tysontom

Dear Steve F, There were several reviews of this series, and one of the better reviews was on the L1290 by Julian Hirsch. The review pretty much speaks for itself, but suffice it to say, Hirsch-Houck Labs was duly impressed by the speaker! If possible, I will attach a copy of that review in PDF format. It is interesting that the 1290 had a 500 Hz crossover and the 1590 had a 350 Hz crossover -- both using the 2-inch dome midrange. I was told by A/D/S/ back in the 80s that the 1590 version had a lower resonance due to a larger cavity under the dome (both drivers were small acoustic-suspension designs!) and some minor changes to the voice coil, I believe. The midrange did not use ferro-fluid, nor was it fused, but the tweeter used the ferro-fluid and had a thermal-resetting fuse link. I agree: these were superb loudspeakers, and I owned a pair of 1590s (which I now have back -- see images in prior message) that I bought new. Prior to the 1590s I owned AR-9s; after the 1590s I had KEF R107s, then B&W 801 Matrixes. The 9s had the bottom-end pretty well covered, but not greatly better than the 1590s. The 107s were the best in very deep bass, however, but too directional in the midrange for my tastes, over time. The 801s were great, but the bass was less-well defined than the others. Some of my best memories were of the 1590s! --Tom Tyson

The L1590 was a 1980's speaker held in high regard for its uniform on-axis output as well as it's relatively flat acoustic-power output, the downfall of so many loudspeakers. The acoustic-power frequency response is basically the integrated power output of a transducer as measured throughout a listening environment, and is a measurement of the speaker's abillity to disperse sound over a wide vertical and horizontal axis. The end result was a speaker that was capable of great accuracy and realism, as well as a speaker with very "spacious" sound characteristics. The L1590 also had very low distortion and excellent deep-bass capability with its two 10-inch acoustic-suspension woofers mounted in separate chambers within the heavily braced cabinet. The -3 dB point of this speaker was approximately 28 Hz, so the low-frequency extension was also excellent. Power-handling for the woofers was top notch with the 2-inch-diameter voice coils with 1.5-inch high windings, giving greater than .5-inch linear overhang. Subjectively, earlier versions of the tweeter used A/D/S/ was considered to be bright sounding, but A/D/S/ made changes to the crossover and the magnet structures on this vintage of the speaker, and the L1090, L1290 and L1590 were a bit more reticent than earlier models. --Tom Tyson

Dear Minh, I’ve been away for a few days, so I’m just now getting back to check messages, etc. I have commented below on your post regarding the Amati. [You said] “I am going to break apart you post and answer to what you said and hopefully this will clear up the misconception of people who have a hard time understanding the Cello Amati speakers.” [You said] “No problem, I don't get upset but willing to listen and learn if there is anything I had missed? I want to find out where the discrepancy was! I would like to present what I know and to set things straight so to stop the people who love to copy what you said and spread the wrong info to mislead others.” Minh, I know you are passionate about the Levinson-Amati speakers, and that is great. There is no intention whatsoever on my part to “mislead others or spread the wrong,” as you say. But in my opinion, the original price of the Amati speaker (wasn’t it between $10,000 and $15,000 per pair at the time?) was excessively expensive, especially considering the performance level, which may or may not have been lower than the AR-LST. Even the Amati speaker stand ($5,000 I believe) was more than four-times as expensive as the original AR-LST speaker pair! How can that be justified? I have *never* seen response graphs or objective test reports on the Amati speaker -- so I would simply ask you to provide whatever evidence you can give that the Amati was equal to or an improvement over the AR-LST. As you know, the LST was tested extensively in AR’s reverberant and anechoic chambers, and its performance was quantified with results that were widely published throughout the world. Its level of performance was therefore established over time, not merely by people bragging about it, but by objective reports and measurements. A lot of people did not like the LST, and it had its share of criticism, but at least it was tested and measured carefully. I don’t recall ever seeing a single test report or response graph on the Amati or the Amati Pro, and that is where I ask you to help me out by supplying some documented evidence of that speaker’s performance. [You said] “The Cello Amati speakers have never used stock AR-10Pi/AR9 coated soft dome tweeters since day one but instead they were special ordered paper dome tweeter with butyl latex/coated fabric suspension with embedded ferro fluid for high power handling but with the off-axis dispersion characteristic of the original AR-3a tweeter. The midranges were ferro fluid filled as well compare to the none ferro fluid filled midranges in the original AR-LST therefore the Cello Amati speakers actually can handle even higher power than the original AR-LST speakers and the dispersion characteristic is basically the same for both models. The later Cello Amati Pro also used 3/4" coated soft dome Dynaudio tweeters (not the larger 1"+ tweeter as you may think, see attached photos for the difference) so to preserve as much of the dispersion characteristic as the AR drivers Amati but the crossover were totally changed due to the introduction of the more expensive Dynaudio drivers to kick it up a notch.” I guess I stand corrected on the issue of the tweeter used on the first Amati; it looks very similar to the “B” generation AR-10Pi/AR-11 tweeter. However, it would be helpful to me to see a high-resolution image of this tweeter (close-up) to see how the paper dome was integrated with a cloth suspension, as you describe. By the way, the second-generation Amati Pro ¾-inch coated soft-dome Dynaudio tweeter is inferior in dispersion to the hard-dome AR-3a-style tweeter for two reasons: 1) soft-dome designs don’t respond as well off-axis as hard-dome tweeters and 2) the Dynaudio tweeter is recessed in a small “semi-horn” type appendage which enhances on-axis efficiency at the expense of off-axis response. The soft-dome “semi-horn” approach isn’t wrong, per se; it is the modern way to manufacture dome tweeters these days, as dispersion is less important to contemporary speaker-driver engineers as on-axis sensitivity. For Levinson to “kick it up a notch,” makes me wonder why you would want to take a basically flat-response speaker (the original AR-LST) and make it even brighter. Does that make it more accurate? The definition of accuracy is the faithful recreation of the original sound, not adding to or subtracting from the original program source. [You said] “I imagine these insiders must be hard cored Roy Allison followers and will not give Mark Levinson any credit but making judgement based on their personal believe and what they think. I used to be one of these people myself for many years but eventually feel I should let go my blind following and personal assumption but to find out the real truth. But then I could be wrong about this so please let me know who said that if you don't mind!” The comment regarding the LST’s performance compared to the Amati was made during one of the long-past Chicago CES Shows by a respected industry insider and a member of the Boston Audio Society, but I have *no* intention of naming any names! The comments were made “off the cuff,” and were only comments of people who had made comparisons of the AR-LST and the original Amati speakers. I felt the comments had credibility, but I never thought much more about it. [You said] “Is the b&w AR-LST picture shown the picture you mention about Victor Campos experiment of soft dome tweeters on the AR-LST? This is a technical drawing and beautiful rendering but not a true photograph at all. Hopefully Victor Campos can tell us what he did or had found out in the experiment with the AR-10Pi tweeters on the AR-LST speakers if such test had been done?” No, you are looking at the wrong picture (see attachments). --Tom Tyson

The tweeters, midranges and 10" woofer with step down adapter are all Allison drivers. What are they doing in the Cello Amati speakers, I have no idea and it would be nice if the original owner who modified these speakers can explain his purpose and personal believe... Minh Luong Dear Minh, The only reasons I could imagine anyone making this type of alteration would be to (1) improve the already superb dispersion and (2) increase the already prodigious power-handling capability of the LST/Amati. The only peculiar thing is the use of that woofer which, by the way, does not appear to be an Allison woofer. Nevertheless, I believe that the Allison tweeter is the only tweeter ever made that can outperform the AR-3a 3/4-inch tweeter with respect to off-axis dispersion. I think the midrange is somewhat better off-axis than the AR-3a, and can also be crossed over at significantly lower frequency (375 Hz). The Allison tweeters had a "pulsating" characteristic that made radiation from the edges of the diaphragm somewhat asymmetrical, and thus there was increased output from the “flexing” nature of the edges of the diaphragm (refer to US Patent No. 4,029,910 “Wide Dispersion Loudspeaker with Flexing Diaphragm.” I’m not sure if this patent went forward). On the other hand, I don't think the Allison drivers were better performers, overall, than the AR drivers with regard to transient response, distortion and flatness of response. The AR-LST (not necessarily the Cello Amati) had such wide dispersion that to use a tweeter with even greater off-axis extension doesn't seem particularly rational, and to down-rate the woofer from the potent 12-inch AR woofer to a 10-inch version makes little sense, particularly in a 2-Pi setting. --Tom Tyson

>I seem to remember the KLH Model 4 from an old Lafayette >Radio catalog as a 2 way 12" acoustic suspension speaker >system somewhat larger than Model 6 but looking very much like >it externally having the same open weave off white grill >cloth, same KLH logo badge in the corner. I never actually >heard a pair. The library spread sheet says it had 2 12" >woofers, I thought it had only one. (You'd think with 2, it >would need a much larger enclosure like AR9.) It was priced >about the same as AR3 and was intended to compete directly >with it. The data on the spread sheet says KLH Model 5 was >produced from 1968 to 1972 as was the Model 12. That's how I >remember it also. I guess it's a little strange for the >models 4 and 6 to both predate model 5 but I'd never heard of >Model 5 until the late 60s. I do recall model 9 early on and >I heard it at an IHF show at the Trade Show Building in NYC >just around 64. At the time, some people considered it the >state of the art. Thanks, Soundminded. --Tom Tyson

>Tom, > >Check with Roger, the October 1958 issue of High Fidelity is >listed as having reviews of KLH models One, Two, Three, Four >and Five. > >That sounds like one to get a copy of, you don't hear much >about the scarce Model Five high frequency unit. > >Andy Andy, thanks for this information. I think I might have that review now that you mention it. It was more of a listening evaluation and description than an actual review if I remember correctly. --Tom Tyson

Carl, Thanks very much for your information on the KLH Four. I know Roger Russell, so I should ask him. However, I am not aware of an actual magazine review of the Four, such as in *Audio,* *Stereo Review* or *High Fidelity.* Consumer's Union did evaluate the speaker, and it was in the top rating group, just below the AR-3 and AR-2a. Since the Model Four was a 16-ohm speaker, well-suited to high-power tube amps, but inappropriate for high-current, solid-state amps, it died sooner than expected. None of the big solid-state amps put out significant power into high impedances. For example, the AR Amplifier would put out over 90 watts/ch into 4 ohms but only about 30 watts into 16 ohms. That is enough to drive the speaker okay, but I always heard that one needed something like a McIntosh MC275 or Marantz 9B to really make the speaker perform to its maximum. --Tom Tyson

Does anyone have information on the original Model Four? I'm trying to find any test reviews on this speaker. I have some historical data, but no test reviews. I'm not sure if the speaker was formally reviewed, but I do not know. --Tom Tyson

>Then I went to pull out the pot and it is fried! >Really! Melted! Check it out >Kent Even though this speaker is many years beyond its warranty, this is a classic example of one of the few exceptions to the AR "Full-Five-Year-Warranty" rule. AR would take care of just about anything -- and pay the shipping both ways -- but when something came along that demonstrated acute and grevious abuse ("accidental or otherwise") such as the melted, burned-out level control, AR would make the customer pay for repairs and would not reinburse for shipping. AR even repaired my lightning-damaged AR-3as at no charge (I still have the pair), but the company would not repair damage caused by obvious abuse to its products. --Tom Tyson

> >These drivers have accordion edges, which I don't believe is >correct: > The term "Fs 18Hz" is definitely written by someone after the woofers were manufactured because of "Fs" and "Hz." Neither of these terms was used in the 1950s. The 18 Hz value is correct for this woofer. The first AR woofers with sand-cast frames also did have "pleated" surrounds, which was not shown in Villchur's patent. His patent shows the half-round surround, but Henry Kloss felt the pleated surround would work better since it was the conventional method of the day. Therefore, Villchur decided to compare the harmonic distortion of woofers with both the pleated surround and the half-round surround, and the once that had lower distortion would set the rule. After the initial production run of AR-1s and AR-1Ws, the pleated surround was changed to half-round. http://www.classicspeakerpages.net/dc/user_files/679.jpg Very large file on AR-1 Ser. No. 0006. Shows the pleated surround. Skiver masonite has separated, but underneath the hand-made voice coil can be seen. >I believe that these woofers have been worked on and the 18 Hz >figure was measured after the repair. The surrounds have been treated with some material, but the pleated surrounds are original. --Tom Tyson

>Just wondering if this picture is of the current woofer that >we have test data for: Tonegen 12N12100032. It doesn't look >like the Tonegen currently being sold, rather it looks like a >200003 type. > >Pete B. Pete, I'm not sure who supplied that AR woofer in Ken's Klippel test jig, but I can tell that it was an earlier 200003 or 1210003 factory woofer that had been repaired with a new surround. It might have been one of Bret's woofers; I'm not sure. It is not the Tonegen version. Incidentally, I plan to send (to Ken) an earlier AR-3/AR-3a PN 3700 Alnico woofer and an early AR-3a ARNP 200003-0 woofer recently refurbished with a new 5/8-inch surround. Regarding surrounds, I use Speaker Works Northwest surround kits with satisfactory results, although I am sure there are numerous other good suppliers of the proper surround. These Speaker Works surrounds are similar to samples I received from Minh Luong a few years ago that had the proper 5/8-inch half-round size and the angled-inner flange. http://www.speakerworks.net/ Description: "11-inch Acoustic Research Angle Attach Surround Kit." Price is $24.00 per set, with a small discount for larger numbers. Unfortunately, the kit is incorrectly labelled as an "11-inch" surround, but I guess it's too much trouble to change the description at this point. Despite the incorrect description, the surround kit works very well in my experience. Shims are not supplied nor are they recommended, and the dust cap is left alone. Slow-drying glue is used, similar to white glue, and this method works the best in my opinion. --Tom Tyson

>>Hi Ruchi, >> >>I was just wondering if you tested the woofer face up, down, >>or in a vertical position? >> >>Pete B. > >Hello > >The inbox measurements were done in the vertical position and >Klippel measurements were done with the woofer mounted in the >Klippel stand and laser pointing to center of the woofer. > >Kindly let me know if that answers your question. >Thank you >Ruchi Pete, With the woofer mounted in the enclosure, it probably makes no difference whatsoever how the enclosure is pointed. Even in free air it probably doesn't matter that much, but I would think that vertical mounting, such as the Ken's Klippel setup below, would be the norm. http://www.classicspeakerpages.net/dc/user_files/677.jpg Klippel test jig with AR 12-inch woofer (Ken Kantor) --Tom Tyson

>Just a quick note... > >1- I only got one woofer with this shipment. > >2- My site is hosted by Verio and Florida, and has been >impacted by the hurricane. As such, people might find access >to the data intermittent. I would suggest that Mark move the >data over to CSP. > >-k > Ken, You are correct. I only *thought* I sent two woofers. I actually shipped the Tonegen woofer with the cabinet, and I did not get around to shipping the early Alnico 3700 woofer. I will do that, in addition to a 200003 AR-3a ferrite woofer. Sometimes I think I might be having short-term memory loss. Sometimes I think I might be having short-term memory loss. --Tom Tyson

>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 > 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 Ruchi, Thanks so much for performing these tests for us. Once again, we are greatly indebted to Ken and Ruchi for this work! Great job! I sent a “test” enclosure, which was a standard 1.7 cu. ft. AR-3 box, and I set the crossover so that the woofer could be tested with or without the crossover coil in the circuit. Other parts of the crossover were disabled. After all, this is a test for the low-frequency characteristics of the various AR 12-inch woofers. The midrange and tweeter drivers were removed and the holes filled. I was very careful to make sure that the enclosure was acoustically air-tight, and the enclosure fiberglass was the “standard” weight and density for an AR-3 or early AR-3a, but this could be altered if needed. If I remember correctly, I sent along with the enclosure (1) Tonegen PN12100032 woofer and (2) and early Alnico PN 3700 woofer, although I am not now sure I sent the latter. The one Ruchi tested would clearly have been the Tonegen, and you can see from the response curve that there is close correlation with 2Pi tests that AR did outdoors when testing the Alnico (PN 3700) and ferrite (200003/1210003) woofers. I am going to get an early AR-3a 200003-type woofer (with the proper 5/8-inch surround) out to Ruchi to test, and from that we can see how the different, mounted woofers perform. Thanks again, Ruchi! --Tom Tyson

>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

> >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

>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

>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

>Hi there > >Another 2 1/2 cents worth from me now. > >Have you tried, Acetone, which is similar to lacquer thinners, >for softening the spider glue? > >That is all I've ever seen used up here. > >All safety procedures must be followed, read the safety >haszard sheet, this stuff is not for inhaling. > >I have seen a spider come off in about 30 seconds once the >glue is dampened. > >Just use a 1/2" wide paint brush to apply it. > >Good luck. Vern, I haven't tried acetone on the AR parts, but it's probably a great chemical to use. Ironically, I use acetone and lacquer thinner on a pretty regular basis on other projects, but I've never tried them on the AR speaker glues! I think I was surmising that acetone would damage urethane-foam materials; but after all, there is no surround to dissolve at this point! Both acetone and lacquer thinner are very volatile and flammable, so you have to be very careful with them. Thanks for the suggestion! --Tom Tyson

>>>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.<< > >Tom, I believe you are right about when AR changed from Nomex >to Aluminum voice coil formers. When AR changed the ADD line >from what we on the forum have referred to as "A" model ADD >speakers -- Brass logos, White/yellow fabric on tweeter, black >screen on midrange... The 200003 woofer was the same as that >used in the AR-3a and AR-LST -- Black flange, wide masonite >ring, hex screws... > >I have my Dad's AR-11 "A's" here with me. I just pryed up a >small portion of one woofer dust cap (a replacement porous >dustcap installed by a shop he had refoam the woofer for him, >it isn't glued down very well) -- > Nomex VC former, just like the AR-LST woofers I refoamed a >few years back. > >All the AR-11 "B", and AR-9 200003 woofers I've refoamed are >the silver flange version -- all have Aluminum VC formers. >Pretty good indication this is when the change from Nomex to >Aluminum was made. > >>>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.<< > >Just to add my techniques -- > I've used "Goof Off" and Isopropyl alcohol to loosen the >glue. The alcohol works better than the Goof Off. I use Q-Tips >saturated with alcohol to "scrape" the foam remnants away >before going after the glue. > >The best tools for scraping the glue from the masonite ring >and the outer edge of the cone are razor type knifes -- >X-acto, Stanley retractable blade knife, Box cutter/Wallpaper >razor knife with break-off blades. Whatever type knife you >use, use the BACK OF THE BLADE (not the sharp edge) to scrape. >You will not cut the cone or damage the masonite when you use >the back of the blade. > >>> It's slow, laborious work, but a clean surface is mandatory >for good results.<< > >Absolutely. > >Rich Rich, Excellent message and great advice on the techniques for scraping the glue, etc. I think that "Goof Off" (what a ludicrous name) is xylene, but I'm not sure. It is good for removing label residue without damaging the surface. It all goes to demonstrate that the glue that AR used was not water-based, and some chemicals need to be used to improve the operation. Thanks, --Tom Tyson

>This was the second woofer that I've been referring to as #2 >and it has the red service replacement tag, here's what I said >about it: > >"The second woofer (#2) was damaged when driven with excessive >power (300W), and the voice coil rubs in such a way that the >cone sticks wherever you leave it. ... It is marked: 561 7838 >and has an RDC of 2.37 ohms." > >I'll try to post those pictures soon. I'm working on cleaning >off the old rotted foam and glue from the frame and masonite, >anyone have suggestions for a good way to do this? Any >suggestions for a solvent? > Pete, 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

>The foam from RSSOUND arrived today with hand written answers >to my questions on the receipt. Seems they mainly do business >with large customers, but also provide this semi-automated >service for small customers. The foam looks like a good fit >and is 5/8" wide which I believe is correct for this woofer. > >I unsoldered the lead in wires on woofer #2, unglued the >spider which allows the entire cone, spider, and voice coil to >come out as a unit. The voice coil has a tarnished bronze >look on the outside top near the cone, the appearance on the >inside is black anodized, and the edge has a silver aluminum >color. I believe the former is aluminum but I can't explain >the bronze look on the outside. The voice coil did bend in >and the windings are in perfect condition. I was able to >flare the former back out and it should be fine. >I notice now that the spider is stretched at high excursions >and I believe this is what causes the floppy spider that some >people mention. The spider was also starting to come unglued >where it meets the cone/voice coil joint. I believe this was >also caused by over excursion. > >Pete B. If possible, please send images of this speaker assembly, including both front and back views of the cone and voice-coil assembly. Which vintage 200003/1210003-series was this, date code, etc.? I could go back and look at your earlier message I suppose! I am curious to learn when the aluminum former was put into use; it may have been earlier than I originally thought. Most earlier versions had the paper-nomex former, well-known for its resistance to high temperatures. There were definite differences in spider compliance between earlier and later versions of the 12W, but a stretched spider will simulate a loose suspension as well. Incidentally, the earlier Alnico AR woofers (PN 3700) used phosphor-bronze formers exclusively, but this substance is expensive and somewhat heavy. The 3700 also had a slightly longer coil in practice than the 200003 woofer, but only a millimeter or two. When the 3700 woofer reached its excursion limits, it would not hit the back plate, but rather it would tend to loosen the bond between the voice coil and cone. --Tom Tyson

>Hi Tom, > >I'll weigh them at some point if I get a chance. The former >must extend past the windings somewhat as with most voice >coils, do you know what that dimension is? > Pete B, To answer your question, there is about a millimeter or two above the coil winding, and quite a lot below the windings. The voice coil is 2-inches in diameter and about 1.02 inches in length. Following are images of two damaged AR#200003 voice coils: http://www.classicspeakerpages.net/dc/user_files/616.jpg (1) This AR-3a voice coil was bottomed during strife-testing, and the nomex former and coil suffered slight damage at the edge where the coil touched the back plate in 1+ inch excursions during sine-wave testing. http://www.classicspeakerpages.net/dc/user_files/617.jpg (2) This AR-3a voice coil was heavily damaged by extremely high power at low frequencies, causing the coil to compress the former when the coil hit the back plate violently. This coil bottomed repeatedly before deforming the bobbin. --Tom Tyson

>The plot thickens, different magnet diameters. > I've been thinking >that I should measure every dimension on each of these woofers >but did not get around to do it. I did put them down side by >side and what do you know, one magnet has a larger diameter, >enough that it's easily seen by eye. Here are the pictures: > >Woofer #1 on the right in the top picture, left in the bottom >picture is obviously larger, that is not a shadow in the >picture. Woofer #2 has a red tag stating: "Service >Replacement Unit For Further exchange the original purchase >Bill of Sale required" As I understood it the woofers had >never been replaced, does this tag indicate that it is not the >original woofer? I'll have to check with the original owner >since he has a good memory of what went on with these >speakers. >Woofer #2 has a magnet diameter of 6.04 inches, while woofer >#1 does not fit inside the caliper which stops at 6.185", I'd >say it's about 6.2". >I measured the thickness again Woofer #1 is right on the money >at .75" if not .751", while Woofer #2 is over .74" but closer >to .74 than .75". This is starting to split hairs but clearly >woofer #2 has a smaller magnet. The back plates are both >5.5". > >Woofer #1 is the one that did not fail and it would tend to >have less bass excursion due to the stronger damping and >reduced output in the low bass. > >It's also interesting to note that the woofer that seems to be >original is the stronger version, when the literature states >that the AR-11 should have the weaker driver. Knowing what >goes on in engineering and production this doesn't surprise me >- the stories I could tell. > >They probably used more than one supplier for magnets. Any >other theories? > >I'd appreciate it if others could measure the diameter of the >magnets and report back. Dimensions of the square magnet >version, and the top and bottom plates would also be helpful. Pete, The outside diameter of the magnet being slightly different probably is a reflection of different vendors, particularly in view the relatively small differences you noted. I don't know how many suppliers AR had for magnets, but probably quite a few, as most manufacturers usually have two or three prime vendors for critical parts. Because of different manufacturers, it is also possible that the inside diameter of the magnet was sufficient to offset the different outside diameter. The square magnet is a good example. By the way, did you *weigh* the representative drivers, taking into account that the frames for all the 200003-series woofers are nearly identical, but with only superficial differences in the cones themselves? Determining the weight of the magnetic structure -- which should weigh around 10 lbs or so -- might be a closer indicator of different magnet structures. I honestly don't believe that there was a difference in that series, but I can't be sure. I can assure you that the top and bottom plates on every AR 2000003-style woofer are .5 inches, as the two-inch diameter voice coils in all these speakers are one-inch in length, +/- a millimeter or two, allowing for the designed .5-inch voice-coil overhang. Maximum linear excursion was one-half inch, and maximum excursion before bottoming was a little over one inch. --Tom Tyson