Don't let the bench testers fool you, The broader the range the better. Even though human ears arn't supposed to hear beyond like 17Khz. Our hears can still tell something is going on in those upper freqs.
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Phil..I don't disagree with you at all. '...broader is better...' I just don't understand the value of specifying bandwidth in an unqualified manner - i.e. bandwidth versus frequency response. How do you measure bandwidth? On axis at 1 meter and what is the response in db?
My premise is that the manufacturer is playing specsmanship and these speakers if spec'd +/- 1db or even +/- 3db would look something like 25Hz - 20kHz or even worse.
Rap good point. So the labs claims their speaker goes down to 19 or 25hz...lets see how she performs the more critical 25hz-35hz...and then how she performs in the mid/bass?? When i see a lab's claim of 20hz, ok, but what's the overall sound in the critical 25hz-35hz and then upto the midbass??? The one woofer that i'm confident that delivers a smooth overall response is the new Seas W26. And she goes to 20hz!! But seems Europe is getting first batch of the beautes. Same for tweet, i'm not that interested that the driver goes to 25Khz(almost all do), how's the critical transition point to the woofer/midrange?
The measurements are pretty useless.
Keep in mind +/- 3db can mean up 3 db at 100 HZ and down 3 db at 150 Hz resulting in an overall change of 6 db in 50 Hz but it's still within published specs. You will hear this in the midrange.
As a general rule drop outs in frequency are more easily forgiven by the human than peaks or hills in frequency response.
Also most published curves are weighted and are averaged across a sample of speakers. What your speaker measures, who knows unless the manufacture ships a plot with the speaker. Point is - listen! The numbers are only good for general comparison.
Not having a flat response to 20 Hz is not always a bad thing. Most rooms have modes to deal with and depending on the location of the speakers the room will boost low frequency. If the speakers have a nice roll off in the bass you may gain some back by room placement - this is called room response and some manufactures now publish these ranges too.
In general bandwidth is defined by FWHM (Full Width at Half maximum) at a given amplitude (gain) or SPL level, which is 3db down for power as in SPL and 6db down for voltage/current. This is regardless of any amplitude variation within pass band.
As for what the published speaker specs mean, who knows? When I see a frequency spec with +/-Xdb, I take that as the max/min amplitude variation from the rated sensitivity across the stated bandwidth. That doesn't mean you're going to get 10exp(-X/10) less the power from the rated sensitivity at the two frequency extremes.