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Newbie question: Why AKG K1000 needs a powerful amp?

post #1 of 10
Thread Starter 
I am wondering why K1000 need a powerful amp, such as:RVK MkII, to power it.

Just look at the impedance, K1000 is just 120ohms, so most of the amp should able to power it up.

I know this is newbie question, but I really want to know the answer.

Thanks
post #2 of 10
Guess: Low Efficiency

output power = Efficiency x input power

If efficiency is low, you would need more input power to get the same output power as compared to a pair of more efficient cans.
post #3 of 10
I guess impedance only tells you one half of the story. Similar to speakers, which requires you to know the speaker impedance as well as sensitivity of the speakers in order to get the right amp to match it.
post #4 of 10
The K1000s are extremely inefficient. They are rated by the manufacturer to produce about ~100dB at 400 milliwatts at 120 ohms.

I use my K1000s with an amp rated at 10 watt per channel at 8 ohms. If I've done my Ohm's Law correctly, that comes out to only 666 milliwatts at 120 ohms. So I would need the output volume of this amp at about 2/3 its max to get to 100dB sound pressure, although that's way louder than I would normally listen.

In practice, for most of my listening, the volume control is anywhere from 30 to 50% of max, with a 10wpc amp. If I hook up the same amp to my loudspeakers (8ohms, rated 89/dB per watt) in the same room, at the same volume setting, the speakers are noticeably louder than the headphones, despite the headphones being right on my ears while the speakers are about 10 feet away.

It must have something to do with the unusual way the diaphragm and magnet structure works in the K1000s, and the fact that half the sound pressure goes out the back side of the wide open earpieces.


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post #5 of 10
Quote:
Originally posted by Northern Oak
Guess: Low Efficiency
Good guess, Northern Oak. The efficiency of the K1000s is extremely low at 74dB/mW. For comparison's sake, the K501 is rated at 94 dB/mW. They both have the same 120 ohm impedance.
Every 3 dB increase in sound level requires a doubling of the power. So you can see where the K1000 will eat up power to acheive a rather loud volume. To reach the 94 dB level of the K501 @ 1 mW, the K1000 would need more than 64 mW!
post #6 of 10
Thread Starter 
Thanks for all your help!

Another followup question, why AKG will build such Low Efficiency headphone? How come they don't build a more efficiency headphone, so that K1000 is more easy to power.
post #7 of 10
well, then it wouldn't be a k1000 anymore.

(but i guess the answer you're looking for has to do with its tranducer design. read the manual... the transducer is very different from those found in normal headphones. it produces the sound and performance that the k1000 is known for. doing it any other way would probably change the sound, for good or bad.)
post #8 of 10
Quote:
Originally posted by Uncledan
Thanks for all your help!

Another followup question, why AKG will build such Low Efficiency headphone? How come they don't build a more efficiency headphone, so that K1000 is more easy to power.
Well, the k1000s aren't offically considered headphones, but "earspeakers." Think of them as tiny speakers strapped to your head.
post #9 of 10
I don't think it's strictly a "think" issue. They *LOOK* like tiny speakers strapped to your head.
post #10 of 10
Quote:
Originally posted by Chinchy
I don't think it's strictly a "think" issue. They *LOOK* like tiny speakers strapped to your head.
Actually, with their metal mesh screens, they look more like old-time microphones than speakers to me. Hmmm, I wonder if anyone has ever attempted to wire them up as mics....
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