Stupid speaker test question...please help a n00b

I'm not so sure about squarewave testing being meaningful. It will reward first order (analog) x-over designs, but the audible benefits are debateable. I won't take sides in that debate, but Siegfried Linkwitz has written extensively on the subject, and he comes down squarely (pardon the pun) on the side of higher order designs that won't fare as well on squarewave tests.

Linkwitz certainly qualifies as an authority, since the Linkwitz-Riley crossover solution (even order only for "true" L-R, odd order "quasi" L-R is possible for 3rd order and above) is pretty widely considered a classic bit of design theory. Obviously, there are great designers (Dunleavy, Vandersteen, et al) out there using first order crossovers so.....

While L-R is NOT universally accepted as an optimal solution, Linkwitz's analysis does cast some doubt on the real world benefits of goood performance on a squarewave test.

Marty

PS For those pointing out that THD tests, etc. are of limited utility in judging a speaker's performance, I'd say that this is one more example where test results for speakers may raise more questions than they answer.

See, I'm convinced I'm an audio neanderthal. I've been into this hobby for over 30 yrs and have NEVER checked a single spec or chart! Always skipped right over any and all tech info in reviews. Did it all by ear baby! Must be why I've got a tube-based system!!;)

lol thanks guys. i have to say i can't think of another field that is operates in this much of a grey area regarding performance. imagine if cars, computers, machines, or any other engineering devices operated like this. Quite frankly, I don't like this side of hi-fi.

02-21-12: Spartanmorning
lol thanks guys. i have to say i can't think of another field that is operates in this much of a grey area regarding performance. imagine if cars, computers, machines, or any other engineering devices operated like this. Quite frankly, I don't like this side of hi-fi.

Spartanmorning, you do not need to get so frustrated or disillusioned with this hobby (errrr.....obsession) of hi-end audio. You are new to this field so you do not know the various ins & outs but the it's not hard - just requires some common sense & extensive listening with your ears. Whenever you get an opportunity to listen - audio gear in a friend's house, audio gear a A/V show, audio gear at a dealer, live concert performances - take the opportunity & GO!

Look you cannot specify a speaker's performance by it's output sound waves & there are several reasons:
* the output of a speaker is very dependent on the quality of audio gear driving it. So, which brand or brands of audio gear should be considered the "gold" standard in driving a speaker? Who decides this "gold" standard? Is the decision unbiased or is there collusion in the decision? Who decides what the deciding factors should be to settle upon the gold standard to drive loudspeakers?
* output of a loudspeaker is dependent impedance matching of the amplifier & speaker & cable. Who decides which exact components to select? And, worse, the amplifier-cable-speaker match varies with every speaker! So, if you get such a spec (i.e. measurement of the output sound waves) from one manuf can you make an apples-apples comparison with a similar spec from another speaker manuf? NO! 'cuz 99.999% the 2nd speaker manuf used very diff. audio gear to drive his loudspeaker (to get favourable results).
* What should be the amplitude of the signal driving the loudspeaker? As many have stated distortion is a very heavy function of amplitude (& frequency).
* We have the audio spectrum of 20Hz-20KHz: at which frequencies should the output sound waves be measured? Who/which body decides that? Why is this body entrusted to make this decision?
* What should be the driving signal into the loudspeaker? Should it be a sine wave? Should be it be a square wave? Should it be music? If music, what kind of music? If you say Beethoven, I'll say Mozart! You are not wrong & neither am I! So, now what?

imagine if cars, computers, machines, or any other engineering devices operated like this.

Now, let's look at this part of your statement - computers, cars, machines, engineering devices ALL give you stardardized specifications that hold true across planet Earth whether you are in Tibet or in Washington D.C. or anywhere in between. If you have standard measurement equipment (which can be bought from standard measurement equipment manuf) anybody with the skill in that area can verify the performance. The test conditions require that the device be put into a known state and this can be done by the experts at, say, Consumer Reports, and then the test can be run. When you get the results you can compare apples-to-apples.

Loudspeaker manuf in some sense give you the same -
* they tell you speaker efficiency in dB/W/m or dB/2.83V/m(which lets you estimate amplifier power requirements)
* impedance & phase plots (which again give you an estimation of how easy/hard the speaker is to drive)
* max SPL level (which lets you estimate if it reaches your listening levels + if it'll work in your room)
* some manuf like Green Mtn Audio even give you distortion specs (which give you an idea of how loud you can play the speaker)
* Cross-over point frequencies (which give you an estimation if you'll hear artifacts in the sensitive presence region)

you have all the info/specs you need to make an informed decision of whether the loudspeaker needs to be put on your short-list or not. Thereafter, you NEED to listen to it & see if you like it. No way around this last part. Short-ciruiting this last part often means short-ciruting your listening pleasure!!

Hope that this helps to make you less disillusioned.....
FWIW.

>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.