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GregS[_3_] GregS[_3_] is offline
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Default LA Sound Redondo 80 ... simple questions

In article , (GregS) wrote:
In article , "MOSFET"
wrote:
First, everything Lull said is right on track as usual. But let me add a
few things.

You wondered about impedences and why some are 8 and some are 4. Well, the
reason for this has to do more with tradition than anything else. Car audio
speakers are almost ALWAYS 4 ohms, the only exception to this can be found
in modern automotive subwoofers which will often have dual (or even
quadruple) voice coils and by wiring these in certain ways (parellel,
series, or some combination of both as is the case with my two dual voice
coil subs) you can achieve a particular desired impedence to maximize the
power your sub-amp can produce.

Home speakers on the other hand are almost ALWAYS 8 ohms. I have been into
car audio for nearly 30 years and I have never taken the time to find out
why the difference, perhaps an EE can offer an explanation as to why the
impedences differ.


Way back, 3.2 ohms was very common, and I don't know why. Even in tube
radios, they used 3.2. 4 ohms was used in the car because you only
had so much voltage drive to work with, with the exception of that
tube issue. Most transistor radios had one output referenced to ground. With a
14 volt charging
system, that left about 6 watts out max. 8 ohms would be 3 watts.

8 oms is also far above line losses, and the need for thick wire.
Today there is still a practical limit on output voltages, but car
audio has no excuse to not up the ohms, because switching supplies
can supply all the voltage you need.

greg


Ther is still one other thing. I have seen drivers with 4 ohm vs 8 being more
efficient and having better Qts, meaning smaller box. Resistance
is really an unwanted thing for efficiency.

greg