subwoofers and panels don't mix

Ah, the term is "Group Delay". I am trying to find Group Delay numbers for some of the subs. It would be great if we could get:

Electrostatic panel itself Group Delay at say 300 Hz as refernce.

Group Delay from Sanders Systems integrated sub
Group Delay from Summit X Martin Logan integrated sub
Group Delay from Martin Logan Depth Sub
Group Delay from Hsu Quad Drive ULS-15
Group Delay from Stentor III REL
Group Delay from Stentor Studio III REL

Oh - and these things should be flat to 20, if I find out they roll off at 24, 22 or even 21 then I'm crossing them off, what is the point of all of spending that much money? Mine is pretty flat to 16.

Oh - and we have to put some sort of price limit on it, wasn't there a Krell Sub that used 30 amps circuits or something?

There is a guy 'CraigSub' on other forums and he is sub-crazy (in a good way!). Maybe I can get him to figure this out :).

I may sound like a broken record here: Room analysis, PEq, felexible x-over. I've used a Velodyne SMS-1 sub controller to seamlessly integrate a pair of Velodyne SPLR 800 subs with Maggie SMGs. It took a lot of time and a lot of tweaking, but I can't hear the crossover at all. Let me emphasize, I've always loved the IDEA of hybrid speakers, but, to my ear, even the best (IMHO - Eminent Tech) have had issues with the planar/dynamic x-over.

Using the SMS room analyzer, you can easily see how dipoles differ from forward firing speakers throughout the bass. The nature of the response irregularities in panels makes integration a real challenge - but it can be done.

IMHO, the key to good sub/speaker is smooth on-axis FR around the x-over point, so I follow the following procedure:

1) Use the room analyzer to find a smoothish chunk of bass and start with a frequency in the center of this area as your x-over point. Be sure that this "smooth area" is reasonably balanced w/the rest of the spectrum. A smooth plateau at + 15db doesn't work very well. You may have to move the sub(s) around the room a bit, 'til you find a good result.

2) Flip polarity (this will usually kill the primary suckout quite effectively) to see whether + or - works better.

3) EQ around the x-over point for further smoothing.

4) EQ below the x-over for best balance of smooth vs extended deep bass response.

IME, this procedure will get excellent results from subwoofers with a dipole, unidirectional, or omni speakers (I've tried all three).

Good Luck

Marty

BTW - I really doubt that your choice of subwoofer model is critical - looking "fast vs. slow" isn't likely to help. IME, integration trumps sub performance. I chose the Velos because of size. There are several other models at/near their price that return far better specs (group delay for speed and distortion for clean output) and will very likely outperform them. Yet, I still get great results despite the mediocre subs I use.

Lightminer,

Are you using your system for HT as well as music? Are you a pipe organ guy? If not, why worry about ultimate LF below 25hz. In my collection of >5,000 records and cds, I can only think of a few that go below 30hz. I only mention this because there are tradeoffs in choosing subs and the first one I'll give away is extension.

BTW, I can't imagine that you'll miss the difference in bass performance between EQ'd subs w/ your 3.6s and full range 3.6s. Both will "go there", but they'll sound quite different in terms of "impact". I personally have little issue with timbre (my subs are actively crossed at 74hz). I assume that this is because timbre becomes less meaningful as you descend in frequency. At 25hz, you feel it more than you hear it. I may be less sensitive to timbre issues higher in hz near the x-over than some other folks, but I don't hear the timbre change im my set up; even in the lower registers of electric bass or piano where fundamentals may fall in this critical area. However, this is a classic YMMV.

AVTalk.com and Hometheatershack.com are the two subwoofer distortion & group delay databases I know of (Thanks Shadorne and Bob Reynolds). None of the data you seek is on either site, but there are several REL model test results vailable. General rule for REL = great group delay #s, ugly distortion #s. SVS subs seem to offer a nearly unmatched balance of distortion & group delay performance (if you value both equally), and they do so at a comparatively low price.

Marty

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)

Shadorne,

I understand your point entirely. Now mine:

I recently heard the JL 113 Fathom (low group delay) set up with the
Maggie 1.X (don't recall the current designation) at a local dealer. After an
hour, I had the following observations:

1) The bass sounded no tighter, quicker, or less smeared than my (high
group delay) SPLRs.

2) Mid-bass and mid-range didn't sound more articulate.

3) Discontinuity between planars and subs was evident to me (I attribute this
to careless set-up).

4) The system was more dynamic sounding than mine.

5) This was a different room/different source & amplification/ different set-
up regimen than I use at home, therefore an imperfect test.

However, I concluded that the lower group delay wasn't OBVIOUSLY audible
to me in this set-up, as I expected it might be. Neither was the improved
distortion performance (The JLs produce far better distortion specs than my
SPLRs). 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.

Marty

BTW, once I figure out which subs make the most sense (I wish I had data on
more models) , I'll probably replace the SPLRs (if only on principle alone). I
want lower GD in my system, even if the effect isn't dramatic. Same for lower
distortion. To be clear, I'm not saying better subs don't sound better. I'm just
saying that IME better set-up (including EQ if that -as is likely- proves
necessary) is more obviously beneficial to my ear.

Further, for the OP, I suspect that great subs won't fix his problem. Good
subs, properly set up, just might.

Finally, thanks again to you, Bob and Drew for pointing the way toward betetr
bass performance in my system. Your advice has been invaluable.