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Old 10th September 2011, 02:08 AM   #1
pos is offline pos  Europe
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Default high impedance load

Hi

Is there any downside, expect loss in available power, to present a very high impedance load (say 64 or even 128ohms) to an amplifier?
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Old 10th September 2011, 02:11 AM   #2
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It should be fine.
Valve amps are more touchy about speaker impedance.
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Old 10th September 2011, 09:26 AM   #3
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Thank you!

So no hill effect on frequency response if the amplifier was "calibrated" for a given load range (4-16 ohms), or anything?
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Old 10th September 2011, 10:59 AM   #4
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When one plugs in headphones the circuit sometimes switches off the speaker route to leave the headphones and their dropping resistor as the only load that the amp has to supply.

That is part of the reason that Thiele Networks or Zobels are fitted to the amp output, so that they remain stable into a wide variety of load impedances.
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Last edited by AndrewT; 10th September 2011 at 11:09 AM.
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Old 10th September 2011, 10:40 PM   #5
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Thanks a lot!
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Old 11th September 2011, 03:52 PM   #6
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How would you go about making up a speaker with an impedance of 64 ohm or so. You could wire up a whole lot of eighy ohm drivers in series. Some sort of modern day Bose 901 perhaps...?

Click the image to open in full size.

It's just that there is a ninth driver on the other side of the enclosure and the original was not wired in series....

Last edited by ingenieus; 11th September 2011 at 04:17 PM.
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Old 11th September 2011, 04:18 PM   #7
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Four goodmans axiom 10's in series at 15 ohm each, good for 35 to 15k

I do suspect we are talking headphones here, if not one has the other side of the coin, how do you swing enough voltage to get any power out of 128 ohm.
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Old 11th September 2011, 05:11 PM   #8
RJM1 is online now RJM1  United States
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Sounds like a job for a tube.
(((320V P-P)*0.3535) ^2)/128Ω=100W
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Old 11th September 2011, 07:22 PM   #9
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If I may correct myself - if you want a modern Bose 901, you can just buy it:

Bose 901 Speaker System ? Home Stereo Speakers - Bose Speaker Systems
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Old 11th September 2011, 09:22 PM   #10
RJM1 is online now RJM1  United States
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Bose, somwone stop me quick.

some 350 enhancements over the acclaimed original.

And what are they except for injection molded for added strength?
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