Sealed subwoofer for ESL-63

I am looking for owners who have successfully integrated their QUAD ESL 63s with a subwoofer.

I recently bought a used pair of QUAD ESL63 and had them rebuilt, panels and electronics, this is my third pair. I have had several monkey boxes in between - Aerial 10T, B&W, KEF, IMF, Tannoys, Proac, Goldmund, Falcon Acoustics kits, etc - but the 63s are very hard to live without when you know what they can do.

My problem is that I am particularly fond of large-scale symphonic works such as Wagner’s The Ring , Beethoven, Mahler, Strauss, etc. but the 63s are very special and very frustrating used full range, they have limited bass and dynamics.

I am retired now and have a fixed income so I cannot keep doing what I did for fifty years, buy, experiment, trade and sell.

I would like to keep the cost of the sub to $1K max for a good condition, one owner unit.

Best regards,

The Vandersteen sub would be my first choice, but they sell for about $1500. In your price range maybe a REL or Martin Logan. I would get the smallest one they make, and if you can afford it, get 2 of them. The idea is to get something that will keep up with the speed of your ESL's.
You will eventually probably want a set.  Easier to set up and they sound MUCH better. The ultimate is 4 identical subs as you can play with the room that way.  The new Vandersteen sub with the bass EQ works awesome with the panel speakers.  I've heard that set up numerous times as they are very very fast and set up properly, they take on the same sound as your main amp.  To me, that's the best thing about their integration.  That 12 band EQ has tamed my own room a great deal and smoothed everything out. (I have the Quatro's with built in sub/amp .

Dipoles have smoother in-room bass than monopoles. In general, it takes two monopole sources (intelligently positioned) to approximate the in-room bass smoothness of one dipole source. And it would take four monopole sources to approximate the in-room bass smoothness of two dipole sources.

You may have noticed that people who try a single sub with their Quads or Maggies go back to no sub about half the time. You may have also noticed that people who try two subs almost always keep them. This trend continues as the number of subs increases. This is because the in-room smoothness improves as the number of subs increases.

And smooth bass = fast bass. I can explain this statement if you would like.

Imo a single equalized sub can work quite well for a single-person sweet spot. The larger the listening area, the less the ability of a single equalized sub to maintain smoothness throughout that area. Multiple subs intelligently positioned do a better job of being consistently smooth throughout the room. I can explain why if you’d like.

So if your sweet spot is small, a single equalized sub may be a good choice. If you want a large sweet spot, consider either two or preferably three or four small subs, and consider assembling kits to expand the buying power of your limited budget.

Best of luck with your quest!


Subwoofers are not dipoles. At these low frequencies they behave as an omnidirectional source. 

On your budget it will be tough to find anything good enough to match the crystal clear quality of the quad - you also really need a high end sub for bass heavy music like Wagner and as Duke suggests a couple of subs would be much better than one.

Two JL Fathoms would do well but that is beyond your budget. 

DIY might be your only option.
Look for a JL E110 used and use the internal line level crossover between your amp and preamp.  You'll be amazed.

There actually are dipole subwoofers---the OB/Dipole Gradient offered in the 1980’s for the QUAD 63, and the OB/Dipole now offered by Rythmik/GR Research. It consists of a pair of 12" OB-specific woofers mounted on an H- or W-frame---an open baffle, dipole sub with the Rythmik Servo-Feedback system, the only such sub in the world.

Ya’ll know Duke is a subwoofer expert, and his statement that dipole subs have smoother in-room bass than monopoles is, contrary to shadorne’s claim that "at these low frequencies they behave as an omnidirectional source"---an incorrect and mistaken notion, absolutely and incontrovertibly true.

A dipole sub has a null to either side (just like dipole speakers), propagating bass and bass-loading the room in one less dimension than an omni---not the width of the room. Consequently, fewer room modes are excited---less bass boom. That is an advantage inherent in dipole subs, and dipole speakers as well.

An OB-type dipole sub has one additional benefit---no sealed or ported enclosure to itself be a source of resonance or boom. As I described above, an OB sub has it's woofers are mounted on an open baffle, not in an enclosure. Lean, clean, and pristine!

Let me offer some clarification to my earlier post.

My statement that a dipole has smoother in-room bass is based on a paper written by James M. Kates and published in the Journal of the Audio Engineering Society in 2002.

It takes the ear a long time to hear low frequencies, relatively speaking. We cannot detect the presence of bass energy from less than one wavelength, and we must hear several cycles (several wavelengths) before we can detect pitch. If you stop and think about how long these wavelengths are, you’ll see that by the time we can hear low frequencies, they have already bounced around our little rooms quite a bit. So the room’s effects are all over the sub’s output by the time we hear it. In other words, perceptually we cannot separate the subwoofer(s) from the room - they form a system, for all practical purposes.

The idea with a distributed multisub system is, each sub inevitably generates a nasty room-interaction peak-and-dip pattern. But because the subs are intelligently scattered, these peak-and-dip patterns are all significantly different. The sum of these multiple dissimilar peak-and-dip patterns is pretty darn smooth, assuming we started out with four subs. This smoothness holds up pretty much throughout the room because at any location within the room, we have the summing of four dissimilar peak-and-dip patterns. And since smooth bass is fast bass (both literally and perceptually), the net result blends very well with dipoles.



I've got a pair of Quad 2805's.  I love pretty much everything about them but I would like a bit more bottom end.  I'm a jazz / funk  guy with the emphasis on jazz.

They are powered by a Primaluna Dialogue premium HP.

What would you recommend for a subwoofer(s) in the 2-3k range?

I live 300 miles from the nearest hi fi store and making the trip to audition usually means an overnight stay.

Thanks in advance,

Quad Esl 63’s are fast, to mate a sub well to them they have to be fast also. A well designed sealed sub with less than 10" drivers and with motional feedback would be the way to go, 12" or bigger and or ported tend to be slower and harder to mate with ESL’s

There is a sleeper of old that will suit and are very cheap s/h, and that’s believe it or not is a pair of old Yamaha YST-SW160’s or the more powerfull YST-SW305’s. These both use twin 8" drivers are are motional feedback controlled, and use linear amps, even though ported they are very fast and no doof doof sound, IE: accurate and detailed. They don’t go super low, but low enough to concuss the air in the room when needed.

Don’t bother with anything else from Yamaha, it’s all doof doof rubbish. Just the YST-SW160 or YST-SW305

Cheers George

Jzzmusician wrote: "I’ve got a pair of Quad 2805’s. I love pretty much everything about them but I would like a bit more bottom end... What would you recommend for a subwoofer(s) in the 2-3k range?"

I’ve owned three pairs of Quads and many pairs of SoundLabs, so I’m somewhat familiar with the superb pitch definition of a good dipole bass system. You can hear every little nuance of what the bass player is doing.

In my opinion, the most promising approaches to adding deeper extension to your Quads are probably four small monopole subs, and two dipole subs. Both approaches have similar smoothness across most of the bass region. Briefly, the more bass sources the better, and each dipole is like two bass sources, from an in-room smoothness standpoint. In both approaches, the bass energy from all these different sources bouncing around the room combines in semi-random phase to produce much smoother response than you’d get from a single sub.

Obviously two dipole subwoofers are gong to blend well with two dipole main speakers. But four small monopole subs, scattered around, have about the same in-room smoothness as two dipoles, so they also blend well with two dipole main speakers.

But there is an important difference:

At the bottom end of the bass region, where the wavelengths typically become quite long in relation to the room’s dimensions, a multiple monopole system would tend to have a rising response, because at these long wavelengths their outputs are effectively combining in-phase. And in-phase combining results in 3 dB more SPL than semi-random-phase combining.

On the other hand, at these long wavelengths, the in-phase and out-of-phase energies of the dipoles will combine to produce a falling response, because they are summing towards complete cancellation.

Neither is ideal. But the little multi-sub system has a trick up its sleeve: You can reverse the polarity of one of the subs! This actually results in smoother response over most of the bass region, and then no fat-sounding hump down at the bottom end of the bass region. Smooth bass is "fast" bass, and the net result is smooth bass that extends lower than a comparable dipole subwoofer system would go. And subjectively, the distributed multisub system has the impact that dipole systems lack. So arguably best-of-both worlds: Articulation and pitch-definition competitive with a good dipole, but with impact too.

Yeah I got a dog in this fight... four small dogs, to be precise. So feel free to take my comments with as many grains of salt as needed.


dealer/manufacturer/distributed multi-sub guy

Not to be contrary georgehifi, but the Rythmik 8" sub is no faster than their 12" or 15". All the Rythmik subs are servo-feedback designs, with the behavior of the woofers controlled by the s-f circuit. They all sound very similar, the Rythmik designer/owner Brian Ding citing higher spl output from the larger models, but no less sound quality. There are numerous Maggie, QUAD, and other planar speaker owners using Rythmik subs with their speakers.
I've had great luck integrating a REL Stadium with Quad 63's and later pair of REL Stentors with Quad 2905's. I had Jim Smith help me set up the 2905's and the results were seamless. I would highly recommend REL subwoofers, ideally a matched pair, placed behind your panels if you can put the Quads well into the room.
according to stereophile's measurements for your speakers drop like a rock at 80Hz which makes them excellent candidates for subwoofer integration.  
the key ingredients for perfect sub integration are as follows-
1) subwoofer with polarity invert switch
2) subwoofer with continuous phase angle adjustment 
3) subwoofer with high level (speaker line) inputs
4) subwoofer with flat usable frequency response.  
Some REL subs and JL Audio subs have these features / attributes which is why they blend seamlessly with a little work.
I have the JL Audio D110 integrated perfectly with Harbeth C7s and can recommend it for you application.
*inverted polarity switch helps to eliminate peaks in the response through summing.  
*continuous phase angle allows fine tuning to completely eliminate any peaks or cancellations by aligning the pulse with the main woofer at the crossover point.  
*high level inputs allow better blending because your sub sees the exact same signal your main speakers see.  run in parallel to your amps connections- it creates a benign high impedance load to the amplifier. 
*a flat useable response is what makes a sub sound musical- being able to play many bass notes and not be a one note wonder.  
The JL D110 is an excellent sub at it's price point.  
It’s all about getting the two different masses to behave as close as possible at the xover point.

For a sub to react as fast as an esl-63 at the xover point, it needs to have a reactance speed as close as possible to the speed of the 63’s at 80hz which has virtually no mass, hence the smaller lighter diaphragm/s sub driver/s will be closer, and to help them even more, a servo feedback will help again.

Cheers George
+1 avanti1960
Buy a Martin Logan Sub. After all they build Electrostatic speaker. I use one Depthi-i sub with excellent results with Crossover at 35. Seamlessly blends in and makes my 63 sound even better but without hurting the mid range purity.