Jim Lesurf wrote:

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

An orchestra even in the auditorium can peak at over 120dB.

Do you have a reference for this? I have been looking for credible
sources for peak orchestral SPLs in the auditorium for a long while.

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.


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.


In other words completely useless because they haven't the tiniest
clue what they're measuring. Thankfully or even orchestras would have
to be banned from playing for HSE reasons.

However I have only semi-credible figures for places in the
auditorium and they only go up to 109 dB SPL.

IIRC I read an old article by John Crabbe a while ago that reported
measurements. I can't recall details, but if I do I'll report them.

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 ? Are you familiar with nearfield and farfield
measurements ?


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.

Graham