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Old 13th July 2006, 17:15   #16
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Ya sure I know it is not related to ICE..........

Ok will have to go to diy for this answer then...........

and read book that u recommended.....
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Old 13th July 2006, 22:22   #17
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Quote:
Originally Posted by low_bass_makker
and read book that u recommended.....
No rush I have not read them either! ;-) but I had great teachers and most of them are dead or really old now. I met B&T a few days ago and tld him about a few of them over tea.
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Old 13th July 2006, 23:12   #18
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I wish i was in bombay so that i could meet u in person and discuss on the following stuff and B&T will also join us as he is now married to me.....lol
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Old 14th July 2006, 10:06   #19
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B&T's knowledge is much more current (and so is Tool's) and you are quite close to Gunbir and JB. Besides no meet is compelte without Sam.
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Old 30th August 2006, 13:19   #20
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navinji, B&T, I have a question for you which I hope to get answered without going into too much of technical complexities (without going to the extent of reading textbooks!). Here it is:

all speakers generally have low impedence ranging from 2-8 ohm, except for head or ear phones which usually have 32 ohm. It leads to certain disadvantages which all audio companies strive to solve- 1. we need cables/connectors with very low resistance 2. amplifier design becomes difficult, and also the damping factor reduces. I believe the damping factor is defined in many ways in different contexts, I am referring to the ratio of speaker impedence to amp's output impedence here.

The question is, why can't we have speakers with high nominal impedences to solve above problems? is there any fundamental limitation?

I am sure there must be some advantages of low speaker impedence or disadvantages of making it high, which I am obviously unaware of!
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Old 30th August 2006, 13:49   #21
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Quote:
Originally Posted by santosh.s
The question is, why can't we have speakers with high nominal impedences to solve above problems? is there any fundamental limitation? I am sure there must be some advantages of low speaker impedence or disadvantages of making it high, which I am obviously unaware of!
I am not as knowledgeable as navin ji and b&t are but from my side

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

now increasing it to a certain level can be done after that the DC-DC converter will demand huge power requirment thats why the impedences are reduced to achive the net output.....
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Old 30th August 2006, 14:00   #22
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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 30th August 2006, 14:12   #23
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I home audio the 220 volts are drop down to lower levels to the desired level according to the sound output required....

here is a pic of a amp toridal transformer this amp is capable of 800 x 2 rms at 2 ohms and 1600 x 1 rms at 4 ohms...... in this also the voltages are step down as per requirment....

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Old 30th August 2006, 16:52   #24
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I didn't get the point. you said in car we can not increase speaker impedence because we would need DC-DC voltage upconversion (and it is not good for whatever reason). But when we have 220V supply DC-DC reasoning is ruled out. Then why do speakers still have low impedance? In other words, it seems to me that there should be other compelling reasons to keep the impedance low. Right?
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Old 30th August 2006, 17:05   #25
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the mosfet working voltage........I think it would limit its operation...

I might be wrong on the mosfet voltage part will have to confirm....but 99% i am sure.....
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Old 30th August 2006, 17:20   #26
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Quote:
Originally Posted by santosh.s
navinji, B&T, I have a question for you which I hope to get answered without going into too much of technical complexities (without going to the extent of reading textbooks!). Here it is:

all speakers generally have low impedence ranging from 2-8 ohm, except for head or ear phones which usually have 32 ohm.
most amps are voltage amplifiers. that is they take a 1V signal and amplifiy it to 40V for example.

1V at 8 ohms = 1/8W
40V at 8 ohms = 1600/8 = 200W

Now change impedance to 32ohms and see how watts drop!

However if you had a very senstive speaker say 110db/1W/1m that had an impedance of 32 ohms it would work. then again such speakers have other problems (reduced bass response etc...).

BTW there were a few high impedance speakers made in the early days (tube amps) most were horn loaded.
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Old 30th August 2006, 18:02   #27
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so does that imply amps have a higher limit on their output voltage, and hence speakers have to have low impedance in order to get enough power?... which is at the cost of high currents. For example, MOSFET as mentioned by LBM can put such an upper limit.
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Old 30th August 2006, 18:06   #28
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Quote:
Originally Posted by navin
BTW there were a few high impedance speakers made in the early days (tube amps) most were horn loaded.
the earlier days the impedence was high as the amp could not handle the low impendence load........they were not capable of this type of low impednce driver.....
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Old 30th August 2006, 18:10   #29
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Quote:
Originally Posted by santosh.s
so does that imply amps have a higher limit on their output voltage, and hence speakers have to have low impedance in order to get enough power?... which is at the cost of high currents. For example, MOSFET as mentioned by LBM can put such an upper limit.
Sir I cannot understand ur question you are asking...
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Old 31st August 2006, 11:13   #30
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santosh, amps tend to be current limited rather than voltage limited but given that current and voltage are related you can say that amps are voltage limited at particular resistance loads.

say your amp is producing 40V. At 32ohms that is 50W at 1 ohms that is 1600W. Now at 32ohms the amp is also putting out about 1amp but at 1 ohms the amps i putting out 40A. Your amp will safely drive a 32ohms speaker for hours a end but might baulk at driving a 1 ohm speaker. more about amplifers can be found here.

http://electronics.howstuffworks.com/amplifier2.htm

it is a combination of trade offs that arrived at the 4-8ohms impedance of loudspeakers.

some more information can be gleaned from here
http://www.enjoythemusic.com/magazin...autoformer.htm
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