Is it possible to get the same sound as the IRSV for less?

September 20, 2017
 by Paul McGowan

6 comments on “Is it possible to get the same sound as the IRSV for less?”

  1. I agree with the need for lots of drivers for effortlessness. But I suspect that today we can get similar effortlessness with fewer drivers so long as the drivers have a linear longer throw and there are some very good dynamic drivers that do. Part of the reason the IRS had so many drivers is the limited throw inherent in planar drivers. I do agree that the best way to use multiple drivers to cover the same band width(except possibly for the deep bass) is a line source.

  2. Mrs PG and I visited PS Audio at the end of May 2017, got a tour of the facilities-thank you Kevin, and ended up in Music Room #1 for a demonstration. Everything that Paul has said in his description is accurate. Mrs PG, who has never been in the least interested in audio or music reproduction, was mightily impressed. The only problem with listening to the IRS system is that it left me with a case of upgrade fever.

  3. The IRSV reduced many forms of distortion to a practical minimum at the time by throwing drivers at the problem: Power compression, Doppler, non-linear suspension, magnetic circuit and cone breakup, speaker clipping (Vd), amplitude and slew limits of amplifiers. Driver limits at the time where a problem. EMIMs have very little volume displacement, near zero linear volume. Woofers needed servo because the magnetic circuit and suspension were non-linear approximations; and they weren't fast enough so there was a crossover point tradeoff.

    The brute force also has advantages in room interaction. Vertical comb filtering is reduced to a practical minimum and the wide, curved baffle and rear tweeters provided a more seamless transition from 2PI midrange to 4PI bass. This was a groundbreaking implementation of the criterion of flat frequency response at all angles. Other speakers managed to achieve both flat response on axis and AVERAGED over all room reflection angles, but off-axis lobing always interferes with (fake two channel) imaging, as does the diffraction of sharp edged cabinets.

    Some other approaches have roughly equivalent performance at normal listening levels, but with different sets of virtues: The Dunlavy SC-VI, the Audio Artistry Beethovens and the TAD Reference One. Dunlavy mastered first order crossovers and built a 4 way WMTMW tower that could reproduce square waves in the sweet spot, with near perfect phase and transient response for one listener. He combined a stepped baffle with acoustic resistance that absorbed the surface wave, eliminating secondary edge reflection. The crossovers were hand tuned for the driver set, which was matched in stereo pairs. Unfortunately the horizontal response was more conventional so they needed an enormous room, or heavy diffusion/absorbtion on the side walls, and preferably on floor and ceiling reflection points as well. The frequency band was divided in four, which is better than three, but the shallow slope of the crossovers produced more distortion than the big Infinity's, particularly Doppler (1/3 as many woofers). Further, a 1" dome tweeter is far short of realistic sound levels, a fact that is masked by the treble and transient rolloff in most recordings.

    The latter fault is shared by the Beethovens, but they have much better room integration from the midrange, woofer and subwoofer dipoles. This produces a null from side to side, including the ceiling and floor in a circle that reduces the need for acoustic treatments. Properly executed dipoles also flatten the off-axis response for superior imaging:

    Dipole woofers cut room modes in half, and drop the woofer resonances to free air Fs producing lower group delay than any other enclosure type. These had the best bass sound of any commercially produced speaker.

    Beethovens are near to the IRSV in surface area below 3KHz, with 2x8" midrange, 2x10" woofers and 4x12" subwoofers per channel. The Doppler distortion and power compression are reduced by a high order Linkwitz crossover. It was a poor seller despite being a tremendous value at $25K per pair, with a total of ten high end Danish drivers plus the eight Peerless woofers. Where it falls short is phase/transient response, as shown in this measurement:

    The TAD has spatial coherence from concentric Beryllium drivers. The critical damping of Beryllium enables a 3.5cm dome, with 6dB more headroom than standard 1" while still being only 10dB down at 100KHz! The cabinet is well rounded and very dense. The fault here is small midrange (6" equivalent) and woofer surface area, with a mere 2x10" bass configuration. Subs recommended.

    I have heard one system which equaled or exceeded the IRSV - a Wisdom Audio installation with essentially the same technology, floor to ceiling planar magnetic mid/treble and dynamic woofers. The in-wall configuration eliminated the issue of rear wall reflection and produced a more stable radiation pattern, also the custom installation eliminates the ceiling gap. This was so clean and lifelike that I could hold a conversation while listening at full orchestral levels just like at symphony - except nobody was shushing us.

    In summary: there is no substitute for surface area to produce the effortless sound, and that costs money. Floor to ceiling geometry, on-wall, in-wall or dipole is necessary for room integration. You can substitute cheaper drivers because all drivers are clean at lower displacement, and more division of frequency bands helps but has trade-offs.

    Neodymium-enabled pleated planar mids and tweeters are the good news because they squeeze air, and squeeze five times the radiating area into the same aperture for higher efficiency, higher output and flatter off-axis response. The bad news is they are too expensive for floor to ceiling, and have vertical off-axis problems.

    My hands are up to the elbows in the mud of commercial compromises at the moment. My custom speaker consorts built with no constraints on cost nor convenience serve well for my live recording studio, but nobody wants to buy them. I am working on concepts to create the same visceral impact and nuanced precision in affordable and portable packages. Subwoofers will be required...

      1. hi paul,

        i have been fortunate to have been here in SoCal during the heyday of the Infinity ServoStaiks I and beyond, the QLS and QRS sometimes amplified by Electro Research A75s (John Iverson of Eagle Kinetics) at places like Woodland Stereo and Music and Sound, both Infinity Dealers just across the street from one another.

        i ended up with what i could almost afford-the Monitor Jrs, a 12" 3way with dome mids and tweeters. flat to 30Hz in the lows, and out to about 25kHz on the top.

        much later, the IRS was developed and i heard various iterations, the last time at a Stereophile show on Century Blvd near LAX. it was about the time when Arnie was getting ready to bail from Infinity and form Genesis Technologies (remember that?)

        a friend had been friends with Arnie and had purchased Servos One, sn 001 from Arnie, from his garage. that is Vince Fennell, MD who i worked with at Northridge Hospital. we were talking and Arnie's name came up and i asked if he had spoken to him, to which he replied "no", he hadn't seen him in a while. so i asked him if he knew where he was, and he said no. well, i did and told him that Arnie was in Colorado. Vince flew there and had dinner with him.

        back to speakers. i had spent many an hour in front of speakers that were flat to 16Hz (IMF Monitor IIIs improved) which driven by the Ampzilla in my other friend's system and they didn't sound like there was much bass until it was actually in the program material. he eventually got a pair of Martin Logan reQuests and used the IMFs as subs. again, effortless. the bass being flat all the way down to the cellar truly enhances imaging/soundstaging and therefore-REALISM.

        another friend has speakers with a large AMT that crosses over at 500Hz! it sings with two 12" eminence drivers and the xover is undetectable. the speaker has dynamic range that easily accommodates live trumpet reproduction (driven with an Odyssey amp).

        when ESS had the AMT I, i couldn't stand it. the woofer was inadequate in tightness and definition and the amt had a peak near the 10k range that was unlivable. Thankfully, the modern AMTs are much improved.

        so, if the 500Hz ribbon was hooked to better woofers than the eminence (actually not bad but not optimum), that might be a KILLER system.

        are you asleep yet?

        thanks for listening,


  4. Ultimate effortless is great but unaffordable to most people. What you need are full range speakers with reasonable effortless sound that are detailed, coherent and have good tonal balance. Add subwoofers to get that last bit of low end, good amplification and you will be in audio heaven in most rooms. Some of the best most effortless speakers that cost a zillion dollars are probably too much speaker for most practical rooms and you won't get the best out of them in those rooms anyways so you are better off with affordable effortless speakers. People who could afford the ultimate effortless speakers usually don't have room size problems.

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