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Question on bi-amping - Page 11

post #301 of 1039
Quote:
Originally Posted by JHAz View Post



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.
.

You make a common error with the term "feeding." Amplifiers don't force power into speakers. Speakers draw it from the amp. They will draw only what they need. You can't force them to take more. In other words, it isn't possible to overpower a tweeter relative to a woofer. You can only change the power dissipation for both using the volume control. If you want a tweeter that is louder relative to the woofer, you need make a change in the crossover whether it is active or passive.
post #302 of 1039
Quote:
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.
But you are moving the goalposts here. If "the demands of the music/soundtrack ever call for it," then it's not unused amplifier power, now is it? And if your single amplifier can't deliver the power you need at any point, then what you need isn't two amplifiers, but one larger amplifier.

I defined headroom as "unused amplifier power." But you're using it the way many people do, as "the extra power available for transient peaks." Here's the problem: Going from a 50w amp to a 100w amp doubles the amount of power available for transient peaks. Going from one 50w amp to two 50w amps doesn't come close to doubling the amount of power available. In fact, it doesn't really add much at all. You'd have to understand how these devices work better than I do, to really understand why, but it's true.
post #303 of 1039
Quote:
Originally Posted by FMW View Post

That power calculator is incorrect. Distance from the speaker affects SPL by 3 db for each doubling of the distance.


Have you ever considered the possibility that you are incorrect?

http://www.audioenhancement.com/resources/videos/inverse-square-law/

And another calculator that gives the same as the first one with the same numbers put in...

http://www.crownaudio.com/elect-pwr-req.htm
post #304 of 1039
Quote:
Originally Posted by mcnarus View Post

Going from one 50w amp to two 50w amps doesn't come close to doubling the amount of power available. In fact, it doesn't really add much at all.

I went from one 80w amp in which it would shut off momentarily from being overdriven when I was playing music loud perhaps a couple of times a night. After getting the 2nd 80w amp and passively bi-amping, I haven't had them trip off since.

Passively bi-amping certainly gave my system more total power.
post #305 of 1039
Quote:
Originally Posted by arnyk View Post

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.

But I shouldn't attempt this with my good $3000 speakers though?
post #306 of 1039
Quote:
I went from one 80w amp in which it would shut off momentarily from being overdriven when I was playing music loud perhaps a couple of times a night. After getting the 2nd 80w amp and passively bi-amping, I haven't had them trip off since.

Passively bi-amping certainly gave my system more total power.
It's good you got your problem fixed. But if I were having a problem like that with an amp, the last thing I would do would be to buy a second, identical amp. Buy a better amp.
post #307 of 1039
Quote:
Originally Posted by kiwi2 View Post

Quote:
Originally Posted by lovinthehd View Post

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?

Could be same thing depending on your point of view I suppose. Depends how much you want to do it and how much time you want to put into it. Personally I may try something like that soon as I've recently retired and will soon have plenty of time on my hands for such a project (otherwise I probably wouldn't bother).
post #308 of 1039
Quote:
Originally Posted by mcnarus View Post

It's good you got your problem fixed. But if I were having a problem like that with an amp, the last thing I would do would be to buy a second, identical amp. Buy a better amp.

I know. However I was wanting to end up with 4 amp channels for a possible active bi-amp setup and didn't need two big powerful 2-channel amps for the job. I calculated that two 80w 2-channel amps would be suffice. I brought one initially by itself to test it out before committing to buy the second one. The one by itself did shut off into protection mode occasionally when playing my system loud, but since adding the second one it hasn't happened since. (that was six months ago now)

So my practical hands on experience suggests that passively bi-amping does add extra power capacity to a system.
post #309 of 1039
Quote:
Originally Posted by lovinthehd View Post

Personally I may try something like that soon as I've recently retired and will soon have plenty of time on my hands for such a project (otherwise I probably wouldn't bother).

So you practically agree with the Anthem article too then.
post #310 of 1039
Quote:
Originally Posted by kiwi2 View Post

Quote:
Originally Posted by lovinthehd View Post

Personally I may try something like that soon as I've recently retired and will soon have plenty of time on my hands for such a project (otherwise I probably wouldn't bother).

So you practically agree with the Anthem article too then.

Depends on your time priorities I suppose, when working I'd prefer to spend most of my off time cycling rather than something like this....but now I will have time for both! I already have a miniDSP and have some speakers I wouldn't mind experimenting with....
post #311 of 1039
Quote:
Originally Posted by lovinthehd View Post

Depends on your time priorities I suppose, when working I'd prefer to spend most of my off time cycling rather than something like this....but now I will have time for both! I already have a miniDSP and have some speakers I wouldn't mind experimenting with....

Well as these are my good speakers I use daily, I wouldn't want to be without them for any length of time so I will probably forget going active and just stay with the passive bi-amp setup. Very happy with the sound now anyhow.
post #312 of 1039
Quote:
Originally Posted by kiwi2 View Post

Quote:
Originally Posted by arnyk View Post

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.

But I shouldn't attempt this with my good $3000 speakers though?

That's up to you. I favor the low stress route for learning - put enough skin in the game to make it interesting, but don't bet the farm!

Once you see it work, if you like the results, up the ante!
post #313 of 1039
Quote:
Originally Posted by kiwi2 View Post

I went from one 80w amp in which it would shut off momentarily from being overdriven when I was playing music loud perhaps a couple of times a night. After getting the 2nd 80w amp and passively bi-amping, I haven't had them trip off since.

Passively bi-amping certainly gave my system more total power.

Spreading the current load out to more transistors, and perhaps subsequently spreading the heat out to more area on the heat sinks, may have led to lower transistor and heatsink temps - and that may have been the reason for no more shutdowns after you reconfigured your system. So, yeah, in a sense I guess you can say that passively bi-amping gave your system more power, but I think you realize that's not quite what other people here are saying.
post #314 of 1039
Quote:
Originally Posted by kiwi2 View Post

So my practical hands on experience suggests that passively bi-amping does add extra power capacity to a system.

Power may have zero to do with why it cut out before and not now. That's merely one consideration. However, the power aspect has been examined by enough smart people people to stick with the conclusion it provides no meaningful power increase (assuming the full range signal and in-speaker crossover approach).
post #315 of 1039
In my last post I stated that my passive bi-amped Maggie’s aside from channel separation the bass has more authority - I also run 3 Mackie’s HR824 for the HT L/C/R - 2 HR824 were also used for two channel only for years - (excellent speakers) the difference between the passive Maggie’s and the active Mackie’s is not really a fair comparison - the presentation of both couldn’t be more dissimilar - for serious listening I always choose the passive bi-amped Maggie’s - I can’t help to wonder whether the average audiophile can really distinguish the passive to active in a controlled environment - my guess would be not.
post #316 of 1039
But, of course, you're above average, right?
post #317 of 1039
Whoa, guys, a lot of opinions here! I'm pretty sure someone can run a test. No need to prove a negative. Measure the max clean output of a single amp vs the max clean output of a passive biamp (same amps of course). Arguing about it seems, well, very unscientific... reminds me of the dark ages where people dictated the laws of nature but only Galileo bothered to test them! smile.gif

So far I've been able to gather the following views about passive biamping ("PBA"):

1) Does PBA improve sound quality? Seems most agree it does NOT. (As for ACTIVE biamping, it seems some believe that it DOES improve sound quality BUT some say it can be tricky to do correctly).

2) Does PBA give you more overall power? Here the opinions are all over the map:
a) some say it does NOT (or it does very little) so don't bother with PBA.
b) some say it DOES, but it's "unused power"... but frankly I'm not sure anyone can draw that conclusion without knowing a system's power demands. For the sake of argument can we just assume that more power is the goal? We'll take it as a given that if your amp is powerful enough then you don't need to PBA. (I know, I know, you'll recommend we all just get awesome 200lbs stereo amps so we don't have to bother PBA, but let's assume that that is not an option, but BPA is an option smile.gif
c) among those who believe PBA DOES increase power, some say it doubles the power, while others think it's much less.

Galileo is rolling in his grave smile.gif
post #318 of 1039
There's lots of opinion on item 2, as there usually is in many things audio, but the facts support 2a.
post #319 of 1039
Quote:
Originally Posted by whoaru99 View Post

There's lots of opinion on item 2, as there usually is in many things audio, but the facts support 2a.

If you're right, then the upside for me is I can use my 2 extra amp channels to set up a 9.1 system! If the opposite is true then I'll be biamping my mains and going with 7.1. Win-win I guess. I really didn't think it was gonna be so hard to find out... I just assumed Anthem knew what they were talking about. But seriously, someone in this forum must have the ability to run the test, or have a contact with one of the audio magazines to do it for us!... I'd pay to know the result!! smile.gif
post #320 of 1039
It's all been done....time and time again.

You already have the result. 2a. Most people just don't want to believe it though because they have a hard time understanding that 1 and 1 in this regard isn't the same thing as 1 + 1 as you've been taught all your life.
post #321 of 1039
Quote:
I'm pretty sure someone can run a test. No need to prove a negative. Measure the max clean output of a single amp vs the max clean output of a passive biamp (same amps of course).
Not so simple. We measure amps into pure resistive loads. I don't see how you could measure biamping that way. Biamping presumes the presence of a speaker, which will not be purely resistive.

However, one thing we do know: If a single amp has sufficient power to drive a speaker to the desired level, no amount of additional power, in any configuration, will make a difference. It really will be unused amp power.
Quote:
If you're right, then the upside for me is I can use my 2 extra amp channels to set up a 9.1 system!
If you are comparing the actual benefit of adding channels to the speculative and in all likelihood imaginary benefit of passive biamping, well, there really isn't much choice, is there?
post #322 of 1039
Quote:
Originally Posted by mcnarus View Post

If you are comparing the actual benefit of adding channels to the speculative and in all likelihood imaginary benefit of passive biamping, well, there really isn't much choice, is there?

1) So go with the 9.1 and don't look back?

As an aside:

2) how will I know if my amp doesn't have enough power? What should I be listening for? Does clipping literally sound like a "clipping" noise? Cuz, if I reach that point then I'll look to get a better, more powerful, stereo amp for my L&R main speakers (instead of passively biamping)

3) B&W says bi-wiring is a must, but I can't stand bi-wiring from a single binding post... the spade keeps falling out and it drives me friggin nuts!... THAT alone is enough to make me want to biamp! wink.gif Any tips?? (other than "get better binding posts or better plugs" smile.gif
post #323 of 1039
Quote:
So go with the 9.1 and don't look back?
That would be the correct choice.
Quote:
how will I know if my amp doesn't have enough power? What should I be listening for?
Turn it up a bit above the maximum level you like to listen at. Let's just say that clipping distortion is distinctive enough that if you have to ask, your amp isn't clipping. smile.gif
Quote:
B&W says bi-wiring is a must
B&W is full of $hit. They are only saying that to serve the interests of their dealers, who get to sell you twice as much of the overpriced cable you don't need anyway. Accept this fact: Audio manufacturers don't tell you things you need to know; they tell you things that serve their commercial interests.
post #324 of 1039
Quote:
Originally Posted by stereoforsale View Post

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?

Have you seen bench tests demonstrating the loss of power when driving all channels versus two on a multi-channel AV Receiver? Its pretty typical to see 125wpc for two channels, dip 30-50% when five channels are driven.

Certainly power available for transient peaks is reduced when trying to hit 105dB when the biamp feature engaged in the Receiver.
post #325 of 1039
Quote:
Originally Posted by UndersAVS View Post

Have you seen bench tests demonstrating the loss of power when driving all channels versus two on a multi-channel AV Receiver? Its pretty typical to see 125wpc for two channels, dip 30-50% when five channels are driven.

Certainly power available for transient peaks is reduced when trying to hit 105dB when the biamp feature engaged in the Receiver.

Yes, I have seen that in product reviews. And if I understand you correctly, I wondered the same thing: using the 2 unused amp channels actually reduces the output of ALL the channels, and therefore, if bi-amping doesn't increase power, then what I've actually done is LOWERED the power by adding the 2 channels. I'm better off leaving the 2 spare channels unused to free up power for the other channels. In this scenario passive biamping actually DECREASES power... is that possible?! you just blew my mind!
post #326 of 1039
Quote:
Originally Posted by kiwi2 View Post

I went from one 80w amp in which it would shut off momentarily from being overdriven when I was playing music loud perhaps a couple of times a night. After getting the 2nd 80w amp and passively bi-amping, I haven't had them trip off since.

Passively bi-amping certainly gave my system more total power.

Kiwi,
With little description of the parameters involved, I wonder whether your 80wpc amp was shutting down because you were playing your system at very loud volume; and perhaps in a large room as well; and maybe for an extended period.

I would guess that a well designed amp would distort noticeably before shutting down, causing one to decrease the volume control, and that only a poorly designed amp would shut down before that point, but I'm not everyone, haven't used every speaker, and never used any 80wpc amps.

Supplying speaker sensitivity and impedance specs, room dimensions, and distance between speakers and seating would offer a better idea as to the nature of the problem and why passive bi-amping solved the problem. How loud and how long did you play before shutdown occurred? Are you using the new amp to provide power to the low frequency drivers?

I'm curious as to the equipment involved and what you did to remedy the situation before buying another amp.
post #327 of 1039
Quote:
Originally Posted by stereoforsale View Post

Yes, I have seen that in product reviews. And if I understand you correctly, I wondered the same thing: using the 2 unused amp channels actually reduces the output of ALL the channels, and therefore, if bi-amping doesn't increase power, then what I've actually done is LOWERED the power by adding the 2 channels. I'm better off leaving the 2 spare channels unused to free up power for the other channels. In this scenario passive biamping actually DECREASES power... is that possible?! you just blew my mind!

Bear in mind that using the channels to passively biamp part of a speaker isn't the same thing as using those channel to drive a complete/full range speaker.

In other words, using two channels normally wired vs. four channels wired in this passive biamp is the same/similar load on the receiver/amp power supply. It's really neither gain nor loss in that regard.
post #328 of 1039
After reviewing this thread about passive bi-amping, another about adding expensive high-power amps that are not required but improve sound dramatically, and so forth I have decided to stick with my tried-and-true mathematical formula: 1 + 1 = 3 for very large values of 1.
post #329 of 1039
Quote:
Originally Posted by stereoforsale View Post

Yes, I have seen that in product reviews. And if I understand you correctly, I wondered the same thing: using the 2 unused amp channels actually reduces the output of ALL the channels, and therefore, if bi-amping doesn't increase power, then what I've actually done is LOWERED the power by adding the 2 channels. I'm better off leaving the 2 spare channels unused to free up power for the other channels. In this scenario passive biamping actually DECREASES power... is that possible?! you just blew my mind!

You see my point vividly, and I don't see why it wouldn't be more detrimental than good.

If seeking more power for peaks under demanding conditions, use of four amps and the associated dwindling power when biamping a Receiver seems to defeat the process.

The work-around... Use the biamp feature with a seperate amp connected to the rear channel pre-amp outputs... Or just buy a more powerful amp to use with the front channel pre-amp outputs. Whichever is more cost-effective.
post #330 of 1039
Quote:
Originally Posted by whoaru99 View Post

Bear in mind that using the channels to passively biamp part of a speaker isn't the same thing as using those channel to drive a complete/full range speaker.

In other words, using two channels normally wired vs. four channels wired in this passive biamp is the same/similar load on the receiver/amp power supply. It's really neither gain nor loss in that regard.

True or false? When passive biamping, the Receiver sees the entire speaker load and delivers the same load to each amp. The speaker crossover then filters out the unwanted signal.

Thus, each amp is presented with the same power requirements.
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