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Old 18th January 2010, 04:51 AM   #1
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Default tri-amping question (s)

Hello.



I have one of those annoying, "I don't have all the data, but want answers anyways", kinda questions. Not sure if this belongs here or in speakers.

I have a pair of 3 way speakers (Infinity), which I have powered with a 40w SS amp for years now. Never had it more than half way turned up. The speakers are supposed to be 102db/m and 40w seems more than adequate to me. Actually bought the amp used and thought it was 75w for years.

So my question is, if I tri-amp, how little power can I get away with on the various amps?

I have a fisher el84 PP amp from a console (15w???) and all the iron to a 4 channel Leslie 7189 PP amp. The leslie OP transformers are twice the size of the Fishers, so I figured the fisher on the tweeters. None of them have UL taps.

3 x 15w sounds doable, but I was thinking I might get away with PP triodes on the mids and tweeters, but that leaves questions;

Is 8w (which I guess I would get from triode strapped el84s) enough to drive mid ranges and tweeters?

I see realize the circuit will need to be optimized for the triode mode, but does this mean a different OP transformer, or merely adjusting the rest of the circuit?

And, (finally); Would leaving one out of three amps in pentode mode, have any phase or timing differences that need adjusting?

Sorry, but I don't have any actual specs on the speakers. I realize the precludes educated answers. So I guess I am looking for a best guess.

Thanks, Eric
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Old 18th January 2010, 11:38 AM   #2
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Quote:
I have a pair of 3 way speakers (Infinity), which I have powered with a 40w SS amp for years now. Never had it more than half way turned up.

This type of statement always bothers me. The position of the volume control means absolutely nothing. The higher the signal the lower the position of the volume control. You could be clipping the amp at a 8:00 control position depending on the signal level being fed to the amplifier. It doesn't mean that you have whatever is left on the volume control setting before the amplifier clips.

Are your speakers set up to triamp? If they aren't you are going to need to go inside and separate the low from the mid from the high frequency. Depending on how primative the crossover it may be necessary to use external electronic crossovers or build the necessary crossover network.

My personal opinion is to forget it and channel your money into a better tube amp and call it good.
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Old 18th January 2010, 01:24 PM   #3
Loren42 is offline Loren42  United States
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Quote:
Originally Posted by malcontent View Post
Hello.



I have one of those annoying, "I don't have all the data, but want answers anyways", kinda questions. Not sure if this belongs here or in speakers.

I have a pair of 3 way speakers (Infinity), which I have powered with a 40w SS amp for years now. Never had it more than half way turned up. The speakers are supposed to be 102db/m and 40w seems more than adequate to me. Actually bought the amp used and thought it was 75w for years.

So my question is, if I tri-amp, how little power can I get away with on the various amps?

I have a fisher el84 PP amp from a console (15w???) and all the iron to a 4 channel Leslie 7189 PP amp. The leslie OP transformers are twice the size of the Fishers, so I figured the fisher on the tweeters. None of them have UL taps.

3 x 15w sounds doable, but I was thinking I might get away with PP triodes on the mids and tweeters, but that leaves questions;

Is 8w (which I guess I would get from triode strapped el84s) enough to drive mid ranges and tweeters?

I see realize the circuit will need to be optimized for the triode mode, but does this mean a different OP transformer, or merely adjusting the rest of the circuit?

And, (finally); Would leaving one out of three amps in pentode mode, have any phase or timing differences that need adjusting?

Sorry, but I don't have any actual specs on the speakers. I realize the precludes educated answers. So I guess I am looking for a best guess.

Thanks, Eric
Some rules of thumb. 50% of music power is below 500 Hz, typically. Every 3 dB of increase in SPL requires 2X in power in Watts.

What ever you do, test that all amps have the same phase with a given input. Some amps invert the phase at the output, some do not. If one or more do not, adjust the phase of your drivers as required.

You did not state where your crossover points were, but that will play a small part in the decision. The tweeter is going to be the least demanding on power requirements.

I think 15 Watts for the woofers is a little light in my opinion, but it will not hurt to try it and as you say, if you do not play the material at loud volumes, then it is not such a problem, however, it is good to have head room.
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Old 18th January 2010, 01:34 PM   #4
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Quote:
This type of statement always bothers me.
Sorry you are bothered. My point was I don't know the exact efficiency of the drivers nor the actual SPLs I am getting, only that 40w has been beyond adequate,for my use for years.

Obviously, I need to re-wire and use a crossover. (I had thought that to be self-evident). I wish to to eliminate the passive crossover, which has flakey L-pads anyway.

The point was to play with my exsisting junk and learn something about tubes and multi-amping, not buy a new amp. Buying a new amp teaches me nothing and sounds boring. (Plus, I then have to figure out what to do with this junk I can't bear to throw out anyway.)
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Old 18th January 2010, 01:38 PM   #5
Loren42 is offline Loren42  United States
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There is a wealth of information on that subject and more here:

Elliott Sound Products - DIY Audio Articles
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Old 18th January 2010, 01:45 PM   #6
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Keep the "sand" amp to power the woofers. Both power and damping factor are needed with Infinity stuff. Use "hollow state" for the mids and treble. Disconnect the crossovers and "L" pads and connect the speaker drivers directly to the amps. Use a 3 way electronic crossover between the preamp and power amps. Check the offerings of Marchand Electronics out, as a source for the electronic crossover.
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Old 18th January 2010, 04:52 PM   #7
DougL is offline DougL  United States
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Quote:
Originally Posted by malcontent View Post
Hello.

I have a pair of 3 way speakers (Infinity), which I have powered with a 40w SS amp for years now. The speakers are supposed to be 102db/m ...
So my question is, if I tri-amp, how little power can I get away with on the various amps?


Is 8w (which I guess I would get from triode strapped el84s) enough to drive mid ranges and tweeters?

I see realize the circuit will need to be optimized for the triode mode, but does this mean a different OP transformer, or merely adjusting the rest of the circuit?

And, (finally); Would leaving one out of three amps in pentode mode, have any phase or timing differences that need adjusting?

Thanks, Eric
There are 2 schools of thought about bi-amping.

School one: Each driver should reach your System SPL goal. Example 105 db @ 1 M. If you have 102 db @ 1 Watt @ 1 Meter Speakers, that's a minimum of 2 watts.

School 2: Each driver can have 3 db lower SPL goal than the system SPL goal because there is an extra 3 db there to allow headroom for multiple tones that is not necessary in a bi-amped or tri amped configuration.


If you are removing a pad from the tweeter and or mid-range, its more efficient and will need even less power.

I am running a DCX2496 crossover and love it. However, its tough to get right without measuring equipment and a reference speaker.

HTH

Doug
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Old 18th January 2010, 06:31 PM   #8
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Quote:
Originally Posted by malcontent View Post
Hello.



I have one of those annoying, "I don't have all the data, but want answers anyways", kinda questions. Not sure if this belongs here or in speakers.

I have a pair of 3 way speakers (Infinity), which I have powered with a 40w SS amp for years now. Never had it more than half way turned up. The speakers are supposed to be 102db/m and 40w seems more than adequate to me. Actually bought the amp used and thought it was 75w for years.

So my question is, if I tri-amp, how little power can I get away with on the various amps?

I have a fisher el84 PP amp from a console (15w???) and all the iron to a 4 channel Leslie 7189 PP amp. The leslie OP transformers are twice the size of the Fishers, so I figured the fisher on the tweeters. None of them have UL taps.

3 x 15w sounds doable, but I was thinking I might get away with PP triodes on the mids and tweeters, but that leaves questions;

Is 8w (which I guess I would get from triode strapped el84s) enough to drive mid ranges and tweeters?

I see realize the circuit will need to be optimized for the triode mode, but does this mean a different OP transformer, or merely adjusting the rest of the circuit?

And, (finally); Would leaving one out of three amps in pentode mode, have any phase or timing differences that need adjusting?

Sorry, but I don't have any actual specs on the speakers. I realize the precludes educated answers. So I guess I am looking for a best guess.

Thanks, Eric
Hi Eric
My system is 4 ways 4 amps, crossover home made, add on style gain stage+ filters, I believe this is better than the active style, in here all my friends have similar system because we do compared with others. in your case what I suggest is
1) use same kind of amps not mix with tube and silicon
2) for tube amps all in same style SE or PP because they sound different
3) high power for sub-low, less power for supper high
4) sensitive adjest for each amp ( place a 600 ohm pot in the filter's load)
5) phase adjust is most critical, because music is a combine frequency, if they are not in time never can get good sound, what we can do is judge by ear, in speaker system they use time delay by net-work's components, but in multi amps phase is 0 delay, the only way to do is place each speaker unit forward or backward, take off the mid unit put it forward till you get the best sound stage, (it should stay behind the speakers in air)
6) crossover point, every room should be different if you have a adjustable frequency crossover then you can find it out, if not then you can only by guess. I suggest you take off the mid, put it into another box to run full range, if it can't cover all, replace with a good full range unit, the original one use as sub and with supper high, crossover point 80-100 HZ for the sub and 10K-12K in high will do the most job
7) in making the filter, work out the value of C and L for the frequency that you want, cap can combine with small value to target, choke - you can custom order from Electric Print audio Las vegas, it will not too expensive because no current needs
8) you can add a gain stage (mu stage or SE with transformer to match 600 ohm)front of the filter for better result
Regard Tony Ma
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Old 18th January 2010, 07:11 PM   #9
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Quote:
1) use same kind of amps not mix with tube and silicon
Perhaps theoretically correct, but not a cost effective and practical solution, given the OP is starting with Infinity speakers. The sealed cabinet woofers require plenty of power, along with a good damping factor to work well. None of the "hollow state" stuff he has meets the need. A H/K Cit. 2 in good repair would work well as a bass amp, but that project will set someone back $2000+.

Blending SS bass and tubed midrange amps well is a challenge. A 24 dB./octave Linkwitz-Riley setup down as low as the midrange drivers can tolerate should do the job.

Quote:
5) phase adjust is most critical
A nice thing about Linkwitz-Riley crossovers is that they are in phase, at the "corner" frequency.

An active crossover between bass and midrange seems best to me. Especially since 40 WPC is on the low side for the woofer/cabinet combos under discussion. Getting power robbing passive parts out of the signal path will contribute to the cause. A passive crossover between midrange and tweeter seems quite reasonable.
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Old 18th January 2010, 07:36 PM   #10
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I'm considering bi-amp'ing my Tannoy HPD's with a Simple SE or DIYTube ST-35 to drive the high frequency driver and some sort of class-D amp for the 15 inch cone. I'd say 1 watt would do for the high frequency driver and 20 - 100w for the low frequency driver would do nicely.
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