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Quad ESL 988 Electrostatic Loudspeaker

[Quad 988 ESL]
[Italian version]

Manufacturer Quad Electroacoustics Ltd
MSRP $7000 USD, when discontinued in 2006
Sensitivity 86 dB/2.83V rms
Impedance 8 ohms, nominal
Power handling Continuous input voltage (rms): 10V ; Programme peak for undistorted output: 40V ; Permitted peak input: 55V
Frequency Response -6 dB at 35 Hz; -6 dB >20 kHz
Power Consumption 6W
Dimensions HxWxD 94cm (37") x 67cm (26.4") x 31.5cm (12.4")
Weight 20.5 kgs, 46.1 lbs

Reviewer: Arvind Kohli - TNT USA
Reviewed: October 2012


One of the many reasons I love writing for TNT-Audio, is that, reviewers are also free to write about products that are no longer in production. Why is this important? Because, there are many products from the past that not only are in popular use even today, but also are very relevant and might even be outstanding performers. But though a product may have a long and loyal following - it does not necessarily mean the adulation is warranted. A revisit and comparison to renewed standards is needed every now and again.

One such product is the ESL or 57 electrostatic loudspeaker from Quad. I found a newer iteration of that classic (ESL 988) in the used market, in decent condition and for a reasonable price, and thought to evaluate it for myself. It is a forgone conclusion that anyone in this hobby has some familiarity with electrostatic technology, and has also heard of the Quad brand. If you have just entered the hobby, then take my word for it - this design and this brand are pillars in the history of audio products.

I am not going to proclaim any kind of expertise on the technology or history behind electrostatics speakers in general, or the versions that have been produced by Quad. But for the sake for comprehensiveness of this article, I will mention some of the more salient points that I have cobbled together from other sources. And also, to collectively list the aspects of this technology I believe to be most important in understanding what we have at hand here.

In 1957 Quad released their Electrostatic Loudspeaker (ESL); it was also called the Quad 55 or more popularly the Quad 57. Then in 1981, the next iteration, called the Quad 63 was released - named such since the design work began around 1963. And in 2000 the 63 was replaced by the 988, and also a larger 989 was introduced. And finally, in 2006 the 988 and 989 were replaced by the current 2805 and 2905 respectively. The hobby forums are littered with people swearing the pros and cons of the various iterations; I have no experience with any of the other models and thus will refrain from comment. But, essentially the core technology has not changed, and each iteration has attempted to further refine the model along. I happened to get my hands on this pair of the 988 in the used market, and feel compelled to share my experience of this iteration of a landmark product. TNT-Audio published a review of the Quad ESL 989 in 2000 and a follow-up in the same year.

One of the reasons full-range (or more precisely - crossoverless) electrostatics have always appealed to my sensibilities, is because of the way they approached some of the major problems of speaker design - by eliminating them. A crossoverless Electrostatic speaker inherently eliminates 2 major evils of loudspeaker design - completely - those being, enclosure colourations and signal degradation due to the crossover. I'm not talking about mitigating these evils - like a minimalist crossover, or a lightly braced cabinet might do - it simply does not have either a cabinet or a crossover at all - problem solved (And once again, less is more). The driver material (Mylar) found in modern electrostatics also have very low mass (a fraction of a gram, and a few millionths of an inch thick for the entire 988 panel), and hence very low inertia - they stop and start seemingly instantaneously; and then it is not surprising that electrostats are prized for their transient response, background silence and fidelity.

On the other hand, the design does have its own set of challenges. Primarily that, a single driver can only run so much of the bandwidth, so the response below 40 Hz (at least in my room) drops off quite a bit. And also treble response above 10khz starts to fall off a bit and then severely beyond say 13 kHz, and seems to be 15-20db down at 20 kHz. Now, to the OCD riddled audiophile who demands ruler-flat response from below 20 Hz to way above 20 kHz, this may seem completely unacceptable. But let's reserve judgment for a while and see what the listening tests reveal.


With dipoles of any kind, room placement is critical. And the Quad 988 seemed a lot more finicky about where it and I sat, than the recently reviewed dipole Hawthorne Audio Silver speakers. On a positive note, you can butt these up right against the side wall/s of a room with little to no effect - and that does allow for a lot of flexibility in many situations. But distance from the front wall is critical - and essentially the more distance you can allow the better, at least up to 6' away. Unless you have some serious room treatments, you probably will find 3' to 4' distance from the front wall to be a minimum requirement, any less than that seemed to really exaggerate the bass peaks inherent in my room.

For toe-in I always aimed the center of the panels straight at the listening spot. A slight deviation (say 5 degrees) did not seem to make a difference, but I was not able to set it up so that 2 people in my room could enjoy a reasonably balanced soundstage - this is a one listener speaker. The speaker also did benefit from being spread fairly far apart, an equilateral triangle between the speaker center and my ears seemed to be a minimum separation. I did not measure the angle, but I'd guess I might have been at the apex of a 90 degree angle to the speaker centers, before the soundstage began to fall apart.

[Quad 988 ESL, rear]

Also of importance is the aim of the center of the panel, relative to the ears. These speakers propagate the signal in concentric circles outward from the center, so as to produce a "point source" effect emanating from the center of each panel. It then at least theoretically follows that speakers are probably best suited for the center of the panel to be aimed at the ears, especially since the dispersion pattern is quite limited. If the speakers are placed directly on the floor, then center of the panel tends to aim at one's abdomen and not the ears, so some alteration is necessary to achieve aiming the center of the panel at the ears. There are 2 common ways to accomplish this. The first, by placing the speakers on a short stand and this has been a popular option for quite some time. The theoretical disadvantage being the potential for "floor bounce". The other option would be to elevate the front of the panel and introduce enough of a rake, so as to aim the center of the panel at the ears. I found the second option to make a small but occasionally noticeable improvement. I did not try the first option simply because I think it would be aesthetically hideous, and I am not ready to be kicked out of the house quite yet.

Aesthetically, the folks at Quad have done very well with what essentially is a big panel. Instead of trying to adorn it in vain, they went with the plain sock, footer and cap approach. And I think it works very well....and more importantly so does my wife. I was fully expecting her to be hysterical when she saw the tall and wide panels setup in the room. The one and only thing I would kvetch about is the darned 5 way binding posts spaced so they can fit the standard spaced banana plugs, but if you want to try spades or bare wire, then fuhgeddaboudit.


While the measurements of the 988 show that bass and treble response are indeed limited - the response below 40hz (at least in my room) drops off quite a bit, and treble response above 10khz starts to fall off, and seems to be 15-20db down at 20khz., I was shocked at how little to none of that measured deficiency could be noticed in the listening room without direct comparison to another speaker. On the low frequency end, I definitely heard a noticeable difference in extension with the addition of my ACI Force subwoofer (which incidentally integrates amazingly well with the Quads).

"Bass resolution test" (Chesky Jazz and Audiophile tests Vol2; Chesky; JD68)
The bass extension of the Quad's by themselves was perfectly acceptable, but it is the quality of the bass that was stunning, listening to a well recorded double-bass track has never been so satisfying. It was very easy to forget that I was listening to a recording, but instead I found myself immersed in the beauty of the instrument's sound. Having lived with the Quads for a while now, I am beginning to understand how important transient response is a component of the sense of realism.

On this track, I also did a direct comparison to my Dynaudio Contour 1.3 MkII. In terms of bass extension I did not really find any difference, but I did slightly prefer the Quads at a few spots on the track when it seemed more like I was listening to an instrument than a recording.

"Raga Bageshree" (Ustad Shahid Parvez; Live in Toronto; Sitar school of Toronto)
The treble notes on the Sitar were stunning....I have listened to this album many times, and have never heard the transients so real and effortless. I also happened to be able to ask my brother-in-law who actually recorded this album, and is habituated to the ribbon tweeter of a Clements Audio RT7 in his main rig - he did feel that some slight amount of detail was missing, but even then seemed very impressed by the treble frequencies that were being produced.

Here again, I also did a direct comparison to my Dynaudio Contour 1.3 MkII. And I found a very slight difference, where the Esotar tweeter did have a bit more treble extension in some instances. Not that the Dynaudio was a slouch in any way, but with the Quads I really enjoyed how clean the presentation was. The Sitar is capable of producing a very complex sonic profile, as each note is plucked the primary string continues to resonate for quite some time, and a secondary (sympathetic) string that is tuned to that note will also resonate. Now imagine how complex the sound becomes when several more notes are played before the first one has not died away yet. And we haven't even added in the effect of note-bending yet. Now, what is amazing about the Quads is that you can hear so much separation between not just the notes but also each layer of resonance and even the sympathetic strings. Listening to a single raag with all the focus I can muster leaves me drenched in music and completely exhausted.

"Drum kit recording; Tonian Labs test recordings)
This track was also used to compare the treble performance of the Quad to the Dynaudio Contour 1.3 MkII, via the cymbals on the drum kit. Here I did hear more extension on the Dynaudio than on the Quads. Now, without a direct comparison I would not have noticed anything missing, so the scale of the lacking treble is not large enough to matter on an absolute scale. And that finding makes sense - had the reduced treble been a real issue on an absolute scale, where you felt something was missing right away and without comparison to any other speakers, then so many owners would not have built such a loyal following for so many decades.

Other than the specific tracks above, I have now spent several months listening to these speakers over a variety of genre, format and recording quality. And the most enduring impression I come away with is that they make it easy to listen to music, I have once again found myself listening to a variety of stuff for hours on end - those long sessions that meander through a variety of artists and genres have been revived after many years. Specifically, there are three things that I have found these speakers do exceptionally well, and those are.

First, detail. Whether it is Kavi Alexandar speaking to Taj Mahal from across the cathedral on the last track of "Mumtaz Mahal"; or if it is hearing Ustad Shaheed Parvez fine-tuning his Sitar in the middle of a raag; these speakers have detail and in spades. It is not that the specific artifacts of detail cannot be heard on other speakers, but rather that on the Quads those artifacts are immediately and vividly noticed. In several cases, I heard an artifact (like the examples above) on the Quads, and thought to myself "Why, I've never heard that before". I assumed that only the Quads reproduce them and all the other speakers in the past did not. I then listened to the same section on another pair of speakers and do indeed hear those artifacts, albeit with less clarity. So, the artifacts were being produced by all the speakers in question, it is just that the Quads have the ability to separate individual components of a recording so well, that you immediately notice an artifact and think you have never heard it before. The cumulative impact of hearing, or more precisely noticing, all these additional pieces of detail increases tremendously the immersive quality of the listening session. You at times will feel that you have been transported to the recording session instead of being stuck in front of a bunch of gear.

Second, transients. This one I find difficult to articulate, though it is commonly talked about in audio circles. I do tend to notice it more on solo instrument pieces, especially those which produce sound by a striking or plucking action and also when a "sustain" is released on an instrument and the soundscape plunges into sudden darkness for a moment. It seems to me that the closer a speaker is able to reproduce the exact transient profile of the instrument the more realistic the playback seems. And with the Quads more so that every before, I was repeatedly drawn into the beauty of the instrument and lost focus on the task at hand of notating sonic qualities for the article.

Third, imaging. When properly setup, these speakers are very special in this regard. The instruments are very solidly placed, and the width and depth of the stage is as good as I have ever heard. I cannot remember which, but on one female vocalist track that I have listened to many times before, it seemed as if she was standing about 8 feet in front of me. It was so real it was eerie, I played that track many times over that evening to revel in the new found shine of my long time possession.

I have read some criticism of the Quads and electrostats in general, that they are not able to play very loud or handle a great dynamic range. I have no idea what that criticism is based on. I often do like to play music at levels that you would experience say at the symphony or a jazz club, and even that is pushing your luck with long term hearing damage. Rock concert levels (said often to peak at over 130db) are insane, and I would never judge any system by its ability to play at those levels. Might as well rate performance cars on their ability to tow yachts. There were many an occasion that I was able to comfortably play at what I am guessing was an average SPL of about 80-90db, with peaks I'd guess over 100db and found no sign of compression or the speakers shutting down. And my room is about 14' by 25' with two large openings into the rest of the house, in case you were wondering.

While most of the tests were conducted with my long time 40 WPC pure Class A Cayin 265Ai integrated amp, I also tried the 32WPC digitally aspired TBI Millenia and found a beautiful combination. I might just have to use the Quads to do an A/B comparison of the Cayin and TBI amps sometime soon.

My net takeaway regarding the 988 and the extreme frequencies is, that this is definitely not a full range speaker. But it is also not a "mid-range only" driver, there is more than enough to keep one very happy in the bass and treble - because what it does, it does so extremely well. Now, that is not to say that a subwoofer and a supertweeter will not enhance the overall experience, and I certainly intend to use my ACI Force with the 988's. And I do also intend to experiment with supertweeters in the future.


I cannot say enough how happy I am that I have found these speakers. I may possibly have found the pair I am going to spend the rest of my life with. If you can provide for their placement requirements and are not going to obsess about the lack of extension at the extreme ends, these are outstanding speakers.

Gear Manufacturer and Model
Digital Disc Players Denon DVD-3910 with Underwood mods (level2 + masterclock)
•Pioneer 414
• Sony DVP-NS755V
Phono Cartridge Goldring Elite(MC)
•Audio Technica OC9 MLII(MC)
Turntable Technics/KAB SL1200 MkII, with tonearm damper
Phono stage Cambridge Audio 640P Azur
Integrated Amplifiers Cayin 265Ai
• NAD 317
TBI Millenia
Speakers • Quad ESL 988
Dynaudio Contour 1.3 MkII
Triangle Electroacoustique Titus 202
• NHT Superzero


ACI Force
• Velodyne F1500R
Headphone Amplifier Practical Devices XM3
Headphones • AKG K701
• Sennheiser HD497
Connectors Various

© Copyright 2012 Arvind Kohli - arvind@tnt-audio.com - www.tnt-audio.com

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