"The Flash" wrote in message ...
Your assertion that it is not possible to get low frequencies using an
8 inch driver turns out not to be correct. I have a pair where the LF
is done using 8 inch drivers in a bandpass enclosure. Those have a
measured response which is 1dB down at 30Hz, and an overall
response at 3dB down of 27Hz to 90Hz.

Ok, your using a pair of 8 inch drivers not a single driver, a band pass
enclosure to give base reinforcment. I have a Isobaric bandbass using two 8
inch drivers and yes it will produce low frequencies well, however its
response range is quite limited and its low effientcy is masked by its class
H amplifier inbuilt. I still doubt that you can get a true 'Hifi' response
from a system using a 8 inch driver per cabinet for the LF.

A couple of misconceptions here.

All else being equal, more drivers do not result in lower cutoff
frequencies, they result in more total acoustic power capability,
since you've increased the total displacement volume of tyhe system.

So-called (actually, mis-named) 'isobarik' systems are a way of
obtaining a given response in half the volume, since the arrangement
results in half the total equivalent compliance volume and thus
requires half the enclosure volume for the same response function.

As to "true hifi response," such a term needs definition to be
anything but meaningless jargon, in precisely the same way that
a "specification" like "20Hz-20kHz" is meaningless without
qualification.

THe fundamental efficiency/enclosure volume/cutoff frequency equation
will ALWAYS rule. But, interestingly enough, driver diameter simply
does not enter into that relation. Specifically, the relation:

n0 = kn Vb F3^3

where n0 is reference efficiency, Vb is enclosure volume, F3 is is
low frequency cutoff and kn is the efficiency constant has NO term
in it in any way depedent upon driver diameter. This directly refutes
your assertion that it's not possible to get your "unqualified" 'hifi
response from an 8 inch driver. One needs to simply balance the three
terms of efficiency, enclosure volume and cutoff frequency and you're
there. You seem to intimate that low efficiency is incompatible with
'hifi response," for example, an unjustifiable viewpoint in light
of the lack of qualification of 'hifi response.'