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I posted a similar post under carver-tfms but thought it might be better to make it more general.


I'm thinking of bi-amping my Kef Reference 3 speakers using 2 separate 2-channel amps. When doing this how important, if at all, is it to match the amps? It may not be feasible for me to get identical models. If they are not identical how close should they be in power output? My current carver amp is 350 w/channel into 4 ohms.


I'm thinking I can use one amp for bass on both speakers and the other for mid/highs?


Thanks for your help.
 

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The high side amp may not need as much power. That may depend on the crossover though. So it's not known, to me anyway, how much amp power you need for the high side. If you had at least half the power, I would not be surprised to find that was adequate, but that's a guess.


I would definitely use one amp for the low side and the other for the high side, because if there were audible differences, that would be better.
 

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There's some debate on how much and how to divide the signals (surprise). Rule of thumb is that the highs need perhaps 1/3 - 1/4 the power of the bass, but as MichaelJHuman said it depends on the crossover, among other things.


For dividing the amps, the two main camps for two-channel amps are:


1. Use two identical amps. This may waste power on the highs, but now you use one (stereo) amp for each speaker, totally eliminating crosstalk in the amp channels (though the lows can still modulate the highs in each amp) and enabling short speaker cables (and longer interconnects, which have less sonic impact than longer speaker cables).


2. Optimize the amps by choosing a beefy bass amp with high power, high damping, etc. and a HF amp for best sound with lower power (saving money and energy). This means longer speaker cables and perhaps more L/R crosstalk, though now LF peaks will not modulate the HF signals inside the amp via the power supply (or whatever).


I have done it both ways, as well as used all monoblocks and multichannel amps, and am not sure it really makes that much difference as long as there's enough power for everything. Crosstalk is in the mud for most modern amps; measurements I made on a number of amps years ago showed only minor crosstalk though using a full-scale LF tone I could see a HF (1 - 10 kHz) tone slightly amplitude modulated. Very amp-dependent.


Personally, I like one amp per speaker to shorten the speaker wire runs, though my last biamped system went the other way (big bass amp, smaller mid/high amp). A lot of it is probably just personal preference. - Don
 

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Of course, ideally, you would remove the speaker crossovers completely (the one dealing with bass to mid/high,) and get an active crossover
 

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I hope you realize that using a single X wattage amp for the whole speaker will provide the SAME amount of power to each component as two separate amps sending X wattage to that speaker. It will NOT double the power, if that's what you're hoping to accomplish.


The only way to add (possibly double) power to the speaker would be by bridging the amp channels and passing the bridged power through a single connection to the speaker (or switching to active crossovers in lieu of those already in the speaker, as Michael suggested).


Passive bi-amping is essentially pointless...
 

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@pale... don and michael were referring to an active setup...



i know for sure don is, because he's still mad at me for telling him about the whole passive bi-amping thing that people try to do...
and i know for sure michael is, because i've seen him on this road before...



imo, in an active setup, i'd lean "small for small and big for big"... but i've only done a few, and all of them in cars...


but that's an imo, and as don points out, there's no real "wrong" way... it's a LOT easier to mess up the xover than the amplification (ask me how i know
)...


op, you DO understand that you need an active crossover before the amplifiers and that you must remove the passive crossover network within the speaker itself, correct?
 

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Aaaaarrrrggggghhhhhh... Thanks Chris, I still don't get the whole "passive bi-amping" thing. Yes, I meant, and probably always will, active bi-amping. I am pretty sure any other kind is worthless and a sin against nature, leads to cats and dogs sleeping together, and other such malarky...
- Don
 

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Right, if it was not clear, active biamping is non trivial. You have to use an active crossover, which would cost money, and you would have to modify your speakers which is far from trivial (and would almost certainly void the warranty.) There are advantages to it, which Rodd Elliott explains in an article online (his claim being that you sort of get power for free, my brain is too tired to explain why - or maybe I simply don't understand it enough



Let's assume you don't want to go down that route...


So you are then doing passive biamping. The reason for the term passive, is that you are using "passive" crossovers as opposed to electronic (least I think that's the origin of the term.)


If you are using two amplifiers, and your power is amp limited, not wall socket limited, adding an amp can definitely increase power. However, it's probably not double the power because the high frequency side of your speakers won't need half the power most likely.


And of course, biamping will do you no good at all, if you are not actually running out of power (clipping,) with your current setup.
 

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Quote:
Originally Posted by MichaelJHuman /forum/post/19649533


So you are then doing passive biamping. The reason for the term passive, is that you are using "passive" crossovers as opposed to electronic (least I think that's the origin of the term.)

Indeed, that is true but the significant issue is where the crossover is placed, before (line-level) or after (speaker-level) the amps. I have built passive line-level networks.
 

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Quote:
Originally Posted by Kal Rubinson /forum/post/19649591


Indeed, that is true but the significant issue is where the crossover is placed, before (line-level) or after (speaker-level) the amps. I have built passive line-level networks.

Thanks for the clarification
 

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Have you listened to a bi-amp system?

Before spending additional $ for more amplifiers and x-overs, you might want to audition a bi-amp system..

You could likely find out that any audible marginal gain..

May not be worth the expense and/or time..


Just my $0.02...
 

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Quote:
Originally Posted by M Code /forum/post/19649802


Have you listened to a bi-amp system?

Before spending additional $ for more amplifiers and x-overs, you might want to audition a bi-amp system..

You could likely find out that any audible marginal gain..

May not be worth the expense and/or time..


Just my $0.02...

What kind of wimpy logic is that. Think Tim on Tool Time. More power!



I have not ever heard a bi-amp system, but logic and math have always suggested it's not a great use of money. That's just my own opinion/logic.
 

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I certainly don't claim to be any kind of authority on the subject, so I thought I'd pass this along FWIW -


Passive bi-amping is known in some audio circles as "fools bi-amping". It is claimed that any power increase that you'd hope to realize is dissapated (as heat) in the built-in crossover before it ever gets to the speaker.


It has been pointed out that speaker manufacturers started incorporating dual binding posts with removable straps as a sales gimmick when some "audiophiles" began to employ the highly questionable practice of "bi-wiring". After that it was only a quick and easy jump to passive bi-amping.


A fool and his money...... etc., etc.


Attention True Believers: I've posted this for informational purposes only. I don't have a dog in this fight.


Cheers,

SB
 

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I have heard a number of actively bi-amped systems, from consumer to pro (many if not most pro sound reinforcement systems are bi-amped) and it makes a significant difference to me given the right system and room. However, unless there's a real requirement, and you have a system that will benefit, I wouldn't put forth the effort. With my present system and room I don't see myself bi-amping my Maggies again, partly because I have more than enough power on tap and the system sounds good enough to me as-is. Plus, I haven't the time, funds, or inclination to rebuild my old tube gear (gradually selling it off). Generally speaking, I agree with the reservations stated above. YMMV.


I was lucky that my Magnepans could use a pretty low-order network so my last personal bi-amped system used a passive line-level crossover with Counterpoint SA-220 on the bottom and Audio Research D-79 on top driving my MG-IIIa's. I built the crossover network into my preamp (Audio Research SP3a1), using both pairs of outputs. Whether you can get away with a passive network depends on the speakers and electronic components (for a variety of reasons).


Passive bi-amping strikes me as a waste of time, money and effort but opinions vary.


FWIWFM - Don
 

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Quote:
Originally Posted by MichaelJHuman /forum/post/19649869


What kind of wimpy logic is that. Think Tim on Tool Time. More power!



I have not ever heard a bi-amp system, but logic and math have always suggested it's not a great use of money. That's just my own opinion/logic.

Its really not about power..

Keep in mind, How much power can a mid-range driver or tweeter handle?


We have designed/built both bi-amped and tri-amped systems mainly for Pro-Audio & Studio applications....

By selecting specific amplifiers for each frequency range, each can be optimized such as:
a. A high current/high power for the bass with a high damping factor
b. Less power but good linear, frequency response for the mid-range
c. Again less power, but excellant transient response for the high frequencies


Another advantage is removing the distortion of the traditional, passive x-overs and replacing with an electronic X-over with low distortion and flexible filter & frequency settings.


But for consumer home theater systems, which are already typically bi-amped with a subwoofer/satellite. I would be apprehensive for any claims of its sonic benefits..

But by all means if someone wants to do it, go for it and post back..



Just my thoughts and $0.02...
 

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Oh, I agree. I was being sarcastic about "more power!" AV fans are usually guys. And guys seems to have this built in penchant for more power, even if not needed.
 

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I agree with "More power!" but not in a bi-amping way!


In general, the money and effort put into bi-amping would be better served by simply buying a more powerful amp. If you really do need several thousand watts per channel and can't find a single amp you like that will do that for you, ok, actively bi-amp some smaller ones you do like. I don't forsee many people reaching that point for their HT systems, however.


In any case, the only possible reason I can think of to justify passive bi-amping is if you've already got extra amp channels that are simply sitting idle. You're not going to hurt anything by connecting them, and you can impress people who don't know better by telling them you've bi-amped your speakers. And, who knows, you might even gain an extra half dB of amp headroom.
 

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Quote:
Originally Posted by kapnbill /forum/post/19646926


I'm thinking I can use one amp for bass on both speakers and the other for mid/highs?

Using one amp on the low pass binding posts and another amp on the high pass binding posts is horizontal bi amping. In contrast, using one amp on one speaker and another amp on another speaker is vertical bi amping.


As for the futility of passive bi amping, I have tried to formulate various analogies. Try this one. You & your wife always share the surf & turf because you like only the steak, she the lobster. Now, if both of you separately order the surf & turf, you still get only one steak, she only one lobster. And, no, you cannot take the steak off of her plate, nor she the lobster off of your plate. That food just goes to waste.


Passive bi amping presents a very similar situation, as the low pass crossover "likes" only the lower frequencies, the high pass crossover only the higher frequencies. Thus, the added power largely goes to waste, is dissipated as heat.


AJ
 

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Quote:
Originally Posted by MichaelJHuman /forum/post/19649533


Right, if it was not clear, active biamping is non trivial. You have to use an active crossover, which would cost money, and you would have to modify your speakers which is far from trivial (and would almost certainly void the warranty.) There are advantages to it, which Rodd Elliott explains in an article online (his claim being that you sort of get power for free, my brain is too tired to explain why - or maybe I simply don't understand it enough


.

IMO Active designs are now cheaper then passive designs. I know you guys have no control over design choices but I do



The new MiniDSP is an extremely powerful active XO choice and its under $200. Its hard to build quality XOs for that price tag and its even harder design complex passive XOs (testing theories is impossible).


Anyways, that sort of stuff isnt important to the OP unless he is going to be taking apart an existing design and making it active (which isnt a bad idea considering most XOs in low cost speakers are pretty bad).


Rod Elliott has some great info so does Linkwitz but for me the biggest advantage is the tweakability. I do not have to go out and find a speaker sound I like. I simple create the speaker sound I want in room because I can EQ my speakers all I want.
 
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