General Bi / Tri Amp question...

[Leland47]

I was wondering...
On a Bi or Tri amp....what percentage of the amps output goes to Bass, Mid-range and Tweeter speakers?

Or another way to look at it....I suppose one could build an amp with 2 or 3 different sized OPTs....and size them on what they would be used to drive?

Or a pair of tri amps....could be different tubes and power outputs....or PPP, PP, and SE for the tweeter?

Kind of a noob question....but I've been thinking about it.

 

[Leland47]

Or what about an Active Crossover....that regulates the frequency that the Amp gets before the speakers....as opposed to a passive crossover after the amplifier?

 

[gadget73]

I think it would depend more on the speakers than anything else. That would determine your crossover points and power levels as well to get overall sound levels equal across the board. Broadly speaking bass wants more watts but exactly how much more depends on how sensitive the individual drivers are.

You'd want the crossover ahead of the amp, otherwise the amplifier would need to try and reproduce the whole spectrum, only to discard it at a crossover after the amp. Kind of defeats the point. The crossover can be passive, Magnavox bi-amps were simple LC crossovers using all passive components and it worked out. Its easier to do it with an active crossover, just tweak a knob and adjust the output.

 

[BinaryMike]

This page has some useful data on audio power vs frequency. You can see that amps for tweeters in three-way systems used for classical music would need a small fraction of the woofer amp's power rating, but two-way systems used for rock music might need equal LF and HF amp power ratings, depending on crossover frequency. It's typical for mids and tweeters to have higher efficiency relative to woofers, which allows you to cut the amplifier's power rating in half for every 3dB increase in driver efficiency.

 

[levimax]

I just completed a bi-amp then tri-amp project. It was quite an adventure and I learned a lot and am very happy with the results. Here is a link to a good link on the subject http://sound.whsites.net/bi-amp.htm

During the process I compared SS and tube amps on high , mid, and low.... without passive crossovers the differences between amps became more clear. In the end I came to the conclusion that if you use amps that highlight their strengths and use an active crossover you can get very good sound for a reasonable price. As much as I like tube amps on the bass it is hard to beat a MOSFET amp... lots of clean cheap power with super low output impedance/ high damping factor. On the mid range tubes really shine and no SS I tried sounded the same and I don't know why, for the highs I ended up with a small Class A SS amp... again playing to the amps strength. You can do the same thing with all tube amps but for the high and low frequencies it is really difficult and expensive (mainly due to the limitations / expense of the output transformers).

I would definitely recommend you go for it... have fun.

 

[whoaru99]

^^^ Yes, that's a pretty good site.

Here's a more direct link to the same site re. approximate power distibution vs crossover frequency: http://sound.whsites.net/bi-amp.htm#power_dist

 

[mcdan]

I have been using a tri-amped system for at least 20 years now. The "heart" of the system is a Marchand XM-16 electronic crossover. From there it's 2 solid state amps for the bass, 45 Watts of pure class A tubes on the midrange and currently, 15 Watts pure class A on the tweeters. Let me tell you Leland47 once adjusted you'll never go back!
Dan

 

[gadget73]

Multi-amp setups honestly make good sense. Its much easier to make an excellent limited frequency amp than it is to make an excellent wide frequency amp. Its not a new idea either, EH Scott was doing it back in the 1930s for the same reason.

One of these days I would love to get myself set up to actually do it.

 

[Leland47]

Thanks for the great links and all the replies!

I've been buried at work....and odd hours, too..so haven't followed up on everything posted yet.

Multi-amp setups honestly make good sense. Its much easier to make an excellent limited frequency amp than it is to make an excellent wide frequency amp. Its not a new idea either, EH Scott was doing it back in the 1930s for the same reason.

One of these days I would love to get myself set up to actually do it.

It seems to me the actual OPT would have less work also....(bass, mid or high) having to work with less frequency band. Also, I don't recall seeing any OPTs that are wound for specific narrow band frequency....
I'll have to check out that Maggie with the passive pre-crossover...


Off topic....work has thrown me a couple musically related jobs lately...
I got to bartend at the Bon Jovi Concert here in Tampa last week....Kinda fun! Had a good time!
And yesterday morning at 5AM....had to start setting up for a party....then found out John Legend was going to play! A huge road case came rolling in....with a Yamaha Grand Piano in it....
There was a guy tuning it for what seemed hours.....pre show....along with the sound checks and such...
I saw 3 empty Semi trailers for the Bon Jovi show at the loading docks...and mountains of road cases....in the basement hallways. The Legend show was very intimate...only about 1000 people. Bon Jovi was about 20,000 at the Amalie Arena....and I was on the 6th floor.

Here's a couple pics...

 

[Leland47]

My brother has informed me that John Legend's wife was on the cover of SI swimsuit edition in 2010.....if anyone is interested....