Stupid speaker test question...please help a n00b

02-21-12: Drew_eckhardt
.....I speculate that these reasons are why first order designs don't sound natural.

quite in disagreement with you on this. you clearly state you are speculating - have you heard any true 1st-order x-over speakers? Merely having a 1st-order x-over ckt does not make a speaker 1st order, just FYI.

Basically, if you create a loudspeaker to measure well in an anechoic chamber (the only way you can accurately evaluate its output), it will sound unnatural in a number of ways when placed in a room. Some loudspeakers are designed (e.g., James, Mirage, MBL, Gallo, Ohm) to interact with the room and are the better for it when it comes to natural-sounding listening. But in an anechoic chamber these speakers don't measure so well.

For nearfield monitors, anechoic measurements are valid, but for regular home audio speakers, the *power response* is more important. That is, how linear is the response when it is in a typical listening room, where walls reinforce certain bass frequencies and hard surfaces can make the treble sound unlistenably bright. If you have a narrowed dispersion at the crossover point, this won't be apparent in nearfield listening or anechoic measurement, but will sound thin and hollow at that frequency in a typical room because the narrowed dispersion at that frequency results in less reflection--and therefore less energy--there.

Please define "typical room"?

>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.

02-22-12: Unsound
Please define "typical room"?

Of course there are many listening room configurations, some on a slab, some suspended floor, some with 8' ceilings, some with high or vaulted ceilings, some with enclosed rooms, some with open architecture, etc., etc. One could say, however, that a typical room will be rectangular with painted sheetrock walls, carpeted or with area rugs, with a mix of hard and soft furniture, pictures, wall hangings, and shelves, some holding record and/or cd collections. And the astute buyer will match the speaker's dynamic range, bass extension, and system power to the room size.

One thing is sure--a speaker designed for a uniform power response in the "average room" is going to sound more natural in a wide variety of room configurations than one that is voiced only for nearfield or anechoic use.