Trying to bi amp front speakers without giving up rear surrounds - AVS Forum
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post #1 of 36 Old 03-31-2012, 07:16 PM - Thread Starter
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I have a 9.2 setup with an Onkyo PR-SC5507 prepro. I would like to bi amp my front speakers as I have spare amps. According to the service manual, I have to give up my rear surrounds in order to bi amp.

Is it possible or beneficial to use a Y balanced XLR cable to split the front signals from the prepro so that each front pre out signal goes to 2 different amps, which in turn will supply a woofer and a tweeter with its own amp?

Or if it is not a good idea to split the front XLR inputs, could I use the front RCA preout for the woofer and the balanced front preout for the tweeter?

I emailed onkyo support who responded as follows but gave no explanation :

We do not recommend that you use any splitters, so the only way possible is as it states in the owner's manual on page 21 that when bi-amping, the AV controller is able to feed up to 7.2 speakers ONLY. (PLEASE SEE BELOW INFORMATION).


From the manual :


The FRONT L/R and SURR BACK L/R outputs can be used with front speakers and surround back speakers, respectively,
or bi-amped to provide separate tweeter and woofer feeds for a pair of front speakers that support bi-amping,
providing improved bass and treble performance.
When bi-amping is used, the AV controller is able to feed up to 7.2 speakers in the main room.
For bi-amping, the FRONT L/R outputs feed the front speakers' woofer terminals. And the SURR BACK L/R
outputs feed the front speakers' tweeter terminals.
Once you've completed the bi-amping connections shown below and turned on the AV controller, you must set
the Speakers Type(Front) setting to Bi-Amp to enable bi-amping (see page 53).
Important:
When making the bi-amping connections, be sure to remove the jumper bars that link the speakers'
tweeter (high) and woofer (low) terminals.
Bi-amping can only be used with speakers that support bi-amping. Refer to your speaker manual.
See your multichannel power amplifier's instruction manual for more information on connecting speakers.
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post #2 of 36 Old 03-31-2012, 07:50 PM
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This kind of bi-amping won't gain you anything, and has no benefit to the overall system's performance. The splitter won't help either, and may introduce lots of noise. In other words, I both agree with Onkyo, and I'm telling you this is not worth the time to configure - leave things as they are now.
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post #3 of 36 Old 03-31-2012, 08:39 PM - Thread Starter
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Thanks for the quick response. Could you explain why splitting the preout signal does not work? Or why using the signal from the RCA preout would not work?
I do understand that biamping will only give a small benefit if done the way the manual states and hoped I could duplicate the small benefit while keeping the rear surrounds.
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post #4 of 36 Old 03-31-2012, 08:41 PM
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There is no benefit, neither small nor large. You aren't running a crossover, so all you're going to do is generate two signals at say 100wpc and send both into the speaker, and make the speaker's crossover sink all of the wasted power into it's split HPF/LPF scheme. That's not worth the hassle.

As far as the splitter thing, you'll probably just introduce a lot of noise, and the device may not like having XLR and RCA driving at once (it may short or something else, I don't know) - it'd be nice of Onkyo had explained if it at least *could* run XLR and RCA at once. In theory you could go dual RCA out, but again, it doesn't do anything for you, so it's not worth the hassle of setting up, and the risk of noise.
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post #5 of 36 Old 03-31-2012, 09:07 PM - Thread Starter
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Wonder why the speaker companies put separate terminals on the speaker for biamping?

I have no desire to open up the speaker to alter the crossover.
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post #6 of 36 Old 03-31-2012, 09:13 PM
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Quote:
Originally Posted by bluejayht View Post

Wonder why the speaker companies put separate terminals on the speaker for biamping?

Give the customer what they want. It helps sell units.

There is absolutely no technical benefit.

http://sound.westhost.com/bi-amp.htm
http://www.roger-russell.com/wire/wire.htm#cardas

To properly bi-amp your speakers you'd have to remove the crossovers entirely, and put a crossover between the SSP's outputs and the amplifier's inputs - so that you're amplifying the pass-band on either side, which gives you additional headroom and so on. Figuring out the ideal xover point will require measurement.
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post #7 of 36 Old 04-01-2012, 05:41 AM
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The Onkyo people are talking about the case where one would be using the INTERNAL amplifiers of an Onkyo RECEIVER for bi-amping. If you use the rear surround amps of an Onkyo RECEIVER to bi-amp the front, they obviously are not available for the rear surrounds anymore. They are obviously NOT on the same page as you are...lol (they must think you have a 5007 receiver...).

They must have mistakenly stuck in part of some boilerplate info intended for a 5007 receiver by mistake, since they talk about connecting the outputs directly to the speaker terminals. That makes NO sense at all...duhhh. Page 21 in your manual is stupid and confused; makes no sense. Ignore it.

Since you are talking about using separate EXTERNAL amplifiers for the fronts, there is no reason to lose anything. You can just use a balanced Y connector to go to both external amplifiers for the front; no problem. This is invisible to the 5507; it doesn't know you are splitting that output, and it doesn't care. The input load impedance of the two amplifiers in parallel will be lower, but it should not be low enough to be an issue if each power amplifier has an input impedance of at least 10K ohms.

When bi-amping, you should use one stereo amplifier for the left speaker and use one channel for the LF speaker section and one channel for the HF speaker section.

The other stereo amplifier should be used for both sections of the other speaker.




Quote:
Originally Posted by bluejayht View Post

I have a 9.2 setup with an Onkyo PR-SC5507 prepro. I would like to bi amp my front speakers as I have spare amps. According to the service manual, I have to give up my rear surrounds in order to bi amp.

Is it possible or beneficial to use a Y balanced XLR cable to split the front signals from the prepro so that each front pre out signal goes to 2 different amps, which in turn will supply a woofer and a tweeter with its own amp?

Or if it is not a good idea to split the front XLR inputs, could I use the front RCA preout for the woofer and the balanced front preout for the tweeter?

I emailed onkyo support who responded as follows but gave no explanation :

We do not recommend that you use any splitters, so the only way possible is as it states in the owner's manual on page 21 that when bi-amping, the AV controller is able to feed up to 7.2 speakers ONLY. (PLEASE SEE BELOW INFORMATION).


From the manual :


The FRONT L/R and SURR BACK L/R outputs can be used with front speakers and surround back speakers, respectively,
or bi-amped to provide separate tweeter and woofer feeds for a pair of front speakers that support bi-amping,
providing improved bass and treble performance.
• When bi-amping is used, the AV controller is able to feed up to 7.2 speakers in the main room.
• For bi-amping, the FRONT L/R outputs feed the front speakers’ woofer terminals. And the SURR BACK L/R
outputs feed the front speakers’ tweeter terminals.
• Once you’ve completed the bi-amping connections shown below and turned on the AV controller, you must set
the “Speakers Type(Front)” setting to “Bi-Amp” to enable bi-amping (see page 53).
Important:
• When making the bi-amping connections, be sure to remove the jumper bars that link the speakers’
tweeter (high) and woofer (low) terminals.
• Bi-amping can only be used with speakers that support bi-amping. Refer to your speaker manual.
See your multichannel power amplifier’s instruction manual for more information on connecting speakers.

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post #8 of 36 Old 04-01-2012, 10:30 AM
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Quote:
Originally Posted by walbert View Post

Give the customer what they want. It helps sell units.

Agreed in general, especially the part about not doing any good.

IME the manufacturer probably thought that the extra terminals would be used for biwiring, which has the benefit as not being as technically worthless as biamping. Biwiring may also have a reduced possibility of actually making things worse. Not only is biamping speakers that were not designed for it a bad idea, its an expensive idea.

Some dealers put pressure on manufacturers to add provisions for biwiring so that they can sell twice as much speaker wire.

There is absolutely no technical benefit to biwiring, and biamping can easily destroy the speaker's balance between highs and lows.

Quote:


http://sound.westhost.com/bi-amp.htm
http://www.roger-russell.com/wire/wire.htm#cardas

To properly bi-amp your speakers you'd have to remove the crossovers entirely, and put a crossover between the SSP's outputs and the amplifier's inputs - so that you're amplifying the pass-band on either side, which gives you additional headroom and so on. Figuring out the ideal xover point will require measurement.

The idea that a typical system owner could accomplish all of the required technical steps to not trash the speaker's sound with biamping is a giant flight of fancy. To further expect that the speaker's sound would be improved, is darn near impossible.

Biamping is likely to change the speaker's sound, so that audiophiles who perceive any change as an improvement (after all it represents their expertise!) will react favorably.
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post #9 of 36 Old 04-01-2012, 10:48 AM - Thread Starter
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Quote:
Originally Posted by commsysman View Post


Since you are talking about using separate EXTERNAL amplifiers for the fronts, there is no reason to lose anything. You can just use a balanced Y connector to go to both external amplifiers for the front; no problem. This is invisible to the 5507; it doesn't know you are splitting that output, and it doesn't care. The input load impedance of the two amplifiers in parallel will be lower, but it should not be low enough to be an issue if each power amplifier has an input impedance of at least 10K ohms.

When bi-amping, you should use one stereo amplifier for the left speaker and use one channel for the LF speaker section and one channel for the HF speaker section.

The other stereo amplifier should be used for both sections of the other speaker.

I appreciate your input, but I am not sure what you meant commsysman. I wanted to use a separate amp for the signal to the high pass and a separate amp to the low pass section of each front speaker. That is, 6 separate amps for the front 3 speakers. I have a single amp for each of the side surrounds , rear surrounds, and front height speakers. A total of 12 amps for the 9.2, not including the subwoofer amps.
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post #10 of 36 Old 04-01-2012, 04:11 PM
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Quote:
Originally Posted by arnyk View Post

The idea that a typical system owner could accomplish all of the required technical steps to not trash the speaker's sound with biamping is a giant flight of fancy. To further expect that the speaker's sound would be improved, is darn near impossible.

Okay, that's a very fair criticism. My assumption was that if someone was serious enough about doing this, they'd probably do all their homework, and either design a new set of speakers to work on this principle, or figure out how to make it work properly otherwise (of course, I'd like to believe that the manufacturer has done all of this during R&D and simply replicated their results in a fixed circuit and put that in the box for us).

And I'm in full agreement regarding the skepticism of sound quality improvements - headroom is really the only advantage I've ever seen documented or defended consistently (Even from the flat-earth crowd that wants to do things like the OP proposed).
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post #11 of 36 Old 04-01-2012, 09:31 PM - Thread Starter
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Quote:
Originally Posted by walbert View Post

Okay, that's a very fair criticism. My assumption was that if someone was serious enough about doing this, they'd probably do all their homework, and either design a new set of speakers to work on this principle, or figure out how to make it work properly otherwise (of course, I'd like to believe that the manufacturer has done all of this during R&D and simply replicated their results in a fixed circuit and put that in the box for us).

And I'm in full agreement regarding the skepticism of sound quality improvements - headroom is really the only advantage I've ever seen documented or defended consistently (Even from the flat-earth crowd that wants to do things like the OP proposed).

Walbert, thanks for your reply. Since I had spare amps and had prewired my HT with extra speaker wires and owned speakers with separate terminals, biamping was really considered to provide a little extra headroom at no additional expense at this point. But I did not want to give up my rear surrounds for a "potentially small" benefit, so I thought I could split signals. If the speakers internal crossover really prevents any benefit whether biamping is done onkyo's way or by splitting the signals, then I will probably leave my extra amps unused.
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post #12 of 36 Old 04-02-2012, 06:06 AM
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Quote:
Originally Posted by bluejayht View Post

Walbert, thanks for your reply. Since I had spare amps and had prewired my HT with extra speaker wires and owned speakers with separate terminals, biamping was really considered to provide a little extra headroom at no additional expense at this point. But I did not want to give up my rear surrounds for a "potentially small" benefit, so I thought I could split signals. If the speakers internal crossover really prevents any benefit whether biamping is done onkyo's way or by splitting the signals, then I will probably leave my extra amps unused.

Hold that thought! ;-)

The benefit of biamping speakers with internal crossovers is not only close to zero, but you can easily make small adjustment errors and make things worse.
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post #13 of 36 Old 04-02-2012, 10:09 AM
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Quote:
Originally Posted by arnyk View Post

There is absolutely no technical benefit to biwiring, and biamping can easily destroy the speaker's balance between highs and lows.

Yes, but to be clear, bi-amping when done properly is indeed worthwhile. But you need speakers that can do this correctly, and you need measuring software to set up the active crossover properly.

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post #14 of 36 Old 04-02-2012, 10:45 AM
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Quote:
Originally Posted by walbert View Post

This kind of bi-amping won't gain you anything, and has no benefit to the overall system's performance.

Quote:
Originally Posted by walbert View Post

There is no benefit, neither small nor large.

Quote:
Originally Posted by walbert View Post

There is absolutely no technical benefit.

The original poster did not ask anything about the benefits (or lack of benefits) that might be afforded by passively biamping his speakers.

And I would recommend these threads for some interesting discussion regarding passive biamping and its possible benefit paying particular attention to the posts by 'Nick @ Anthem':

http://www.avsforum.com/avs-vb/showp...38&postcount=3

http://www.avsforum.com/avs-vb/showt...6#post21370316

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

And before anyone raises the criticism that he works for Anthem, and his only goal is to sell more amps, I would ask you to pay attention to what he is saying. He's not making a sales pitch.



Quote:
Originally Posted by walbert View Post

The splitter won't help either, and may introduce lots of noise.

Quote:
Originally Posted by walbert View Post

As far as the splitter thing, you'll probably just introduce a lot of noise, and the device may not like having XLR and RCA driving at once (it may short or something else, I don't know) - it'd be nice of Onkyo had explained if it at least *could* run XLR and RCA at once. In theory you could go dual RCA out, but again, it doesn't do anything for you, so it's not worth the hassle of setting up, and the risk of noise.

I don't know about using the RCA out and XLR out, simultaneously, but splitting one or the other to allow for passive biamping should not introduce any "noise".


Quote:
Originally Posted by walbert View Post

To properly bi-amp your speakers you'd have to remove the crossovers entirely, and put a crossover between the SSP's outputs and the amplifier's inputs - so that you're amplifying the pass-band on either side, which gives you additional headroom and so on. Figuring out the ideal xover point will require measurement.

As already discussed in the thread, the idea that ripping the crossovers out of a perfectly good and (supposedly) well-engineered speaker is some sort of alternative to passive biamping is quite overly optimistic. The chances of most users being able to successfully do this with a consumer-level speaker and achieve results that are better than what the speakers would have otherwise been capable of on their own, with their own, already matched crossovers, is pretty slim.

"All men are frauds. The only difference between them is that some admit it. I myself deny it."
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post #15 of 36 Old 04-02-2012, 10:51 AM
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Quote:
Originally Posted by commsysman View Post

The Onkyo people are talking about the case where one would be using the INTERNAL amplifiers of an Onkyo RECEIVER for bi-amping. If you use the rear surround amps of an Onkyo RECEIVER to bi-amp the front, they obviously are not available for the rear surrounds anymore. They are obviously NOT on the same page as you are...lol (they must think you have a 5007 receiver...).

They must have mistakenly stuck in part of some boilerplate info intended for a 5007 receiver by mistake, since they talk about connecting the outputs directly to the speaker terminals. That makes NO sense at all...duhhh. Page 21 in your manual is stupid and confused; makes no sense. Ignore it.

Since you are talking about using separate EXTERNAL amplifiers for the fronts, there is no reason to lose anything. You can just use a balanced Y connector to go to both external amplifiers for the front; no problem. This is invisible to the 5507; it doesn't know you are splitting that output, and it doesn't care. The input load impedance of the two amplifiers in parallel will be lower, but it should not be low enough to be an issue if each power amplifier has an input impedance of at least 10K ohms.

Stop the presses! I agree with commsysman!

Having a specific biamping setting with a receiver makes sense as this reassigns the amplifier duties. But a pre/pro with this setting doesn't really make a whole lot of sense. Using splitters and external amps, you can passively biamp any channel you desire.


Quote:
Originally Posted by commsysman View Post

When bi-amping, you should use one stereo amplifier for the left speaker and use one channel for the LF speaker section and one channel for the HF speaker section.

The other stereo amplifier should be used for both sections of the other speaker.

Quote:
Originally Posted by bluejayht View Post

I appreciate your input, but I am not sure what you meant commsysman. I wanted to use a separate amp for the signal to the high pass and a separate amp to the low pass section of each front speaker. That is, 6 separate amps for the front 3 speakers. I have a single amp for each of the side surrounds , rear surrounds, and front height speakers. A total of 12 amps for the 9.2, not including the subwoofer amps.

He was describing using stereo amps as opposed to the monoblock amps that it seems you would be using.

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post #16 of 36 Old 04-02-2012, 10:56 AM
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Quote:
Originally Posted by arnyk View Post

.............and biamping can easily destroy the speaker's balance between highs and lows.

Biamping is likely to change the speaker's sound........

"Passive" biamping with identical amplifiers, though, (regardless of whether one deems it to be beneficial or not) will not alter a speaker's characteristic sound.

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Do you need more power, or are you expecting better SQ?
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post #18 of 36 Old 04-02-2012, 02:02 PM
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Miles, I'm going to have to disagree with you, and the Anthem salesman. What really killed it for me was his instence that "only a pair of ears is needed to hear the difference" - poppycock. When you track the source of the entire "support for passive bi-amping" argument back you arrive at Anthem's doorstep, where they'd be happy to sell you an amplifier. In the final thread you linked, note FOH and penngray's replies which absolutely get into the issue (or read the Rod Elliot article I linked). Kal sums it up quite nicely:
http://www.avsforum.com/avs-vb/showp...5&postcount=36

I also disagree with the "it's too complicated so it's not an option" argument - I agree with Arny, it *is* complicated, but if you really want to climb the mountain, you can climb the mountain.

Bottom line is, there's minimal (if any) gains to be had here, the potential for power loss (which can be simply figured if we had more information; hand waving doesn't do it, and I'm not interested in measuring anything), and a lot of wasted time.
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post #19 of 36 Old 04-02-2012, 03:19 PM
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Quote:
Originally Posted by walbert View Post

Miles, I'm going to have to disagree with you, and the Anthem salesman. What really killed it for me was his instence that "only a pair of ears is needed to hear the difference" - poppycock. When you track the source of the entire "support for passive bi-amping" argument back you arrive at Anthem's doorstep, where they'd be happy to sell you an amplifier.

He claims that when pushed to the point of distortion you can hear the difference that passive biamping affords. I can't say from personal experience whether you can or not and I won't be trying it, either.

But his "argument" in favor of passive biamping as a way to protect the tweeter from the distortion that develops in the amplifier driving the woofer when pushing things so hard does make some sense to me.

So, I think it might be a reasonable endeavor for someone who already has either the extra outboard amps or the unused amps in their AVR and will be pushing things to the limits.

Regarding his selling amplifiers, did you did you miss THIS post?

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post #20 of 36 Old 04-02-2012, 05:25 PM
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Quote:
Originally Posted by sivadselim View Post

He claims that when pushed to the point of distortion you can hear the difference that passive biamping affords. I can't say from personal experience whether you can or not and I won't be trying it, either.

But his "argument" in favor of passive biamping as a way to protect the tweeter from the distortion that develops in the amplifier driving the woofer when pushing things so hard does make some sense to me.

So, I think it might be a reasonable endeavor for someone who already has either the extra outboard amps or the unused amps in their AVR and will be pushing things to the limits.

The argument that you're going to save a tweeter from clipping distortion is dubious at best - remember that your amplifier is still seeing full-range, and will still be pushed to clipping if the pre-amp output is too hot. So if you've got a program that "kills" your setup (let's say Hanna ), instead of having two amplifier channels running into clipping, you've now got four. That's an increased demand on the amplifier power supply (or at least the mains power supply), and you've still got clipped outputs going into your speakers. Having the bars out isn't going to make that go away, and the tweeter is still going to be the first to go (assuming you don't put your AVR/amp into protection). The crossover is going to be sinking all of the stopband energy and expressing it as heat, but you've still got clipping going into the tweeter (and everything else).

If Hanna is already killing your AVR (okay I promise that's the last time I make the joke, that thread title just stuck with me though), asking it to send the same signal out multiple times isn't going to help. It may hurt. If you need more headroom, you need more sensitive speakers, a bigger amplifier, or both.

Anyways, if there was a magical headroom gain, it'd be to the order of 3 dB (if we assume we're just ganging more channels from the same MCH amp/AVR) which is nothing to write home for. If we're getting into audiophile land and talking about "solid state for the lows and tubes for the highs" now you've (very likely) got a level mismatch problem which will influence the overall sound of the system (likely in the negative).

If you have an AVR or MCH amp that can bridge it's outputs, that would be more useful - you'd get a legitimate 3 dB gain, providing more headroom before clipping. Assuming the thing's internal power supply can keep up, of course. I still vote for bigger amplifiers, more sensitive speakers, both, or none of the above (if you really don't need the extra power, it doesn't matter if the amplifier can deliver it).

I'm not sure what that post has to do with him somehow being impartial - he's just supporting the notion of passive bi-amping, which is something that a lot of AVR makers have been beating on for a while because it's an easy feature to implement from the DSP's perspective, and the assumption (I'm guessing) is that the actual power demand will never get into a dangerous situation (and that if it does, the protection circuit kicks in) and it lets customers have another "feel good" to go along with their "buy-wire ready" speakers and overpriced cables.
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post #21 of 36 Old 04-03-2012, 04:40 AM
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Quote:
Originally Posted by sivadselim View Post

He claims that when pushed to the point of distortion you can hear the difference that passive biamping affords. I can't say from personal experience whether you can or not and I won't be trying it, either.

But his "argument" in favor of passive biamping as a way to protect the tweeter from the distortion that develops in the amplifier driving the woofer when pushing things so hard does make some sense to me.

The relevant question at this point is: "what kind of distortion"?

In general the only way to make a modern amp distort audibly is to clip it.

To re-iterate what Walbert said quite correctly above but in different words, since the amp is amplifying the same signal as ever with passive bi-amping, its going to generate most of the same kinds of distortion, and its clipping point isn't going to improve that much. BTW massively changing the signals that the amps amplifiy is the source of the actual benefits that are obtained when speakers are upgraded to active bi-amping with active crossovers, total-re-engineering, no passive crossovers, and all the rest. This is the key point!

It is true that adding a speaker load may increase power amp distoriton from 0.001% to 0.002% or even from 0.01% to 0.02% but that only happens when you are already driving the amp to near clipping. At lower levels we're not even talking those inaudible levels of distortion.

The fact is that a power amp driving a speaker load with music is not working a fraction as hard as it does on a test bench with a resistive or even speaker load, amplifying test signals to near full output. Music is easier to amplify than than full-output test tones because it varies its level so much and because it it not a pure tone. Speaker loads are easier on most parts of a modern power amp than resistive loads, no matter what yu may hear which is based on how amps were 40 years ago. This is clearly observable in real life.

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So, I think it might be a reasonable endeavor for someone who already has either the extra outboard amps or the unused amps in their AVR and will be pushing things to the limits.


The opportunity to unbalance the levels or reverse the phase of the high and low frequency sections of a speaker with passive bi-amplfiication are signficiant. If you hear a difference, its mistakes like those that are the most likely reliable sources of audible differences.

The differences that are alleged to occur by off-loading the bass from the tweeter amplifier are gnerally extremely difficult or impossible to hear.
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post #22 of 36 Old 04-03-2012, 11:19 AM
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Originally Posted by sivadselim View Post

But his "argument" in favor of passive biamping as a way to protect the tweeter from the distortion that develops in the amplifier driving the woofer when pushing things so hard does make some sense to me.

Nope. Both amplifiers are presented the same input signal, have the same gain and the same output. So when clipping occurs, it will occur in the same manner and level in both amplifiers.

Using Rod Elliott's graphics (discussion of one channel, say Left): here you have a 200Hz and 2kHz sine of equal amplitude in an amplifier, just before clipping.



Same signal with an increase in gain driving the amplifier, or both in a passive biamp into clipping. This is the voltage that will be produced at the output of an SS amp, both in this case.



Here is the spectrum of the distortion produced, by both amplifiers.

[Note] because I have used someone else's graphics, ignore the scales are different. Assume the top graphic has a peak of 1, not 2, the same as the second one.



To make the discussion simple, and because I'm not going to make graphics, assume the xover is at 2kHz, a not uncommon frequency for a 2 (or 2.5) way speaker.

In the low pass section that filters for the LF driver, everything above 2kHz will be progressively attenuated by the xover. The LF driver typically has a higher power rating and larger coil so the increase in dissipation should not cause any issues.

In the highpass section that filters for the tweeter, everything below 2khz is progressively attenuated by the xover, but anything above 2kHz is passed pretty much undiminished (attenuation only in the region of the xover). So the distortion produced will still be audible via the tweeter and the increase in dissipation from the extra harmonic and inharmonic distortion produced by the clipping will still be dissipated in the tweeter coil affording it no extra protection in the passive biamp version.

In a single amp (conventional) set up, the same output voltage is produced by the single amplifiers. The same xover is used, so the signal being applied to the HF section is the same, with the same dissipation.
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post #23 of 36 Old 04-03-2012, 11:24 AM
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Originally Posted by arnyk View Post

The relevant question at this point is: "what kind of distortion"?

In general the only way to make a modern amp distort audibly is to clip it.

To re-iterate what Walbert said quite correctly above but in different words, since the amp is amplifying the same signal as ever with passive bi-amping, its going to generate most of the same kinds of distortion, and its clipping point isn't going to improve that much. BTW massively changing the signals that the amps amplifiy is the source of the actual benefits that are obtained when speakers are upgraded to active bi-amping with active crossovers, total-re-engineering, no passive crossovers, and all the rest. This is the key point!

It is true that adding a speaker load may increase power amp distoriton from 0.001% to 0.002% or even from 0.01% to 0.02% but that only happens when you are already driving the amp to near clipping. At lower levels we're not even talking those inaudible levels of distortion.

The fact is that a power amp driving a speaker load with music is not working a fraction as hard as it does on a test bench with a resistive or even speaker load, amplifying test signals to near full output. Music is easier to amplify than than full-output test tones because it varies its level so much and because it it not a pure tone. Speaker loads are easier on most parts of a modern power amp than resistive loads, no matter what yu may hear which is based on how amps were 40 years ago. This is clearly observable in real life.




The opportunity to unbalance the levels or reverse the phase of the high and low frequency sections of a speaker with passive bi-amplfiication are signficiant. If you hear a difference, its mistakes like those that are the most likely reliable sources of audible differences.

The differences that are alleged to occur by off-loading the bass from the tweeter amplifier are gnerally extremely difficult or impossible to hear.


I agree with almost everything you say, and am personally convinced that whatever minor occasional benefit might come from biamping would be better handled by haveing an amp of appropriate power. But just because the amp connected to the tweeter is still swinging the voltage for the lows does not mean it will necessarily, or even likely, clip because of the power in the lows. Once one gets far enough below the crossover point, the tweeter/high pass network looks like a very high resistance to the amp. It delivers, effectively, zero amps at lower frequencies. Otherwise it would throw the tweeter dome across the room.

So if, as may be the case, an amp is distorting because it's running out of current capability, rather than exceeding the voltage swing the transistors can supply, the tweeter amp should stay clean while the woofer amp may distort.

But given the power distribution between tweeter level (let's say 2KHz and up) and mids/woofer, the occasions on which the difference is relevant have to be very few. And at least except for transients that last in the few milliseconds, likely nonexistent for normal folks, and one would think that if youre clipping at 10 dB below the transient levels, you've got a significantly underpowered system (by a factor of ten), and whether simply passively biamping could make a significant sonic difference in that situation is not at all clear to me.
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post #24 of 36 Old 04-03-2012, 11:29 AM
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Well, maybe 'Nick @ Anthem' will stop by and defend the posts in the links I posted. Honestly, I can't. That's not to say he is not right. Only an admission of my relative ignorance, here. But he does address everything that has been said in the last few posts in this thread, in his posts in those threads.

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post #25 of 36 Old 04-03-2012, 11:33 AM
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Originally Posted by JHAz View Post

I agree with almost everything you say, and am personally convinced that whatever minor occasional benefit might come from biamping would be better handled by haveing an amp of appropriate power. But just because the amp connected to the tweeter is still swinging the voltage for the lows does not mean it will necessarily, or even likely, clip because of the power in the lows. Once one gets far enough below the crossover point, the tweeter/high pass network looks like a very high resistance to the amp. It delivers, effectively, zero amps at lower frequencies. Otherwise it would throw the tweeter dome across the room.

So if, as may be the case, an amp is distorting because it's running out of current capability, rather than exceeding the voltage swing the transistors can supply, the tweeter amp should stay clean while the woofer amp may distort.

But given the power distribution between tweeter level (let's say 2KHz and up) and mids/woofer, the occasions on which the difference is relevant have to be very few. And at least except for transients that last in the few milliseconds, likely nonexistent for normal folks, and one would think that if youre clipping at 10 dB below the transient levels, you've got a significantly underpowered system (by a factor of ten), and whether simply passively biamping could make a significant sonic difference in that situation is not at all clear to me.

If you clipping at -10db transient and you have any reasonably powered amp (100w or more) you have much bigger problems than can be solved with bi-amping or even buying a bigger amp. You would really need to look into the overall speaker/room/amp configuration and go from there.
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post #26 of 36 Old 04-03-2012, 11:39 AM
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Originally Posted by ethan winer View Post

yes, but to be clear, bi-amping when done properly is indeed worthwhile. But you need speakers that can do this correctly, and you need measuring software to set up the active crossover properly.

--ethan

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post #27 of 36 Old 04-11-2012, 03:27 PM
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Originally Posted by walbert View Post

Miles, I'm going to have to disagree with you, and the Anthem salesman. What really killed it for me was his instence that "only a pair of ears is needed to hear the difference" - poppycock. When you track the source of the entire "support for passive bi-amping" argument back you arrive at Anthem's doorstep, where they'd be happy to sell you an amplifier. In the final thread you linked, note FOH and penngray's replies which absolutely get into the issue (or read the Rod Elliot article I linked).

How is it possible to put something so out of context? Here's what I really said and note what it was in response to, i.e. some of the setup needed for a properly controlled A/B comparison.

http://www.avsforum.com/avs-vb/showp...5&postcount=17

For the full meaning the discussion has to be read from start to finish. To reiterate -- again -- several older discussions, all of which started with nothing but someone asking whether to use the biamp option in an AVR:

- there's nothing to lose except some speaker wire, assuming speakers are biampable and jumpers are removed

- it does not increase overall power output, but that's not the point

- it can help only if the amp clips, by isolating distortion to the section causing it

- if you're looking at purchasing new as opposed to reconfiguring existing equipment, just get the right amp from the start instead of considering biamping or for that matter bridging

- expecting that a generic active crossover substituting for a purpose-made passive one will give good results is wishful thinking, in the context of home audio and the average DIY "lab"

All of the above was challenged in older threads and technical explanations were subsequently provided to each point. The fact that some people were trying to prove a negative was lost on them. Note that penngray, whom you reference, conceded (his word) that heat loss in a biamped passive crossover is not an issue after all, thus indicating that at last he considered Ohm's Law, the foundation of all circuits. Briefly, the channel may be receiving a full range signal but due to high impedance at the frequencies beyond the bandwidth of each crossover section, there's little power output at those frequencies therefore each amp channel is *not* doing the same work as in non-biamp mode. This is the little-understood part.

oh and btw I've never been a salesman and ironically Anthem AVRs don't have a biamp option... so much for conspiracy theories.

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Originally Posted by walbert View Post

The argument that you're going to save a tweeter from clipping distortion is dubious at best

That's pure assumption and I wouldn't mention it to anyone who works in the parts and service department of a speaker manufacturer or dealership. You may never be pushing your amp into clipping but that doesn't mean that people elsewhere don't misuse their equipment at dance parties or from three rooms away. It happens often enough to create full time positions out of repairing the aftermath.

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post #29 of 36 Old 04-11-2012, 03:57 PM
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Nick, your arguments would make sense iff:

- We were talking about an active xo ahead of the amplifiers (and why do we have to denigrate "average users" so much just for the sake of argumentation (the straw man that "oh well the "average user" cannot figure this out so that doesn't work!!", really? - sure it's complex, and not worth the time based on the results, but it's not impossible and it completely ignores the capabilities of many modern xover devices).

and/or

- You otherwise had a solution to address the (higher) power demand placed on an MCH amplifier (irrelevant if we're dealing with monos, but (since we're creating a lot of straw men here) monos are not as seemingly common (and passive bi-amplification is a terrible reason to justify buying more monos imho)) and the (potentially) clipped signal coming out of the amplifier itself.

Basically, you lost me with the "nothing to lose" arguments (that's a weak position to start with, but it's also so commonly a segue into audiophile nonsense) - what next? Bi-wiring? Power cleaners? Cable lifters? Vibration mats?
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post #30 of 36 Old 04-11-2012, 04:02 PM
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Quote:
Originally Posted by glimmie View Post

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Originally Posted by ethan winer View Post

yes, but to be clear, bi-amping when done properly is indeed worthwhile. But you need speakers that can do this correctly, and you need measuring software to set up the active crossover properly.

+1

+1
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