tysontom

The term "tweeter" is technically correct, but the reference to the 2-inch driver in the 910 and the 1590 was actually to the mid-range driver. --Tom Tyson

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

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

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

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

I don't have those parameters, but you could get some internet-based measuring tools and measure the drivers that you do have if you want to try to match them. You could also simply reverse-engineer your existing ADS L1290s' crossover networks when constructing a new one, and then use basically the same drivers. If you are going to use non-ADS drivers, then you will probably need to start from scratch. It's probably not so much the impedance, sensitivity and so forth that are at stake, but the dispersion characteristics that would be different if you used something other than ADS drivers, but the latter are readily available on the internet. Changing the layout from vertical to horizontal will also affect the speaker's spectral balance, too. You are not likely to need the bass power of the standard configuration for your proposed center channel, so you could use smaller woofers or even a single woofer for the center. Good luck on your project.

There were some significant differences in the Series I and Series II ADS models, primarily the addition of Ferrofluid, changes in crossover component (improved quality components, etc.), slightly extended high-frequency extension, elimination of the slight 2-3 dB rise in the midrange response, greater overall power-handling capability and so on. The crossover frequencies remained unchanged, I believe, which in the case of the ADS L1290 Series I and Series II is 500 and 5000 Hz., 12 dB/octave slopes. The Series II high-frequency output, on-axis, was extended out to 27 kHz from 23 kHz, but of course this is just marketing talk mainly because of the extreme range involved. Who can hear out to 27 kHz? But the response was smoother out to the limits of audibility, and this could be heard. The Series II also used Kapton voice-coil formers for the midrange and tweeter (and the L1590-2 woofers) voice coils, and this enabled much greater power-handling capability. Fuses were eliminated in the Series II altogether in the midrange, and a solid-state protection system was embedded in the crossover to protect the tweeter against excessively large input levels or overload. You could probably mix and match for a center channel without causing too much difficulty, especially since it will be reproducing a lot of voice information and less deep bass and music, etc. --Tom Tyson

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

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

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

Gerry, I never owned the ADS 910s, but I was very impressed with their sound on several occasions. At the local ADS dealer close by, I was able to compare the 910s—with levels equalized—with my own AR-3as, and the ADS was marginally more powerful in the deep bass, as expected with its lower system resonance. The 910 also had more "clarity," but it was also more forward-sounding to me; and what it had in "clarity" over the AR-3a, it seemed to give up in spaciousness. So that might have been a wash. Both speakers are such great reproducers, it's difficult to make a true value judgment on them; however, for sure, the ADS 910s could pound out higher SPL levels more effortlessly—perhaps without strain—than the AR-3a, but then the 910 was intended as a monitor speaker. The 910 never seemed muddy at any sound level I could withstand. 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. The ADS 910 had a 550 and 4000 Hz network (12 dB/octave, as with the tower speakers), whereas the 1590 had 350- and 5000-Hz crossover frequencies. In this way, the 1590 used the excellent 2-inch dome to handle a great deal of the important middle frequencies, and thus the dispersion at upper bass frequencies was improved. The 1590 also had a lower fc (33 Hz vs. 39 Hz) and much more robust 10-inch woofers than the 910. I also believe the 1590 was a significant improvement over most of the earlier ADS tower speakers, such as the 1230 and the 1530. For one thing, the treble was toned-down with the improved dome drivers in the newer series. The humongous ADS 2030 may have been the best—I don't know—but it was just gargantuan with its multiple mids and tweeters and dual 14-inch woofers, and it was a favorite of the Telarc recording group for a long period of time. --Tom Tyson

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. Fig. 1: Inverted view of high-output 10-inch ADS Stifflite Woofer used in the L1590-2 Fig. 2: Detail of the conformal high-temperature coating of the 2-inch diameter, long-throw ADS L1590-2 dual 10-inch Woofers Fig. 3: 2-inch Diameter Voice Coil used on the ADS L1590-2 dual 10-inch Woofers Fig. 4: Detail of the cross-section of the special felted cone assembly of the 10-inch ADS L1590-2 Woofers --Tom Tyson

audiomagnate, Judging by a previous message, you may no longer be on this site, so we're sorry to see you leave if this is the case. With regard to the L1530's efficiency (sensitivity), it was rated by ADS at 95 dB (in a 2000 cu. ft. room), about 5-dB more efficient than the later L1590, rated at 90 dB (in an "average-sized" room). ADS recommended a minimum of 10 watts and 300 watts maximum for the 1530, whereas the 1590 recommended 15 watts minimum and 500 watts maximum. However, the principal reason for this high efficiency rating was the 1530's use of the samarium-cobalt magnet in the 1-inch tweeter vs. the standard ceramic magnet used in the later speakers. For some reason, ADS had the spectral level set fairly high (read "bright") for the L1530 1-inch dome tweeter, but this was later changed in the 1590 ¾-inch tweeter. Also, the woofers in the 1530 had less voice-coil "overhang" in the woofers than with the later 1590 system; as a result, 1590 had lower bass distortion and greater power-handling ability than the earlier 1530 system. It is possible that the 95-dB rating for the 1530 was slightly optimistic, but the system was definitely more sensitive than the later 90-series speakers. The 1530 was also rated with a 25-20,000 Hz frequency response, ±3dB, meaning that the 1530's system resonance was very slightly lower than the 1590, rated at 28-27,000 Hz ±3 dB. In any event, both systems are impressive tower speakers of very high quality! --Tom Tyson

Which version L1590s? Are they the first version or the L1590-II? The fuse for the tweeter is a Bussman 3AG 1.6A for both versions, I believe, but the fuse for the midrange (which was a 3AG 2.5 Amp) was dropped in the Series II speaker as being unnecessary. What kind of music was being played when the fuses blew? The speakers are rated for 500-watt peaks, and in actuality easily handle upwards of 1000-watt peaks, but no speaker can readily handle sustained high-energy rock music or the like, with intense high-frequency energy being put into the tweeters. During the April 1984 Stereo Review Equipment Test Report on the L1290 (almost identical tweeter and midrange to the 1590), Julian Hirsch tested the tweeters with high-energy tone bursts of up to 2,500 watts into the tweeter at 10kHz without distortion, so the driver will handle a lot of power if it is short term and clean. Your Proton D1200 might be clipping on some of the high-energy peaks, as well. --Tom Tyson

Powering the ADS L1590s and L1290s: I have found that any number of power amplifiers can do a decent job driving these speakers, but the ADS speaker efficiency is relatively low and their power-handling capability is high, so I have been using QSC professional amplifiers of late to drive them. For the L1590 I use a QSC PLX-3602 Two-Tier Class-H amp (switching power supply), and the sound is effortless. This amplifier is capable of nearly 1000 watts/channel into the 1590s, so fusing is a must. For the L1290 I have been using a slightly different QSC design, a class AB GX3 design, about 300 watts/channel. The 3602 is a highly advanced, high-power design with very low noise and low distortion, but frankly it is very difficult to discern any differences between any quality amplifiers operating in their safe range driving into an impedance that does not cause problems. The reasons for using pro amps are simple: these amplifiers are far more rugged and conservatively designed than their consumer equivalents, and they are reasonably priced due to the competitive nature of the pro-sound market. These amplifiers can operate into very low impedances and capacitive-reactive loads without any stress, and the distortion levels are usually in the 0.05% range across the band. Also, the consumer-audio business is dying with the lack of interest in quality "stereo" high-fidelity sound (iPods and Bose Docking Stations rule now), but the professional-audio market is still very strong. In fact, the QSC RMX 2450 is the best-selling amplifier in the world, and it is among the most reliable devices of its sort available with a failure rate of less than 1/2 of 1%. Crown, Crest and other professional manufacturers offer similar devices. The end result is effortless sound quality from these speakers, and the knowledge that very little can cause problems for these amps. There is fan noise, but the newer pro amps have a low fan noise unless the amps are driven excessively hard. --Tom Tyson Image: rack-mounted Crown and QSC amplifiers

The files were apparently too large and didn't pass the server. I'll try again later in a modified format. --Tom Tyson

These ADS Tower Loudspeaker brochures may have been previously listed, and the files are large, but here they are again: (1) ADS L1090, (2) ADS L1290: --Tom Tyson

Bob, that was an excellent and lengthy addition to this post. It is great to have someone who was part of ADS to add to these comments. I do have a question for you: who actually did the design work at ADS on the L1590, L1290 and L1090 series (and other variants) that were introduced in the mid-1980s? These speakers, even to this day, are excellent designs and among the better products ever designed by ADS. Also, I believe that the company used the ADS trademark until the M-series was introduced, and then a change was made to a/d/s/. I incorrectly listed the L1590 as an a/d/s/ version; it should have been ADS L1590. --Tom Tyson

Some additional images of the ADS Rosewood L1590:

These are some interesting comments, but I don't follow you on the requirement for such high current for these a/d/s/ speakers or the McIntosh solid-state power amps not being able to deliver sufficient current current up to their rated power. Most of the Mac amps had multiple output taps, including 4-ohms and lower, such that full current commensurate with the rated power (per Ohm's Law) would be delivered to any load, continuously, both channels operating. I had a MC2500 amp for many years, and it had a 1-ohm, 2-ohm, 4-ohm tap, in addition to higher-Z taps, which would be very compatible with the M30's 4-ohm impedance and 91 dB sensitivity. With each lower-impedance tap, of course, the amp would swing twice the current across the load for a given voltage, and the amp was rated for full power into each impedance tap. In other words, there is no way that a MC2500 has insufficient current to drive an M30 or M20 speaker, especially since the M30 is rated at 91 dB sensitivity. I had my MC2500 amp tested at a McIntosh Clinic soon after I purchased it, and it delivered over 725 watts-per-channel RMS continuous output into 4 ohms right up to the point of throwing the 15-amp breaker on the test bench. The voltage sag was so great that the lights on the test bench grew dim. The maximum input power dissipation for the MC2500 was close to 22 amps, so the amplifier could easily overload a 15-amp standard wall circuit; after that test in the dealer showroom, I wired in a dedicated 20-amp circuit at home used only for the amplifier, and the voltage never sagged. So now the MC2500 could deliver its full-rated (plus some) power into any load, continuously with approximately twice that amount as an instantaneous peak, before the Power Guard circuit softened the output. Several Krells and Threshold amplifers, among other exotic amps, were designed to be able to produce very high brief power peaks, and this is where the high current comes into play, but these power levels are very brief before distortion sets in. The point is, the MC2500 could effortlessly drive an M20 or M30 to its full capabilities, and for that matter, any loudspeaker designed for home use. I would suspect that if an M20 was causing the Power Guard light to flicker with the music at "not very high volume," most likely the speaker was connected to the wrong output tap on the amplifier, thus limiting the actual power being delivered. --Tom Tyson

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. One thing that ADS did for service centers was to provide replacement dome assemblies and woofer-cone-voice-coil assemblies that could simply be placed into the magnet assembly with minimum alignment difficulties. The woofer replacement assembly did include a clear cylindrical alignment shim to make sure the coil was properly in place. The dome tweeters were placed down into the ferrofluid already in the gap, thus assuring good alignment once the four centering screws were in place. The precision manufacture of these drivers is amazing! The voice coils are coated with a special dark-gray lacquer coating, but this was later dropped in favor of clear lacquer. The woofer voice coil on the L1590 was 2-inches in diameter, quite large for a ten-inch woofer, and the cone material (referred to as Stiflite) was thick and dense, yet very light. The woofer's coil former, or bobbin, was made from Kapton, a high-temperature Nylon-like material that is ideally suited for that purpose. --Tom Tyson

In 2001 a/d/s/ became part of Directed Electronics, a large (and the industry leader) auto-alarm security systems manufacturer based in southern California. Directed Electronics acquired Orion and Precision Power that same year; and since that time the company has been on a steady diet of company acquisitions, including Polk and Definitive Technology, making the company the number supplier of home-theatre loudspeakers, according to their website. Directed Electronics has sales of $400M in 2007, but also had a big loss due to a non-recurring cost. In 2006 the company had sales of $438M and a profit of $21M, approximately. As for a/d/s/, the division produces mainly home-theatre products. What I don't know is the history of a/d/s/ during the 1990s. I don't know when the company was first sold, but for now a/d/s/ is in good hands. --Tom Tyson

Steve F, Some additional comments on your message above: ADS did offer a PA1 Biamplifier (module) powered option in 1986 or 1987 that mounted down at the base of the L1290 and L1590 speakers (only). The cost was $1200 (per pair), and I don't think ADS offered the option for very long due to its added cost. By late 1987, with the introduction of the new "Unison" M9, M12 and M15 (equivalent to the older L1590), the power module was not available, to my knowledge, or at least I've never seen one in use with the M12 or M15. It was also at this time that ADS adopted the a/d/s/ logo (which was not used with the original L1290 and L1590 series I and II), and the gradual slide backward had begun although there was a spurt of activity with the "Unisom" M-series and the CM5, CM6 and CM7, all superb and favorably reviewed loudspeakers. Perhaps it was the beginning of the Subsat series and the exotic M20 and hugely expensive M30 that began the slowly downward spiral (as with so many other loudspeaker manufacturers during the late 1980s and into the 1990s). As for ADS' critical acclaim, there were numerous reviews on the various models (up through and including the Unison series) in most of the major magazines. Nearly all of the reviews were extremely flattering and favorable to ADS, with many exclamations from renowned critics such as Julian Hirsch saying about the L1290, "...the widest and flattest response we can recall measuring from a speaker with our current test procedures." Another reference to the 1290, "the woofer distortion was perhaps the lowest we have yet measured." Hans Fantel in The New York Times said, "...the L1590 is widely regarded as one of the finest loudspeakers ever made." Ovation magazine reviewed the L1090 and gave it very high marks; High Fidelity gave high marks to the single-woofer L990 as did Digital Audio magazine. Hirsch also reviewed the L780 and gave it the same type of excellent review as he did the 1290. These are just some of the reviews that I have in my file; there are probably quite a few more. --Tom Tyson The excellent ADS 2-inch dome midrange of the mid 1980s.