Time aligment with an Alyec 511B horn and woofer necessary ?

[MerlinVSM]

The speaker include an Altec 511B horn and a Acoustic Elegance dipole 15 inch woofer, on a aluminium baffle.

When looking at the vintage Altec Santiago, Valencia the horn seams to be mounted on the same plane or even little behind the woofer, estimated 2-5cm .

However, on the Altec A7 the horn is placed substantially in front of the woofer.

Is time aligment something to bother about ?

Well, with regard to time alignment where to put the horn ?

a) Just mount it on the same baffle as the woofer ?
b) Little bit behind the baffle
c) Substantially in front of the woofer i.e align the horn and driver coils ?

I thought c) was the right thing to do but when loking at the Santiago or Valencia...

How does it come that it differ between the Altec A7 and Santiago ?

[Cal Weldon]

You're likely to get many opinions on this.

When I was a young man we were taught to align the coils. This has been challenged. Not sure why, but apparently with a horn, things are different so the acoustic center might not be the coil.

My A7's with the 511 horn have the coils lined up.

Time alignment is important to some but others don't notice. The is a theoretical distance that must be achieved before your brain can detect a difference. I forget what that is right now, but it's less than a foot IIRC. It's measured in m/s. I'll go look for ya.

I think C is the right answer from my experimenting.

Altec didn't think it was as important as some people do. Just like Altec never seem to use their L-Pads as anything but a variable resistor. Go figure...

EDIT: If sound travels at about 1 foot per millisecond and you have trouble discerning a difference of 10 milliseconds then your woofer and tweeter, if crossed over very steeply could be 10 feet apart. If there is overlap at the XO you would notice them being out of alignment as you would run into phase cancellation issues. This can happen at about 1 foot distance apart. Probably best just to line up the coils.

[amandarae]

The speaker include an Altec 511B horn and a Acoustic Elegance dipole 15 inch woofer, on a aluminium baffle.

When looking at the vintage Altec Santiago, Valencia the horn seams to be mounted on the same plane or even little behind the woofer, estimated 2-5cm .

However, on the Altec A7 the horn is placed substantially in front of the woofer.

Is time aligment something to bother about ?

Well, with regard to time alignment where to put the horn ?

a) Just mount it on the same baffle as the woofer ?
b) Little bit behind the baffle
c) Substantially in front of the woofer i.e align the horn and driver coils ?

I thought c) was the right thing to do but when loking at the Santiago or Valencia...

How does it come that it differ between the Altec A7 and Santiago ?

http://audioroundtable.com/misc/Altec_AN-9.pdf

[donaldpatten]

MerlinVSM
Yes ,aleast line up the coils.
You can test your choice, and fine tune the position.
I used the method described in my web site to tune 605s and 604s. Since the horn is fixed the XO was designed with the proper delay.
You could use my test pulse to get th sweet spot to mount the horns. Remember any coils in the XOs cause delay.

www.donpatten.com