[Howard Davis[_2_]]

I have a pair of Legacy-1 speaker systems, now out of warranty, and two
speakers (the front-facing woofer in one system; the midrange in the other)
produce noticeable distortion at certain frequencies when tested with a
clean sine wave at low to moderate power levels. I have not heard anything
objectionable (yet) with music material. While they were still under
warranty it was necessary to replace a ribbon tweeter that failed in one
system.

I am still awaiting a reply from Legacy regarding the availability of exact
replacement speakers for these systems.

I have never abused these speakers. My Harmon-Kardon receiver can deliver
140W RMS maximum into 4 ohms, and the maximum rated amplifier power for
these speakers is 300W. I always operate them at reasonable levels, never
approaching the maximum power the amp can deliver.

It is unreasonable to expect that expensive high-performance speakers like
these will not become defective within 20 years if not abused?

[Audio_Empire]

In article ,
"Howard Davis" wrote:

I have a pair of Legacy-1 speaker systems, now out of warranty, and two
speakers (the front-facing woofer in one system; the midrange in the other)
produce noticeable distortion at certain frequencies when tested with a
clean sine wave at low to moderate power levels. I have not heard anything
objectionable (yet) with music material. While they were still under
warranty it was necessary to replace a ribbon tweeter that failed in one
system.

I am still awaiting a reply from Legacy regarding the availability of exact
replacement speakers for these systems.

I have never abused these speakers. My Harmon-Kardon receiver can deliver
140W RMS maximum into 4 ohms, and the maximum rated amplifier power for
these speakers is 300W. I always operate them at reasonable levels, never
approaching the maximum power the amp can deliver.

It is unreasonable to expect that expensive high-performance speakers like
these will not become defective within 20 years if not abused?

Are you referring to ADVENT Legacy 1 speakers (you don't specify)?

It depends upon how they are made. For instance, The old AR3ax speakers
from the late 1960's often had drivers fail after just 10 years due to
the paper drying-out. Older Magneplanars had the aluminum-wire voice
grids fail after just a few years if they were located where they got
direct sunlight. Seems that the adhesive used to adhere the voice grids
to the Mylar diaphragms was sensitive to UV and it would actually change
chemically and corrode away the aluminum voice grid wire so that
eventually the wire parted and the speaker failed. Infinity had a
similar problem with the EMIT and EMIM ribbon drivers used in their
better speakers. The etched copper voice grid on the diaphragm would get
hair-line cracks in it causing the unit to fail. If you knew what you
were doing, you could generally fix those yourself, though. None of
these failures are related to abuse.
Many modern cone speakers use synthetic materials such as Kevlar and
Polypropylene as cone materials and they generally don't fail like paper
cones did. Given the robustness of most voice coils and coil forms these
days, those speakers should outlast their owners as long as they aren't
abused.

If you are indeed talking about Advent's Legacy 1 speaker system, the
cones of the main drivers on those speakers were made from paper, and it
is quite possible that the dry heat found in most people's homes in the
winter will have, over a 20-year period, dried the paper out so that it
has started to come apart. If, on the other hand, you are talking about
the products of the company Legacy Audio, I can't say, except for the
general comments above.

[Howard Davis[_2_]]

"Audio_Empire" wrote in message
...
In article ,
"Howard Davis" wrote:

I have a pair of Legacy-1 speaker systems, now out of warranty, and two
speakers (the front-facing woofer in one system; the midrange in the
other)
produce noticeable distortion at certain frequencies when tested with a
clean sine wave at low to moderate power levels. I have not heard
anything
objectionable (yet) with music material. While they were still under
warranty it was necessary to replace a ribbon tweeter that failed in one
system.

I am still awaiting a reply from Legacy regarding the availability of
exact
replacement speakers for these systems.

I have never abused these speakers. My Harmon-Kardon receiver can deliver
140W RMS maximum into 4 ohms, and the maximum rated amplifier power for
these speakers is 300W. I always operate them at reasonable levels, never
approaching the maximum power the amp can deliver.

It is unreasonable to expect that expensive high-performance speakers
like
these will not become defective within 20 years if not abused?

Are you referring to ADVENT Legacy 1 speakers (you don't specify)?

Thank you for the reply.
No, These are from Legacy Audio, originally known as Reel to Real Designs.
Legacy Audio is easily found via Google search.
This particular speaker system model was subsequently renamed the Classic,
and I believe is no longer produced.

It depends upon how they are made. For instance, The old AR3ax speakers

I had a pair of the AR3a prior to buying the Legacies!

from the late 1960's often had drivers fail after just 10 years due to
the paper drying-out.

True!

Older Magneplanars had the aluminum-wire voice
grids fail after just a few years if they were located where they got
direct sunlight. Seems that the adhesive used to adhere the voice grids
to the Mylar diaphragms was sensitive to UV and it would actually change
chemically and corrode away the aluminum voice grid wire so that
eventually the wire parted and the speaker failed. Infinity had a
similar problem with the EMIT and EMIM ribbon drivers used in their
better speakers. The etched copper voice grid on the diaphragm would get
hair-line cracks in it causing the unit to fail. If you knew what you
were doing, you could generally fix those yourself, though. None of
these failures are related to abuse.
Many modern cone speakers use synthetic materials such as Kevlar and
Polypropylene as cone materials and they generally don't fail like paper
cones did. Given the robustness of most voice coils and coil forms these
days, those speakers should outlast their owners as long as they aren't
abused.

Legacy began using Kevlar cones in their midranges, but after I bought the
Legacy-1s that I have.
I doubt that the distortion-buzzing I now hear under test conditions is due
to the cone material - more likely the voice coils or cone suspension.

If you are indeed talking about Advent's Legacy 1 speaker system, the
cones of the main drivers on those speakers were made from paper, and it
is quite possible that the dry heat found in most people's homes in the
winter will have, over a 20-year period, dried the paper out so that it
has started to come apart. If, on the other hand, you are talking about
the products of the company Legacy Audio, I can't say, except for the
general comments above.

Thanks. I have still not received any response to my two inquiries to Legacy
Audio.
Viewing their most recent online catalog and comparing it with a catalog I
have from 1994, it appears they have somewhat downgraded their product line.
I'll report here on any response I receive from Legacy. When necessary to
replace these speakers, I will NOT be buying from this company - unless
perhaps they see fit to give me a good deal on speakers of equal or superior
quality.

[[email protected]]

On 28 Sep 2012 17:51:38 GMT, "Howard Davis" wrote:

It is unreasonable to expect that expensive high-performance speakers
like these will not become defective within 20 years if not abused?

Um, speakers do not "become" defective after 20 years. They are either defective
to start, or they fail. If they failed after 20 years, it's probably because
they wore out like everything else. Nothing lasts forever.

Thanks. I have still not received any response to my two inquiries to Legacy
Audio.

That surprises me. Did you try calling? Every time I called Legacy, I was
treated with extreme courtesy. But I haven't called in more years than I care to
admit.

(I note with interest that their current Web page shows them to be back in
Springfield. For a while they were in ... Pennsylvania, I think. Apparently
they've gone home again.)

When necessary to
replace these speakers, I will NOT be buying from this company - unless
perhaps they see fit to give me a good deal on speakers of equal or superior
quality.

If that is your opinion because they haven't responded, then perhaps I can
sympathize. But if you feel that way because a 20 year old set of speakers
finally bit the dust, I think you're being unreasonable. Legacy has always
produced very fine loudspeakers at a reasonable price, compared to competitors'
products of similar sound quality.

[Michael Bennet]

I haven't heard your original Classics, but I am very familiar with
Legacy as a company and I have their original Signature II speakers
from the 90's as well as the new Signature SE sitting side by side in
my room.

The new Signature SE is a huge leap forward in performance from the
origina l Signature II. (My Signature IIs from the 90's are still
performing like they did on day one.)

Their latest product line are incredible performers, and are superior
designs. Rohacell reinforced silver graphite drivers, cast frames,
rubber surrounds, AMT tweeters, and DSP correction with internal amps
in the larger systems, with a second to none fit and finish. This is
a well thought out, well designed, and value packed product line.

In my experience with the company, Doug and Bill have been nothing
short of exemplary in the customer service department. Perhaps your
correspondence isn't reaching them? Have you called in?

[Howard Davis[_2_]]

"Michael Bennet" wrote in message
...
I haven't heard your original Classics, but I am very familiar with
Legacy as a company and I have their original Signature II speakers
from the 90's as well as the new Signature SE sitting side by side in
my room.

The new Signature SE is a huge leap forward in performance from the
origina l Signature II. (My Signature IIs from the 90's are still
performing like they did on day one.)

Their latest product line are incredible performers, and are superior
designs. Rohacell reinforced silver graphite drivers, cast frames,
rubber surrounds, AMT tweeters, and DSP correction with internal amps
in the larger systems, with a second to none fit and finish. This is
a well thought out, well designed, and value packed product line.

In my experience with the company, Doug and Bill have been nothing
short of exemplary in the customer service department. Perhaps your
correspondence isn't reaching them? Have you called in?

Yes, Legacy products are no doubt still good value for the money, but
comparing their speakers of today with those in my 1994 and subsequent
catalogs, I see a decline in what one gets for their money. The most obvious
example is in their original Focus system, which I would have if I had the
space for them in my living room. The original Focus had three 12" low
frequency drivers. The Focus SE and Focus HD that replaced the original
Focus system appear in a my 2008 catalog, and have only TWO such woofers. I
consider this a pretty obvious downgrading of the original design, though
two such woofers per system are no doubt more than adequate in most rooms. I
could cite other such changes in their product line.

As an electronics engineer I admire their advanced, sophisticated designs as
seen in the Helix and Whisper, though these syatems seem better suited to
large theaters than home audio application. My problem is with the failure
of a ribbon tweeter, midrange, and woofer - THREE speakers, over the 18
years I have had my Legacy-1 systems, which I have not abused.

[Howard Davis[_2_]]

wrote in message
...
On 28 Sep 2012 17:51:38 GMT, "Howard Davis" wrote:

It is unreasonable to expect that expensive high-performance speakers
like these will not become defective within 20 years if not abused?

Um, speakers do not "become" defective after 20 years. They are either
defective
to start, or they fail. If they failed after 20 years, it's probably
because
they wore out like everything else. Nothing lasts forever.

When one spends a few thousand dollars on such durable products as
audiophile quality speakers, one has a reasonable right to expect their life
will at least exceed their own. Speakers, used well within the power levels
they were designed to handle, should not wear out.

Thanks. I have still not received any response to my two inquiries to
Legacy
Audio.

That surprises me. Did you try calling? Every time I called Legacy, I was
treated with extreme courtesy. But I haven't called in more years than I
care to
admit.

I received a response by email today, and will follow up by phone with
Legacy next week. This was NOT a response to my original emails to their
service and tech departments, but specifically stated it was due to my
posting to this newsgroup.

(I note with interest that their current Web page shows them to be back in
Springfield. For a while they were in ... Pennsylvania, I think.
Apparently
they've gone home again.)

When necessary to
replace these speakers, I will NOT be buying from this company - unless
perhaps they see fit to give me a good deal on speakers of equal or
superior
quality.

If that is your opinion because they haven't responded, then perhaps I can
sympathize. But if you feel that way because a 20 year old set of speakers
finally bit the dust, I think you're being unreasonable. Legacy has always
produced very fine loudspeakers at a reasonable price, compared to
competitors'
products of similar sound quality.

Legacy has finally responded, but as a result of my publicizing my issue
here. I thought this would elicit a response when direct communication
failed to do so! I am not criticizing the performance quality of their
speakers, but their durability.

[Audio_Empire]

In article ,
"Howard Davis" wrote:

wrote in message
...
On 28 Sep 2012 17:51:38 GMT, "Howard Davis" wrote:

It is unreasonable to expect that expensive high-performance speakers
like these will not become defective within 20 years if not abused?

Um, speakers do not "become" defective after 20 years. They are either
defective
to start, or they fail. If they failed after 20 years, it's probably
because
they wore out like everything else. Nothing lasts forever.

When one spends a few thousand dollars on such durable products as
audiophile quality speakers, one has a reasonable right to expect their life
will at least exceed their own. Speakers, used well within the power levels
they were designed to handle, should not wear out.

And why not? They are electromechanical devices subject to wear like any
other mechanical system. I think your expectations might be a tad
unreasonable. Most audiophile manufacturers are small companies. They
can't afford the kind of longevity testing that a big appliance company
like a TV maker or a washing machine company can do. The best that they
can hope for is to do their best in designing and manufacturing their
products and to stand behind them when they make mistakes choosing
components or processes whether over the long or the short haul.

Now that they have contacted you, I suspect that they will move heaven
and earth (within reason, of course) to do right by you. That's the
tradition of this industry.

[Greg Berchin[_3_]]

On 29 Sep 2012 17:50:37 GMT, "Howard Davis" wrote:

My problem is with the failure
of a ribbon tweeter, midrange, and woofer - THREE speakers, over the 18
years I have had my Legacy-1 systems, which I have not abused.

I am going to be a polite about this as I possibly can ...

If you have experienced excessive driver failures over eighteen years, with a
set of speakers from a manufacturer that, to the best of my knowledge, has an
excellent reputation for quality, then perhaps the problem is that your speakers
HAVE been abused. (My Focus system from the early 1990s still seems to be in
excellent shape. But after twenty years, if one or more of the drivers was found
to have deteriorated to the point of failure, I would not attribute it to a
"defect".)

I do not intend any offense by my comment, only to note that "abuse" takes many
forms and not all of them are intentional. Does your amplifier output DC-offset
when overdriven? Is there an ozone source anywhere in your home? Were the
drivers exposed to direct sunlight through a window? The possibilities are
endless.

[Howard Davis[_2_]]

"Audio_Empire" wrote in message
...
In article ,
"Howard Davis" wrote:

wrote in message
...
On 28 Sep 2012 17:51:38 GMT, "Howard Davis"
wrote:

It is unreasonable to expect that expensive high-performance speakers
like these will not become defective within 20 years if not abused?

Um, speakers do not "become" defective after 20 years. They are either
defective
to start, or they fail. If they failed after 20 years, it's probably
because
they wore out like everything else. Nothing lasts forever.

When one spends a few thousand dollars on such durable products as
audiophile quality speakers, one has a reasonable right to expect their
life
will at least exceed their own. Speakers, used well within the power
levels
they were designed to handle, should not wear out.

And why not? They are electromechanical devices subject to wear like any
other mechanical system. I think your expectations might be a tad
unreasonable. Most audiophile manufacturers are small companies. They
can't afford the kind of longevity testing that a big appliance company
like a TV maker or a washing machine company can do. The best that they
can hope for is to do their best in designing and manufacturing their
products and to stand behind them when they make mistakes choosing
components or processes whether over the long or the short haul.

Of course nothing is 100% reliable or can last forever, but to have THREE
speakers fail over an 18 year period (in two systems with a total of 6
speakers each, or 12 speakers), without abuse of any kind, is a bit too
much! That is a 25% failure rate!

Now that they have contacted you, I suspect that they will move heaven
and earth (within reason, of course) to do right by you. That's the
tradition of this industry.

Hopefully!

[Audio_Empire]

In article ,
Greg Berchin wrote:

On 29 Sep 2012 17:50:37 GMT, "Howard Davis" wrote:

My problem is with the failure
of a ribbon tweeter, midrange, and woofer - THREE speakers, over the 18
years I have had my Legacy-1 systems, which I have not abused.

I am going to be a polite about this as I possibly can ...

If you have experienced excessive driver failures over eighteen years, with a
set of speakers from a manufacturer that, to the best of my knowledge, has an
excellent reputation for quality, then perhaps the problem is that your
speakers
HAVE been abused. (My Focus system from the early 1990s still seems to be in
excellent shape. But after twenty years, if one or more of the drivers was
found
to have deteriorated to the point of failure, I would not attribute it to a
"defect".)

I do not intend any offense by my comment, only to note that "abuse" takes
many
forms and not all of them are intentional. Does your amplifier output
DC-offset
when overdriven? Is there an ozone source anywhere in your home? Were the
drivers exposed to direct sunlight through a window? The possibilities are
endless.

Most people don't realize that too small of an amplifier for a given
speaker is generally much more prone to damage the drivers than is a too
big of an amplifier. Small amp clips a lot exceeding the duty cycle of
the voice coils which heat up and warp the coil form, or worse, burn-out
the coil. The bottom line with this avenue of thought is that people can
abuse speakers without even realizing it. Not casting aspersions here,
or saying that this is what happened with Legacy's in question. Just
pointing out that all is not always as it seems......

[Howard Davis[_2_]]

"Greg Berchin" wrote in message
...
On 29 Sep 2012 17:50:37 GMT, "Howard Davis" wrote:

My problem is with the failure
of a ribbon tweeter, midrange, and woofer - THREE speakers, over the 18
years I have had my Legacy-1 systems, which I have not abused.

I am going to be a polite about this as I possibly can ...

If you have experienced excessive driver failures over eighteen years,
with a
set of speakers from a manufacturer that, to the best of my knowledge, has
an
excellent reputation for quality, then perhaps the problem is that your
speakers
HAVE been abused. (My Focus system from the early 1990s still seems to be
in
excellent shape. But after twenty years, if one or more of the drivers was
found
to have deteriorated to the point of failure, I would not attribute it to
a
"defect".)

I do not intend any offense by my comment, only to note that "abuse" takes
many
forms and not all of them are intentional. Does your amplifier output
DC-offset
when overdriven? Is there an ozone source anywhere in your home? Were the
drivers exposed to direct sunlight through a window? The possibilities are
endless.

My amp can deliver 140W RMS per channel into 4 ohms. The Legacy-1 is rated
for use with amps up to 300W. My oscilloscope shows no DC offset from the
amp, and even if there was, it could not affect the midrange or tweeter. The
speakers are in a temperature controlled living space and not in direct
sunlight, which the grills would protect them from if they were.
I do not run the speakers even close to the maximum power capabilities of
the amp.
Three out of a total of 12 drivers have failed over an 18 year period. That
is a 25% failure rate!
Two of the drivers - a woofer and a midrange - still function, and the
defects are only audible with a sine wave input. If there is any problem
with musical program material I cannot hear it, but certainly these speakers
in time will only deteriorate further to the point of unacceptable
performance.

[Greg Berchin[_3_]]

On 30 Sep 2012 20:54:37 GMT, "Howard Davis" wrote:

My amp can deliver 140W RMS per channel into 4 ohms. The Legacy-1 is rated
for use with amps up to 300W.

...

Two of the drivers - a woofer and a midrange - still function, and the
defects are only audible with a sine wave input. If there is any problem
with musical program material I cannot hear it, but certainly these speakers
in time will only deteriorate further to the point of unacceptable
performance.

Well, I think I see your problem.

Be aware that rating a speaker "for use with 300W amp" does NOT mean that each
individual driver can safely absorb 300W sine waves. The woofer may be able to
handle 200W, the midrange perhaps 75W, and the tweeter maybe 25W. But with
"typical" musical material, even when the amplifier is delivering 300W, none of
the individual drivers will be overpowered because of the power spectrum of the
music.

Now, if you're sending 140W sine waves to midranges that are rated at only 75W,
or to tweeters that are rated at only 25W, then the "defects" that you hear are
only the drivers' cries of anguish as their voice coils are being melted; their
ribbons being torn to shreds.

[Howard Davis[_2_]]

"Greg Berchin" wrote in message
...
On 30 Sep 2012 20:54:37 GMT, "Howard Davis" wrote:

My amp can deliver 140W RMS per channel into 4 ohms. The Legacy-1 is rated
for use with amps up to 300W.

...

Two of the drivers - a woofer and a midrange - still function, and the
defects are only audible with a sine wave input. If there is any problem
with musical program material I cannot hear it, but certainly these
speakers
in time will only deteriorate further to the point of unacceptable
performance.

Well, I think I see your problem.

Be aware that rating a speaker "for use with 300W amp" does NOT mean that
each
individual driver can safely absorb 300W sine waves. The woofer may be
able to
handle 200W, the midrange perhaps 75W, and the tweeter maybe 25W. But with
"typical" musical material, even when the amplifier is delivering 300W,
none of
the individual drivers will be overpowered because of the power spectrum
of the
music.

The drivers' deterioration could not have been caused by sine wave
operation, as I have only done that for test purposes, and when I do it I am
careful to keep the power at a reasonable level. I am an electronics
engineer and know better than to drive a midrange or tweeter with a sine
wave at a level anywhere near the system's power rating.

Now, if you're sending 140W sine waves to midranges that are rated at only
75W,
or to tweeters that are rated at only 25W, then the "defects" that you
hear are
only the drivers' cries of anguish as their voice coils are being melted;
their
ribbons being torn to shreds.

In testing I was driving with perhaps 25W RMS maximum, though I did not
measure it. When reaching the tweeters' range I decreased the power level
even further.
If the woofer cannot handle this without an audible buzz, even below 30 Hz,
it is certainly defective. This only happens in one of my two Legacy-1
systems, and thus it reveals a defective driver.
The midrange of the other of the two systems has an apparent resonant peak
(maximum cone motion) at about 150 Hz, at which a buzzing distortion occurs.
The other system's midrange does not do this.

[John Stone]

On 9/30/12 3:54 PM, in article , "Howard
Davis" wrote:
Two of the drivers - a woofer and a midrange - still function, and the
defects are only audible with a sine wave input. If there is any problem
with musical program material I cannot hear it, but certainly these speakers
in time will only deteriorate further to the point of unacceptable
performance.

Do the woofers and midranges use foam in the surrounds? These kinds of
surrounds will certainly rot away after 18 years. If not, other things to
look for are deterioration of the glued joints between the cone and
surround, surround and basket, or around the dust cap. Sometimes you can
press against the various parts and get the distortion to go away. But
repairing such problems usually requires replacement of the driver.
Unfortunately, a small manufacturer like Legacy will not have much control
over the manufacturing process of the drivers they use. They have to hope
that their driver OEM has made good choices on choosing materials that stay
together over the long term. But there are many factors involved in choice
of things like adhesives beyond just long term durability. These include
their impact on acoustic performance, as well as environmental regulations.
Deterioration of drivers over an extended period is hard to predict, and
failure of drivers after 18 years, while disappointing, is also far from
unusual.
Your best bet is to work with the manufacturer to solve the problem
..

[MBennet]

The answer to your problem is to call Legacy.
I just talked to them last week, and they kindly answered all of my questions.

I have Legacy speakers that are old as well, and they are still performing great.

I love my Legacy's- old and new. But, the new ones absolutely devastate the old ones!

[Howard Davis[_2_]]

"John Stone" wrote in message
...
On 9/30/12 3:54 PM, in article , "Howard
Davis" wrote:
Two of the drivers - a woofer and a midrange - still function, and the
defects are only audible with a sine wave input. If there is any problem
with musical program material I cannot hear it, but certainly these
speakers
in time will only deteriorate further to the point of unacceptable
performance.

Do the woofers and midranges use foam in the surrounds? These kinds of
surrounds will certainly rot away after 18 years. If not, other things to
look for are deterioration of the glued joints between the cone and
surround, surround and basket, or around the dust cap. Sometimes you can
press against the various parts and get the distortion to go away. But
repairing such problems usually requires replacement of the driver.
Unfortunately, a small manufacturer like Legacy will not have much control
over the manufacturing process of the drivers they use. They have to hope
that their driver OEM has made good choices on choosing materials that
stay
together over the long term. But there are many factors involved in choice
of things like adhesives beyond just long term durability. These include
their impact on acoustic performance, as well as environmental
regulations.
Deterioration of drivers over an extended period is hard to predict, and
failure of drivers after 18 years, while disappointing, is also far from
unusual.
Your best bet is to work with the manufacturer to solve the problem

Legacy I'm sure always knew better than to allow their driver manufacturers
to use foam surrounds.
I'll be calling the company soon, and hopefully they can offer exact
replacements for the defective speakers.
Buyers of speaker systems like these should not experience a 25% driver
failure rate over 18 years!

[Dick Pierce[_2_]]

Howard Davis wrote:
Legacy I'm sure always knew better than to allow their driver manufacturers
to use foam surrounds.

Sorry, that's not a choice one gets to make like choosing the
color of your socks. The particular mechanical properties of
the surround is the number one criteria used for choosing
the surround. Compressed foam offers a combination of mass,
stiffness, mechanical losses and linearity that's not easily
matched by other materials. It may well be that a particular
set of such parameters was required and non other material
came close.

It's certainly not an issue of cost: the actual difference
in cost between a foam surround and other materials is
small, and the surround is far from being the most expensive
component in a driver. The combination of magnet hard and
soft parts, basket, voice coil cone and manufacturing overhead
comprise perhaps no less than 80% of the total cost of a driver:
the surround might be 5% at most of the total cost. A factor
of two difference in the cost of a surround makes a very small
differnce in the total cost of the driver to the driver
manufacturer.

And all foam is not the same. There are a number of formulations
that have greater longevity than others.

But, with all due respect, and not intending to denigrate, a
statement like, "Legacy I'm sure always knew better than to
allow their driver manufacturers to use foam surrounds" shows
a rather naive view of the determining factors in driver
design, construction, performance and selection.

--
+--------------------------------+
+ Dick Pierce |
+ Professional Audio Development |
+--------------------------------+

[Dick Pierce[_2_]]

Howard Davis wrote:
The midrange of the other of the two systems has an apparent resonant peak
(maximum cone motion) at about 150 Hz, at which a buzzing distortion occurs.
The other system's midrange does not do this.

A number of factors could contrinute to this, some of them
are not even consdered as "defects".

Your observation that maximum cone excursion occurs at 150
Hz, and that correpsonds to the prinsiple mechanical resonance
is probably fairly accurate. One thing that often can occur
is that if the flex lead from the terminal to the voice coil
is not properly dressed, it can buzz from contact with the
back of the cone. This is not an uncommon problem and is
easily corrected: If you can take the driver out of the
enclosure and tune through the resonance (which may well
be at a somewhat different frequency) while observing the
lead, you may actually see it hitting the back of the cone.
Carefully take a long, non-magnetic probe (a coffee stirrer
would work well, and try gently moving the lead around. Often
just touching it is enough to make the problem dramatically
better or worse for a second or two.

Another experiment you might perform is while the driver is
producing the buzzing, try offsetting the axis of the cone
by gently pressing on the edge of the surround at different
points along its circumference. If you find at one point
it gets better while at anpther it gets worse, then you may
have a slightly miscentered cone. Often simply taking it out,
rotating 180 degrees and putting it back in might make the problem
go away.

Also, try simply removing the drivers and screweing it back in,
making sure all screws are tightened evenly and that all gasket
material is properly placed.

You also might have some foreign material in the gap.

Also chekc out is there is a loose component somewhere in the
speaker, like a rattling terminal or crossover component.

If none of these fixes work, then its more probably you have an
actual defect, like a dropped voice coil winding, or some sort
of foreign object in the cap, or the like.

--
+--------------------------------+
+ Dick Pierce |
+ Professional Audio Development |
+--------------------------------+

[Dick Pierce[_2_]]

Howard Davis wrote:
The
speakers are in a temperature controlled living space and not in direct
sunlight, which the grills would protect them from if they were.

That's assuming direct sunlight is the culprit: mostly it is
not. A lot of deterioration is due to environmental factors
such as fairly common air pollution, ozone being one possble
agent.
My own experience over about 40 years suggest that same speakers
used in similar ways in urban environments suffer higher long-
term failures due to material degredation, e.g., adhesive degredation
and so on.

Plastics, in general, due not do well in long-term stability.
The can suffer both evaporative losses of plasticizing agents
as well as absorbtion of foreign substances. You might counter
that this would all similar drivers at the same time. Statistically,
that's true, but there is absolutely no assurance that two
identical drivers are, indeed, identical to that degree. They may
be all going down, and the ones you have detected just happen to
be on that side of the bell curve.

Two of the drivers - a woofer and a midrange - still function, and the
defects are only audible with a sine wave input. If there is any problem
with musical program material I cannot hear it, but certainly these speakers
in time will only deteriorate further to the point of unacceptable
performance.

That does not necessarily follow. If you had run the same tests,
say, two or five years ago and gotten significantly different
results then, maybe, they are on their way out. But, as far as I am
able to detect from the thread, that may not be the case.

--
+--------------------------------+
+ Dick Pierce |
+ Professional Audio Development |
+--------------------------------+

[Howard Davis[_2_]]

"Dick Pierce" wrote in message
...
Howard Davis wrote:
The midrange of the other of the two systems has an apparent resonant
peak (maximum cone motion) at about 150 Hz, at which a buzzing distortion
occurs. The other system's midrange does not do this.

A number of factors could contrinute to this, some of them
are not even consdered as "defects".

Your observation that maximum cone excursion occurs at 150
Hz, and that correpsonds to the prinsiple mechanical resonance
is probably fairly accurate. One thing that often can occur
is that if the flex lead from the terminal to the voice coil
is not properly dressed, it can buzz from contact with the
back of the cone. This is not an uncommon problem and is
easily corrected: If you can take the driver out of the
enclosure and tune through the resonance (which may well
be at a somewhat different frequency) while observing the
lead, you may actually see it hitting the back of the cone.
Carefully take a long, non-magnetic probe (a coffee stirrer
would work well, and try gently moving the lead around. Often
just touching it is enough to make the problem dramatically
better or worse for a second or two.

Thanks - I'm familiar with voice coil lead buzz and what to do for it. In my
case, it is not the problem.

Today I removed the midrange driver, leaving it electrically connected, for
further testing. It turns out that the driver is OK; the resonant buzz
around 150Hz is coming from WITHIN THE CABINET! I am now in contact with
Legacy. They are very courteous and helpful, and I am satisfied they will
advise me on fixing this - hopefully by working through the driver openings
in the cabinet. The woofer buzz in the other system IS from the woofer,
which must be replaced.

Another experiment you might perform is while the driver is
producing the buzzing, try offsetting the axis of the cone
by gently pressing on the edge of the surround at different
points along its circumference. If you find at one point
it gets better while at anpther it gets worse, then you may
have a slightly miscentered cone. Often simply taking it out,
rotating 180 degrees and putting it back in might make the problem
go away.

This did not help with the woofer.

Also, try simply removing the drivers and screweing it back in,
making sure all screws are tightened evenly and that all gasket
material is properly placed.

Tried that too.

You also might have some foreign material in the gap.

Also chekc out is there is a loose component somewhere in the
speaker, like a rattling terminal or crossover component.

If none of these fixes work, then its more probably you have an
actual defect, like a dropped voice coil winding, or some sort
of foreign object in the cap, or the like.

--
+--------------------------------+
+ Dick Pierce |
+ Professional Audio Development |
+--------------------------------+

Thank you for the advice!

[Howard Davis[_2_]]

"Dick Pierce" wrote in message
...
Howard Davis wrote:
Legacy I'm sure always knew better than to allow their driver
manufacturers to use foam surrounds.

Sorry, that's not a choice one gets to make like choosing the
color of your socks. The particular mechanical properties of
the surround is the number one criteria used for choosing
the surround. Compressed foam offers a combination of mass,
stiffness, mechanical losses and linearity that's not easily
matched by other materials. It may well be that a particular
set of such parameters was required and non other material
came close.

It's certainly not an issue of cost: the actual difference
in cost between a foam surround and other materials is
small, and the surround is far from being the most expensive
component in a driver. The combination of magnet hard and
soft parts, basket, voice coil cone and manufacturing overhead
comprise perhaps no less than 80% of the total cost of a driver:
the surround might be 5% at most of the total cost. A factor
of two difference in the cost of a surround makes a very small
differnce in the total cost of the driver to the driver
manufacturer.

And all foam is not the same. There are a number of formulations
that have greater longevity than others.

But, with all due respect, and not intending to denigrate, a
statement like, "Legacy I'm sure always knew better than to
allow their driver manufacturers to use foam surrounds" shows
a rather naive view of the determining factors in driver
design, construction, performance and selection.

Naive??
We all have our areas of expertise; mine is analog circuit design, not
speaker design.
I am an analog circuit design engineer that has designed guitar effects for
some of the world's best known rock bands. I invented, among other things,
the Pigtronix Mothership Guitar Synthesizer.
What I meant is that Legacy, I am sure, chose their speaker materials or
instructed their makers to choose them with durability in mind as well as
other desirable characteristics. My experience with driver failure is
probably far from typical in Legacy products.

[Dick Pierce[_2_]]

Howard Davis wrote:
"Dick Pierce" wrote in message
...

Howard Davis wrote:

Legacy I'm sure always knew better than to allow their driver
manufacturers to use foam surrounds.

Sorry, that's not a choice one gets to make like choosing the
color of your socks. The particular mechanical properties of
the surround is the number one criteria used for choosing
the surround. Compressed foam offers a combination of mass,
stiffness, mechanical losses and linearity that's not easily
matched by other materials. It may well be that a particular
set of such parameters was required and non other material
came close.

It's certainly not an issue of cost: the actual difference
in cost between a foam surround and other materials is
small, and the surround is far from being the most expensive
component in a driver. The combination of magnet hard and
soft parts, basket, voice coil cone and manufacturing overhead
comprise perhaps no less than 80% of the total cost of a driver:
the surround might be 5% at most of the total cost. A factor
of two difference in the cost of a surround makes a very small
differnce in the total cost of the driver to the driver
manufacturer.

And all foam is not the same. There are a number of formulations
that have greater longevity than others.

But, with all due respect, and not intending to denigrate, a
statement like, "Legacy I'm sure always knew better than to
allow their driver manufacturers to use foam surrounds" shows
a rather naive view of the determining factors in driver
design, construction, performance and selection.

Naive??

Yes, "naive," as in "having or showing a lack of experience,
information".

What I meant is that Legacy, I am sure, chose their speaker materials or
instructed their makers to choose them with durability in mind as well as
other desirable characteristics.

But what if a manufacturer is faced with the tradeoff between,
say, performance and durability? Which is the better choice?

Let me give you an example. When I was running driver design
for a number of clients, I had several examples of manufacturers
who needed a 6.5" driver with a combination of a fairly low
moving mass and high compliance. In addition, they specified a
specific formulation of plastic for the cone.

Here where the choices available:

1. Polybutadene-styrene alloy (commonly referred to as "rubber"):
Too much mass, too much stiffness, and the adhesive that was
compatible with the surround was incompatible with the cone
material, and vice versa,

2. Accordion-pleated doped paper: far too little linear excursion,
almost no internal damping that was worth anything, compliance
was too low.

3. Doped cloth surround: compliance was far too high, poor internal
damping.

4. Compressed foam: compliance off-the shelf was a bit low,
damping was about right, mass was just about what was needed,
had the linear excrusion needed.

The ONLY choice for these manufacturers was to have the surround
manufacturer use a slightly thinner material (which was easy to do),
I designed the out-of-the-press compliance a wee too high and
the mass a wee too low, then the surrounds were coated with a
clear latex-based sealer which got the compliance and mass just
about right and gave the damping we needed. They also were compatible
with the adhesive we needed.

So here was the dilemma: Assume, for the moment, these foam
surrounds had the durability issue you mentioned (they didn't,
because of the sealer): the choice to these manufacturers
were a near-ideal driver for there applications that might have
a long-term durability issue vs. no driver at all.

What choice would you make?

Now, here are some questions: what's the warranty period on your
speakers? What's the typical warranty period? WHy is the warranty
period so limited?

Because, very simply, the cost, to the manufacturer, of supporting
warranty service on speakers is very low until you get to a point
were durability issues start climbing. It's such that the difference,
say, between a 5-year warranty and a 10-year warranty might require
the manufacturer to DOUBLE the price of a speaker to cover the losses
entailed by the greater failure rate as the speakers wear out.

Yes, speaker ABSOLUTELY do wear out, no doubt about it. Yes, foam
crumbles, but as well, adhesives get brittle and fail (ESPECIALLY
around the voice coil, where the temperatures can easily get VERY
high under normal use), metals fatigue, aluminum voice coils
fail due to a process called "hydrogen embrittlement", the varnish
holding the voivl coil dinsings in place eventually gets brittle
and dries out, the magnets loose their strength. Plastics become
embrittled as volatile pasticizers evaporate. And on and on...

NONE of these are "manufacturing defects." They are the intrinsic
properties of the materials and methods used.

My experience with driver failure is
probably far from typical in Legacy products.

That may well be true. But that's different from declaring
"Legacy I'm sure always knew better than to allow their driver
manufacturers to use foam surrounds" if, for no other reason,
that neither you nor I know what Legacy did or did not know
better and what particular business, marketing and engineering
decisions led to what they did or did not allow their vendors
to do.

Though, having been responsible for the design and manufacturing
of many thousands of drivers, and having examined and performed
autopsies on a very large number of drivers, I suspect that
I might legitimately lay claim having a bit more insight into
the process.

--
+--------------------------------+
+ Dick Pierce |
+ Professional Audio Development |
+--------------------------------+

[Dick Pierce[_2_]]

Howard Davis wrote:
"Dick Pierce" wrote in message
A classic example at the theoretical level is the hard-
constrained relation between enclosure volume, cutoff
frequency and in-band efficiency. For a given enclosure
type, the product of these three parameter CANNOT EVER
exceed a constant (well, to be more precise, it's
the product opf the enclosure size, efficiency and the
cube of the cutoff frequency).

Which is why the sealed box (acoustic suspension) design,
as in the AR3a, is inefficient.

Since this thread has migrated off into a tangent, no harm in
letting it wander a bit more. I saw a teachable moment.

It's a little difficult to parse your sentence here, but it
has shades of a very common misconception when it comes to
speakers.

As stated, one implication of the statement,

"Which is why the sealed box (acoustic suspension) design,
as in the AR3a, is inefficient."

is that putting a driver in a sealed box makes it inefficient,
or, conversely, turning a sealed box into a reflex makes it
MORE efficient.

Both of these statements are technically wrong. For all direct-
radiator systems, it's not the box that determines the
efficiency, it's the driver. The system's efficiency (that is,
it's efficiency in its passband) is determined by the relation
of a small handful of parameters unique to the driver itself:
moving mass, DC resistance of the voice coil, and the Bl product
of the magnet/voice coil system. Take any given driver and put
it in pretty much any direct-radiator enclosure, and the passband
efficiency of the system DOES NOT CHANGE.

Now, that may seem contradictory to my earlier statement, but it
is, in fact, completely consistent with it.

Let's take the AR3 you cited as an example. It's about 1.4 cubic
feet in volume and has a system resonance of about 43 Hz, and a Q
at resonance of about 1.2 or so. In order to achieve that
low a resonance in an enclosure that small requires that the
moving mass of the cone has to a certain value. Now, to achieve
the Q at resonance desired, it has to have a specific combination
of Bl product and voice coil resistance (since it's the electrical
damping that dominates the total system damping).

Now, look at what I said a little farther up: the passband
efficiency of the driver is determined by its moving mass,
DC resistance and Bl product.

So, to achieve the system response AR wanted, they HAD to use
a driver with a specific mass, DC resistance and Bl product.

Thus, the system design parameters dictated the driver efficiency
needed for the enclosure. Choosing a driver with higher efficiency
could have been accomplished a number of ways:

1. Reduce the moving mass of the driver:
Yes, the efficiency would have gone up, to be sure, but so
too would the system resonance, and the system Q would go
down: you'd no longer have the cutoff frequency and low-
frequency response of an AR3,

2. Reduce the DC resistance of the voice coil:
This, too, would have increased efficiency, but with several
side effects and complications of its own.

a. Reducing the DC resistance itself (if possible, see the next
point would have resulted in a reduction in the system's
electrical Q, with the result the the system Q would no
longer by 1.2, but would have been less, raising the
cutoff frequency of the system,

b. HOW you reduce the DC resistance is the real trick: you
have some severe limitations as to how to go about this:

i Use a larger gauge wi that has two effects: one,
it means fewer winding per inch, which results in less
wire in the magnetic field (l), which means lower Bl product
(see #3 below) and thus less efficiency, and two, it
means the voice coil outer diameter is greater, which
requires a wider magnetic gap. A wider magnetic gap
reduces the field density (B) and thus a lower Bl
product

ii Use a shorter winding, less overhang:
Means you reduce the linear excursion of the woofer,

c. The DC resistance of an AR3 is already pretty low, around
3 ohms. Reducing it further would have made a number of
contemporary amplifiers (notably the AR amplifier, ironically),
VERY unhappy.

3. Increase the BL product of the driver:
Well, a bigger magnet might seem the way to go, but it's actually
the fact that it's the low-carbon soft steel used for the front
plate that sets the limit the the gap is run pretty much at or
near saturation: a bigger magnet simply ends up increasing the
leakage elsewhere without increasing the flux density at all.
So that's not a choice.

You could increase the length of the voice coil winding in the gap,
which you could do by either decreasing the wire gauge (smaller
diameter) or adding more layers: both of these result in MORE
DC resistance, reducing the efficiency there.

Or, you could increase the width of the gap with a thicker front
plate and more magnet to compensate to get back up to saturation.
But, remember, increasing the Bl product also reduces electrical Q,
overdamping the system and raising the cutoff frequency. Also, to
then achieve the same linear excursion, you'd have to increase
with length of the voice coil, increasing the DC resistance and
thus reducing the the efficiency there.

So, if you want a 1.5 cubic foot sealed system with a cutoff of
43 Hz and a Q of 1.2, the only way to do it is with a driver of
such-and-such efficiency.

If you wanted to do a reflex system in 1.5 cubic feet with a cutoff
of 43 Hz, then you could NOT do it with THAT driver, you'd need
a different one, one with a different combination of moving mass, DC
resistance and Bl product. And that driver would be, for the maximum
possible efficiency, 3 dB more efficient than the driver for the
sealed maximum efficiency system (which an AR3 is pretty close to).

--
+--------------------------------+
+ Dick Pierce |
+ Professional Audio Development |
+--------------------------------+

[Audio_Empire]

In article ,
Dick Pierce wrote:

Howard Davis wrote:
"Dick Pierce" wrote in message
A classic example at the theoretical level is the hard-
constrained relation between enclosure volume, cutoff
frequency and in-band efficiency. For a given enclosure
type, the product of these three parameter CANNOT EVER
exceed a constant (well, to be more precise, it's
the product opf the enclosure size, efficiency and the
cube of the cutoff frequency).

Which is why the sealed box (acoustic suspension) design,
as in the AR3a, is inefficient.

Since this thread has migrated off into a tangent, no harm in
letting it wander a bit more. I saw a teachable moment.

It's a little difficult to parse your sentence here, but it
has shades of a very common misconception when it comes to
speakers.

As stated, one implication of the statement,

"Which is why the sealed box (acoustic suspension) design,
as in the AR3a, is inefficient."

is that putting a driver in a sealed box makes it inefficient,
or, conversely, turning a sealed box into a reflex makes it
MORE efficient.

Both of these statements are technically wrong. For all direct-
radiator systems, it's not the box that determines the
efficiency, it's the driver. The system's efficiency (that is,
it's efficiency in its passband) is determined by the relation
of a small handful of parameters unique to the driver itself:
moving mass, DC resistance of the voice coil, and the Bl product
of the magnet/voice coil system. Take any given driver and put
it in pretty much any direct-radiator enclosure, and the passband
efficiency of the system DOES NOT CHANGE.

Now, that may seem contradictory to my earlier statement, but it
is, in fact, completely consistent with it.

Let's take the AR3 you cited as an example. It's about 1.4 cubic
feet in volume and has a system resonance of about 43 Hz, and a Q
at resonance of about 1.2 or so. In order to achieve that
low a resonance in an enclosure that small requires that the
moving mass of the cone has to a certain value. Now, to achieve
the Q at resonance desired, it has to have a specific combination
of Bl product and voice coil resistance (since it's the electrical
damping that dominates the total system damping).

Another way is to pad the higher frequencies down to near the level of
the rolling-off low frequencies so that the response is flatter over a
broader range. I always thought that was the reason that AR3's were low
in efficiency. Of course it IS true that when you don't use the back
wave of a speaker to reinforce the front wave (essentially dissipating
it as heat) it does lower the acoustic output of the driver, but I don't
think it's by much. In the AR, the air trapped in the sealed enclosure
acted as the suspension for the woofer and allowed it to be more
compliant (hence the term Acoustic Suspension).

Now, look at what I said a little farther up: the passband
efficiency of the driver is determined by its moving mass,
DC resistance and Bl product.

So, to achieve the system response AR wanted, they HAD to use
a driver with a specific mass, DC resistance and Bl product.

Thus, the system design parameters dictated the driver efficiency
needed for the enclosure. Choosing a driver with higher efficiency
could have been accomplished a number of ways:

1. Reduce the moving mass of the driver:
Yes, the efficiency would have gone up, to be sure, but so
too would the system resonance, and the system Q would go
down: you'd no longer have the cutoff frequency and low-
frequency response of an AR3,

2. Reduce the DC resistance of the voice coil:
This, too, would have increased efficiency, but with several
side effects and complications of its own.

a. Reducing the DC resistance itself (if possible, see the next
point would have resulted in a reduction in the system's
electrical Q, with the result the the system Q would no
longer by 1.2, but would have been less, raising the
cutoff frequency of the system,

b. HOW you reduce the DC resistance is the real trick: you
have some severe limitations as to how to go about this:

i Use a larger gauge wi that has two effects: one,
it means fewer winding per inch, which results in less
wire in the magnetic field (l), which means lower Bl product
(see #3 below) and thus less efficiency, and two, it
means the voice coil outer diameter is greater, which
requires a wider magnetic gap. A wider magnetic gap
reduces the field density (B) and thus a lower Bl
product

ii Use a shorter winding, less overhang:
Means you reduce the linear excursion of the woofer,

c. The DC resistance of an AR3 is already pretty low, around
3 ohms. Reducing it further would have made a number of
contemporary amplifiers (notably the AR amplifier, ironically),
VERY unhappy.

3. Increase the BL product of the driver:
Well, a bigger magnet might seem the way to go, but it's actually
the fact that it's the low-carbon soft steel used for the front
plate that sets the limit the the gap is run pretty much at or
near saturation: a bigger magnet simply ends up increasing the
leakage elsewhere without increasing the flux density at all.
So that's not a choice.

You could increase the length of the voice coil winding in the gap,
which you could do by either decreasing the wire gauge (smaller
diameter) or adding more layers: both of these result in MORE
DC resistance, reducing the efficiency there.

Or, you could increase the width of the gap with a thicker front
plate and more magnet to compensate to get back up to saturation.
But, remember, increasing the Bl product also reduces electrical Q,
overdamping the system and raising the cutoff frequency. Also, to
then achieve the same linear excursion, you'd have to increase
with length of the voice coil, increasing the DC resistance and
thus reducing the the efficiency there.

So, if you want a 1.5 cubic foot sealed system with a cutoff of
43 Hz and a Q of 1.2, the only way to do it is with a driver of
such-and-such efficiency.

If you wanted to do a reflex system in 1.5 cubic feet with a cutoff
of 43 Hz, then you could NOT do it with THAT driver, you'd need
a different one, one with a different combination of moving mass, DC
resistance and Bl product. And that driver would be, for the maximum
possible efficiency, 3 dB more efficient than the driver for the
sealed maximum efficiency system (which an AR3 is pretty close to).

Thank you. Very informative.

[Dick Pierce[_2_]]

Audio_Empire wrote:
Dick Pierce wrote:
Let's take the AR3 you cited as an example. It's about 1.4 cubic
feet in volume

Sorry, that's atypo: should be 1.5 cubic feet, or about 43 liters,
0.043 m^3.

and has a system resonance of about 43 Hz, and a Q
at resonance of about 1.2 or so. In order to achieve that
low a resonance in an enclosure that small requires that the
moving mass of the cone has to a certain value. Now, to achieve
the Q at resonance desired, it has to have a specific combination
of Bl product and voice coil resistance (since it's the electrical
damping that dominates the total system damping).

Another way is to pad the higher frequencies down to near the level of
the rolling-off low frequencies so that the response is flatter over a
broader range.

That's not done for several reasons, mostly because it's
probably the least efficient, most expensive way to do it.
The reason is that if you have too high an efficiency a
driver to begin with, one that results in to low a system Q
(overdamped), it means your driver Bl product is too high
and/or your DC resistance is too low. Put a smaller magnet
on the driver: lower the B and thus the BL, and you achieve
the same results only at a lower cost and you're not
dissipating the bulk of the input power heating the resistive
part of your padding network. If you really DO have too high
and efficiency, just put a resistor in series: That WILL "pad"
the high frequencies: but you're ending up paying for the
resistor and for the extra magnet you no longer need.

It's a bad idea, that's why nearly no one does it.

(secondarily, consider the frequency-dependent impedance
presented by the woofer: that leads to a non-linear
"padding": as the frequency rises and thus the woofer's
impedance rises, the pad becomes less effective, and it
leads to a rising response, something most woofers or
woofer midranges really don't need.)

I always thought that was the reason that AR3's were low
in efficiency.

No, the reasons I cited are sufficient, in and of themselves
to account for the system's efficiency.

And I'm siting here looking at the AR3 crossover schematic,
there most assuredly is not such pad in the system. And,
further, because of the way the midrange and tweeter in
the system was designed, the woofer, unfortunately,
ended up being the highest efficiency driver in the system,
which is what lead to the roughly -1dB/octave dropping response
in the system.

Of course it IS true that when you don't use the back
wave of a speaker to reinforce the front wave

No, it is NOT true.

(essentially dissipating it as heat)

It only dissipates it as heat if the major portion of
the radiation impedance is resistive. Most assuredly,
at those frequencies, the radiation impedance of the
enclosure is anything but.

Try this experiment: put a thermometer inside an acoustic
suspension speaker. Play it VERY loud for an hour, and
check the temperature. Yes, it will be higher, but only
because the voice coil and magnet structure got hot through
simple ohmic heating of the voice coil. There will be little
or no excess heating due to the "back wave" of the speaker.

(to be honest, it's a damned hard experiment to do.
An AR3 had an efficiency of perhaps 1/4%. That means
if you played it for an hour at an average power of
10 watts, while the total energy input would be
roughly 36 kJoules, 36.91 kJoules get turned into heat
by the voice coil, but only 0.09 kJoules actually
ends up being sound.)

it does lower the acoustic output of the driver,

No, it does not.

but I don't think it's by much.

It lowers it by nothing.

This, again, is a common misconception. The efficiency of a
vented box (bass reflex, if you prefer) is NOT higher because
the back wave contributes to the output, it's higher because
the efficiency of the driver itself is higher. The back wave
DOES NOT, in and off itself, contribute anything to the
broadband efficiency of the system.

Just as in the case of an acoustic suspension system, the
physical driver parameters optimized to achieve the proper
alignment of a vented system naturally lead to a driver
that is more efficient than a driver optimized for a sealed
box of the same enclosure size and cutoff frequency.

If you, in fact, examine the relative contributions to the
total acoustic output of a vented system of the woofer and
vent (port), you find something very interesting happening.
Once you get away from the enclosure/vent resonant frequency,
the output from the vent is insignificant compared to the
direct output of the woofer: the woofer is, in essence,
the sole radiating component of the system.

Now at and around the vent resonant frequency, exactly the
opposite is happening: the direct output from the woofer is
insignificant compared to that of the port: the port, in
essence, is the sole radiating component of the system.

To paraphrase Richard Small (of Thiele-Small fame), the
acoustic output of the port does NOT augment the direct
output of the driver, it SUPPLANTS (that is, replaces)
the direct output of the driver.

This can be shown empirically in two ways.

1. Using a tunable sine-wave oscillator, slowly sweep the
frequency from below the system's cutoff frequency
through the port/enclosure resonance and into the midband,
and observe the excursion of the cone. At the port/enclosure
resonant frequency, you can clearly see the excursion of the
come reduce to a minimum, increasing again as you tune above
and below that frequency.

At the same time, observe (feel, or put a cotton ball in the
port) the port output: you will see it at its maximum at the
same frequency the excursion of the woofer is at a minimum.

2. Find a plug that will fit snugly in the port. Measure the
broadband efficiency of the system with the port unplugged
and plugged. They will be the same.

The back wave IS NOT reinforcing the front wave: over a fairly
narrow band around the enclosure/port resonance, it is
REPLACING the output of the woofer.

In the AR, the air trapped in the sealed enclosure acted as
the suspension for the woofer and allowed it to be more
compliant (hence the term Acoustic Suspension).

No, that's not what's going on.

The mechanical suspension of the driver HAS to be significantly
higher (generally, by at least a factor of 2-3 times) in order
for the so-called acoustic suspension principle to work.

The idea is that it's easier to get both a more linear compliance
AND a more consistent compliance if you make the stiffness of
the air in a sealed box the dominant stiffness of the system
(stiffness simply being the reciprocal of compliance).

It's difficult (and certainly was more so way back when) to
achieve a linear suspension through purely mechanical means.
But the linearity of the compression of the air in a fixed
volume is determined by thermodynamics, thus dependent only
upon the volume of the enclosure and the thermodynamic properties
of a diatomic gas (air, being something like 78% nitrogen, N2,
and 21% oxygen, O2, is almost a perfect diatomic gas, and
is at a density and temperature where it performs as essentially
an ideal gas). Make the effective acoustic stiffness of the
enclosure much higher than that of the mechanical suspension
(that's the same as saying make the compliance of the enclosure
much less than that of the suspension), and the linearity of
the total system stiffness (compliance) is determined by the
air in the enclosure, not the suspension.

And one of the most difficult parameters to control in
manufacturing is the suspension compliance. Even in this day
and age, variations of +-30% in suspension compliance is
quite typical for very high-quality drivers. That leads
to a difference of about +-14% in free-air resonance.

Now, take that same range of compliances and put it in a box
where the box compliance is 1/4 that of the suspension, and
now that +-30% variance in driver compliance is reduced to
a +-10% variance in system compliance.

And the irony is, compliance only matters below the system
resonance: above that, it's the mass and linearity of the voice
coil that's in charge.

--
+--------------------------------+
+ Dick Pierce |
+ Professional Audio Development |
+--------------------------------+

[Howard Davis[_2_]]

"Dick Pierce" wrote in message
...
Howard Davis wrote:
"Dick Pierce" wrote in message
A classic example at the theoretical level is the hard-
constrained relation between enclosure volume, cutoff
frequency and in-band efficiency. For a given enclosure
type, the product of these three parameter CANNOT EVER
exceed a constant (well, to be more precise, it's
the product opf the enclosure size, efficiency and the
cube of the cutoff frequency).

Which is why the sealed box (acoustic suspension) design, as in the AR3a,
is inefficient.

Since this thread has migrated off into a tangent, no harm in
letting it wander a bit more. I saw a teachable moment.

It's a little difficult to parse your sentence here, but it
has shades of a very common misconception when it comes to
speakers.

As stated, one implication of the statement,

"Which is why the sealed box (acoustic suspension) design,
as in the AR3a, is inefficient."

is that putting a driver in a sealed box makes it inefficient,
or, conversely, turning a sealed box into a reflex makes it
MORE efficient.

Both of these statements are technically wrong. For all direct-
radiator systems, it's not the box that determines the
efficiency, it's the driver. The system's efficiency (that is,
it's efficiency in its passband) is determined by the relation
of a small handful of parameters unique to the driver itself:
moving mass, DC resistance of the voice coil, and the Bl product
of the magnet/voice coil system. Take any given driver and put
it in pretty much any direct-radiator enclosure, and the passband
efficiency of the system DOES NOT CHANGE.

Now, that may seem contradictory to my earlier statement, but it
is, in fact, completely consistent with it.

Let's take the AR3 you cited as an example. It's about 1.4 cubic
feet in volume and has a system resonance of about 43 Hz, and a Q
at resonance of about 1.2 or so. In order to achieve that
low a resonance in an enclosure that small requires that the
moving mass of the cone has to a certain value. Now, to achieve
the Q at resonance desired, it has to have a specific combination
of Bl product and voice coil resistance (since it's the electrical
damping that dominates the total system damping).

Now, look at what I said a little farther up: the passband
efficiency of the driver is determined by its moving mass,
DC resistance and Bl product.

So, to achieve the system response AR wanted, they HAD to use
a driver with a specific mass, DC resistance and Bl product.

Thus, the system design parameters dictated the driver efficiency
needed for the enclosure. Choosing a driver with higher efficiency
could have been accomplished a number of ways:

1. Reduce the moving mass of the driver:
Yes, the efficiency would have gone up, to be sure, but so
too would the system resonance, and the system Q would go
down: you'd no longer have the cutoff frequency and low-
frequency response of an AR3,

2. Reduce the DC resistance of the voice coil:
This, too, would have increased efficiency, but with several
side effects and complications of its own.

a. Reducing the DC resistance itself (if possible, see the next
point would have resulted in a reduction in the system's
electrical Q, with the result the the system Q would no
longer by 1.2, but would have been less, raising the
cutoff frequency of the system,

b. HOW you reduce the DC resistance is the real trick: you
have some severe limitations as to how to go about this:

i Use a larger gauge wi that has two effects: one,
it means fewer winding per inch, which results in less
wire in the magnetic field (l), which means lower Bl product
(see #3 below) and thus less efficiency, and two, it
means the voice coil outer diameter is greater, which
requires a wider magnetic gap. A wider magnetic gap
reduces the field density (B) and thus a lower Bl
product

ii Use a shorter winding, less overhang:
Means you reduce the linear excursion of the woofer,

c. The DC resistance of an AR3 is already pretty low, around
3 ohms. Reducing it further would have made a number of
contemporary amplifiers (notably the AR amplifier, ironically),
VERY unhappy.

3. Increase the BL product of the driver:
Well, a bigger magnet might seem the way to go, but it's actually
the fact that it's the low-carbon soft steel used for the front
plate that sets the limit the the gap is run pretty much at or
near saturation: a bigger magnet simply ends up increasing the
leakage elsewhere without increasing the flux density at all.
So that's not a choice.

You could increase the length of the voice coil winding in the gap,
which you could do by either decreasing the wire gauge (smaller
diameter) or adding more layers: both of these result in MORE
DC resistance, reducing the efficiency there.

Or, you could increase the width of the gap with a thicker front
plate and more magnet to compensate to get back up to saturation.
But, remember, increasing the Bl product also reduces electrical Q,
overdamping the system and raising the cutoff frequency. Also, to
then achieve the same linear excursion, you'd have to increase
with length of the voice coil, increasing the DC resistance and
thus reducing the the efficiency there.

So, if you want a 1.5 cubic foot sealed system with a cutoff of
43 Hz and a Q of 1.2, the only way to do it is with a driver of
such-and-such efficiency.

If you wanted to do a reflex system in 1.5 cubic feet with a cutoff
of 43 Hz, then you could NOT do it with THAT driver, you'd need
a different one, one with a different combination of moving mass, DC
resistance and Bl product. And that driver would be, for the maximum
possible efficiency, 3 dB more efficient than the driver for the
sealed maximum efficiency system (which an AR3 is pretty close to).

--
+--------------------------------+
+ Dick Pierce |
+ Professional Audio Development |
+--------------------------------+

From the above (thank you!), I take it that claims of greater efficiency for
reflex systems based on the use of the acoustic "back wave" from the speaker
are not valid; that greater efficiency is due to the characteristics of the
driver itself, not the acoustic radiation through the port of the enclosure?

[Dick Pierce[_2_]]

Howard Davis wrote:
"Dick Pierce" wrote in message
From the above (thank you!), I take it that claims of greater efficiency for
reflex systems based on the use of the acoustic "back wave" from the speaker
are not valid; that greater efficiency is due to the characteristics of the
driver itself, not the acoustic radiation through the port of the enclosure?

That is, in essence, correct: the port is najor contributor
to system output when the driver is not, and the driver is
the major contributor to system output when the port is not.

And the port is the major contributor ONLY over a very
narrow band of frequencies, just above the system cutoff
frequency. Above and below that, it's output diminishes
rapidly.

--
+--------------------------------+
+ Dick Pierce |
+ Professional Audio Development |
+--------------------------------+

[Audio_Empire]

In article ,
"Howard Davis" wrote:

From the above (thank you!), I take it that claims of greater efficiency for
reflex systems based on the use of the acoustic "back wave" from the speaker
are not valid; that greater efficiency is due to the characteristics of the
driver itself, not the acoustic radiation through the port of the enclosure?

That's what Mr. Pierce says. I wonder if that applies to folded horns
Like Klipschorns (50% efficient) and Altec-Lansing Model A7 "Voice of
the Theater" speaker systems? I.E. The fact that these are folded horns
has nothing to do with the efficiency of the speakers, and that the same
drivers in, say, a bass-reflex or an infinite baffle of some type might
have the same efficiency?

[Dick Pierce[_2_]]

Audio_Empire wrote:
In article ,
"Howard Davis" wrote:


From the above (thank you!), I take it that claims of greater efficiency for
reflex systems based on the use of the acoustic "back wave" from the speaker
are not valid; that greater efficiency is due to the characteristics of the
driver itself, not the acoustic radiation through the port of the enclosure?

That's what Mr. Pierce says.

No, that's what the physics says. That's what Thiele, Small and
Bensonsay, among many others. I am simply retelling the tale.

I wonder if that applies to folded horns Like Klipschorns (50% efficient)

Well, not quite. YOu still have to account for the
ohmic losses in the voice coil.

and Altec-Lansing Model A7 "Voice of
the Theater" speaker systems? I.E. The fact that these are folded horns
has nothing to do with the efficiency of the speakers,

Well, no, not ocrrect.

Recall back to the beginning of this particular tangent
where I stated, quite clearly:

"For all direct-radiator systems, it's not the box
that determines the efficiency, it's the driver.

The two speakers you nention here are NOT direct radiator
systems. A somewhat different set of constraints apply.

One of the constraints direct-radiator systems operate
under is that they are, in their passband, essentially
omnidirectional. That is, they are evenly distributing
their radiated acoustical power evenly in all directions
(that is part of the definition of "direct radiator").
At higher frequencies, yes, the radiation pattern is
no longer omnidirectional. and there also, the constraint
system is different. All of this discussion about AR3
woofers and bass reflex enclosure is all quite valid
at low frequencies.

Now, with a horn, you have a VERY interesting phenomenon:
the radiation pattern of a horn in its passband is
anything BUT omnidirectional: the power is concentrated
over a much smaller solid angle.

Lets' take a Klipsch corner horn as an example. The very
nature of its design constrains it's radiation pattern
to 1/8 that of a direct radiator. Simply based on that
fact alone, the same power, distributed over 1/8 the solid
angle, gives a 9 dB increase in sound pressure at the
listening position, all other things being equal.

But, also, all things are not equal, because the other
thing the horn does is changes the acoustical load impedance
on the driver, and that change in load impedance contribute
another 3 dB or so to the effective sound pressure level
at the listening position.

So, by itself, you have a large increase in sound pressure
level at the listening position. But you DON'T have a large
increase in radiated acoustical power for the same electrical
input power: that's the definition of "efficiency", the
ratio of output power to input power.

Now, take a driver that itself has an electroacoustic reference
efficiency into a full sphere of, say 2%. In an anechoic space,
1 watt into that speaker will produce a sound pressure level of
92 dB at 1 meter. Put that same speaker flat against a single
wall. At low frequencies, the sound pressure level will increase
by 3 dB. Now, stick it right at the junction of two walls: another
3 dB. Now stick it in a corner, another 3 dB. It seems like,
magically, the speaker has just gained a factor of 8 efficiency,
but, the power into the space has not changed, so the efficiency
has not changed.

That 12 dB increase due to all the factors (constraining the
radiation pattern, different acoustical load) makes a corner
horn a given river SEEM like instead of having an efficiency
of 2%, it has an efficiency of of nearly 30%.

The Voice of the Theater is an escpeically interesting case
for this analysis. Below the cutoff of the horn, which is
fairly high (something like 80 Hz, as I recall), the system has
the efficiency exactly that of the electroacoustic reference
efficiency of the driver, AND it's radiation pattern is quite
assuredly omnidirectional. AS you move ABOVE the horn cutoff
frequency, the efficiency goes up, at the same time the
width of the radiation pattern is being more and more
constricted. At the point of maximum "efficiency," it'sd
about 6 dB more efficient, and the total solid radiation
beamwidth is about 1/4 that of omnidirectional.

The problem with this analysis is that it through horn
afficianados, and especially Kipschophiles, into an
uncontrollabel religious apoplexy, as they rend their sacred
garments upon being confronted with such a heretical view.

Yet, while they admit the factuality of the radiation pattern
they refuse to connect it with the increase in sound pressure
level. Paul would not have it this way.

and that the same
drivers in, say, a bass-reflex or an infinite baffle of some type might
have the same efficiency?

Below the cutoff of the horn, and where the systems are radiating
as direct radiators, yes, they do. Above that, where the radiation
pattern is contricted, they are more SENSITIVE, i.e., they have
a higher acoustic sound pressure level on the principle axis,
but that's NOT the same as saying they are more efficient.

--
+--------------------------------+
+ Dick Pierce |
+ Professional Audio Development |
+--------------------------------+

[Andrew Haley]

Audio_Empire wrote:

Most people don't realize that too small of an amplifier for a given
speaker is generally much more prone to damage the drivers than is a too
big of an amplifier. Small amp clips a lot exceeding the duty cycle of
the voice coils which heat up and warp the coil form, or worse, burn-out
the coil.

This is pretty much an urban legend which persists despite Rane's
famous Note 128, which noted back in 1991 "Sure, clipping is producing
extra harmonics but they never approach the levels of the amplified
high frequency source signals." As they noted, even a 100Hz
full-power square wave doesn't overdrive a reasonably-sized tweeter.

Andrew.

[Howard Davis[_2_]]

"Dick Pierce" wrote in message
...
Audio_Empire wrote:
In article ,
"Howard Davis" wrote:

snip

+--------------------------------+
+ Dick Pierce |
+ Professional Audio Development |
+--------------------------------+

Thank you!
Your posts here are enjoyable and very informative.

[Audio_Empire]

In article ,
Andrew Haley wrote:

Audio_Empire wrote:

Most people don't realize that too small of an amplifier for a given
speaker is generally much more prone to damage the drivers than is a too
big of an amplifier. Small amp clips a lot exceeding the duty cycle of
the voice coils which heat up and warp the coil form, or worse, burn-out
the coil.

This is pretty much an urban legend which persists despite Rane's
famous Note 128, which noted back in 1991 "Sure, clipping is producing
extra harmonics but they never approach the levels of the amplified
high frequency source signals." As they noted, even a 100Hz
full-power square wave doesn't overdrive a reasonably-sized tweeter.

Andrew.

But a continuously clipping 10KHz signal can kill a tweeter. I've seen
the results. Mostly burned-out tweeters come from "rockers" who listen
at high volume levels with amps that too small. Take overproduced and
over-compressed electronic rock-n-roll, play it a lease-breaking levels
on inadequate, or poorly designed amplifiers, and one has a recipe for
blown tweeters.

Another source of blown tweeters, is a highly reactive speaker load
causing marginal solid-state amplifiers to go into ultra-sonic
oscillation. While not a problem any more, back in the late sixties
through much of the seventies, there were a number of amps that did this
(Accusound solid state amp, anybody? Especially in conjunction with some
early attempts at fancy speaker cables - the woven flat-ribbon type
come to mind. They would blow tweeters and ultimately the amp itself.

[Dick Pierce[_2_]]

Audio_Empire wrote:
In article ,
Andrew Haley wrote:


Audio_Empire wrote:

Most people don't realize that too small of an amplifier for a given
speaker is generally much more prone to damage the drivers than is a
too
big of an amplifier. Small amp clips a lot exceeding the duty cycle of
the voice coils which heat up and warp the coil form, or worse,
burn-out
the coil.

This is pretty much an urban legend which persists despite Rane's
famous Note 128, which noted back in 1991 "Sure, clipping is producing
extra harmonics but they never approach the levels of the amplified
high frequency source signals." As they noted, even a 100Hz
full-power square wave doesn't overdrive a reasonably-sized tweeter.

Andrew.


But a continuously clipping 10KHz signal can kill a tweeter. I've seen
the results. Mostly burned-out tweeters come from "rockers" who listen
at high volume levels with amps that too small. Take overproduced and
over-compressed electronic rock-n-roll, play it a lease-breaking levels
on inadequate, or poorly designed amplifiers, and one has a recipe for
blown tweeters.

Clipping a 10 kHz sine will produce harmonics from 30 kHz on
up. At that point, both the increased inductive reactance of
the tweeter and ten increased resistance resulting in a
higher impedance at ultrasonic frequencies (compared to 10 kHz
will prevent much of that signal from getting through.

But, in fact, NONE of the harmonics resulting from clipping
a 10 kHz signal will destroy a tweeter, NONE of them. That's
because the tweeter itself would already have been destroyed
by the non-clipped 10 kHz signal well below clipping.
50 watts of completely undistorted 10 kHz will kill most
tweeters in a heartbeat.


--
+--------------------------------+
+ Dick Pierce |
+ Professional Audio Development |
+--------------------------------+

[Arny Krueger]

"Howard Davis" wrote in message
...

It is unreasonable to expect that expensive high-performance speakers like
these will not become defective within 20 years if not abused?

I have a pair of Boston Acoustic CR-9 speakers that must be close to 20
years old and still sound very fine.

So I don't know about expensive high-performance speakers, but some
mid-priced speakers seem to hang in there pretty well. ;-)

[Arny Krueger]

"Audio_Empire" wrote in message
...
In article ,

But a continuously clipping 10KHz signal can kill a tweeter.

Since the 10 KHz fundamental is in the frequency range of most tweeters, it
need not be clipped to kill!

In fact, what kills speakers is simply too much power. There are many ways
to achieve this, but IME dance parties and/or excess use of preferred
intoxicants seem to facilitate the process.

Since even $80 receievers have 100 wpc power amps, there is usually more
than enough power around in most home audio systems to damage many speakers
if the system is abused.

[isw]

In article ,
"Arny Krueger" wrote:

"Audio_Empire" wrote in message
...
In article ,

But a continuously clipping 10KHz signal can kill a tweeter.

Since the 10 KHz fundamental is in the frequency range of most tweeters, it
need not be clipped to kill!

In fact, what kills speakers is simply too much power. There are many ways
to achieve this, but IME dance parties and/or excess use of preferred
intoxicants seem to facilitate the process.

Since even $80 receievers have 100 wpc power amps, there is usually more
than enough power around in most home audio systems to damage many speakers
if the system is abused.

(Mumble) years ago, I toasted the woofer voice coil in a Klipschorn when
one output device shorted in a homebrew 70 watt amp I had hooked to it--
but *man* was the hum loud while it lasted! I wrote to the factory,
explaining what had happened and inquiring about the cost of a
replacement. Paul Klipsch, being Paul Klipsch, wrote back saying that
his woofers weren't supposed to do that, and sent me a new one.

Isaac

[Audio_Empire]

In article , isw
wrote:

In article ,
"Arny Krueger" wrote:

"Audio_Empire" wrote in message
...
In article ,

But a continuously clipping 10KHz signal can kill a tweeter.

Since the 10 KHz fundamental is in the frequency range of most tweeters, it
need not be clipped to kill!

In fact, what kills speakers is simply too much power. There are many ways
to achieve this, but IME dance parties and/or excess use of preferred
intoxicants seem to facilitate the process.

Since even $80 receievers have 100 wpc power amps, there is usually more
than enough power around in most home audio systems to damage many speakers
if the system is abused.

(Mumble) years ago, I toasted the woofer voice coil in a Klipschorn when
one output device shorted in a homebrew 70 watt amp I had hooked to it--
but *man* was the hum loud while it lasted! I wrote to the factory,
explaining what had happened and inquiring about the cost of a
replacement. Paul Klipsch, being Paul Klipsch, wrote back saying that
his woofers weren't supposed to do that, and sent me a new one.

Isaac

If you received an answer from Paul Klipsch personally, that wasn't
THAT "many years ago" as Paul Klipsch only died in 2002 at the age of
98. I understand that he was personally involved in the business almost
to the end. Pretty good run, I'd say!

[isw]

In article ,
Audio_Empire wrote:

In article , isw
wrote:

In article ,
"Arny Krueger" wrote:

"Audio_Empire" wrote in message
...
In article ,

But a continuously clipping 10KHz signal can kill a tweeter.

Since the 10 KHz fundamental is in the frequency range of most tweeters,
it
need not be clipped to kill!

In fact, what kills speakers is simply too much power. There are many
ways
to achieve this, but IME dance parties and/or excess use of preferred
intoxicants seem to facilitate the process.

Since even $80 receievers have 100 wpc power amps, there is usually more
than enough power around in most home audio systems to damage many
speakers
if the system is abused.

(Mumble) years ago, I toasted the woofer voice coil in a Klipschorn when
one output device shorted in a homebrew 70 watt amp I had hooked to it--
but *man* was the hum loud while it lasted! I wrote to the factory,
explaining what had happened and inquiring about the cost of a
replacement. Paul Klipsch, being Paul Klipsch, wrote back saying that
his woofers weren't supposed to do that, and sent me a new one.

Isaac

If you received an answer from Paul Klipsch personally, that wasn't
THAT "many years ago" as Paul Klipsch only died in 2002 at the age of
98. I understand that he was personally involved in the business almost
to the end. Pretty good run, I'd say!

I agree. And he was really a character. I grew up in Little Rock, about
a hundred miles from his original operation down in Hope. If you were a
techno-geek, the pilgrimage was nearly obligatory, and he was always a
gracious host to kids a fraction of his age. There was always a lunch
(on him) at the local diner, where he would regale us with stories about
trains (one of his hobbies) or watches (another one). I remember once
when he jumped up, pointed out the window, and said "Look! There goes a
car with the new Timken roller bearings. No more hot boxes!"

The woofer blowout I described happened in about 1970, a few years after
I had graduated and moved away.

Isaac

[Arny Krueger]

"ScottW" wrote in message
...
On Oct 9, 3:39 pm, "Arny Krueger" wrote:
"Howard Davis" wrote in message

...

It is unreasonable to expect that expensive high-performance speakers
like
these will not become defective within 20 years if not abused?

I have a pair of Boston Acoustic CR-9 speakers that must be close to 20
years old and still sound very fine.

So I don't know about expensive high-performance speakers, but some
mid-priced speakers seem to hang in there pretty well. ;-)

My nearly 40 year old Original large Advents are also working like
new.

I did have to refoam the woofer surrounds but I consider that a 20
year maintenance requirement. It's really not hard to do.
More surprisingly...the amp I purchased for them at the same time (a
Sansui AU-6500) still works as well.

My origional Advents were purchased new in the very early 1970s.

By the middle 1980s their foam surrounds were thoroughly gone. I replaced
the woofers with Peerless drivers with appropriate sensisitivity and T/S
parameters.

By that time I had sold them to my brother in law. I last saw them operating
in the early 2000s. The Peerless drivers had rubber surrounds and were
holding strong.