[sdiy] group delay (of filters) and listening

[Magnus Danielson]

From: "Czech Martin" <Martin.Czech at Micronas.com>
Subject: RE: [sdiy] group delay (of filters) and listening
Date: Thu, 7 Oct 2004 09:29:54 +0200
Message-ID: <D9D56E8FA1A73542BE9A5EC7E35D37FF01C4F20E at EXCHANGE2.Micronas.com>

Martin,

> <Right. You don't need anechoic rooms by the way, you can do pseudo-anechoic
> <measurements easilly. On and off axis naturally. Off-axis is really not only to
> <the side put also up down, effectively at different points around the speaker.
> 
> What do you mean by pseudo-anechoic? Lawn?

No, what you do is that you measure the impulse responce of your speaker and
then cut it short just before the first reflection. By moving the first
reflection (ground) away from the speaker (rising the speaker and measuring
mike up from the ground on a riser) the first time the surrounding gets a
chance to do anything with the responce we say "cut! Thank you!" and move on.
So, even if it certainly not is an anechoic environment, the first reflection
and any after it is removed from the responce and the end result is as if it
was playing in an anechoic chamber for real, just that we had a very short
sample of it.

I can tell you that this was great fun. I've listend many times to the MLS
signal and yes, it beats like hell! ;O) I had to avoid using it as a beat
pattern for myself... ;O)

Cheers,
Magnus