Question on bi-amping - Page 34 - AVS Forum
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post #991 of 1044 Old 12-12-2013, 02:04 PM
 
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Originally Posted by Speed Daemon View Post

You might want to recheck what a crossover does. smile.gif

Yeah I know what a crossover does. You'll find that excess power that isn't needed is just discarded which is pretty efficient, don't you think?
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Not if that power is being used.

Ever heard of the power distribution of audio signals? Might want to do some research before commenting further.
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There's nothing inherently inefficient about splitting the power in equal proportions

Oh, you probably don't realise it, but tweeters typically draw a fraction of the power of a typical woofer. Splitting the power 50-50 is an extremely inefficient use of the available power. Just do some homework.
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It's not very common with dynamic drivers, since HF drivers tend to consume less input power to meet their requirements for amplitude in their passband. But if you had some esoteric HF driver that's a power hog and took an equal amount of power, the inefficiency would lie at that driver, and not at the amplifier.

Name an esoteric HF driver that could benefit with 120 watts? Even if you could name one, it would be the exception, not the norm.
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Shaun was correct in saying that separate amplifiers with more/better power supplies will yield more usable power with all channels driven, compared to a typical AVR. If you care to read back many pages, that point has been laid out in some detail.

There is no advantage to using separate amplifiers if the additional power won't be used compared to a typical AVR. Shaun said that bi-amping would be beneficial if using dedicated amplifiers. A single large amplifier of equivalent power non bi-amped could offer improved headroom over a bi-amped set up for easy to understand reasons. Can you guess what those reasons are?

So more usable power with all channels driven, you say? A fantasy condition that doesn't exist in actual usage? And I see you are conflating the difference between available power and usable power, which are really two different things, You can have more available power and never use it. Just a thought. wink.gif
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post #992 of 1044 Old 12-12-2013, 02:08 PM
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Originally Posted by goneten View Post

I don't care about passive bi-amping because it's a waste of time.

Oh, cmon, it doesn't waste that much time. Or wire.

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post #993 of 1044 Old 12-12-2013, 02:13 PM
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Originally Posted by Heinrich S View Post

Technical question. My friend has a Rotel RMB-1075 power amp. 5 x 120 watts.

If I had to allocate two channels in a bi-amp role would that mean each speaker would have 240 watts (120 watts to the tweeter and 120 watts to the woofers)? Do I have that correct?
That could be correct for a theoretical woofer and tweeter that miraculously had exactly the same impedance always, and the same power handling capabilities. In the real world that doesn't happen very often at all.

Generally speaking, HF drivers are smaller than LF drivers because it's much easier to get smaller objects to reverse direction than it is for larger ones. Also as a general rule, it's harder to dissipate heat from a small space than from a much larger one. The end result is that feeding a "general rule" tweeter 120W will cause it to fail sooner than later.

The whole topic is about far more than how much power you can dump into something. Presumably the quality of the sound, affected by things like HF/LF matching would also be important. If the primary purpose is still to make a coherent sound, then more has to be done than figuring out how to dissipate lots of amplifier power.

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post #994 of 1044 Old 12-12-2013, 02:17 PM
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Originally Posted by sivadselim View Post

I doubt any of us would recommend someone go out and purchase equipment just so they can passively biamp their biwirable/biampable speakers.
Well, the equipment doesn't just magically appear (at least not at my house), so it's fair to say that it has to be gotten at some point. Are we just assuming that everybody has nothing but an AVR to use? That's not the case for me, but I'll be happy to play along as long as we have the ground rules established.

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post #995 of 1044 Old 12-12-2013, 02:25 PM
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Quote:
Originally Posted by goneten View Post

Yeah I know what a crossover does.
Do you? Because you wrote "the passive circuit would route the same full range signal to each speaker." Well the job of a passive crossover (which is what we're talking about here) is anything but to "route the same full range signal to each speaker".

Better luck next time.

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post #996 of 1044 Old 12-12-2013, 02:27 PM
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Ok here you are! http://www.chuckhawks.com/bi-wire_bi-amp.htm


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post #997 of 1044 Old 12-12-2013, 02:58 PM
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Quote:
Originally Posted by Speed Daemon View Post

Well, the equipment doesn't just magically appear (at least not at my house), so it's fair to say that it has to be gotten at some point. Are we just assuming that everybody has nothing but an AVR to use? That's not the case for me, but I'll be happy to play along as long as we have the ground rules established.

I think I addressed this in the rest of my post that you didn't quote.

And as far as someone with separates is concerned, I think most people would still probably recommend buying a more powerful amplifier over simply buying an additional amplifier (identical to an existing one or not) for a passive biamping setup.

Generally speaking, of course. I realize that someone may have a pet product that they truly believe in and really want to use to passive biamp. Or maybe they got a great deal. Or a hand-me-down. Or whatever.

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post #998 of 1044 Old 12-12-2013, 04:38 PM
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Quote:
Originally Posted by sivadselim View Post

I think I addressed this in the rest of my post that you didn't quote.

And as far as someone with separates is concerned, I think most people would still probably recommend buying a more powerful amplifier over simply buying an additional amplifier (identical to an existing one or not) for a passive biamping setup.

Generally speaking, of course. I realize that someone may have a pet product that they truly believe in and really want to use to passive biamp. Or maybe they got a great deal. Or a hand-me-down. Or whatever.
I agree with you 100%. My position all along has been that replacing the power section of an AVR with a good set of separate power amps, and upgrading speakers to match the new power levels is the best way to get results.

I've also been in a position where I knew what I needed, lacked the cash to get there and experimented with what I had. A certain poster here apparently has nothing more than an AVR and wanted to try it out. As I said, if we're still talking in the context of that person's desires, I'm down with that. If not, what is the current circumstance?

I have to ask this since a couple of people have come in making wild assertions and imposing their own pet rules that don't appear to have anything at all to do with what was being discussed before. I'm growing tired of private definitions, if you follow me.

You seem to be one of the reasonable ones here, so I'm asking you for clarification, that's all.

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post #999 of 1044 Old 12-12-2013, 05:20 PM
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Quote:
Originally Posted by Speed Daemon View Post


CLAIM: "the tweeter amp will clip well before the woofer amp even though it's producing a fraction of the power of the woofer amp"
CLAIM: "it still must swing the full range/full voltage signal"
CLAIM: "assuming a nominal 8 ohm load from each speaker section"
CLAIM: "the 200W amp can swing ~40 volts, the 100W amp ~28V"
CLAIM: "So, a 200W + 100W amp in passive biamp only works OK if your demand never exceeds the potential voltage swingl of the smallest amp. In this case, using a 200W amp with a 100W amp is a waste of the 200W amp."

I have no time for people who only make vicious personal attacks, but I can prove you're a liar. There you go.

You don't understand it at all, that's why you think it's wrong. The part I'm unclear about is if you actually realize that and are just trying to deflect from your incorrect statement about the 200W and 100W amps, or if you don't even know that it was so incorrect.

Edit: Post 993 provided the clarity I was unclear about. You don't know.

I will play along in your style though....

What do you think is incorrect about it, and why?

Just because there is a knob doesn't mean you should turn it.
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post #1000 of 1044 Old 12-12-2013, 05:27 PM
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Originally Posted by goneten View Post

I don't care about passive bi-amping because it's a waste of time. Proper bi-amping allows you to drive the highs and lows independently with the use of an active crossover. I'm not going to wade through 30+ pages in order to reach the conclusion that passive bi-amping is not a waste of time. Thank you but no thanks.

That's not what active biamping is "about", either, btw,

Just FYI, the premise of this entire thread is discussion about biamping with full range signals applied to the separated hpf and lpf of a speakers crossover; aka "fool's biamping".

So, while discussion of real biamping is interesting, it just tends to cloud this thread.

Just because there is a knob doesn't mean you should turn it.
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post #1001 of 1044 Old 12-12-2013, 05:30 PM
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Originally Posted by Speed Daemon View Post

That could be correct for a theoretical woofer and tweeter that miraculously had exactly the same impedance always, and the same power handling capabilities. In the real world that doesn't happen very often at all.

That is not why 120 + 120 doesn't equal 240 in this case.

Just because there is a knob doesn't mean you should turn it.
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post #1002 of 1044 Old 12-12-2013, 06:18 PM
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Originally Posted by sivadselim View Post

That the amplifiers are still amplifying a full-range signal is, essentially, irrelevant. Read the thread. And the other recent one.

smile.gif

I'm curious about why you say it's irrelevant?

Just because there is a knob doesn't mean you should turn it.
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post #1003 of 1044 Old 12-12-2013, 06:38 PM
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Originally Posted by wse View Post

Ok here you are! http://www.chuckhawks.com/bi-wire_bi-amp.htm

This article has been referenced many times, and thoroughly discredited for many reasons.
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post #1004 of 1044 Old 12-12-2013, 07:17 PM
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Originally Posted by stereoforsale View Post

This article has been referenced many times, and thoroughly discredited for many reasons.
The opinion part can be left behind, but the description of terms is pretty accurate:
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In passive bi-amping, the output from the pre-amplifier is fed to a pair of identical stereo power amps. All four amplifier channels are fed the same, full range, signal from the pre-amp. This is important, so take note of it. The output of the power amps is fed to the stereo loudspeakers, the left and right outputs of one power amp to the left and right loudspeakers' high frequency binding posts and the left and right outputs of the other power amp to the left and right loudspeakers' low frequency binding posts. We now have the same, full range signal everywhere. The high frequency part of each loudspeaker's passive internal crossover is doing what it always does with a full range signal, as is the low frequency part of each loudspeaker's crossover.
That is what you were talking about doing, correct?

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post #1005 of 1044 Old 12-12-2013, 07:27 PM
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While the general description of how it's connected is fine, he fell flat on his face with this bit -
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The system's total amplifier power has been doubled, which is probably a good thing and may actually result in a sonic improvement at high listening levels. However, if doubling the system's amplifier power is necessary, it would be cheaper to buy (for example) one 200 watt stereo amplifier than two 100 watt stereo power amps of the same quality to get the same result.

You don't get the same result with two 100W amps in this type of setup as you do with one 200W amp. Not even remotely close.

Just because there is a knob doesn't mean you should turn it.
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post #1006 of 1044 Old 12-12-2013, 09:53 PM
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Originally Posted by Speed Daemon View Post

I'm not biting. It's your claim to back up or fail on. You failed. You're over.
Considering how little you actually know, as referenced by the questions you ask in post 988, I find that hilarious.
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post #1007 of 1044 Old 12-12-2013, 10:45 PM
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Quote:
Originally Posted by Speed Daemon View Post

CLAIM: "assuming a nominal 8 ohm load from each speaker section"
CLAIM: "the 200W amp can swing ~40 volts, the 100W amp ~28V"
From Ohm's Law, P=V²/R
∴ V=√(P.R)
For 100W/8Ω, P=√(100x8)=28.28Vrms. Peak voltage of a sinewave is √2.RMS, so 28.28Vrms = 40Vpk.
For 200W/8Ω, P=√(200.8)=40Vrms or 56.57Vpk.
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Originally Posted by Speed Daemon View Post

CLAIM: "it still must swing the full range/full voltage signal"
It must. In a passive biamp, by definition, there is no xover at line level before the poweramp so full signal is applied to the input of the two power amps. SS amplifiers are voltage amplifiers: they take an input voltage (signal) and amplify it by the gain, typically about 30x and provide that voltage at the output terminals. With no load you'll still measure this voltage (input x gain). As you apply a load, current will be drawn from the amp proportional to the voltage and the load. Again, simple Ohm's Law, I=V/R.

In both amps in the passive biamp, they still provide this full range voltage at the amp output terminals. The HF amp will see a nominal load, say 8Ω, and below the xover the load will decrease as the impedance rises as frequency reduces. The HF amp will be seeing the full range signal at it's terminals, but will only supply (significant) current and therefore power to the load near to and above the xover frequency.
The LF amp will see a nominal load, say 8Ω, and above the xover the load will decrease as the impedance rises as frequency increase. The LF amp will be seeing the full range signal at it's terminals, but will only supply (significant) current and therefore power to the load near to and below the xover frequency.
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Originally Posted by Speed Daemon View Post

CLAIM: "So, a 200W + 100W amp in passive biamp only works OK if your demand never exceeds the potential voltage swingl of the smallest amp. In this case, using a 200W amp with a 100W amp is a waste of the 200W amp."
CLAIM: "the tweeter amp will clip well before the woofer amp even though it's producing a fraction of the power of the woofer amp"

A while ago, I posted a link to a well respected site owned by Rod Elliott. Here is the link again.
In it he was trying to explain the benefits of active biamping, but his graphs are useful.



In this image he shows two sine waves, both with an amplitude of one, and what happens to the total amplitude waveform when the two are added together, one at 100Hz and one at 1kHz. This is called superposition, and you may note, I mentioned it before.

This is relevant because music, soundtracks etc are a very complex mix of different frequencies at different amplitudes and all of these vary with time. The LF energy tends to predominate so is the larger waveform. Where this becomes important is in a single amping or passive biamping, the LF waveform tends to dominate the signal that will cause the amplifiers to clip.

Now looking at two more of his graphs.



If this is the 100W8Ω and the '2' on the vertical is the 40Vpk just prior to when the amplifier clips, a clean output voltage will be presented at the output of the amplifier. It will also present the same at the output of the 200W amp as well because it can hit nearly 57Vpk before clipping.



Note: Rod changed the scales to better express the point he is making, so looking at the vertical scale, multiply by 2 so it's the same as the one immediately above.
Here we have increased the signal level above the 40Vpk the 100W amplifier could cleanly output. The amp is clipping. The 200W amp still has nearly 17V of signal swing available to it before it gets to this point. As both amplifiers are receiving the same wideband input and must output the same signal voltage for the passive biamp set up to remain with the same frequency balance as the single amp, when the signal level exceeds 40Vpk in this case, the HF amp will be clipping, and the LF amp not (until >56.57Vpk).

The HF signals need not be very high at all. As can be seen from the example graphs, even if the HF signal were a mere 1Vpk, as soon as the LF signal exceeds 39Vpk, the HF signal will be clipping.
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post #1008 of 1044 Old 12-13-2013, 09:55 AM
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Originally Posted by Speed Daemon View Post

The opinion part can be left behind, but the description of terms is pretty accurate:
That is what you were talking about doing, correct?

Oh ok, yeah, I think the description is generally correct. But his commentary of the pros/cons of passive biamping have been dismissed by BOTH sides of the argument.
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post #1009 of 1044 Old 12-13-2013, 01:48 PM
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Originally Posted by stereoforsale View Post

Oh ok, yeah, I think the description is generally correct. But his commentary of the pros/cons of passive biamping have been dismissed by BOTH sides of the argument.
Thanks for confirming that! I know that topics can change, and it seems that over the life of this thread quite a few posts have been made that really had nothing to do with the conversation at the time. While I support free expression, I also think that it's common courtesy to at least attempt to be sociable and join the conversation as opposed to trying to turn the focus on one's self. I for one would be embarrassed if I missed the question.

My own impression of this Chuck Hawks web page is that its author is highly opinionated and has no shortage of ego. That comes with the territory. What I also see is a lot of truth in the page, much more than in many posts here made by the countless sophomores at Wikipedia U. You might not care for the snarky delivery; I personally balk at extremes like "NO effect", but there are many kernels of truth there.

For example:
Quote:
Folks with scant technical knowledge and lots of blind faith report sonic improvements with bi-wiring. This is known as the placebo effect in medicine.
It is a very human trait to imagine a difference that you anticipate or just plain want, even when it doesn't happen. The non-medical term is "vivid imagination". What's more, it can affect people at all levels of knowledge. (Yes, Mr. Hawks made an unnecessary dig there.) This is the reason why scientists use double blind testing, and why products like the abx comparitor were developed.

Mr. Hawks reaches the limit of his knowledge on the subject when he declares that "total amplifier power has been doubled" without any elaboration. As you may recall, that potential for doubled power is affected by a variety of factors, which has been covered to death in past pages. Those who fail to resolve those outstanding issues cannot come to any real conclusions.

You are correct that many posts here have bashed the heck out of Mr. Hawk's treatise. But has he really been debunked? Sadly, no. Those posts which carry the largest chips on their shoulders tend to also come from a place of ego. Six of one, half a dozen of another. There's a HUGE difference between people seeking to cut down the words of others in the hope of making themselves seem larger, and those who serve the truth above all else. Don't confuse an abundance of verbal sparring with actually winning a point!

I'm not making this a contest, but it does look like the web page in question does have a higher concentration of fact than many posts made here. Give creduit where it's due, and don't confuse those who shout the loudest with somehow being correct about anything. This is an Internet forum, possibly the most perfect truth-free zone that humankind has been able to create. wink.gif

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post #1010 of 1044 Old 12-13-2013, 03:26 PM
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Originally Posted by Speed Daemon View Post

Thanks for confirming that! I know that topics can change, and it seems that over the life of this thread quite a few posts have been made that really had nothing to do with the conversation at the time. While I support free expression, I also think that it's common courtesy to at least attempt to be sociable and join the conversation as opposed to trying to turn the focus on one's self. I for one would be embarrassed if I missed the question.

My own impression of this Chuck Hawks web page is that its author is highly opinionated and has no shortage of ego. That comes with the territory. What I also see is a lot of truth in the page, much more than in many posts here made by the countless sophomores at Wikipedia U. You might not care for the snarky delivery; I personally balk at extremes like "NO effect", but there are many kernels of truth there.

For example:
It is a very human trait to imagine a difference that you anticipate or just plain want, even when it doesn't happen. The non-medical term is "vivid imagination". What's more, it can affect people at all levels of knowledge. (Yes, Mr. Hawks made an unnecessary dig there.) This is the reason why scientists use double blind testing, and why products like the abx comparitor were developed.

Mr. Hawks reaches the limit of his knowledge on the subject when he declares that "total amplifier power has been doubled" without any elaboration. As you may recall, that potential for doubled power is affected by a variety of factors, which has been covered to death in past pages. Those who fail to resolve those outstanding issues cannot come to any real conclusions.

You are correct that many posts here have bashed the heck out of Mr. Hawk's treatise. But has he really been debunked? Sadly, no. Those posts which carry the largest chips on their shoulders tend to also come from a place of ego. Six of one, half a dozen of another. There's a HUGE difference between people seeking to cut down the words of others in the hope of making themselves seem larger, and those who serve the truth above all else. Don't confuse an abundance of verbal sparring with actually winning a point!

I'm not making this a contest, but it does look like the web page in question does have a higher concentration of fact than many posts made here. Give creduit where it's due, and don't confuse those who shout the loudest with somehow being correct about anything. This is an Internet forum, possibly the most perfect truth-free zone that humankind has been able to create. wink.gif

LOL!!!. That's some of the best spin and redirection I've read in a long time.

Now, how about that 200W + 100W amp thing? Still waiting for your ownership on that one.

Just because there is a knob doesn't mean you should turn it.
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post #1011 of 1044 Old 01-05-2014, 03:56 PM
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Quote:
Originally Posted by DonH50 View Post

Well, not really... Tweeter and woofer each have 120 W available to them. Nothing in the system sees 240 W, there is no effective power gain. You don't get 240 W to the woofer, do not get 240 W to the tweeter, do not pass go, do not collect $2000, etc. (Apologies to those who have never played Monopoly.) If you had a single 120 W amp driving both, they each still see 120 W max. That is true for active or passive bi-amping. The endless argument to this point should have shown you that any advantage from passive bi-amping is minimal at best in the vast majority of cases, meaning no practical power gain. That is not the main reason to bi-amp, active or passive. For active, is to optimize the power to each driver, often by using a smaller amp for the tweeter, and potentially to optimize the crossover response and other parameters by having individual amps power each driver. For passive, the primary advantage seems to be to sell more amps and wire, though some have seen benefits (marginal, IMO, but YMMV).


It has been decades since I played Monopoly. Has inflation increased the reward for passing go to $2,000? I'd hate to have to pay rent on Park Place!
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post #1012 of 1044 Old 01-05-2014, 06:33 PM
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Typo, though with inflation $2k is probably low...

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post #1013 of 1044 Old 01-05-2014, 07:47 PM
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Quote:
Originally Posted by arnyk View Post

Well indict yourself if you will Amir, but the above statement is the product of your weird ideas about quoting people which includes chopping sensible statements into nonsense.

What I said was:

":QSC's clipping indicator is inside the amp's feedback loop and only sees large voltages when the output stage is saturated."

Not the same thing as your bastardized version:

"amp's' feedback loop and only sees large voltages"

Here's what happens. In the QSC power amp circuit (and just about any SS amp), the whole amp is inside an inverse feedback loop. Typically power amps have from 20 to 40 dB or more inverse feedback which means that the open loop gain of the power amp circuit is 20 to 40 dB more than whatever gain the amp has with the inverse feedback loop closed. However, when the output stage saturates, it looses most if not all of its gain, and the excess gain in the driver circuits causes the signal voltage provided to the output stage to increase by from 20 to 40 dB or more. The QSC clipping circuit monitors the signal voltage at the input to the output stage and when it increases by 20 to 40 dB or more when the amp clips it activates the LED.

Amir if you can, get one of the big tech boys in your shop who actually takes the covers off of power amps and knows how to probe around inside them without hurting themselves or the amp show you how this works. ;-)

Or, add $100 to my Paypal account (arnyk@wowway,com) and I'll rip open one my QSC amps and post some information here about how the signal voltages inside the amp changes dramatically when it clips. ;-)

Again some variation in this happens in just about every SS amp. It is particularly pronounced in power amps with output stages that have gain, which is not always the rule. If the output stage has unity gain, you may have to back up a stage so that there is gain between the point you are probing and the amps output terminals.


I'm not familiar with QSC or any amplifiers they manufacture. Amplifiers that have output stages with voltage gain are interesting. Could you send me a link to a schematic(s)?

Thanks
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post #1014 of 1044 Old 01-05-2014, 08:17 PM
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Yes active bi- amping is the only way to benefit from Bi-amping

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post #1015 of 1044 Old 01-07-2014, 06:56 AM
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I felt some diagrams could aid the conversation.

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post #1016 of 1044 Old 01-07-2014, 08:00 AM
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except with real program material, in passive biamping half of the power is never wasted. Assuming the amps' voltage is the limiting factor in clipping, the mid/woofer amp's output loses somewhere around 25%, and the tweeter amp loses about 75%, just because that's the way real world content is.
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post #1017 of 1044 Old 01-07-2014, 08:04 AM
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Quote:
Originally Posted by JHAz View Post

except with real program material, in passive biamping half of the power is never wasted. Assuming the amps' voltage is the limiting factor in clipping, the mid/woofer amp's output loses somewhere around 25%, and the tweeter amp loses about 75%, just because that's the way real world content is.

Correct. Look at the math portion and see numbers very similar to what you put.

I should've used "halfish" instead of "half"
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post #1018 of 1044 Old 01-13-2014, 09:27 AM
 
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Apologies for asking this again, but please explain briefly why (2) 2 x 200W amps in bi-amp configuration isn't 400W? It's 200W for the highs and 200W for the lows, per speaker. But that equals 400W. With (1) 2 x 200 amp both speakers would have 200W total, each.

Sorry I'm just trying to jog my memory on this, but there is something I'm missing.
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post #1019 of 1044 Old 01-13-2014, 11:00 AM
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Quote:
Originally Posted by Heinrich S View Post

Apologies for asking this again, but please explain briefly why (2) 2 x 200W amps in bi-amp configuration isn't 400W? It's 200W for the highs and 200W for the lows, per speaker. But that equals 400W. With (1) 2 x 200 amp both speakers would have 200W total, each.

Sorry I'm just trying to jog my memory on this, but there is something I'm missing.

Take it form me as I just went through a painful experience with this over the holidays.

DO NOT USE HIGH POWER AMPS ON BIAMPED TWEETERS!

I put a four channel QSC theater amp with 170w RMS per channel on my LCR tweeters. Hey, they only need a few watts but I have this nice compact amp sitting around that cosmetically matches the other power amps I am using. Now TWO sets of new tweeters later I am using some rebuilt old Hafler SE120s at 60w per channel. And even that's too much so I am looking at some 20w class A designs long term.

The problem is that all it takes is a digital error (click) or two or an improper turnoff sequence where there's a thump and your tweeters are gone. Fuses are useless. After the origional tweeters went out I put 1.5amp fast blow fuses on the new tweeters. Well those new $200 ScanSpeak tweeters did a great job protecting those expensive fuses!

Another trick I am also using now is to have a 33uf capacitor in series with the tweeters. This rolls off the low end to about -3db @ 700hz. This is far enough from the 1800hz crossover point not to cause significant phase shift. But it will offer some protection against low frequencies getting to the tweeters. Yes, the active crossover does this too but consider a turn on or off thump or some other anomaly on the tweeter amp. The active crossover won't protect against that.

Before all this nonsense I was using 10 watt tube amps on the tweeters and never had an issue in 10 years of biamping. I guess the cost of re-tubing every year was not that much after all! rolleyes.gif

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post #1020 of 1044 Old 01-13-2014, 11:39 AM
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Quote:
Originally Posted by Heinrich S View Post

Apologies for asking this again, but please explain briefly why (2) 2 x 200W amps in bi-amp configuration isn't 400W? It's 200W for the highs and 200W for the lows, per speaker. But that equals 400W. With (1) 2 x 200 amp both speakers would have 200W total, each.

Sorry I'm just trying to jog my memory on this, but there is something I'm missing.

200 W to the lows and 200 W to the highs, yes, but neither driver, high or low, ever sees 400 W. To achieve 400 W drive to any driver you need a 400 W amp.

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