# Bi-Amping questions



## Richard in Idaho (Dec 16, 2010)

My Pioneer Elite vsx-30 allows for bi-amping using the front and surround back speaker terminals.
Questions assuming that I have bi-ampable speakers.

1. Will the AVR actually be able to deliver more power to the speakers.
2. Does dividing the speaker into High and low parts by removing the jumper plate between the two sets of terminals change the impedance that the avr sees.

Thanks


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## tonyvdb (Sep 5, 2007)

Hello, The power difference between bi amping or not is very little. Remember that its the lower frequencies that draw the power not the highs.
And no, the ohms will stay close to the same even in bi amp mode.


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## bambino (Feb 21, 2010)

I have personally never noticed a differance, but several folks say they can so it's somewhat of a debatable topic.


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## Coytee (May 7, 2010)

Richard in Idaho said:


> My Pioneer Elite vsx-30 allows for bi-amping using the front and surround back speaker terminals.
> Questions assuming that I have bi-ampable speakers.
> 
> 1. Will the AVR actually be able to deliver more power to the speakers.
> ...


Some might swear by it... I'm in the camp that this won't get you much improvement as long as everything is working as it should. I think one key thought is, are you using a decent size wire for your application. If you are then no gains, if you are not then maybe the additional wire will help (since that would take it closer to 'proper sized')

Traditional biamping is having an active crossover after your preamp and before your power amps. It will divide the signal itself into a lower and higher range so that each amp will only have to amplify a section of the signal.

You can mix/match some biamping though... (I use an active in my system so I biamp in the traditional way)

Anyways.... you can mix/match a bit... I once took my 2-way speakers apart, keeping the bass bin hooked up. I replaced my top horn with a smaller 3-way speaker giving me four drivers (when I traditionally have two)

I used my active to split the signal around 100hz and fed that to my woofer box and everything above 100hz went to my 3-way speaker, allowing the passive inside of it to further divide the signal to each driver.

So now I'm "biamping" (since I had two channels of amplification) a 4-way speaker.

Running another pair of wires in parallel to the first I think is called biwiring (?)


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## jackfish (Dec 27, 2006)

1. Yes, an amplifier channel is dedicated to each +/- output the same as if you were connecting two pairs of individual loudspeakers. So if your AVR is rated for 80 watts per channel for the front and back surround channels it will supply the rated power to each of those channels *potentially* doubling the power available to the speaker in a bi-amp configuration as opposed to just connected to one channel with the speaker input terminals bridged. However, as mentioned before the low frequency section of the speaker will draw more power. But, in your passive bi-amp scenario the low frequency section would now have its own channel rather than sharing power with the high/mid frequency section. Even though the channel for the high/mid frequency section is likely to be under utilized compared to the low frequency section, there will be additional power available for high/mid frequency transient peaks.
2. The impedance remains essentially the same.


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## Coytee (May 7, 2010)

jackfish said:


> 1. Yes, an amplifier channel is dedicated to each output the same as if you were connecting two pairs of individual loudspeakers. So if your AVR is rated for 80 watts per channel for the front and back surround channels it will supply the rated power to each of those channels *potentially* doubling the power available to the speaker in a bi-amp configuration as opposed to just connected to one channel with the speaker input terminals bridged. However, as mentioned before the low frequency section of the speaker will draw more power. But, in your passive bi-amp scenario the low frequency section would now have its own channel rather than sharing power with the high/mid frequency section. Even though the channel for the high/mid frequency section is likely to be under utilized compared to the low frequency section, there will be additional power available for high/mid frequency transient peaks.
> 2. The impedance remains essentially the same.


I find that interesting. I had never ever biamped and didn't know much about it. I then jumped 100% into a 2-way amped system using an active crossover. Because of my lack of knowledge, I ended up asking lots of various questions.

One of them was essentially, "if I put a 200 watt amp on my woofers and a 200 watt amp on my tweeter will I end up with a 200 watt system or a 400 watt system?"

My recollection of the answer was I'd have a 200 watt system (though with perhaps more headroom) and not a 400 watt. Meaning, they were not additive in power. 

With his speakers being "bi-amp able" I would have more questions. I also have a pair of speakers that can be biamped. You don't move a jumper but rather, change a pinned "plug" that goes on the bottom. That said, my speaker that is biampable then still requires an active in the signal chain to divide the signal between two amps.

Is that what he has or, does he have something where both legs still go to his passive crossover?

My understanding is, if he's got TWO full range signals going to his passive crossover then his low frequency part of the crossover is bleeding off the high frequency signal as heat (wasted headroom) and the high frequency part of the crossover is bleeding off the low frequency signals as heat (wasted headroom) leaving him ultimately with essentially the same that he started with.

If however, he was able to slip an active crossover in there and actually divide the signal, his woofer amp and woofers would then be ONLY trying to reproduce the low frequencies and not wasting any bandwidth on upper frequencies. Alternatively, his tweeter amp and tweeters would be then ONLY trying to reproduce the upper spectrum and not wasting the amps bandwidth on the lower frequencies.


I'm not an engineer (farrrrrrrrrrrrrrrrrrrr from it!) and I did not stay at a Holiday Inn last night so I don't know all the answers. I'm merely parroting back some of my understanding that I've come to grips with after asking a lot of questions myself on my path to biamping with an active crossover.

Actually....the more I think about it from one perspective (I can be retentive at times), I guess he IS "bi-amping" if he is by definition, using two amps to drive his speakers. Even if they're full signal and have of each leg is getting wasted in the crossover.... I guess it's still biamping!


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## jackfish (Dec 27, 2006)

Ask your self what happens to the current from a single amplifier channel of a given rated power applied to speakers with the high/mid frequency section and low frequency section bridged and how that is different from two amplifer channels of a given power applied to speakers with one channel connected only to the high/mid frequency section and one channel connected only to the low frequency section (terminal bridge removed). Do you really think the power equivalent to one amplifier channel is lost to heat dissipation due to the crossover in the bi-amp scenario? If so, then how much power is lost due to the crossover with a single amplifier channel of a given rated power applied to speakers with the high/mid frequency section and low frequency section bridged? Hmmmm....


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## Coytee (May 7, 2010)

jackfish said:


> Ask your self what happens to the current from a single amplifier channel of a given rated power applied to speakers with the high/mid frequency section and low frequency section bridged and how that is different from two amplifer channels of a given power applied to speakers with one channel connected only to the high/mid frequency section and one channel connected only to the low frequency section (terminal bridge removed). Do you really think the power equivalent to one amplifier channel is lost to heat dissipation due to the crossover in the bi-amp scenario? If so, then how much power is lost due to the crossover with a single amplifier channel of a given rated power applied to speakers with the high/mid frequency section and low frequency section bridged? Hmmmm....


I've been asking myself... and freely admit I'm clueless!

I've also mentioned that I'm not an engineer so, perhaps you'll clarify your question for me in more simple terms?

(just pretend you're talking to your 6 year old...and no, I'm not trying to be an idiot... just trying to get it clarified)

To respond to _one_ of your questions, I understand that in MY circumstance, there is a 1 or 2 db "insertion loss" when a passive crossover is used instead of an active. I have no idea how 1 or 2 db equates to any electronic losses.


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## jackfish (Dec 27, 2006)

Well, I believe it is understood that as much as a 10 dB change in volume is considered to be perceived as a doubling in volume, most people will perceive a minimum volume change of 1 dB, and 3 dB being perceived as being slightly louder. Remember also that the decibel scale is not linear and the relationship between amplifier power and volume increases is logarithmically. Hence, if it takes a ten times increase in amplifier power to yield a subjective doubling of volume (10 dB), and a doubling of amplifier power yields a 3 dB increase in volume, a 2 dB loss in volume due to a crossover could equate to an effective loss of a third of amplifier power. So there would still be a marginal increase in power from passive bi-amping. However, my point was there is power loss due to the crossover in both scenarios (single channel, bridged hi-lo vs. two channels, one each for hi-lo) so it would be relative, meaning there would still be an effective increase of power with passive bi-amping.


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## DrWho (Sep 27, 2006)

Amplifiers are voltage amplifying devices, so the actual current being drawn is irrelevant (provided the amplifier is capable of delivering enough). This is why we talk about being "2ohm stable" etc...lower impedances require more current, so there is a minimum that we can deliver the same voltage to.

When you use the biamp feature on the amplifier, you're not reducing the amount of bandwidth coming out of each amplifier. Both amps deliver the entire bandwidth of the signal. This means you get no increase in voltage headroom by having a separate amp per section. In other words, your voltage clip point does not change and you do not get the apparent increase in power by reducing the bandwidth. More importantly, you're not increasing the max SPL of the total system...which is ultimately the goal of having more power available.

It should also be mentioned that in your typical AVR, the power supply (shared by all of the outputs) is _usually_ the limiting factor...thus why the power for 2 channels driven is always higher than the power for all channels driven. Because of this, you're not really buying more headroom...even if you somehow divided the bandwidth.

That said, technically the tweeter impedance is high at low frequencies (due to the passive xover) and the woofer impedance is high at high frequencies (again due to the passive xover), so there is a decrease in the amount of current being delivered for out of band signals. Again, let me stress that these amplifiers are voltage amplifying devices so the actual current is just an issue of having enough available, but you might buy yourself a little bit of thermal headroom since the heating will be spread out across two devices. Because of this, some of the distortions might take on a slightly different flavor when you start getting into the dominate region of distortion...but should we really be running near the point at which the distortion timbre starts to matter? Why not get a properly sized amplifier to begin with? (or use more efficient speakers).

I'm a huge fan of proper bi-amping, but the biggest benefit is getting rid of the passive xover and all the tradeoffs that come with using passives. Other benefits include dividing the bandwidth before the amplifiers and the option to do time-alignment. It's also nice that the filters don't modulate and steeper slopes are possible when running an active xover.


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## Coytee (May 7, 2010)

Understood... so let me ask this...

Which would give anyone more volume? (presuming the speakers are rated for it and don't blow up!)

If we take a speaker as suggested above and do the following:

1. Remove said jumpers and apply say, 200 watts to the bottom end and 200 watts to the upper end or
2. Replace said jumpers and apply a 400 watt amp

Are you suggesting that the end result would be the SAME?

I would have speculated the 400 watt amp would give more power/headroom than the two 200's

?


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## Coytee (May 7, 2010)

Dr. Who slipped in between my comment (it was not directed at you Dr. Who). Thanks for your input


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## jackfish (Dec 27, 2006)

There you go! Thank you for the concise explanation. My previously limited and erroneous understanding has been greatly improved upon. It obviously remains limited. Thanks again.


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## gsmollin (Apr 25, 2006)

For non-technical consumers, the way to acquire bi-amplified speakers is to buy active studio monitors. The difficult job of designing the electronic crossovers to give phase-coherence at the crossover frequency has been accomplished.

For the hobbyist or technical consumer, bi-amping is a great way to achieve significantly more power bandwidth from your equipment. Di- or tri-secting the bandwidth allows the amplifiers to avoid clipping and distortion products that would be spread from bass to treble frequencies without it. The drivers are directly connected to an amplifier and benefit from the greater damping ratio. Active crossovers can be fine tuned to tweak phase responses in ways that are not practical in passive crossovers.

To answer an early question about power sharing in bi-amped systems: Power adds quadratically in a wideband amplifier. So if a 1 W signal is present at bass frequencies, before a passive crossover, and I add a 1 W treble signal to that, I need a 4 W amplifier to reproduce this signal without clipping. The crossover splits the signal and two, 1 W signals will be reproduced, one at the woofer and one at the tweeter. In an active-crossover, bi-amplified system, the two signals are split before the power amplifier, so two, 1 W amplifiers are required to reproduce the two signals. So two, 1W amplifiers add up to be equivalent to a 4 W amplifier, in this example. Extending this to program material requires us to choose crossover frequencies so that the energy in the program is spread evenly. Unfortunately, program material is bass-heavy and an equal division is not possible in the best systems. So the bass amplifier has to be pretty big anyway. However, clipping in the bass amp will not spread to the midrange and treble, and this is a great advantage of bi-amplified systems with narrow-band power amplifiers.

Bi-amplified systems that use a passive crossover after the power amplifier achieve little or no advantage over single amplifiers.


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## Coytee (May 7, 2010)

The scary thing is I followed most of that! :unbelievable:


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## kflory (Feb 6, 2010)

I run my system bi-amped and highly recommended if you can invest the time (I am still working on mine ).

But it is not a simple undertaking, so you need to be prepared to invest the time and do some engineering because you are essentially re-designing the speakers to some extent as you removed the passive cross over and replace it with the active crossover.

ESP has what I consider to be some very good info on bi-amping and explains the principles pretty well if anyone is interested:
http://sound.westhost.com/bi-amp.htm. 

There was some discussion here in this thread on the power that are explained pretty well here.

For what it is worth, my experience is largely documented here. As you can see I still have not posted my final crossover settings because I still have some pending experiments/tweaking I want to do that I have not gotten back to it yet, but I am extremely happy with the results.

I would also add that it is not just about more power providing higher volumes, but really allows the amplifier to control the driver which is improved when you eliminate the passive components between the amp and the driver.


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## tonyvdb (Sep 5, 2007)

You will get better results if you just use an external amp thats rated higher than what the speakers can handle and dont bother to bi-amp at all. Most of the time the "audible" difference you hear is just in your head or the fact the the receivers amps are simply not up to the task of driving them properly in the first place and you are hearing distortion caused by lack of power.


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## mjcmt (Aug 30, 2010)

The difference you may notice w/ bi-amping using an AVR is going to be small, generally yielding better isolation between lows and highs. AVRs usually use one power supply for all the channels (not necessarily a robust one either), so the advantage you will notice will be similar to bi-wiring (again depending on the quality of your AVR). 
A better bi-amping scenario will be to use a stereo amp for each speaker, therefore each speaker will be powered with it's own amp, for more robust sound and articulation, because only one of the 2 channels is powering the bass driver, therefore easing the demand on the stereo amps power supply. Even one mono block amp per channel is going to be an upgrade from and AVR.


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## Coytee (May 7, 2010)

Also when you're biamping (with an active in the chain) you can mix/match various types of amps. I used to have a 100 watt McIntosh MC-2102 (tube power) amp on my top horns mated with a Crown K2 for my bottom horns.

Later I sold the McIntosh and used a Viva 300B SET tube amp for my top horn while still keeping the Crown K2's for my bottom. I couldn't crank things as much since the 300B pooped out around 15 watts instead of the near 400/500 that the Crown offered HOWEVER, when staying in the range of the 300B, it was a very sweet sound.

I actually noticed some more spatial cues with that amp than some of the other tube amps I had used.


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## Richard in Idaho (Dec 16, 2010)

Thanks to everyone who posted here.

In doing research on speakers I came across the following regards the impedance part of my question.

This is on the Jaton web site

Impedance 4 Ohms @ Single Amplification
8 Ohms @ Bi-Amplification

Some here have said that the impedance would not change. Why would the Jaton change form 4 to 8 if others do not.

The manual for my AVR says that the impedance should be from 6 to 16.


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