time correction and units alignment

[Williams Audio]

hi,
time correction and units alignment;
i am trying to set up a 3 way spk and i have to decide how to place the units .
how do i calculate the distance between the units (3d view) in order to get a time delay correction; i use 3 way elec. xover and 3 way amplification. I know that tweeter has to be place back wards some how, but how much, if I incline the spk box back wards this will do it?
best regards
Williams

[e-side]

You could read this ESP article about time alignment.

[cs]

Hi,

I had a long email discussion with Ashley James, MD of AVI HiFi on this subject. AVI are a very well respected manufacture of amps, cd players and speakers. (www.avihifi.co.uk)

Ashley maintains that there is no need to compensate for acoustic delay between drive units, but it is vital to ensure the electrical signals are in phase.

He said they carried out a test, where the tweeter and bass/mid units were in different enclosures, one on top of the other. They could move the tweeter boxes by +/-1m forward and backwards, before there was any noticable difference !!

[soongsc]

Originally posted by cs
Hi,

I had a long email discussion with Ashley James, MD of AVI HiFi on this subject. AVI are a very well respected manufacture of amps, cd players and speakers. (www.avihifi.co.uk)

Ashley maintains that there is no need to compensate for acoustic delay between drive units, but it is vital to ensure the electrical signals are in phase.

He said they carried out a test, where the tweeter and bass/mid units were in different enclosures, one on top of the other. They could move the tweeter boxes by +/-1m forward and backwards, before there was any noticable difference !!

I would really like to know what drivers and type of XO they used during the test, and the exact components and ratings used. XO frequency is also important.

Measurements in the lab allowed me in identify exactly how much I needed to move a super tweeter to get the response I was looking for. Although initial listening did not show much difference with an XO at 10KHz, if the XO was at a lower point where normal 2-way speakers cross, the difference would be significant.

[cs]

I think the rationale of AVI is that you listen to the reverberant field, so acoustic alignment is meaningless. Seems to be born out by their tests.

I believe they use 4th order Butterworth filters. There is quite a lot of info on their site.

[soongsc]

It does save lots of development effort if they make that kind of assumption.

[phase_accurate]

..... and they are very good fortunetellers as well: They even know that I am listenig in the reverberant field.

Regards

Charles

[roland bios]

Hi there

I tried to time align my tweeters electrically with an alpass network some years ago. To align them with my mid. I could not hear an difference. (1.2cm back in time...)

If you time align a tweeter with 2 inches, how do the on and off axis measurements ever are going to add up?

Best Regards

Roland

[cs]

Originally posted by phase_accurate
..... and they are very good fortunetellers as well: They even know that I am listenig in the reverberant field.

Regards

Charles

A pretty safe assumption, I would have thought.
Unless you are in the habit of listening to your system, either with your ear pressed against the speakers, or in an anechoic chamber !

I have tried delay compensation with active speakers in the past, and agree with AVI - it makes absolutely no difference !

[DorinD]

Originally posted by cs
...I have tried delay compensation with active speakers in the past, and agree with AVI - it makes absolutely no difference !

Same from my exps. But we are in danger to get in trouble.