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Sound Lab Ultimate U-4iA electrostatic speaker Review

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Systems and listening impressions

The initial system I set up was as follows:

As the first few songs wafted across my ears my thought was, “I can’t for the life of me understand why anyone would opt for a vintage Quad.” Before me was a speaker with warmth, openness and generosity in the midrange and that special zip that an electrostatic provides, but done up in a grand fashion. At this time I was listening often to Everything But The Girl’s The Language of Life 2013 Edsel Remaster that includes a great number of variant recordings, such as remixes, alternative rough mixes, home demos and live performances. It contains a very wide range of recordings for comparison on a system. This is a wonderful collection of stripped down instrumentals with raw vocals, cleaned up studio enhanced renderings, and bombastic LF remixes. The continuity of having one group of songs with its radically different iterations allows me to understand more precisely the performance of the U-4iA.

My first impression was that the vocals of Tracey Thorn were brought forward and more in line with the rest of the soundstage to the left and right compared to many of the other speakers I have used. I typically work with a generous toe-in, aiming speakers just to the outside of the respective ear. The challenge in such a setup is the tendency of the center image to be “sunken” (further away) relative to the right and left channel. It does add depth to the performance and gives the sensation of being mid-hall versus the front hall, where it seems one is plastered against the stage. It also tightly focuses the center image, an effect I much enjoy.

The movement forward of the center image was not shocking, and as one becomes accustomed to it is quite pleasant. My assessment is that the wide midrange and treble band across the midsection of the speaker is the primary cause of the more intimate center image. There is no sense of the sound field being chopped into segments left, right and center, or of gaps between them. With certain albums this is most helpful because not all vocalists are equally powerful, and in some recordings the instrumentals tend to smother them; I am thinking here of live recordings especially.

It is impossible to experience the U-4iA without the solidity and dynamic punch of the bass immediately asserting itself. Other panels I have used, including the King III, which reaches the same 32Hz threshold, do not have the visceral impact of the U-4iA. While not on the level of larger dynamic speakers with multiple 12” or larger bass drivers, the U-4iA did a remarkably fine job of infusing the cement and thick carpeted floor with some tactile sensation, an unheard of event in my room for a panel speaker sans subwoofer. The bass of the King III is spread out as typical with big panels, but the concentrated force of the U-4iA’s bass via the Bass Focus technique is mighty impressive. LF in massive doses on remixes normally kills panels, but the U-4iA handled them like a champ. It must be understood that I am not listening at club or live levels, as I find no advantage to doing so. Listening at approximately 85-87dB did not seem to stress the speakers at all in the lower frequencies regardless of frequency extension.

I heard my first big crunch of stator crackle when I played the Poem of the Chinese Drums at about 90dB. Thankfully, the incident of the crackling is explained thoroughly in the Manual, because if an owner would hear this without understanding he might think his speaker was blowing up. It was fixed in a jiffy by a quick turn of the Bias control. In my initial setup I played more conservative music, but when I introduced the extreme LF the crackling showed up again and two minutes of adjustment banished it. It is a testament to the U-4iA’s good design how close to the limit it can be run, losing little of its sensitivity to accommodate powerful bass. Grace Kelly’s “Ain’t No Sunshine” features a meaty electric bass, and as I trickled the level upward it was the Son of Ampzilla II, a rich and tonally warm amp, that ran out of steam before the U-4iA hit its dynamic limits. The U-4iA’s bass hangs tight when pushed hard better than the King III.

Depending on the music, the amount of bottom-end energy could be excessive and would call for tonal adjustments to the speaker. Hootie and the Blowfish’s “Use Me” continued the impressive demonstration of the U-4iA’s bottom-end capacity, but was so overtly present in the lower frequencies that it was in danger of overrunning the upper half of the spectrum. I adjusted the midrange and treble to +3dB to compensate and an acceptable balance was restored. To my ear, leaving the tonal controls flat brings a more “tube like” character from the Sound Lab, versus adjustment upward of them bringing out a touch of solid-state forwardness. Note that this effect can also be further increased or decreased to one’s satisfaction by proper selection of cables.

Another word about the Poem of the Chinese Drums; the U-4iA exquisitely renders the nuances of the mallet and drum skin interaction. With quite a large number of speakers, mostly dynamic or hybrid dynamic, the thump of the mallet whacking the drum comes off as a shuddering burst, an LF punch that has little character of other instruments such as piano and saxophone. To my delight, a splendid amount of the subtleties of the drum were retrieved by the U-4iA. Usually at that frequency, an electrostatic speaker coughs out a stressed throb, but the musical integrity of the LF created by the U-4iA was exemplary. This gave me the sense that it was more powerful than the rated 32Hz.


Changing the landscape

For my second system I swapped in the Wyred4Sound PCOCC Premium USB Cable and SST Thoebe II Preamp/DAC, all reviewed along with the Son of Ampzilla II. I placed the Verastarr Grand Illusion PC on the Thoebe II. The remainder of the system was the same.

Initially I swapped three USB cables: the Silnote, Wyred4Sound and an inexpensive Furutech Silver GS, which sounded thin, vacant and colorless compared to the others. The Silnote edged out the Wyred4Sound in this configuration in terms of cleanness and richness. It took only moments to hear that this was a complimentary pairing for the U-4iA. There was a magic about the Son of Ampzilla II amplifier and the U-4iA that reminded me of the Pathos Classic One MkIII amplifiers in Mono mode, which could be paired with nearly any components to create a satisfactory experience. The Son of Ampzilla II is a push-pull solid-state amplifier, and though it is 200wpc it drove the U-4ia as no other amp solidly. Even the lovely Red Dragon S500 class D amps in Mono mode at 1,000Wpc did not quite have the fortitude of the push-pull Son of Ampzilla II. It has the richness to get by as a tube amp substitute and the muscle to make the U-4iA mimic its larger siblings if slightly under-driven.

I am constantly amazed by the change that one component or a cable can produce in an audio system. Though I have been doing this for years it still thrills me and surprises me. The sharp reader may notice that the essential difference in the system was subtle, moving from a DAC with a preamp function to a preamp with a DAC built-in. I discuss the implications of this in the SST review. “Cool Man Cool” by Grant Geismann had a generous amount of the pop and boogie that I normally associate with the Vapor Audio Joule White 3 Speakers, a quick and ultra-tight dynamic speaker. The smallish form factor when well driven made the U-4iA sound intense, concentrated more so than expected for an electrostatic. Returning to Hootie and the Blowfish’s “Use Me” revealed I had forgotten to turn down the Bass tone control on the Thoebe II from previous use, yet I preferred it to the flat setting. The overall impact in the Bass was greater, yet the tonal balance also was better. It would be a pity if the pairing of SST components brought about a worse result! There should be synergies attained when a company’s preamp and amp are used together. This is not always the case, though, and I often find a superior result from mixing brands of preamp and amp.


Two sets of tone controls?

The Thoebe II also has tone controls that I extolled in the review. I really liked the subtle yet efficacious performance of those controls, and they operated as I would expect a proper tone adjustment; I struggled to detect sonic degradation from their use. Now, with two sets of tone controls, one on the preamp and the other on the speakers which one would prove most beneficial? The bass control on the electronics plate of the U-4iA had much less potency than the tone control of the Thoebe II. The initial +1 bass setting of the Thoebe II brought greater change to the bass than the +3 setting on the speaker. That might be expected as Roger was looking for subtle iterations of bass presence, while a preamp with tone controls might be expected to range more widely and provide quite a boost to bookshelf speakers. With floorstanding speakers the influence was prodigious. I elected to keep the U-4iA settings flat and adjust the tone with the Thoebe II.

Repeating the same song list everything was riper and more fleshed out. The center image was slightly more diffuse and recessed again, but no less pleasing overall. The Poem of the Chinese Drum was no more detailed than with the Exogal Comet DAC, but was even warmer, and the finger work of Grant Geismann’s guitar playing was smoother. There was a closer affinity between these two systems than many others I build. While the Exogal Comet was somewhat lighter and brighter and the Thoebe II heavier and darker, neither was unacceptable. A room of listeners would likely be split down the middle in terms of preference between these two systems. It showed the U-4iA could be pushed toward the “lighter” end of the performance spectrum or the “darker” end without harming its charm.


Introduction of Salk Sound StreamPlayer Gen III

I have forged a review of my first dedicated file server experience with the Salk StreamPlayer III and I can hardly say enough about how revelatory it has been. Fans will read plenty about this digital sea change in my systems, but suffice to say here that the Mac Mini has been forever banished! Thus, the system morphed again to compare two iterations in which the only difference was the amplification; in the first instance the Red Dragon S500 class D amps in Mono mode at 1,000wpc, and the other the relatively more physically imposing but sonically reposing First Watt J2 JFET Amps sporting 25Wpc:

  • Salk StreamPlayer III
  • Silnote Epirus USB Cable
  • Exogal Comet DAC with upgraded power supply and Verastarr Grand Illusion PC
  • TEO Liquid Reference MkII Interconnect (RCA)
  • Red Dragon S500 in Mono Mode with Clarity Cable Vortex PCs
  • OR
  • First Watt J2 JFET Amplifiers (stereo amps; use of one channel only as faux mono amps such that the power supply serves one channel)
  • TEO Liquid Standard Speaker Cables
  • Ultimate U-4iA with Silnote Poseidon GS PC


Starting this system with the Nelson Pass First Watt J2 amps caused a jolt, and a not altogether pleasant one. When a significant change has occurred to an audio system the owner has to first give time to adapt to the change, and it can be a jarring experience. The reader needs to take note that this was expected to be a challenging system as the amplification is admittedly inadequate. I would not run the U-4iA with anything less than 200Wpc, but I have always been a fan of big power. Roger reassures that several times in shows the big Sound Labs have been run with moderate tube power and have acquitted themselves well. I wanted to test it out for myself, but I would use lower power, 25 Watts per channel.

Here was a fundamental shift from a mellower, bottom-end fortified sound to a far brighter, seemingly upper-end emphasized performance. The canyon of bass depth shrunk to a chasm and the visceral aspects of the listening all but disappeared. As the Thoebe II with its powerful tone control was no longer in the rig, I found myself in short order upping the bass control of the U-4iA. Still, there was no way to capture the same result because the speaker was fundamentally underpowered. For the U-4iA to sound overwhelming it must have high power and high current. If all that is played is chamber music and there is avoidance of all LF, then one could perhaps make a case for this setup, but it would take careful choices of cables, including power cables, to do so. In my estimation this is akin to climbing a snowy mountain without climbing gear; it’s an uphill battle that is made unnecessarily difficult due to the mismatched amplification.

There is absolutely nothing wrong with the U-4iA or the J2 Amps, however they are not electronically ideal candidates for each other. With a speaker like the U-4iA you do yourself a disservice if you do not find proper amplification. The right amplification does not have to cost a fortune, as the Red Dragon S500 took to the U-4iA like bread to butter. The poor U-4iA was so disadvantaged by the J2 Amps, which were remarkable with the appropriate type of speakers such as the PureAudioProject Trio15 Voxativ under review, that I quickly replaced the J2s with the Red Dragons. Some people in this hobby have been very poorly guided to think that as long as one has adequate power the sound will be as good as can be obtained. Note well, adequate for the High End usually means average and that means unexciting in the long term. The prescribed minimum power of 50 Watts specified in the Manual of the U-4iA will get the speaker to work, but nowhere near the level it is capable of achieving. An extreme comparison of the 25Wpc J2 and the 1,000Wpc Red Dragon S500 reveals this clearly. Yet, I encountered one uniquely notable exception, which I discuss below, the Exogal Ion PowerDAC at 100wpc. It is a special case where the relatively lower power rating for amplification used with an electrostatic speaker belies the performance of the Ion PowerDAC. The bottom line is you want to make the U-4iA dance, not shuffle, and the amplifier makes all the difference.

The aforementioned Red Dragon S500 class D amps with their Pascal module-based sound have been my economical amp darlings for about a year now. They are the only class D amps I have used where my friend-critics visiting do not complain of the class D sound. I had to work a bit harder to get to that ultra-supple sound that the SST Son of Ampzilla II had, but I succeeded. The solution to the anemia from the mismatched J2 amps came in the form of retreating to these remarkable 12-pound bricks of class D power. A slumbering giant had been awakened, and a close approximation of the macrodynamics of the Son of Ampzilla II returned. I was falling in love with these Sound Lab speakers now. Given the proper front end they arose to challenge dynamic speakers’ immediacy while retaining the classic ESL speed and openness.

The insertion of the LampizatOr Big 7 DAC, which like the Exogal Comet has an internal preamp, produced a setup that could perhaps be a contender for a best of show award. LampizatOr jacks up the output of their hybrid DACs such that one has to match them up well with gear or else the speakers will be overdriven. Considering that I had 1,000 watts on tap and the juiced output of the Big 7, I was ready to control the U-4iA!

The Lampi Big 7 is a warmer, more romantic DAC than the Exogal Comet. The Comet is sweet like white sugar and the Big 7 is like brown sugar. Here was a combination that made the U-4iA sing enticingly. The Big 7 is a tube DAC and the presence of tubes with more than adequate power brought the best performance thus far in the review. Note that the power was solid state, but the source was tubed, which captured the “best of both worlds” in this system for audiophiles who cannot tear themselves away from thermionic valves.

Partnered with the LampizatOr Big 7 and Red Dragon S500, Marcus Miller’s “Higher Ground” sprang to life with each of the bass notes popping with energy. It’s a particular pleasure to hear a very well recorded electric bass piece, and the U-4iA can handle the dynamics as well as open up the notes to hear the vibration of the strings in the air. Even when the string vibrates against the fret board it was clear to discern. Singer Sarah Jarosz is becoming a well-known artist in the audiophile community for her distinctly enchanting voice. I thrilled to how the U-4iA rendered her song “Green Lights.” There are backup vocals along with her at the onset of the piece and in a lesser system it sounds like an effect added to her voice. However, with the U-4iA those backing vocals were teased out for full enjoyment.

Systems with the U-4iA were moving steadily from performance oriented to easeful listening. It can be tricky to tame an ESL such that one can spend longer time periods in front of it. The U-4iA, like all ESL speakers, takes a bit of massaging to elicit enchantment, but it responds readily to component and cable changes, making it very likely that you can tailor it to your pleasure. I do not subscribe to the viewpoint that extreme performance and extreme ease are incompatible, necessitating that one back off from precision in order to gain a relaxed listening experience. On the contrary, I begin to relax when a system sounds utterly real, and that requires extreme precision.The less accurate the speaker, the more problematic the result, and it’s not fun to sit in front of a high dollar rig and hear problems. The U-4iA offers very, very few potential problems and makes it most likely that you can obtain the sonic signature you seek with both precision and a relaxed quality to the sound.

12 Responses to Sound Lab Ultimate U-4iA electrostatic speaker Review

  1. Jerry Belben says:

    Wow!!! What a thoughtful, descriptive and moving review. Thanks for introducing me to a speaker that I had no previous knowledge of. ( I use PSB Image Tower 3’s and Prima Luna Dialogue HP Integrated Amplification) can you compare and contrast the PSB’s to the Sound Lab u4iA’s?

    Also I am in the market for a DAC and up to this point I have been leaning towards the PS Audio Directstream. Can you compare and contrast the two and if you were buying a new DAC what would you choose? Lastly do you have any reason to believe the results you achieved with the Excel Comet DAC with upgraded power Supply would be replicated with another system such as mine?

    Thanks again for a thorough and thoughtful review?


    Halifax, NS

  2. Miguel Dunkelberger says:

    As an owner of SoundLab A1’s I can attest to the outstanding customer service SoundLab offers. I shipped my circa 2004 electronic plates to the factory for the updated Torid and hot rod upgrade. You deal with Dr. West and he is a very nice man who accommodates custom requests. In my case, I asked to have silver WBT binding posts installed and the work is flawless. SoundLabs are the pinnacle of electrostatic technology and I for one will not consider cone based Speakers again.

  3. alan trahern says:

    Correct me if I’m wrong but I believe a 12 db per octave filter is a second order, not fourth order.

  4. Jerry,
    God’s Peace to you,

    PSB makes a high value speaker; I have always admired that in a speaker company. The performance of the U-4iA is quite different than all moderately sized floor standing dynamic speakers. Chiefly, the scale of the soundstage and coherency, the sense of being woven as a tapestry, are the most striking first impressions. The level of detail achievable is first rate. Some people adore panel sound and some do not, but you should endeavor to hear a good panel speaker; you may be smitten by it.

    I have heard PS audio gear a fair bit in the past and have heard their DACs. I had the PerfectWave DAC in my room for a week and decided not to review it. The Exogal, on the other hand, mightily impressed me, especially with the Ion. YMMV.

    I believe you would realize similar benefits by moving to the Exogal Comet and Ion, however, for many reasons you would not have replicated the U-4iA with those components and the PSB speakers.

    Douglas Schroeder

  5. William Juch says:

    To prevent confusion the nomenclature of the entire Sound Lab design has been changed. U-4iAs have been renamed U-545s; U-1PXs are now U-745s. There are now Sound Labs from 5 feet, 6, 7, 8 9 feet tall to fit different listening requirements in the Ultimate, Audiophile, and Millenium series. (only the U-745 and U-545 are offered.) All panel speakers now use the Consummate backplates comprising the “Hot-rod” super-premium components and the Toroidal Two transformers as was noted in the review. You can check my website below for current information.

  6. Russell Dawkins says:

    I am wondering about the sonic differences between the Ultimate 545 and Majestic 545 Soundlab speakers, with the Ultimate vs Majestic version of the same dimensioned speaker selling for $21,650 and $13,450, respectively.

  7. Russel,
    God’s Peace to you,

    Yours is an astute question. Though I have not done a comparison, I recall Roger West telling me that the new frame of the speaker was a profound improvement to performance. I am unsure whether the Ultimate and Majestic series uses the same power supply; that would be significant. Beyond that I direct you to discuss this with Sound Lab or persons who have sold or owned both.

    Douglas Schroeder

  8. Steven Klein says:

    I just received my Majestic 545 today! Roger told me all 545’s use the same electronics and panels and it’s only the frames that differ. As for sound Dr West says there’s small differences.
    Dealer disclaimer

  9. William Juch says:

    U-645s are now available! Contact your dealer for recommendations for your size room. Sound-Labs are like a “up-stream component analysis” tool. Very astute comment about Magicos and other dynamic speakers; now horn enthusiasts are waking up, too. With Bass Focus, you can now enjoy reliable electrostatics with “slam” and life-like coherence.
    Not having read it in some time, the above was a very thoughtful review. Dealer disclaimer.

  10. gary brandwein says:

    Doug-I might have missed it, but can tell me the size of the room that auditioned the speakers in. Otherwise well conceived exciting review, that let me bursting with curiosity. Thanks!

  11. Gary,
    God’s Joy to you,

    The listening room I have is 13′ x 23′ x 7.5′, which may seem smallish, but it is a custom built room for audio and can accommodate larger speakers well. The Sound Lab worked very well and did not sound constrained.

    I am not a proponent of the school of thought that one should opt for a much smaller speaker in a moderately sized room. What is typically forgotten in that perspective is that the holistic performance of the larger speaker is vastly superior to the lower models. I refuse to give up that superior performance, and I have not been disappointed with that decision.

    Douglas Schroeder

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