Bi-amping Rules


I wasn't sure if this question belongs in the amp or the speaker section but I figured I'll post it here. Those of you who have bi-amped your speakers, what's the general rule for deciding which amplifiers are better for low frequency vs. the high frequency drivers. I recognize an accurate answer will depend on the particular speakers and amp combinations but I'm looking for general rules of thumb from personal experiences and not application specific recommendations. For the sake of the argument, let's assume the amps are different but the gains on both amps can be adjusted if that matters. Thanks.
Convert?fit=crop&h=128&rotate=exif&w=128kalali
Give this a read before you decide to bi-amp. Generally tubes on the top and solid state on the bottom!
http://www.gcaudio.com/resources/howtos/biamping.html

Read the next to last paragraph in yogiboy’s link. IMHO, using different amps to bi-amp is just going down a dead end street and trying to get it to sound right will be like chasing a rainbow.

I, too, considered bi-amping, but now think a pair of Monoblocks  would be a better way to go. Introducing 2 different amps is a recipe for trouble/disapointment as there are too many variables.
While anecdotal indications are that there are certainly **some** cases where audiophiles have achieved fine results by bi-amping, in both passive and active configurations and by using different as well as identical amplifiers, I agree with the foregoing comments and the article that in the great majority of circumstances the corresponding funds are likely to be applied more constructively in other ways. And presumably and hopefully the designers of most high quality speakers have gone to great pains to try to make them sound as coherent as possible throughout the frequency range. Why risk undoing that by using different sounding amps?

Also, while I agree with most of what is said in the referenced article, I don’t quite agree with the following paragraph:
Ok, so what about just using two amplifiers and forgetting about the electronic crossover? Simply using two amplifiers is not true bi-amping and does not offer the same advantages; we still face the limitations of the passive crossover. What about the notion that bi-amping reduces stress on the amplifiers since they are powering only limited frequency ranges? That would be true in a true bi-amp configuration where the frequencies are split ahead of the amplifiers, but in a passive environment both amplifiers receive a full range signal from the preamp and dump that power into the speakers, regardless of whether one is connected to the tweeter or woofer inputs. The only benefit (and it marginal at best) is simply the additional power offered by the second amp.*
* There may be a bit more advantage obtained when one employs two identical amplifiers, one for each speaker – vertical bi-amping.
Passive biamping will in fact relieve the bass amplifier of having to deliver current and power above the frequency at which the low pass section of the speaker’s crossover has essentially completed its rolloff, and will relieve the mid/hi frequency amplifier of having to deliver current and power below the frequency at which the high pass section of the speaker’s crossover has essentially completed its rolloff.

HOWEVER, when it comes to passive bi-amping what seems to often not be realized is that since both amps have to output VOLTAGES corresponding to the full frequency range of the signal, using a very powerful solid state amp for the lows and a much lower powered tube amp for the mids/highs (as some audiophiles do) will probably result in much of the power capability of the higher powered amp being unusable. A much lower powered amp can be expected to generally have a much lower maximum output voltage capability than a much higher powered amp, which in a passive bi-amp arrangement (i.e., without a crossover "ahead" of the amps) means that how much of the power capability of the higher powered amp is usable will be limited by the clipping point (the maximum voltage capability) of the lower powered amp.

Good luck. Regards,
-- Al


Unless you have the exact model for both amps, don't bother.  If you're contemplating a purchase of 2 like amps...getting 1 good amp for a side  is better than 2 lesser ones...and certainly better than different models.
I passively Bi amp my Maggie 3.6's with a pair of David Berning ZH270 power amps. The result is much better sound from my  Maggies then using one amp. In fact I won't get 3.7's because with there series crossover you can't bi amp. I also when I was upgrating one of my bernings I thru a vtl ST80 in to replace one berning and it sounded just as good. One nice things about the Berning amps is they have volume controls so I can adjust bass/mid levels versus the treble level. 
Alan
Thanks for all the inputs. I have experimented bi-amping my Aerius i  using few different amps, all SS, and could never get it to sound right or better than a single (good) amp.
Kalali, my dealer recommended a pair of Aesthetix Atlas stereo amp for vertical bi-amping.  It's a hybrid amp with a built in crossover. 

I am working on a plan to try them out in next month or so. 
Agree with those who say that you really have to have an active bi-amp system for it to make much sense.  Some benefits can be achieved with a passive vertical bi-amp which of course assumes you are using two identical amps.  Otherwise, you need an active crossover.  In my system, active crossover low passes the bass below about 8O hz to a high power class D stereo amp then to a pair of 10" woofers for each channel; and high passes the mids and highs to a tube amp that drives the (almost) full range drivers. This does introduce lots of complexity and requires lots of outlets and cables.  The system to my ears sounds wonderful but there are many places for gremlins to rear their ugly little heads, which per Murphy, happens on occasion. 

In my case, the music I listen to does not have an overwhelming amount of very low bass content so most of the information is reproduced by the tube amp.  The class D amp is really for all practical purposes, a sub-woofer amp and in fact, the active crossover I use (NHT X-1) was designed primarily to use ahead of a subwoofer. 
there are four descent ways:

1. The best one is not to biamp at all and use single amplifier of sufficient power or monoblocks.
2. Active speakers are usually bi-amplified or can accommodate an external amplifier along with built-in, because they have ELECTRONIC CROSSOVER
3. Replacing built-in crossover with electronic and use same or different amps
4. Mating amps of the same brand with existing passive built-in crossover.


bi-amping my B&W 803Ds, Kebshcul 35W per channel mono blocks on the mids up, and crown 1502 on the bottom end, sounds wonderful, I think the key may be that the crown has input sensitivity, can dial it in.
jrhud, what preamp you're using? And are you using an external crossover? 

I am looking bi-amping my 800D2's.  

When you bi-amp, you become a speaker designer, like it or not.  There was a time when it was a bit of a pig in a poke, but the possibilities were always there.  The miniDSP 2x4 active crossover only costs about $110 and it allows you to do DSP EQ on your system.  No matter the amps or the room you're using, you can measure what's coming out and create a correction filter to apply to the miniDSP.  

This means you can try whatever amps you like and just see how it goes.  When an amp only has a single driver as its load, it can do a whole lot better than you realize.  This also gives you the chance to mix tubes and solid state if you like.  Many have done that with great results.  Tweeters and mid-range drivers require little power.  Most of the power being used in the big systems is lost in the crossovers as well as being used to drive the low end.  And a solid state low end is just so much stronger than most tube amps as well.

Or you can be like most who just prefer to spend many, many thousands of dollars because someone told them they should trust the designers because they charge so much they must be good.  Why should you trust your own ears?
So given three way speakers, why stop at bi-amping when you can tri-amp? I am of course being facetious. Please let us know how this turns out.

I can’t tell y’all how many times in the last 40 years of my career in A/V people have always missed the first fundamental. They pile up a stack of humming electronics and wonder why their performance is underwhelming. Think about power first. Add up the greedy electrical cravings of all the equipment - then spot it all an additional 25%. You need the available power to do what you want and give the amps a chance to breath. Keep in mind a 15amp a/c circuit has 1800 watts available and a 20amp has only 2,400 (both with 120volt US standard). And be sure to add up every bit on that circuit - be sure to include lamps, clocks, and chair warmers!

Two 1,000 watt per channel amps, preamp, tuner, DVD, computer, cable box, D/A, equalizers, monitors, and that neon lit beer sign with the dogs playing poker are going to suck dry a 15amp circuit. Your result will be a rather anemic.

For me..... low end must have high damping factor, tubes on highs SS on bottom and yes tramping is even beter. I've even heard quad and more amping. Basically I feel it about control.
Let's leave PA-systems out of the discussion. In them you want efficiency and the most bang for the buck at the least weight to haul around. You also have a brain behind the console to tweak the sound as he pleases and the music is produced rather than reproduced so there is no original to compare with. That is not to say that you don't need good sounding amps etc to get the venue rockin' and a satisfied audience that leaves saying that the sound system was the best they had ever heard...

Can you use different amps for hi/lo in a HiFi-system? Yes! But I recommend using similar amps. I used Nakamichi N620+N420+EC100 for many years and the sound was very balanced. Of course this configuration was intended by the manufacturer. My guess is that eg Linn LK140+LK85 would perform even better as they are also two versions of the same series of amps but with different power ratings.

If your speakers are simple 2-way with just a coil and a capacitor for filtering my recommendation is using two identical stereo-amps with one placed behind each speaker and low level passive x-overs that only employs 2 resistors and 2 capacitors for each channel. This is very simple, keeps the speaker cables short and leaves most of the PSU in the amps available for the woofers.

If the speakers have complex filters they usually not only divides the range and adjust levels but also includes phase correction components that may require some kind of delay line in the active x-over and you are in for a big challenge...
I prefer two identical amps and preamps. This way, I can adjust the bass or recordings lacking such. I tried alternate ideas, but there is a tradeoff with phasing. 
I bi-amp with two identical amps, and I mean identical.  Despite being about 25 years old they are 5 numbers apart (serial number) built on the same day, same shift, same parts bins.  One amp runs the left speaker and one the right.  The left channel of each drives the woofer module and the right the electrostatic panel of a very power hungry vintage pair of Acoustats. 
@danvignau I suggest using an EQ instead of touching the filter levels. Behringer have one that is digitally controlled 1/3 octave where you can save settings and recall them anytime you like and they are not very expensive. For normal use you will just of course leave it in "By-Pass" and if you want to keep it completely out of the signal chain simply connect it to the Tape Monitor Loop of the Pre-amp.

Good recordings does not in general need any altering but eg an old VHS- or cassette-tape might benefit a lot from some tweaking/restoration. You might also like to call it a REMASTERING and there is NOTHING WRONG with trying to get the most out of a crappy recording using whatever apparatus you like! Including EQ, Noise Reduction, Expanders or Sonic Enhancers etc... It is not "puristic" but it might sound a h_ll of a lot better and if that is the only recording you have there is NOTHING WRONG with trying to restore it "to its former glory" using what ever means you have available!

BUT: Don't touch the filters! They are part of the Amp-Speaker combination and should NEVER be changed once they are properly aligned! Of course that is just my humble opinion and you are of course free to turn any knob you want... :-)

@midareff1 I agree 100%! Two identical stereo-amps with one for each channel is DEFINITELY the best way to go when Bi-Amping...
BTW: I've gone back to passive x-overs but not with the original components in the filters but instead 14AWG Jantzen coils and their Superior Red Z-Caps.

Does this sound better or worse than my active Nakamichi arrangement?
Hard to tell since what is best since the amps and cables have also been altered.
At lower levels YES! But if I try to "wake up my neighbors": NO!

I ran the system in passive configuration with a Linn Majik-I and THAT sounded a h_ll of a lot better than the Naka combination but that little VERY NICE amplifier just did not have the oumff since it only produced 2x33W at 8ohms and that is not enough to drive my speakers to more than approximately 85dB.

So what is best? Active or passive x-overs?
There is simply no correct answer to this question!
They both have their uses and issues....

For high power systems: Go active!
For low level systems: Leave the speaker design to the manufacturer...

Of course it is a free world and anyone is free to do anything they want but the original question in this thread was about using different amps in Bi-Amp configuration and my answer is: YES, you can do that!

BUT: YOU will become a SPEAKER DESIGNER if you try!

Nothing wrong with that! There are thousand of them out there and you might be just as good as they are but believe me when I say that it is NOT an easy thing to design a good amp/speaker system.

It all boils down to what you want to do! Cracking the skulls of 75 000 people at an arena or sit at home listen to a singer-songwriter at "bedtime" levels?

If what you want is the first alternative: Go active!
If it is the second and you want to keep it simple: Don't bother!

If you are anywhere in between it is all up to you! :-)
Hi: Back in the Nineties; I used a Bi-Amp set up. I was using some Adcom stuff the GFP565 as it has three sets of out puts. I used a GFA 535 with about 60watts/Channel. So, When I bought some Polk Audio SDA SRS 2.2 speakers, I needed a bigger amp! I stumbled into a Great deal on a Bryston  4B they were rated at 200watts/ channel then. Even then I was aware of Polk tweeters blowing fairly easy with too much power. My previous speakers were DCM Time Windows (first series). What I did was put the 4B into the "Bass" end of the Polks;(6x 6 1/2 mid woofers into a 15" sub bass radiator each speaker), then used the GFA 535 to run the tweeters and the Time Windows. I never blew any tweeters! That set up had 10; yes ten tweeters. The bonus was the best Holographic stereo soundstage I have ever had or heard. I had the DCMs on the side walls 6-8 feet from the Polks and Image at about 270 degrees in front of me. My case was I got new gear and did not want to part with the old gear yet? Once you know a sonic signature in your set up you can use that to get "other" results. When I played Jimi Hendrix's "Purple Haze" he sounded outside the window singing in and between the two right speakers. I told people this and when I played it they were amazed? I guess what I am getting at is A lot of previous people are right on " Bi Amping Blues". I wanted to experiment. Out of fear of blowing tweeters and  having Extra Gear, so I Bi Amped for fun, and got an extra Bonus in soundstage. That set up was the most fun to listen to of any set up I have had. It unlocked recordings secret information; and that was fun. I think you take all the information and experiment? Something does not work, try something else? Gear is easy to sell and buy now. You can always follow someone else's pattern or electronic IQ, mix and match until YOU are happy.   B
What I don't get about the entire concept of using SS for low freq and tubes for high freq is there will always be a dramatic power differential.  So how can you begin to balance out the sound levels coming from your tweeter and woofer when the amps delivering the signal are themselves delivering noticeable different volumes?  To me that means that the tube/SS suggestion has always seemed sort of useless unless you automatically include an electronic crossover and the ability the sound balance.  Am I missing something here?
aewhistory
What I don't get about the entire concept of using SS for low freq and tubes for high freq is there will always be a dramatic power differential.  So how can you begin to balance out the sound levels coming from your tweeter and woofer when the amps delivering the signal are themselves delivering noticeable different volumes?
The issue isn't one of a power differential between the two amplifiers or whether one is solid state and one is tube. The issue arises when the amplifiers have different amounts of gain, independent of power.  That's why you use an active crossover to balance them out.
At the minimum, you need to be able to control the gain of one of the amps in order to make the bi-amp approach work properly. Even then, the results can be very mixed. My NAD preamp allows for changing the gain on the second pre-out output. Some amps like my Mac MC2200 also have separate gain controls for left and right channels. But gain aside, I still don't quite understand the need for an outboard crossover to control the frequency between the HF and LF sections since both amps are feeding full range and each section of the speaker still operates within its own design frequency range.
russbutton66 posts07-29-2016 8:45pmWhen you bi-amp, you become a speaker designer, like it or not.

Can you share a number of your 'supply' dealer so I can try it too?

kalali
But gain aside, I still don't quite understand the need for an outboard crossover to control the frequency between the HF and LF sections since both amps are feeding full range and each section of the speaker still operates within its own design frequency range.
When biamping, the active crossover has separate low and hi frequency outputs, which then feed the amplifiers. The amplifiers don't run full range. This, imo, is the only way to get maximum benefit from biamplification.

czarivey
When you bi-amp, you become a speaker designer, like it or not.
Not necessarily. Some speaker systems are designed to be biamplified.

Post removed 
But gain aside, I still don't quite understand the need for an outboard crossover to control the frequency between the HF and LF sections since both amps are feeding full range and each section of the speaker still operates within its own design frequency range.
kalali,
the advantage of an external x-over lies in the fact that you can tweak the x-over slopes to suit your listening needs &/or your room.
In an in-built (in the speaker cabinet) x-over the designer does this job for you using his design skill & keeping in mind 99% of the population so that his speakers work in a wide range of room sizes. So, it's often the best compromise.
With an external x-over you can change the slope (-6dB or -12dB or -24dB or -48dB & so on) make the speaker tuned to your room.
Plus, some of the factory x-overs are very power hungry. Using an ext x-over you can overcome this shortfall & make it easier for your amp to drive your speakers.
You can also upgrade all the components in your ext x-over & make it as transparent sounding as your wallet will allow.
Plus another major thing these days - some digital x-overs will also allow you to do room correction & bring your speaker closer to being a time-coherent speaker (which is a big deal, i.e. being time coherent). The merits of room & speaker correction towards making the speaker time-coherent are huge. One listen & you will know.
hope this clarifies.....
A couple of comments and clarifications regarding today’s posts in this thread:

In the case of passive biamping, i.e., biamping without an electronic crossover "ahead" of the power amps, it is of course correct that what has to be matched in some manner is the gain of the two amps (gain being the ratio of an amplifier’s output voltage to its input voltage, for a given load impedance), not their maximum power ratings. While amplifier gain is often unspecified, if Stereophile has reviewed the product the measurements section of the review will usually indicate the gain, or it may be determined by contacting the manufacturer, or it can be calculated to a reasonably good approximation from the max power rating and sensitivity specs that are usually provided, per the methodology indicated in the second of my posts dated 3-10-2012 in this thread.

Passive biamping will greatly minimize the amount of low frequency CURRENT and POWER that is supplied by the high frequency amp, and will greatly minimize the amount of high frequency CURRENT and POWER that is supplied by the low frequency amp. However the VOLTAGE that will be supplied by each of the amps will correspond to the full frequency range of the signal. As I indicated in the last paragraph of my post earlier in this thread, a consequence of that (which would be avoided if an electronic crossover is used) is that if there is a **large** disparity in the power capabilities of the two amps, much of the power capability of the higher powered amp will not be able to be utilized without driving the lower powered amp into clipping.

Regards,
-- Al

In the case of passive biamping, i.e., biamping without an electronic crossover "ahead" of the power amps, it is of course correct that what has to be matched in some manner is the gain of the two amps (gain being the ratio of an amplifier’s output voltage to its input voltage, for a given load impedance), not their maximum power ratings.

In the context of a passive crosover, while it seems as a simple thing to just match the gain of the two "different" amplifiers used in biamping, it is much more than that. Two different amplifiers will never have the same timing and phase response in the music reproduction. So in effect you are feeding two differently timed signals to the two drivers (LF and HF) and also both signals vary in their respective phasi-ness. The final output will be a sound where the drivers do not integrate and sing as one. The HF and LF will be all there but they will sound like individuals. All the work done at the crossover to marry the drivers are nearly lost. The same happens when biwiring with different cables for LF and HF.
If you bring in the tonality aspect it gets even more complex. Imagine the lower notes of the piano coming from one amplifier and the higher notes from another amplifier of a different make (which means different voice)! Ultimately it will also mean the fundamental notes are generated by one amplifier and the higher order harmonics by a totally different amplifier. Will the fundamental and its harmonics now sound like it is coming from the same note ? It is ultimately a "cooked" sound to say the least.
Pani, to be sure it's clear, my comment that you quoted was not intended to imply anything inconsistent with your comments.  And personally I am in essential agreement with everything you have said above.  From my post in this thread dated 7-25-2016:
While anecdotal indications are that there are certainly **some** cases where audiophiles have achieved fine results by bi-amping, in both passive and active configurations and by using different as well as identical amplifiers, I agree with the foregoing comments and the article that in the great majority of circumstances the corresponding funds are likely to be applied more constructively in other ways. And presumably and hopefully the designers of most high quality speakers have gone to great pains to try to make them sound as coherent as possible throughout the frequency range. Why risk undoing that by using different sounding amps?
Regards,
-- Al

I read through this thread and maybe I missed it but what about amps that have been designed to work together in a bi-amp configuration?
I have a Marantz PM-11s3 and Marantz talks about how these have been designed to work in tandem with each other in a bi-amp configuration.
The PM-11s3 owners manual shows how to connect two and configure them with one being the control amp/pre and the other the slave unit providing just the amp and locking out its pre.
I wonder if these types of designs work well or is it just a sales gimmick?