subwoofers and panels don't mix

Just a thought - having never experimented - but could the issue be related to dynamics? A panel is not known for punchy dynamics (typically they compress audio signals and are preferred for classical listening)

...yet most subs are evaluated on their dynamic impact.

My suggestion would be to use an adjustable audio compressor on the sub signal so the sub can work in a "balanced" way with the rest of the audio frequencies from the panel....limit the dynamic range of the sub to match the panel.

A balanced sound will be correct at a variety of listening levels/dynamic ranges rather than over a very limited range or sweetspot.

This works if we assume that the panels bass roll-off remains consistent at different volume levels (like cone speakers generally do)....if the panel roll-off is also level dependent then I can't see a way to ever achieve a proper match.

Mr T....this may be what you are looking for Emperor (Check under products for Emperor loudspeaker)

Impractical perhaps but since when has esoteric Hi-Fi been practical.

20 electrostatic "woofer" panels should get you 110 db SPL down to 20 Hz!

Lightminer,

I would suggest that Shefield Drum track will highlight most of the reasons panels and subwoofers don't mix. Drums are some of the hardest sounds to reproduce convincingly, although other percussion instruments (like the piano) will work well too...Dave Grusin is a good choice.

My guess is you need a critically damped subwoofer which generally means a very large motor magnet structure within a sealed box and not the usual boomy kind (known for total movie noise capability). This means the woofer goes directly to the rest position when the signal drops to zero without any overshoot or additional resonant oscillations. Remember the panel will have good transient capabilities in the sense that it has very little stored energy...

Firstly, I like Marty I don't understand the preoccupation with flat to 20 Hz - most rooms have 10 db SPL peaks and troughs in the bass and furthermore room boost always causes a rising output in SPL as you go lower with frequency.

Secondly, the reason for a fast bass repsonse (low group delay - no extra added cycles) is to avoid masking the transparent panel midrange with delayed or smeared bass response. A port is adding a signal delayed by 1 cycle and at 20 Hz this is 50 msecs...a lot of midrange music can occcur over 50 msecs, as that is equivalent to 50 cycles of 1000 Hz - and a loud bass sound can reduce your ability to hear the midrange details (masking)

My conclusion is that careful set-up (probably including EQ) likely
trumps specific sub performance. IOW, I suspect that the specs we use are
measuring stuff I can't hear (or, at least, hear very well). YMMV.

You have a good point. Room modes and slow RT60 decay times of more than 1 second will also have a huge influence on the bass response. In a sense, room modal reverberation is a form of repeated/delayed bass cycles that can actually last longer than anything the subwoofer does due to a port or high group dalay.

The only thing I would add is that it is all cumulative...add a slow subwoofer with large group delay into a modest highly modal reverberant space and the bass will start to dominate and sound boomy and disconnected from the panel's beautiful light midrange. So if you have a large space that has a great RT60 with very fast decay times in the bass then you might not care too much about the subwoofer group delay.

BTW Large classical concert halls sound best with RT60's up around 1.4sec. Loud rock and big band in a normal sized studio monitoring room sound better with RT60's around 0.4sec. So the room as well as the genre play a big role too.

Marty,

Indeed, it is fair to say that the importance of low group delay increases
significantly as you go above 40 Hz. However low distortion remains
important right down to 20Hz because an 80 Hz harmonic of a 20 Hz signal is
likely to be quite loud to your hearing even if it is of the order of a mere 1%.
(This is because hearing sensitivity increases dramatically from 20 to 80 Hz.)

So if you have high group delay and a sub which puts out say 100% THD at 20
Hz then you might be rather concerned about what this is doing to the
unwanted distortion harmonics from non-linearities in the design.

Only a horn has the transient speed and "air" to keep up with a panel????
Any responses?

A horn subwoofer would need a huge chamber. If it were folded and made of concrete (so the walls did not introduce distortion) then it might work but we are talking dimensions of 30 feet or so. If you are thinking ported or TL design then the transient response will not be as good as a sealed box.

Soundlabs are reviewed as having very good realistic bass, so a sub should not be necessary.
However before I got the Soundlabs I was going to try out a Klipschorn bass unit that I managed to get hold of - my theory is that it would make the ideal sub

I agree with Johnk - stay away from bass bins - far away.

Gordon Holt used Soundlabs (very fast) for many years before switching to ATC speakers (fast with panel-like mids and more dynamics). An 0.1/15 ATC sub will probably integrate with panels as good as if not better than most anything else - only problem is they are $7K which is like twice what a good JL subwoofer costs. If budget constrains you then check out a JL F112 first and see how that sounds (it is great value for a tight/fast sub).

On another point - how would you stop the bass from a poweful sub (like a JL or ATC) from interfering with the panels - surely the giant panel surfaces will be influenced by the air vibrations in the room. What I mean is this - when I play music loud then I can feel all the surfaces vibrating as they respond to airborne LF vibrations. Obviously a woofer with a huge magnet will be tightly controlled and remain unaffected - this is unlikley to be th case for a huge surface area of a panel in a relatively weak force field.