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Old 12th May 2008, 02:26 AM   #1
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Question 3 Way Power Distribution

I can't seem to find any useful info on the power consumption of individual speakers based on frequency in a 2 or 3 way. For example, How much power does a tweeter crossed above 3000 Hz use in comparison to a woofer crossed below 500 Hz?

Any formulas or links to this info. I appreciate anyone's help.
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Old 12th May 2008, 10:52 AM   #2
sreten is offline sreten  United Kingdom
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Hi,

The 50% power point is ~ 350Hz for rock, a little higher for classical.
Treble wise peak and average powers are rarther different, average
levels above 3kHz are low, but peak levels not so much.
Mid/treble split around 3Khz of the remaining 50% is ~ 30%/20%.

For bi-amping with the same amplifiers active bass/mid and passive
mid/treble (possibly with active BSC) is an attractive option, see :

http://www.musicanddesign.com/HybridDesign.html

/sreten.
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Old 13th May 2008, 01:01 AM   #3
gedlee is offline gedlee  United States
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Default Re: 3 Way Power Distribution

Quote:
Originally posted by kucharcity
I can't seem to find any useful info on the power consumption of individual speakers based on frequency in a 2 or 3 way. For example, How much power does a tweeter crossed above 3000 Hz use in comparison to a woofer crossed below 500 Hz?

Any formulas or links to this info. I appreciate anyone's help.
The reason that you can't find any information is because its a dificult problem. SO much depends on the spectrum of the music. One can talk about a "typical" selection, but then I could always find an atypical example that was completely different. When talking about power you have to remember to talk in linear frequency terms. In other words for a broadband noise spectrum there is as much "power" from 1000 Hz to 2000 Hz as there is from 0 Hz to 1000 Hz. Its just that most music tails off in spectrum at the top end, above about 1000 Hz.

When an amp clips it shifts the spectrum upwards and this changes the "typical" spectrum dramatically. This is why a short blast of a clipped signal can take out a tweeter almost instantly.

In real terms, tweeters take a lot more power than woofers. Consider a woofer from 0 - 1000 Hz. and a tweeter from 1000 Hz up to 20 kHz. The tweeter is getting 19 times more power than the woofer.
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Old 13th May 2008, 06:41 AM   #4
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Thanks to both of you for your replies. They were both very helpful. While I don't quite understand why a tweeter would possibly use 19 x's the power of a woofer above 1000 Hz, it's more logical for me to see the the power to be 30/20 %(Mid/Tweet) above 350 Hz. However I'm not an expert and I respect all responses.
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Old 13th May 2008, 09:42 AM   #5
sreten is offline sreten  United Kingdom
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Default Re: Re: 3 Way Power Distribution

Quote:
Originally posted by gedlee

In real terms, tweeters take a lot more power than woofers. Consider a woofer from 0 - 1000 Hz. and a tweeter from 1000 Hz up to 20 kHz. The tweeter is getting 19 times more power than the woofer.
Hi, Care to expand on this garbage ? /sreten.
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Old 13th May 2008, 12:20 PM   #6
gedlee is offline gedlee  United States
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Default Re: Re: Re: 3 Way Power Distribution

Quote:
Originally posted by sreten


Hi, Care to expand on this garbage ? /sreten.
Not with an insulting statement like that.
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Old 13th May 2008, 02:41 PM   #7
sreten is offline sreten  United Kingdom
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Default Re: Re: Re: Re: 3 Way Power Distribution

Quote:
Originally posted by gedlee


Not with an insulting statement like that.
Hi,

You said it without qualification, I didn't.
It only applies to white noise which is irrelevant.
The statement is completely wrong.

/sreten.
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Old 13th May 2008, 05:46 PM   #8
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While I have not done a comprehensive study of this, when trying to answer the same question I have written a program in Matlab that takes a chunk of a song in, breaks it up into octave-sized frequency bands, and then computes the rms power in each of those bands. After sending in about a dozen "typical" songs (reasonably uncompressed rock songs), I found that the energy per octave is slightly downward-tilted in frequency and falls off pretty quick below 30 Hz. If I break the signal up into say, 20-80 Hz, 80-250 Hz, 250-1.5k Hz, and 1.5-20 kHz the power going into each of these bands is pretty close.

The EIA 426B standard noise is designed to approximate the power distribution in music. The frequency content of this is as such: 4th order BW highpass at 40 Hz, half order lowpass (-3 dB/oct) at 1 kHz. What I have observed is "on average" consistent with this.
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Old 13th May 2008, 05:55 PM   #9
gedlee is offline gedlee  United States
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This is quite reasonable.

Had the other "gentleman" not been so rude, I would have pointed out that my claim was for noise as implied by the context of the note. With a -3 dB slope to the noise (i.e. pink) the power frraction above about 1 kHz will be about 1/2 the total. At -0dB it with be 19/20 the the total just as I claimed.
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Old 13th May 2008, 06:09 PM   #10
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If you mean the 426B noise, the filter is applied to pink noise, not to white, so the power per octave is itself decreasing above 1 kHz.
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