"Jim Lesurf" wrote in message
...
In article , Peter Scott
wrote:

Hence what we get may be nothing like either 6dB or 3dB. Depends on the
details.

In practice, the speaker designer is probably trying to get a given
response, but has to worry about the user-choice of speaker and listening
locations and room acoustics all being outwith his control, and varying
from one user to another. Thus the designer has to make a 'guess' as to
what will suit enough people to make a speaker a commerical success!

Thanks for clarifying that. The more you think about it the more of a
compromise loudspeaker design is. Bit like designing a vehicle that might
run
on a road or perhaps on fields or up mountains, or maybe on water or.....
This must also be true for high-end speakers unless the designer exactly
specifies the room, speaker positions and surfaces. Going back to another
discussion perhaps there ought be a test criterion along the lines of
'performs well in a wide range of environments'? This might prove to
be a crucial, if not *the* crucial, factor for speakers.

In my question I was thinking of a simpler matter. According to Behringer
two speakers next to each other, so acting as a single point-source, would
show 3dB gain at low frequencies. I should have specified the frequency.
This region is on my mind because I'm pondering what to do about
the design for a sub-woofer. B says you need four drivers for 6dB.
Clearly this will not be the perceived gain throughout the listening
area but just that near the speakers.

Peter Scott