Try an ATC C4 sub woofer. The ATC's were originally designed to get the low distortion and exceptional quality sound of the Quad 57 midrange but at much much higher SPL's and without the distortion inherent in other conventional designs.
ATC sub woofers are of the type of design that you do not notice that they are there - very tight and fast.
My friend runs a ZU sub and its super fast....it mates great with his dual concen mains that need a really fast sub.
I use a pair of TBI subs which work nicely with Quad 989s
The room is the dominant factor at bass frequencies. Not to say that different subs don't sound different, but the peak-and-dip pattern imposed by the room is quite audible, as is the progressive boundary reinforcement ("room gain") at low frequencies that makes a "flat anechoic" sub sound boomy and slow, and a sub that rolls off high and gradually sound tight and fast. The ear actually has very poor time-domain resolution at low frequencies, so the subjective impression of "slowness" is really a frequency response issue; in studies where group delay was digitally separated from frequency response, group delay proved to be barely audible on test tones and inaudible on music. On the other hand, frequency response anomalies were readiliy audible if they spanned a large enough portion of the spectrum (which happens routinely in the bass region).
Dipoles have been shown to have smoother in-room bass than monopoles, so this makes matching a pair of dipole main speakers with a single monopole sub often frustrating. The ear can often hear the discrepancy between the smooth upper bass of the pair of dipoles in contrast with the lumpy middle and lower bass from the sub. Using two subs helps a great deal, as each sub will interact with the room's bass modes differently, and the two dissimilar peak-and-dip patterns will smoothe one another out. I advocate taking that one step further and using four small subs... preferrably, small subs that are tuned to take room gain into account.
I know it seems highly counter-intuitive to use a lot of subs when your goal is quality instead of quantity, but this is the best way to get the room to work with you instead of against you. And the elephant in the room is... the room. The multisub approach is effective at extending the smoothness inherent in a good dipole like the Quad 57 down into the low bass region.
Imo, ime, ymmv, etc.
The REL would be my choice.
I would buy the small Definitive Technology Supercube III, great little sub, you can connect it via the speaker terminal off your amp, or many other and multiple ways.
Very, very fast and deep little sub.
Read the subwoofer reviews in Stereophile by Larry Greenhill in the last few years. He uses Quads.http://www.stereophile.com/category/subwoofer-reviews/
Duke, thanks for your post. I always appreciate the science you provide in your posts.
On the other hand, frequency response anomalies were readiliy audible if they spanned a large enough portion of the spectrum (which happens routinely in the bass region).
How much was considered "large enough portion" to be audible? I agree that frequency response anomalies are really a matter of course in the bass, but if Dr. Toole's comment about needing 1/10th octave resolution to usefully expose bass response it seems to me that we're talking about small portions of the bass band. Did I make any sense?
I don't recall how wide a "critical band" is in the bass region, sorry. My impression is that it's less than 1/3 octave wide.
For those who wonder what I'm talking about, the ear/brain system "averages out" narrow-band peaks and dips across what's called a "critical band", which is approximately 1/3 octave wide over much of the spectrum. So in other words if we have offsetting peaks and dips within 1/3 octave of one another, the ear tends not to hear either one. If we just have a peak, then the ear will hear it, though if it's a narrow peak it looks worse to the eye than it sounds to the ear.
In the bass region, the room-induced peaks and dips are inherently too far apart for the ear/brain system to average them out, and as a result they are audible and objectionable. Higher up we still have numerous peaks and dips from room interaction, but they are so close together (and delayed by so many wavelengths) that they are relatively benign, even though they may look awful on an unsmoothed in-room frequency response curve.
Tieing back in to the multisub concept, each sub will produce a different peak-and-dip pattern so the sum ends up not only averaging out considerably, but the remaining peaks and dips are more numerous and thus closer together - giving the ear/brain system's smoothing mechanism a better chance to work in to our benefit. As a result, the subjective benefit of a multisub system is often greater than one would expect from merely eyeballing the in-room frequency response curves.
It's not necessary to use identical subs like in the system I build; in fact if the subs aren't designed with room gain in mind, we're probably better off with some of the subs extending deeper in the bass than others. The basic principle can be employed without spending megabucks.
I would recommend the Talon Roc subwoofer. This sub can blend with any speaker. The Seaton Submersive is excellent as well. While one sub can work if properly located and using bass traps and/or an eq to attain the smoothest response, use of multiple sub is a good recommendation as well. Good luck!
From ServOdrive to Carver's little true sub I've had a number of subwoofer systems in my HT, two channel, Bass rig, and small PA. Still, I know little of the mechanics of the room and sub relationship. I'm not a golfer either but I did hit through the ball once. When things are done correctly the sensation of both the ball and the sub can have striking similarities, you simply know its right.
Your getting close when you don't notice the sub's presence until it's turned off. IMO there is no such thing as matching a sub to a speaker. The process begins with blending the crossover point and gain to the speaker but the trick comes in the equalization of the subs output to the room. For this you need processing.
There are only a few consumer subs that have the processing built in to make this a simple adjustment for people without room analyzing and equalization capability. Even then some are better than others. For consumer HT and two channel it's my limited experience that Velodyne Digital Drive subs with high pass filtering are a clear stand out at this. For any other consumer sub I would suggest using Velodyne's SMS system.
I strongly agree with Duke that in both HT and two channel using two subs seems to be able to grip the room as well as creating a bit more air and stage in the two channel system.
Hi Duke, thanks for the additional information. Can you suggest any reference texts for this sort of psychocoustics information?
if we have offsetting peaks and dips within 1/3 octave of one another, the ear tends not to hear either one. If we just have a peak, then the ear will hear it, though if it's a narrow peak it looks worse to the eye than it sounds to the ear.
This would be useful in selecting candidate peaks to EQ. I wonder if any of the automated software is doing this.
I'd try a Vandersteen V2W. Quad ESL-57's are Richard Vandersteen's reference speakers, and I'll bet he has done some tailoring for the Quads low end.
I am using a True Sub.... and it's heaven.