Bi-amping

[JJMP50]

I finally upgraded my HT with the purchase of some new speakers. I replaced my mix matched batch (JBL L1 mains/Athena Center and Athena B1 surrounds) with JBL Studio L series (830/C1/810 in Cherry). My question is about Bi-amping. These are the first speakers I've owned with 4 binding posts. Is Bi-amping fact or audio BS?

 

[highfigh]

Bi-amping, as in using one amp for the high-pass and one for the low-pass or bi-wiring, as in using separate cables for the HP and LP?

 

[bandphan]

id recommend searching the forum for bi/amp - bi/wire as there have been several long and slightly boring threads. The short and skinny would be that neither would present a benefit with most speakers and avrs.

 

[highfigh]

The main benefit to true bi-amping comes when an active crossover is used. If major EQ and treatment is needed, active circuitry is the best way because of the losses and effects from passive circuits. Unity gain is possible and an amplifier circuit that works best for high frequency can be dedicated to that, while an equally great low frequency design can be dedicated to that.

Active crossovers are commonly used in PA systems because they need to cover a specific area with each type of speaker. The line arrays don't see any bass and this allows them to handle more power, and the low end can be directed to the speakers that are designed for that, without wasting energy by sending high frequencies to them, or needing a passive crossover to filter it out, wasting energy in the process.

 

[fmw]

I finally upgraded my HT with the purchase of some new speakers. I replaced my mix matched batch (JBL L1 mains/Athena Center and Athena B1 surrounds) with JBL Studio L series (830/C1/810 in Cherry). My question is about Bi-amping. These are the first speakers I've owned with 4 binding posts. Is Bi-amping fact or audio BS?

Here's a little articly by yours truly for what it's worth.

http://www.foodieforums.com/otherimages/biamplification.htm

 

[OttoMatic]

Here's a little articly by yours truly for what it's worth.

There are some problems with that discussion.

Your claim of "It isn’t biamplification" is strange to me. Using two amps to drive one pair of speakers is, indeed, biamplification. To distinguish between the two, they are usually referred to as "active biamp" or "passive biamp". I understand what you are trying to say, but I don't think that trying to remove the definition is really helping make your point.

Adding more power by adding a second or third amplifier isn’t really helpful either. The problem is that the low frequency drivers in the speaker system use most of the amplifier power. The high frequency drivers don’t need much power at all – only milliwatts in fact. So adding the second amplifier doesn’t relieve the original amplifier of much work. You end up with one driver powered about like it was before and another driver – the high frequency one – with far more power than it can possibly use. You have achieved no improvement in isolation or control and you have done virtually nothing to help power the system either.

Well, I suppose it depends on a number of things. Consider the way the wiring is done inside the cabinet of the speaker (my input for "highs" goes to both a tweeter and a 5" driver, so it's gonna suck some power). Also consider the type of music being played. I would imagine that some classical music may play more toward the middle of the band, perhaps near a crossover point, and not be pushing a lot of bass. I also don't believe that the HF drivers only require "milliwatts". At high volumes, I believe it would be much more. At high volumes, biamping could make a difference (you could also achieve a similar increase in power simply by using a bigger amp in the first place -- I recognize that; but you can also get an increase in power by biamping.)

When talking about using two extra channels from a receiver for biamping, you say "the two amplifiers we want to use in this process are powered by the same power supply as all the others. So the power supply becomes the limiting factor in the system, not the number of amplifiers."

You fail to note that while being power supply limited is indeed one possibility, it's not the only possibility. In a properly designed amp, they power supply should easily supply enough power to drive all channels to their maximum outputs. Many amplifiers and receivers are designed with adequate power supplies, so the end user shouldn't run into the problem you are trying to describe.

In general, I agree with the idea that passive biamping doesn't do much. However, I think that the above points needed some clarification.

 

[fmw]

I don't. I think the article is accurate and useful as written. The reason the name passive biamplification is a poor description of of it is that you aren't biamplifying. You are using two amplifiers to power opposite ends of a crossover network. You can do it just as well with the same results with one amplifier. So I guess I disagree with the term passive biamplification and I prefer to call it powered biwiring which is what it is. If your argument is about terminology then use any terminology you like. I'll use any I like. The consumer audio business is so full of half truths and nonsense, somebody needs to call a spade a spade.

It doesn't matter whether the power supply is capable of driving all the amps to full power or not. The amplifier driving the high frequency side uses almost no power at all. It relieves the other amplifier of virtually nothing. The power supply spends more energy heating that amplifier than it does amplifying anything. If you think there is something to be gained by the process, you would have lots of company. But in the audio world that doesn't always mean much. I continue to try to keep the record straight. Sorry you don't like it.

As it turns out, I don't like it either. Coming to this forum should be recreational for me. It just ends up making me angry. Why don't you keep the record straight. I'll go do something else.

 

[OttoMatic]

If your argument is about terminology then use any terminology you like. I'll use any I like. The consumer audio business is so full of half truths and nonsense, somebody needs to call a spade a spade.

Well, you're the one that's tried to change the name of what we're doing here. I'm sure that if you present "powered biwiring" to forums, audio guys, etc., they won't understand what you're talking about until you break down and call it "passive biamping". I see no problem with calling it passive biamping. As I'm sure you know, the "bi" prefix usually means "two" (bicycle, bicentennial, etc.), and when biamping, you're now using two amplifiers. You're using a passive crossover network to do the filtering. So, "passive biamping" seems like a perfect term. It's like the guys that don't like the term "Christmas" trying to get it changed to "Yule Celebration" or "Winter Break" or whatever. We can agree to call it whatever we like, but I just really don't see any philosophical problem with calling it passive biamping.

It doesn't matter whether the power supply is capable of driving all the amps to full power or not.

Well, it does when you assert this type of thing:

So the power supply becomes the limiting factor in the system, not the number of amplifiers.

Please recognize that in the second sentence, you say that the power supply will become the limiting factor, and in the first you say it doesn't matter. I would say that if the power supply really is the limiting factor, then you have a potential concern. If the power supply is NOT the limiting factory, then there's nothing to be concerned about in that regard. Like I said, your link only provided one of those options, with it being the "bad" option.

Your argument above, though, is based on this fallacious assumption:

The amplifier driving the high frequency side uses almost no power at all.

How do you know this? How much power goes to a 5" driver and a tweeter when playing back a violin concerto?

It relieves the other amplifier of virtually nothing. The power supply spends more energy heating that amplifier than it does amplifying anything.

Are you sure of this? Wouldn't the reduced power requirements on amp #1 reduce its heat output accordingly? And since amp #2 is now doing "almost nothing", wouldn't its heat output also be "almost nothing"? Unless this is a Class A amp, the amp circuits themselves aren't going to get terribly warm unless they are being used. Some of your discussion seems as though it made sense to you when you were writing it, but it's more assumptions and personal beliefs.

If you think there is something to be gained by the process, you would have lots of company. But in the audio world that doesn't always mean much.

Well, I don't think there's much to be gained by it either, but I do believe that there is a measurable difference, from which some people may actually garner some slight benefit. But I think if you want to make a case against it, using handwaving type arguments isn't the best way to go about it.

Why don't you keep the record straight.

I'm trying, I'm trying...

 

[corey]

For most practicle purposes, mostly BS. Unless you are using low power tube amps, or have a very large space to fill, I wouldn't worry about it.

No one has asked yet: what amp/receiver are you using, and how big is your room?

 

[JJMP50]

For most practicle purposes, mostly BS. Unless you are using low power tube amps, or have a very large space to fill, I wouldn't worry about it.

No one has asked yet: what amp/receiver are you using, and how big is your room?

Yamaha 659 in a standard size living room. From the previous posts I doubt very much if I would benefit and it probably would be an effort to keep the wires hidden. Wifey issue. She says she cannot tell the difference from my old speakers although they look nicer (Cherry). She somewhat has a point when just watching broadcast TV even HD/Digital, but previously I only listened to music in stereo mode using the L1s because of the mismatched speakers (it seemed that the Athenas were a lot more sensitive than the old JBLs/played a lot louder and with a different voice) and my DVD concerts now sound a lot better with the matched studio L's.

 

[irishtom]

Passive bi-amping is the practice of using passive filters rather than active ones to split the signal between the preamp and amplifiers. As with active bi-amping no fullrange signal is sent to an amplifier and no passive crossovers are used at the speaker level. This is a very old practice dating back to the birth of high fidelity in motion picture theater sound.

The dubious practice of sending two fullrange signals to the legs of speaker level passive crossovers is often called "fool's bi-amping" by real bi-ampers. No doubt this practice evolved so new school audiophiles could throw the term "bi-amping" around.

 

[OttoMatic]

Passive bi-amping is the practice of using passive filters rather than active ones to split the signal between the preamp and amplifiers.

Yes, I forgot about that method. I would also consider that to be passive bi-amping.

I'd still argue that using filters in the speaker is also passive bi-amping, regardless of other derogatory names that might be assigned to it.