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Old 31st August 2006, 13:10   #31
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Quote:
Originally Posted by low_bass_makker
Sir I cannot understand ur question you are asking...
Navin has already explained it.

Nevertheless, here is what I meant-

power that an amp can feed is proportional to both V and I
power P = V*I => (V^2)/R => (I^2)*R

For a give R, the way to get more power is to increase V, which implies that I=V/R will also automatically increase. If amp has no upper limit on V that it can produce, then there is no problem. We can increase speaker impedance to whatever extent we want by making the amp feed high voltages to it.

But if amp has upper limit on voltage, let us say 40V (no limit on current). then it becomes the limiting factor on how much max power that can be fed to a given speaker.
For R=2ohm P is 800W (I=20A)
For R=4ohm P is 400W (I=10A)
For R=8ohm P is 200W (I=5A)
... and so on.
So due to the limit of 40V, we have to stay below 8ohm if you want at least 200W.
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Old 31st August 2006, 13:20   #32
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Quote:
Originally Posted by low_bass_makker
we all have heard of the ohms law....

v=ir

v-> volts
i-> current
r-> resistance

if we increase the impedence of the drivers the amp will also have to increase the voltages of the whole setup to achive the desired output...

if we keep the current constant as we dont want to change the output and change the other values one can see the differnce....

v=12 volts
r=4 ohms
i=3 amps

now if we change the r to 8 ohms the current will drop to 1.5 amps so to keep the output same we have increase the voltage which we calculate will comes to 24 volts.

Now take a case of car audio the voltage have to be increased to achive an certain output
I think I have said it before.......
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Old 31st August 2006, 13:26   #33
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Originally Posted by low_bass_makker
I think I have said it before.......
then how come you said that you didn't understand the question?
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Old 31st August 2006, 13:38   #34
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Quote:
Originally Posted by santosh.s
then how come you said that you didn't understand the question?
I was asking this question....

Quote:
Originally Posted by santosh.s
LBM, in fact the question came to my mind because of this basic power equation itself, which is discussed in "thick wire" sticky... voltage conversion is applicable to car but then even home speakers have similar impedance. Here we already have high enough voltage available !!??
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Old 31st August 2006, 14:02   #35
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Quote:
Originally Posted by santosh.s
So due to the limit of 40V, we have to stay below 8ohm if you want at least 200W.
FYI: To be clear 40V is a arbitrary limit of a hypothetical amp we used just to clarify this issue. it is not the limit of all amplifiers.
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Old 31st August 2006, 14:24   #36
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Quote:
Originally Posted by low_bass_makker
I was asking this question....

Quote:
Originally Posted by santosh.s
LBM, in fact the question came to my mind because of this basic power equation itself, which is discussed in "thick wire" sticky... voltage conversion is applicable to car but then even home speakers have similar impedance. Here we already have high enough voltage available !!??
Hey LBM, the message that you quoted in your post #29 was something else!
sorry to feed your own stuff back to you... didn't notice what I was doing

Now let me explain it-
by "in fact the question came to my mind because of this basic power equation itself, which is discussed in "thick wire" sticky..."
I meant theoretically speaker wires could have been thinner if there were speakers with high impedence and amps capable of driving enough power into them. Also the system could have been more tolerant to bad contacts and connectors.

by "voltage conversion is applicable to car but then even home speakers have similar impedance. Here we already have high enough voltage available !!??"
I meant if DC-DC conversion was the limiting factor, not amp itself, then in home system we could have used higher voltage supply which is difficult in cars due to DC-DC conversion issue. Since we have AC supply at home, we can achieve any voltage using a transformer, no DC-DC required. However it doesn't seem to be the case since home speakers also have as low impedance as in cars. So I thought there should be other reasons too.

Hope I clarified it well...
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Old 31st August 2006, 14:28   #37
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Quote:
Originally Posted by navin
FYI: To be clear 40V is a arbitrary limit of a hypothetical amp we used just to clarify this issue. it is not the limit of all amplifiers.
yes, me too used it as an arbitrary value just for the sake of explanation.
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