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ADS L1590

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Gerry,

That big, broad front baffle board on the ADS 910 seemed to be in vogue briefly during that time (another example was the Andy Kotsatos Boston Acoustics A100 with the wide front face), but I would think there would be interference effects on a grand scale if the speaker were measured in the near field—again, not a big factor in the reverberant field. The later ADS tower speakers—especially the late-80s L Series 2 versions—were narrower and had significant improvements in dispersion and acoustic power over the 910 series. This acoustic power might be unimportant to some such a Speaker Dave, but it seemed to make the newer "L" speakers more three-dimensional. I really don't know if there were changes in the so-called "imaging" of the speakers, but overall the (especially the 1590) towers were considered better performers.

--Tom Tyson

Tom (and former ADS engineers). I always wondered why they never "mirror imaged " them, especilally since they were "studio monitors". I know that they were "reverberant field" speakers, but still !!!!. Other "classical music" monitors of that period (KEF & B&W) did pay attention to imaging in the near field as well as diffraction issues. The grilll that came with them was reminiscent of the AR3a inset driver mounting with a big lip overhanging the baffle. At least the 910 grills were removable.

I must say that the 910's were my biggest "high-end" dissapointment of all the speakers I've owned. Given the superb and expensive "build quality" of this model, a miirror imaged pair shouldn't have been that costly to make. Heavy MDF consruction, well braced,seperate chambers for each woofer, industrial grade printed circuit board and crossover components, fuses for each driver, etc.

I can't help but wonder why they didn't go "alll out" to address my "minor quibbles" like imaging.

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Tom (and former ADS engineers). I always wondered why they never "mirror imaged " them, especilally since they were "studio monitors". I know that they were "reverberant field" speakers, but still !!!!. Other "classical music" monitors of that period (KEF & B&W) did pay attention to imaging in the near field as well as diffraction issues. The grilll that came with them was reminiscent of the AR3a inset driver mounting with a big lip overhanging the baffle. At least the 910 grills were removable.

I must say that the 910's were my biggest "high-end" dissapointment of all the speakers I've owned. Given the superb and expensive "build quality" of this model, a miirror imaged pair shouldn't have been that costly to make. Heavy MDF consruction, well braced,seperate chambers for each woofer, industrial grade printed circuit board and crossover components, fuses for each driver, etc.

I can't help but wonder why they didn't go "alll out" to address my "minor quibbles" like imaging.

Gerry,

At least the 910s (as well as the later 90-series towers) were vertically aligned. Perhaps "mirror-imaging" might have very slightly improved performance, but considering how Dr. Guenther did things back in those days—and being the resourceful German that he was—he likely dismissed a design change that could not be warranted, but this is a total assumption on my part. Guenther did pay great attention to detail, and ADS speakers always reflect those engineering details, but some things weren't necessary. Nevertheless, the 910s were certainly designed for high-output, far-field acoustic power necessary for studio work during that period. With such wide dispersion, especially through the lower midrange, it would be hard to get imaging such as with some other speakers with 4-5" midrange drivers (such as the KEF and B&W designs). Up close, I thought the speakers did seem a bit bright—and perhaps that was what you didn't like about them—but back in the reverberant field, I felt the balance was pretty good, and the speakers had a definite three-dimensional sound from what I remember back several years ago. I do vividly remember that the speakers could pump out a high SPL output, and one day (at a dealership called Soundhaus Stereo in Chapel Hill, North Carolina) I heard them being powered by a McIntosh MC2300 driven to peak output, and I was amazed at how clean and clear the sound was at such a high-output level. There was none of the usual strain you hear with speakers as they begin to compress. Perhaps this was one reason some studios used this speaker as a monitor. As for diffraction, the front panel was pretty flush and clean, and I suspect that studios did not operate the speakers with grills in place. Even so, diffraction was pretty much swamped in the far field anyway.

It is noteworthy that Guenther used separate chambers for dual woofers all the way back to the 30-series in the early 1980s, and this continued with the lower-cost 810 model during the mid-1980s. This had to be considerably more expensive to manufacture, but according to ADS, this design improved bass performance considerably, and it was used in most of the other top-end ADS designs. The quality-of-construction and attention-to-detail of ADS speakers was definitely set to a high standard.

--Tom Tyson

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Update on the ADS L1590-2 woofers: the following images are details of the construction of the dual-10-inch woofers used in the L1590-2. The voice coil is coated with a special high-temperature coating, and the coil is wound on a special Kapton former for excellent power-handling capability. The coil is 2-inches in diameter. The cone is a special-density pulp mixture engineered by ADS to prevent breakup distortion, and with the very low crossover frequency, the woofer's output is very uniform down to -3dB point of 28 Hz, with natural rolloff below that frequency. There is usable response down to 20 Hz and below at fairly high output levels.

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Fig. 1: Inverted view of high-output 10-inch ADS Stifflite Woofer used in the L1590-2

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Fig. 2: Detail of the conformal high-temperature coating of the 2-inch diameter, long-throw ADS L1590-2 dual 10-inch Woofers

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Fig. 3: 2-inch Diameter Voice Coil used on the ADS L1590-2 dual 10-inch Woofers

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Fig. 4: Detail of the cross-section of the special felted cone assembly of the 10-inch ADS L1590-2 Woofers

--Tom Tyson

I actually WOUND these voice coils in their Wilmington ,MA facilities. I distinctty remember that black "goop" coating; a devil to work with. DCR tolerances were extremely tight (at least mine were). When I owned the 910's, never blew a driver despite using them for hard-rock & disco playback @ high SPL. My amp at the time was a Dunlap- Clark Dreanaught 1000 (rated @500 watts/ channel into 4 ohms from 20 -20 Khz CONTINUOUSLY) ! Think my ears became "non-linear" before the speakers did !

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I actually WOUND these voice coils in their Wilmington ,MA facilities. I distinctty remember that black "goop" coating; a devil to work with. DCR tolerances were extremely tight (at least mine were). When I owned the 910's, never blew a driver despite using them for hard-rock & disco playback @ high SPL. My amp at the time was a Dunlap- Clark Dreanaught 1000 (rated @500 watts/ channel into 4 ohms from 20 -20 Khz CONTINUOUSLY) ! Think my ears became "non-linear" before the speakers did !

Gerry,

When I first got my 1590s I hooked them to my McIntosh MC2500 amp (a full 750 watts rms/channel continuous), and drove them quite hard playing some Telarc recordings on numerous occasions -- sometime to maximum peak power (Power Guard clamping the output on several occasions) -- but I never blew a fuse or damaged any drivers. It was so loud as to be uncomfortable, and the fact these speakers survived this ordeal is probably indicative of the high levels that could not be tolerated for too long! Those two big fans on the back of the Mac would light up and run hard on occasions, indicating a lot of current was passing through the outputs! ADS speakers tend to be durable; however, an underpowered amp clipping badly will always cause problems and can easily destroy a tweeter. Ironically, later Type 2 L1590s and L1290s did away with some fuses, as they were deemed unnecessary.

The Dunlap-Clarke Dreadnaught 1000 was a fine amplifier, and it was originally used in the mid-70s AR-10Pi Live-versus-Recorded demonstration with Neil Grover as drummer. Steve F attended some of these concerts. As long as it was not stressed too much, the 1000 could power anything. The peak-power outputs were so high for so long during the AR demonstration (800-1000 watts peak-per-channel into the AR-10Pi speakers) that the event eventually destroyed the amplifier, and AR (Victor Campos) eventually used another similarly powerful amp for the demonstrations. As I sit here now in my office, I'm listening to that exact pair of AR-10s that was used during the LvR demonstration.

--Tom Tyson

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Tom, I never blew a 910 fuse either. I do remember the Dunlap-CLark "VU" meters "dimming" significanty when I "clpped them". The meters weren't "true" VU meters because their ballistics were a bit slower than what's called for. still good enough though ! At the "-20 db" level meter setting, 0 to +3 db "average" readings would clip the Dreadnaught. Strangely enough, none of the fuses on the amplifier blew either. And if the fans did come on , it was a very rare occurance. I actually owned TWO Dreadnaughts. When they eventually failed , it was an output transistor.

I actually used the Dreanaught to develop the "improved" BA towers and found the Dreadnaught invaluable; revealed some critical performance criteria i wouldn't have noticed if I used the amps BA had in the labs at the time (big Adcom and NAD amps). But that's another story.

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Gerry,

When I first got my 1590s I hooked them to my McIntosh MC2500 amp (a full 750 watts rms/channel continuous), and drove them quite hard playing some Telarc recordings on numerous occasions -- sometime to maximum peak power (Power Guard clamping the output on several occasions) -- but I never blew a fuse or damaged any drivers. It was so loud as to be uncomfortable, and the fact these speakers survived this ordeal is probably indicative of the high levels that could not be tolerated for too long! Those two big fans on the back of the Mac would light up and run hard on occasions, indicating a lot of current was passing through the outputs! ADS speakers tend to be durable; however, an underpowered amp clipping badly will always cause problems and can easily destroy a tweeter. Ironically, later Type 2 L1590s and L1290s did away with some fuses, as they were deemed unnecessary.

The Dunlap-Clarke Dreadnaught 1000 was a fine amplifier, and it was originally used in the mid-70s AR-10Pi Live-versus-Recorded demonstration with Neil Grover as drummer. Steve F attended some of these concerts. As long as it was not stressed too much, the 1000 could power anything. The peak-power outputs were so high for so long during the AR demonstration (800-1000 watts peak-per-channel into the AR-10Pi speakers) that the event eventually destroyed the amplifier, and AR (Victor Campos) eventually used another similarly powerful amp for the demonstrations. As I sit here now in my office, I'm listening to that exact pair of AR-10s that was used during the LvR demonstration.

--Tom Tyson

Senior moments come and go. While it's still in my head: "another similarly powerful amp for the demonstrations" was (I think) a Luxman M4000. The Dreadnaught cost me $1500....very industrial looking. The Luxman cost several times that....more than the car I owned at the time. It almost weighed as much too..LOL :)

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Senior moments come and go. While it's still in my head: "another similarly powerful amp for the demonstrations" was (I think) a Luxman M4000. The Dreadnaught cost me $1500....very industrial looking. The Luxman cost several times that....more than the car I owned at the time. It almost weighed as much too..LOL :)

Gerry,

You were close: it was the Luxman M-6000 dual-mono (monoblock) amplifier that was used with the AR-10Pi speakers in the Neil Grover live-versus-recorded demonstrations. I think that the Dreadnaught was preferred by Victor Campos because it was "manageable," but it failed along the way. The Luxman weighed over 115 lbs. Ironically, the Luxman was rated for 8 ohms and not 4 ohms, yet it could power the 4-ohm AR-10s easily without shutting down. The M-6000 was a also very expensive, limited-production amplifier that was not mass-produced. Just think that if they had amps such as the QSC PLX-3602 or the big Crown Macro pro amps (5002v or whatever it was), doing a high-power LvR would be a breeze!

--Tom Tyson

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Several questions have been raised about differences between the mid-1980s "Series 1" and late-1980s "Series 2" ADS speaker models. The following information is adapted (and paraphrased) from some internal and generally published ADS material and manuals. It outlines in some detail the changes from "Series 1" to "Series 2" that were made to the ADS models L470 up through the L1590 flagship tower loudspeaker, subject of this topic.

Series 2 Changes:

ADS made a series of significant engineering changes to the "L" series loudspeakers (L470 through the L1590) in the 1987-1988 period that resulted in improvements in smoothness, power-handling capability and lower distortion. Improvements were made to crossover networks and driver components themselves. For example, the new version were called "L1290 Series 2," or "L1590 Series 2." Original series were simply "L1290" or "L1590," but were referred to internally at ADS as "Series 1."

These changes came about as a result of new computer modeling techniques, such as FFT measurements, that allowed ADS engineers to enhance product performance and durability. Another reason for the improvement came about due to concerns about reducing coloration and distortion in the midrange area. Since ADS speakers were already critically acclaimed for excellent performance in smoothness, off-axis response and low distortion, this improvement was further indication that ADS was very serious about making state-of-the-art loudspeakers for the consumer high-fidelity industry.

For the woofer systems in the new Series 2 versions of the L1590 and L980, ADS changed the 2-inch diameter voice coil former from aluminum to Kapton, a material unaffected by heat well beyond temperatures found in loudspeakers. Kapton is more stable than aluminum at high temperatures and is not affected by magnetic flux during wide excursions.* This simple change reduced low-frequency reproduction coloration and distortion, improved damping and increased power-handling capability for this woofer system. This was a subtle but important improvement in an already potent low-frequency system in the L1590.

For the 2-inch fabric-dome midrange driver, Kapton formers were also used in addition to Ferrofluid to stabilize and cool the voice coil. This improved transient response and smoothed the output in the 5kHz region approaching crossover, reducing a 2-3 dB rise at that frequency to 0 dB. The Kapton former further reduced mass, thus improving efficiency and damping of an already nearly ideal reproducer. The actual passband of the 2-inch Kapton midrange driver was widened to allow a lower crossover to the woofer section, allowing a 350 Hz crossover and the elimination of the 2.5 amp protection fuse. Crossover transition was smoother.

The ¾-inch fabric-dome tweeter also benefitted from the new Series 2 improvements. The 1.5 amp fuse was eliminated and a special, solid-state thermal protection device was incorporated into the crossover. A damping pad was placed under the dome that both protected the dome against indentation (fingers) and also improved damping. Ferrofluid added to the voice coil also increased damping and power-handling capability, and because of the lowered mass of the improved tweeter, the high-frequency on-axis response was extended well beyond audible limits. The tweeter's transient response was further improved, yet there was scarcely any evidence of ringing in any of the older tweeters. The clarity and smoothness of this tweeter was an important reason for the L1590's reputation as a superior sound reproducer.

Crossovers were improved in the Series 2 versions. Computer-aided analysis allowed ADS to improve interaction between the drivers and crossover, resulting in smoother response and lower coloration. Phase response was optimized for flat-baffle systems. Larger-diameter gold-plated binding posts were added to allow larger diameter speaker cable (up to 7 gauge). New-generation "slick-film" capacitors with lower dielectric absorption and less heat loss were added along with polyester-film capacitors in the tweeter circuits. Midrange coils were air-core, low-loss types and woofer chokes were ferrite-bobbin designs rated for 0.02% harmonic distortion at up to 500 watts input, just prior to saturation. This is steady-state power rating, whereas peak power inputs go greatly higher than that without saturation. For example, in 1984 Julian Hirsch tested the original version L1290 with peak power pulses of up to 2,500 watts at 10kHz, which was the limit of the testing amplifier, without distress, and up to 1200 watts at 100 Hz into the woofers. These high numbers are significant, but the L1590 has significantly greater power-handling capability than the 1290, particularly in the bass frequencies. With the Series 2 versions, this power-handling would have been even greater.

Therefore, the Series 2 changes were significant. Audible differences were certainly subtle, but when compared side-by-side, improvements could be heard in smoothness and clarity. These were the last of the butyl-rubber treated fabric-dome midrange and tweeter units, and the last of the "old" ADS speakers before the advent of the newer a/d/s/ versions of the CM and M speakers. Whether or not the new versions were better than the earlier Series 2 speakers has been debated at some length, but in terms of measured response smoothness and dispersion and the resultant acoustic power, the Series 2 speakers were probably superior to the later models and certainly among the best loudspeaker ever designed.

*Kapton is a high-temperature, stable polyimide dielectric film material used for critical aircraft wiring insulation, solderless terminals and other special applications requiring a wide range of heat cycles. It has been the material used for insulation in NASA lunar modules and so forth.

--Tom Tyson

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I remember reading brochures on the Series II. On paper, it seemed to have enough engineering improvements to justify it as a replacement for my 910's. So, I went to listen to them...forgot where. What I saw was impressive: tall, elegant towers with all drivers vertically aligned. Metal grills designed for minumum difraction. Compared to my relatively "squat" 910's, they certainly LOOKED more apealing to me.

But, when I heard them, I wasn't "hit-over-the-head" impressed. If I AB-ed them at length, and at home, I might have thought differently. When I asked about the price, THAT'S when I decided the audible improvements (I did hear some in that showrooom setting) were not large enough to warrant lugging them home for extended listening. I think I would have been impressed if I did.

Having done my share of crossovers at BA, I can attest to how important ADS's improved crossovers can be in determining overall sound quality. At the same time, many improvements can only be heard if the system is properly set up, AND quality recordings are used to reveal these improvements. I believe under normal conditions, many of these improvements would be inaudible or very subtle.

I know that there IS a "night and day difference" between an AR 3a and a AR10 pi. Despite having similar/identical drivers, I could easily and repeatedly distiguish one from the other blindfolded. Probaly not as much between the AR 10pi and the AR 9 as far as tonal balance...probably reasonably similar! However, the AR 9 would have been my speaker of choice (tremendous dynamic capabilities AND "imaging") if I had to own something "vintage". I can't help but wonder if I would feel the same way about the ADS Series II if I had purchased them.

The ADS Series II towers (an idustrial designer's speaker) LOOKED more advanced than the AR 9 (an audiophile/enginner type product). I wonder.... which product sold better?

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I was always amazed that AR was able to "get away with" such an unattractive cosmetic design as the original AR-9. I often wonder if the design was intentionally bad-looking, as if to emphasize the no-nonsense engineering, or if it was ugly simply because they had no good industrial designers working on the project.

I won't go into the detail-by-detail aspects of the awful looks of the AR-9. Suffice to say, the ADS towers showed that it was possible to put worthy effort into the appearance of the product, as well as the sound of the product.

The AR-9 would not be allowed to exist in its original form were it on the market today. I think that its acoustic performance is still commensurate with a TOTL speaker in 2012, but the requisite cabinetry would likely push the 9's list price into the $10k/pr. range in 2012.

But it would be worth it, I'd say.

Steve F.

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I was always amazed that AR was able to "get away with" such an unattractive cosmetic design as the original AR-9. I often wonder if the design was intentionally bad-looking, as if to emphasize the no-nonsense engineering, or if it was ugly simply because they had no good industrial designers working on the project.

I won't go into the detail-by-detail aspects of the awful looks of the AR-9. Suffice to say, the ADS towers showed that it was possible to put worthy effort into the appearance of the product, as well as the sound of the product.

The AR-9 would not be allowed to exist in its original form were it on the market today. I think that its acoustic performance is still commensurate with a TOTL speaker in 2012, but the requisite cabinetry would likely push the 9's list price into the $10k/pr. range in 2012.

But it would be worth it, I'd say.

Steve F.

I agree with Steve on this matter! The AR9, while a fine performer in every respect, is not a particularly handsome tower speaker. It lacks that classic beauty of the ADS L1590, yet each can hold its own, sonically, with about any new-design speaker out there today. I have both the 1590 and the AR9 and have lived with both speakers over the years. These two have many similarities with regard to powerful and clean acoustic performance, but the ADS 1590 is far more handsome in appearance.

--Tom Tyson

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Tom, I also have an ADS L1590 newly purchased and a set of AR9's. In my opinion so far they seem to be similar in sound and performance with a tad more bass going to the AR9's and a tad more tightness in bass going to the L1590's. However, the L1590's are INFINITELY easier to drive. It's made me consider (and I never ever thought I would say this) selling the AR9's. Have you had similar thoughts? I haven't A/B'd them and put them through the paces due to time constrains but perhaps you have.

Also, does anyone here have a crossover schematic for an L1590/2 and know whether or not there is any gain to recapping these? I have been told that ADS used a lot of poly caps in their xover but I'm not sure how pervasive that was and whether or not an upgrade to some modern film caps for the tweets/mids might give me some palpable gain.

Thanks,

McCarty350

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Tom, I also have an ADS L1590 newly purchased and a set of AR9's. In my opinion so far they seem to be similar in sound and performance with a tad more bass going to the AR9's and a tad more tightness in bass going to the L1590's. However, the L1590's are INFINITELY easier to drive. It's made me consider (and I never ever thought I would say this) selling the AR9's. Have you had similar thoughts? I haven't A/B'd them and put them through the paces due to time constrains but perhaps you have.

Also, does anyone here have a crossover schematic for an L1590/2 and know whether or not there is any gain to recapping these? I have been told that ADS used a lot of poly caps in their xover but I'm not sure how pervasive that was and whether or not an upgrade to some modern film caps for the tweets/mids might give me some palpable gain.

Thanks,

McCarty350

Hi McCarty350,

Both the AR9 and the ADS L1590 have a very similar and potent low-frequency response; both speakers have the same approximate system-resonance frequency. I think the AR9 has a bit more palpable bass output than the 1590 for a couple of reasons: 1) the 9's two 12-inch woofers are close to the floor, and thus the coupling is better and 2) the balance between the midrange/treble and bass is slightly different in the AR9, and tends to favor the low-frequency response more than in the ADS 1590. In short, the AR9 seems to sound "heavier" than the ADS 1590. I suspect that both speakers are close in overall performance in the deep bass (extension and harmonic distortion), but the two 12-inch woofers in the AR9 can technically move (slightly) more air than the two 10-inch versions in the 1590, plus the floor-wall coupling favors the AR9 woofers. It's been awhile since I've actually compared the two side-by-side, but both are such outstanding speakers that it would be hard to choose between the two. I do recall that the differences in powerful deep bass was actually tiny after both speakers were properly equalized for sensitivity differences. Whereas the AR9 might a slight advantage in the bass, the 1590 at times seemed a bit cleaner and smoother throughout the midrange and treble. One advantage: the ADS 2-inch midrange is extremely smooth from below 400 Hz up through 10 kHz, even though it is crossed over into the 3/4-inch tweeter at 5 KHz, it provides very smooth and linear response throughout the midrange. Therefore, there is one less crossover transition in the ADS than in the AR9and except for power-handling capabilitythis is probably an advantage. The ADS 3/4-inch tweeter has always been considered one of the best tweeters ever made, thus the treble response is excellent. I do know that a great deal of attention was paid to the crossover in the Series II versions, and a lot of tests were done with impulse testing to improve phase response along with improving the already nearly perfect transient-response characteristics of both dome drivers. I do know that both speakers are capable of handling a huge amount of clean amplifier power. Back when new, I was able to put my McIntosh MC2500 into Power-Guard protection mode using both the AR9 and the ADS L1590/2s on several separate occasions, and neither loudspeaker seemed to be over-stressed. Both were very clean and effortless, a hallmark of a premium tower loudspeaker system!

All in all, I'd have a lot of trouble choosing one over the other, I like them both so much! I'm in the slow process of rebuilding my pair of AR9s now, and I haven't been able to spend too much time recently on them, but I'll compare the two in more detail once I finish that restoration. I don't think the crossover capacitors are an issue with this series ADS speaker. The Series II speakers use high quality "slick-film" capacitors, and these are designed to last for many years without changes or degradation, from what I understand. I have not heard of the need to update any of the Series II crossovers, but I don't know that for a fact. The overall construction of the crossover is really top-notch, computer-grade, and unless you have a specific reason to change the crossoveror suspect something is amissI would leave that particular crossover intact. The crossover is a 12 dB/octave LCR type, but I can't locate a schematic. I'll try to locate one.

Tom Tyson

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Tom thank you so much for the great and lengthy response! I hadn't checked for a few weeks so I apologize for the late response on my part. It's getting late but I did open up and look at the crossover as much as I could (it's sandwiched together and it looks like it would be very tough to get it into two pieces without desoldering the binding post leads from the PCB) and noticed what I thought to be quite a few NPE caps. When I get a few more cycles I'll reply at length.

John

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Both the ADS 910 and the ADS 1590 (as well as other ADS speakers) used a version of the 2-inch treated-cloth-dome tweeter, but the differences in these drivers is shown in the attached photograph cross-section. This comparison shows the evolution from the earlier 910, 1230 and so forth up through the 90-series tower speakers. The later series of dome tweeters (L-1590, etc.) used a sealed cavity beneath the dome rather than an open bottom plate section. All versions of the linen soft-dome tweeter were treated with a proprietary butyl-rubber substance, spun on, for damping properties and stability. All domes used a very light voice-coil former and lightweight dome, placed within a very tight-tolerance voice-coil gap with a large magnetic structure for maximum damping. Transient response (and the accompanying flat frequency response) was excellent for this driver with no modes of ringing or spurious output.

Tom Tyson

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Some additional technical details on the ADS 1590 Series-2 woofer, part number 206-0631. The images have inscriptions describing mechanical details.

  • 10-inch acoustic-suspension woofer design
  • Extremely flat, linear response in the 28-350 Hz range
  • Very low distortion from 20-350 Hz
  • Low-resonance [free-air resonance approx. 19-20 Hz]
  • Low system resonance 35 Hz; -3dB 28 Hz
  • True system extension to 20 Hz and below with low distortion
  • ADS Stifflite molded-fiber/paper cone assembly
  • Crossover at 350 Hz
  • 2-inch copper voice coil wound on Nomex high-temperature former (bobbin)
  • Large-diameter, flexible treated-fabric spider assembly for long excursions and voice-coil centering
  • Butyl-rubber half-round surround (skiver) for precise control and long-life durability
  • Large voice-coil overhang, keeping voice coil in linear magnetic field during >1/2-inch excursion

--Tom Tyson

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ADS L1590/2 Ferrofluid Question:

The question of the Ferrofluid magnetic fluid evaporating in the magnetic gap in mid-range and tweeter domes of the ADS L 1590/2 and L1290/2 is addressed in these comments below from another thread on this site, "L1590's! Now what?," and I thought it would be useful to bring it over to this topic on the 1590 that I started quite some time back, since there is much more technical information present here.

I am not aware of a true problem with the voice coils in the ADS 1590 or 1290 or the other ADS models using versions of the 2-inch and 3/4-inch dome drivers; it is possible that some speakers that had been driven abnormally hard at high-acoustic levels might suffer evaporation of the oil in the gap, but under normal use this is somewhat unlikely. Comments below address this question, but the important thing is that evaporated Ferrofluid will cause distortion, lower output and uneven response, and these effects would be quite audible.

—Tom Tyson

Posted 14 November 2015 - 07:17 PM:

Well, picked them (L1590s) up yesterday and have them hooked up now. Very, Very Nice as others have said here (TT) Impressive. I am running them with my Adcom GFA5500 and a tube preamp. My room is on the smaller side so I think that will be plenty.

All drivers seem to be in good order but would like everyone's impression on weather or not I should send the tweeter/mids down to Arizona to be looked at and serviced. You can see a slight impression in one of the woofer dust caps too.

--DavidDru

Posted 17 November 2015 - 12:33 AM:

I contacted ADS repair guru Richard So down in AZ. He think these would benefit from service to the Mids and Tweeters. Old Fero Fluid gets muddy I guess. Something you probably wouldn't realize until they are serviced and get them back and hear a difference. He has a special for all 4 for $225 that I will probably take advantage of.

Posted 17 November 2015 - 05:05 AM:

DavidDru,

That Ferrofluid issue has become a topic of a lot of discussion. If the fluid dries up, the midrange and tweeter would likely sound distorted and "muddy," and the high-frequency mid-range and treble response would fall off precipitously. But on the other hand, if you think the sound is clean without distortion, there's a good chance the Ferrofluid hasn't dried up. I have both L1290s and L1590s, and I don't detect any distortion or change in the character of the sound, but I would have to say that neither pair of ADS speakers was electrically abused (over-driven) over time, so I don't suspect any real issue with the tweeters (or the crossovers, for that matter). In short, I don't detect too much difference from when they were new, but hearing memory is short, so it's not possible to know precisely. If you are a risk-taker, you can remove a mid-range driver and a tweeter, and you can actually remove the aluminum top plate and inspect the gap and the voice coil to see if the material has dried. The dome and coil assembly can be re-installed, but it is still a slightly risky proposition.

The only real test would be to measure the tweeters' response anechoically, and that would not be easy to do without taking the drivers out of the cabinet and measuring them -- with crossover in place -- individually for on-axis frequency response to see if they match the original measurements (only a few response graphs are present in some of ADSs original lliterature). On the other hand, sending them off to be "checked" for that would mean that a new dome/coil assembly would have to be installed, and the old magnet assembly/gap would have to be completely cleaned out and replaced with fresh Ferrofluid, and that is a very, very difficult thing to do since the Ferrrofluid is a magnetic substance in an oil base, and those magnets are very powerful. In other words, unless it was done by the factory -- which no longer exists -- it's very likely that the end result could be worse than when you sent them in for repair. As they say, "if they ain't broke, don't fix them!"

—Tom Tyson

Posted 17 November 2015 - 12:33 AM:

Ferrofluid does also reduce Q of resonance. Measuring Q or at least max impedance will take only few minutes and may give clue how things are?

This is not fool proof method as coil scraping to dried fluid will also reduce Q,

Best Regards

Kimmo

Posted 17 November 2015 - 11:04 PM:

Kimmo,

Yes, measuring the impedance at resonance might be good, but it would need to be compared with the original factory curve for reference to determine any changes. Does anyone have that? I suspect not, insofar as specific measurements were proprietary during the ADS production years, to my knowledge. There were generic measurements that were published, but not specific measurement curves. It's the same with the frequency-response measurement of an original vs. an old one; unlike AR, for example, there were few, if any, published response and distortion curves, per se, of the ADS drivers other than in promotional literature.

____________

***Probably the only thing to do now would be to listen carefully to determine if there is an audible problem. If one of the speakers had been previously played at very high output levels -- especially over extended periods -- the temperature of the voice coil would be very high, and this would accelerate changes to the Ferrofluid in the gap (even cause the magnetic fluid to boil), but under normal conditions, no one seems to know how long the Ferrofluid will remain in the gap without going bad. I've heard 15 years, but that's also the "half-life" of urethane-polymer foam surrounds, so that age period for Ferrofluid is probably internet "conjecture."

I honestly don't know the answer to "how long." It is clear, of course, that if new oil is put in the gap, the old stuff has to be removed, and that job is very, very difficult due to do because of the strong magnetic strength of the ADS magnets and the narrow voice-coil gap. Metal particles from the Ferrofluid would be left behind, too. I suspect that those metal particles and any oil residue left would be highly resistant to removal, so I just don't know how it could be effectively accomplished. Also, it's nearly impossible to get beneath the gap; i.e., on the underside, because of the back plate/pole piece assembly that are staked together. Therefore, all removal would have to be done from the top, and I've seen attempts at doing this, but none was definitive and the outcome was questionable.

And, once all of this was done, the driver would have to be measured for smoothness, uniformity and impedance, as well as for sensitivity, and the measurements would have to be compared with the original impedance curves and response curves, for which none were published (for the public) by ADS.

—Tom Tyson 11/21/2015

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Attached is the owner's manual for my pair of ADS L1590/2 loudspeakers, and it may have some helpful information for those with the series 1 as well, but there are some differences, some noted on the final page.

ADS_L1590-2_Owners-Manual_Tyson980.pdf

--Tom Tyson

***Update: the manual supplied by ADS was actually for the Series 1; but rather than print a brand-new owner's manual for the Series 2, ADS added a supplement at the very end (shown with my manual) describing the differences. Therefore, this manual works for either the Series 1 or Series 2.

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Tom, getting back to this as a follow-up.  Thank you for all the very helpful information you have provided in this thread.  Great stuff.  Now that I am the very lucky owner of both the AR9 and L1590 speakers much of what you have provided is very applicable.  As I read your comments and thoughts on each I have been nodding my head in agreement. Listening impression that both you and McCarty provided are similar to mine.  

Over the years my plan is to preserve each and enjoy them as much as possible.  Both sound fantastic as I hear them now, but I of course have no idea how that compares to what they may have sounded like new.  This is of course a challenge for many of us that have jumped into this fun hobby and it keeps of curious.  Where do we stop and start with our efforts to restore these beauties to their fullest or former glory?!  Do they need it? Some things man engineers are just run until they give out. Other things are better serviced along the way.  What do we do here?

I did send the 1590 mid and tweeters down to Richard So for the treatment and I will report all is great.  As I had stated in my other thread and you copied above I felt they sounded pretty darn good as they were.  Getting them back, they sound pretty darn good and I also know they are set in this regard for another good block of time.

I also now have the 910's and will be sending those drivers to Ricard as well at some point.  710's will arrive on my doorstep on Sunday!

I have not as of yet concerned myself with any of the crossover components.  Their complexity is enough to make me pause at this point considering they sound so good.  My guess is that replacement of the many caps would be quite expensive.  When I do get the courage I hope to tap into the vast knowledge and experience on this board and maybe find some ways to go about things practically.  Maybe even remove and measure them before assuming they need to be replaced. etc.

Both still need the treatment on the exteriors and I have again paused as I want to take my time, reflect on things and do it right.  Maybe even find a way to sexy up the otherwise brutish AR9's! (As it seems none of us feel they are lookers as they are)

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Being a 910 owner, early sequential numbers, with original stands, this thread is invaluable! Incredible information here.

Regarding the 910's sound, I have found them to out preform just about every speaker set I own. This includes AR12's, AR3's, AR LST-2's KLH Fives, among a few others, (all restored). The only set that comes close are a set of Prototype/DIYs, labeled "Angelica's", I found at a GW a year ago that are incredible. I have a lengthy thread over on AK about them. Anyway, I sent my mids and tweeters to Richard So for preventive maintenance more than for sonic improvement. They sounded great prior to the rebuild, but a bit better after. Just a bit cleaner and crisper in the mids and highs than before, though not at all harsh or too forward sounding. In my space in my cave/basement, they sit about 10 feet apart. The sound stage spaceiousness and dimensional clarity are quite amazing. I too had wondered why these were not mirrored, and assumed it was a cost issue vs. sonic benefits. The cross overs are original and will be left alone. I was able to find and purchase the bi-amp & tri-amp cards as well as the LED cards, and may some day try to bi-amp them, but for now I'm quite happy. I'm driving them with a JVC M-7050 power amp rated @ 150wpc, but on my techs bench was putting out 210 wpc. This combination is just spectacular, and as stated earlier, at extreme volume, the 910's output is effortless and distortion free.

I would love to hear the later models just to see how they compare some day.

Glenn

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I don't find that the ADS speakers need anywhere near as much restoration/preservation as many other speaker brands.   There is no one yet that has proclaimed the driver rebuild is much more than a small improvement and a comfort factor for the owner that they will be good for years to come and the woofers don't need to have surrounds replaced.  Many of the caps are film caps and won't need replacement.  Only thing is the metal grilles on those so equipped that would usually need some body work and a light coat of satin black paint (not on the bronze grilles) and the speakers would be ready to go.  Those ARs need lots of foam for the drivers and the cabinets, if I'm not mistaken.  Good thing they are worth the work.  

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899, I think you are correct with some exceptions. It seems there are a few specific drivers that ADS had some production issues with and need to be changed out if they are still around.  Glue issues mostly  Cant recall which specific models those were found in but it was a few maybe.

The ferrofluid in the drivers can also be about at the end of their life cycle but at least that can be addressed.

Also, that darn crossover board arrangement on the 910's can cause some age related issues in regards to parts or pieces needed to be tightened back up, reflowed and cleaned since it is exposed and is exposed to a little more wear and tear.  

The rubber surrounds help.

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On 8/25/2016 at 8:05 AM, DavidDru said:

Tom, getting back to this as a follow-up.  Thank you for all the very helpful information you have provided in this thread.  Great stuff.  Now that I am the very lucky owner of both the AR9 and L1590 speakers much of what you have provided is very applicable.  As I read your comments and thoughts on each I have been nodding my head in agreement. Listening impression that both you and McCarty provided are similar to mine.  

Over the years my plan is to preserve each and enjoy them as much as possible.  Both sound fantastic as I hear them now, but I of course have no idea how that compares to what they may have sounded like new.  This is of course a challenge for many of us that have jumped into this fun hobby and it keeps of curious.  Where do we stop and start with our efforts to restore these beauties to their fullest or former glory?!  Do they need it? Some things man engineers are just run until they give out. Other things are better serviced along the way.  What do we do here?

I did send the 1590 mid and tweeters down to Richard So for the treatment and I will report all is great.  As I had stated in my other thread and you copied above I felt they sounded pretty darn good as they were.  Getting them back, they sound pretty darn good and I also know they are set in this regard for another good block of time.

I also now have the 910's and will be sending those drivers to Ricard as well at some point.  710's will arrive on my doorstep on Sunday!

I have not as of yet concerned myself with any of the crossover components.  Their complexity is enough to make me pause at this point considering they sound so good.  My guess is that replacement of the many caps would be quite expensive.  When I do get the courage I hope to tap into the vast knowledge and experience on this board and maybe find some ways to go about things practically.  Maybe even remove and measure them before assuming they need to be replaced. etc.

Both still need the treatment on the exteriors and I have again paused as I want to take my time, reflect on things and do it right.  Maybe even find a way to sexy up the otherwise brutish AR9's! (As it seems none of us feel they are lookers as they are)

DavidDru,

I'm glad to learn that you have restored your L1590s and got your midrange and tweeters refurbished from Richard So.  I think he is the one from whom I bought several ADS replacement parts, such as woofer cone/voice coil replacements, new midrange and tweeter dome top plates, etc.  I've never had to use any of them, but it is good to have those replacements, and it is nice that ADS went to the trouble to make their drivers so easily restorable.

Let me know how you think the 910s sound when compared with the 1590s.  The 910s were very fine speakers, but they were not quite as robust and refined as the 1590s.  I honestly can't imagine the need to replace the crossover components on any of the up-scale ADS speakers in the L series.  ADS L1590 and L1290 (and L1090, among others in this family) crossover capacitors are computer-grade throughout, and all of the crossover components are premium quality, and I think they will last a long time.  The impression I have is that few people have to update the crossovers in ADS speakers of this generation.  I have never attempted to replace anything on either my 1590s or 1290s, but both sound pretty much exactly as they always have sounded!   Neither my 1590s nor the 1290s has ever been driven hard (other than brief bursts of high power) over the years, and neither has been in constant use over the years.  I really don't see any signs of deterioration over time, but I'm sure all speakers gradually deteriorate very slightly as the years pass.

As for the cabinets, the finish is lacquered, and to repair or refinish will require more detailed steps than the simple oil finishes.  However, use of the new poly finishes, such as premium-quality Mohawk Pour-n-Wipe, and similar wipe-on polyurethane finishes, can probably be used on these lacquer finishes once the original finish has been sanded sufficiently.  The end result would probably be very similar to the matte-type luster of the original ADS finish (done in Germany, incidentally).

—Tom Tyson

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