Random Thoughts on Bi-amping

[russ69]

Back in the 70's there was not a lot of talk about bi-amping unless your loudspeaker system required it. Today, that's all I hear, "You need to bi-amp". Well, I come from "the simpler the better" (KISS) school and have avoided bi-amping for the last 40 years. However, I'm a firm believer in separates and mono-block amps but bi-amping with a pair of low-fi stereo amps or a multi channel receivers just doesn't make much sense to me, I'm probably wrong, what do you guys think? Remember this is the 2 channel forum............

Thanx, Russ

[wuzzzer]

True bi-amping can have its benefits. You can power woofers with a powerful SS amp and then power the midrange/top end with a tube amp giving you the best of both worlds. The woofers won't eat up the generally low watts that tube amps have and the midrange/tweeters will be blessed with the smooth tube amp output. I am only going by what I've heard, though. I've yet to experience a properly setup tube amp. []

As far as using a receiver's unused surround-back channels to bi-amp, I don't buy it as far as any kind of improvement.

[DanO55]

I do it with all tube equipment except the CD player. To me, the benefits far outweigh the additional cost in amplifiers, cabels, etc. System consist of a Nakamich CD player (model CD2), Heathkit XO-1 tube crossovers set to 1200hz, lows to a pair of Heathkit W5s with reissue Gold Lion KT 66 output tubes, highs to a set of Heathkit W4s. The system is currently driving a pair of Altec Valencias (846b) with 416-8a 15 inch woofers and 811 horns with 806a drivers. Crossovers have 12db slopes.

This paragraph is supposed to be where I use a bunch of undefinable words and phrases to relate to you how well the sound is reproduce. Instead I will just say I have never heard any system I have had sound more pleasing and accurate. All of the equipment was meticulously restored/upgraded with high quality parts. The background noise floor is very quiet. To use a phrase often heard (read), all of my recorded music sounds better than it ever did.

For me, it was definetly worth the additional cost. Bi-amping or even tri-amping is what I have instore for my La Scalas. Pictures can be posted if anyone is interested.

[runninshine]

Can someone please explian to me in a simple way how to bi amp? Sorry for the lack of knowledge, but Im very interested in learning all of this stuff and I don't have anyone here that I know or hang out with to teach me some of these technique.

[Mr. RF62]

IMO, (and someone can correct me if I'm wrong) but I think its best done with the proper power for the drivers being used as well as having an external crossover to send the proper frequencies to the appropiate drivers. Not to mention fun having the ability to select different frequencies to try different sounds/x-over points. This should be done by someone that knows what to do though as sending the wrong frequencies to the wrong driver may not be desireable. But done properly, can have a positive effect on the sound of a speaker system.

[dtel]

I think its best done with the proper power for the drivers being used as well as having an external crossover to send the proper frequencies to the appropiate drivers.

I think that is 95% of the benefit, not so much the proper power but the external crossover is where most of the gain of biamping is. IMO

I bi-amp for 2 CH because I don't have crossovers built for those speakers and the external crossover is much better for flexibility if I did want to make changes. I could get permanent crossovers but I just went this direction considering I got a good deal and if I make changes I can just change any part of the crossover to match anything I want to do.

Personally I would never bi-amp a speaker just for bi-amping reasons, I would think a more powerful amp would solve any problems that regular bi-amping would help. Unless you wanted to use something like tubes for mid and high frequencies and SS for bass but that also brings in other problems like matching the volumes easily. IMO

[Coytee]

Can someone please explian to me in a simple way how to bi amp?

Simply put, you have your source (vinyl, cd...other...) go into your preamp. Coming out of your preamp you then plug into an active crossover. Active crossovers are usually good to have either 2 or 3 or 4 outputs per channel (per speaker side).

If you have a 3 way speaker you would get an active that is capable of having 2 inputs (from your preamp) and SIX outputs (three for each speaker)

So, your path is, source into preamp. Preamp into your crossover. From the 3 outputs of your crossover you would then attach an amp to each one and then connect each amp to the specific driver.

It sounds more complicated than it really is.... it IS a bit more complicated but not necessarily a real challange.

There are some here, like myself, who are biamping. The above is actually describing tri-amping since you have 3 drivers per side.

In my case, I have a 2-in, 4 out active crossover. This gives me 2 channels per speaker (hence, biamp). My path is the same. I have my sources plugged into a preamp, the preamp output goes into the active crossover input and from the active crossover output I go to my amps and then directly to the drivers.

When you use active all the way, you will generally not use a passive at all. I think you could use a passive in a 3 way speaker where you might take the active crossover to divide the signal into a low frequency signal up to say, 400 hz and feed that directly to an amp and to the woofer. The rest of the spectrum (400hz up to ????) would then go to another amp and that could go to the upper half of a passive crossover. This would save some costs of 3 amps but... might not garner you all the benefits of doing a full blown active crossover system.

I'm not an expert, the above is just my understanding and how I do it.

[Coytee]

Unless you wanted to use something like tubes for mid and high frequencies and SS for bass but that also brings in other problems like matching the volumes easily. IMO

Not to pick on you (since you're like 5 feet taller than me)... [] but this is easily overcome as well.

When using amps with differing input sensativities, you can take the values (of the input sensativities) and insert them into the forumla "20xlog(V1/V2)" where V1 and V2 are the input sensativities. This will give you a number. The number will be positive OR negative, depending solely on which value you put on top or bottom. The number will be the same, only the sign will be different. Regardless of that...this number will represent to you the number of DB's you need to attenuate the more sensative amp to better match the lessor amp.

So, if you have two amps, one with 1 volt input sensativity and the other with a 2.4 volt, you'd have "20xlog(1/2.4)" = -7.60 (it would have been a positive 7.60 had I switched the 1/2.4 to be 2.4/1)

Anyways...this means you want to internally attenuate the amp with the 1 volt input sensativity by 7.6 db's and they will then be matched. You can do this inside your Dx38 quite easily.

Test tomorrow at 11:00