Sloped baffle

Hi Roy,

Thanks for the discussion, but though the difference between the woof and mid remain constant, there is a difference, yes? And that means that the wave launch of a transient will not be the same for the 2 drivers, correct? The are not time aligned, it would seem. Even if the sum of the outputs through the crossover point remains correct, are we not stuck with the constant time differential between the 2 drivers?

Could you tell me what I am missing?

07-17-14: Sounds_real_audio
Wouldn't it be easier just to tilt the speaker slightly backwards?

tilting the speaker backwards attempts to merely align the acoustical centers of the drivers such that the sound from all the drivers reaches your ears at the same time.
But what about the damage done by the higher-order x-over to the phase & time coherency of the music signal? This damage is the phase distortion that Roy is talking about all along. That cannot be corrected by merely tilting the speaker backwards.

I just want to listen to good music

'good' is a relative term - your music selection is best for your taste in music. Others might not find it 'good' at all...
OR, did you mean 'good' as in well reproduced playback sonics??

Thanks Roy for the detailed explanation. :-) Was very helpful, as always.
OK, I wont put as much emphasis on the T/S parameters any more. I thought that I could read them & determine something about the quality of the driver. Not so, it seems....

Sounds Real-
You are indeed right about 'just tilting back the front face'. That can be enough to line up the acoustic centers of woofer/mid and tweeter, so that the drivers are possibly in their best positions to combine properly at your ears, no matter what crossover design is used. The high-order crossover circuits then put more and more time delay on the signal the lower and lower down the scale we go. That cannot be fixed.

And then to make the first order crossover work correctly, one must choose the correct drivers to begin with. I hope this clarifies a bit more for you.

Omsed-
You ask "though the difference between the woof and mid remain constant, there is a difference, yes? And that means that the wave launch of a transient will not be the same for the 2 drivers, correct? The are not time aligned, it would seem. Even if the sum of the outputs through the crossover point remains correct, are we not stuck with the constant time differential between the 2 drivers?

Could you tell me what I am missing? "

Yes, I agree. Again, with the right drivers, Zobels, and first-order crossover design, there will always be a time difference created by that constant 90-degree differential, a constant difference 'in degrees only' at every frequency we examine.

90 degrees is one-fourth of any sinewave's period. At a 3kHz crossover point, that wave's period is 1/3000 of a second. One fourth is 1/12000 of a second. This is the time-difference between the mid and tweeter at this frequency. If we choose 1000 Hz instead, the time difference would be three times longer, 1/4000 of a second.

I can only tell you that the math of "two waves of the same tone traveling out of phase with each other by 90 degrees" will measure and sound like one wave having no time delays. Perhaps you must do the math yourself to see this-- I certainly understand that feeling! Again, the key words to look up are "operating in quadrature".

Bombaywalla-
I apologize if I gave the wrong impression. T/S parameters are quite important, as they tell us a great deal about how the driver will perform in any box.

They just do not give the exact box size, which was the hope. The error can be 10 to 20% off of the correct box volume.

A real test box's performance is determined by listening and then measuring its impedance curve and resonant frequency, to find out the Qts and Fs. That tells us how close we came to meeting the T/S ideals with that test box. Then build another...

Best,
Roy

Hi Roy, thank you for your response.
At the risk of appearing argumentative; here on Audiogon another speaker designer has suggested that placing multiple woofers in a room at different distances could be beneficial towards evening out standing waves, if that were the case; wouldn't W M T M W speaker arrays have some advantages? I'm not aware of any speakers that are touted be time coherent having more than one tweeter per channel, are there any?
As for sound bouncing differently above and below ones head, wouldn't that be typical during live musical performances? Wouldn't the wave size from midranges and woofers (and live performers) be large enough to extend above and below a typically seated listener's head?
Thiel's concentric drivers appear to be flat, so reflections should be minimized, no?
I have no direct experience, but I seem to recall that DEQX suggests that speaker correction should be first done close to the speakers and then followed with room correction at the listening positions.
Another question if I may; could horn loaded speakers be time coherent?
Thanks again!