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Sound Lab Ultimate U-4iA electrostatic speaker Review

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The power supply and crossover

The power supply/crossover unit, that is the top plate of this structure that Roger refers to as the “electronic plate,” holds all the electronics, and the shell of the chassis surrounds it. There is no bottom to this enclosed power supply, but rather it sits open directly on the floor, which makes access for assembly easier. Packed along with it is the thorough and technically clear Owner’s Manual. The Manual suggests additional steps to assembling the power supply; however, it appears that Sound Lab now ships it fully assembled, calling for only a few well-explained and illustrated connections to make it operational. Access to the bolts anchoring the panel to the power supply is through the open bottom. If the speaker is assembled on carpeting one can gently lay down the speaker’s panel on its face, guide the power supply – careful, it’s about 70 pounds – to the proper location on the back of the panel with the integral heavy gauge bolts protruding, and affix it with the nuts provided. Do so carefully as the positioning of the power supply is done blindly, another reason to have a helper if you are unsure of yourself. Not to overly worry, however, as any scratch on the power supply while aligning it will not be seen because it is flush with the panel’s frame. Three color-coded leads, red, yellow and black, are connected from the panel to the power supply. The red and black leads connect the front and back panel’s stators to the high voltage output (secondary windings) of the audio transformers, and the yellow lead connects the panel’s membrane to the bias supply. The Owner’s Manual, in an exemplary fashion, explains all these steps such that anyone handy with a socket wrench should be able to complete the assembly.

The top of the electronic plate has the expected 15A IEC connector for the power cord, which is mounted vertically as opposed to most components that accept the power cord horizontally. You might need another foot or so in length of the power cords to reach outlets when the speaker is in the preferred position. Best to consider this prior to final placement, although I would not hesitate to get new power cords for the speakers if positioning would be compromised in order to reach a power outlet in the room. My biggest gripe with the build of the speaker is the miserably invisible speaker post markings. It is neigh unto impossible to see the miniscule “+” and “-“ near the speaker posts. In anything less than direct sunlight or a flashlight held right at the posts it is difficult to even locate the markings. Sound Lab should change this immediately. There is no discussion of the orientation of the terminals in the Manual, but regardless the markings need to be impossible to miss. It is a statement of overall satisfaction that this was my only gripe about the speaker.

There is a Bias adjustment along with three equalization adjustments labeled “Bass, Midrange, and Brilliance (treble)”. The Bass and Midrange controls have four steps which operate in 3dB increments marked; -6dB, -3dB, 0, and +3dB, while the Brilliance control affecting the treble is continuously variable, devoid of numeration, and is at a flat setting at the 3 O’clock position. I did not see any discussion of the Brilliance control in the Manual and would expect this to be updated in the future.

When I adjusted the Brilliance control via the dial atop the electronic plate, I was surprised that it seemed to have no effect to the point that I would say it failed my Law of Efficacy. In every instance where I have been able to adjust electronics while standing near speakers, even behind them (excluding)dipole speakers, I can easily hear adjustments of +/-2 or +/-3 dB, whether adjusting the bass, midrange or treble. Even switching out jumpers on bi-wireable speakers confers an immediate change that is easily heard. It seems the Sound Lab Brilliance control is exceptionally subtle in its effect and, as Roger indicates, not a make-or-break adjustment. I suggest the user set it and forget it and focus on the aforementioned Bias adjustment, Bass and Midrange controls.

Adjustments to the Bass and Midrange tone controls were instantly discernible as I stood behind the speakers and changed them. I concur with Roger that these adjustments are very handy for tuning a system. Some might question the use of tone controls on a top end speaker, however Roger points out that there are several conditions which might influence the sound of the system, including room acoustics, the “personality” of the assembled gear, and the variances between music sources. A degree of control can compensate for system, acoustical and recording deficits.

I found the Bass and Midrange controls highly efficacious. As the speaker is rated to reach 32Hz +/-3dB and I am accustomed to much lower bass, I wished to extract as much as possible from the speaker without distortion. A setting of +3dB was sufficient to lend added weight to the bottom end without overloading when listening to LF heavy music. My room is quite well damped, and similarly a boost of +3dB to the Midrange was sufficient to add sparkle to the upper end. A local Sound Lab dealer who heard the system and who uses a concert piano as a gauge of performance quibbled about my +3dB setting and asserted that his recordings were better served by the flat Midrange setting. To me, the reversion to the 0 setting buffered the immediacy of the piano, and I pointed out that the microphone placement in the recording was right at the piano versus backed off from it. We didn’t agree, but the speaker proved highly agreeable in that it could accommodate either of our preferences, making us happy with our preference. The U-4iA can eliminate hand wringing from frustration to obtain that last smidgen of change that would make a listener relax fully.

The last user calibrated control is the Bias adjustment, which sits along with the other controls on the top of the electronics plate and is changed with a small flat-head screwdriver. I mention it last, but it is necessarily the first adjustment made when setting up the speaker. The Bias supply places a fixed charge on the membrane. Too low of a setting and the speaker will have lower sensitivity, which means the amp will not drive the speaker optimally. If the setting is too high a crackling-like noise will be emitted from the panel. The noise may be intermittent and reveal itself only at peaks. The optimum setting is about 1/8 rotation of the control counter-clockwise from the position where there is incident of the crackling sound. I adjusted the Bias twice; a second tuning was necessary the first time I listened to extreme low frequency music at higher levels. The Bias is line regulated so that once it is set any fluctuations in the AC line voltage will have no effect on the speaker.

New developments for the panels

We will get to the systems I set up and listening impressions shortly, but first we should appreciate the enhanced electrostatic panels. Roger shared more information about the panels than some manufacturers do about their entire product. Painstakingly, he ensured I understood their design principles and performance enhancements. Several terms used in describing the new technology caught my attention, including “Bass Focus,” “single monolithic diaphragm” and “distributed resonance.” Being aware that a variety of layouts are employed by manufacturers to orient the bass, midrange and treble sections of an electrostatic speaker, I peered with a flashlight into the innards and was surprised to see segmentation denoting larger sections at the top and bottom decreasing in width moving toward the middle. My first thought was, “This is a D’Appolito setup!” A D’Appolito distribution of the drivers forms a mirror image with the Bass/Midrange on top and bottom and the Tweeter in the middle (aka MTM). It was named after its inventor, Joseph D’Appolito, who used it to address lobe tilting of a more traditional TM or MT configuration. It allows the tweeter and midrange drivers to be placed into a simple front baffle and addresses the need for physical or electronic time alignment between the tweeter and midrange.

However, that was not what caught my fancy. Rather, it was the mid-height wide band across the middle, the side-to-side width of the tweeter section, which impressed me. I have been spending what little free time I have when not engaged in reviewing to experiment further with my Landscape Speaker method. Early on I used the quasi-D’Appolito configured Daedalus Ulysses placed on a custom Sound Anchor stand having complete adjustability to put the speaker on a horizontal plane. The method sonically mimics a picture taken from landscape perspective versus a portrait perspective. The Ulysses was interesting enough to merit further experimentation, and I have proceeded to move to a second phase of the Landscape experiment, which will be revealed in time. To my ear, the width of the U-4iA’s midrange and treble is comparable to the Landscape method I employ, the primary difference being that the Sound Lab carries the width across the entire frequency spectrum and the complete height of the speaker, ergo a panel speaker.

Here is where an electrostatic speaker shines, in the vastness of the acoustic canvas it paints with vivid colors. Big scale sound is a big pleasure to the ear and is a primary reason why panel speakers continue to find favor, especially for recordings of large-scale performances. This smallest Ultimate cannot compete with its larger siblings in the absolute scale of the performance, but it competes exceptionally well with even large dynamic floorstanding speakers of great price.

The Kingsound King III, another sizable electrostatic speaker that I reviewed, employs a far different method of arriving at the same goal. The King III is what I call an LSESL, or Line Source Electrostatic Loudspeaker, with seven bass drivers longitudinally oriented one above the other, and alongside three Mid/Tweeter drivers oriented vertically, one above the other. The most apparent and critical performance difference is the King III uses multiple individual drivers versus the U-4iA’s single driver.

Here is where the distinctions become somewhat blurred in my view; the U-4iA is also segmented in a sense as Roger describes the driver membrane: “Specifically, the membrane movement is blocked at calculated vertical intervals, based on a distribution ‘law’ that equalizes bass response.” The movement seems to be dampened at critical places similar to how a piano string can be dampened by the hammer that rests against it. Judicious placement of blocking to use the peak resonances to advantage is a process Roger calls “distributed resonance,” and it begins at the location where the U-4iA’s membrane produces 32Hz.

The intervals, and there are several, occur more frequently as they move from the upper and lower limits toward the center – these are the cross sections I saw initially and account for the sonically D’Appolito-type distribution of sound from the speaker. The critical damping, along with 12dB per octave (2nd order) filters, allows the single membrane to radiate the necessary spectrum of sound. As Roger states, “All of our panels are based on the principle of a vertical line source.” Additional treatment of the membrane is done vertically by use of “radiating areas” which are attached to the top and bottom of the driver, and which seem to cause a bend in the Mylar, thus producing a curvilinear result. To the untrained eye they look like additional blocking, so that the driver looks to be segmented with a quasi-checkerboard appearance. Roger impressed upon me the singular nature of the driver membrane, yet for lack of better term it is parceled to achieve the curvature and frequency distribution.

These methods resulted in an increase of +6dB dynamic range in the bass, which was termed “Bass Focus,” and has been adopted from the development of the U-4iA and applied to all Sound Lab panels. Combined with the most advanced electronic plate to date, “which uses the Toroid II audio transformer and Hot-Rod super quality audio components,” Roger states the U-4iA is endowed with the expertise of Sound Lab at the highest technological level. Incredibly, it captures the same frequency response specifications as the largest model, the U-1PX! Even more incredibly, this particular expression of Ultimate series speakers fits into my room!

All this technological talk is daunting, but the speaker is wonderfully user-friendly. A lot is going on under the surface, but the user only needs to be concerned about what is on the surface, the obvious controls. Once the speaker’s Bias is dialed in, a simple task, and the preferred adjustments made to tone, the owner sits back and relishes the results. A single pair of speaker cables is required for the robust metal binding posts. The owner may wish to obtain a proper speaker binding post wrench to ensure that if spade terminations are used they will be cinched down well and not work their way loose. During the extensive review period the speaker performed flawlessly.



Initially I placed the speakers at the position where I use all panel speakers, approximately six feet from the front wall and about 20” from the side walls. This allows an 8’ gap between them with the listening chair located 12’ from them. However, with experimentation I settled on anarrower placement, approximately 7’ between them, and this afforded an even more solid soundstage with no softness in the middle. I recommend that owners try both wider and narrower setups to select their preference.

The owner can use the U-4iA in a perceived deeper position, with the speaker placed almost against the front wall. Roger urges that in such a configuration the toe-in must be severe, on the order of 30 degrees, to avoid reflections off the front wall (behind the speakers). For more distant placement from the front wall one may start with the speakers parallel to the front wall and move the speakers in by 10-degree increments.


Power cords

Each of the speakers requires a 15A IEC power cord. I try not to use anything longer than 2 meters. Roger feels that the U-4iA’s power supply is so robust and impervious to AC line noise that it would be inconsequential to change power cords from the stock cord supplied. I disagree based on my usage of not only this speaker but also the Kingsound King and King III electrostatic speakers. I regularly swapped the Silnote Poseidon GS and Clarity Cable Vortex power cords in this review between the speakers and the amplifiers to create an instantly noticeable, highly efficacious shift in tonality and sound staging.

I am not surprised at Roger’s response, as I have encountered several manufacturers who, according to design principles, eschew aftermarket power cords. However, I do the comparison by actually trying different ones, and the real world changes are to my ear important enough to merit special attention by the owner. If you are skeptical of my findings, I encourage an experiment by using a $100 second-hand power cable by a reputable manufacturer, as even an affordable power cord can reveal discernible changes. When you spend $20K+ on the speakers you owe it to yourself to try such a low cost method of enhancing the system.


Technological comparison to Kingsound King III

Aside from the curvature of the diaphragm versus the King III’s multiple flat diaphragms, how does the Sound Lab panel technology differ from that employed by Kingsound? The U-4iA seems to maintain the integrity of a single driver while forcing it to operate like individual ones. Avoidance of comb filtering resultant from use of multiple similar drivers seems to be the most direct benefit. The U-4iA has a far greater sense of the sound being “cut from the same cloth” than the King III. While the King III has larger scale, for it is a taller speaker, the U-4iA has an edge in absolute cleanness and a sense of more speed in transients due to the single driver with blocking technology. In fact, the coherence and cleanness of the U-4iA reminds me of extreme high-end dynamic speakers. Throughout the review process I kept thinking that the U-4iA would be an electrostatic that could draw some hard-core dynamic speaker fans away from Magico, YG Acoustics, Rockport, and the like. This is no disparagement of these other speakers, but rather an endorsement of the tightness and completeness of the imaging the U-4iA produces.

I am in amazement at the solidity of the images that the U-4iA produces. Quad electrostatic speakers have been favored for their coherence due to the circular distribution of the electrostatic elements, vaguely like a concentric driver. In the U-4iA we see a similar coherence. The Sound Lab does remind me of a Quad, but with a far higher performance level and, in my opinion, more reliability. Several years ago I attempted repeatedly to get a review of either the Quad 2912 or 2812 via emails and phone calls, but never received a response from the North American distributor. Not long after I saw the distributorship was lost. The manufacturing was outsourced to China, and I heard enough rumors of build quality problems that I was no longer interested. I understand that now Quad is back in North America, and I wish them success. Sound Lab has been refining its technology and has a tradition of good customer service. In this initial run the U-4iA seems to be an endearing and enduring design. You can hardly hurt it, as when you over drive it and the speaker crackles, you turn the Bias down and onward you go!

The U-4iA presents a more compact, more focused experience than the King III. The bass seems far more potent because it is more gathered, yet the Landscape type of distribution by the midrange and tweeter gives every bit as much a sense of wide-openness in terms of width of imaging. One does not get the 8’ tall head singing with the U-4iA but rather a more true-to-life scale of the singer, as I have found with other Landscape systems. This is a critical point, as those with dynamic speakers will often condemn ESLs because they cannot produce a convincingly dynamic performance. That concern is eliminated with the U-4iA, as it is the most potent panel speaker per square inch I have encountered. Friends with audio systems containing up to 15” dynamic drivers were astounded by the dynamic output of the U-4iA, as was I. I was dumbfounded by the amount of acoustic energy the U-4iA could propagate and with fantastic precision. With these introductions, let us proceed to the listening experience.

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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