A quick, dumb question on time-alignment

Cloth Ears · 1st September 2006, 02:13 AM

If you have a front-loaded horn mid, and a ribbon tweeter or a high-efficiency mid-bass - how do you locate the horn to time align? Do you still line up the voice-coils, or do you treat align the horn mouth with the other drivers and delay the mid-bass at crossover?

Told you it was a dumb question

I've got some dome mids that I can build some 7cm horns for (13cm dia) - and, as usual, I was just wondering...

I couldn't find any relevant post, so if there is one, just point please.

misterears · 1st September 2006, 06:55 PM

In general, the effective source location on most all transducers is at the voice coil or at the bobbin to cone adhesive joint. So, the entire horn would need to overhang in front of a direct radiating driver at crossover.

This all presumes that the units are minimum phase devices and also assumes you'll be addressing the the acoustic output of the devices and not expect an idealized theoretical crossover will give the expected results (meaning you'll include the response roll offs of the transducer when designing the crossover ...which is usually a significant effect with horns near and below their LF cutoff).

Salas · 1st September 2006, 07:23 PM

By experiment i.e. measuring summation and simulating it, we can draw conclusions of propagation centres from phase tracking. It shifts a little for different frequencies. In the critical midrange around 3kHz I have seen cones having their origin of sound at about 3/5 their cone depth and tweeters & compression drivers with horns at about the join of dome with coil point.

myhrrhleine · 5th September 2006, 09:08 PM

Measurement works best.
It can also be done 'by ear' if you have the know-how, but it's rather imprecise.

Cloth Ears · 25th September 2006, 07:17 AM

Nee How! Sorry for the late response, been in Shanghai.

Thank you for the replies... damn! I knew I would have to do some work instead of there being an easy answer.

1st September 2006, 02:13 AM	#1
Cloth Ears diyAudio Member Join Date: Dec 2001 Location: Melbourne, Australia	A quick, dumb question on time-alignment If you have a front-loaded horn mid, and a ribbon tweeter or a high-efficiency mid-bass - how do you locate the horn to time align? Do you still line up the voice-coils, or do you treat align the horn mouth with the other drivers and delay the mid-bass at crossover? Told you it was a dumb question I've got some dome mids that I can build some 7cm horns for (13cm dia) - and, as usual, I was just wondering... I couldn't find any relevant post, so if there is one, just point please. __________________ Jont. "It is impossible to build a fool proof system; because fools are so ingenious."

25th September 2006, 07:17 AM	#5
Cloth Ears diyAudio Member Join Date: Dec 2001 Location: Melbourne, Australia	Nee How! Sorry for the late response, been in Shanghai. Thank you for the replies... damn! I knew I would have to do some work instead of there being an easy answer. __________________ Jont. "It is impossible to build a fool proof system; because fools are so ingenious."

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1st September 2006, 06:55 PM	#2
misterears diyAudio Member Join Date: Jul 2006	In general, the effective source location on most all transducers is at the voice coil or at the bobbin to cone adhesive joint. So, the entire horn would need to overhang in front of a direct radiating driver at crossover. This all presumes that the units are minimum phase devices and also assumes you'll be addressing the the acoustic output of the devices and not expect an idealized theoretical crossover will give the expected results (meaning you'll include the response roll offs of the transducer when designing the crossover ...which is usually a significant effect with horns near and below their LF cutoff).

1st September 2006, 07:23 PM	#3
Salas diyAudio Chief Moderator Join Date: Oct 2002 Location: Athens-Greece	By experiment i.e. measuring summation and simulating it, we can draw conclusions of propagation centres from phase tracking. It shifts a little for different frequencies. In the critical midrange around 3kHz I have seen cones having their origin of sound at about 3/5 their cone depth and tweeters & compression drivers with horns at about the join of dome with coil point.

5th September 2006, 09:08 PM	#4
myhrrhleine diyAudio Member Join Date: Jan 2006 Location: Avalon Island	Measurement works best. It can also be done 'by ear' if you have the know-how, but it's rather imprecise.

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