Skip to main content ↑ ↓

Notice

Please note that most of the software linked on this forum is likely to be safe to use. If you are unsure, feel free to ask in the relevant topics, or send a private message to an administrator or moderator. To help curb the problems of false positives, or in the event that you do find actual malware, you can contribute through the article linked here.
Topic: Passive bi-amping: What is the benefit? (Read 26447 times) previous topic - next topic
0 Members and 1 Guest are viewing this topic.

Passive bi-amping: What is the benefit?

I'm not sure if this is the correct place to discuss this topic, but I have a question about passive bi-amping, assuming an AVR is handling the task.

What I understand about bi-amping is that it won't do that much because the same transformer is being used, but it will allow you to go louder with less distortion from the amp's side because you will effectively be providing more power to the speakers?

That's another thing I thought about. I can see how a transformer can be the ultimate limiting factor in output. But if you think of a bank of power amp devices in an AVR, each one of them will have the same max output based on the voltage supplied to them.

As each one of their outputs goes towards max, their individual distortion increases. In this case, you are supplying let's say 50W to the woofer and 10W to the tweeter. The distortion at the woofer will be higher than the tweeter, simply due to the higher power that output device is providing. If one device was supplying the entire 60W, the distortion would be higher for both woofer and tweeter. Makes sense? No?

More power doesn't sound like a bad thing, to me anyway. If I'm wrong in the above, please correct me.

Passive bi-amping: What is the benefit?

Reply #1 –
The main advantage I see is bypassing the passive crossovers.
"I hear it when I see it."

Passive bi-amping: What is the benefit?

Reply #2 –
Under some circumstances, you can cause measurable improvements by moving from 1) standard connection to 2) bi-wiring to 3) bi-amping to 4) active analogue cross overs to 5) active digital cross overs.

There are questions about audibility, but there are also questions about value for money / bang for your buck. If you spend $1000 on digital cross overs, four monoblock amplifiers and two speakers, will that sound better than spending $1000 on an integrated amplifier and two speakers? It's also hard to compare like with like.

Cheers,
David.

Passive bi-amping: What is the benefit?

Reply #3 –
I think you will find that most monitors now on sale for more than $100/ea already come with an active crossover and a separate amplifier for each driver built in.

Passive bi-amping: What is the benefit?

Reply #4 –
To expand upon what xnor's comment, here's what Siegfried Linkwitz has to say on the subject of passive crossovers:

Quote
The only excuse for passive crossovers is their low cost. Their behavior changes with the signal level dependent dynamics of the drivers. They block the power amplifier from taking maximum control over the voice coil motion. They are a waste of time, if accuracy of reproduction is the goal.


The full article is here:
Linkwitz Lab: Crossovers

And multi-amping + active crossovers is a handy way to eliminate passive crossovers. Why not? Amplifiers are cheap these days.

Passive bi-amping: What is the benefit?

Reply #5 –
Quote from: 4season on
Why not?

Because they aren't foolproof when not in one package. It's the perfect solution for active speakers (that's why you see it that often), but if you would do this with a separate crossover -> amp -> speaker setup, swapping a woofer and a tweeter will probably destroy the tweeter, right?

Sure, you might do this on your own, but it'll be a commercial disaster. And as the HiFi market doesn't accept active speakers very well for some reason (probably because you can't upgrade the components separately? It's mostly a problem for the stores anyway) I don't see active crossovers become a standard anytime soon, despite its technical superiority.
Music: sounds arranged such that they construct feelings.

Passive bi-amping: What is the benefit?

Reply #6 –
Quote from: xnor on
The main advantage I see is bypassing the passive crossovers.


But that ain't passive biamping.

Passive biamping leaves the passive crossovers in place.

It's based on the idea that amps with what I call premature clipping in another thread are common.

It isn't.

Passive biamping is an essentially zero cost feature when implemented. It can be waved in front of ignorant customers as a reason to buy my product.

Passive bi-amping: What is the benefit?

Reply #7 –
Quote from: Arnold B. Krueger on
But that ain't passive biamping.

Yeah, no I wasn't talking about that.

There's a reason it is also known as "fool's bi-amping".
"I hear it when I see it."

Passive bi-amping: What is the benefit?

Reply #8 –
I have to admit, this is the first time I've heard of passive bi-amping...   

Quote
What I understand about bi-amping is that it won't do that much because the same transformer is being used...
In a good design with a "solid" power supply, the transformer won't have much effect.    If one channel driven alone clips at 100W, it should clip at (approximately) 100W with all channels driven.

Quote
As each one of their outputs goes towards max, their individual distortion increases. In this case, you are supplying let's say 50W to the woofer and 10W to the tweeter. The distortion at the woofer will be higher than the tweeter, simply due to the higher power that output device is providing. If one device was supplying the entire 60W, the distortion would be higher for both woofer and tweeter. Makes sense? No?
No.    distortion remains very low as long as you keep the level below clipping (assuming a reasonably good solid-state amplifier).    If the amp is rated at 50W and the specs are honest, distortion won't be an issue unless you try to exceed 50W. 

With a normal (active) bi-amplified design, you can get more power and you don't get the small power loss that you normally get in the passive crossover network.  Plus, the woofer amplifer can clip without clipping the tweeter signal, and some of the distortion will be filtered-out simply because the woofer can't reproduce the distortion harmonics.   

With passive bi-amping, if the woofer amplifer is clipping, the tweeter amplifier is probably clipping too.  Both amplifiers are providing the exact same signal, they are both putting-out the full frequency-range and same voltage,  so I don't think you are getting any more power to the speakers.  Each amplifier is putting-out less current that it would if used alone, but current is NOT a limiting factor (again assuming a good amplifier with the proper impedance load, etc.)

Passive bi-amping: What is the benefit?

Reply #9 –
Quote from: DVDdoug on
Quote

I have to admit, this is the first time I've heard of passive bi-amping... 

What I understand about bi-amping is that it won't do that much because the same transformer is being used...
In a good design with a "solid" power supply, the transformer won't have much effect.    If one channel driven alone clips at 100W, it should clip at (approximately) 100W with all channels driven (ACD).


AVRs that do well in ACD testing are generally big, heavy and pricey.

Common AVRs in the $250-500 range don't do so well in ACD tests based on sine waves. However those tests are far more severe than actual use with music because the crest factor of music is >> 3 dB (since wave).

The worst damage done by passive biamping is probably reinforcement of yet another golden ear myth.  The actual difference is never enough to unmistakably audible. That leaves the door wide open for the placebo effect.

I can and have heard it: "Now that my dealer opened my ears to the glorious sonic advantages of passive biamping, I'm more willing to try those expensive speaker cables that he has been raving about""

Passive bi-amping: What is the benefit?

Reply #10 –
Quote from: Arnold B. Krueger on
"Now that my dealer opened my ears to the glorious sonic advantages of passive biamping, I'm more willing to try those expensive speaker cables that he has been raving about""


And an extra monoblock per speaker! 
"I hear it when I see it."

Passive bi-amping: What is the benefit?

Reply #11 –
Passive bi-amping is audibly worthless to a consumer and costs twice as much. It won't make your system play even a scant 1 dB more loudly, whereas buying a single amp that has twice the power of the first one being consider really does increase output by 3 dB. That's discernible in some instances and arguably worth it, but passive bi-amping never is.

Passive bi-amping: What is the benefit?

Reply #12 –
Slightly off topic - I have heard an improvement in the clarity of the mid range when  a passive sub woofer system is added to a two way system  which  includes a passive crossover to remove the  low frequencies in the branch that goes to the existing two way speakers.

Passive bi-amping: What is the benefit?

Reply #13 –
Quote from: KMD on
Slightly off topic - I have heard an improvement in the clarity of the mid range when  a passive sub woofer system is added to a two way system  which  includes a passive crossover to remove the  low frequencies in the branch that goes to the existing two way speakers.


Well, that does makes sense. If you relieve the woofers in the main speakers from having to play back low bass frequencies that are outside of their ideal performance envelope, odds are they'll play mid-bass and midrange more clearly.

Speakers need more and more excursion* to produce lower and lower frequencies, especially the relatively small woofers in most main speakers. Excessive excursion can cause all kinds of audible side effects, and with enough power, you'll reach the mechanical limits of the speaker and either destroy the suspension or burn out the voice coil.

* Or more correctly, the lower the frequency, the more air you have to move. You can do this with larger diaphragms, longer excursion or both.

Passive bi-amping: What is the benefit?

Reply #14 –
Dealers love pushing both bi-wiring and (passive) bi-amplifying because it makes the consumer buy twice as much merchandise as they should.

Passive bi-amping: What is the benefit?

Reply #15 –
Quote from: KozmoNaut on
Quote from: KMD on
Slightly off topic - I have heard an improvement in the clarity of the mid range when  a passive sub woofer system is added to a two way system  which  includes a passive crossover to remove the  low frequencies in the branch that goes to the existing two way speakers.


Well, that does makes sense. If you relieve the woofers in the main speakers from having to play back low bass frequencies that are outside of their ideal performance envelope, odds are they'll play mid-bass and midrange more clearly.

Speakers need more and more excursion* to produce lower and lower frequencies, especially the relatively small woofers in most main speakers. Excessive excursion can cause all kinds of audible side effects, and with enough power, you'll reach the mechanical limits of the speaker and either destroy the suspension or burn out the voice coil.

* Or more correctly, the lower the frequency, the more air you have to move. You can do this with larger diaphragms, longer excursion or both.




Thats what I thought, unfourtunately most commercial sub woofer add on systems for existing hi fi systems  I have seen don't have this feature and so the resulting amplifier and speaker configuration does not have the benefit of relieving the original bass unit from the low frequency excursions.

A high pass fillter circuit in the branch to the existing speakers would acheive this, would anyone on the forum care to propose what would be suitable.

Passive bi-amping: What is the benefit?

Reply #16 –
Quote
anyone on the forum care to propose what would be suitable.


Use a pro or semi pro multi channel audio interface (DAC) which comes with a sophisticated software EQ and effects package.

Send the same mix to your mains and/or sub(s) but vary the high and low pass filters as appropriate. e.g.

MOTU Cuemix

Also better quality monitors usually come with a variety of built in high, low and sometimes even mid shelving filters and gains.

Still a jolly tricky business to get right.

Passive bi-amping: What is the benefit?

Reply #17 –
Quote from: KMD on
Thats what I thought, unfourtunately most commercial sub woofer add on systems for existing hi fi systems  I have seen don't have this feature and so the resulting amplifier and speaker configuration does not have the benefit of relieving the original bass unit from the low frequency excursions.

A high pass fillter circuit in the branch to the existing speakers would acheive this, would anyone on the forum care to propose what would be suitable.


On the contrary, most active subwoofers have a set of outputs that are high-level filtered, to connect main speakers. This is true for subwoofers with line level inputs as well as those with speaker-level inputs.

On the other hand, most passive subwoofers will only have a set of speaker-level inputs, and no outputs. A lot of them do not even have a low-pass filter built in, never mind a high-pass filter and speaker outputs. Only "home theater in a box"-type products generally have passive subwoofers with high-pass filters for satellite speakers, for cost reasons.

For passive subwoofers, you are generally expected to have your own amplifier and crossover in place, and the knowledge of how to integrate those into your system.

For the situation you are describing, an active subwoofer with speaker-level in/outputs and a configurable crossover point is probably the best solution. If your amplifier has pre-out connections, you can use line-level signals instead, and loop the signal back into the power amp section via the subwoofer, this solution will have less distortion and utilize your main amplifier better.

E: Honestly, I think you should start a new thread, and describe exactly what it is you want to do. You will receive good advice in no time at all :-)

Passive bi-amping: What is the benefit?

Reply #18 –
Quote from: KozmoNaut on
most active subwoofers have a set of outputs that are high-level filtered, to connect main speakers


I contest that claim. The majority of home-audio subs I see do not apply high-pass filters to the outputs, it's simply pass through for convenience. Even many studio monitor subs that have line-level pass through don't.  (they only usually have a buffer between the line level input and output to prevent problems with the impedance getting too low for the source). Especially for speaker-level connections, I haven't seen any with a crossover in a sub.

Passive bi-amping: What is the benefit?

Reply #19 –
Quote from: Ferongr on
I contest that claim. The majority of home-audio subs I see do not apply high-pass filters to the outputs, it's simply pass through for convenience. Even many studio monitor subs that have line-level pass through don't.  (they only usually have a buffer between the line level input and output to prevent problems with the impedance getting too low for the source). Especially for speaker-level connections, I haven't seen any with a crossover in a sub.


My DALI SWA 12 has it, though it's a very basic fixed 150hz first-order crossover, so the utility of it is debatable.

Passive bi-amping: What is the benefit?

Reply #20 –
Any ideas for a scratch built passive circuit to use at speaker voltage levels. If 1st order is appropriate, like  the order of the filter in the DALI SWA 12,  it seems using a single capacitor for each of the stereo channels would do it.

Passive bi-amping: What is the benefit?

Reply #21 –
Quote from: Yahzi on
I have a question about passive bi-amping, assuming an AVR is handling the task.
What I understand about bi-amping is that it won't do that much because the same transformer is being used, but it will allow you to go louder with less distortion from the amp's side because you will effectively be providing more power to the speakers?

No, "more power" is not the possible benefit. Lower HF distortion is.
There should be no difference at all until the amplifier is driven into non-linear behavior. That depends on quite a few variables, especially if the difference is to rise to "audible" thresholds. But that is absolutely possible.
When a single Ch of the amp drives the speaker full range, it sees a load (simple 2-way, 1st order electrical XO) like this:

When the legs of the XO are separated, the individual ch's (in bi-amp mode) see this:


Obviously the current loading/draw is quite different from the single Ch.
This can lead to the LF Ch clipping before the HF Ch does

The result of that, would be that the clipping spectra is now limited to and ow passed (attenuated) by the woofer filter.
That certainly opens the possibility of audibility.
Music is not steady state, but dynamic. Scroll down to The Peak Power Demands of Well-recorded Music for an interesting demo. Then there is the spectrum of the music itself and demads for power at LF vs HF.
It is possible that some clipping would still go undetected. Its also possible that folks can imagine hearing things that aren't there. Many, many variables involved.
In short, if you already have the AVR, bi-ampable speakers and an extra 2pcs of zip wire ($2 ?), you can give it a whirl yourself.
Highly doubtful you'll hear any (real) difference other than at higher levels....if any at all. But it is possible, not impossible.
Oh and to stave off the inevitable ad hominem, I don't sell amps or passive biampable speakers.

cheers,

AJ
Loudspeaker manufacturer

Passive bi-amping: What is the benefit?

Reply #22 –
In real world use with music, the burden to the amplifier is always from the bass content, never the treble. In using two amps in passive bi-amping the amp driving the tweeter may indeed be running cooler and have tons of power on reserve, but that isn't the limiting factor for the overall system's maximum SPL so we need not concern ourselves with how happy that amp is; it is the bass amp we need to concern ourselves with. Can it suddenly play a tad more loudly because it is no longer burdened by driving the tweeter? NO! It still clips at almost exactly the same point because in real world use that point is always determined by the bass content of the music and the burden of driving the woofers, never the treble content and the burden of driving the tweeters.

Part of the beauty of active bi-amping, on the other hand,  is we can take advantage of how easy it is to drive just the HF content of the music when it is isolated from LF content, before the amp even sees the signal, and therefore buy much less powerful [read: less expensive] amps for the tweeter.

A pusher of passive bi-amplifying  may contend that although the "bass" amp [keep in mind it still sees the full range signal, unlike in an active bi-amp setup] will start to clip at pretty much the same volume level as it would in driving a full range speaker, the claimed advantage is that the nature of that distortion will first be identifiable to human hearing in the treble content and since there is no tweeter to reproduce that, we won't notice a problem as quickly. Oh brother. I think that's grasping at straws to rationalize the doubly as expensive setup, but maybe, just maybe, it does help protect one's tweeters, just a smidge, for people who constantly "red line" their engines, er amps.

Passive bi-amping: What is the benefit?

Reply #23 –
Quote from: mzil on
the claimed advantage is that the nature of that distortion will first be identifiable to human hearing in the treble content and since there is no tweeter to reproduce that, we won't notice a problem as quickly. Oh brother. I think that's grasping at straws, but maybe, just maybe, it does help protect one's tweeters, just a smidge.

Full range clipping spectra vs clipping spectra with a 3rd-4th order filter @ 2k, being discernible, isn't grasping at straws. Claiming absolutes pushes only ignorance.
Loudspeaker manufacturer

Passive bi-amping: What is the benefit?

Reply #24 –
It's easy to show that passive bi-amping is electrically different compared to using a conventional  single amp, however nobody in the history of hifi has ever shown any evidence to support the notion that the difference is audible to humans, using music (or for that matter, a specially designed test signal), without intentionally driving one or more of the amps beyond its linear operating range, via ABX or any other similar, carefully conducted testing methodology, meeting our forum's TOS #8 criteria.