[Bob Urz]

On 8/1/2011 9:25 PM, Phil Allison wrote:
"Peter Larsen"

A sane way to design the 4 Ohm box would btw. be to stick with the same
midrange and top components as in the 8 Ohm box.

** Long as similar woofers and compression drivers are available in 4 and 8
ohms, that is the easiest way to do it.

( Note that the 8 ohm version uses a 16 ohm compression driver. )


But there sees to be no valid technical reason to make a 4 Ohm box for
those that can't afford large amplifiers if it ends up in toy class
efficiency so that they get more sound from the same amp by getting the 8
Ohm version.

** Obviously true.

Another way to convert any box from 8 to 4 ohms is to simply install a
matching transformer at the input, ie an auto-transformer that gives a 41%
step up in voltage.


A twist of the balance control is a much cheaper and simple way to match
efficiency in a situation where you cannot get the matched parts



A toroidal cored type would make it quite small and inexpensive too.


I have seem autoformers on permanent installs, but never have seem one
on a over the counter box for musicians internally. There would seem to
be no logical reason to add expense to a box other than to use matched
components. I have seem autoformer impedance matchers for home audio
that allows many speakers to be hooked to one amplifier. I have also
seen amps shutdown or fry if too much power is fed to one


BTW

The size of the magnet does not change with rated impedance - 4, 8 and 16
ohms versions have identical magnet structures.

Many lower end manufacturers change drivers at will on the same model of
speakers over a period of time. SO, it may not be a matter of same
basket or different Z, it could be an entirely different basket with
different magnet and voice coil size, type, or magnetic gap.

Anytime you buy an open box or factory second version of a speaker you
run the risk of internal components not being what you thought they were.

Even companies like Meyers are not immune from running model changes.
I think we were teching Broadway white Christmas awhile back and the
Sound consultants were having issues with voicing on the Meyer CQ's.
Turns out there are older and newer versions of CQ's and the components
are NOT the same and the box will not sound the same between the two
versions. The solution was to swap the one box for a CQ of the same
vintage

bob