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post #1 of 108 Old 09-24-2009, 08:09 PM - Thread Starter
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I Recently purchased a STRDA5400ES Sony receiver and a set of PSB ALpha T1 tower speakers. I noticed that the receiver offers a "Bi-amp" option, I realize that there are a lot of threads with people saying "don't bother". So my question is, what is the point of having the "bi-amp" feature on the reciever and should I use it? (I am currently using it and thought I could hear a difference, but to be fair, it could just be in my head)

Thanks in advance
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post #2 of 108 Old 09-24-2009, 08:55 PM
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If you truly have 2 amps to bi-amp with there can be a difference. Extreme example-you use a tube amp on the tweeter to roll off the highs to keep the dig harshness of a red book cd from being tiring, and use a SS amp for the woofers to get that sharp crisp slam. Then of course you have created another problem--balance
This is an over simplification but I hope it helps.

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post #3 of 108 Old 09-24-2009, 08:59 PM - Thread Starter
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Thanks, basically it sounds like your saying the bi-amp feature doesn't do anything, true?
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post #4 of 108 Old 09-24-2009, 09:12 PM
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Not unless you have 2 seperate amps. My Dennon 988 has the same option and if I were to use it their would be no diffrence. Better to use the option if you can for a 2 channel dedicated music system and the rest for HT

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post #5 of 108 Old 09-24-2009, 10:13 PM
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Quote:
Originally Posted by Tir_McDohl View Post

I Recently purchased a STRDA5400ES Sony receiver and a set of PSB ALpha T1 tower speakers. I noticed that the receiver offers a "Bi-amp" option, I realize that there are a lot of threads with people saying "don't bother". So my question is, what is the point of having the "bi-amp" feature on the reciever and should I use it? (I am currently using it and thought I could hear a difference, but to be fair, it could just be in my head)

Thanks in advance

The main factor limiting the effectiveness of biamping is that the receiver has a shared power supply.

If you look at a benchmark in a receiver review you will see how power drops off as you drive more channnels. So the additional power you get by using two vs one amp per speaker is offset by the additional load on the receiver.

That being said, there might be cases where it could help a bit such as when playing a stereo signal. In this case, your power could be limited by power supply rail voltage. You can't amplify the signal to more than the rail voltage. If that's the reason two channel power is limited, the two amps could help a bit I guess - it's all speculation on my end.

My receiver's rail voltage is very high, and I would guess the limiting factor is always the power supply.

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post #6 of 108 Old 12-19-2011, 09:08 AM
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I know this thread is old, but questions still linger. I have a Denon 1712 that you can set to assign the back surround channel to bi-amp the front speakers. Denon says that:

" The Denon AVR-1712 is equipped with a power amplifier (90W x 7Ch )that reproduces high-fidelity sound in surround mode with equal quality and power for all channels, true to the original sound. The power amplifier circuit adopts a discrete-circuit configuration that achieves high-quality surround sound reproduction. To faithfully reproduce the original surround sound, each of the Denon AVR-1712's seven channels are equipped with its own high-current power amp of equal power (90-watts)"

Is this true bi-amping, or still the passive kind that is unlikely to produce any discernible benefit?
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post #7 of 108 Old 12-19-2011, 09:15 AM
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^^
Still only "passive" bi-amping as is the case with every AVR with this feature (ie. no discernable benefit).

To learn more about your new 1712, join us in the Denon XX12 Owner's thread linked in my sig ... especially noting post #3.

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post #8 of 108 Old 12-19-2011, 10:04 AM
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Thanks, I'll go over there and browse and participate.
I guess if the Denon's do have discrete amps inside for each channel, I'm still confused on how that differs from having discrete amps in different boxes.
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post #9 of 108 Old 12-19-2011, 10:09 AM
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^^
An AVR's amps are drawing from the same single power supply.

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post #10 of 108 Old 12-19-2011, 10:17 AM
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Quote:
Originally Posted by hippiedave View Post

Thanks, I'll go over there and browse and participate.
I guess if the Denon's do have discrete amps inside for each channel, I'm still confused on how that differs from having discrete amps in different boxes.

Not 100% sure I understand your confusion. I will try to answer what I think you may be asking.

You may be thinking that each amp is fully independent. The amps are dependent on a shared power supply.

Power is likely limited by the power supply being unable to keep up under heavy load. In this case the voltage it normally supplies may sag and clipping will occur. Another possibility is that the receiver's protective circuits may limit voltage in an attempt to protect itself. In either case, having more amplifiers for a speaker seem unlikely to help.

If the biamping was active, that could help limit peak voltage, because the peak signal is lowered for the low/high signal by filtering the total signal into a low and high signal (I mean a signal with the low freqs and another with the high freqs.) It's hard to explain, but with active biamping, by splitting the signal up like that, you reduce the voltage of the two resulting signals you get from filtering and thus reducing the onset of clipping.

So when you passively biamp, you are probably not adding power, because total power is likely limited by other factors. And you are feeding the two amps involved with identical signals...the only difference is that you spread the load to two amps. But one is likely working much harder, because the high frequency side of the biamp almost certainly needs significantly less power. But the total power needed has not changed as far as I can tell.

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post #11 of 108 Old 12-19-2011, 12:48 PM
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The difference when passively biamping *and* the power supply's output is peaking is that the distortion usually only goes to the woofer, reducing its audibility - this part seems to almost always be missed. A path to the details:

http://www.avsforum.com/avs-vb/showthread.php?t=1369008

and a little further discussion:

http://www.avsforum.com/avs-vb/showthread.php?t=1375954

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post #12 of 108 Old 12-19-2011, 04:02 PM
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Quote:
Originally Posted by Nick @ Anthem View Post

The difference when passively biamping *and* the power supply's output is peaking is that the distortion usually only goes to the woofer, reducing its audibility - this part seems to almost always be missed. A path to the details:

http://www.avsforum.com/avs-vb/showthread.php?t=1369008

and a little further discussion:

http://www.avsforum.com/avs-vb/showthread.php?t=1375954

I can see why that could be the case. Your post is the first I have seen that suggests this possibility, which is why I did not mention it in my post.

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post #13 of 108 Old 12-19-2011, 04:52 PM
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Quote:
Originally Posted by hippiedave View Post

I know this thread is old, but questions still linger. I have a Denon 1712 that you can set to assign the back surround channel to bi-amp the front speakers. Denon says that:

" The Denon AVR-1712 is equipped with a power amplifier (90W x 7Ch )that reproduces high-fidelity sound in surround mode with equal quality and power for all channels, true to the original sound. The power amplifier circuit adopts a discrete-circuit configuration that achieves high-quality surround sound reproduction. To faithfully reproduce the original surround sound, each of the Denon AVR-1712's seven channels are equipped with its own high-current power amp of equal power (90-watts)"

Is this true bi-amping, or still the passive kind that is unlikely to produce any discernible benefit?

Read the forums and varuous posts..
Bi-Amping is a useless feature with an AVR...
If one has a sophisticated high resolution loudspeaker system with high quality transducers than maybe...
There could be an audible difference with the system being bi-amped or even tri-amped.. Once the levels & x-over points & slopes are optimized, but this is far beyond the normal surround system listener...

Since the choice of loudspeakers is so crucial to the final sonic delivery...
It is recommended to the listener time is better to spent, getting the best loudspeaker within their budget rather than jacking around with Bi-Amping...

Just my $0.02..
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post #14 of 108 Old 12-19-2011, 08:13 PM
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Repeating a myth on a forum 10,000 times doesn't change it into truth.

Nearly all forum talk about biamping, in the context of passively biampable home speakers and otherwise unused amp channels, is just plain incorrect and confused with other biamping applications not typically found in the home. I often wonder how many of the people who talk about it tried it, and of the few who say they did, how many pushed their system to the limit where biamping, even passive, can make a difference.

The most basic understanding of Ohm's Law is required but if you follow my linked posts all the way back to the first one, it's all explained in lay terms. By the end of that discussion most posters including those bashing passive biamping as a waste of the amp's energy, including one who built his own actively biamped speakers, finally got it.

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post #15 of 108 Old 12-19-2011, 08:18 PM
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It's not trivial to push the system just hard enough to know where the difference between biamp and non biamp mode, while measuring the SPL in both cases to compare them.

But I have often suggested to people to try it, when they ask about it. Speaker cable is cheap (unless you feel the need to spend more money than needed on it.) I agree with you 100% there.

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post #16 of 108 Old 12-19-2011, 08:28 PM
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Quote:
Originally Posted by Nick @ Anthem View Post

Repeating a myth on a forum 10,000 times doesn't change it into truth.

Nearly all forum talk about biamping, in the context of passively biampable home speakers and otherwise unused amp channels, is just plain incorrect and confused with other biamping applications not typically found in the home. I often wonder how many of the people who talk about it tried it, and of the few who say they did, how many pushed their system to the limit where biamping, even passive, can make a difference.

The most basic understanding of Ohm's Law is required but if you follow my linked posts all the way back to the first one, it's all explained in lay terms. By the end of that discussion most posters including those bashing passive biamping as a waste of the amp's energy, including one who built his own actively biamped speakers, finally got it.

Thats why we have open discussions in the forum..
State your opinions, others can try it and if they conclude its better it will be posted as being better....
But as Pappy always said..
Wire it up and take a listen...
If it sounds better to you then it is better..


Just my $0.02..
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post #17 of 108 Old 12-19-2011, 09:15 PM
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Quote:
Originally Posted by MichaelJHuman View Post

It's not trivial to push the system just hard enough to know where the difference between biamp and non biamp mode, while measuring the SPL in both cases to compare them.

True, and the hardest part is performing a blind A/B comparison where the two can be compared within five seconds, all else being equal (not that it's overly complicated - think break-before-make relays with adequate current capacity, also useful for amp comparisons where two amps are connected to one speaker). Apart from that only ears are needed to determine whether a difference in the amount of distortion is audible. The volume control would not change position - the point is to compare the difference in sound when the woofer is using a different amplifier, isolating its distortion when things get loud.

In general, trying to match levels using an SPL meter is tricky unless the signal is a steady sine wave, because for a proper listening comparison levels must be matched within 0.1 dB or the louder one will likely be perceived as sounding better (only 0.2 to 0.3 dB increase is needed for that to happen).

But why worry about all that when all it takes, when there are spare amp channels and the speakers are biampable, is adding some speaker cable?

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post #18 of 108 Old 12-19-2011, 10:04 PM
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Quote:
Originally Posted by M Code View Post

Thats why we have open discussions in the forum..
State your opinions, others can try it and if they conclude its better it will be posted as being better....
But as Pappy always said..
Wire it up and take a listen...
If it sounds better to you then it is better..


Just my $0.02..

On the other hand, your previous post is a blanket statement calling biamping a useless feature in an AVR, and someone ought to tell Pappy about blind testing.

This is most certainly not a matter of opinion: When one amp channel powers the woofer while another powers the other drivers, the possibility of harmonic distortion being carried into the upper frequency drivers is eliminated when the distortion is generated as a result of low frequencies being played too loudly.

No need to belabor it, the rest is all in the old posts I linked.

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post #19 of 108 Old 12-19-2011, 10:16 PM
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Quote:
Originally Posted by Nick @ Anthem View Post

On the other hand, your previous post is a blanket statement calling biamping a useless feature in an AVR, and someone ought to tell Pappy about blind testing.

This is most certainly not a matter of opinion: When one amp channel powers the woofer while another powers the other drivers, the possibility of harmonic distortion being carried into the upper frequency drivers is eliminated when the distortion is generated as a result of low frequencies being played too loudly.

No need to belabor it, the rest is all in the old posts I linked.

Applies to a minority audience...
92% of the home theater systems in North America use subwoofer/satellite loudspeaker systems, which have powered subwoofers..
Besides the power supplies & amplifiers within the majority of AVRs sold today lack enough voltage/current capability to drive a woofer adequately..

Just my $0.02..
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post #20 of 108 Old 12-19-2011, 11:04 PM
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Quote:
Originally Posted by M Code View Post

Applies to a minority audience...
92% of the home theater systems in North America use subwoofer/satellite loudspeaker systems, which have powered subwoofers..
Besides the power supplies & amplifiers within the majority of AVRs sold today lack enough voltage/current capability to drive a woofer adequately..

Just my $0.02..

The first part of that reply changes nothing in relation to the original questions and my answers to them, and the last part supports biamping regardless.

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post #21 of 108 Old 12-20-2011, 05:38 AM
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A different viewpoint:

If you have two unused channels on your AVR or amplifier, and have the capability to bi-amp (with the speakers and amp), then there is little reason not to. I personally think there is some technical merit to doing so. It is arguable when and under what conditions this might become audibly beneficial, however, I have not heard an argument against doing this if all it's going to cost you is some time and speaker wire.
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post #22 of 108 Old 12-20-2011, 06:03 AM
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Quote:
Originally Posted by Nick @ Anthem View Post

Repeating a myth on a forum 10,000 times doesn't change it into truth.

Nearly all forum talk about biamping, in the context of passively biampable home speakers and otherwise unused amp channels, is just plain incorrect and confused with other biamping applications not typically found in the home. I often wonder how many of the people who talk about it tried it, and of the few who say they did, how many pushed their system to the limit where biamping, even passive, can make a difference.

The most basic understanding of Ohm's Law is required but if you follow my linked posts all the way back to the first one, it's all explained in lay terms. By the end of that discussion most posters including those bashing passive biamping as a waste of the amp's energy, including one who built his own actively biamped speakers, finally got it.



I have tried passive bi-amping, and it does work. You will not notice the difference in sound until you push the volume up to be loud enough to matter. The non bi-amped setup just runs out of power at a lower volume level.

However, most people do not have speakers that will benefit from bi-amping. If the amplifier has enough current capability to drive the speaker, then more current capability via bi-amping will not make much or any diference.

In general a 2-way speaker does not need to be bi-amped. In my specific case, my speakers were 4-way speakers. The bi-amp terminals seperated the woofer from the 3-way upper drivers at 100 Hz. The bi-amped setup can play much louder than the straight setup.

The same speaker driven by a higher power single outboard amplifier will also work well at an extra cost.
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post #23 of 108 Old 12-20-2011, 06:05 AM
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Quote:
Originally Posted by leger433 View Post

A different viewpoint:

If you have two unused channels on your AVR or amplifier, and have the capability to bi-amp (with the speakers and amp), then there is little reason not to. I personally think there is some technical merit to doing so. It is arguable when and under what conditions this might become audibly beneficial, however, I have not heard an argument against doing this if all it's going to cost you is some time and speaker wire.


That depends on the speaker in question. Most 2-way speakers will not sound different being bi-amped.
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post #24 of 108 Old 12-20-2011, 06:26 AM
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Biamping even 2-way speakers has its benefits. In my older posts I mentioned that if an amp channel only has to drive a tweeter it is less likely that the tweeter will see extraneous high frequencies arising from clipping, a.k.a. harmonic distortion. The number one tweeter killer is an underpowered overdriven amp therefore biamping can be a tweeter saver if nothing else. This includes passive biamping.

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post #25 of 108 Old 12-20-2011, 06:52 AM
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Quote:
Originally Posted by leger433 View Post

A different viewpoint:

If you have two unused channels on your AVR or amplifier, and have the capability to bi-amp (with the speakers and amp), then there is little reason not to.

It's the exact viewpoint that a few of us have been expressing all along, and with it its corollary that if the system is still in the planning phase and equipment has not been purchased yet, get the right-sized amp for the speaker instead of thinking about biamping. Discussion exists only because there's always someone who quickly interjects with a technically misinformed argument against passive biamping.

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post #26 of 108 Old 12-20-2011, 09:13 AM
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I think we covered bi-amping pretty well in this thread. Bi-wiring seems silly to me, so I think the case may be closed on that one.

But what about bi-curious-amping?

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post #27 of 108 Old 12-20-2011, 11:47 AM
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Quote:
Originally Posted by Nick @ Anthem View Post

In my older posts I mentioned that if an amp channel only has to drive a tweeter it is less likely that the tweeter will see extraneous high frequencies arising from clipping, a.k.a. harmonic distortion. The number one tweeter killer is an underpowered overdriven amp therefore biamping can be a tweeter saver if nothing else. This includes passive biamping.

I don't get that logic, in passive bi-amping the amps are sending the full signal to both sides, the speakers' crossover then has to filter out the unwanted frequencies, my understanding is that this process doesn't do much to reduce the "amp load" per se. I don't know that for sure, but what happens to the bass frequencies once they're "blocked" by the x-over and what is that effect on the amps' load? Does impedance change when you passively bi-amp? I don't think so but again not sure.

Now, it is logical to me that active bi-amping, where the crossover is done before the amplification can accomplish what you're suggesting.

From a practical experience, I've never tried active bi-amping, but I've tried passive bi-amping a variety of ways with a variety of different amps and have yet to experience a difference worth the effort or cost of the extra wiring.
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post #28 of 108 Old 12-20-2011, 12:04 PM
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Quote:
Originally Posted by rnrgagne View Post

I don't get that logic, in passive bi-amping the amps are sending the full signal to both sides, the speakers' crossover then has to filter out the unwanted frequencies, my understanding is that this process doesn't do much to reduce the "amp load" per se. I don't know that for sure, but what happens to the bass frequencies once they're "blocked" by the x-over and what is that effect on the amps' load? Does impedance change when you passively bi-amp? I don't think so but again not sure.

Now, it is logical to me that active bi-amping, where the crossover is done before the amplification can accomplish what you're suggesting.

From a practical experience, I've never tried active bi-amping, but I've tried passive bi-amping a variety of ways with a variety of different amps and have yet to experience a difference worth the effort or cost of the extra wiring.

FWIW, as I understand it because the impedance of the crossover is very high once you get far past the crossover point, the amp (of course) continues to develop the voltage called for by the input signal, but essentially sends zero amps outside the passband. So it can reduce power requirements, at least a little. From a pure power perspective, AFAIK, the issue is that typical speaker crossovers (to the tweeter) are high enough that the power requirements of real program material to the tweeter are far less than the requirements for the sub. So when the woofer amp is putting out 200 watts, the tweeter amp may be putting out 25 watts, even though the full range signal is theoretically present at the amp's output terminals.

I find interesting and at least on its face reasonable the idea that you essentially scrape off the higher frequency distortion, rendering less unpleasant an overdriven amp. Since I'm pretty sure peaks at my typical listening levels (seldom higher than -15 from reference) call for less than 20 watts per channel, it's of only academic interest to me. I will, of course, defend vigorously (if perhaps not to the death) the right of others to have systems and listen at levels that require a bunch more power . . .
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post #29 of 108 Old 12-20-2011, 12:18 PM
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So here is my question, if passive biamping helps the tweeter not get distortion from the woofer that would still mean the woofer is still not getting enough power after you biamp. Wouldn't you want an amp that has enough power for the woofer as well? I would think that if passive biamping give you an improvement that would mean that the receiver doesn't have enough power for you speakers and since the tweeter doesn't use that much power you would still not have enough power after you biamp. It just wouldn't affect the sound as much because the tweeter is not getting the distortion but you would know that the woofer is still getting it. Is this correct?



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post #30 of 108 Old 12-20-2011, 12:40 PM
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Quote:
Originally Posted by mjpearce023 View Post

So here is my question, if passive biamping helps the tweeter not get distortion from the woofer that would still mean the woofer is still not getting enough power after you biamp. Wouldn't you want an amp that has enough power for the woofer as well? I would think that if passive biamping give you an improvement that would mean that the receiver doesn’t have enough power for you speakers and since the tweeter doesn’t use that much power you would still not have enough power after you biamp. It just wouldn't affect the sound as much because the tweeter is not getting the distortion but you would know that the woofer is still getting it. Is this correct?

Your points seem reasonable to me.

I am guessing (emphasis on guessing,) that our ears would probably most notice distortion in the higher frequencies. If I am correct, that we would not be as sensitive to the distortion that would be occuring due to some specific instant in time where a signal (or signals) are causing one or more channels to clip. If, by bi-amping a channel, distortion to the high freq side is being reduced, I can follow the argument that bi-amping would help.

I would think all channels are voltage starved during clipping because I would guess clipping in AVRs usually occurs due to limiter circuits reducing the voltage to multiple amps or the power supply's voltage collapses. I still can't quite visualize how the amp handling the high freq (in a biamp arrangement,) is not being voltage starved. Also, in AVRs, you can only bi-amp the left/right channel. During a high peak signal instance, one would guess all channels are being heavily utilized if a movie is playing. And I would have guessed all the channels are clipping or close to clipping.

I would think it's pretty hard to specifically know any random receiver is going to behave in the real world situation, with 5 or more amplifiers being involved, along with limiter circuitry, which may not work the same on every receiver and in conjunction with 5 or more speakers reactively interacting with the amplifiers.

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