Subs & Group Delay

Shadorne,

Your point is taken regarding sensitivy vs. frequency - do you miss your "loudness" control?

However, when I run test sweeps on the SMS-1, the lowest audible tones generate a VERY loud rumble at 90db and up. Whatever frequencies we're talking about here (it appears to be app 25hz from the readout), it should be low enough to fall into the "insensitive" range of perception. This doesn't seem consistent with "rustling leaves" and I wonder what the explanation is. I'd also note that A0 on a piano (typically 27.5hz) registers as LOUD! well below the levels implied by your math (the room is not shaking). Any thoughts as to what I'm missing here?

Beyond this, my intended point re:crushing spl is that (it would intuitively seem that) the 100db anechoic test output should register much higher than 100db in a typical listening room. Obviously, there's lots of things going on that affect the change in output at low frequencies between anechoic and real world environments, 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)?

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. Obviously, there are too many variables for a precise answer, but, as a practical matter, there should be a reasonable answer (or range of answers) to that question. Just wondering which sweep you might look to in evaluating a sub.

Thanks in advance.

Marty

I'd also note that A0 on a piano (typically 27.5hz)
registers as LOUD!

You will hear the 2nd and higher harmonics of the piano loudly.

Now for the weird part.... you can completely remove the fundamental and play
just the harmonics and your ears will hear the correct note (but timbre will be
off)....hearing is a weird science!!!!

If you notice above I mentioned a pure 20 Hz tone or test tone (not a note from
an instrument as any instrument will have higher harmonics too)

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