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Old 28th Mar 2012, 12:11 am   #9
mhennessy
Dekatron
 
Join Date: Jul 2007
Location: Evesham, Worcestershire, UK.
Posts: 4,241
Default Re: Radio 5 Live Echo (Empty Hall) Effect ?

Hmm - just because the OP said "echo", it doesn't mean that this is what he's specifically hearing. He also said "empty hall", and this is far more telling. Much shorter delays than 100ms cause the effects described - that of giving the impression of hearing reverberations in a large room - just have a play with an FX box to get an idea of the delays involved. Just a few ms is enough to upset a stereo image - indeed such delays are routinely used in recording studios to "excite" instruments in a mix. A few 10ms of ms is enough to upset a presenter (hearing themselves delayed in their "clean feed"). A delayed signal mixed with the original will also cause comb filtering effects.

As to the OP's original question, I'm afraid I have no "inside knowledge", but I'll ask around to see if anyone knows anything about AM distribution these days. I know how FM is done, but obviously that's different. It's perhaps not too surprising that you also get the same effect with R4 FM and LW...
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