Re: Impedance Matching Volume Control

["Robert L Bass" <robertbass1@xxxxxxxxxxx>]

>> I disagree.  70-Volt (and 25-Volt) systems
>> are primarily used for offices.  Most are
>> mono -- not stereo.
>
> If you only run two wires, mono
> is all you get, transformers or not...

True, but I believe the gentleman has run separate cables for stereo speakers.

> It should be pretty obvious that it
> takes at least three wires (and two
> sets of transformers) to deliver two
> channels. It should also be obvious
> that 70-volt transmission systems
> can be used for two-channel sound
> systems -- and in fact are, regularly.

They are rarely used for residential music systems.  The audio quality is usually poor.  Most home stereo amps don't support 25/70
Volts.

>> Sound quality is what you expect
>> in an elevator.
>
> In fact, it is possible to buy 70-volt
> audio transformers that have pretty
> decent characteristics (i.e. better
> than the speakers you intend
> to drive with them)?

Having worked with both 70-Volt and 8-Ohm systems over the years, I find the former to be almost invariably of poorer qudio quality
than even moderately priced conventional systems.  Yes, you can find "decent" quality 70-Volt components.  However, for similar cost
you can get superior quality 8-Ohm systems.

> 70 volt transmission systems solve
> a lot of other pesky problems,too;
> not least of which is the ability to get
> lots of volume from good speakers
> in a big room while not blowing out
> the small ones in a bathroom...

Actually, the primary use of 70-Volt systems is to get cheap sound out of *lots* of speakers.

> IOW, the reason professionals use that
> method is NOT because it's low in quality
> or low in cost.

Professional home audio installers rarely select 70-Volt systems and for good reason.  FWIW, I've designed and built custom home
theaters and multi-zone entertainment systems for years.  I also sell these systems online to DIYers.  I have access to various
70-Volt systems as well.  I choose not to offer them for residential installations.

--

Regards,
Robert L Bass

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