Sloped baffle

07-06-14: Sounds_real_audio

I have a question. If an 18kHz sound left its' source and a 30Hz sound wave left its source at the same time. would they both get to the listener at the same time?

No, they would not.
If you have the driver creating the 18KHz signal & the other driver creating the 30Hz signal mounted on a perfectly vertical plane, the acoustical center of the 18KHz driver would be in front of the acoustical center of the 30Hz driver. Due to this, the 18KHz signal would get a head-start & would reach your ear 1st.
You hear this all the time at shows - the music is always "tipped up". You hear way too much high freq & the bass seems to be missing. The speakers are not time-coherent & often the drivers are not time-aligned.
If I remember Roy Johnson's paper, the woofer driver has a 90 degree phase lag in its pass band meaning that it starts to produce the 30Hz signal 1/4 wavelength of the x-over frequency later than the tweeter driver.
That's why you see sloped baffles with the tweeter on top - the furtherest away from the listener's ear. This aligns the acoustical centers of the tweeter, mid & woofer drivers to give them a chance to arrive at your ear at the same time.
hope this helps.....

Bombaywalla, yes, your post is responsive and I get it. I still wonder out loud whether speaker inductance as a function of frequency response in fact remains constant within the speaker's pass band. Indeed ... even if speaker inductance remains constant as a function of frequency, wouldn't that also impact phase coherency?

I gather from your prior posts that the answer is "no" as long as inductance doesn't change. Then there will be no impact on phase coherency. Instead, phase coherency is effected only when there is a change in X-over reactance, albeit whether it is capacitive or inductive.

Al ... if you're catching any of this, please chime in. I think this is an important issue. Put it to you this way, my sense is that even if proponents and opponents of the importance (or not) of phase coherence want to argue yay or nay on the issue, it seems to me that phase shifting can't be good factor ... at best neutral.

BIF

Bombaywalla, sounds_real_audio didn't ask if the were on a sloped front or a flat front, He simply asked, If they leave the source at the same time, would they end up at the listener at the same time...
I believe his real question is "do all frequencies move at the same speed"
I'm sorry if I mis understood the question, but as it was proposed, the answer is Yes.... I'm not try to start an argument, only to head off confusion.
Tim

"I still wonder out loud whether speaker inductance as a function of frequency response in fact remains constant within the speaker's pass band. Indeed ... even if speaker inductance remains constant as a function of frequency, wouldn't that also impact phase coherency?"
Speaker inductance is one of the main factors that we measure to build a impedance/phase correction circuitry. The more that impedance and phase can be controlled, the easier it is on amplifiers (especially tubed).. Tubes can handle inductive loads reasonably well, but crap on themselves trying to drive capacitive loads.
Here is a thread where Al does a good job of explaining it...
http://forum.audiogon.com/cgi-bin/fr.pl?htech&1377551562&read&3&zzlMesch&&

Hi Timlub,
Ok, no problem.

I believe his real question is "do all frequencies move at the same speed"

yes, all freq travel at the same speed. But the answer to his question is still "No, they do not arrive at the listener's ear at the same time". I tried to explain that in my post - looks like you missed it? I'll cut & paste here again for your convenience:
" the acoustical center of the 18KHz driver would be in front of the acoustical center of the 30Hz driver. Due to this, the 18KHz signal would get a head-start & would reach your ear 1st."
if you do nothing to compensate for the fact that the acoustical centers of the 2 drivers are different, the highs arrive earlier.
hope that this clarifies.