Stupid speaker test question...please help a n00b

>Why aren't speakers tested by measuring the output sound waves vs the input wave signals?

Because it's less relevant due to how our hearing works than other measurable parameters like intermodulation distortion and stored energy.

The phase distortion (reproduced via electronic all-pass filters so that the effects can be tested without the polar response differences that go with multiple drivers and varying cross-over functions) by cross overs through fourth order at typical frequencies is not detectable in blind comparisons with musical signals (clicks at long intervals can be differentiated).

While first order acoustic cross-overs avoid that they also allow excursion to double at a given input signal level for each octave below the cross-over point until their slope gets steeper. To avoid audible distortion as you reach the speakers' mechanical limits you need a higher cross-over point which means the lower frequency driver is becoming acoustically large with increasing directivity so there's a bigger directivity mismatch switching between drivers. You also have a +3dB peak off-axis someplace which isn't something our brains encounter in nature. I speculate that these reasons are why first order designs don't sound natural.

>Assuming you control all the other parameters of the test of course...

You'd do well to read _Sound Reproduction: Loudspeakers and Rooms_ by Floyd Toole. It does a great job summarizing what we know about hearing and sound reproduction.

>quite in disagreement with you on this. you clearly state you are speculating - have you heard any true 1st-order x-over speakers? $#

I've heard Dunlavies + Thiels and they subjectively don't sound as correct as good designs with higher order cross-overs.

I'm just making a high probability (90%?) educated guess on the reason where it's most likely the polar response problem that makes most consumer two-way speakers sound wrong too (I don't like those either) unless they're built to clock radio dimensions which precludes bass extension and more realistic listening levels.

Timbre perception results from a weighted combination of what our brains identify as the direct sound and its reflections which are the direct result of polar response. Where the response spectra vary too much (we seem to accommodate high frequency roll-off which would be consistent with evolution in natural surroundings that become more diffusive and absorbing with higher frequency) it doesn't sound like it would have live.

Subjectively polar response uniformity predicts speaker preference regardless of a listener's country of origin, preferred musical genre, sex, and other factors. Sean Olive has actually produced a formula using weighted values of amplitude response over a listening window and first reflection angles for a variety of rooms but AFAIK the coefficients remain a Harman Group trade secret.

To avoid running into higher frequency drivers' mechanical limits first order designs generally use cross-over points where the lower frequency drivers are becoming acoustically large which makes directivity non-monotonic.

Note the peaks and dips in off-axis response as the Dunlavy SC-IV/a transitions from woofer to midrange and midrange to tweeter as the lower frequency driver gets acoustically large:

http://www.stereophile.com/images/archivesart/D4afig06.jpg

http://www.stereophile.com/content/dunlavy-audio-labs-sc-iva-loudspeaker-measurements-part-2

(The vertical polar response should be interesting too with all the driver overlap but Stereophile doesn't measure far enough off-axis to capture what you're hearing from floor and ceiling bounce).

which is not natural and not preferred (although you might object less to the polar response problems than the stored energy issues that go with metal drivers which are avoided in first order designs).

Note speakers I like or don't object to just don't do that

http://www.linkwitzlab.com/Pluto/resp1.gif

http://www.stereophile.com/images/archivesart/N33fig4.jpg

http://www.stereophile.com/content/nht-33-loudspeaker-measurements

There are lots of others that should have similar polar response which I haven't verified.

Wave guides mated to large mid-bass drivers, dynamic driver dipoles that limit dispersion through acoustic cancellation, and wide dispersion designs with acoustically small baffles all work well.

>Merely having a 1st-order x-over ckt does not make a speaker 1st order, just FYI.

Right. Drivers have a pair of high-pass poles and the voice coil inductance creates a low-pass filter so first order electrical can yield up to third order acoustic.

>02-23-12: Unsound
>I'd be leery of putting too much stock in Sterophiles testing of first order speakers. Unlike many other speakers manufactures, first order speaker manufacturers usually suggest testing speakers at the preferred listening positions, not 1 or 2 meters, something that seems to have been challenging for Stereophile.

While I wouldn't read anything into small peaks and dips resulting from being more off-axis to one of the drivers, the narrowing and broadening horizontal dispersion are endemic to the design and captured accurately enough to show why first order acoustic cross-overs are not the best idea.