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post #271 of 1044 Old 11-11-2013, 06:34 PM
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Originally Posted by theatredaz View Post

Ok so what I've understood so far about Bi-amping is>



* A passive crossover is designed to see 100W TOTAL power> adding another 100 watts would only be disipated as heat because it only accept 100W TOTAL (not 200W) anyways

If the internal crossover has Separate passive components going to each speaker> then it's still only handles 100W total. Except in Bi-amp ~ now the woofer can see a full 100% 50 Watts of power and the tweeter will use 20% @ 50WATTS.

Basically the issue then lies in having the woofers use100% of available power from the amp instead of lets say 60-75% power (that the tweeter midrange need).

So in essence although doubling the power in total will not yield doubling of power> it will allow the low end to use all available power instead of sharing it with the tweeter.

Single amp @ 100W = 60-70*WATTS @ (Woofer) + 20-30WATTS @ (Tweeter / Mid)

Bi-AMP @100+100 = 50-60WATTS @ (WOOFER) + 20-30 WATTS @ (TWEETER / MID)

*It would help to contact the Manufacturer of the speakers and ask how much power the Low x-over and High x-over can handle when fed separate power feeds.

Mmmmm....no.

The extra 100W is not dissipated in the speaker. Maybe a little extra heat from the amp because you're using two instead of one but it's not wasted power as in turned to heat in the crossover or speaker because that power is never produced.

Assuming, for sake of discussion, the passive crossover splits the power 75% woofer and 25% tweeter, it doesn't matter if you use one 100W amp or two 100W amps. 75% of 100 goes to the woofer, 25% of 100 goes to the tweeter. Same both ways.

The speaker handles the same amount of power either way. Nothing changes about the power or the power handling.

Just because there is a knob doesn't mean you should turn it.
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post #272 of 1044 Old 11-11-2013, 07:31 PM
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Quote:
Originally Posted by theatredaz View Post

Ok so what I've understood so far about Bi-amping is>



* A passive crossover is designed to see 100W TOTAL power> adding another 100 watts would only be disipated as heat because it only accept 100W TOTAL (not 200W) anyways

If the internal crossover has Separate passive components going to each speaker> then it's still only handles 100W total. Except in Bi-amp ~ now the woofer can see a full 100% 50 Watts of power and the tweeter will use 20% @ 50WATTS.

Basically the issue then lies in having the woofers use100% of available power from the amp instead of lets say 60-75% power (that the tweeter midrange need).

So in essence although doubling the power in total will not yield doubling of power> it will allow the low end to use all available power instead of sharing it with the tweeter.

Single amp @ 100W = 60-70*WATTS @ (Woofer) + 20-30WATTS @ (Tweeter / Mid)

Bi-AMP @100+100 = 50-60WATTS @ (WOOFER) + 20-30 WATTS @ (TWEETER / MID)

*It would help to contact the Manufacturer of the speakers and ask how much power the Low x-over and High x-over can handle when fed separate power feeds for bi-amping.

Personally I would think that: take for example my Paradigm Monitor 11's can handle 280 Watts total RMS. >Then Adding an amp that puts 140WATTS RMS to the woofer section and another amp @ 100 Watts for the Mid tweet section would yield better acoustics theoretically ~ than an amp that would lets say only do 140 WATTS RMS (200W Peak) Assuming both amps where evenly matched in terms of voltage output so there's no delay between the two signals going into the Speaker cabinet etc.





____

Of course, your amps put out zero power (leaving self noise aside) during the silences between songs, and put out less power when the signal is lower (say, most obviously, during a fade out, or if you ever turn the volume control down from your personal max) and with the exception of massively loudness war compressed recentish music the music itself will be at less than full tilt maybe 80 percent of the time or more. Movie dialog is likely to be in teh 77 to 85 dB range at reference, and you probably aren't using a watt or two to reproduce that in many systems. If you fed 100 watts instead the dialog would be 20 dB louder, because that's how speakers work. More power - more louder until they start compressing.

How much power goes to each driver depends on the signal. I did some research a while ago and found that in general real music and movies will have not more than 25% of their audio power in the tweeter's range. Feeding the tweeter more requires unbalancing the system and will make things sound too too bright.

A 25 percent power increase is a decibel. A 100 percent power increase is 3 dB (and AFAIK the usual thought is 3 dB sounds 'one notch' louder to most people). So biamping a two way, or any system where the split is at the tweeter, you can't ever, in the real world, get more than a 1 dB increase in available power. Of course if you happen to be like me and don't listen terribly loud, you're not ever touching max power from your amps anyway because, first, you've got a sub that's handling the most power hungry frequencies and second, a mere 3 dB reduction from whatever is the max is cuts power in half. I tend to listen to movies at 10 to 20 dB below reference, depending on my mood, so I use between 1/100 and 1/1000 of the power that would be needed to hit reference levels. The unused power remains unused because the amp is not allowed to slip into an alternate universe where Ohm's law doesn't apply.
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post #273 of 1044 Old 11-11-2013, 08:46 PM
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Quote:
Originally Posted by JHAz View Post

A 25 percent power increase is a decibel. A 100 percent power increase is 3 dB (and AFAIK the usual thought is 3 dB sounds 'one notch' louder to most people).

100/3 does not equal 25 tongue.gif

What is 'one notch'?
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post #274 of 1044 Old 11-11-2013, 09:12 PM
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Quote:
Originally Posted by Audionut11 View Post

Quote:
Originally Posted by JHAz View Post

A 25 percent power increase is a decibel. A 100 percent power increase is 3 dB (and AFAIK the usual thought is 3 dB sounds 'one notch' louder to most people).

100/3 does not equal 25 tongue.gif

What is 'one notch'?

Why would you expect a doubling of power as happens with a 3dB increase to relate to 100 divided by 3? You do realize deciBels are logarithmic? Try this if you want to go between dB and a percentage...http://www.ehow.com/how_8208377_convert-decibel-increase-percent.html

3 dB I believe is generally considered at which point most perceive as a noticeable change in volume or something along those lines, a notch so to speak.

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post #275 of 1044 Old 11-11-2013, 10:47 PM
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Any suggestions as to why Abbey Road studios would use a pair of 400w 8ohm Classe mono blocks to power the B&W speakers in their control room.

http://www.bowers-wilkins.com/Images/MediaImages/large/Explore--Abbey--Banner.jpg

http://www.classeaudio.com/delta/specs/cam400.htm

http://www.abbeyroad.com/Content/Pdfs/STUDIO_one_floorplan_pdf_v1.1.pdf
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post #276 of 1044 Old 11-12-2013, 05:57 AM
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Originally Posted by UndersAVS View Post

Any suggestions as to why Abbey Road studios would use a pair of 400w 8ohm Classe mono blocks to power the B&W speakers in their control room.

http://www.bowers-wilkins.com/Images/MediaImages/large/Explore--Abbey--Banner.jpg

http://www.classeaudio.com/delta/specs/cam400.htm

http://www.abbeyroad.com/Content/Pdfs/STUDIO_one_floorplan_pdf_v1.1.pdf

The control room is about 10m x 8 m or about 30 x 24 and seems to have a high ceiling. This is a far larger room than the typical listening room.

I see no subwoofers, so they are on their own with 3 pair of 8 inch woofers. Which is kinda meager for a room this size.

The usual peak level goal for recording monitoring is 116 dB instead of the 105 dB we use for home audio. The speakers are rated at 1,000 wpc. 116 dB at 1 meter takes 400 watts, and the listening distance is large enough to increase that by maybe 3-4 dB to 800-1000 wpc.

There appear to be 2 mono amps per speaker. It is not clear how they are being deployed. I presume that the two amps are bridged which might get the over 1,000 wpc that may be required.

A lot of money has been spent, but the sound may not be all that posh for some of us.
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post #277 of 1044 Old 11-12-2013, 06:01 AM
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Quote:
Originally Posted by Audionut11 View Post

Quote:
Originally Posted by JHAz View Post

A 25 percent power increase is a decibel. A 100 percent power increase is 3 dB (and AFAIK the usual thought is 3 dB sounds 'one notch' louder to most people).

100/3 does not equal 25 tongue.gif

Right, 20% increase in power = 1 dB is IMO a better approximation.

1 dB is well approximated by 10% change in voltage or 20% change in power.

0.1 dB is well approximated by a 1% change in voltage or a 2% change in power.

6 dB is twice the voltage.

20 dB is 10 times the voltage.
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post #278 of 1044 Old 11-12-2013, 06:30 AM
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Quote:
Originally Posted by Audionut11 View Post

100/3 does not equal 25 tongue.gif

What is 'one notch'?

Um, no, and I didn't suggest it is. If you increase power from, say 50 to 100 watts that's a 100 percent increase. It will yield a three dB SPL increase. Really.

one notch is how much you turn up to get just a little louder. More than merely noticeable, kind of like a meaningful increase. So when you turn it up a little you're likely increasing by at least 3 dB.
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post #279 of 1044 Old 11-12-2013, 06:38 AM
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Mmmmm....no.

The extra 100W is not dissipated in the speaker. Maybe a little extra heat from the amp because you're using two instead of one but it's not wasted power as in turned to heat in the crossover or speaker because that power is never produced.

Assuming, for sake of discussion, the passive crossover splits the power 75% woofer and 25% tweeter, it doesn't matter if you use one 100W amp or two 100W amps. 75% of 100 goes to the woofer, 25% of 100 goes to the tweeter. Same both ways.

The speaker handles the same amount of power either way. Nothing changes about the power or the power handling.

* Understood the woofer still only uses %75 power because the tweeters only need 25% anyways> but assuming there's distortion at near reference volumes in the tweeter freq's, then...That distortion isn't shared by the tweeters (when the amp requires to boost it's voltage outputs to max) if another amp powering the tweeters doesn't need to reach it's maximum output. Thus smoother playback at higher volumes that doesn't cause the tweeters to distort or clip, fortunately my Nad T977 has a soft clipping switch at the back to prevent the tweeters from reaching this stage, but audiographically adding an amp to power the tweeters separately , redcues the need for soft clipping which really lowers the input signal from reach it's maximum input voltage etc.

* Although I'm not sure if the tweeters would sound too bright.
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post #280 of 1044 Old 11-12-2013, 07:33 AM
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Quote:
Originally Posted by theatredaz View Post


Understood the woofer still only uses %75 power because the tweeters only need 25% anyways> but assuming there's distortion at near reference volumes in the tweeter freq's,

What is the justification for the assumption: "assuming there's distortion at near reference volumes in the tweeter freq's"?

You just seem to pick that out of the air!
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That distortion isn't shared by the tweeters

That can true for active biamping, but it is not true for passive biamping. Why aren't you distinguishing the two? Which one are you talking about, anyway?
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post #281 of 1044 Old 11-12-2013, 08:32 AM
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I neglected to account for the logarithmic scale. I was pretty sure I was missing something fundamental, hence the tongue smile!
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post #282 of 1044 Old 11-12-2013, 09:21 AM
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Quote:
Originally Posted by arnyk View Post

What is the justification for the assumption: "assuming there's distortion at near reference volumes in the tweeter freq's"?

You just seem to pick that out of the air!
That can true for active biamping, but it is not true for passive biamping. Why aren't you distinguishing the two? Which one are you talking about, anyway?


* Not as scientifically as technical as some members on AVS here , just generalizing something without getting into Algabreric math formulas on Tweeters distortion ratio's> I'm not going to say the tweeter distorts in definetly> but there is surface tension that causes the tweeter to become slightly harsh when pushed to reference levels, although to a trained hear it might be less noticeable with a second amp powering the tweeter, and thats what it comes down to. Adding another amp could mellow out that distortion at reference levels (but I agree an active~x-over will completely eliminate most distortion that passive x-overs still can be characterized with.)





______
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post #283 of 1044 Old 11-12-2013, 11:39 AM
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while I have seen at least one i\poster here who is in the industry suggest that passive biamping might yield an audible benefit IF you have audible distortion using a single amp, by not pushing the added tweeter amp into distortion and that makes some kind of sense, you would still have audible distortion in the woofer amp and therefore from the woofer. And since our ears are highly sensitive around 1 KHz, an octave or so below typical crossovers, the remaining distortion from the woofer should still be plenty annoying. better when possible to have enough power to begin with.
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post #284 of 1044 Old 11-12-2013, 11:52 AM
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^ I think that implies current-limiting is the primary clipping mechanism instead of lack of voltage headroom. I conjecture that is the minority of real-world situations.

"After silence, that which best expresses the inexpressible, is music" - Aldous Huxley
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post #285 of 1044 Old 11-12-2013, 02:08 PM
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Quote:
Originally Posted by JHAz View Post

while I have seen at least one i\poster here who is in the industry suggest that passive biamping might yield an audible benefit IF you have audible distortion using a single amp,

As others have already pointed out, the above depends on what causes the audible distortion.

Power amp clipping can be broken down into two categories;

(1) Voltage driven clipping

(2) Current driven clipping

Voltage driven clipping is far and away the most common kind of clipping. It simply means that the amp ran out of power.

Current driven clipping only happens if you are using too low of an impedance speaker for the application, which almost never happens.

For passive biamping to be any help at all, a further condition has to be met:

(3) The current driven clipping has to be due to both drivers being hooked up to the same amplifier. This is again usually not the case.

So, if two improbable situations occur at the same time, passive biamping just might be of some help.

Let me hide in the basement and stay there forever because a meteor might fall in the neighborhood! ;-)
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post #286 of 1044 Old 11-14-2013, 11:24 AM
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Guys, I'm new to this thread. I'm eager to learn and I'm very confused. I am passively biamping and have read many articles and posts against it. Anthem's website however, clearly states that this is all a myth. Passive biamping does work, and active biamping is not recommended. I'm not a technician by any stretch, but what the anti-passive-biamp camp does not realize (according to Anthem) is that when you passively biamp, the impedance is signficantly increased and therein lies the advantage. Meanwhile active biamping messes up the carefully designed crossover of any quality speaker and will likely reduce performance. I tend to believe the experts at Anthem, but I do the potential motivation of encouraging people to buy additional amps to boost sales. To put this debate to bed, has anyone, or any reputable magazine, actually tested this??? While judging sound quality may be subjective, I assume you can certainly test if passively biamping gives more headroom.
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post #287 of 1044 Old 11-14-2013, 11:37 AM
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Quote:
Originally Posted by stereoforsale View Post

Guys, I'm new to this thread. I'm eager to learn and I'm very confused. I am passively biamping and have read many articles and posts against it. Anthem's website however, clearly states that this is all a myth. Passive biamping does work, and active biamping is not recommended. I'm not a technician by any stretch, but what the anti-passive-biamp camp does not realize (according to Anthem) is that when you passively biamp, the impedance is signficantly increased and therein lies the advantage. Meanwhile active biamping messes up the carefully designed crossover of any quality speaker and will likely reduce performance. I tend to believe the experts at Anthem, but I do the potential motivation of encouraging people to buy additional amps to boost sales. To put this debate to bed, has anyone, or any reputable magazine, actually tested this??? While judging sound quality may be subjective, I assume you can certainly test if passively biamping gives more headroom.

Just to make it easier to refer to, here's what the faq on Anthem site says:

Doesn't passive biamping waste the amp's power because each channel still has to amplify the full range signal and not just the highs or the lows?
No. With the jumpers removed on a biampable speaker, the impedance of each section is not the usual 4 or 8 ohms, but several hundred if not more at the frequencies that the amp is "not supposed to be amplifying". Higher impedance means less current draw. No meaningful amount of current, no wasted power.

According a recurring audio-myth, only an active crossover should be used for biamping, in order to split the band before the power amp instead of inside the speaker, thereby reducing the amount of work each amp channel has to do. While active crossovers do have their place in PA systems, it should be noted that equalizers are also a part of it.

A generic active crossover on its own merely divides the audio band into smaller ones. The carefully custom-designed crossover in a high performance home audio speaker does a lot more. It is responsible for correcting frequency response aberrations of the individual drivers, maintaining phase coherence between drivers, optimizing off-axis response, balancing levels between drivers, setting up impedance, at times improving woofer performance by rolling off not just the top, but also frequencies that are too low and cause it to misbehave, and other things that vary according to model.

Tearing out the speaker's own finely-tuned crossover to replace it with an active crossover with generic controls almost guarantees that, just for starters, frequency response will be altered. Different sound doesn't mean better sound. Using the passive crossover in the speaker is indeed the correct way to biamp.

(What's biamping? It's using one amp channel for the speaker's mid-high frequency drivers, and another for the low-frequency drivers. The speakers must have separate inputs for this - be sure to remove the jumpers from the speaker inputs first or amp will become instant toast! If one amp starts running out of power, usually the one driving the woofer, then the other side remains clean instead of becoming part of the problem, a double-win. This is the very idea behind bass management and powered subwoofers in home theater systems.)

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post #288 of 1044 Old 11-14-2013, 11:40 AM
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I tend to believe the experts at Anthem, but I do the potential motivation of encouraging people to buy additional amps to boost sales.
Ya think?
Quote:
To put this debate to bed, has anyone, or any reputable magazine, actually tested this??? While judging sound quality may be subjective, I assume you can certainly test if passively biamping gives more headroom.
I'm not aware of any published tests that directly compare a single amp to passive biamping, but at this point so much is known about the effects that amplifiers have (and don't have) on sound that we can apply that knowledge to the case at hand. To address the specific issue you raise in your final sentence, "headroom" is just another term for "unused amplifier power." Of course, if you're using two amps instead of one, you have more "unused amplifier power." But unused amplifier power has no impact whatever on the sound.

In science, it's hard to prove a negative, so the burden of proof lies with those making the positive claim. Get back to us when Anthem published a blind listening test.

If you can't explain how it works, you can't say it doesn't.—The High-End Creed

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post #289 of 1044 Old 11-14-2013, 12:41 PM
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Hi StereoForSale,
Quote:
. . . (according to Anthem) is that when you passively biamp, the impedance is significantly increased and therein lies the advantage.
I don't see why significantly increased impedance would be an advantage, unless you had an anemic amplifier. In the end, you will be pumping the same amount of power through the speakers to get the same volume. As Mcnarus said, any power capability above that is really of no use.
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Meanwhile active biamping messes up the carefully designed crossover of any quality speaker and will likely reduce performance.
That statement makes the assumption that the crossover is indeed "carefully designed ", and can't be improved on by an active crossover. I doubt that is always the case. I agree that an active crossover is incapable of compensating for the impedance and phase issues with the driver, but it is also more difficult to deal with the frequency response in a passive crossover.

Maybe the most flexible solution would be to have passive components that dealt with each driver's phase issues (I'm not sure impedance issues need to be dealt with, separate from phase), and then have an active crossover to give you better granularity for controlling the frequency response and crossover behavior.
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post #290 of 1044 Old 11-14-2013, 12:47 PM
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Quote:
Originally Posted by lovinthehd View Post

Quote:
Originally Posted by stereoforsale View Post

Guys, I'm new to this thread. I'm eager to learn and I'm very confused. I am passively biamping and have read many articles and posts against it. Anthem's website however, clearly states that this is all a myth. Passive biamping does work, and active biamping is not recommended. I'm not a technician by any stretch, but what the anti-passive-biamp camp does not realize (according to Anthem) is that when you passively biamp, the impedance is signficantly increased and therein lies the advantage. Meanwhile active biamping messes up the carefully designed crossover of any quality speaker and will likely reduce performance. I tend to believe the experts at Anthem, but I do the potential motivation of encouraging people to buy additional amps to boost sales. To put this debate to bed, has anyone, or any reputable magazine, actually tested this??? While judging sound quality may be subjective, I assume you can certainly test if passively biamping gives more headroom.

Just to make it easier to refer to, here's what the faq on Anthem site says:

Doesn't passive biamping waste the amp's power because each channel still has to amplify the full range signal and not just the highs or the lows?
No. With the jumpers removed on a biampable speaker, the impedance of each section is not the usual 4 or 8 ohms, but several hundred if not more at the frequencies that the amp is "not supposed to be amplifying". Higher impedance means less current draw. No meaningful amount of current, no wasted power.

Anthem appears to be propagating a myth claiming that anything that reduces the load on an amplifier reduces its audible distortion. That is not true.
Quote:
According a recurring audio-myth, only an active crossover should be used for biamping, in order to split the band before the power amp instead of inside the speaker, thereby reducing the amount of work each amp channel has to do. While active crossovers do have their place in PA systems, it should be noted that equalizers are also a part of it.

Anthem appears to be propagating a myth claiming that anything that has an equalizer in it is a bad thing. That is not true.
Quote:
A generic active crossover on its own merely divides the audio band into smaller ones. The carefully custom-designed crossover in a high performance home audio speaker does a lot more. It is responsible for correcting frequency response aberrations of the individual drivers, maintaining phase coherence between drivers, optimizing off-axis response, balancing levels between drivers, setting up impedance, at times improving woofer performance by rolling off not just the top, but also frequencies that are too low and cause it to misbehave, and other things that vary according to model.

Anthem seems to be contradicting themselves by now glorifying "correcting frequency response aberrations of the individual drivers, maintaining phase coherence between drivers, optimizing off-axis response, balancing levels between drivers, improving woofer performance by rolling off not just the top, but also frequencies that are too low and cause it to misbehave, and other things that vary according to model". Those are all things that one does with equalizers.
Quote:
Tearing out the speaker's own finely-tuned crossover to replace it with an active crossover with generic controls almost guarantees that, just for starters, frequency response will be altered. Different sound doesn't mean better sound. Using the passive crossover in the speaker is indeed the correct way to biamp.

Anthem appears to be demonizing people all who convert speakers from passive to active crossovers by faulting them for being technically incompetent and not performing required engineering steps.
Quote:
(What's biamping? It's using one amp channel for the speaker's mid-high frequency drivers, and another for the low-frequency drivers. The speakers must have separate inputs for this - be sure to remove the jumpers from the speaker inputs first or amp will become instant toast! If one amp starts running out of power, usually the one driving the woofer, then the other side remains clean instead of becoming part of the problem, a double-win. This is the very idea behind bass management and powered subwoofers in home theater systems.)

Anthem appears to be misleading people by obfuscating the fact that passive biamping requires both amplifiers to amplify both low and high frequencies.

BTW, here's a link to Anthem's faq:

http://statement.anthemav.com/support/faq.php

I chased some other links on AVS and they now appear to be broken.

No place in this FAQ does it appear that Anthem admits to the fact that passive biamping introduces the risk of the low and high portions of the speaker not being properly driven in perfect balance, or that if you make an error while setting up the wiring for passive biamping you may short out amplifier channel(s) with the resulting possibility of damage to the amplifier.
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post #291 of 1044 Old 11-14-2013, 12:58 PM
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Anthem appears to be demonizing people all who convert speakers from passive to active crossovers by faulting them for being technically incompetent and not performing required engineering steps.

But a couple of days ago you said this.
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post #292 of 1044 Old 11-14-2013, 12:59 PM
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Ya think?
I'm not aware of any published tests that directly compare a single amp to passive biamping, but at this point so much is known about the effects that amplifiers have (and don't have) on sound that we can apply that knowledge to the case at hand. To address the specific issue you raise in your final sentence, "headroom" is just another term for "unused amplifier power." Of course, if you're using two amps instead of one, you have more "unused amplifier power." But unused amplifier power has no impact whatever on the sound.

In science, it's hard to prove a negative, so the burden of proof lies with those making the positive claim. Get back to us when Anthem published a blind listening test.

Thanks mcnarus. Appreciate the comment. What confuses me is many people won't even conceed that passive biamping gives more headroom... they say it adds nothing: not quality (which I accept) and not even headroom. For me, I want the headroom, in case the demands of the music/soundtrack ever call for it, even if briefly. For the lay person it's very hard to know how much power you need so it's difficult to say for if that extra power is truly "unused amp power"... but again, some people depute there is any additional headroom at all.

Maybe I should pose the question this way: I have B&W Matrix 803s - how much power do I realistically need to drive them at near reference level? To make it more complicated, my 9ch amp is rated at 125w with 2ch driven, and I have no clue what it's rated with all channels driven. Call me crazy but why wouldn't I passively biamp 2 of the unused channels, just in case?
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post #293 of 1044 Old 11-14-2013, 01:18 PM
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Maybe I should pose the question this way: I have B&W Matrix 803s - how much power do I realistically need to drive them at near reference level?

There is a good calculator at the bottom of this page...

http://www.allegrosound.com/Power_AllegroSound.html
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post #294 of 1044 Old 11-14-2013, 01:22 PM
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Originally Posted by arnyk View Post

Anthem appears to be demonizing people all who convert speakers from passive to active crossovers by faulting them for being technically incompetent and not performing required engineering steps.

But a couple of days ago you said this.

Yes I did, and the conflict between the two statements escapes me.

My point is that everybody around here is very clear about this being a challenging project but Anthem seems to be staking their reputation on nobody doing it right.
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post #295 of 1044 Old 11-14-2013, 01:29 PM
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Yes I did, and the conflict between the two statements escapes me.

You seem to agree with Anthem that converting passive crossovers in a speaker to active is futile.
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post #296 of 1044 Old 11-14-2013, 01:30 PM
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Futile or just extremely involved to achieve better results?

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post #297 of 1044 Old 11-14-2013, 01:35 PM
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What confuses me is many people won't even conceed that passive biamping gives more headroom... they say it adds nothing: not quality (which I accept) and not even headroom.

Well, unused headroom has no audible benefits so that is that about unused headroom.

For added headroom that you actually use to be helpful or even really noticable you need what is technically a lot of headroom - from 4 times to 10 times the power. If you want to know what twice power sounds like, change the digital volume control on your AVR by 6 clicks. What do you want to pay for that?
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For me, I want the headroom, in case the demands of the music/soundtrack ever call for it, even if briefly.

That's a big if. How do you know what fraction of your existing power is being used?
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For the lay person it's very hard to know how much power you need so it's difficult to say for if that extra power is truly "unused amp power"...

Right and without reliable evidence its hard to know if the glass is half empty or half full.
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but again, some people depute there is any additional headroom at all.

Well, if you run the scenarios, you come up with a goodly number of situations where the promise of extra power is completely vacant.
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Maybe I should pose the question this way: I have B&W Matrix 803s - how much power do I realistically need to drive them at near reference level? To make it more complicated, my 9ch amp is rated at 125w with 2ch driven, and I have no clue what it's rated with all channels driven. Call me crazy but why wouldn't I passively biamp 2 of the unused channels, just in case?

One of the scenarios is as follows. The limit to power with 7 channels running might be the power supply, which is shared among all of the channels. If you hook up two more channels how do you know that they aren't limited by the fact that they are hooked to the same power supply?

The 803 is yet another large floor stander with 90 dB/W sensitivity. In a typical room with typical listening distances you can probably hit peak reference levels with about 3 dB headroom.

If you want more headroom, the sure bet for vastly improved sound quality is a really good subwoofer if you don't already have one.
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post #298 of 1044 Old 11-14-2013, 01:38 PM
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There is a good calculator at the bottom of this page...

http://www.allegrosound.com/Power_AllegroSound.html

That power calculator is incorrect. Distance from the speaker affects SPL by 3 db for each doubling of the distance. If I put minimal numbers and then increase the distance from 1 meter to 2 meters, the calculator quadruples the amount of amplifier power needed. Good for selling amps but not good for providing the truth. I put the numbers from my system into the calculator using their recommendations for overhead, SPL etc. The result was 369 watts and the industry doesn't even make amplifiers that big. Nor do I listen anywhere near that loud. My actual amplifier use measures at less than 2 watts average with peaks as high as 18 watts. I have no idea what they would expect me to do with the other 351 watts. Calculator not recommended.
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post #299 of 1044 Old 11-14-2013, 01:39 PM
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Futile or just extremely involved to achieve better results?

Kind of the same thing.

I presently have my 2-way speakers passively bi-amped. Should I go the extra last step and order some MiniDSP units and remove the passive filters from my speakers?
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post #300 of 1044 Old 11-14-2013, 01:47 PM
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Yes I did, and the conflict between the two statements escapes me.

You seem to agree with Anthem that converting passive crossovers in a speaker to active is futile.

No, not futile, just potentially a really involved project.

For the record I am a strong proponent of active speakers. I own at least 3 active crossovers, I may have forgotten where one is... ;-)

Note that powered subwoofers are the one active biamplifying project that is actually pretty feasible to do. Try imagine me coming out against actively biamped subwoofers. If you know me, that will make your head ache! ;-)

If someone wants to have a fun winter, buy Vance Dickason's book and use it as your guide (note I didn't say cookbook) for an active biamping project involving some inexpensive 2 ways, perhaps one of the Pioneer Famous Designer series.
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