In article , Eeyore
wrote:


Jim Lesurf wrote:

wrote:
On 14 Oct, 00:40, Eeyore
wrote:

It's a 'well known fact' amongst audio professionals. Google it.

For some reason I have come to be wary of claims thrown around on the
basis of being a "well known fact".

It was actually intentionally slightly tongue in cheek, but remeber I am
referring to PEAK levels not average levels which dB meters read.

I was aware of that. For all I know, the claim is quite accurate. But the
problem is the one I described.


That sometimes seems to mean, "Loads of people have been saying it to
one another on the basis that someone else told them. They've been
doing this for so long that no-one can recall who made it up in the
first place." :-)

See above.

See above. :-)



Clearly then, you'll know that having two speakers increases the
nominal sensitivity by 3dB for a central sound, and having them in
an average living room gives you another 3dB or so of reverberant
sound, so you can hit a 120dB peak from 91 db/watt speakers with
about 23dB of amp power, which is 200 watts. Not trivial, but
readily obtainable from many modern amps.

FWIW The effect of room reverb in UK domestic rooms might be somewhat
higher than a 3dB gain. I did some analysis of this a while ago (see
Hi Fi News August 2008). Hard to give a figure as it will probably
vary from room to room, but 3dB may be on the low side as an estimate
of what is typical. IIRC some texts also give details that indicate
well above 3dB for this.

3dB relative to WHAT ?

If you look at what Stewart wrote (Hi, Stewart! :-) ) that seems to be
comparing the effect of the room reverb with a situation where such reverb
would be absent. At least that is my understanding of his saying,
"...having them in an average living room gives you another 3dB or so of
reverberant sound..." If that is wrong, I'm sure he will correct me, but
that was what I then was referring to. Sorry if you didn't follow what I
wrote.


Are you familiar with nearfield and farfield measurements ?

Yes - although you haven't said which particular mechanisms you have in
mind for the factor(s) which affect how they differ, so I don't know which
one(s) you have in mind. Have you read the article I referred to?


That said (again as discussed in the HFN article) there is a
distinction between the actual instantaneous peak measured power, and
the peak level perceived, due to the way human hearing tends to
'integrate' the effect of short term delayed reflections into one
percieved peak.

Quite. It's not simple.

That was indeed, part of my point. :-)

Slainte,

Jim

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