Originally Posted by ainsworth
In trying to compare different subwoofers and looking at their frequency response specs, what number should be used as a guideline for the lower value? For instance, some subs state that the frequency response is 20-120hz, well the AVR will cutoff the hz above 80-90 so anything above that for me doesn't factor in. Problem is how low is low enough, and even if it gets to say....20-25hz, is it not also important to know/see the frequency response curve to check what frequency the roll off starts at? Do I need to worry about this at all?
Don't think that frequency response is the sole measure of a speaker or subwoofer. Dynamic range is at least as important.
A sub that works well down to 40 Hz is good for most music as there are only a few instruments that reach lower.
A sub that works well down to 30 Hz is good for almost all music as there are only a very few instruments that reach lower.
A sub that works well down to 20 Hz is good for all music it is the very rare instrument that reaches lower, but further bass extension can matter for sound effects and the like.
A sub that works well down to 10 Hz is a truely amazing thing but its favorable qualities are not always all that obvious.
But response down to XX Hz means nothing unless the response is clean, and this is what separates the boy subwoofers from the men's subwoofers.
IOW, you can have a $200 subwoofer and a $2,000 subwoofer that are both "Flat down to 20 Hz", but they are very different things to listen to. The differences are actually pretty extreme. I can pretty well guarantee that the best $200 woofer that responds down to 20 Hz lacks the ability to generate enough clean at that SPL to be audible during a loud passage in music or a movie.
AFAIK the best data to use to judge subwoofers that is generally available is known as "CEA 2010 Maximum" and a large cache of it can be found here:
The usual criteria for "clean response" among subwoofers are SPL for 10% THD and freedom from compression.
Taking as our exemplary low cost subwoofer the $329 BIC ACOUSTECH: PL-200 we find that 20 Hz it has a clean dB rating from 84 to 87 dB.
Problem is that the threshold of hearing @20 Hz is about 74 dB SPL which basically means that the limit of clean output from the (highly rated) BIC ACOUSTECH: PL-200 is barely audible when playing a pure tone. In the midst of a loud sound effects scene in a movie or an orchestral climax, it isn't going to be noticed all that much.
Taking as our exemplary expensive subwoofer the SVS PB-13 Ultra tuned to optimize 20 Hz operation we find more like 110 dB SPL. This is 25 dB or subjectively maybe 6 times louder. In the midst of a loud sound effects scene in a movie or an orchestral climax, it is probably going to be noticed to say the least.
Another way to look at it is that it would take something like 40 or more PL-200s to produce the same clean output @ 20Hz as one PB-13. In terms of what you actually get in terms of SPL @ 20 Hz, the SVS might be cheap at twice the price! Economies of scale!
Just for grins, I have at least 3 friends who live nearby and have large custom subs that are the equivalent of 4 or more PB 13's.
So, you pays your money and your makes your choice. At least you might have some idea about what to expect.
If the AVR has EQ like YPAO or Audyssey correct for deficiencies?
The main point is that Eq can correct frequency response, but it does zero for dynamic range. Not to diminish the value of eq because it can help with any sub no matter how much dyanamic range it has, by getting the best possible bass extension.
Even within just the realm of frequency response, these peoduct vary quite a bit. Please check on the threads on AVS that are related to the specific product. Audyssey, MCACC and YPAO are families of products and all versions that you may encounter of them are not the same, to say the least!