I've noticed while doing some research on speakers that the acoustic
suspension design has largely disappeared in favor of bass-reflex design.
Also, the newer speakers (dynamic) are using metals or metal sandwiches
instead of Kevlar or paper. And the woofer surrounds are butyl rubber
instead of foam.
I'd appreciate your take on all of this. Thanks.

In , on
01/05/04
at 11:26 PM, "lynsam" said:

I've noticed while doing some research on speakers that the acoustic
suspension design has largely disappeared in favor of bass-reflex
design.

"Bass-reflex" has become "ported". Ported designs are more efficient.
An acoustic suspension enclosure must eat the backward propagating
wave, the ported design uses it. In the overall scheme of things,
acoustic suspension design was introduced later than Bass-reflex.
Bass-reflex was always tricky to design because the size of the port
was "tuned" by hand. It was cut-and-try, swear a bit, cut-and-try,
swear some more, cut-and-try, ... Now we have some math that eliminates
the cut-and-try tuning. One can purchase a computer program that will
design a passable speaker while you watch.

There are contract engineers who will design a line of speakers for a
fee. It is possible that some of the brands you looked at were designed
by the same person.

Also, the newer speakers (dynamic) are using metals or metal
sandwiches instead of Kevlar or paper.

Depends where you hang out. Many believe that speakers still need lots
of improving. Some think that: Since the regular materials aren't doing
the job, why not try something exotic? I had one speaker sales rep tell
me that his brand used special water to make the paper pulp. To a large
degree, the choice of materials is whatever is in the design engineers
"bag of tricks". Many times the designer comes to this industry because
of a love of audio. If the designer used fiber composits in the
previous career, Kevlar is the likely choice. Another designer might be
more familiar with metal sandwiches. There are a lot of copycats in the
speaker design business.

And the woofer surrounds are
butyl rubber instead of foam.
I'd appreciate your take on all of this. Thanks.

That foam from the 70's has liquefied, the rubber didn't. A new cottage
industry has sprung-up to replace all those old foam surrounds.

-----------------------------------------------------------
spam:
wordgame:123(abc):14 9 20 5 2 9 18 4 at 22 15 9 3 5 14 5 20 dot 3 15
13 (Barry Mann)
[sorry about the puzzle, spammers are ruining my mailbox]
-----------------------------------------------------------

In , on
01/05/04
at 11:26 PM, "lynsam" said:

I've noticed while doing some research on speakers that the acoustic
suspension design has largely disappeared in favor of bass-reflex
design.

"Bass-reflex" has become "ported". Ported designs are more efficient.
An acoustic suspension enclosure must eat the backward propagating
wave, the ported design uses it. In the overall scheme of things,
acoustic suspension design was introduced later than Bass-reflex.
Bass-reflex was always tricky to design because the size of the port
was "tuned" by hand. It was cut-and-try, swear a bit, cut-and-try,
swear some more, cut-and-try, ... Now we have some math that eliminates
the cut-and-try tuning. One can purchase a computer program that will
design a passable speaker while you watch.

There are contract engineers who will design a line of speakers for a
fee. It is possible that some of the brands you looked at were designed
by the same person.

Also, the newer speakers (dynamic) are using metals or metal
sandwiches instead of Kevlar or paper.

Depends where you hang out. Many believe that speakers still need lots
of improving. Some think that: Since the regular materials aren't doing
the job, why not try something exotic? I had one speaker sales rep tell
me that his brand used special water to make the paper pulp. To a large
degree, the choice of materials is whatever is in the design engineers
"bag of tricks". Many times the designer comes to this industry because
of a love of audio. If the designer used fiber composits in the
previous career, Kevlar is the likely choice. Another designer might be
more familiar with metal sandwiches. There are a lot of copycats in the
speaker design business.

And the woofer surrounds are
butyl rubber instead of foam.
I'd appreciate your take on all of this. Thanks.

That foam from the 70's has liquefied, the rubber didn't. A new cottage
industry has sprung-up to replace all those old foam surrounds.

-----------------------------------------------------------
spam:
wordgame:123(abc):14 9 20 5 2 9 18 4 at 22 15 9 3 5 14 5 20 dot 3 15
13 (Barry Mann)
[sorry about the puzzle, spammers are ruining my mailbox]
-----------------------------------------------------------

In , on
01/05/04
at 11:26 PM, "lynsam" said:

I've noticed while doing some research on speakers that the acoustic
suspension design has largely disappeared in favor of bass-reflex
design.

"Bass-reflex" has become "ported". Ported designs are more efficient.
An acoustic suspension enclosure must eat the backward propagating
wave, the ported design uses it. In the overall scheme of things,
acoustic suspension design was introduced later than Bass-reflex.
Bass-reflex was always tricky to design because the size of the port
was "tuned" by hand. It was cut-and-try, swear a bit, cut-and-try,
swear some more, cut-and-try, ... Now we have some math that eliminates
the cut-and-try tuning. One can purchase a computer program that will
design a passable speaker while you watch.

There are contract engineers who will design a line of speakers for a
fee. It is possible that some of the brands you looked at were designed
by the same person.

Also, the newer speakers (dynamic) are using metals or metal
sandwiches instead of Kevlar or paper.

Depends where you hang out. Many believe that speakers still need lots
of improving. Some think that: Since the regular materials aren't doing
the job, why not try something exotic? I had one speaker sales rep tell
me that his brand used special water to make the paper pulp. To a large
degree, the choice of materials is whatever is in the design engineers
"bag of tricks". Many times the designer comes to this industry because
of a love of audio. If the designer used fiber composits in the
previous career, Kevlar is the likely choice. Another designer might be
more familiar with metal sandwiches. There are a lot of copycats in the
speaker design business.

And the woofer surrounds are
butyl rubber instead of foam.
I'd appreciate your take on all of this. Thanks.

That foam from the 70's has liquefied, the rubber didn't. A new cottage
industry has sprung-up to replace all those old foam surrounds.

-----------------------------------------------------------
spam:
wordgame:123(abc):14 9 20 5 2 9 18 4 at 22 15 9 3 5 14 5 20 dot 3 15
13 (Barry Mann)
[sorry about the puzzle, spammers are ruining my mailbox]
-----------------------------------------------------------

lynsam wrote:

I've noticed while doing some research on speakers that the acoustic
suspension design has largely disappeared in favor of bass-reflex design.

After Thiele and Small got the math done it became a lot easier to
design bass-reflex cabinets.

Also, the newer speakers (dynamic) are using metals or metal
sandwiches instead of Kevlar or paper.

Metal is as poor as kevlar unless you are very good at making
cross-overs. If you are very good at making cross-overs then something
that is rigid in the pass band is attractive.

And the woofer surrounds are butyl rubber
instead of foam.

Yes, as it was prior to foam getting intruced and because there are
quite many people who will not ever purchase anything with a foam
surround for some straaange reason.

I'd appreciate your take on all of this. Thanks.

My dkk 0.02 above.

--
*******************************************
* My site is at: http://www.muyiovatki.dk *
*******************************************

lynsam wrote:

I've noticed while doing some research on speakers that the acoustic
suspension design has largely disappeared in favor of bass-reflex design.

After Thiele and Small got the math done it became a lot easier to
design bass-reflex cabinets.

Also, the newer speakers (dynamic) are using metals or metal
sandwiches instead of Kevlar or paper.

Metal is as poor as kevlar unless you are very good at making
cross-overs. If you are very good at making cross-overs then something
that is rigid in the pass band is attractive.

And the woofer surrounds are butyl rubber
instead of foam.

Yes, as it was prior to foam getting intruced and because there are
quite many people who will not ever purchase anything with a foam
surround for some straaange reason.

I'd appreciate your take on all of this. Thanks.

My dkk 0.02 above.

--
*******************************************
* My site is at: http://www.muyiovatki.dk *
*******************************************

lynsam wrote:

I've noticed while doing some research on speakers that the acoustic
suspension design has largely disappeared in favor of bass-reflex design.

After Thiele and Small got the math done it became a lot easier to
design bass-reflex cabinets.

Also, the newer speakers (dynamic) are using metals or metal
sandwiches instead of Kevlar or paper.

Metal is as poor as kevlar unless you are very good at making
cross-overs. If you are very good at making cross-overs then something
that is rigid in the pass band is attractive.

And the woofer surrounds are butyl rubber
instead of foam.

Yes, as it was prior to foam getting intruced and because there are
quite many people who will not ever purchase anything with a foam
surround for some straaange reason.

I'd appreciate your take on all of this. Thanks.

My dkk 0.02 above.

--
*******************************************
* My site is at: http://www.muyiovatki.dk *
*******************************************

(Barry Mann) wrote in message . com...
In , on
01/05/04
at 11:26 PM, "lynsam" said:

I've noticed while doing some research on speakers that the acoustic
suspension design has largely disappeared in favor of bass-reflex
design.

"Bass-reflex" has become "ported". Ported designs are more efficient.
An acoustic suspension enclosure must eat the backward propagating
wave, the ported design uses it.

Not entirely correct.

The common impression is that bass reflex system are more efficient
than sealed box because the sealed enclosure "must eat the backward
wave," implying that a reflex is going to be twice as efficient because
it does not wast the rear wave of the cone. This is simply not the case.

A reflex system CAN be more efficient that a sealed system of the same
box volume and cutoff frequency becuase it can utilize a more efficient
driver to achieve those results. So the system is more efficient because
the DRIVER is more efficient, not becuas ethe ENCLOSURE is more efficient.
The reason this is so is not as straightforward as "using the back wave."

The efficiency of ANY direct-radiator system (bass reflex, ported, vented,
sealed, acoustic suspension, infinite baffle) is determined by the driver.
The driver's electrical resistance, its moving mass, its radiating area
and its magnet system determine that efficiency, period. The enclosure,
in combination with the driver, determines the system response function
near the low end cutoff.

Now, if we want to build an acoustic suspension system which maximizes
the efficiency/volume/bandwidth relation, i.e., makes the efficiency
as high as possible, the enclosure volume as small as possible and
the cutoff frequency as low as possible, we need to pick a driver that
has a certain combination of mass, resistance, magnet and so on that
in that enclosure, gives a slightly underdamped response. That combination
of mass, resistance, magnet, and so on leads to a particular system
efficiency. Your stuck with it, if that's the system performance you
want.

Now, if you put a MORE efficient driver in that same sealed box, say
with a larger magnet or lower resistance, the system response will now
be UNDERdamped (because damping increases with increasing magnet strength
or lowered DC resistance) and, as a result, have a HIGHER cutoff frequency
than the sealed box system, BUT will also have a higher efficiency as well.

Now, punch a hole in the enclosure of the right size, and what you have
now done is NOT made the system more efficient (you already got ALL of
your efficiency increase from the driver), but you have now utilized the
enclosure air compliance and the acoustical inertance of the port to add
a second resonant system to our speaker system (the first being the driver
mass and combination of driver and enclosure compliance). That second
resonant system has the property of essentially taking over (that is,
replacing) the output of the main driver and for a reagion right around
the cutoff frequency, providing most of the output of the system

Imagine it this way, the more efficient driver rolls off in the bass
early, but the port supplants the output where the driver output is
drooping resulting in a flat, but slightly extended low end. Which,
if you pick that partifcular combination of parameters, results in
the same cutoff frequency in the same box but with the possibility of
up to twice the efficiency.

Punching a hole in a box DOES NOT make the speaker more efficient.
Putting a more efficient speaker in the box is what makes it more
efficient, and punching the hole is what makes the low end response
go to where you want it to in that sized enclosure.

In the overall scheme of things,
acoustic suspension design was introduced later than Bass-reflex.
Bass-reflex was always tricky to design because the size of the port
was "tuned" by hand. It was cut-and-try, swear a bit, cut-and-try,
swear some more, cut-and-try, ... Now we have some math that eliminates
the cut-and-try tuning. One can purchase a computer program that will
design a passable speaker while you watch.

Actually, we don't have "some math," we have a comprehensive system
model which works very well. And, interestingly enoughm, that model
was well in place cotemporaneously with the acoustic suspension
speaker, Thiele having done his work in the early 1960's. It just took
a long time for people, especially in the U.S., to recognize it for
what it was. The more recent proliferation of software that makes the
"design" of such systems accessible has, regrettably, done little to
promote the understanding of WHY things work the way they do.

To more directly address the original question, much of the impetous
for the change in what's available is more market-driven than
technically correct. Ports are stuck in boom-box and computer
speakers because they look cool, not because they are correct.

On the other hand, the combination of proper driver and enclosure
parameters is yet another set of tools to a competent designer to
enable the realization of a final system response.

And the woofer surrounds are
butyl rubber instead of foam.
I'd appreciate your take on all of this. Thanks.

That foam from the 70's has liquefied, the rubber didn't. A new cottage
industry has sprung-up to replace all those old foam surrounds.

Beyond that, foam surrounds are very cheap to tool up for and
manufacture. It's a pretty low-tech process requiring low-pressure,
high-tolerance heated molds and not particularily accurate trim
dies. There are basically nothing more than thicker (5-10 mm)
sheets of very ordinary polyurethane foam that are compressed
under moderate temperatures (80-100C) in a simple press. The
resulting product is, well, cheap. Foam surrounds tend to have
less than optimum internal mechanical losses necessary for proper
termination of cones. Depending upon the forumlation of the polyurethane,
these surrounds can be VERY vulnerable to both atmospheric chemical,
ultraviolet and biological deterioration. Having learned this fact
in the middle 1980's, the speaker industry promptly forgot it.

(Barry Mann) wrote in message . com...
In , on
01/05/04
at 11:26 PM, "lynsam" said:

I've noticed while doing some research on speakers that the acoustic
suspension design has largely disappeared in favor of bass-reflex
design.

"Bass-reflex" has become "ported". Ported designs are more efficient.
An acoustic suspension enclosure must eat the backward propagating
wave, the ported design uses it.

Not entirely correct.

The common impression is that bass reflex system are more efficient
than sealed box because the sealed enclosure "must eat the backward
wave," implying that a reflex is going to be twice as efficient because
it does not wast the rear wave of the cone. This is simply not the case.

A reflex system CAN be more efficient that a sealed system of the same
box volume and cutoff frequency becuase it can utilize a more efficient
driver to achieve those results. So the system is more efficient because
the DRIVER is more efficient, not becuas ethe ENCLOSURE is more efficient.
The reason this is so is not as straightforward as "using the back wave."

The efficiency of ANY direct-radiator system (bass reflex, ported, vented,
sealed, acoustic suspension, infinite baffle) is determined by the driver.
The driver's electrical resistance, its moving mass, its radiating area
and its magnet system determine that efficiency, period. The enclosure,
in combination with the driver, determines the system response function
near the low end cutoff.

Now, if we want to build an acoustic suspension system which maximizes
the efficiency/volume/bandwidth relation, i.e., makes the efficiency
as high as possible, the enclosure volume as small as possible and
the cutoff frequency as low as possible, we need to pick a driver that
has a certain combination of mass, resistance, magnet and so on that
in that enclosure, gives a slightly underdamped response. That combination
of mass, resistance, magnet, and so on leads to a particular system
efficiency. Your stuck with it, if that's the system performance you
want.

Now, if you put a MORE efficient driver in that same sealed box, say
with a larger magnet or lower resistance, the system response will now
be UNDERdamped (because damping increases with increasing magnet strength
or lowered DC resistance) and, as a result, have a HIGHER cutoff frequency
than the sealed box system, BUT will also have a higher efficiency as well.

Now, punch a hole in the enclosure of the right size, and what you have
now done is NOT made the system more efficient (you already got ALL of
your efficiency increase from the driver), but you have now utilized the
enclosure air compliance and the acoustical inertance of the port to add
a second resonant system to our speaker system (the first being the driver
mass and combination of driver and enclosure compliance). That second
resonant system has the property of essentially taking over (that is,
replacing) the output of the main driver and for a reagion right around
the cutoff frequency, providing most of the output of the system

Imagine it this way, the more efficient driver rolls off in the bass
early, but the port supplants the output where the driver output is
drooping resulting in a flat, but slightly extended low end. Which,
if you pick that partifcular combination of parameters, results in
the same cutoff frequency in the same box but with the possibility of
up to twice the efficiency.

Punching a hole in a box DOES NOT make the speaker more efficient.
Putting a more efficient speaker in the box is what makes it more
efficient, and punching the hole is what makes the low end response
go to where you want it to in that sized enclosure.

In the overall scheme of things,
acoustic suspension design was introduced later than Bass-reflex.
Bass-reflex was always tricky to design because the size of the port
was "tuned" by hand. It was cut-and-try, swear a bit, cut-and-try,
swear some more, cut-and-try, ... Now we have some math that eliminates
the cut-and-try tuning. One can purchase a computer program that will
design a passable speaker while you watch.

Actually, we don't have "some math," we have a comprehensive system
model which works very well. And, interestingly enoughm, that model
was well in place cotemporaneously with the acoustic suspension
speaker, Thiele having done his work in the early 1960's. It just took
a long time for people, especially in the U.S., to recognize it for
what it was. The more recent proliferation of software that makes the
"design" of such systems accessible has, regrettably, done little to
promote the understanding of WHY things work the way they do.

To more directly address the original question, much of the impetous
for the change in what's available is more market-driven than
technically correct. Ports are stuck in boom-box and computer
speakers because they look cool, not because they are correct.

On the other hand, the combination of proper driver and enclosure
parameters is yet another set of tools to a competent designer to
enable the realization of a final system response.

And the woofer surrounds are
butyl rubber instead of foam.
I'd appreciate your take on all of this. Thanks.

That foam from the 70's has liquefied, the rubber didn't. A new cottage
industry has sprung-up to replace all those old foam surrounds.

Beyond that, foam surrounds are very cheap to tool up for and
manufacture. It's a pretty low-tech process requiring low-pressure,
high-tolerance heated molds and not particularily accurate trim
dies. There are basically nothing more than thicker (5-10 mm)
sheets of very ordinary polyurethane foam that are compressed
under moderate temperatures (80-100C) in a simple press. The
resulting product is, well, cheap. Foam surrounds tend to have
less than optimum internal mechanical losses necessary for proper
termination of cones. Depending upon the forumlation of the polyurethane,
these surrounds can be VERY vulnerable to both atmospheric chemical,
ultraviolet and biological deterioration. Having learned this fact
in the middle 1980's, the speaker industry promptly forgot it.

(Barry Mann) wrote in message . com...
In , on
01/05/04
at 11:26 PM, "lynsam" said:

I've noticed while doing some research on speakers that the acoustic
suspension design has largely disappeared in favor of bass-reflex
design.

"Bass-reflex" has become "ported". Ported designs are more efficient.
An acoustic suspension enclosure must eat the backward propagating
wave, the ported design uses it.

Not entirely correct.

The common impression is that bass reflex system are more efficient
than sealed box because the sealed enclosure "must eat the backward
wave," implying that a reflex is going to be twice as efficient because
it does not wast the rear wave of the cone. This is simply not the case.

A reflex system CAN be more efficient that a sealed system of the same
box volume and cutoff frequency becuase it can utilize a more efficient
driver to achieve those results. So the system is more efficient because
the DRIVER is more efficient, not becuas ethe ENCLOSURE is more efficient.
The reason this is so is not as straightforward as "using the back wave."

The efficiency of ANY direct-radiator system (bass reflex, ported, vented,
sealed, acoustic suspension, infinite baffle) is determined by the driver.
The driver's electrical resistance, its moving mass, its radiating area
and its magnet system determine that efficiency, period. The enclosure,
in combination with the driver, determines the system response function
near the low end cutoff.

Now, if we want to build an acoustic suspension system which maximizes
the efficiency/volume/bandwidth relation, i.e., makes the efficiency
as high as possible, the enclosure volume as small as possible and
the cutoff frequency as low as possible, we need to pick a driver that
has a certain combination of mass, resistance, magnet and so on that
in that enclosure, gives a slightly underdamped response. That combination
of mass, resistance, magnet, and so on leads to a particular system
efficiency. Your stuck with it, if that's the system performance you
want.

Now, if you put a MORE efficient driver in that same sealed box, say
with a larger magnet or lower resistance, the system response will now
be UNDERdamped (because damping increases with increasing magnet strength
or lowered DC resistance) and, as a result, have a HIGHER cutoff frequency
than the sealed box system, BUT will also have a higher efficiency as well.

Now, punch a hole in the enclosure of the right size, and what you have
now done is NOT made the system more efficient (you already got ALL of
your efficiency increase from the driver), but you have now utilized the
enclosure air compliance and the acoustical inertance of the port to add
a second resonant system to our speaker system (the first being the driver
mass and combination of driver and enclosure compliance). That second
resonant system has the property of essentially taking over (that is,
replacing) the output of the main driver and for a reagion right around
the cutoff frequency, providing most of the output of the system

Imagine it this way, the more efficient driver rolls off in the bass
early, but the port supplants the output where the driver output is
drooping resulting in a flat, but slightly extended low end. Which,
if you pick that partifcular combination of parameters, results in
the same cutoff frequency in the same box but with the possibility of
up to twice the efficiency.

Punching a hole in a box DOES NOT make the speaker more efficient.
Putting a more efficient speaker in the box is what makes it more
efficient, and punching the hole is what makes the low end response
go to where you want it to in that sized enclosure.

In the overall scheme of things,
acoustic suspension design was introduced later than Bass-reflex.
Bass-reflex was always tricky to design because the size of the port
was "tuned" by hand. It was cut-and-try, swear a bit, cut-and-try,
swear some more, cut-and-try, ... Now we have some math that eliminates
the cut-and-try tuning. One can purchase a computer program that will
design a passable speaker while you watch.

Actually, we don't have "some math," we have a comprehensive system
model which works very well. And, interestingly enoughm, that model
was well in place cotemporaneously with the acoustic suspension
speaker, Thiele having done his work in the early 1960's. It just took
a long time for people, especially in the U.S., to recognize it for
what it was. The more recent proliferation of software that makes the
"design" of such systems accessible has, regrettably, done little to
promote the understanding of WHY things work the way they do.

To more directly address the original question, much of the impetous
for the change in what's available is more market-driven than
technically correct. Ports are stuck in boom-box and computer
speakers because they look cool, not because they are correct.

On the other hand, the combination of proper driver and enclosure
parameters is yet another set of tools to a competent designer to
enable the realization of a final system response.

And the woofer surrounds are
butyl rubber instead of foam.
I'd appreciate your take on all of this. Thanks.

That foam from the 70's has liquefied, the rubber didn't. A new cottage
industry has sprung-up to replace all those old foam surrounds.

Beyond that, foam surrounds are very cheap to tool up for and
manufacture. It's a pretty low-tech process requiring low-pressure,
high-tolerance heated molds and not particularily accurate trim
dies. There are basically nothing more than thicker (5-10 mm)
sheets of very ordinary polyurethane foam that are compressed
under moderate temperatures (80-100C) in a simple press. The
resulting product is, well, cheap. Foam surrounds tend to have
less than optimum internal mechanical losses necessary for proper
termination of cones. Depending upon the forumlation of the polyurethane,
these surrounds can be VERY vulnerable to both atmospheric chemical,
ultraviolet and biological deterioration. Having learned this fact
in the middle 1980's, the speaker industry promptly forgot it.

On Tue, 06 Jan 2004 13:18:10 +0100, Peter Larsen
wrote:

Metal is as poor as kevlar unless you are very good at making
cross-overs. If you are very good at making cross-overs then something
that is rigid in the pass band is attractive.

The B&W Kevlar drivers are not rigid in the pass band, they are
*designed* to move into bending mode.
--

Stewart Pinkerton | Music is Art - Audio is Engineering

On Tue, 06 Jan 2004 13:18:10 +0100, Peter Larsen
wrote:

Metal is as poor as kevlar unless you are very good at making
cross-overs. If you are very good at making cross-overs then something
that is rigid in the pass band is attractive.

The B&W Kevlar drivers are not rigid in the pass band, they are
*designed* to move into bending mode.
--

Stewart Pinkerton | Music is Art - Audio is Engineering

On Tue, 06 Jan 2004 13:18:10 +0100, Peter Larsen
wrote:

Metal is as poor as kevlar unless you are very good at making
cross-overs. If you are very good at making cross-overs then something
that is rigid in the pass band is attractive.

The B&W Kevlar drivers are not rigid in the pass band, they are
*designed* to move into bending mode.
--

Stewart Pinkerton | Music is Art - Audio is Engineering

Stewart Pinkerton wrote:

On Tue, 06 Jan 2004 13:18:10 +0100, Peter Larsen
wrote:

Metal is as poor as kevlar unless you are very good at making
cross-overs. If you are very good at making cross-overs then something
that is rigid in the pass band is attractive.

The B&W Kevlar drivers are not rigid in the pass band, they are
*designed* to move into bending mode.

Yes, yes, yes, kevlar units (x) tend to have a nice smooth drastically
rising response because of that well designed breakup, but eventually
things do get to steep dips, the major issue is of course the rising
response, they are possibly not heavy enough to remain linear when
breaking up ... it would be great if somebody could explain this better.

(x) those I have seen specs for, I recall - probably Seas - mentioning
that they required special care in the cross-over ... the Monacor ones
surely are not "exceptionally flat" by any definition of that term.
Flatness of response is however a system requirement and not a unit
requirement.

Stewart Pinkerton | Music is Art - Audio is Engineering


Kind regards

Peter Larsen

--
*******************************************
* My site is at: http://www.muyiovatki.dk *
*******************************************

Stewart Pinkerton wrote:

On Tue, 06 Jan 2004 13:18:10 +0100, Peter Larsen
wrote:

Metal is as poor as kevlar unless you are very good at making
cross-overs. If you are very good at making cross-overs then something
that is rigid in the pass band is attractive.

The B&W Kevlar drivers are not rigid in the pass band, they are
*designed* to move into bending mode.

Yes, yes, yes, kevlar units (x) tend to have a nice smooth drastically
rising response because of that well designed breakup, but eventually
things do get to steep dips, the major issue is of course the rising
response, they are possibly not heavy enough to remain linear when
breaking up ... it would be great if somebody could explain this better.

(x) those I have seen specs for, I recall - probably Seas - mentioning
that they required special care in the cross-over ... the Monacor ones
surely are not "exceptionally flat" by any definition of that term.
Flatness of response is however a system requirement and not a unit
requirement.

Stewart Pinkerton | Music is Art - Audio is Engineering


Kind regards

Peter Larsen

--
*******************************************
* My site is at: http://www.muyiovatki.dk *
*******************************************

Stewart Pinkerton wrote:

On Tue, 06 Jan 2004 13:18:10 +0100, Peter Larsen
wrote:

Metal is as poor as kevlar unless you are very good at making
cross-overs. If you are very good at making cross-overs then something
that is rigid in the pass band is attractive.

The B&W Kevlar drivers are not rigid in the pass band, they are
*designed* to move into bending mode.

Yes, yes, yes, kevlar units (x) tend to have a nice smooth drastically
rising response because of that well designed breakup, but eventually
things do get to steep dips, the major issue is of course the rising
response, they are possibly not heavy enough to remain linear when
breaking up ... it would be great if somebody could explain this better.

(x) those I have seen specs for, I recall - probably Seas - mentioning
that they required special care in the cross-over ... the Monacor ones
surely are not "exceptionally flat" by any definition of that term.
Flatness of response is however a system requirement and not a unit
requirement.

Stewart Pinkerton | Music is Art - Audio is Engineering


Kind regards

Peter Larsen

--
*******************************************
* My site is at: http://www.muyiovatki.dk *
*******************************************

(Dick Pierce) wrote in message

The efficiency of ANY direct-radiator system (bass reflex, ported, vented,
sealed, acoustic suspension, infinite baffle) is determined by the driver.
The driver's electrical resistance, its moving mass, its radiating area
and its magnet system determine that efficiency, period. The enclosure,
in combination with the driver, determines the system response function
near the low end cutoff.

I agree to your post, except for one little word; the "period" above.
The efficiency is also affected by the placement of the speaker. It is
doubled if it is mounted in a wall, compared to radiating in free
space. Efficiency increases even more if mounted in a corner etc. OK,
OK, I'm being picky and maybe that has nothing to do with the design
of the speaker. ...or maybe it does? If the speaker is designed for
free-field conditions, the speaker will still be radiating in
half-space toward higher frequencies, and thus have a lift of +6dB.
This should be compensated for. If the same speaker is mounted in the
wall, the HF boost will not occur (or rather, an equally large LF
boost will occur), so then no compensation is needed. So, the
placement of the speaker is something that the designer of the system
should consider.

Anyway, efficiency for loudspeaker elements is mostly measured with
the speaker radiating in half-space. Typically, we also mean at a
frequency where the radiation is dominated by the radiation from the
speaker (not the port) and where it is mass-controlled but below
frewquencies where the cone breaks up. Being mass-controlled means
that the mechanical impedance is dominated by the cone and coil
masses, and that the acoustic impedance from the box is neglectable.
Therefore, the efficiency is determined by the driver, as you wrote,
and its placement in the room, but not by the box.

However, strictly speaking, the efficiency varies a lot with
frequency. When the motion is NOT mass-controlled, the situation is
completely different. For example, the efficiency for the closed box
peaks at the system resonance, but since the electrical impedance also
does, less power is delivered to the speaker (for a given voltage) and
the output is largely the same as for higher frequencies (-3dB for a
butterworth design). Well below the resonance it drops by 12
dB/octave. But hardly anyone speaks about efficiency as being varying
with frequency, "it is one number, period". In my opinion this adds to
the confusion regarding efficiency.

The related term "sensitivity" is also often expressed as one number,
as if it did not vary with frequency. However, a frequency response
curve show us exactly how sensitivity varies with frequency (if
calibrated, the sensitivity levels can be read directly on the
y-axis). The frequency response curve is exactly that, a graph that
shows how sensitivity varies with frequency.

BTW is there a difference between "ported", "bass-reflex" and
"vented"? "Sealed" and "acoustic suspension"? Aren't they synonyms?

(Dick Pierce) wrote in message

The efficiency of ANY direct-radiator system (bass reflex, ported, vented,
sealed, acoustic suspension, infinite baffle) is determined by the driver.
The driver's electrical resistance, its moving mass, its radiating area
and its magnet system determine that efficiency, period. The enclosure,
in combination with the driver, determines the system response function
near the low end cutoff.

I agree to your post, except for one little word; the "period" above.
The efficiency is also affected by the placement of the speaker. It is
doubled if it is mounted in a wall, compared to radiating in free
space. Efficiency increases even more if mounted in a corner etc. OK,
OK, I'm being picky and maybe that has nothing to do with the design
of the speaker. ...or maybe it does? If the speaker is designed for
free-field conditions, the speaker will still be radiating in
half-space toward higher frequencies, and thus have a lift of +6dB.
This should be compensated for. If the same speaker is mounted in the
wall, the HF boost will not occur (or rather, an equally large LF
boost will occur), so then no compensation is needed. So, the
placement of the speaker is something that the designer of the system
should consider.

Anyway, efficiency for loudspeaker elements is mostly measured with
the speaker radiating in half-space. Typically, we also mean at a
frequency where the radiation is dominated by the radiation from the
speaker (not the port) and where it is mass-controlled but below
frewquencies where the cone breaks up. Being mass-controlled means
that the mechanical impedance is dominated by the cone and coil
masses, and that the acoustic impedance from the box is neglectable.
Therefore, the efficiency is determined by the driver, as you wrote,
and its placement in the room, but not by the box.

However, strictly speaking, the efficiency varies a lot with
frequency. When the motion is NOT mass-controlled, the situation is
completely different. For example, the efficiency for the closed box
peaks at the system resonance, but since the electrical impedance also
does, less power is delivered to the speaker (for a given voltage) and
the output is largely the same as for higher frequencies (-3dB for a
butterworth design). Well below the resonance it drops by 12
dB/octave. But hardly anyone speaks about efficiency as being varying
with frequency, "it is one number, period". In my opinion this adds to
the confusion regarding efficiency.

The related term "sensitivity" is also often expressed as one number,
as if it did not vary with frequency. However, a frequency response
curve show us exactly how sensitivity varies with frequency (if
calibrated, the sensitivity levels can be read directly on the
y-axis). The frequency response curve is exactly that, a graph that
shows how sensitivity varies with frequency.

BTW is there a difference between "ported", "bass-reflex" and
"vented"? "Sealed" and "acoustic suspension"? Aren't they synonyms?

(Dick Pierce) wrote in message

The efficiency of ANY direct-radiator system (bass reflex, ported, vented,
sealed, acoustic suspension, infinite baffle) is determined by the driver.
The driver's electrical resistance, its moving mass, its radiating area
and its magnet system determine that efficiency, period. The enclosure,
in combination with the driver, determines the system response function
near the low end cutoff.

I agree to your post, except for one little word; the "period" above.
The efficiency is also affected by the placement of the speaker. It is
doubled if it is mounted in a wall, compared to radiating in free
space. Efficiency increases even more if mounted in a corner etc. OK,
OK, I'm being picky and maybe that has nothing to do with the design
of the speaker. ...or maybe it does? If the speaker is designed for
free-field conditions, the speaker will still be radiating in
half-space toward higher frequencies, and thus have a lift of +6dB.
This should be compensated for. If the same speaker is mounted in the
wall, the HF boost will not occur (or rather, an equally large LF
boost will occur), so then no compensation is needed. So, the
placement of the speaker is something that the designer of the system
should consider.

Anyway, efficiency for loudspeaker elements is mostly measured with
the speaker radiating in half-space. Typically, we also mean at a
frequency where the radiation is dominated by the radiation from the
speaker (not the port) and where it is mass-controlled but below
frewquencies where the cone breaks up. Being mass-controlled means
that the mechanical impedance is dominated by the cone and coil
masses, and that the acoustic impedance from the box is neglectable.
Therefore, the efficiency is determined by the driver, as you wrote,
and its placement in the room, but not by the box.

However, strictly speaking, the efficiency varies a lot with
frequency. When the motion is NOT mass-controlled, the situation is
completely different. For example, the efficiency for the closed box
peaks at the system resonance, but since the electrical impedance also
does, less power is delivered to the speaker (for a given voltage) and
the output is largely the same as for higher frequencies (-3dB for a
butterworth design). Well below the resonance it drops by 12
dB/octave. But hardly anyone speaks about efficiency as being varying
with frequency, "it is one number, period". In my opinion this adds to
the confusion regarding efficiency.

The related term "sensitivity" is also often expressed as one number,
as if it did not vary with frequency. However, a frequency response
curve show us exactly how sensitivity varies with frequency (if
calibrated, the sensitivity levels can be read directly on the
y-axis). The frequency response curve is exactly that, a graph that
shows how sensitivity varies with frequency.

BTW is there a difference between "ported", "bass-reflex" and
"vented"? "Sealed" and "acoustic suspension"? Aren't they synonyms?

(Dick Pierce) wrote in message

The efficiency of ANY direct-radiator system (bass reflex, ported, vented,
sealed, acoustic suspension, infinite baffle) is determined by the driver.
The driver's electrical resistance, its moving mass, its radiating area
and its magnet system determine that efficiency, period. The enclosure,
in combination with the driver, determines the system response function
near the low end cutoff.

I agree to your post, except for one little word; the "period" above.
The efficiency is also affected by the placement of the speaker. It is
doubled if it is mounted in a wall, compared to radiating in free
space. Efficiency increases even more if mounted in a corner etc. OK,
OK, I'm being picky and maybe that has nothing to do with the design
of the speaker. ...or maybe it does? If the speaker is designed for
free-field conditions, the speaker will still be radiating in
half-space toward higher frequencies, and thus have a lift of +6dB.
This should be compensated for. If the same speaker is mounted in the
wall, the HF boost will not occur (or rather, an equally large LF
boost will occur), so then no compensation is needed. So, the
placement of the speaker is something that the designer of the system
should consider.

Anyway, efficiency for loudspeaker elements is mostly measured with
the speaker radiating in half-space. Typically, we also mean at a
frequency where the radiation is dominated by the radiation from the
speaker (not the port) and where it is mass-controlled but below
frewquencies where the cone breaks up. Being mass-controlled means
that the mechanical impedance is dominated by the cone and coil
masses, and that the acoustic impedance from the box is neglectable.
Therefore, the efficiency is determined by the driver, as you wrote,
and its placement in the room, but not by the box.

However, strictly speaking, the efficiency varies a lot with
frequency. When the motion is NOT mass-controlled, the situation is
completely different. For example, the efficiency for the closed box
peaks at the system resonance, but since the electrical impedance also
does, less power is delivered to the speaker (for a given voltage) and
the output is largely the same as for higher frequencies (-3dB for a
butterworth design). Well below the resonance it drops by 12
dB/octave. But hardly anyone speaks about efficiency as being varying
with frequency, "it is one number, period". In my opinion this adds to
the confusion regarding efficiency.

The related term "sensitivity" is also often expressed as one number,
as if it did not vary with frequency. However, a frequency response
curve show us exactly how sensitivity varies with frequency (if
calibrated, the sensitivity levels can be read directly on the
y-axis). The frequency response curve is exactly that, a graph that
shows how sensitivity varies with frequency.

BTW is there a difference between "ported", "bass-reflex" and
"vented"? "Sealed" and "acoustic suspension"? Aren't they synonyms?

(Svante) wrote in message om...
(Dick Pierce) wrote in message

The efficiency of ANY direct-radiator system (bass reflex, ported, vented,
sealed, acoustic suspension, infinite baffle) is determined by the driver.
The driver's electrical resistance, its moving mass, its radiating area
and its magnet system determine that efficiency, period. The enclosure,
in combination with the driver, determines the system response function
near the low end cutoff.

I agree to your post, except for one little word; the "period" above.
The efficiency is also affected by the placement of the speaker. It is
doubled if it is mounted in a wall, compared to radiating in free
space. Efficiency increases even more if mounted in a corner etc. OK,
OK, I'm being picky and maybe that has nothing to do with the design
of the speaker. ...or maybe it does? If the speaker is designed for
free-field conditions, the speaker will still be radiating in
half-space toward higher frequencies, and thus have a lift of +6dB.
This should be compensated for. If the same speaker is mounted in the
wall, the HF boost will not occur (or rather, an equally large LF
boost will occur), so then no compensation is needed. So, the
placement of the speaker is something that the designer of the system
should consider.

Actually, no, the efficiency, specifically, the ratio of total
radiated acoustic power to total input electrical power does NOT
change. The sound pressure level on axis MAY change, but the
efficiency does not. The same power is distributed over a smaller
area, and since SPL is a measure of power per unit area, the SPL
changes, but the power output does not.

However, strictly speaking, the efficiency varies a lot with
frequency. When the motion is NOT mass-controlled, the situation is
completely different.

There is a specific definition for efficiency, which is very clear
on the meaning, that is, the efficiency above the system cutoff
but below the frequency where the wavelength is equal to the
circumference of the radiator. SMall and Thiele and others are quite
clear on this definition, and I defer to their definition.

For example, the efficiency for the closed box
peaks at the system resonance, but since the electrical impedance also
does, less power is delivered to the speaker (for a given voltage) and
the output is largely the same as for higher frequencies (-3dB for a
butterworth design). Well below the resonance it drops by 12
dB/octave. But hardly anyone speaks about efficiency as being varying
with frequency, "it is one number, period". In my opinion this adds to
the confusion regarding efficiency.

As the definition used in the domain is quite clear, no, it in
fact removes such confusion.

BTW is there a difference between "ported", "bass-reflex" and
"vented"?

Generally, these terms are synonymous.

"Sealed" and "acoustic suspension"? Aren't they synonyms?

No, indeed, they are not. While an acoustic suspension enclosure
is a sealed enclosure, the converse is not necessarily true.

A "sealed" enclosure can be defined broadly a number of ways, but
generally refers to any enclosure where the time constant of any
"leak" is MUCH longer than the time constant of the system cutoff
frequency. Also, any such leak cannot contrinute at all to the total
system output. Essentially, the enclosed air looks like a simple
acoustical compliance.

An "acoustic suspension" is defined as a subset of sealed box systems
where the acoustical compliance of the enclosure is substantially
smaller than the compliance of the driver suspension, and thus it
is the enclosure compliance that cominates the total system compliance.
Typically, this means that the enclosure volume is NO MORE than 1/4
the equivalent volume of compliance of the driver, specifically:

Vb = Vas / 4

In such an arrangement, the enclosure provides the major portion of
the system stuffness seen by the driver, and the amount of stiffness
provided by the suspension is relatively insignificant by comparison.

(Svante) wrote in message om...
(Dick Pierce) wrote in message

The efficiency of ANY direct-radiator system (bass reflex, ported, vented,
sealed, acoustic suspension, infinite baffle) is determined by the driver.
The driver's electrical resistance, its moving mass, its radiating area
and its magnet system determine that efficiency, period. The enclosure,
in combination with the driver, determines the system response function
near the low end cutoff.

I agree to your post, except for one little word; the "period" above.
The efficiency is also affected by the placement of the speaker. It is
doubled if it is mounted in a wall, compared to radiating in free
space. Efficiency increases even more if mounted in a corner etc. OK,
OK, I'm being picky and maybe that has nothing to do with the design
of the speaker. ...or maybe it does? If the speaker is designed for
free-field conditions, the speaker will still be radiating in
half-space toward higher frequencies, and thus have a lift of +6dB.
This should be compensated for. If the same speaker is mounted in the
wall, the HF boost will not occur (or rather, an equally large LF
boost will occur), so then no compensation is needed. So, the
placement of the speaker is something that the designer of the system
should consider.

Actually, no, the efficiency, specifically, the ratio of total
radiated acoustic power to total input electrical power does NOT
change. The sound pressure level on axis MAY change, but the
efficiency does not. The same power is distributed over a smaller
area, and since SPL is a measure of power per unit area, the SPL
changes, but the power output does not.

However, strictly speaking, the efficiency varies a lot with
frequency. When the motion is NOT mass-controlled, the situation is
completely different.

There is a specific definition for efficiency, which is very clear
on the meaning, that is, the efficiency above the system cutoff
but below the frequency where the wavelength is equal to the
circumference of the radiator. SMall and Thiele and others are quite
clear on this definition, and I defer to their definition.

For example, the efficiency for the closed box
peaks at the system resonance, but since the electrical impedance also
does, less power is delivered to the speaker (for a given voltage) and
the output is largely the same as for higher frequencies (-3dB for a
butterworth design). Well below the resonance it drops by 12
dB/octave. But hardly anyone speaks about efficiency as being varying
with frequency, "it is one number, period". In my opinion this adds to
the confusion regarding efficiency.

As the definition used in the domain is quite clear, no, it in
fact removes such confusion.

BTW is there a difference between "ported", "bass-reflex" and
"vented"?

Generally, these terms are synonymous.

"Sealed" and "acoustic suspension"? Aren't they synonyms?

No, indeed, they are not. While an acoustic suspension enclosure
is a sealed enclosure, the converse is not necessarily true.

A "sealed" enclosure can be defined broadly a number of ways, but
generally refers to any enclosure where the time constant of any
"leak" is MUCH longer than the time constant of the system cutoff
frequency. Also, any such leak cannot contrinute at all to the total
system output. Essentially, the enclosed air looks like a simple
acoustical compliance.

An "acoustic suspension" is defined as a subset of sealed box systems
where the acoustical compliance of the enclosure is substantially
smaller than the compliance of the driver suspension, and thus it
is the enclosure compliance that cominates the total system compliance.
Typically, this means that the enclosure volume is NO MORE than 1/4
the equivalent volume of compliance of the driver, specifically:

Vb = Vas / 4

In such an arrangement, the enclosure provides the major portion of
the system stuffness seen by the driver, and the amount of stiffness
provided by the suspension is relatively insignificant by comparison.

(Svante) wrote in message om...
(Dick Pierce) wrote in message

The efficiency of ANY direct-radiator system (bass reflex, ported, vented,
sealed, acoustic suspension, infinite baffle) is determined by the driver.
The driver's electrical resistance, its moving mass, its radiating area
and its magnet system determine that efficiency, period. The enclosure,
in combination with the driver, determines the system response function
near the low end cutoff.

I agree to your post, except for one little word; the "period" above.
The efficiency is also affected by the placement of the speaker. It is
doubled if it is mounted in a wall, compared to radiating in free
space. Efficiency increases even more if mounted in a corner etc. OK,
OK, I'm being picky and maybe that has nothing to do with the design
of the speaker. ...or maybe it does? If the speaker is designed for
free-field conditions, the speaker will still be radiating in
half-space toward higher frequencies, and thus have a lift of +6dB.
This should be compensated for. If the same speaker is mounted in the
wall, the HF boost will not occur (or rather, an equally large LF
boost will occur), so then no compensation is needed. So, the
placement of the speaker is something that the designer of the system
should consider.

Actually, no, the efficiency, specifically, the ratio of total
radiated acoustic power to total input electrical power does NOT
change. The sound pressure level on axis MAY change, but the
efficiency does not. The same power is distributed over a smaller
area, and since SPL is a measure of power per unit area, the SPL
changes, but the power output does not.

However, strictly speaking, the efficiency varies a lot with
frequency. When the motion is NOT mass-controlled, the situation is
completely different.

There is a specific definition for efficiency, which is very clear
on the meaning, that is, the efficiency above the system cutoff
but below the frequency where the wavelength is equal to the
circumference of the radiator. SMall and Thiele and others are quite
clear on this definition, and I defer to their definition.

For example, the efficiency for the closed box
peaks at the system resonance, but since the electrical impedance also
does, less power is delivered to the speaker (for a given voltage) and
the output is largely the same as for higher frequencies (-3dB for a
butterworth design). Well below the resonance it drops by 12
dB/octave. But hardly anyone speaks about efficiency as being varying
with frequency, "it is one number, period". In my opinion this adds to
the confusion regarding efficiency.

As the definition used in the domain is quite clear, no, it in
fact removes such confusion.

BTW is there a difference between "ported", "bass-reflex" and
"vented"?

Generally, these terms are synonymous.

"Sealed" and "acoustic suspension"? Aren't they synonyms?

No, indeed, they are not. While an acoustic suspension enclosure
is a sealed enclosure, the converse is not necessarily true.

A "sealed" enclosure can be defined broadly a number of ways, but
generally refers to any enclosure where the time constant of any
"leak" is MUCH longer than the time constant of the system cutoff
frequency. Also, any such leak cannot contrinute at all to the total
system output. Essentially, the enclosed air looks like a simple
acoustical compliance.

An "acoustic suspension" is defined as a subset of sealed box systems
where the acoustical compliance of the enclosure is substantially
smaller than the compliance of the driver suspension, and thus it
is the enclosure compliance that cominates the total system compliance.
Typically, this means that the enclosure volume is NO MORE than 1/4
the equivalent volume of compliance of the driver, specifically:

Vb = Vas / 4

In such an arrangement, the enclosure provides the major portion of
the system stuffness seen by the driver, and the amount of stiffness
provided by the suspension is relatively insignificant by comparison.

(Svante) wrote in message om...
(Dick Pierce) wrote in message

The efficiency of ANY direct-radiator system (bass reflex, ported, vented,
sealed, acoustic suspension, infinite baffle) is determined by the driver.
The driver's electrical resistance, its moving mass, its radiating area
and its magnet system determine that efficiency, period. The enclosure,
in combination with the driver, determines the system response function
near the low end cutoff.

I agree to your post, except for one little word; the "period" above.
The efficiency is also affected by the placement of the speaker. It is
doubled if it is mounted in a wall, compared to radiating in free
space. Efficiency increases even more if mounted in a corner etc. OK,
OK, I'm being picky and maybe that has nothing to do with the design
of the speaker. ...or maybe it does? If the speaker is designed for
free-field conditions, the speaker will still be radiating in
half-space toward higher frequencies, and thus have a lift of +6dB.
This should be compensated for. If the same speaker is mounted in the
wall, the HF boost will not occur (or rather, an equally large LF
boost will occur), so then no compensation is needed. So, the
placement of the speaker is something that the designer of the system
should consider.

Actually, no, the efficiency, specifically, the ratio of total
radiated acoustic power to total input electrical power does NOT
change. The sound pressure level on axis MAY change, but the
efficiency does not. The same power is distributed over a smaller
area, and since SPL is a measure of power per unit area, the SPL
changes, but the power output does not.

However, strictly speaking, the efficiency varies a lot with
frequency. When the motion is NOT mass-controlled, the situation is
completely different.

There is a specific definition for efficiency, which is very clear
on the meaning, that is, the efficiency above the system cutoff
but below the frequency where the wavelength is equal to the
circumference of the radiator. SMall and Thiele and others are quite
clear on this definition, and I defer to their definition.

For example, the efficiency for the closed box
peaks at the system resonance, but since the electrical impedance also
does, less power is delivered to the speaker (for a given voltage) and
the output is largely the same as for higher frequencies (-3dB for a
butterworth design). Well below the resonance it drops by 12
dB/octave. But hardly anyone speaks about efficiency as being varying
with frequency, "it is one number, period". In my opinion this adds to
the confusion regarding efficiency.

As the definition used in the domain is quite clear, no, it in
fact removes such confusion.

BTW is there a difference between "ported", "bass-reflex" and
"vented"?

Generally, these terms are synonymous.

"Sealed" and "acoustic suspension"? Aren't they synonyms?

No, indeed, they are not. While an acoustic suspension enclosure
is a sealed enclosure, the converse is not necessarily true.

A "sealed" enclosure can be defined broadly a number of ways, but
generally refers to any enclosure where the time constant of any
"leak" is MUCH longer than the time constant of the system cutoff
frequency. Also, any such leak cannot contrinute at all to the total
system output. Essentially, the enclosed air looks like a simple
acoustical compliance.

An "acoustic suspension" is defined as a subset of sealed box systems
where the acoustical compliance of the enclosure is substantially
smaller than the compliance of the driver suspension, and thus it
is the enclosure compliance that cominates the total system compliance.
Typically, this means that the enclosure volume is NO MORE than 1/4
the equivalent volume of compliance of the driver, specifically:

Vb = Vas / 4

In such an arrangement, the enclosure provides the major portion of
the system stuffness seen by the driver, and the amount of stiffness
provided by the suspension is relatively insignificant by comparison.

"Peter Larsen" wrote in message
...
Yes, as it was prior to foam getting intruced and because there are
quite many people who will not ever purchase anything with a foam
surround for some straaange reason.

The fact that I have many rubber, paper or cloth surround woofers still
working after 30 years or more, and all foam surrounds stuffed in much less
time, is probably reason enough for me.

TonyP.

"Peter Larsen" wrote in message
...
Yes, as it was prior to foam getting intruced and because there are
quite many people who will not ever purchase anything with a foam
surround for some straaange reason.

The fact that I have many rubber, paper or cloth surround woofers still
working after 30 years or more, and all foam surrounds stuffed in much less
time, is probably reason enough for me.

TonyP.

"Peter Larsen" wrote in message
...
Yes, as it was prior to foam getting intruced and because there are
quite many people who will not ever purchase anything with a foam
surround for some straaange reason.

The fact that I have many rubber, paper or cloth surround woofers still
working after 30 years or more, and all foam surrounds stuffed in much less
time, is probably reason enough for me.

TonyP.

"Peter Larsen" wrote in message
...
Yes, as it was prior to foam getting intruced and because there are
quite many people who will not ever purchase anything with a foam
surround for some straaange reason.

The fact that I have many rubber, paper or cloth surround woofers still
working after 30 years or more, and all foam surrounds stuffed in much less
time, is probably reason enough for me.

TonyP.

(Dick Pierce) wrote in message . com...
(Svante) wrote in message om...
(Dick Pierce) wrote in message

The efficiency of ANY direct-radiator system (bass reflex, ported, vented,
sealed, acoustic suspension, infinite baffle) is determined by the driver.
The driver's electrical resistance, its moving mass, its radiating area
and its magnet system determine that efficiency, period. The enclosure,
in combination with the driver, determines the system response function
near the low end cutoff.

I agree to your post, except for one little word; the "period" above.
The efficiency is also affected by the placement of the speaker. It is
doubled if it is mounted in a wall, compared to radiating in free
space. Efficiency increases even more if mounted in a corner etc. OK,
OK, I'm being picky and maybe that has nothing to do with the design
of the speaker. ...or maybe it does? If the speaker is designed for
free-field conditions, the speaker will still be radiating in
half-space toward higher frequencies, and thus have a lift of +6dB.
This should be compensated for. If the same speaker is mounted in the
wall, the HF boost will not occur (or rather, an equally large LF
boost will occur), so then no compensation is needed. So, the
placement of the speaker is something that the designer of the system
should consider.

Actually, no, the efficiency, specifically, the ratio of total
radiated acoustic power to total input electrical power does NOT
change. The sound pressure level on axis MAY change, but the
efficiency does not. The same power is distributed over a smaller
area, and since SPL is a measure of power per unit area, the SPL
changes, but the power output does not.

I think we had this discussion before, but then the issue was what
happens if there are two loudspeakers present. I waited for a final
post from you there, but failed to see it. The thread name was
"Speaker sensitivity and fs in multiples."

Actually I argue the the output power DOES increase. The wall acts as
a mirror (in the optical analogy) and the source and its mirror image
together double the sound pressure, and thus quadruples the intensity.
This leads to a level increase of +6dB. However, since the area hit by
this radiation is of half the size, the power is "only" increased by a
factor 2. Another way of seing it is that the radiation impedance is
doubled.

However, strictly speaking, the efficiency varies a lot with
frequency. When the motion is NOT mass-controlled, the situation is
completely different.

There is a specific definition for efficiency, which is very clear
on the meaning, that is, the efficiency above the system cutoff
but below the frequency where the wavelength is equal to the
circumference of the radiator. SMall and Thiele and others are quite
clear on this definition, and I defer to their definition.

OK, that's what most people do, and I see the benefits of doing so.
However, the original definition of efficiency (which can be applied
to many things, such as car motors etc) is the ratio between output
and input power.

For example, the efficiency for the closed box
peaks at the system resonance, but since the electrical impedance also
does, less power is delivered to the speaker (for a given voltage) and
the output is largely the same as for higher frequencies (-3dB for a
butterworth design). Well below the resonance it drops by 12
dB/octave. But hardly anyone speaks about efficiency as being varying
with frequency, "it is one number, period". In my opinion this adds to
the confusion regarding efficiency.

As the definition used in the domain is quite clear, no, it in
fact removes such confusion.

Any person who has heard the word "efficiency" in other contexts may
be confused IMO. And I guess those are not few.

BTW is there a difference between "ported", "bass-reflex" and
"vented"?

Generally, these terms are synonymous.

"Sealed" and "acoustic suspension"? Aren't they synonyms?

No, indeed, they are not. While an acoustic suspension enclosure
is a sealed enclosure, the converse is not necessarily true.

A "sealed" enclosure can be defined broadly a number of ways, but
generally refers to any enclosure where the time constant of any
"leak" is MUCH longer than the time constant of the system cutoff
frequency. Also, any such leak cannot contrinute at all to the total
system output. Essentially, the enclosed air looks like a simple
acoustical compliance.

An "acoustic suspension" is defined as a subset of sealed box systems
where the acoustical compliance of the enclosure is substantially
smaller than the compliance of the driver suspension, and thus it
is the enclosure compliance that cominates the total system compliance.
Typically, this means that the enclosure volume is NO MORE than 1/4
the equivalent volume of compliance of the driver, specifically:

Vb = Vas / 4

In such an arrangement, the enclosure provides the major portion of
the system stuffness seen by the driver, and the amount of stiffness
provided by the suspension is relatively insignificant by comparison.

OK, so in my mind they ARE principally the same, it is just a matter
of which compliance that dominates (which of course is not
insignificant when it comes to the actual design).

(Dick Pierce) wrote in message . com...
(Svante) wrote in message om...
(Dick Pierce) wrote in message

The efficiency of ANY direct-radiator system (bass reflex, ported, vented,
sealed, acoustic suspension, infinite baffle) is determined by the driver.
The driver's electrical resistance, its moving mass, its radiating area
and its magnet system determine that efficiency, period. The enclosure,
in combination with the driver, determines the system response function
near the low end cutoff.

I agree to your post, except for one little word; the "period" above.
The efficiency is also affected by the placement of the speaker. It is
doubled if it is mounted in a wall, compared to radiating in free
space. Efficiency increases even more if mounted in a corner etc. OK,
OK, I'm being picky and maybe that has nothing to do with the design
of the speaker. ...or maybe it does? If the speaker is designed for
free-field conditions, the speaker will still be radiating in
half-space toward higher frequencies, and thus have a lift of +6dB.
This should be compensated for. If the same speaker is mounted in the
wall, the HF boost will not occur (or rather, an equally large LF
boost will occur), so then no compensation is needed. So, the
placement of the speaker is something that the designer of the system
should consider.

Actually, no, the efficiency, specifically, the ratio of total
radiated acoustic power to total input electrical power does NOT
change. The sound pressure level on axis MAY change, but the
efficiency does not. The same power is distributed over a smaller
area, and since SPL is a measure of power per unit area, the SPL
changes, but the power output does not.

I think we had this discussion before, but then the issue was what
happens if there are two loudspeakers present. I waited for a final
post from you there, but failed to see it. The thread name was
"Speaker sensitivity and fs in multiples."

Actually I argue the the output power DOES increase. The wall acts as
a mirror (in the optical analogy) and the source and its mirror image
together double the sound pressure, and thus quadruples the intensity.
This leads to a level increase of +6dB. However, since the area hit by
this radiation is of half the size, the power is "only" increased by a
factor 2. Another way of seing it is that the radiation impedance is
doubled.

However, strictly speaking, the efficiency varies a lot with
frequency. When the motion is NOT mass-controlled, the situation is
completely different.

There is a specific definition for efficiency, which is very clear
on the meaning, that is, the efficiency above the system cutoff
but below the frequency where the wavelength is equal to the
circumference of the radiator. SMall and Thiele and others are quite
clear on this definition, and I defer to their definition.

OK, that's what most people do, and I see the benefits of doing so.
However, the original definition of efficiency (which can be applied
to many things, such as car motors etc) is the ratio between output
and input power.

For example, the efficiency for the closed box
peaks at the system resonance, but since the electrical impedance also
does, less power is delivered to the speaker (for a given voltage) and
the output is largely the same as for higher frequencies (-3dB for a
butterworth design). Well below the resonance it drops by 12
dB/octave. But hardly anyone speaks about efficiency as being varying
with frequency, "it is one number, period". In my opinion this adds to
the confusion regarding efficiency.

As the definition used in the domain is quite clear, no, it in
fact removes such confusion.

Any person who has heard the word "efficiency" in other contexts may
be confused IMO. And I guess those are not few.

BTW is there a difference between "ported", "bass-reflex" and
"vented"?

Generally, these terms are synonymous.

"Sealed" and "acoustic suspension"? Aren't they synonyms?

No, indeed, they are not. While an acoustic suspension enclosure
is a sealed enclosure, the converse is not necessarily true.

A "sealed" enclosure can be defined broadly a number of ways, but
generally refers to any enclosure where the time constant of any
"leak" is MUCH longer than the time constant of the system cutoff
frequency. Also, any such leak cannot contrinute at all to the total
system output. Essentially, the enclosed air looks like a simple
acoustical compliance.

An "acoustic suspension" is defined as a subset of sealed box systems
where the acoustical compliance of the enclosure is substantially
smaller than the compliance of the driver suspension, and thus it
is the enclosure compliance that cominates the total system compliance.
Typically, this means that the enclosure volume is NO MORE than 1/4
the equivalent volume of compliance of the driver, specifically:

Vb = Vas / 4

In such an arrangement, the enclosure provides the major portion of
the system stuffness seen by the driver, and the amount of stiffness
provided by the suspension is relatively insignificant by comparison.

OK, so in my mind they ARE principally the same, it is just a matter
of which compliance that dominates (which of course is not
insignificant when it comes to the actual design).

(Dick Pierce) wrote in message . com...
(Svante) wrote in message om...
(Dick Pierce) wrote in message

The efficiency of ANY direct-radiator system (bass reflex, ported, vented,
sealed, acoustic suspension, infinite baffle) is determined by the driver.
The driver's electrical resistance, its moving mass, its radiating area
and its magnet system determine that efficiency, period. The enclosure,
in combination with the driver, determines the system response function
near the low end cutoff.

I agree to your post, except for one little word; the "period" above.
The efficiency is also affected by the placement of the speaker. It is
doubled if it is mounted in a wall, compared to radiating in free
space. Efficiency increases even more if mounted in a corner etc. OK,
OK, I'm being picky and maybe that has nothing to do with the design
of the speaker. ...or maybe it does? If the speaker is designed for
free-field conditions, the speaker will still be radiating in
half-space toward higher frequencies, and thus have a lift of +6dB.
This should be compensated for. If the same speaker is mounted in the
wall, the HF boost will not occur (or rather, an equally large LF
boost will occur), so then no compensation is needed. So, the
placement of the speaker is something that the designer of the system
should consider.

Actually, no, the efficiency, specifically, the ratio of total
radiated acoustic power to total input electrical power does NOT
change. The sound pressure level on axis MAY change, but the
efficiency does not. The same power is distributed over a smaller
area, and since SPL is a measure of power per unit area, the SPL
changes, but the power output does not.

I think we had this discussion before, but then the issue was what
happens if there are two loudspeakers present. I waited for a final
post from you there, but failed to see it. The thread name was
"Speaker sensitivity and fs in multiples."

Actually I argue the the output power DOES increase. The wall acts as
a mirror (in the optical analogy) and the source and its mirror image
together double the sound pressure, and thus quadruples the intensity.
This leads to a level increase of +6dB. However, since the area hit by
this radiation is of half the size, the power is "only" increased by a
factor 2. Another way of seing it is that the radiation impedance is
doubled.

However, strictly speaking, the efficiency varies a lot with
frequency. When the motion is NOT mass-controlled, the situation is
completely different.

There is a specific definition for efficiency, which is very clear
on the meaning, that is, the efficiency above the system cutoff
but below the frequency where the wavelength is equal to the
circumference of the radiator. SMall and Thiele and others are quite
clear on this definition, and I defer to their definition.

OK, that's what most people do, and I see the benefits of doing so.
However, the original definition of efficiency (which can be applied
to many things, such as car motors etc) is the ratio between output
and input power.

For example, the efficiency for the closed box
peaks at the system resonance, but since the electrical impedance also
does, less power is delivered to the speaker (for a given voltage) and
the output is largely the same as for higher frequencies (-3dB for a
butterworth design). Well below the resonance it drops by 12
dB/octave. But hardly anyone speaks about efficiency as being varying
with frequency, "it is one number, period". In my opinion this adds to
the confusion regarding efficiency.

As the definition used in the domain is quite clear, no, it in
fact removes such confusion.

Any person who has heard the word "efficiency" in other contexts may
be confused IMO. And I guess those are not few.

BTW is there a difference between "ported", "bass-reflex" and
"vented"?

Generally, these terms are synonymous.

"Sealed" and "acoustic suspension"? Aren't they synonyms?

No, indeed, they are not. While an acoustic suspension enclosure
is a sealed enclosure, the converse is not necessarily true.

A "sealed" enclosure can be defined broadly a number of ways, but
generally refers to any enclosure where the time constant of any
"leak" is MUCH longer than the time constant of the system cutoff
frequency. Also, any such leak cannot contrinute at all to the total
system output. Essentially, the enclosed air looks like a simple
acoustical compliance.

An "acoustic suspension" is defined as a subset of sealed box systems
where the acoustical compliance of the enclosure is substantially
smaller than the compliance of the driver suspension, and thus it
is the enclosure compliance that cominates the total system compliance.
Typically, this means that the enclosure volume is NO MORE than 1/4
the equivalent volume of compliance of the driver, specifically:

Vb = Vas / 4

In such an arrangement, the enclosure provides the major portion of
the system stuffness seen by the driver, and the amount of stiffness
provided by the suspension is relatively insignificant by comparison.

OK, so in my mind they ARE principally the same, it is just a matter
of which compliance that dominates (which of course is not
insignificant when it comes to the actual design).

(Dick Pierce) wrote in message . com...
(Svante) wrote in message om...
(Dick Pierce) wrote in message

The efficiency of ANY direct-radiator system (bass reflex, ported, vented,
sealed, acoustic suspension, infinite baffle) is determined by the driver.
The driver's electrical resistance, its moving mass, its radiating area
and its magnet system determine that efficiency, period. The enclosure,
in combination with the driver, determines the system response function
near the low end cutoff.

I agree to your post, except for one little word; the "period" above.
The efficiency is also affected by the placement of the speaker. It is
doubled if it is mounted in a wall, compared to radiating in free
space. Efficiency increases even more if mounted in a corner etc. OK,
OK, I'm being picky and maybe that has nothing to do with the design
of the speaker. ...or maybe it does? If the speaker is designed for
free-field conditions, the speaker will still be radiating in
half-space toward higher frequencies, and thus have a lift of +6dB.
This should be compensated for. If the same speaker is mounted in the
wall, the HF boost will not occur (or rather, an equally large LF
boost will occur), so then no compensation is needed. So, the
placement of the speaker is something that the designer of the system
should consider.

Actually, no, the efficiency, specifically, the ratio of total
radiated acoustic power to total input electrical power does NOT
change. The sound pressure level on axis MAY change, but the
efficiency does not. The same power is distributed over a smaller
area, and since SPL is a measure of power per unit area, the SPL
changes, but the power output does not.

I think we had this discussion before, but then the issue was what
happens if there are two loudspeakers present. I waited for a final
post from you there, but failed to see it. The thread name was
"Speaker sensitivity and fs in multiples."

Actually I argue the the output power DOES increase. The wall acts as
a mirror (in the optical analogy) and the source and its mirror image
together double the sound pressure, and thus quadruples the intensity.
This leads to a level increase of +6dB. However, since the area hit by
this radiation is of half the size, the power is "only" increased by a
factor 2. Another way of seing it is that the radiation impedance is
doubled.

However, strictly speaking, the efficiency varies a lot with
frequency. When the motion is NOT mass-controlled, the situation is
completely different.

There is a specific definition for efficiency, which is very clear
on the meaning, that is, the efficiency above the system cutoff
but below the frequency where the wavelength is equal to the
circumference of the radiator. SMall and Thiele and others are quite
clear on this definition, and I defer to their definition.

OK, that's what most people do, and I see the benefits of doing so.
However, the original definition of efficiency (which can be applied
to many things, such as car motors etc) is the ratio between output
and input power.

For example, the efficiency for the closed box
peaks at the system resonance, but since the electrical impedance also
does, less power is delivered to the speaker (for a given voltage) and
the output is largely the same as for higher frequencies (-3dB for a
butterworth design). Well below the resonance it drops by 12
dB/octave. But hardly anyone speaks about efficiency as being varying
with frequency, "it is one number, period". In my opinion this adds to
the confusion regarding efficiency.

As the definition used in the domain is quite clear, no, it in
fact removes such confusion.

Any person who has heard the word "efficiency" in other contexts may
be confused IMO. And I guess those are not few.

BTW is there a difference between "ported", "bass-reflex" and
"vented"?

Generally, these terms are synonymous.

"Sealed" and "acoustic suspension"? Aren't they synonyms?

No, indeed, they are not. While an acoustic suspension enclosure
is a sealed enclosure, the converse is not necessarily true.

A "sealed" enclosure can be defined broadly a number of ways, but
generally refers to any enclosure where the time constant of any
"leak" is MUCH longer than the time constant of the system cutoff
frequency. Also, any such leak cannot contrinute at all to the total
system output. Essentially, the enclosed air looks like a simple
acoustical compliance.

An "acoustic suspension" is defined as a subset of sealed box systems
where the acoustical compliance of the enclosure is substantially
smaller than the compliance of the driver suspension, and thus it
is the enclosure compliance that cominates the total system compliance.
Typically, this means that the enclosure volume is NO MORE than 1/4
the equivalent volume of compliance of the driver, specifically:

Vb = Vas / 4

In such an arrangement, the enclosure provides the major portion of
the system stuffness seen by the driver, and the amount of stiffness
provided by the suspension is relatively insignificant by comparison.

OK, so in my mind they ARE principally the same, it is just a matter
of which compliance that dominates (which of course is not
insignificant when it comes to the actual design).

"Svante" wrote in message
om...
Actually I argue the the output power DOES increase. The wall
acts as

You can argue all you want but you will be wrong.

a mirror (in the optical analogy) and the source and its mirror
image
together double the sound pressure, and thus quadruples the
intensity.
This leads to a level increase of +6dB. However, since the area
hit by
this radiation is of half the size, the power is "only"
increased by a
factor 2. Another way of seing it is that the radiation
impedance is
doubled.

No. The output power of the driver does not change. The
efficiency does not change.

It's similar to changing a flashlight focus from a widebeam flood
to a narrow beam spot. The light may be directed to a smaller
area but the power output and efficiency of the bulb does not
change.

There is a specific definition for efficiency, which is very
clear
on the meaning, that is, the efficiency above the system
cutoff
but below the frequency where the wavelength is equal to the
circumference of the radiator. SMall and Thiele and others
are quite
clear on this definition, and I defer to their definition.

OK, that's what most people do, and I see the benefits of doing
so.
However, the original definition of efficiency (which can be
applied
to many things, such as car motors etc) is the ratio between
output
and input power.

As it is in this case. Acoustical output of the driver in watts
divided by electrical input in watts. You may be changing the
radiation pattern but the power output of the driver does not
change.

Any person who has heard the word "efficiency" in other
contexts may
be confused IMO. And I guess those are not few.

The context is the same in this situation.

"Svante" wrote in message
om...
Actually I argue the the output power DOES increase. The wall
acts as

You can argue all you want but you will be wrong.

a mirror (in the optical analogy) and the source and its mirror
image
together double the sound pressure, and thus quadruples the
intensity.
This leads to a level increase of +6dB. However, since the area
hit by
this radiation is of half the size, the power is "only"
increased by a
factor 2. Another way of seing it is that the radiation
impedance is
doubled.

No. The output power of the driver does not change. The
efficiency does not change.

It's similar to changing a flashlight focus from a widebeam flood
to a narrow beam spot. The light may be directed to a smaller
area but the power output and efficiency of the bulb does not
change.

There is a specific definition for efficiency, which is very
clear
on the meaning, that is, the efficiency above the system
cutoff
but below the frequency where the wavelength is equal to the
circumference of the radiator. SMall and Thiele and others
are quite
clear on this definition, and I defer to their definition.

OK, that's what most people do, and I see the benefits of doing
so.
However, the original definition of efficiency (which can be
applied
to many things, such as car motors etc) is the ratio between
output
and input power.

As it is in this case. Acoustical output of the driver in watts
divided by electrical input in watts. You may be changing the
radiation pattern but the power output of the driver does not
change.

Any person who has heard the word "efficiency" in other
contexts may
be confused IMO. And I guess those are not few.

The context is the same in this situation.

"Svante" wrote in message
om...
Actually I argue the the output power DOES increase. The wall
acts as

You can argue all you want but you will be wrong.

a mirror (in the optical analogy) and the source and its mirror
image
together double the sound pressure, and thus quadruples the
intensity.
This leads to a level increase of +6dB. However, since the area
hit by
this radiation is of half the size, the power is "only"
increased by a
factor 2. Another way of seing it is that the radiation
impedance is
doubled.

No. The output power of the driver does not change. The
efficiency does not change.

It's similar to changing a flashlight focus from a widebeam flood
to a narrow beam spot. The light may be directed to a smaller
area but the power output and efficiency of the bulb does not
change.

There is a specific definition for efficiency, which is very
clear
on the meaning, that is, the efficiency above the system
cutoff
but below the frequency where the wavelength is equal to the
circumference of the radiator. SMall and Thiele and others
are quite
clear on this definition, and I defer to their definition.

OK, that's what most people do, and I see the benefits of doing
so.
However, the original definition of efficiency (which can be
applied
to many things, such as car motors etc) is the ratio between
output
and input power.

As it is in this case. Acoustical output of the driver in watts
divided by electrical input in watts. You may be changing the
radiation pattern but the power output of the driver does not
change.

Any person who has heard the word "efficiency" in other
contexts may
be confused IMO. And I guess those are not few.

The context is the same in this situation.

"Svante" wrote in message
om...
Actually I argue the the output power DOES increase. The wall
acts as

You can argue all you want but you will be wrong.

a mirror (in the optical analogy) and the source and its mirror
image
together double the sound pressure, and thus quadruples the
intensity.
This leads to a level increase of +6dB. However, since the area
hit by
this radiation is of half the size, the power is "only"
increased by a
factor 2. Another way of seing it is that the radiation
impedance is
doubled.

No. The output power of the driver does not change. The
efficiency does not change.

It's similar to changing a flashlight focus from a widebeam flood
to a narrow beam spot. The light may be directed to a smaller
area but the power output and efficiency of the bulb does not
change.

There is a specific definition for efficiency, which is very
clear
on the meaning, that is, the efficiency above the system
cutoff
but below the frequency where the wavelength is equal to the
circumference of the radiator. SMall and Thiele and others
are quite
clear on this definition, and I defer to their definition.

OK, that's what most people do, and I see the benefits of doing
so.
However, the original definition of efficiency (which can be
applied
to many things, such as car motors etc) is the ratio between
output
and input power.

As it is in this case. Acoustical output of the driver in watts
divided by electrical input in watts. You may be changing the
radiation pattern but the power output of the driver does not
change.

Any person who has heard the word "efficiency" in other
contexts may
be confused IMO. And I guess those are not few.

The context is the same in this situation.

On Wed, 7 Jan 2004 03:58:09 -0600, "Rusty Boudreaux"
wrote:

"Svante" wrote in message
. com...
Actually I argue the the output power DOES increase. The wall
acts as

You can argue all you want but you will be wrong.


Betting is still open. . .

a mirror (in the optical analogy) and the source and its mirror
image
together double the sound pressure, and thus quadruples the
intensity.
This leads to a level increase of +6dB. However, since the area
hit by
this radiation is of half the size, the power is "only"
increased by a
factor 2. Another way of seing it is that the radiation
impedance is
doubled.

No. The output power of the driver does not change. The
efficiency does not change.

It's similar to changing a flashlight focus from a widebeam flood
to a narrow beam spot. The light may be directed to a smaller
area but the power output and efficiency of the bulb does not
change.


White light is incoherent and the wavlength of green, say 532 nm is
considerably shorter than, say, a 1cm filament. You analogy is
********.

There is a specific definition for efficiency, which is very
clear
on the meaning, that is, the efficiency above the system
cutoff
but below the frequency where the wavelength is equal to the
circumference of the radiator. SMall and Thiele and others
are quite
clear on this definition, and I defer to their definition.

OK, that's what most people do, and I see the benefits of doing
so.
However, the original definition of efficiency (which can be
applied
to many things, such as car motors etc) is the ratio between
output
and input power.

As it is in this case. Acoustical output of the driver in watts
divided by electrical input in watts. You may be changing the
radiation pattern but the power output of the driver does not
change.

Any person who has heard the word "efficiency" in other
contexts may
be confused IMO. And I guess those are not few.

The context is the same in this situation.

On Wed, 7 Jan 2004 03:58:09 -0600, "Rusty Boudreaux"
wrote:

"Svante" wrote in message
. com...
Actually I argue the the output power DOES increase. The wall
acts as

You can argue all you want but you will be wrong.


Betting is still open. . .

a mirror (in the optical analogy) and the source and its mirror
image
together double the sound pressure, and thus quadruples the
intensity.
This leads to a level increase of +6dB. However, since the area
hit by
this radiation is of half the size, the power is "only"
increased by a
factor 2. Another way of seing it is that the radiation
impedance is
doubled.

No. The output power of the driver does not change. The
efficiency does not change.

It's similar to changing a flashlight focus from a widebeam flood
to a narrow beam spot. The light may be directed to a smaller
area but the power output and efficiency of the bulb does not
change.


White light is incoherent and the wavlength of green, say 532 nm is
considerably shorter than, say, a 1cm filament. You analogy is
********.

There is a specific definition for efficiency, which is very
clear
on the meaning, that is, the efficiency above the system
cutoff
but below the frequency where the wavelength is equal to the
circumference of the radiator. SMall and Thiele and others
are quite
clear on this definition, and I defer to their definition.

OK, that's what most people do, and I see the benefits of doing
so.
However, the original definition of efficiency (which can be
applied
to many things, such as car motors etc) is the ratio between
output
and input power.

As it is in this case. Acoustical output of the driver in watts
divided by electrical input in watts. You may be changing the
radiation pattern but the power output of the driver does not
change.

Any person who has heard the word "efficiency" in other
contexts may
be confused IMO. And I guess those are not few.

The context is the same in this situation.

On Wed, 7 Jan 2004 03:58:09 -0600, "Rusty Boudreaux"
wrote:

"Svante" wrote in message
. com...
Actually I argue the the output power DOES increase. The wall
acts as

You can argue all you want but you will be wrong.


Betting is still open. . .

a mirror (in the optical analogy) and the source and its mirror
image
together double the sound pressure, and thus quadruples the
intensity.
This leads to a level increase of +6dB. However, since the area
hit by
this radiation is of half the size, the power is "only"
increased by a
factor 2. Another way of seing it is that the radiation
impedance is
doubled.

No. The output power of the driver does not change. The
efficiency does not change.

It's similar to changing a flashlight focus from a widebeam flood
to a narrow beam spot. The light may be directed to a smaller
area but the power output and efficiency of the bulb does not
change.


White light is incoherent and the wavlength of green, say 532 nm is
considerably shorter than, say, a 1cm filament. You analogy is
********.

There is a specific definition for efficiency, which is very
clear
on the meaning, that is, the efficiency above the system
cutoff
but below the frequency where the wavelength is equal to the
circumference of the radiator. SMall and Thiele and others
are quite
clear on this definition, and I defer to their definition.

OK, that's what most people do, and I see the benefits of doing
so.
However, the original definition of efficiency (which can be
applied
to many things, such as car motors etc) is the ratio between
output
and input power.

As it is in this case. Acoustical output of the driver in watts
divided by electrical input in watts. You may be changing the
radiation pattern but the power output of the driver does not
change.

Any person who has heard the word "efficiency" in other
contexts may
be confused IMO. And I guess those are not few.

The context is the same in this situation.

On Wed, 7 Jan 2004 03:58:09 -0600, "Rusty Boudreaux"
wrote:

"Svante" wrote in message
. com...
Actually I argue the the output power DOES increase. The wall
acts as

You can argue all you want but you will be wrong.


Betting is still open. . .

a mirror (in the optical analogy) and the source and its mirror
image
together double the sound pressure, and thus quadruples the
intensity.
This leads to a level increase of +6dB. However, since the area
hit by
this radiation is of half the size, the power is "only"
increased by a
factor 2. Another way of seing it is that the radiation
impedance is
doubled.

No. The output power of the driver does not change. The
efficiency does not change.

It's similar to changing a flashlight focus from a widebeam flood
to a narrow beam spot. The light may be directed to a smaller
area but the power output and efficiency of the bulb does not
change.


White light is incoherent and the wavlength of green, say 532 nm is
considerably shorter than, say, a 1cm filament. You analogy is
********.

There is a specific definition for efficiency, which is very
clear
on the meaning, that is, the efficiency above the system
cutoff
but below the frequency where the wavelength is equal to the
circumference of the radiator. SMall and Thiele and others
are quite
clear on this definition, and I defer to their definition.

OK, that's what most people do, and I see the benefits of doing
so.
However, the original definition of efficiency (which can be
applied
to many things, such as car motors etc) is the ratio between
output
and input power.

As it is in this case. Acoustical output of the driver in watts
divided by electrical input in watts. You may be changing the
radiation pattern but the power output of the driver does not
change.

Any person who has heard the word "efficiency" in other
contexts may
be confused IMO. And I guess those are not few.

The context is the same in this situation.