Stupid speaker test question...please help a n00b

>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.

I'd suggest listening to speakers at the appropriate listening position. Caveat, first order speakers might not be the best choice for dancers. 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.

Johnnyb53 wrote:

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.

I might have said "different" rather than "unnatural" to describe the in-room performance, but his point should be taken. An anechoic chamber is (for measurement purposes) infinitely large - with no contributions to the measured performance from reflected sounds. To achieve this in your listening room (for instance, to eliminate quarter wave reflections), the speakers would need to be +/- 5 meters from the nearest wall (including the floor, to be a purist). I thinks Johnny's generalization is pretty safe: few rooms will allow such speaker positioning.

Marty

PS The contribution of reflected energy is usually VERY audible. Audyssey is - broadly speaking - a system that attempts to adjust your system's in-room response to something more akin to anechoic response. A simple "before" and "after" test with Audyssey will quickly demonstrate just how far from "anechoic-ish" response you will get in your listening room.

PPS I'm pretty confident that anechoic testing arose to "level the playing field" for comparing speaker test results. Unfortunately, the level field is IMHO also the wrong field. If you want to determine which is the better of two football teams, by all means schedule a head to head game. Just don't play it on a basketball court.

Marty

Where should they play, in a water polo pool? Without anechoic measurements we wouldn't have a baseline. Without a baseline it would all become a crap shoot. With reasonable speaker/ placement we can differentiate between direct and reflected sound surprisingly well. Appropriate room treatment can go a long way towards attaining a fairly neutral environment. As you have pointed out, digital room correction is starting to further help in that regard too.