subwoofers and panels don't mix

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.

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.

Two more group delay observations:

First is inconsistency in test results:

If you cross check AVTalk and Hometheatershack you will see differences in the test results of the same model subwoofer (these may look smallish at a glace) which prove greater than the delta between differing makes & models. In fact, HTshack tested 2 samples of the SVS 12NSD and got significantly different GD results.

Second is Shadorne's illustration of GD's impact at 20hz:

While the GD test results really diverge at this low frequency, they tend to converge significantly as pitch rises. I wonder if the lack of really low frequency program content tends to obscure the audibility of a sub's GD capability. At least, the program material I used in my listening tests.

Marty

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.