Originally Posted by rdclark
Originally Posted by DonH50
Hmmm... Look up Fletcher-Munson (or Robinson & Dadson) loudness curves. Bass frequencies don't take any more power than any other frequencies at the same SPL
I thought the A-weighting on the SPL meter was assumed in these discussions. As I believe they should be, since we're speaking exclusively of audio and human hearing. With A-weighting -- the default on every SPL meter I've ever used -- it does in fact take considerably more power to produce the same SPL at low frequencies.
But whether you split the hair or I do, we seem to agree that powered subs are a benefit in pretty much any system, and their ability to extend the power capabilities of the main system amplifiers is one reason why.
I never assume weighting in any discussion of frequency response. Personal preference. I do not use an SPL meter often and when I do I almost always use flat or C weighting (usually C since flat meters are expensive, and I have an expensive Earthworks measurement mic with preamp and SW to do frequency and time domain analysis much faster and more accurately than most consumer SPL meters). Whenever I did a professional installation the reference was established using a flat meter or sometimes C-weighted. A weighting is meant to follow human hearing and so the meter's response rolls off at the high and low ends. I would avoid or compensate weighting when assessing the frequency response of a system. But I see where you are coming from now, more power is needed at LF due to the meter's A weighting, which requires more power at LF to read "0" compared to a flat response. However, that is because the meter's weighting has changed the level the meter reads at those frequencies. The absolute SPL is rising at LF (and HF, but less dramatically, depending upon age) to provide the same perceived loudness, but the meter rolls off the higher SPL. The idea behind A weighting is to provide a meter that reads "0" across frequency when the perceived sound (not actual SPL) is the same to us. I always reference SPL to absolute values, not weighted values. I suppose we could use phons or some other unit instead, but SPL to me is relative to unweighted pressure levels.
The answer is the same, we got there via different paths. I did not understand you were assuming A weighting, I was weaned differently. No worries!
As an aside, one reason I rarely use A weighting is because it is a single curve, whilst in reality our sensitivity to various frequencies also changes with different level (volume, loudness). Manufacturers can also improve their SNR by applying A weighting to the output, bah! A lot of consumer reel-to-reel recorders spec'd A weighting for obvious reasons (better numbers). I've only used weighted readings when required by a customer or per some gov't tests, but again most testing I have performed required flat response that is then compared to an appropriate curve (A, B, C, D, Z, whatever). I think some OSHA tests use A but it's been a while since I did any of this. I always measure and strive for a flat response as measured using a flat meter or mic/measurement system.