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,

f456gt

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.

Duke

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