Biwiring vs biamping - AVS Forum
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post #1 of 15 Old 09-20-2012, 05:56 AM - Thread Starter
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I'm pretty sure I understand what biamping is. 2x the power into one speaker using 2 channels instead of 1ch. What I don't really understand is what biwiring is/does. Is it 2 pairs of wires coming from one amp channel? If so, what good does that do? Does it distribute the power between the different components in the speaker? I can see pros and cons with this, but seems like the traditional "single wiring" would be good enough. I don't own speakers that do either one but just wondered what the deal was. Thanks for the help.
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post #2 of 15 Old 09-20-2012, 07:16 AM
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Originally Posted by ambesolman View Post

I'm pretty sure I understand what biamping is. 2x the power into one speaker using 2 channels instead of 1ch. What I don't really understand is what biwiring is/does. Is it 2 pairs of wires coming from one amp channel?

Yes, with each pair of wires connected to a different pair of terminals on the back of the speakers. The two sets of terminals are sometimes there, provided for separate connections to the high and low frequency parts of the speaker. They pass a signal to the drivers through the passive crossover inside the speaker box.
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If so, what good does that do?

Not a heck of a lot for the user, but it doubles the speaker cable footage sales volume for the dealer. bi wire = buy wire! ;-)
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Does it distribute the power between the different components in the speaker?

Yes that's one way to distribute the power. The other way involves jumpers between the pairs of terminals. They accomplish essentially the same outcome at a far lower cost and complexity.
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I can see pros and cons with this, but seems like the traditional "single wiring" would be good enough. I don't own speakers that do either one but just wondered what the deal was. Thanks for the help.
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post #3 of 15 Old 09-22-2012, 11:17 AM - Thread Starter
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bi wire = buy wire! ;-)

That's funny AND accurate. That's what I figured but the presence of jumpers seems to make this pointless since that same power would still be going to the components.
Reminds me of when my cousin sold his old truck. He had added a dual tank switch on the dash for the hell of it. When the buyer asked him about it he said, "well, when you get down to a half empty tank you just flip the switch and then it's half full." There's one born every minute smile.gif
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post #4 of 15 Old 09-22-2012, 04:01 PM
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Aside: Even active bi-amping does not double the power into the speaker. If you have two 100 W amps and split the signal into low and high parts, then you have 100 W on the lows and 100 W on the highs just as before. It is not the same as using a 200 W amp. While there can be benefits to bi-amping by distributing the load and eliminating the passive crossover, increased power is not one of them, unless you buy bigger amps.

Bi-wiring an benefit if the increase in effective wire guage is helpful in reducing loss or lowering the effective driving impedance, or if the isolation provided by the extra wire helps the amp by reducing charge kick back to the amp. Neither is likely to be audible.

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post #5 of 15 Old 09-23-2012, 05:28 PM
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I assume that you are referring to speakers that have separate terminals for the woofer and tweeter. The main advantage of bi-wiring is that the the audio current feeding the LF drivers (woofers) will interfere much less with the HF (tweeter) audio. The woofers consume MUCH more power than the tweeters and with a single pair of wires the tweeter current will end up being slightly "modulated" by the woofer signal, which may cause a small amount of harmonic and/or phase distortion. This occurs because of voltage drop in the wires, which have a small but finite amount of resistance. By running separate wires to the HF drivers the LF drivers you isolate the LF signal and lessen this problem.

Even with bi-wiring the interference will still occur to a small extent because the amp isn't perfect either; like your cables it has a finite output impedance, and a small amount of voltage drop in its internal wiring. But bi-wiring will eliminate most of the interaction between the 2 drivers, except when you approach the amplifiers full power output.

If your speakers have just one set of terminals each, then bi-wiring will just double the speaker gauge and halve the resistance. This will improve LF-HF interference also, but there will be less benefit in this case.
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post #6 of 15 Old 09-23-2012, 05:31 PM
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The main advantage of bi-wiring is that the the audio current feeding the LF drivers (woofers) will cause interfere much less with the HF (tweeter) audio. The woofers consume MUCH more power than the tweeters and with a single pair of wires the tweeter current will end up being slightly "modulated" by the woofer signal, which may cause a small amount of harmonic and/or phase distortion. This occurs because of voltage drop in the wires, which have a small but finite amount of resistance. By running separate wires to the HF drivers the LF drivers you isolate the LF signal and lessen this problem.

Even wioth bi-wiring the interferance will still occur to a small extent because the amp isn't perfect either; like your cables it has a finite output impedance, and a small amount of voltage drop in its internal wiring. But bi-wiring will eliminate most of the interaction between the 2 sets of speakers, except when you approach the amplifiers full power output.
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post #7 of 15 Old 09-23-2012, 07:41 PM
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Would you care to explain the reasons behind your statement?

I've been an audio engineer / technician for 35 years and feel that I have some pretty good credentials, which I'll be glad to detail if anyone's interested.

Kind regards...David

www.studioelectronics.biz
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post #8 of 15 Old 09-23-2012, 07:48 PM
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Originally Posted by vinyl collector View Post

. . . The woofers consume MUCH more power than the tweeters and with a single pair of wires the tweeter current will end up being slightly "modulated" by the woofer signal, which may cause a small amount of harmonic and/or phase distortion. This occurs because of voltage drop in the wires, which have a small but finite amount of resistance. . .
Sorry, no. That is somebody's fantasy story.

First, the woofers do not consume much more power. They consume what is fed by the amp, based on their impedance. The impedance of both the tweeter and woofer should be approximately the same, so the power is also approximately the same. The "more-power" misconception is based on the fact that the bass can sound louder and the woofer is typically bigger and heavier.

Second, frequencies do not "modulate" each other over a cable. If they did, you could not have Ethernet-over-powerline (an electric dryer, at 60hz, does consume much more power than an Ethernet node) or different cable-channels on the same RG6 cable, or even audio and video on the same composite-video cable.
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post #9 of 15 Old 09-23-2012, 09:08 PM
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Originally Posted by MarkHotchkiss View Post

Sorry, no. That is somebody's fantasy story.
First, the woofers do not consume much more power. They consume what is fed by the amp, based on their impedance. The impedance of both the tweeter and woofer should be approximately the same, so the power is also approximately the same. The "more-power" misconception is based on the fact that the bass can sound louder and the woofer is typically bigger and heavier.
Second, frequencies do not "modulate" each other over a cable. If they did, you could not have Ethernet-over-powerline (an electric dryer, at 60hz, does consume much more power than an Ethernet node) or different cable-channels on the same RG6 cable, or even audio and video on the same composite-video cable.

Actually the woofer and tweeter would use the same power only if playing white noise, which by definition averages equal power at every frequency. My understanding is that pink noise is typically used because it sort of more closely resembles the power distribution in real program material, and it averages equal power in each octave. So the frequencies from 2000 to 16000 Hz are equla in power to the frequencies from 40 to 320 Hz in pink noise. In general, my internet research on the point several years ago suggested that for typical real program material the fifty fifty split point is around 600 Hz. Many powered speakers use separate amps for woofer and tweeter, and many use a much smaller amp for the tweeter, simply because program material requires less power. You can also see this in specs for some unpowered pro level PA speakers. Woofs might have a thermal rating of 500 watts while the horns driver will be 100 watts, for example.
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post #10 of 15 Old 09-23-2012, 10:32 PM
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Hi jHAz,

Thanks for that, it was very informative. But now to add:

As you said, white noise would have equal power at every frequency. So lets say X watts per hertz. If a two way speaker has a crossover at 5kHz, which is at the high end, then the woofer would receive just under 5,000 times X watts, whereas the tweeter would receive 15,000 times X watts, or three times the power. If the crossover was at a more normal 2.5kHz, then the tweeter would receive seven times the power with white noise.

But white noise is not a good example for the real world. Pink noise, with the crossover at 2.5kHz, would have the tweeter receiving the power of about three octaves while the woofer would receive the power of about seven octaves. So the woofer is indeed receiving more than twice the power.

Your research showed a power midpoint of around 600 Hz, whereas pink-noise would have a power midpoint near 660 Hz, so pink-noise might be considered not far from the real world.

So I stand corrected: The woofer might be expected to receive twice to three times the power of the tweeter in a real-world two-way system.

Am I off-topic yet?
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post #11 of 15 Old 09-23-2012, 10:46 PM
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I have never heard an audio difference bi-wiring.. My advice, bi-wire and see if you hear a difference. I never tried bi-amping due to the cost although I would I may have my dealer setup a demo for me just to see if I can hear a difference. After all bi-amping is quite costly, I need to hear an extreme difference to justify the price.
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post #12 of 15 Old 09-25-2012, 11:54 AM
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Originally Posted by MarkHotchkiss View Post

Hi jHAz,
So I stand corrected: The woofer might be expected to receive twice to three times the power of the tweeter in a real-world two-way system.

Yeah but the distances involved in typical bi-wiring shouldn't be enough to make a difference from a single point source in the low frequencies affecting the highs over the transmission line. (Where both wires are connected to one output terminal.) Someone can correct me if I'm wrong, but my understanding is that an inch of conductor isn't much different from 10' as far as electrical properties in the audio frequencies are concerned provided there's suitable gauge for both distances, so since the first inch or two inside the amp to the speaker terminals has both signals travelling through it... the next 10' shouldn't matter.

From a hands on perspective, I've tried bi-wiring many times and never was able to yield any difference at all.
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post #13 of 15 Old 09-25-2012, 11:58 AM
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Originally Posted by rlhaudio View Post

After all bi-amping is quite costly, I need to hear an extreme difference to justify the price.

Been there done that too, and passive bi-amping is pretty much a waste of time. Active bi-amping, where the crossover is before the amps, can have some appreciable benefits.
But to get it right is pretty tricky and you have to have faith that you can do a better job with the crossover than the speakers' designer did.
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post #14 of 15 Old 09-25-2012, 04:51 PM
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Originally Posted by vinyl collector View Post

The main advantage of bi-wiring is that the the audio current feeding the LF drivers (woofers) will interfere much less with the HF (tweeter) audio.

You seemingly lack formal education in basic electronics because:

The only way that the audio current feeding the LF drivers (woofers) would interfere with the HF (tweeter) audio flowing through the same wire would be if the wire had a nonlinear response to current flowing through it which copper wire most definitely does not have.
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The woofers consume MUCH more power than the tweeters and with a single pair of wires the tweeter current will end up being slightly "modulated" by the woofer signal,

This alleged modulation can only happen if the speaker wire is made from some highly nonlinear conductor such as corroded wire, or a semiconducting material such as silicon.
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which may cause a small amount of harmonic and/or phase distortion. This occurs because of voltage drop in the wires, which have a small but finite amount of resistance.

Wrong again. The resistive characteristic of ordinary copper wire is highly linear.
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By running separate wires to the HF drivers the LF drivers you isolate the LF signal and lessen this problem.

There simply is no such problem to lessen.

Please post again on this topic when you understand the basic linear properties of the kind of wire that is commonly used for speaker wiring.
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post #15 of 15 Old 09-25-2012, 05:05 PM
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Originally Posted by rnrgagne View Post

Been there done that too, and passive bi-amping is pretty much a waste of time. Active bi-amping, where the crossover is before the amps, can have some appreciable benefits.
But to get it right is pretty tricky and you have to have faith that you can do a better job with the crossover than the speakers' designer did.

And be willing to rip the crossover out of your existing speakers . . .
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