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Evolution of and Replacements for the AR 11/12" Woofer


Pete B

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Hi,

Yes interesting to be able to count the turns right off the picture.

It's sort of detective work to figure out what's going on with these woofers, interesting.

>Hi there

>

>Isn't digital photography a wonderful tool?

>

>I never even spent 5 minutes really ever looking at a voice

>coil before, but with these pictures and the feedback it

>certainly makes this more interesting.

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I've been aware of thermal issues for a long time and even stated that voice coils should be black anodized many years ago but this is the first I've seen in practice.

Those 10Pi's are a part of audio history, obviously, I'd guess that you've got you own AR museum there.

Yes most drivers will take a lot of short term power, it's interesting to look at the sine burst tests done in the old Audio reviews by Don Keele.

Pete B.

>It appears that the late-70s designation of the 200003/1210003

>woofer (AR-9/AR-11B) you show is consistent the advent of the

>aluminum voice-coil former. The anodized-aluminum former was

>more robust (up to a point) and would likely dissipate heat

>better than the first versions. Ironically, the voice coil I

>showed with the flattened former was hit with peaks in excess

>of 1 kilowatts. That will usually do it, although the

>AR-10Pi/Neil Grover live-vs.-recorded drum demonstration by

>AR/C. Victor Campors in the mid-1970s used the ill-fated

>Dunlap-Clarke Dreadnaught 1000 amplifier driven to full power

>much of the time before failing completely. I don't believe

>that the woofers suffered any damage (I own one of the

>original pairs of 10Pis used in the demonstration, and it has

>all the original drivers according to the date codes), but

>there were some tweeters destroyed. So the woofers will

>definitely take a lot of peak power before damage.

>

>One way to help in removing the glue on the woofer flange is

>to use denatured alcohol to soften the glue, and then

>carefully scrape away. It's slow, laborious work, but a clean

>surface is mandatory for good results.

>

>--Tom Tyson

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>I've been aware of thermal issues for a long time and even

>stated that voice coils should be black anodized many years

>ago but this is the first I've seen in practice.

>Those 10Pi's are a part of audio history, obviously, I'd guess

>that you've got you own AR museum there.

>Yes most drivers will take a lot of short term power, it's

>interesting to look at the sine burst tests done in the old

>Audio reviews by Don Keele.

>

Pete, as you stated,

"...I've been aware of thermal issues for a long time and even

stated that voice coils should be black anodized many years

ago but this is the first I've seen in practice...."

Pete, you should have patented your idea when it came to you. However, I believe that the qualities of anodized-aluminum for this purpose are well-known, and have been around for many years. Prior to this, the usual material was phosphor-bronze, which has similar heat dissipation qualities. As Frederick Hunt put it in his book, *Electroacoustics,* "...As is often the case with ideas that appear superficially to be simple, a good many loudspeaker designers discovered that they had already made this invention -- after someone else had pointed out what the invention was...."

It is both bad and good that I do have a sort of AR museum here. I was fortunate to acquire the AR-10Pi's that were used in the Neil Grover live-vs.-recorded session. I have also donated some of my collection to historical museums such as The Museum of American History, and will continue to do so.

As for power-handling, there are actually relatively few speakers made back in the mid-1970s that could handle peaks of 1000 watts. Part of the reason the AR-10Pi's could handle that sort of power was (1) robust-build quality with heavy voice coils and (2) sealed, acoustic-suspension cabinet which tends to protect the woofer at ultrasonic frequencies. By contrast, I managed to heavily damage a B&W 801 Matrix woofer during a high-power, low-frequency "bass-drum tests" demonstration to some friends. It was physical damage by over-excursion (became "uncoupled" with the air) due to the vented design, not thermal damage. My amplifier was the Crown Studio Reference, and the peak-power at low frequencies was about a thousand watts.

--Tom Tyson

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It's been said that most good ideas have already been done, and I'd have to say that this AR woofer is an example of prior art with regards to my thoughts on black anodizing, I didn't know about it at the time.

I've usually seen aluminized paper used in smaller drivers and I'd think that a thin layer of aluminum on those Nomex formers would help quite a bit as far as heat sinking goes. On the other hand solid metal formers have the advantage that both sides serve as heat radiating area. One problem with pure aluminum is the difference in the coefficient of thermal expansion as compared to the copper windings, it does seem that they've gotten around this since aluminum is common these days. This is one reason that I like bronze type formers.

I'm curious to know what the source material was used for your drum test, live recordings often have a lot of subsonic material that should be filtered. Vocal pops, string initial impact and so on. Were you running the active filter for the 801s? It's an interesting challenge to try to reproduce uncompressed material at realistic levels.

Keele probably half joking, referred to a system I particularly like as the 10,000 Watt speaker. The original PSB Stratus Golds will handle his short term burst test at 10,000 W above 700 Hz. He runs a bridged Crown amp to do this. One has to wonder if the voltage rating of the capacitors is exceeded in this test. This system crosses and stays above the 120 dB mark (at about 4 kW bursts) from 70 Hz on up in Max SPL capability. I don't need this SPL level but it just shows how much head room is available and the robust construction.

Many here talk of specs and the flat response of AR speakers. The first version of the Stratus Golds were rated at +/- 1 dB from 36 Hz to 20 kHz on axis. This is hard to believe and Keele was only able to confirm +/- 1.5 dB from 40 to 20 K, still not bad and Keele does outdoor tests with spliced near field woofer response if I remember correctly, so there's some room for error. Both specs are certainly outstanding. I found this hard to believe and actually measured the Thiel and Small parameters of the Stratus Gold woofer, then simulated the response, -.9 dB at 36 Hz - impressive.

They claim hand selection of inductors and caps to a 1% tolerance, resistors are 2%. There are no exotic parts but I'd expect tight quality control on drivers. I'm just offering this as a comparison to a value engineered modern design.

Pete B.

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>It's been said that most good ideas have already been done,

>and I'd have to say that this AR woofer is an example of prior

>art with regards to my thoughts on black anodizing, I didn't

>know about it at the time.

>

>I've usually seen aluminized paper used in smaller drivers and

>I'd think that a thin layer of aluminum on those Nomex formers

>would help quite a bit as far as heat sinking goes. On the

>other hand solid metal formers have the advantage that both

>sides serve as heat radiating area. One problem with pure

>aluminum is the difference in the coefficient of thermal

>expansion as compared to the copper windings, it does seem

>that they've gotten around this since aluminum is common these

>days. This is one reason that I like bronze type formers.

>

>I'm curious to know what the source material was used for your

>drum test, live recordings often have a lot of subsonic

>material that should be filtered. Vocal pops, string initial

>impact and so on. Were you running the active filter for the

>801s? It's an interesting challenge to try to reproduce

>uncompressed material at realistic levels.

>

>Keele probably half joking, referred to a system I

>particularly like as the 10,000 Watt speaker. The original

>PSB Stratus Golds will handle his short term burst test at

>10,000 W above 700 Hz. He runs a bridged Crown amp to do

>this. One has to wonder if the voltage rating of the

>capacitors is exceeded in this test. This system crosses and

>stays above the 120 dB mark (at about 4 kW bursts) from 70 Hz

>on up in Max SPL capability. I don't need this SPL level but

>it just shows how much head room is available and the robust

>construction.

>Many here talk of specs and the flat response of AR speakers.

>The first version of the Stratus Golds were rated at +/- 1 dB

>from 36 Hz to 20 kHz on axis. This is hard to believe and

>Keele was only able to confirm +/- 1.5 dB from 40 to 20 K,

>still not bad and Keele does outdoor tests with spliced near

>field woofer response if I remember correctly, so there's some

>room for error. Both specs are certainly outstanding. I

>found this hard to believe and actually measured the Thiel and

>Small parameters of the Stratus Gold woofer, then simulated

>the response, -.9 dB at 36 Hz - impressive.

>They claim hand selection of inductors and caps to a 1%

>tolerance, resistors are 2%. There are no exotic parts but

>I'd expect tight quality control on drivers. I'm just

>offering this as a comparison to a value engineered modern

>design.

>

>Pete B.

Hi there

I wrote a story a few months ago from memory about the KEF-107's and how thirsty they were.

I believe it was a report from Audio? and about 12 pages long.

A custom 5,000 watt amplifier was used.

The reviewer had commented on the fact that clipping amps had been a major limitation previously for testing speakers.

They had this amp clipping using just the tweeter section.

Maybe this is what we need, now that we can't hear as well, from playing rock music so loud when we were young.

Pardon me while I go replace my hearing aid batteries.

Have a good one.

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>It's been said that most good ideas have already been done,

>and I'd have to say that this AR woofer is an example of prior

>art with regards to my thoughts on black anodizing, I didn't

>know about it at the time.

>

As we know, AR was a true pioneer in the development of many innovations and technological advances in the science of sound reproduction. But even AR was not afraid to use the best conventional methods of the day, and anodized-aluminum voice coils certainly falls into that category. It’s not really an example of “prior art,” which refers principally to patents, but to a process resident in the public domain for many years. This is in contrast to Thiel and PSB (that you mentioned), companies that produce physically beautiful loudspeakers, but who have contributed little to the science of sound reproduction. Are there any significant contributions from these companies that have affected the entire speaker industry?

>

>I'm curious to know what the source material was used for your

>drum test, live recordings often have a lot of subsonic

>material that should be filtered. Vocal pops, string initial

>impact and so on. Were you running the active filter for the

>801s? It's an interesting challenge to try to reproduce

>uncompressed material at realistic levels.

>

There were several discs used: (1) Telarc early Stravinsky’s *Firebird;* (2) Stravinsky’s *Rite of Spring;* (3) Telarc’s *Bachbusters,* (4) a famous analog percussion/drum CD that used to be used in hi-fi shows, whose title escapes me and (5) an uncompressed analog 15-ips drum/percussion recording made on my Ampex 440B. I believe the damage was caused by the heavily recorded *Firebird* bass-drum notes, and not actually by the home-brew recording. The B&W filter was definitely in use -- I never used the speakers without it. The filter flattens and extends the bass response while protecting the speaker against sub-sonic energy, so it was the 40Hz bass-drum energy that most likely damaged the woofer at very high power levels. The filter did allow 20Hz energy to get to the woofer, but had a steep roll-off below that frequency. Incidentally, I am now far removed from this type of foolish ear-shattering demonstration. That was twenty-years ago. I merely wanted to point out that not many speaker designs were capable of sustaining short-term, high-energy bursts at low frequencies.

>

>Many here talk of specs and the flat response of AR speakers.

>The first version of the Stratus Golds were rated at +/- 1 dB

>from 36 Hz to 20 kHz on axis. This is hard to believe and

>Keele was only able to confirm +/- 1.5 dB from 40 to 20 K,

>still not bad and Keele does outdoor tests with spliced near

>field woofer response if I remember correctly, so there's some

>room for error. Both specs are certainly outstanding.

>Pete B.

>

Pete, the spec of +/- 1dB from 36 Hz to 20 kHz, *on-axis,* does not impress me in the least. It is meaningless in the grand scheme of things. The speaker you mention is directional at most mid-and-high frequencies, and I believe has steep 24 dB crossover slopes. This will produce very flat on-axis response if the drivers are appropriately high-quality. A speaker such as this also has a relatively focused energy output, and does not have good integrated-power response. It might be very flat, on-axis, in the near field, but it will sound increasingly *dull* the further back in the listening environment you get -– even on the speaker’s axis. Placement of the speakers and the listening position is therefore highly critical for good results, and it allows only one person at a time to truly get into the “sweet spot,” and other listeners have to wait their turn, or are likely to get a different impression of the performance of that speaker. In short, the speaker takes on different personalities when one moves around the room. If one seeks that type of listening, why not simply listen through good-quality headphones?

Like it or not, we are influenced by the room boundaries and reflections, which are a balance of the *sum* of direct and reverberant fields. Even Baranek’s calculations imply that listeners are almost always in the reverberant field of the room for all frequencies being reproduced, and a wide-dispersion loudspeaker is necessary to support uniform and flat response in the reverberant field. Most of the AR speakers we mention in the forum have wide dispersion, and provide good integrated-power response in the typical listening room. Yes, we “talk of specs and the flat response of AR speakers,” but the reference is made primarily to the integrated-power energy of these speakers, which in the real world is more important than the simple in-situ on-axis frequency response.

--Tom Tyson

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>As we know, AR was a true pioneer in the development of many

>innovations and technological advances in the science of sound

>reproduction. But even AR was not afraid to use the best

>conventional methods of the day, and anodized-aluminum voice

>coils certainly falls into that category. It’s not really an

>example of “prior art,” which refers principally to patents,

>but to a process resident in the public domain for many years.

> This is in contrast to Thiel and PSB (that you mentioned),

>companies that produce physically beautiful loudspeakers, but

>who have contributed little to the science of sound

>reproduction. Are there any significant contributions from

>these companies that have affected the entire speaker

>industry?

Hi Tom,

I'm fairly sure that black anodized aluminum former voice coils are common today in some of the better woofers but I don't think they were common that far back. In fact, I seem to be the first reporting it in an AR woofer, most others are not anodized. I've not done extensive research so I'm not going to get into a back and forth. I referred to it as prior art because most ideas such as this, as obvious and trivial as they might be, become patented. I have some experience with the patent system and it is a mess, it is pathetic but I won't get into the details.

Several here have commented on innovation and significant contributions to the art/science which is fine but not a requirement for every company producing speakers, from my perspective. I'm able to admire a company that simply applies the well known concepts of the day and produces a top notch product, especially at a fair price. PSB speakers test very well, have been praised by both the objectivists (Keele) and the subjectivists (several at Stereophile), and they sound outstanding for their price point to my ear.

I was referring to Thiele in the sense of Thiele and Small driver parameters. OK you made me look up the spelling, it is Thiele and I apologize to Mr. Thiele as I admire his work very much.

Concerning Theil speakers, they've certainly perfected first order crossover design and system designs that attempt to preserve wave shape. They've also perfected high performance coaxial speakers. These are not high priorities from my perspective.

Thanks for the mention of the source material, I think I have a few of those but do not play them often.

>>Many here talk of specs and the flat response of AR speakers.

>

>>The first version of the Stratus Golds were rated at +/- 1

>dB

>>from 36 Hz to 20 kHz on axis. This is hard to believe and

>>Keele was only able to confirm +/- 1.5 dB from 40 to 20 K,

>>still not bad and Keele does outdoor tests with spliced near

>>field woofer response if I remember correctly, so there's

>some

>>room for error. Both specs are certainly outstanding.

>>Pete B.

>>

>

>Pete, the spec of +/- 1dB from 36 Hz to 20 kHz, *on-axis,*

>does not impress me in the least. It is meaningless in the

>grand scheme of things. The speaker you mention is

>directional at most mid-and-high frequencies, and I believe

>has steep 24 dB crossover slopes. This will produce very flat

>on-axis response if the drivers are appropriately

>high-quality. A speaker such as this also has a relatively

>focused energy output, and does not have good integrated-power

>response. It might be very flat, on-axis, in the near field,

>but it will sound increasingly *dull* the further back in the

>listening environment you get -– even on the speaker’s axis.

>Placement of the speakers and the listening position is

>therefore highly critical for good results, and it allows only

>one person at a time to truly get into the “sweet spot,” and

>other listeners have to wait their turn, or are likely to get

>a different impression of the performance of that speaker. In

>short, the speaker takes on different personalities when one

>moves around the room. If one seeks that type of listening,

>why not simply listen through good-quality headphones?

A specification of +/-1 dB from flat and not a prototype response, over that wide a range for a production speaker is mighty impressive IMO. Many here are having trouble getting their -3dB point below 40 Hz for the AR 11/12" woofer. Few unequalized systems even offer the bass extension. It's interesting that 4th order LR crossover is claimed for the mid to tweeter XO in the PSBs and it is obtained with 2nd order electrical networks in combination with the driver's acoustical response. I believe they're approximately 4th order LR. The mid to woofer is claimed to be 3rd order, IIRC but looks to me to be approximately 4th order also. It is well known that 4th order LR crossovers do not have flat power response, however I never believed AR's claim of the importance of flat power reponse, since I first heard them and found them lacking.

I'm certainly familiar with the power response issue as it relates to crossover design and it has been covered for probably more than 30 years in the technical journals. I'm familiar with most of these papers and don't believe that a passive higher order network has been covered that provides both flat on axis and flat power response. It appears, based on looking at AR's published specs that some driver overlap is used to improve the power reponse, however I don't believe this provides flat *summed* on axis response. I also do not believe that this crossover with overlap and the goal of flat power response has been covered in the journals. There are many experts that place on axis response as the most important parameter, and I agree with them. This of course assumes that a reasonable crossover type is chosen so that the off axis response does not suffer significantly.

Your discussion of near field (using this term loosly) as compared to other listening positions might apply to much larger rooms but I would not agree with your analysis in the typical home environment. Reflections from the boundaries around the speakers in the typical sized home environment are far too early to improve the sound in any way, indeed these early reflections tend to blur the early arrival. This is why the front of the NHT 3.3 is aimed in toward the listener to reduce side wall reflections, it is also why the signal is electronically delayed in the AR systems that have reflective firing augmentation speakers. We may also note that the design of the 3.3 forces the main drivers to be far out from the wall behind them which also reduces early reflections.

I've found in practice just the opposite of your theories claimed above, that systems with higher order in-phase crossovers sound good in most listening postitions. They have excellent polar response and the sound does not vary significantly in seated or standing positions, or over a wide angle in the horizontal plane. This is in contrast to first order systems that typically have issues with seated versus standing positions, not due to power response issues but rather their inferior polar response with non-coincident drivers. I don't believe that the non-flat power response to the degree seen with LR crossovers is an issue in typical home listening environments. We may just have to agree to disagree.

>Like it or not, we are influenced by the room boundaries and

>reflections, which are a balance of the *sum* of direct and

>reverberant fields. Even Baranek’s calculations imply that

>listeners are almost always in the reverberant field of the

>room for all frequencies being reproduced, and a

>wide-dispersion loudspeaker is necessary to support uniform

>and flat response in the reverberant field. Most of the AR

>speakers we mention in the forum have wide dispersion, and

>provide good integrated-power response in the typical

>listening room. Yes, we “talk of specs and the flat response

>of AR speakers,” but the reference is made primarily to the

>integrated-power energy of these speakers, which in the real

>world is more important than the simple in-situ on-axis

>frequency response.

Again with your points here we may just have to agree to disagree.

Pete B.

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I'm finding this thread difficult to navigate, so I'm posting this back at the top level. I mentioned what glues I thought were used in the 200003 woofer and confirmation from someone who knows what was actually used would be helpful.

Here's some interesting information on adhesives that are used in modern drivers:

http://www.loctite.com/int_henkel/loctite_...id=318&layout=2

Pete B.

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>

>I've found in practice just the opposite of your theories

>claimed above, that systems with higher order in-phase

>crossovers sound good in most listening postitions. They have

>excellent polar response and the sound does not vary

>significantly in seated or standing positions, or over a wide

>angle in the horizontal plane. This is in contrast to first

>order systems that typically have issues with seated versus

>standing positions, not due to power response issues but

>rather their inferior polar response with non-coincident

>drivers. I don't believe that the non-flat power response to

>the degree seen with LR crossovers is an issue in typical home

>listening environments. We may just have to agree to

>disagree.

>

>>Like it or not, we are influenced by the room boundaries and

>>reflections, which are a balance of the *sum* of direct and

>>reverberant fields. Even Baranek’s calculations imply that

>>listeners are almost always in the reverberant field of the

>>room for all frequencies being reproduced, and a

>>wide-dispersion loudspeaker is necessary to support uniform

>>and flat response in the reverberant field. Most of the AR

>>speakers we mention in the forum have wide dispersion, and

>>provide good integrated-power response in the typical

>>listening room. Yes, we “talk of specs and the flat

>response

>>of AR speakers,” but the reference is made primarily to the

>>integrated-power energy of these speakers, which in the real

>>world is more important than the simple in-situ on-axis

>>frequency response.

>

>Again with your points here we may just have to agree to

>disagree.

>

>Pete B.

Pete,

Yes, definitely, we have two divergent views on what's important in sound reproduction. It's almost like the issue of "realism" in sound reproduction compared to "accuracy" in sound reproduction: Tim Holl (of AR-9 fame) back in the late-70s once said that the goal at AR was *not* to produce loudspeakers that sounded realistic, but those that were accurate reproducers. He felt that an AR loudspeaker should only reproduce a close facsimile of the original program source. Clearly, loudspeaker designers have gone in different directions and there are merits both ways.

--Tom Tyson

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Just came across this site which talks about the "Professional Loudspeaker Reconers Association". I didn't know there was such a thing but I think that they mainly serve the proaudio industry. The reference is at the bottom of the page:

http://www.musicianshotline.com/archive/tech/reconing.htm

Here the writer speaks about the differences between Kapton and aluminum formers. I don't agree with all of the opinions stated here or in the previous link, but he does note a difference:

http://www.musicianshotline.com/archive/tech/reconing2.htm

Pete B.

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Thanks for the information Rich,

Do you know what time frame these drivers are from?

One woofer of the pair I'm working on has a 51 turn voice coil and the other 55 based on my calculations below. I wonder what the story is with this replacement driver with a black anodized former. Was the shorter coil and aluminum former only used for replacement woofers? I'd think that they rebuilt drivers, so it's possible that this driver represented how drivers were being made in the early 80's if that's when it was rebuilt. The question is then if all drivers around that time were made with anodized formers and short coils? Any AR people willing to help out here?

Are there opinions on what people would want in a rebuilt driver to consider what we might want to put into a specification for driver rebuilding? My preference is an aluminum former, black anodized if possible, not sure if I like the resistance getting as low as 2.37, it was on the low side at 2.5.

I'd like to have two matching drivers for this pair, I'll probably look on ebay.

Pete B.

>>>Rich, did you notice if any of the woofers with aluminum

>voice coils were black anodized on the inside?<<

>

>I've refoamed five (5) AR-11 "B" and twelve (12) AR-9 200003

>woofers over the past few years. All with the silver flange.

>

>I'm a "shimmer" when I refoam so I saw the inside of the voice

>coil on all of them when I removed the dust cap. The Aluminum

>VC formers on all the woofers were all silver, none were black

>anodized like the one in your pictures.

>

>The same can be said for all the 10" woofers (pair of AR-90's)

>and 8" lower midranges (AR-90's and AR-9's)I've refoamed --

>all silver Aluminum VC formers.

>

>Rich

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Hey Pete,

In the link you provided there is mention of a "problem" with "magnet half-life" in a speaker more than 20 years old.

I wonder what that translates into relative to the parameters of our 25 to 40 year old AR woofers? We've been wrestling with "if and when" AR increased the magnet strength of the 12 incher. What if we are dealing with an overall net LOSS of magnet strength across the board? What are the likely symptoms of a "magnet half-life" issue? Would it affect alnico and ceramic magnets in the same way?

Roy

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>Hey Pete,

>

>In the link you provided there is mention of a "problem" with

>"magnet half-life" in a speaker more than 20 years old.

>

>I wonder what that translates into relative to the parameters

>of our 25 to 40 year old AR woofers? We've been wrestling with

>"if and when" AR increased the magnet strength of the 12

>incher. What if we are dealing with an overall net LOSS of

>magnet strength across the board? What are the likely symptoms

>of a "magnet half-life" issue? Would it affect alnico and

>ceramic magnets in the same way?

>

Roy, magnets basically do not lose power over time. That is an old-wives' tale -- a wild falsehood. The factors that *do* affect a magnet's strength are: (1) strong electrical currents in close proximity to the magnetic assembly, (2) heat and (3) other strong magnets very close by or in contact with a given magnet. Under normal circumstances there might be a 1% loss in ten years according to what I have read, so maybe a 4 or 5% loss in the 40-50-year-old AR speakers might occur. What does that imply? If anything, it probably just means slightly more bass output at resonance and a fractionally reduced damping at resonance. Your ears will give out long before you would notice the difference.

AR speakers that have been affected slightly by a loss in magnetic strength were the AR-4/AR-4x and AR-2ax-series woofers with Alnico pot-magnet assemblies, subjected to high-power testing and so forth. These magnetic assemblies, with the pot magnet forming the pole piece, were somewhat susceptible to losing magnetic strength over time due to the close proximity of high current close to the magnet itself, but this is the only example in the AR world to my knowledge.

--Tom Tyson

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Hi Roy,

I agree with Tom's comments concerning the magnet issue. You might note that we're finding the magnets to be too strong and we have the measured response by AR as a reference for the original performance.

I posted the links just to raise awareness that there is a "Professional Loudspeaker Reconers Association" and that they're seeing similar issues with the results of the repair work being done. They even mention the difference between aluminum and Kapton formers.

You've probably noticed my posts where I'd like to come up with a specification for rebuilding a classic woofer like the AR 200003.

I've looked into obtaining new spiders for the drivers that I'm working on. I've found that even the best people draw from their supply of old stock parts, even one of the major suppliers considers their stock of parts to be surplus, however they do have new parts for pro drivers. It's up to the driver manufacturer to provide a recone kit and this is done for drivers intended for professional use but commercial companies do not normally do this. No one rebuilding these drivers has the "exact replacement parts" because AR never provided them to the industry. Most spiders are made to order and are not stock off the shelf type parts.

What I thought were part numbers in the NuWay catalog for spiders are die numbers for pressing spiders, there are many materials to choose from and many chemical treatments to produce a finished spider from a given die. There are many combinations for each die number and therefore they're made to order.

Pete B.

>Hey Pete,

>

>In the link you provided there is mention of a "problem" with

>"magnet half-life" in a speaker more than 20 years old.

>

>I wonder what that translates into relative to the parameters

>of our 25 to 40 year old AR woofers? We've been wrestling with

>"if and when" AR increased the magnet strength of the 12

>incher. What if we are dealing with an overall net LOSS of

>magnet strength across the board? What are the likely symptoms

>of a "magnet half-life" issue? Would it affect alnico and

>ceramic magnets in the same way?

>

>Roy

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>Pete, How about sending an old spider to a place like NuWay

>and having them replicate it?

>

>Roy

This came up in my discussion with them, but they normally sell in quantity and I don't want to trouble them if a quantity buy would not happen in the end. I just need 2 spiders and had no plans of coordinating a group buy or handling the prototyping of a new spider.

I might consider it if there was serious interest, that means someone or a group putting up some cash. Sorry to be so blunt but as I'm sure you know people talk and BS, not you in particular.

It also seems to me that most just replace the foam, so who knows if there would be much interest. A new spider might help bring the Tonegens closer to 1970s specifications and this might be a good application for them.

Also note that the closest die from NuWay of the correct dimensions has 6 corrugations. The AR spider has in a sense 7 or 6.5 however half of one is essentially glued to the cone providing a larger contact area. The NuWay spider would have to be installed what appears to be upside down to get the same glue contact area and then if one counts the corrugations on that side there would only be 5. The point being that it is not *exactly* the same, however I do not see this as a problem if the correct compliance is provided. This spider is listed as a 6 corrugation spider however when installed in a way similar to the AR it might be viewed as a 5 or 5.5.

I just checked and the spiders will not fit into the frame upside down due to interference with the inside diameter of the masonite spacer ring so this point of gluing to the cone and loosing a corrugation is moot. The spiders would have to go in normally and be glued in such a way as to get a strong bond to the voice coil alone.

Constructive thoughts are welcome.

Pete B.

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>This came up in my discussion with them, but they normally sell in quantity<

Was quantity or price a topic of your discussion? I don't mind calling them myself, but thought joining the conversation late might just cause a lot of repeated redundancy.

The biggest question I'd have is since the spiders changed over the years, which spider would be the spider of choice? The later 9-spider with a little more power-handling, or the earlier 3a with a lower Fs and a greater tendency to bottom, or the middle-of-the-road 11/10pi? (although early ones of those had slightly different cones that might have been just a tad heavier)

Bret

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>>This came up in my discussion with them, but they normally

>sell in quantity<

>

>Was quantity or price a topic of your discussion? I don't

>mind calling them myself, but thought joining the conversation

>late might just cause a lot of repeated redundancy.

>

>The biggest question I'd have is since the spiders changed

>over the years, which spider would be the spider of choice?

>The later 9-spider with a little more power-handling, or the

>earlier 3a with a lower Fs and a greater tendency to bottom,

>or the middle-of-the-road 11/10pi? (although early ones of

>those had slightly different cones that might have been just a

>tad heavier)

>

>Bret

Please do not call them, the last thing I want is several different people calling them as a result of a post I make here. I want to stay on good terms with them. They do not normally deal with the public, and I was honest about the low volume. On the other hand go ahead if your getting into the speaker business and are able to rebuild a driver and test the Thiele and Small parameters. I'm slowly moving into the speaker business and I don't mind doing the R&D to restore, improve, or design new drivers. I'm actually very interested in being able to prototype completely new drivers so I do have a business interest in this.

Yes quantity came up and he said it's usually something like 5000 units. And we did discuss lower quantities that would involve a setup charge. I'm not sure if I want to get into it on a public forum with you.

I don't know what you mean by joining the discussion? The discussion between myself and NuWay is private between two businesses. If I refine a spider I'll probably ask for it to be exclusive to me because I'm the one spending the time to do the analysis, take measurements, and get it right. I'm probably going to build a simple jig to measure spider compliance. And I'll certainly measure them in several drivers.

As far as your question goes, I'd shoot for an approximate 18 Hz Fs for the 200003 woofer. Fs is really not that important, cone mass is much more important as I've said over and over. The important reason to make the spider stiffer is to return the cone/voice coil to center and to keep the entire assembly from tilting when mounted in the system which can result in the voice coil rubbing. These are very good reasons for having a stiffer spider. I wonder how many here are aware of how important it is for the voice coil to return to the correct zero position, do people know what the result is of a 1 mm offset, especially in a driver with an asymmetrical fringe field? Read here: "Moving Coil Loudspeaker Topology as an Indicator of Linear Excursion Capability", by Mark R. Gander (JBL), JAES 1981 January/February. I'm surprised by how primative the 200003 woofer is given that they had the opportunity to make simple improvements. I'm curious if anyone knows who at AR did the design for the 200003 woofer, and the AR-11 also?

My current thinking is to specify a very loose outer edge suspension and that the cone mass be adjusted if necessary to provide an in box resonance of 40 Hz +/- 2 Hz. A reconer can actually measure the cone/voice coil weight on a scale when they remove it to install a new spider and I will provide an acceptable range. Kind of like blueprinting a motor. I want nominal to be slightly on the low side to allow for a slightly wider tolerance.

This spider could be used with the older drivers and it might result in an Fc of 42 Hz +/- 2 Hz in box due to a slightly lighter cone. I probably would not add mass in this case because these drivers have a lower Bl and more sensitivity would be lost. This assumes that it fits, from a physical stand point and I cannot confirm this until I get one in hand. I think for now we should say that this is just a 200003 spider, if it fits in the older drivers or the Tonegens that's just another bonus. I believe that it should fit all the ceramic magnet 200003 style woofers and if the cone mass is adjusted, and the proper edge used they all should provide an Fc that is within the tolerance range. I'd actually prefer to specify an Fc of 38 Hz +/- 2 Hz for the stronger Bl versions to trade off some sensitivity for bass extension, what do the people think of this?

I can also have voice coils professionally wound to order and my preference is an aluminum former but Kapton is the current standard, not Nomex. Would there be interest in a classic rebuild spec say Kapton former, 40 Hz target Fc, and an enhanced-1 spec aluminum VC former, 38 Hz target Fc for the 200003?

I'd like to do several levels for the Tonegen:

Enhanced-2 spec for 35 Hz target Fc (more cone mass)

and I have other ideas for a better pole piece, inductance modulation reduction, and better VC venting.

The spec should also indicate modifications to provide proper in system Qtc. I may have to work closely with a few specific reconers because there's no guarantee that they'll generally follow a spec.

I don't agree with your theory that the 200003 variations went with specific systems, rather I think it was time of manufacture and parts being used at the time. The woofers here out of 1978 AR-11s have very loose spiders and probably 2 different voice coils. Very early AR-3a woofers probably had slightly lighter cones since the suspensions were more compliant to obtain the same target Fc.

Pete B.

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>I don't agree with your theory that the 200003 variations went with specific systems, rather I think it was time of manufacture and parts being used at the time.<

Pete - I have absolutely no interest whatsoever in getting into the speaker (driver) manufacturing business. The only reason I said something about calling them is that you had said you *were not interested* in being the person to spearhead an attempt to get an order together. I thought the matter was closed as far as you were concerned and if someone didn't follow-up an opportunity might be lost. I hate missed opportunities.

It's hard to stay out of your way if you weave a bunch.

BUT - having said that, I'd suggest that you don't tell us if you have 5,000 "correct" spiders made because some of us might want a few pairs and you're indicating exclusive manufacture for yourself. That might make some people sorta glum.

Or maybe I'm misreading you all the way around. Sorry about that.

Second - Why yes, Pete. Yes, I am aware of what happens to the performance of a speaker when the cone is not returned to the correct 0 position. In fact, you and I have gone over the DUTs where two of them were refoamed with bad spiders and were not returning to the correct 0 position. They stunk-up the place. They rolled-off sooner, were louder, and . . . something else nasty that I don't recall, but I do recall you were doing your best to chalk-it-up to a difference in motor and I was trying my best to reassure you that there was none. Remember the whole "stronger magnet" thing? I'm guessing the measurement you were using to conclude the stronger-magnet theory was caused by the lousy spider sucking the voice coil back into the magnet too much.

Sigh. . . I guess we'll never actually know.

This is one of my "harps" about letting a pro do the re-foaming. Someone who can find "0" and check the doggone spider. If Tom hadn't told me what to look for, poor-old-me would probably have thought the motor was different. I might have even pitched the re-foamed and well-traveled units in the garbage.

Perhaps you are right about my thinking about the early 10pi/11 version of the 200003 being an accident of birth, rather than a design parameter for that speaker. Makes sense. The driver I associate with the 10pi/11 is evident in the brochures for both speakers - the first brochures. The second round, the "B" series with the aluminium badges, have a silver basketed driver. BUT - you correctly point-out that this old black version could have also appeared in the latest version of the 3a, or even perhaps in the LST. I don't know. I do know that earlier 3a's did not use this same cone material and the cone changed along with the basket color for the "B" series speakers.

Still, anything that gets us closer to either of those "era" of spider is a great leap forward. . . so long as you don't hog all the spiders!

I hope you "go for it" and get into the speaker manufacturing business. It'd be nice for there to be another company of quality willing to operate in the good-ol' U.S.A. and put-up with the EPA, OSHA, the wage and hour division of the DOL, IRS, etc, etc, etc, instead of sending the jobs to China where they don't worry so much about that stuff.

Bret

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Pete -

It was *you* who first put-forth the sagging spider theory and Tom reinforced.

I saw the messages again and it was YOU!

Good call.

Sorry to have remembered Tom's comment and not your own.

Bret

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Bret,

I have to wonder if you could have misinterpreted me and jumped to conclusions to any greater degree than in your most recent post. Don't misrepresent my intentions with your assumptions.

I'm not going to respond blow by blow to your post, people should simply disregard it, as it pertains to me, or read what I actually said to see the facts. You suggest that I will get into driver manufacturing, I don't think so, there are many companies who know this very well. It would be foolish so drop the assumptions will you? I may prototype drivers from time to time, for my own use and perhaps for some associates.

Back to the subject, there's been no response to my suggestions for having a spider made so we might as well drop it. I might have had 100 to offer to the group but there is no interest so the point is moot. I would make no money on this deal, just in case your thinking of jumping to more conclusions, given the amount of time I spend on this subject.

You do misinterpret me, over and over.

You dream about what a "pro" reconer does, you might be surprised by the reality.

I explained what happens with an offset voice coil assuming (a reasonable assumption) that perhaps an extended pole piece was used for better fringe field symmetry. You'll have to read the paper to really understand the facts. I doubt you will since it seems that you look only for the "facts" that support your leaps to conclusions based on listening.

I don't have time for this and I don't enjoy this type of discussion at all.

Pete B.

>>I don't agree with your theory that the 200003 variations

>went with specific systems, rather I think it was time of

>manufacture and parts being used at the time.<

>

>Pete - I have absolutely no interest whatsoever in getting

>into the speaker (driver) manufacturing business. The only

>reason I said something about calling them is that you had

>said you *were not interested* in being the person to

>spearhead an attempt to get an order together. I thought the

>matter was closed as far as you were concerned and if someone

>didn't follow-up an opportunity might be lost. I hate missed

>opportunities.

>

>It's hard to stay out of your way if you weave a bunch.

>

>BUT - having said that, I'd suggest that you don't tell us if

>you have 5,000 "correct" spiders made because some of us might

>want a few pairs and you're indicating exclusive manufacture

>for yourself. That might make some people sorta glum.

>

>Or maybe I'm misreading you all the way around. Sorry about

>that.

>

>Second - Why yes, Pete. Yes, I am aware of what happens to the

>performance of a speaker when the cone is not returned to the

>correct 0 position. In fact, you and I have gone over the

>DUTs where two of them were refoamed with bad spiders and were

>not returning to the correct 0 position. They stunk-up the

>place. They rolled-off sooner, were louder, and . . .

>something else nasty that I don't recall, but I do recall you

>were doing your best to chalk-it-up to a difference in motor

>and I was trying my best to reassure you that there was none.

> Remember the whole "stronger magnet" thing? I'm guessing the

>measurement you were using to conclude the stronger-magnet

>theory was caused by the lousy spider sucking the voice coil

>back into the magnet too much.

>

>Sigh. . . I guess we'll never actually know.

>

>This is one of my "harps" about letting a pro do the

>re-foaming. Someone who can find "0" and check the doggone

>spider. If Tom hadn't told me what to look for, poor-old-me

>would probably have thought the motor was different. I might

>have even pitched the re-foamed and well-traveled units in the

>garbage.

>

>Perhaps you are right about my thinking about the early

>10pi/11 version of the 200003 being an accident of birth,

>rather than a design parameter for that speaker. Makes sense.

> The driver I associate with the 10pi/11 is evident in the

>brochures for both speakers - the first brochures. The second

>round, the "B" series with the aluminium badges, have a silver

>basketed driver. BUT - you correctly point-out that this old

>black version could have also appeared in the latest version

>of the 3a, or even perhaps in the LST. I don't know. I do

>know that earlier 3a's did not use this same cone material and

>the cone changed along with the basket color for the "B"

>series speakers.

>

>Still, anything that gets us closer to either of those "era"

>of spider is a great leap forward. . . so long as you don't

>hog all the spiders!

>

>I hope you "go for it" and get into the speaker manufacturing

>business. It'd be nice for there to be another company of

>quality willing to operate in the good-ol' U.S.A. and put-up

>with the EPA, OSHA, the wage and hour division of the DOL,

>IRS, etc, etc, etc, instead of sending the jobs to China where

>they don't worry so much about that stuff.

>

>Bret

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I should probably clarify my thinking as to why a collector might be interested in spiders. I'm thinking that some might want to have the "correct" spider and edge so that they can provide them to a reconer when he works on their driver.

Pete B.

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>Quite some time ago, Tom Tyson entrusted me with an original

>12" to test. I have been embarrassingly remiss in finishing

>that work. Fortunately, an engineer of mine has just

>delivered a big customer project and, prompted by this recent

>thread, I today assigned her with completing the task.

>

>Within a few days, I should have comprehensive data to review.

> I'm travelling until I return from the upcoming AES show, but

>will not drop the ball again. (Or the woofer!)

>

>I hope I can provide a few other technical goodies, too, to

>thank everyone, particularly Tom, for your patience.

>

>-k

>

Hello everyone,

This is Ruchi Goel, Assistant Research Engineer to Ken Kantor at Tymphany Corporation, USA. As Ken had mentioned in the discussion forums, I was given the task to measure AR 12" woofer (12N12100032) sent to him by Mr. Tom Tyson. I am delighted to say that I have finished the task and have the measurements ready to be posted. The link to the measurements is : http://aural.org/ar_hist/AR_OCT05/

Kindly have a look at the data and I will be glad to do any other measurements requested by anyone.

Thank you,

Ruchi Goel

Assistant Research Engineer

Tymphany Corporation

Ph: 408-200-3126

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