Subs & Group Delay

but my assumption is that the same signal in a 15' x
20' room should be perceived as much louder than in the (quasi) anechoic
measurement environment used by HTshack. Do you believe that this is a
good assumption (at least below the primary cancellation frequency)?

Absolutely - you will get at least a 3 to 6 db boost and more or less at room
mode peaks/troughs.

Finally, do you have a sense as to which test sweep
(they go in 5db increments from 90db to 115db) in those subwoofer tests
might be the best proxy for LOUD listening - (music) in a real room.

I can't say but I think you need roughly 110 db SPL in the parking lot at 30 Hz
to convincingly represent peaks from real live instruments (like a drum set) in
a large sized room. This will have you covered for rock and dance club tracks
but classical can be handled with 10 to 15 db less. You can probably get away
with 100 db SPL or less at 20 Hz - as I think I mentioned I'd rather not have
20Hz at all if it was at all distorted.

One or two JL F113's would have it covered for most people in a large room
(if you ask around I think you will find several people own two of
these monsters and are very happy)

Hi Shadorne, I dont know where to go with my reply to your post above (six above). But I must say it has me "confused". Where you wrote,

"It is pretty impressive yes but a far cry from a crushing SPL due to the fact we can barely hear 20 Hz. For comparison it would sound as loud as a 40 db SPL note at 1 Khz...a little above the rustling of leaves. The good news is that if your sub can achieve 115 db SPL then it suddenly becomes much more audible - as 120 db SPL will sound like 80 db SPL at 1 Khz - so clearly audible even above a conversation. Also there is not much at 20 Hz anyway so the biggest benefit is the lack of distortion at higher harmonics rather than any bone crushing sound.

The reality is that a great sub will NOT sound devastating on a 20 Hz pure tone at 100db SPL - is will be mostly inaudible if it is a good high quality sub!!!"

I am actually having a hard time digesting this. If you would like to try re-explaining this to me I would be obliged. I am not sure how I want to counter to those statements. Perhaps we can dissect it at some point and discuss it that way. Not trying to be argumenative, but I do belive you need to perhaps rethink this.

Or perhaps I DO!

Bob

Shadorne,

Thanks again.

Your final suggestion goes to the heart of my questions:

1) I'm pretty confident that a pair of 113s will do it right (and look good doing so), but distortion specs are significantly better on the SVS ultra 13 (even with the ports sealed to minimize group delay). Will I hear this?

2) The SVS ofers an appealling 20ms Group Delay, but the JL stays below 10ms (for the most part). Will I hear this?

3) Will I hear improvement IN MY ROOM at MY LISTENING LEVEL with either choice versus my dual SPLR 800s which, honestly, don't seem remotely stressed when listening now.

4)If I spend $2500 for the pair of SVS subs, will I feel less silly than if I spend 3X that on pair of 113s only to find that the answer to #3, above, is "NO!".

5) If I can hear a difference, and the difference is distorion rather than group delay will I still feel silly because the cheaper SVS will get you virtually all of the distortion benefits and most of the group delay benefits at half the cost of the SVS Ultras?

You've been tremendously helpful, but I suspect I'm at the point where tossing it around further becomes pointless. I'll make my decision and report back.

Marty

I am actually having a hard time digesting this. If you
would like to try re-explaining this to me I would be obliged. I am not sure
how I want to counter to those statements.

My comments are entirely based on equal loudness contours. A deep bass
pure tone at 20 Hz (with no harmonics) is quite soft sounding at 100 db SPL
(in fact you may hear rattling of windows etc. louder than the pure tone - i.e.
you are more sensitive to harmonics or vibration induced by the 20 Hz tone).
Basically we hear 1 KHz tones with some 60 db better hearing sensitivity. As
you get louder and close to 130 db SPL at 20 Hz then the equal loudness
curves flatten significantly and that pure tone would sound as loud as 100 db
spl at 1Khz ( a mere 30 db drop in sensitivity as our hearing response
"flattens" as you go louder) As you can see from those curves - even a
tiny bit of harmonic distortion (say 5%) from your sub on a 20 Hz pure tone is likely to be more audible than the test tone itself - just because of our poor hearing sensitivity at 20Hz.

Hi Shadorne, Now I am with you! But I think the numbers and their implications are a bit exaggerated.

It looks to me you are using the Robinson Dadson cure as opposed to the Fletcher Munson. I see that at 80db the R-D curve is up 30db (not 40db) at 20hz while the F-M curve is only up 10db at 20hz. But even so with the R-D curve at 40db you are then looking at 50db up at 20hz, still not even close to the 60db that you mentioned to sound like rustling leaves.

I do think, now here we go, that the R-D curve is not as useful as the F-M curve. I believe the F-M curve to be the more accurate curve for our purposes. And yes thats good for me as now I do only have to be 10db up at 20hz as opposed to the 30db as suggested by R-D. Wow thats a big difference (20db). That is four times the difference between the two and the implications of power requiremens are huge. I will go with the F-M just because it is at least possibly obtainable by most audiophiles. And no I am not wimping out:)

Bob