From: mark_zacharias@labolgcbs.net
"Trevor" wrote in message
news:m5oi4e$bot$1@speranza.aioe.org...
> On 3/12/2014 12:21 AM, Mark Zacharias wrote:
>> "Trevor" wrote in message
>> news:m5jjac$s85$1@speranza.aioe.org...
>>> On 2/12/2014 12:19 AM, thekmanrocks@gmail.com wrote:
>>>> geoff: My 1995 JVC receiver specifies 8-16ohms. Guess that's an
>>>> oldie then!
>>>>
>>>
>>> Many cheap receivers with limited current capability specify 8 ohms or
>>> more, regardless of age. Conversely many good amps can handle loads as
>>> low as 2 ohms without a problem.
>>>
>>
>>
>> Speaker impedances have not really changed - they are rating them a bit
>> more accurately these days.
>>
>> Mark Z.
>
>
> Partly true to the second part, mostly no to the first part. Some
> manufacturers use the impedance minimum fairly closely these days. Others
> are just an estimate of what they think the amp rating should be. But
> speaker impedances HAVE generally dropped over the last 50 years or so.
> First with the change from valve amps they generally went from ~16ohm to
> 8ohm. Then with the improvement in current handling of transistor amps
> (and the increase in multiple small bass drivers vs one larger driver),
> many have dropped from ~8ohm to ~6 or 4 ohm.
> In any case ALL speakers vary wildly in *impedance* across the frequency
> range, especially ported speakers, but the voice coil *resistance* of many
> drivers has decreased. That affects the system impedance, and is easy to
> measure. And some manufacturers still produce their drivers with voice
> coil resistance options, or even custom make them if you buy enough.
>
> Trevor.
>
>
What I meant to suggest is that so-called "8-ohm" speakers have always
actually been closer to 5 or 6 ohms. Should have been clearer.
mz
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