Subs & Group Delay

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

Bob,

The general idea is that low frequencies are much less audible compared to midrange frequencies...with the biggest loss as you go down from 60 to 20 Hz. I may have exaggerated it some but it certainly "significant" whichever way you look at it.

The implication is that harmonic distortion in the 3rd and higher harmonic of a 20 Hz note may be detrimental - even in tiny amounts - making the sound louder than intended on the recording. See what Seigfried Linkwitz has to say - scroll to the bottom of the page.

This is a review of an important AES paper on subwoofers that appeared in Stereophile - The Science of Subwoofing.

Subwoofer

distortion guidelines are offered: Harmonic distortion will not be audible if the second harmonic is below 3%, the third around 1%, and higher harmonics no greater than 0.1–0.3%.

and

The authors sadly report that it is evidently believed in the loudspeaker industry that woofer distortion is not particularly important; as a result, there are very few drivers built that possess adequate linearity. All of this bodes ill for our chances of finding the ideal subwoofer from a commercial vendor.

For details see: Louis D. Fielder & Eric M. Benjamin, "Subwoofer performance for accurate reproduction of music", JAES, Vol. 36, Number 6, pp. 443 (1988).

Most of us are listening to distortion on our subwoofers...