OT: Speaker systems was: Re: crystal clear : was : RE: [sdiy] Simple discrete Unity-GainFollower ?

[Magnus Danielson]

From: Tim Ressel <madhun2001 at yahoo.com>
Subject: OT: Speaker systems was: Re: crystal clear : was : RE: [sdiy] Simple discrete Unity-GainFollower ?
Date: Wed, 7 May 2003 23:08:38 -0700 (PDT)

> Yo,

Yo Tim,

> (This IS kinda off topic, after all...)
> 
> One of the amazing things about horn systems is the
> efficiency. I once held a speaker-warming party for my
> new Altec A-7 Voice of the Theater speakers. We had
> those monsters cranked until our ears bled. I glanced
> over at the power amp watt meters: 5 watts per
> channel.

Horns *ARE* very efficient. There is a number of issues to handle carefully.
I've used horn speakers in PA systems and they can fill a good spot. It is
however not my choice for the really large stadium gigs.

> Horns are acoustic transformers. They match the
> impedance of the driver to the impedance of the air.
> Because of this they are very efficient.

Indeed. The troubles is that all the traditional horn-shapes is not really very
good. One should use the ortonormal hyperbolic shape.

Also, you need to "terminate" the acoustical impedance of the horn edge
properly. Poor termination, especiall in horns with low mouth/throat ratio will
lead to zeros in the responce.

When you combine the lobes of several horns you need to make sure the shoot
their own part of the steradian space or else you will have interference
problems which is exactly what you want to avoid.

The 4-inch compressor drive into a 2 inch throath that we used kicked
136 dB(SPL) at 1 meter and the 10 inch mid kicked as with 139 dB(SPL) at
1 meter. We never used less than 4 such cabinetts a side as I recall it (I did
it once for a private gig, but then it was more than adequate anyway).

> When the engineers installed the A-7s in the Chineese
> theater in hollywood, they hand-wound crossovers coils
> until the system sounded right. That is what you have
> to do with passive crossovers. 

Yes.

> By the by: we were playing a sound effects CD with
> Huey helicopters on it. We had the neighbors thinking
> we were being invaded!!!

Hehehe...

Cheers,
Magnus