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  #561   Report Post  
Nousaine
 
Posts: n/a
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"Wessel Dirksen" wrote:


"Michael McKelvy" wrote in message
...
"Nousaine" wrote in message
...
"Michael McKelvy"
wrote:

....snip to content......

I don't know why I'd trust anybody that still sells the break-in
mythology. :-)
compensation.

But again, why would I want to trust people who still subscribe to

the
speaker
break-in urban legend?

For the same reason I wouln't write off someone who sells finished

speakers
that tout the fact that they have gold plated terminals, it's about
marketing and doesn't really do any harm. I know your position on

break-in
and my expierience is the same, but it is limited. There is a car

speaker
company's web site I visited that had specs on before and after

break-in
on
their drivers, there was a difference albeit a small one.

I don't have a 'position' on break-in. I've conducted more than one

extensive
experiment testing the hypothesis. It is true that you can 'measure'

changes in
Fs and Vas immediately after a long break-in period when the voice coil

is
still hot. But those changes are 1) off-setting in regard to cabinet

design and
2) return to previous values after a few hours rest.


Fs and Vas are mechanical properties and have no dependance on the
electrical properties of the voicecoil whatsoever. Even if the voicecoil
could theoretically double it's Rdc from overheating (impossible without
damage), the Fs and Vas and therefore Qm would not be affected. But a hot
voicecoil will increase Qe and therefore overall Qt will increase until the
VC cools down.


What you say may be true but the calculation of Vas is dependent on measuring
the impedance curve and Fs and Re and Q does change and so do the calculated
values of Vas. But, and this is the important point is that they fall back to
'fresh' values as the voice coil cools down. It may be true that this
phenomenon may be independent of the latter but the real point is that speakers
DO NOT break in. At best it can be said that they may WARM UP. But because
performance doesn't change why would anyone care?

The ambient temperature can significantly affect Cms where an increase in
temperature increases system compliance and leads to increased Vas and
decreased Fs which in turn increases overal Q. So the weather has a greater
influence on the mechanical properties of a driver than most other factors.


Sure. But that simply says that speakers do not break-in.


Driver break-in is much less of an issue these days mainly because the
industry has for awhile now demanded low assembly line unit to unit
variability and polymer technology has made this possible. Break in, when
present in the driver itself is usually in only in the amount of hysteresis
leading to dicernable differences only when the cone is barely moving.


Meaning when Theil/Small parameters are generally measured :-)


A very common and very audible "break in" phenomena when first taking
speakers home is due to external factors. The ambient temperature changes
from warehouse to car etc and temporarily changes mechanical compliance.
Often a speaker is not stocked in the same orientation as it is used, so
that internal damping materials often shift during the first days of use and
this can be very discernable. Even the re-location from a different
elevation can cause an atmospheric pressure gradient with a sealed midrange
driver leading to a break-in phenomena for a few days until equalibrium has
been reached.


I'm guessing that elevation and storage equibrium is reached within a few
seconds. If you have some more data I'd be glad to hear it.
  #562   Report Post  
Wessel Dirksen
 
Posts: n/a
Default

(Nousaine) wrote in message ...
"Wessel Dirksen"
wrote:


"Michael McKelvy" wrote in message
...
"Nousaine" wrote in message
...
"Michael McKelvy"
wrote:

....snip to content......

I don't know why I'd trust anybody that still sells the break-in
mythology. :-)
compensation.

But again, why would I want to trust people who still subscribe to

the
speaker
break-in urban legend?

For the same reason I wouln't write off someone who sells finished

speakers
that tout the fact that they have gold plated terminals, it's about
marketing and doesn't really do any harm. I know your position on

break-in
and my expierience is the same, but it is limited. There is a car

speaker
company's web site I visited that had specs on before and after

break-in
on
their drivers, there was a difference albeit a small one.

I don't have a 'position' on break-in. I've conducted more than one

extensive
experiment testing the hypothesis. It is true that you can 'measure'

changes in
Fs and Vas immediately after a long break-in period when the voice coil

is
still hot. But those changes are 1) off-setting in regard to cabinet

design and
2) return to previous values after a few hours rest.


Fs and Vas are mechanical properties and have no dependance on the
electrical properties of the voicecoil whatsoever. Even if the voicecoil
could theoretically double it's Rdc from overheating (impossible without
damage), the Fs and Vas and therefore Qm would not be affected. But a hot
voicecoil will increase Qe and therefore overall Qt will increase until the
VC cools down.


What you say may be true but the calculation of Vas is dependent on measuring
the impedance curve and Fs and Re and Q does change and so do the calculated
values of Vas. But, and this is the important point is that they fall back to
'fresh' values as the voice coil cools down. It may be true that this
phenomenon may be independent of the latter but the real point is that speakers
DO NOT break in. At best it can be said that they may WARM UP. But because
performance doesn't change why would anyone care?


Vas is not actually determined from the free air impedance curve since
it is dependant on Cms, Sd and air density, but that is not the issue
here. We, and the others still involved with this issue, are in
agreement here that break in as far the drivers themselves are
concerned is at best an issue of the past. What is of importance is
how the drivers mechanical properties are affected by ambient
conditions of which ambient temperature is most critical. Temperature
related voice coil compression from overheating is a functional matter
that is always relevant.

But the affect of ambient temperature on driver characteristics is not
insignificant! System compliance varies greatly in the cold and can
lead to more than a 10% change in Fs at even 50 deg F. This is why
drivers intended for indoor use are developed, and T/S specifications
are considered representative, at operating temperatures between 20
and 25 deg C. If one leaves the heat off during the day in an
environment with cold winters, this is exactly what is happening.
Speakers tend to sound rather lifeless until first the room, then the
speakers warm up. Polypropylene cones are especially notorious for
extra buckling at higher temperatures. I discovered this myself in
turn to hear from driver developers that they have been struggling
with this for years. A typical warm summer can cause the living room
to heat up to 80 deg F.unless you keep the AC on the whole time. This
affects the sound of speakers, especially FR in polypropylene models.


The ambient temperature can significantly affect Cms where an increase in
temperature increases system compliance and leads to increased Vas and
decreased Fs which in turn increases overal Q. So the weather has a greater
influence on the mechanical properties of a driver than most other factors.


Sure. But that simply says that speakers do not break-in.


Agreed



Driver break-in is much less of an issue these days mainly because the
industry has for awhile now demanded low assembly line unit to unit
variability and polymer technology has made this possible. Break in, when
present in the driver itself is usually in only in the amount of hysteresis
leading to dicernable differences only when the cone is barely moving.


Meaning when Theil/Small parameters are generally measured :-)


A very common and very audible "break in" phenomena when first taking
speakers home is due to external factors. The ambient temperature changes
from warehouse to car etc and temporarily changes mechanical compliance.
Often a speaker is not stocked in the same orientation as it is used, so
that internal damping materials often shift during the first days of use and
this can be very discernable. Even the re-location from a different
elevation can cause an atmospheric pressure gradient with a sealed midrange
driver leading to a break-in phenomena for a few days until equalibrium has
been reached.


I'm guessing that elevation and storage equibrium is reached within a few
seconds. If you have some more data I'd be glad to hear it.


Well I'll tell you a story. A customer of mine awhile back lived in
Redlands, California (elevation +/- 500 ft) and had a cabin at Big
Bear Lake (elevation +/- 6000 ft) that he frequently went to for a few
weeks at a time. He had a pair of one the smaller B&W Nautilus
speakers to first use the now common stiff larger 6" midrange driver
(I don't know the model number). Because he liked these speakers he
took them with him every time he went to his cabin. He noticed that
they sounded quite bad for a few days until they sorted themselves
out. When he contacted me about this, I explained the temperature
thing as a hypothesis, and he went to great lengths to correct for
this. A neighbor turned on the heat at the cabin a day in advance, he
pre-heated the car prior to loading, and he carried them outside
wrapped in a couple of sleeping bags. The problem didn't seem to go
away. We decided to look inside since he was considering mod's anyway.
In one of the speakers, a glob of glue had fallen on the leak hole in
the midrange enclosure. Also inspecting the driver and mounting seal,
it didn't appear that air was going to get out easily. Once this was
removed, the problem went away.

This is a little exceptional perhaps but it proves the point
  #563   Report Post  
Wessel Dirksen
 
Posts: n/a
Default

(Nousaine) wrote in message ...
John Stone
wrote:

in article
, Nousaine at wrote
on 7/31/04 4:26 PM:

Some vendors will match your drivers for specs for an additional fee, I
believe NorthCreek is one of them.

And how do they do that? It's been my experience that often the drivers
marketed to the DIY market seem to be end-of-run, out-of-spec orr OEM

rejected
drivers that may not even have the same parts as listed in the catalog.

That's
OK but they need to be verified not only for T/S parameters but also

frequency
response.

For example I once purchased Dynaudio drivers for a custom powered speaker
system. Not only was the Fs of the woofers a half octave higher than
advertised
they weren't even within 10 Hz of each other. This required significant

design
compensation.


Why do you keep resurrecting this old wives' tale, Tom?


It's not an old wive's tale. It's a given experience. And it's one of the
reasons that I stopped making speakers,other than subwoofers 10 years ago.

Where is your
evidence that today's DIY drivers are end run, OEM rejects, or out-of-spec?


I don't have any evidence that this is the case other than never having bought
a driver from anybody, other than tweeters, that didn't require more
investigation than specifications from the vendor for design purposes.

My present company (SEAS) and my previous company (Vifa/Scan-Speak) would
never allow out of spec drivers to leave the factory-ever. In fact, each
SEAS product is fully tested for Fs, frequency response, and rub/buzz before
it ever leaves the factory. Anything that goes to a product distributor like
Madisound is virtually identical to the same product sold to an OEM.


I think you may both be right. John's perspective may be a bit
positively skewed because he works for Seas who in my experience have
the best unit to unit tolerances in the business. Actually there's
pretty much nothing bad you can say about Seas. Focal seem to be
consistantly inconsistant with the individual units I've had but not
terrible per se, in that the drivers I have had would have still
passed reasonable assembly line tolerances compared to published
spec's. I have to side with Tom on Dynaudio though. I once had two
17W75's (out of +/- 12 units total) with a spec'd Fs and a Qt of 1.1!!
(in comparison to 0.74 with normal Fs and Rdc that represents a
magnetic gap flux down close to 50%) I've had 4 20W-75's before of
which two of them had an Fs of 55 (almost an octave to high) I've
never worked with OEM units from either to know how units from the
same series compare. Haven't used enough Scanspeak woofers to know
about them either. I've seen some loosey goosey Vifa drivers in my day
as well, but I rarely use Vifa woofers anymore so I don't know
anymore. In the early to mid 90's, I found that polymer surrounds of
several Vifa units got severely stiff in just a few years time in both
Southern California and in The Netherlands. Seas drivers don't seem to
have this. Actually, about 6 months ago, I got an old project from
1995 back in my hands that had Seas CA21-RE's in them. Because I write
the T/S parameters on the magnets of every individual driver I happen
to measure, I re-tested this unit and it was still spot on even being
tortured in an aggressive bandpass cabinet.

A little further up in this thread ambient temperature was addressed
as it can certainly affect T/S measurement, so measuring a driver's
parameters in a hot or cold garage is asking for surprizes.
  #565   Report Post  
Philip Meech
 
Posts: n/a
Default

Hi John,
I recently bought the H1224 Drivers from Madisound. Can you shed some
light on how they evolved from
the H 1142? Thanks!

John Stone wrote:

in article , Nousaine at wrote
on 7/31/04 4:26 PM:


Some vendors will match your drivers for specs for an additional fee, I
believe NorthCreek is one of them.


And how do they do that? It's been my experience that often the drivers
marketed to the DIY market seem to be end-of-run, out-of-spec orr OEM rejected
drivers that may not even have the same parts as listed in the catalog. That's
OK but they need to be verified not only for T/S parameters but also frequency
response.

For example I once purchased Dynaudio drivers for a custom powered speaker
system. Not only was the Fs of the woofers a half octave higher than
advertised
they weren't even within 10 Hz of each other. This required significant design
compensation.



Why do you keep resurrecting this old wives' tale, Tom? Where is your
evidence that today's DIY drivers are end run, OEM rejects, or out-of-spec?
My present company (SEAS) and my previous company (Vifa/Scan-Speak) would
never allow out of spec drivers to leave the factory-ever. In fact, each
SEAS product is fully tested for Fs, frequency response, and rub/buzz before
it ever leaves the factory. Anything that goes to a product distributor like
Madisound is virtually identical to the same product sold to an OEM. The
better Danish Sound Technology products are likely the same. While I can't
speak for cheap Chinese drivers and other such stuff, I can say that these 2
Scandinavian companies account for a huge chunk of the DIY driver market.

As for your Dynaudio experience, I'm wondering if your high Fs problem
didn't stem at least partially from using a different measuring voltage than
Dynaudio did. Many measuring systems; e.g., MLSSA , simply don't put enough
low frequency energy into the driver to get the suspension working in a
linear fashion. All surrounds, especially high loss types, have some degree
of hysteresis, and at low measurement levels a driver will exhibit
precisely the problem you describe. At any rate, the point is moot given
that Dynaudio stopped stopped selling to the DIY market years ago. Focal and
Audax are both exiting this market as well.

Regarding DIY systems, I've heard some absolutely fantastic designs; IMO as
good as anything commercially available. But-and this is a big but-it takes
someone with a lot of talent and measurement capability to accomplish this.
My present living room system uses the SEAS Odin kit (designed by Joe
D'Appolitto) coupled to a commercial subwoofer. It sounds very good indeed.





  #566   Report Post  
Nousaine
 
Posts: n/a
Default

(Wessel Dirksen) wrote:



John Stone wrote in message
...
in article
, Nousaine at
wrote
on 8/4/04 7:05 PM:

And the better sounding ones cost a lot more in terms of
cash outlay.

The Thor is around $1500.00. Have you heard it?

No. But John Stone reported on the Seas Odin kits he uses; and after

checking
these on the Madisound website they are actually more expensive than the
excellent PSB Stratus Mini. So is this kit.



Yes, but are you then assuming that the 2 are qualitatively equal? Let's
compare them. The PSB is a 6-1/2 2-way with a Vifa P17WJ 17cm and D19AD
19mm alu dome tweeter.
The Odin is a WTW with 2 6-1/2" SEAS Excel woofers and a 25mm "Millennium"
soft dome tweeter.


At this point John has said enough. This is apples vs. oranges.

If both kits are designed reasonably, based on components, the later
will tear up the former left, right and sideways. This is like
comparing a Saturn to a BMW M5.


Oh for Pete's sake. The finished PSB costs 2/3 of the kit. For an even price
comparison, and if you want to play the driver-count game, you can get a pair
of fully finished Paradigm Studio 60s for $1500 or a pair of Studio 40s for
$1100. Both with full warranties.

Everyone wants to ignore that you aren't going to save money or get
demonstrably better performance, even with a high quality kit, compared to
what's commercially available. Sure there are lots of even more expensive
"high-end" speakers that aren't worth the paper the reviews are printed on ---
so what?
  #567   Report Post  
Nousaine
 
Posts: n/a
Default

(Wessel Dirksen) wrote:



(Nousaine) wrote in message
...
"Wessel Dirksen"
wrote:


"Michael McKelvy" wrote in message
...
"Nousaine" wrote in message
...
"Michael McKelvy"
wrote:

....snip to content......

I don't know why I'd trust anybody that still sells the break-in
mythology. :-)
compensation.

But again, why would I want to trust people who still subscribe to

the
speaker
break-in urban legend?

For the same reason I wouln't write off someone who sells finished

speakers
that tout the fact that they have gold plated terminals, it's about
marketing and doesn't really do any harm. I know your position on

break-in
and my expierience is the same, but it is limited. There is a car

speaker
company's web site I visited that had specs on before and after

break-in
on
their drivers, there was a difference albeit a small one.

I don't have a 'position' on break-in. I've conducted more than one

extensive
experiment testing the hypothesis. It is true that you can 'measure'

changes in
Fs and Vas immediately after a long break-in period when the voice

coil
is
still hot. But those changes are 1) off-setting in regard to cabinet

design and
2) return to previous values after a few hours rest.

Fs and Vas are mechanical properties and have no dependance on the
electrical properties of the voicecoil whatsoever. Even if the voicecoil
could theoretically double it's Rdc from overheating (impossible without
damage), the Fs and Vas and therefore Qm would not be affected. But a hot
voicecoil will increase Qe and therefore overall Qt will increase until

the
VC cools down.


What you say may be true but the calculation of Vas is dependent on

measuring
the impedance curve and Fs and Re and Q does change and so do the

calculated
values of Vas. But, and this is the important point is that they fall back

to
'fresh' values as the voice coil cools down. It may be true that this
phenomenon may be independent of the latter but the real point is that

speakers
DO NOT break in. At best it can be said that they may WARM UP. But because
performance doesn't change why would anyone care?


Vas is not actually determined from the free air impedance curve since
it is dependant on Cms, Sd and air density, but that is not the issue
here. We, and the others still involved with this issue, are in
agreement here that break in as far the drivers themselves are
concerned is at best an issue of the past. What is of importance is
how the drivers mechanical properties are affected by ambient
conditions of which ambient temperature is most critical. Temperature
related voice coil compression from overheating is a functional matter
that is always relevant.

But the affect of ambient temperature on driver characteristics is not
insignificant! System compliance varies greatly in the cold and can
lead to more than a 10% change in Fs at even 50 deg F. This is why
drivers intended for indoor use are developed, and T/S specifications
are considered representative, at operating temperatures between 20
and 25 deg C. If one leaves the heat off during the day in an
environment with cold winters, this is exactly what is happening.
Speakers tend to sound rather lifeless until first the room, then the
speakers warm up. Polypropylene cones are especially notorious for
extra buckling at higher temperatures. I discovered this myself in
turn to hear from driver developers that they have been struggling
with this for years. A typical warm summer can cause the living room
to heat up to 80 deg F.unless you keep the AC on the whole time. This
affects the sound of speakers, especially FR in polypropylene models.


The ambient temperature can significantly affect Cms where an increase in
temperature increases system compliance and leads to increased Vas and
decreased Fs which in turn increases overal Q. So the weather has a

greater
influence on the mechanical properties of a driver than most other

factors.

Sure. But that simply says that speakers do not break-in.


Agreed



Driver break-in is much less of an issue these days mainly because the
industry has for awhile now demanded low assembly line unit to unit
variability and polymer technology has made this possible. Break in, when
present in the driver itself is usually in only in the amount of

hysteresis
leading to dicernable differences only when the cone is barely moving.


Meaning when Theil/Small parameters are generally measured :-)


A very common and very audible "break in" phenomena when first taking
speakers home is due to external factors. The ambient temperature changes
from warehouse to car etc and temporarily changes mechanical compliance.
Often a speaker is not stocked in the same orientation as it is used, so
that internal damping materials often shift during the first days of use

and
this can be very discernable. Even the re-location from a different
elevation can cause an atmospheric pressure gradient with a sealed

midrange
driver leading to a break-in phenomena for a few days until equalibrium

has
been reached.


I'm guessing that elevation and storage equibrium is reached within a few
seconds. If you have some more data I'd be glad to hear it.


Well I'll tell you a story. A customer of mine awhile back lived in
Redlands, California (elevation +/- 500 ft) and had a cabin at Big
Bear Lake (elevation +/- 6000 ft) that he frequently went to for a few
weeks at a time. He had a pair of one the smaller B&W Nautilus
speakers to first use the now common stiff larger 6" midrange driver
(I don't know the model number). Because he liked these speakers he
took them with him every time he went to his cabin. He noticed that
they sounded quite bad for a few days until they sorted themselves
out. When he contacted me about this, I explained the temperature
thing as a hypothesis, and he went to great lengths to correct for
this. A neighbor turned on the heat at the cabin a day in advance, he
pre-heated the car prior to loading, and he carried them outside
wrapped in a couple of sleeping bags. The problem didn't seem to go
away. We decided to look inside since he was considering mod's anyway.
In one of the speakers, a glob of glue had fallen on the leak hole in
the midrange enclosure. Also inspecting the driver and mounting seal,
it didn't appear that air was going to get out easily. Once this was
removed, the problem went away.

This is a little exceptional perhaps but it proves the point


Actually it doesn't seem relevant to your point. It seems that you just
discovered an operating flaw if anything. The "problem" was exactly what? The
speakers didn't sound good for a few days but then started sounding good when
you removed the plugged hole? None of this seems relevant to ambient conditions
or elevation. Forgive me if I'm missing something here.
  #568   Report Post  
Nousaine
 
Posts: n/a
Default

(Wessel Dirksen) wrote:



(Nousaine) wrote in message
...
John Stone
wrote:

in article
, Nousaine at

wrote
on 7/31/04 4:26 PM:

Some vendors will match your drivers for specs for an additional fee, I
believe NorthCreek is one of them.

And how do they do that? It's been my experience that often the drivers
marketed to the DIY market seem to be end-of-run, out-of-spec orr OEM

rejected
drivers that may not even have the same parts as listed in the catalog.

That's
OK but they need to be verified not only for T/S parameters but also

frequency
response.

For example I once purchased Dynaudio drivers for a custom powered

speaker
system. Not only was the Fs of the woofers a half octave higher than
advertised
they weren't even within 10 Hz of each other. This required significant

design
compensation.

Why do you keep resurrecting this old wives' tale, Tom?


It's not an old wive's tale. It's a given experience. And it's one of the
reasons that I stopped making speakers,other than subwoofers 10 years ago.

Where is your
evidence that today's DIY drivers are end run, OEM rejects, or

out-of-spec?

I don't have any evidence that this is the case other than never having

bought
a driver from anybody, other than tweeters, that didn't require more
investigation than specifications from the vendor for design purposes.

My present company (SEAS) and my previous company (Vifa/Scan-Speak) would
never allow out of spec drivers to leave the factory-ever. In fact, each
SEAS product is fully tested for Fs, frequency response, and rub/buzz

before
it ever leaves the factory. Anything that goes to a product distributor

like
Madisound is virtually identical to the same product sold to an OEM.


I think you may both be right. John's perspective may be a bit
positively skewed because he works for Seas who in my experience have
the best unit to unit tolerances in the business. Actually there's
pretty much nothing bad you can say about Seas. Focal seem to be
consistantly inconsistant with the individual units I've had but not
terrible per se, in that the drivers I have had would have still
passed reasonable assembly line tolerances compared to published
spec's. I have to side with Tom on Dynaudio though. I once had two
17W75's (out of +/- 12 units total) with a spec'd Fs and a Qt of 1.1!!
(in comparison to 0.74 with normal Fs and Rdc that represents a
magnetic gap flux down close to 50%) I've had 4 20W-75's before of
which two of them had an Fs of 55 (almost an octave to high) I've
never worked with OEM units from either to know how units from the
same series compare. Haven't used enough Scanspeak woofers to know
about them either. I've seen some loosey goosey Vifa drivers in my day
as well, but I rarely use Vifa woofers anymore so I don't know
anymore. In the early to mid 90's, I found that polymer surrounds of
several Vifa units got severely stiff in just a few years time in both
Southern California and in The Netherlands. Seas drivers don't seem to
have this. Actually, about 6 months ago, I got an old project from
1995 back in my hands that had Seas CA21-RE's in them. Because I write
the T/S parameters on the magnets of every individual driver I happen
to measure, I re-tested this unit and it was still spot on even being
tortured in an aggressive bandpass cabinet.

A little further up in this thread ambient temperature was addressed
as it can certainly affect T/S measurement, so measuring a driver's
parameters in a hot or cold garage is asking for surprizes.


Actually I'll accpet what Mr Stone says about the drivers his company makes
although he never did quantify what he meant by 'virtually' identical to OEM
products :-)

And it's true that my first hand experience with drivers other than woofers has
been limited in the past few years. For those I employ DUMAX which is capable
of measuring parameters (including compliance and BL) over a range of
excursion.

It is quite typical for rest-position measurements to differ quite
significantly from manufacturers specifications. The latter may either be
estimated from the parts values or measured with nearly no movement of the cone
(as originally specified by Small). That's all fine but a speaker is seldom
used under the latter conditions.

The Theile/Small parameters were originally developed so that engineers could
use commonly available test instruments and develop a set of measurements to
aid in design. That was the beauty of them.

Today we have DUMAX and Klippel measurements that take into account
non-linearities of the speaker systems.

I'm quite encouraged that manufacturers are now making speakers specifically
for the DIY market. My experience with KEF and Dynaudio drivers (like you
describe above) led me to believe that the DIY market may have been fed
products that that either failed to meet OEM specifications OR were over-runs
of OEM lots that may not even have the same parts that may have been specified
in the catalog.

I may have been in error in that regard and/or perhaps manufacturing techniques
(both gluing up speaker products AND in the parts manufacture) have improved so
that making the same speaker twice in a row is easier.

Although I think that many people think I'm dumping on DIY projects. That's far
from the case. But I see no harm in divulging to enthusiasts up front that they
are not likely to save money or get demonstrably better performance than they
will get by hard shopping.
  #570   Report Post  
Wessel Dirksen
 
Posts: n/a
Default

(Nousaine) wrote in message ...
(Wessel Dirksen) wrote:



(Nousaine) wrote in message
...
John Stone
wrote:

in article
, Nousaine at

wrote
on 7/31/04 4:26 PM:

Some vendors will match your drivers for specs for an additional fee, I
believe NorthCreek is one of them.

And how do they do that? It's been my experience that often the drivers
marketed to the DIY market seem to be end-of-run, out-of-spec orr OEM

rejected
drivers that may not even have the same parts as listed in the catalog.

That's
OK but they need to be verified not only for T/S parameters but also

frequency
response.

For example I once purchased Dynaudio drivers for a custom powered

speaker
system. Not only was the Fs of the woofers a half octave higher than
advertised
they weren't even within 10 Hz of each other. This required significant

design
compensation.

Why do you keep resurrecting this old wives' tale, Tom?

It's not an old wive's tale. It's a given experience. And it's one of the
reasons that I stopped making speakers,other than subwoofers 10 years ago.

Where is your
evidence that today's DIY drivers are end run, OEM rejects, or

out-of-spec?

I don't have any evidence that this is the case other than never having

bought
a driver from anybody, other than tweeters, that didn't require more
investigation than specifications from the vendor for design purposes.

My present company (SEAS) and my previous company (Vifa/Scan-Speak) would
never allow out of spec drivers to leave the factory-ever. In fact, each
SEAS product is fully tested for Fs, frequency response, and rub/buzz

before
it ever leaves the factory. Anything that goes to a product distributor

like
Madisound is virtually identical to the same product sold to an OEM.


I think you may both be right. John's perspective may be a bit
positively skewed because he works for Seas who in my experience have
the best unit to unit tolerances in the business. Actually there's
pretty much nothing bad you can say about Seas. Focal seem to be
consistantly inconsistant with the individual units I've had but not
terrible per se, in that the drivers I have had would have still
passed reasonable assembly line tolerances compared to published
spec's. I have to side with Tom on Dynaudio though. I once had two
17W75's (out of +/- 12 units total) with a spec'd Fs and a Qt of 1.1!!
(in comparison to 0.74 with normal Fs and Rdc that represents a
magnetic gap flux down close to 50%) I've had 4 20W-75's before of
which two of them had an Fs of 55 (almost an octave to high) I've
never worked with OEM units from either to know how units from the
same series compare. Haven't used enough Scanspeak woofers to know
about them either. I've seen some loosey goosey Vifa drivers in my day
as well, but I rarely use Vifa woofers anymore so I don't know
anymore. In the early to mid 90's, I found that polymer surrounds of
several Vifa units got severely stiff in just a few years time in both
Southern California and in The Netherlands. Seas drivers don't seem to
have this. Actually, about 6 months ago, I got an old project from
1995 back in my hands that had Seas CA21-RE's in them. Because I write
the T/S parameters on the magnets of every individual driver I happen
to measure, I re-tested this unit and it was still spot on even being
tortured in an aggressive bandpass cabinet.

A little further up in this thread ambient temperature was addressed
as it can certainly affect T/S measurement, so measuring a driver's
parameters in a hot or cold garage is asking for surprizes.


Actually I'll accpet what Mr Stone says about the drivers his company makes
although he never did quantify what he meant by 'virtually' identical to OEM
products :-)

And it's true that my first hand experience with drivers other than woofers has
been limited in the past few years. For those I employ DUMAX which is capable
of measuring parameters (including compliance and BL) over a range of
excursion.

It is quite typical for rest-position measurements to differ quite
significantly from manufacturers specifications. The latter may either be
estimated from the parts values or measured with nearly no movement of the cone
(as originally specified by Small). That's all fine but a speaker is seldom
used under the latter conditions.


T/S parameters should always be tested at least in the neigborhood of
1/2 Xmax. Earlier we discussed hysteresis, so did John Stone, there
may be some break in there. I bang on 'em when I do T/S. Almost full
x-max, why not? It is a single sided hysteresis profile these days. I
also tend to run em in anyway before measurement. With most it makes
no difference at all. Tweeters are different, they do break in but
ussualy within 30 minutes or so with high pass filtered pink noise.

The Theile/Small parameters were originally developed so that engineers could
use commonly available test instruments and develop a set of measurements to
aid in design. That was the beauty of them.

Today we have DUMAX and Klippel measurements that take into account
non-linearities of the speaker systems.

I'm quite encouraged that manufacturers are now making speakers specifically
for the DIY market. My experience with KEF and Dynaudio drivers (like you
describe above) led me to believe that the DIY market may have been fed
products that that either failed to meet OEM specifications OR were over-runs
of OEM lots that may not even have the same parts that may have been specified
in the catalog.


I'll tell you what else. I've had Dynaudio units with suspiciously too
many stickers on them, I never considered what you are saying. Also, I
contacted Dynaudio about the 4 20W-75's I had because I was
considering +/- bulk stocking them (for me that means 10 - 20). This
is in +/- 1994. And the response was: Our Esotec line is build to such
high standards and tolerances that our research has shown that there
is no need to measure them on the assembly line. Upon which he
dismissed my results as user error and did mention 30 hours of break
in. The woofers were very stable though, they stayed at 55 hz after
weeks of constant break in. Although the 20W-75's were very good, this
didn't take well with me.

I may have been in error in that regard and/or perhaps manufacturing techniques
(both gluing up speaker products AND in the parts manufacture) have improved so
that making the same speaker twice in a row is easier.

Although I think that many people think I'm dumping on DIY projects. That's far
from the case. But I see no harm in divulging to enthusiasts up front that they
are not likely to save money or get demonstrably better performance than they
will get by hard shopping.



  #572   Report Post  
Wessel Dirksen
 
Posts: n/a
Default

"Nousaine" wrote in message
...
(Wessel Dirksen) wrote:



(Nousaine) wrote in message
...
"Wessel Dirksen"
wrote:


"Michael McKelvy" wrote in message
...
"Nousaine" wrote in message
...
"Michael McKelvy"
wrote:

....snip to content......

I don't know why I'd trust anybody that still sells the

break-in
mythology. :-)
compensation.

But again, why would I want to trust people who still subscribe

to
the
speaker
break-in urban legend?

For the same reason I wouln't write off someone who sells

finished
speakers
that tout the fact that they have gold plated terminals, it's

about
marketing and doesn't really do any harm. I know your position

on
break-in
and my expierience is the same, but it is limited. There is a

car
speaker
company's web site I visited that had specs on before and after
break-in
on
their drivers, there was a difference albeit a small one.

I don't have a 'position' on break-in. I've conducted more than

one
extensive
experiment testing the hypothesis. It is true that you can

'measure'
changes in
Fs and Vas immediately after a long break-in period when the voice

coil
is
still hot. But those changes are 1) off-setting in regard to

cabinet
design and
2) return to previous values after a few hours rest.

Fs and Vas are mechanical properties and have no dependance on the
electrical properties of the voicecoil whatsoever. Even if the

voicecoil
could theoretically double it's Rdc from overheating (impossible

without
damage), the Fs and Vas and therefore Qm would not be affected. But a

hot
voicecoil will increase Qe and therefore overall Qt will increase

until
the
VC cools down.

What you say may be true but the calculation of Vas is dependent on

measuring
the impedance curve and Fs and Re and Q does change and so do the

calculated
values of Vas. But, and this is the important point is that they fall

back
to
'fresh' values as the voice coil cools down. It may be true that this
phenomenon may be independent of the latter but the real point is that

speakers
DO NOT break in. At best it can be said that they may WARM UP. But

because
performance doesn't change why would anyone care?


Vas is not actually determined from the free air impedance curve since
it is dependant on Cms, Sd and air density, but that is not the issue
here. We, and the others still involved with this issue, are in
agreement here that break in as far the drivers themselves are
concerned is at best an issue of the past. What is of importance is
how the drivers mechanical properties are affected by ambient
conditions of which ambient temperature is most critical. Temperature
related voice coil compression from overheating is a functional matter
that is always relevant.

But the affect of ambient temperature on driver characteristics is not
insignificant! System compliance varies greatly in the cold and can
lead to more than a 10% change in Fs at even 50 deg F. This is why
drivers intended for indoor use are developed, and T/S specifications
are considered representative, at operating temperatures between 20
and 25 deg C. If one leaves the heat off during the day in an
environment with cold winters, this is exactly what is happening.
Speakers tend to sound rather lifeless until first the room, then the
speakers warm up. Polypropylene cones are especially notorious for
extra buckling at higher temperatures. I discovered this myself in
turn to hear from driver developers that they have been struggling
with this for years. A typical warm summer can cause the living room
to heat up to 80 deg F.unless you keep the AC on the whole time. This
affects the sound of speakers, especially FR in polypropylene models.


The ambient temperature can significantly affect Cms where an increase

in
temperature increases system compliance and leads to increased Vas and
decreased Fs which in turn increases overal Q. So the weather has a

greater
influence on the mechanical properties of a driver than most other

factors.

Sure. But that simply says that speakers do not break-in.


Agreed



Driver break-in is much less of an issue these days mainly because the
industry has for awhile now demanded low assembly line unit to unit
variability and polymer technology has made this possible. Break in,

when
present in the driver itself is usually in only in the amount of

hysteresis
leading to dicernable differences only when the cone is barely moving.

Meaning when Theil/Small parameters are generally measured :-)


A very common and very audible "break in" phenomena when first taking
speakers home is due to external factors. The ambient temperature

changes
from warehouse to car etc and temporarily changes mechanical

compliance.
Often a speaker is not stocked in the same orientation as it is used,

so
that internal damping materials often shift during the first days of

use
and
this can be very discernable. Even the re-location from a different
elevation can cause an atmospheric pressure gradient with a sealed

midrange
driver leading to a break-in phenomena for a few days until

equalibrium
has
been reached.

I'm guessing that elevation and storage equibrium is reached within a

few
seconds. If you have some more data I'd be glad to hear it.


Well I'll tell you a story. A customer of mine awhile back lived in
Redlands, California (elevation +/- 500 ft) and had a cabin at Big
Bear Lake (elevation +/- 6000 ft) that he frequently went to for a few
weeks at a time. He had a pair of one the smaller B&W Nautilus
speakers to first use the now common stiff larger 6" midrange driver
(I don't know the model number). Because he liked these speakers he
took them with him every time he went to his cabin. He noticed that
they sounded quite bad for a few days until they sorted themselves
out. When he contacted me about this, I explained the temperature
thing as a hypothesis, and he went to great lengths to correct for
this. A neighbor turned on the heat at the cabin a day in advance, he
pre-heated the car prior to loading, and he carried them outside
wrapped in a couple of sleeping bags. The problem didn't seem to go
away. We decided to look inside since he was considering mod's anyway.
In one of the speakers, a glob of glue had fallen on the leak hole in
the midrange enclosure. Also inspecting the driver and mounting seal,
it didn't appear that air was going to get out easily. Once this was
removed, the problem went away.

This is a little exceptional perhaps but it proves the point


Actually it doesn't seem relevant to your point. It seems that you just
discovered an operating flaw if anything. The "problem" was exactly what?

The
speakers didn't sound good for a few days but then started sounding good

when
you removed the plugged hole? None of this seems relevant to ambient

conditions
or elevation. Forgive me if I'm missing something here.


Many/most drivers leak air inheirantly from the front to the back of the
driver through porous cone material (kevlar) or through a fabric dust cover
with vented pole piece etc. Those with phase plugs leak by definition. If a
driver doesn't leak, and happens to be air tight mounted in a sealed
enclosure (this shouldn't happen), than an atmospheric pressure gradient is
possible to maintain between the outside air and the sealed cabinet. I would
imagine that most manufacturers provide a small hole to allow equalization.
I'm assuming, obviously don't know for sure, that this happened in the one
speaker in the example and made the set sound poor.

  #574   Report Post  
Wessel Dirksen
 
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Default

"Nousaine" wrote in message
...
(Wessel Dirksen) wrote:



John Stone wrote in message
...
in article
, Nousaine at
wrote
on 8/4/04 7:05 PM:

And the better sounding ones cost a lot more in terms of
cash outlay.

The Thor is around $1500.00. Have you heard it?

No. But John Stone reported on the Seas Odin kits he uses; and after

checking
these on the Madisound website they are actually more expensive than

the
excellent PSB Stratus Mini. So is this kit.


Yes, but are you then assuming that the 2 are qualitatively equal?

Let's
compare them. The PSB is a 6-1/2 2-way with a Vifa P17WJ 17cm and

D19AD
19mm alu dome tweeter.
The Odin is a WTW with 2 6-1/2" SEAS Excel woofers and a 25mm

"Millennium"
soft dome tweeter.


At this point John has said enough. This is apples vs. oranges.

If both kits are designed reasonably, based on components, the later
will tear up the former left, right and sideways. This is like
comparing a Saturn to a BMW M5.


Oh for Pete's sake. The finished PSB costs 2/3 of the kit. For an even

price
comparison, and if you want to play the driver-count game, you can get a

pair
of fully finished Paradigm Studio 60s for $1500 or a pair of Studio 40s

for
$1100. Both with full warranties.

Everyone wants to ignore that you aren't going to save money or get
demonstrably better performance, even with a high quality kit, compared to
what's commercially available.


Tom, are you sure about that? Are you sure you know what you're comparing
here? The last statement could be interpreted as just as presumpuous as
thinking there could be no performance difference between a true sportscar
and a family sedan. And I understand you review stuff so you'd be a good
judge.

Have you heard the Seas Milleneum tweeter in a good system in a good
listening environment? IMO, if depth of imaging is something you enjoy, I
would seriously listen sometime because this tweeter is exceptional. It and
a few exotic competitive counterparts are considered to be among the
industry's best dome tweeters and as you can see they don't cost a mortgage.
You normally find these tweeters (or OEM variants) in goofy priced exotic
production speakers. The run of the mill 19mm Vifa isn't in the ballpark.
The fact is this kit does not just have regular components, but recognized
industry performance exotica and the retail price is for probably about 60%
represented in the cost of the components. You just deemed them at par,
performance wise, with a $1200 retail product which probably has a
production cost in the neighborhood of $250 of which the components probably
represent less than a third. Why the difference? You do the sweating
yourself and you don't pay for expensive ad's. Even though price doesn't
have to say it all, you pretty much still get what you pay for on a large
scale (aside from exceptional stupid stuff like 300K amps). I'd bet the farm
on this Seas kit over the PSB and I haven't even seen or heard either and I
can do this with confidence, not suposition, because the particular PSB in
question with good but run of the mill transducers doesn't have a chance in
hell to outperform these high end Seas Excel components just as the Saturn
doesn't have a chance in hell on the racetrack against an BMW M5.

"high-end" speakers that aren't worth the paper the reviews are printed

on ---
so what?


  #575   Report Post  
Wessel Dirksen
 
Posts: n/a
Default

"Nousaine" wrote in message
...
"Wessel Dirksen" wrote:

...snip....

Actually it doesn't seem relevant to your point. It seems that you just
discovered an operating flaw if anything. The "problem" was exactly

what?
The
speakers didn't sound good for a few days but then started sounding

good
when
you removed the plugged hole? None of this seems relevant to ambient

conditions
or elevation. Forgive me if I'm missing something here.


Many/most drivers leak air inheirantly from the front to the back of the
driver through porous cone material (kevlar) or through a fabric dust

cover
with vented pole piece etc. Those with phase plugs leak by definition. If

a
driver doesn't leak, and happens to be air tight mounted in a sealed
enclosure (this shouldn't happen), than an atmospheric pressure gradient

is
possible to maintain between the outside air and the sealed cabinet. I

would
imagine that most manufacturers provide a small hole to allow

equalization.
I'm assuming, obviously don't know for sure, that this happened in the

one
speaker in the example and made the set sound poor.


Sure but didn't the original condition "change" with the passage of time

in
either direction? Wasn't the hole plugged all the time? Couldn't it be

more
likely that the system never changed sound but the listener simply

re-adjusted
his bias? Why not duplicate this condition? Of course, I understand that

this
may have occured long ago.


Probably unlikely, a small hole will never affect the Qtc of a closed system
so glue or no glue, performance is the same. A pressure gradient would
always be audible if it existed as it affects the function of the
transducer. But in all fairness, I don't know. For all I know the glue
didn't even cover the hole enough to abstruct air. The apparent reproducable
problem apparently sorted itself out leaving this as a reasonable hypothesis
..

I did completely seal a cabinet up with silicon stuff a reeeeal long time
ago ( I believe I was 17), and mounted a bike valvestem on the back. I
pumped it up and watched the woofer blob out then played Led Zeppelin on it
to see what it would sound like. It took about 30 seconds to gradually
normalize. I had nothing to measure it with back then but it sounded
terrible and slowly came back to life. Hilarious.



  #577   Report Post  
Dick Pierce
 
Posts: n/a
Default

(Nousaine) wrote
The Theile/Small parameters were originally developed so that
engineers could use commonly available test instruments and
develop a set of measurements to aid in design.


No, they were not. The Thiele-Small parameter set was developed as a
means of representing diverse parameters, such as acoustical vs
mechanical compliance, with a common set of units. A second reason
was to allow the representation of the system description in the
language of filter synthesis, thus the use of "Q" values for describing
mechanical, electrical and acoustical loss mechanisms.

An example of the almost tower of Babel units confusion is that of
compliance. The unit for mechanical compliance, Cm, is pretty straight-
forward and familiar to anyone having taken college freshman-level
physics: it described in terms of displacement per unit force, and in
units of meters per newton. On the other hand, acoustical compliance
is not so neat and obvious: it's expressed in units of meters^4 seconds^2
per kilogram! Now, quick, what's the effect of the parallel mechanical
combination of a mechanical stiffness with an acoustical stiffness?

Instead, what Small did was come up with a system-description relevant
unit: equivalent volume of compliance, Vas. This basically transforms
the mechanical compliance of the driver into a volume. It's MUCH
easier to calculate the effect of putting a mechanical compliance in
parallel with an acoustical compliance when both are stated in the same
units: volume. One can quickly see that a drive with a Vas of 50 liters
placed in a box with a volume of 50 liters will result in a total system
compliance of 25 liters.

All of the primary T/S parameters, Vas, Fs, Qms, Qes, Qts Vb, Qb and so
forth incorporate ALL of the fundamental mechanical and acoustical para-
meters of the system in a representation that makes the DESCRIPTION of
the system make sense in a system filter notation. One talks about the Q
of a high-pass electrical filter in precisely the same way that one
talks about the Q of a woofer system.

It had NOTHING to do with "commonly available test equipment." Indeed,
the equipment needed to measure the T/S parameter set is no more or less
common that that needed to measure the electromechanical parameter set.
In fact, one can measure the electromechanical properties almost directly
using LESS equipment. For example, the entire electromechanical property
set can be measured without using ANY AC signals. (How, one might wonder,
does one find the resonance without an AC signal? Well, if one knows the
mass, and one knows the compliance, and one can multiply and take square
roots and reciprocals, you're there. Oh, and you have to know pi to a decimal
place or three).

That was the beauty of them.


The T/S model has EVERYTHING to do with coherent, consistent SYSTEM description.
And THAT'S it's real beauty: describing speakers NOT as a collections of parts,
but as an inter-related SYSTEM having a SYSTEM RESPONSE FUNCTION.

--
+--------------------------------+
| Dick Pierce |
| Professional Audio Development |
+--------------------------------+
  #578   Report Post  
Nousaine
 
Posts: n/a
Default

"Wessel Dirksen" wrote:

"Nousaine" wrote in message
...
(Wessel Dirksen) wrote:



John Stone wrote in message
...
in article
, Nousaine at
wrote
on 8/4/04 7:05 PM:

And the better sounding ones cost a lot more in terms of
cash outlay.

The Thor is around $1500.00. Have you heard it?

No. But John Stone reported on the Seas Odin kits he uses; and after
checking
these on the Madisound website they are actually more expensive than

the
excellent PSB Stratus Mini. So is this kit.


Yes, but are you then assuming that the 2 are qualitatively equal?

Let's
compare them. The PSB is a 6-1/2 2-way with a Vifa P17WJ 17cm and

D19AD
19mm alu dome tweeter.
The Odin is a WTW with 2 6-1/2" SEAS Excel woofers and a 25mm

"Millennium"
soft dome tweeter.

At this point John has said enough. This is apples vs. oranges.

If both kits are designed reasonably, based on components, the later
will tear up the former left, right and sideways. This is like
comparing a Saturn to a BMW M5.


Oh for Pete's sake. The finished PSB costs 2/3 of the kit. For an even

price
comparison, and if you want to play the driver-count game, you can get a

pair
of fully finished Paradigm Studio 60s for $1500 or a pair of Studio 40s

for
$1100. Both with full warranties.

Everyone wants to ignore that you aren't going to save money or get
demonstrably better performance, even with a high quality kit, compared to
what's commercially available.


Tom, are you sure about that? Are you sure you know what you're comparing
here? The last statement could be interpreted as just as presumpuous as
thinking there could be no performance difference between a true sportscar
and a family sedan.


Why would that be? I've been a DIY constructor since the early 70s. I've been
evaluating speakers professionally since 1985.

And I understand you review stuff so you'd be a good
judge.


And?

Have you heard the Seas Milleneum tweeter in a good system in a good
listening environment? IMO, if depth of imaging is something you enjoy, I
would seriously listen sometime because this tweeter is exceptional. It and
a few exotic competitive counterparts are considered to be among the
industry's best dome tweeters and as you can see they don't cost a mortgage.
You normally find these tweeters (or OEM variants) in goofy priced exotic
production speakers. The run of the mill 19mm Vifa isn't in the ballpark.
The fact is this kit does not just have regular components, but recognized
industry performance exotica and the retail price is for probably about 60%
represented in the cost of the components.


What "kit" do you reference?

You just deemed them at par,
performance wise, with a $1200 retail product which probably has a
production cost in the neighborhood of $250 of which the components probably
represent less than a third. Why the difference?


What differennce? Are you suggesting that the distributor and the manufacturer
of speaker 'parts' don't need a mark-up? Are you suggesting that an individual
buying parts 2 pieces at a time has some economic advantage?

You do the sweating
yourself and you don't pay for expensive ad's.


Sure; but you also don't get to buy parts at OEM prices OR get to make then
yourself and eat the supplier margin.

Even though price doesn't
have to say it all, you pretty much still get what you pay for on a large
scale (aside from exceptional stupid stuff like 300K amps). I'd bet the farm
on this Seas kit over the PSB and I haven't even seen or heard either and I
can do this with confidence, not suposition, because the particular PSB in
question with good but run of the mill transducers doesn't have a chance in
hell to outperform these high end Seas Excel components just as the Saturn
doesn't have a chance in hell on the racetrack against an BMW M5.


I'm glad you are willing to 'bet the farm' on systems that you've never heard
:-)


"high-end" speakers that aren't worth the paper the reviews are printed

on ---
so what?


So what?
  #580   Report Post  
Wessel Dirksen
 
Posts: n/a
Default

Dick Pierce wrote in message ...
(Nousaine) wrote
The Theile/Small parameters were originally developed so that
engineers could use commonly available test instruments and
develop a set of measurements to aid in design.


No, they were not. The Thiele-Small parameter set was developed as a
means of representing diverse parameters, such as acoustical vs
mechanical compliance, with a common set of units. A second reason
was to allow the representation of the system description in the
language of filter synthesis, thus the use of "Q" values for describing
mechanical, electrical and acoustical loss mechanisms.

An example of the almost tower of Babel units confusion is that of
compliance. The unit for mechanical compliance, Cm, is pretty straight-
forward and familiar to anyone having taken college freshman-level
physics: it described in terms of displacement per unit force, and in
units of meters per newton. On the other hand, acoustical compliance
is not so neat and obvious: it's expressed in units of meters^4 seconds^2
per kilogram! Now, quick, what's the effect of the parallel mechanical
combination of a mechanical stiffness with an acoustical stiffness?

Instead, what Small did was come up with a system-description relevant
unit: equivalent volume of compliance, Vas. This basically transforms
the mechanical compliance of the driver into a volume. It's MUCH
easier to calculate the effect of putting a mechanical compliance in
parallel with an acoustical compliance when both are stated in the same
units: volume. One can quickly see that a drive with a Vas of 50 liters
placed in a box with a volume of 50 liters will result in a total system
compliance of 25 liters.

All of the primary T/S parameters, Vas, Fs, Qms, Qes, Qts Vb, Qb and so
forth incorporate ALL of the fundamental mechanical and acoustical para-
meters of the system in a representation that makes the DESCRIPTION of
the system make sense in a system filter notation. One talks about the Q
of a high-pass electrical filter in precisely the same way that one
talks about the Q of a woofer system.

It had NOTHING to do with "commonly available test equipment." Indeed,
the equipment needed to measure the T/S parameter set is no more or less
common that that needed to measure the electromechanical parameter set.
In fact, one can measure the electromechanical properties almost directly
using LESS equipment. For example, the entire electromechanical property
set can be measured without using ANY AC signals. (How, one might wonder,
does one find the resonance without an AC signal? Well, if one knows the
mass, and one knows the compliance, and one can multiply and take square
roots and reciprocals, you're there. Oh, and you have to know pi to a decimal
place or three).


Agreed Dick if you happen to know Mms, but what if you don't know
anything about a driver and don't want to guess. Cms can be determined
statically with the added mass - cone displacement method, but how
would you then determine Mms without an AC signal. Is there something
I'm missing. You have to know at least 2 of the 3, fs, Cms, or Mms.


That was the beauty of them.


The T/S model has EVERYTHING to do with coherent, consistent SYSTEM description.
And THAT'S it's real beauty: describing speakers NOT as a collections of parts,
but as an inter-related SYSTEM having a SYSTEM RESPONSE FUNCTION.



  #581   Report Post  
Dick Pierce
 
Posts: n/a
Default

For example, the entire electromechanical property
set can be measured without using ANY AC signals. (How, one might wonder,
does one find the resonance without an AC signal? Well, if one knows the
mass, and one knows the compliance, and one can multiply and take square
roots and reciprocals, you're there. Oh, and you have to know pi to a decimal
place or three).


Agreed Dick if you happen to know Mms, but what if you don't know
anything about a driver and don't want to guess. Cms can be determined
statically with the added mass - cone displacement method, but how
would you then determine Mms without an AC signal. Is there something
I'm missing. You have to know at least 2 of the 3, fs, Cms, or Mms.


Well, there's always the direct method: weigh the cone. That certainly
works well in my situation where I'm given a dozen samples to evaluate
and can sacrifice several of them during a tear-down. These days, mass
is among the most tightly controlled proproties of the cone: you measure
one, you've measured them all.

Alternatively, once you've determined Cms as you describe (and, by the
way, with a variable DC power supply, you also determine Bl by injecting
a current sufficient to restore the cone back to its rest position), you
can measure mass by measuring the deflection with the axis vertical, invert
the driver, measure it again, and calculate the mass from the deflection and
compliance.

But, more to the point, the T/S parameter set didn't come about as a means
of making measurements convenient.

--
+--------------------------------+
| Dick Pierce |
| Professional Audio Development |
+--------------------------------+
  #583   Report Post  
Wessel Dirksen
 
Posts: n/a
Default

"Nousaine" wrote in message
...
"Wessel Dirksen" wrote:

"Nousaine" wrote in message
...
(Wessel Dirksen) wrote:



John Stone wrote in message
...
in article
, Nousaine at


wrote
on 8/4/04 7:05 PM:

And the better sounding ones cost a lot more in terms of
cash outlay.

The Thor is around $1500.00. Have you heard it?

No. But John Stone reported on the Seas Odin kits he uses; and

after
checking
these on the Madisound website they are actually more expensive

than
the
excellent PSB Stratus Mini. So is this kit.


Yes, but are you then assuming that the 2 are qualitatively equal?

Let's
compare them. The PSB is a 6-1/2 2-way with a Vifa P17WJ 17cm and

D19AD
19mm alu dome tweeter.
The Odin is a WTW with 2 6-1/2" SEAS Excel woofers and a 25mm

"Millennium"
soft dome tweeter.

At this point John has said enough. This is apples vs. oranges.

If both kits are designed reasonably, based on components, the later
will tear up the former left, right and sideways. This is like
comparing a Saturn to a BMW M5.

Oh for Pete's sake. The finished PSB costs 2/3 of the kit. For an even

price
comparison, and if you want to play the driver-count game, you can get

a
pair
of fully finished Paradigm Studio 60s for $1500 or a pair of Studio 40s

for
$1100. Both with full warranties.

Everyone wants to ignore that you aren't going to save money or get
demonstrably better performance, even with a high quality kit, compared

to
what's commercially available.


Tom, are you sure about that? Are you sure you know what you're comparing
here? The last statement could be interpreted as just as presumpuous as
thinking there could be no performance difference between a true

sportscar
and a family sedan.


Why would that be? I've been a DIY constructor since the early 70s. I've

been
evaluating speakers professionally since 1985.


Geez Tom, so you obviously know alot about this; so I don't quite get your
angle on a few of the last replies here. I'm sure you've got knowledge to
share here and yet instead of clarifying your views, you seem to diffuse
them. Please expand on why . . . "you aren't going to save money or get
demonstrably better performance, even with a high quality kit, compared to
what's commercially available". This is a powerfully stated generalization.

I feel it's usually the other way around but anything's possible on a case
to case basis. The Seas kit vs. PSB comparison in question here is
especially poignant, indicated in the detailed comparison John Stone made. I
put in my rather strongly stated opinion that the enormous performance
difference of the drivers (joe blow vs. top of the trade) should be enough
to demonstrate with a good amount of certainty the kit as the beter
performer. I understand that you're not in agreement. So what's your opinion
on the total package vs.driver performance issue?

And I understand you review stuff so you'd be a good
judge.


And?

Have you heard the Seas Milleneum tweeter in a good system in a good
listening environment? IMO, if depth of imaging is something you enjoy, I
would seriously listen sometime because this tweeter is exceptional. It

and
a few exotic competitive counterparts are considered to be among the
industry's best dome tweeters and as you can see they don't cost a

mortgage.
You normally find these tweeters (or OEM variants) in goofy priced exotic
production speakers. The run of the mill 19mm Vifa isn't in the ballpark.
The fact is this kit does not just have regular components, but

recognized
industry performance exotica and the retail price is for probably about

60%
represented in the cost of the components.


What "kit" do you reference?


The one John Stone was comparing to the Seas Odin awhile back.

You just deemed them at par,
performance wise, with a $1200 retail product which probably has a
production cost in the neighborhood of $250 of which the components

probably
represent less than a third. Why the difference?


What differennce? Are you suggesting that the distributor and the

manufacturer
of speaker 'parts' don't need a mark-up? Are you suggesting that an

individual
buying parts 2 pieces at a time has some economic advantage?


Not at all. But there are more factors involved that make it a sort of
"forest for the trees" thing. The advantages of lower costs for materials
are far outweighed by the non-material costs to manufacture, market, and
retail a hi-fi loudspeaker. Less than half of the total manufacturing cost
of a loudspeaker comes from materials. Costs to construct those components
into a product (labor) is the largest manufacturing expenditure, but that's
often not even the biggest portion of the pricetag. The retailer demands a
sizeable portion for his effort on top of that. In the end the actual cost
to manufacture a loudspeaker is in the neighborhood of 20 to 25% of MSRP.
Considering that DIY has become a large enough industry which can also OEM
purchase, kits are ussually cheaper than the sum of all parts sold
independantly which eases DIY retail prices somewhat.

What is important is how good the kits are designed. I would like to think
that the big manufacturers have the advantage of superior expertise on their
side and would know how to take a good idea far. It seems that DIY has
followed the market but does less so these days.


You do the sweating
yourself and you don't pay for expensive ad's.


Sure; but you also don't get to buy parts at OEM prices OR get to make

then
yourself and eat the supplier margin.

Even though price doesn't
have to say it all, you pretty much still get what you pay for on a large
scale (aside from exceptional stupid stuff like 300K amps). I'd bet the

farm
on this Seas kit over the PSB and I haven't even seen or heard either and

I
can do this with confidence, not suposition, because the particular PSB

in
question with good but run of the mill transducers doesn't have a chance

in
hell to outperform these high end Seas Excel components just as the

Saturn
doesn't have a chance in hell on the racetrack against an BMW M5.


I'm glad you are willing to 'bet the farm' on systems that you've never

heard
:-)


"high-end" speakers that aren't worth the paper the reviews are printed

on ---
so what?


So what?


  #584   Report Post  
Wessel Dirksen
 
Posts: n/a
Default

"Dick Pierce" wrote in message
...
For example, the entire electromechanical property
set can be measured without using ANY AC signals. (How, one might

wonder,
does one find the resonance without an AC signal? Well, if one knows

the
mass, and one knows the compliance, and one can multiply and take

square
roots and reciprocals, you're there. Oh, and you have to know pi to a

decimal
place or three).


Agreed Dick if you happen to know Mms, but what if you don't know
anything about a driver and don't want to guess. Cms can be determined
statically with the added mass - cone displacement method, but how
would you then determine Mms without an AC signal. Is there something
I'm missing. You have to know at least 2 of the 3, fs, Cms, or Mms.


Well, there's always the direct method: weigh the cone. That certainly
works well in my situation where I'm given a dozen samples to evaluate
and can sacrifice several of them during a tear-down. These days, mass
is among the most tightly controlled proproties of the cone: you measure
one, you've measured them all.

Alternatively, once you've determined Cms as you describe (and, by the
way, with a variable DC power supply, you also determine Bl by injecting
a current sufficient to restore the cone back to its rest position), you
can measure mass by measuring the deflection with the axis vertical,

invert
the driver, measure it again, and calculate the mass from the deflection

and
compliance.


Indeed, hadn't thought about that one. Certainly fun from a theoretical
standpoint although not very practical.
Probably wouldn't have enough displacement resolution with a smaller Cms
though.


But, more to the point, the T/S parameter set didn't come about as a means
of making measurements convenient.

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


  #585   Report Post  
Nousaine
 
Posts: n/a
Default

"Wessel Dirksen" wrote:

"Nousaine" wrote in message


....snip to specific point...


Why would that be? I've been a DIY constructor since the early 70s. I've

been
evaluating speakers professionally since 1985.


Geez Tom, so you obviously know alot about this; so I don't quite get your
angle on a few of the last replies here. I'm sure you've got knowledge to
share here and yet instead of clarifying your views, you seem to diffuse
them. Please expand on why . . . "you aren't going to save money or get
demonstrably better performance, even with a high quality kit, compared to
what's commercially available". This is a powerfully stated generalization.


This is based on my examination of several hundred commerically available
speakers and several dozen DIY models. I've never found a DIY speaker (other
than a subwoofer) that offered better performance for less cost than a
better-than-average commerically available model. Never. That doesn't mean that
I haven't encountered a handful of DIY speakers that weren't better than
commerical models but at a higher price.



I feel it's usually the other way around but anything's possible on a case
to case basis. The Seas kit vs. PSB comparison in question here is
especially poignant, indicated in the detailed comparison John Stone made. I
put in my rather strongly stated opinion that the enormous performance
difference of the drivers (joe blow vs. top of the trade) should be enough
to demonstrate with a good amount of certainty the kit as the beter
performer.


It's a commonly held misunderstanding that throwing money at a project with
expensive drivers automatically makes for a better finished system. I will
grant that the kits in question do have quite a pedigree with the designers
credentials and will in most cases result in a very good sounding product BUT
the particular kit does not appear to offer significantly better performance
than a commercial product of 2/3 the price or other finished products of
similar price.

I'm at a loss that people seem to think this is an attack on DIY. I think that
the big advantage of DIY is the educational experience, elimination of the
product selection and buying process and the on-line socialism possibilities
with other kit-builders and DIY enthusiasts.

I'm simply ponting out that if you think you're going to save money
rolling-your-own you might want to think that idea over carefully.

I understand that you're not in agreement. So what's your opinion
on the total package vs.driver performance issue?


We've been talking about driver performance here and no one has ever spoken a
word about real-performance. Just like car engines knowing the motor used in a
car isn't enough by itself to decide in advance whether its fast enough.

Same with drivers. I use TC Sounds 15-inch woofers in my DIY subwoofers that
have an individual Fs of 30-32 Hz with a Qts of 0.53-0.57 and a Vas of 3.5 ft3
which were made with off-the-shelf parts. Do those numbers disqualify them from
being a good subwoofer? Not many people would be satisfied with a subwoofer
with a free-air resonance of over 30 Hz.

Can you predict what the actual system performance is from them? Certainly not;
you have to know how they will be deployed.

In my case the System has a natural resonance of 21 Hz when 8 of these drivers
are mounted in an 8-foot plenum and are flat to 12 Hz at my listening position
with 18 dB of EQ at 12 Hz and will deliver 120 dB+ from 12 to 62 Hz (10% THD)
when driven with a 5000 watt amplifier.

A good part of this latter performance is dependent upon these drivers having a
23.4 mm Xmax (linear stroke) which is a measured value and was not known when I
purchased the drivers. I was 'hoping" for a value of 16mm and the driver count
of 8 was based on that.

But none of this meant low cost. The total $$$ input to the system was well
over $5000 not counting my own labor, the DUMAX testing (which I was able to
get in trade), the cost of the loudspeakers I traded to another fellow for some
carpentry or the cost of my own measurement equipment. It is true that the cash
outlay is less than the cost of a Velodyne 1812 but don't forget that it was
attainable because I had access to measurement and other professional services
that the average guy doesn't sometimes even know about.

Have I saved any money? Doubtful. I could buy a Genelec HST6 for about the same
total outlay. Have I gotten better performance? Absolutely; the Velodyne is
high-passed at 15 Hz and the Genelec at 19Hz.

Would someone without accomodation pricing be able to do likewise. Sure. But in
trade for 10 Hz extension it's going to cost him.


And I understand you review stuff so you'd be a good
judge.


And?

Have you heard the Seas Milleneum tweeter in a good system in a good
listening environment? IMO, if depth of imaging is something you enjoy, I
would seriously listen sometime because this tweeter is exceptional. It

and
a few exotic competitive counterparts are considered to be among the
industry's best dome tweeters and as you can see they don't cost a

mortgage.
You normally find these tweeters (or OEM variants) in goofy priced exotic
production speakers. The run of the mill 19mm Vifa isn't in the ballpark.
The fact is this kit does not just have regular components, but

recognized
industry performance exotica and the retail price is for probably about

60%
represented in the cost of the components.


What "kit" do you reference?


The one John Stone was comparing to the Seas Odin awhile back.

You just deemed them at par,
performance wise, with a $1200 retail product which probably has a
production cost in the neighborhood of $250 of which the components

probably
represent less than a third. Why the difference?


What differennce? Are you suggesting that the distributor and the

manufacturer
of speaker 'parts' don't need a mark-up? Are you suggesting that an

individual
buying parts 2 pieces at a time has some economic advantage?


Not at all. But there are more factors involved that make it a sort of
"forest for the trees" thing. The advantages of lower costs for materials
are far outweighed by the non-material costs to manufacture, market, and
retail a hi-fi loudspeaker. Less than half of the total manufacturing cost
of a loudspeaker comes from materials. Costs to construct those components
into a product (labor) is the largest manufacturing expenditure, but that's
often not even the biggest portion of the pricetag. The retailer demands a
sizeable portion for his effort on top of that. In the end the actual cost
to manufacture a loudspeaker is in the neighborhood of 20 to 25% of MSRP.
Considering that DIY has become a large enough industry which can also OEM
purchase, kits are ussually cheaper than the sum of all parts sold
independantly which eases DIY retail prices somewhat.


Sure I understand all that. It's just thatv there are a number of manufacturers
who have put all this together and deliver commecial products that are simply
outstanding for the price and rival or beat the performance of any DIY project
on a $ for $ basis.

I'm thinking that I'm perhaps the only person on Earth who is willing to
ackowledge that some manufacturers are able to make a better full range or
satellite loudspeaker for less money than I can do myself. And that's based on
what my ears, test instruments as well as my wallet tell me.

What is important is how good the kits are designed. I would like to think
that the big manufacturers have the advantage of superior expertise on their
side and would know how to take a good idea far. It seems that DIY has
followed the market but does less so these days.


Well Joe D'Appolito is now Chief Engineer for Snell and had been associated
with Usher prior. Personally I think DIY should not follow the market BUT guess
what even the Adire and Madisound websites don't offer any 10-12 Hz kit
systems. Instead they seem to be emulating the current commerical products of
which direct-mail Hsu and SVSubwoofers seem to offer as much performance for a
given $ as the DIY systems.

I'm guessing that we've taken this thread as far as it needs to go.


  #586   Report Post  
Nousaine
 
Posts: n/a
Default

"Wessel Dirksen" wrote:

....snip to content ......

Well Joe D'Appolito is now Chief Engineer for Snell and had been
associated
with Usher prior. Personally I think DIY should not follow the market BUT

guess
what even the Adire and Madisound websites don't offer any 10-12 Hz kit
systems. Instead they seem to be emulating the current commerical products

of
which direct-mail Hsu and SVSubwoofers seem to offer as much performance

for a
given $ as the DIY systems.

I'm guessing that we've taken this thread as far as it needs to go.


Agreed, thanks for the last bit. Our opinions seem to stem from experience
from literally different sides of the spectrum. You have cited much
sub-woofer experience. My whole emphasis tends to be imaging where the
tweeter plays a pivital role. Individual driver performance among tweeters
IMO is quite diverse. Maybe you've done so, but if not, try a Seas Milleneum
or a Scanspeak D2904 sometime in a project, it's hard to go back.


Actually our experience isn't that different. I started out making full-range
and satellite systems. I held the same views you seem to have now but after
25-years of experience and evaluation of dozens of DIY systems and hundreds ot
commercially available products I just concluded that unless you have access to
measurement equipment the likelihood of getting a bertter product for less
money going roll-your-own or kit-your-own is unlikely. The sole exception is
subwoofers where all commercial products are effectively high-passed in some
way.

Let me expand on your opinion that the "tweeter" plays a big role in imaging.
The directivity of the tweeter and of its location will have an effect on
spatiality but for the most part good spatial rendition is first a mid-range
function.
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