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What do you do to set gain when bi or tri-amping?

Funky54

Funky54

Super Member
This thread is NOT a debate about bi-amping. If you ARE bi-amping please share and participate. I also would like it to NOT turn into an argument over passive and active crossovers. Of course everyone has an opinion and they are welcome to share, but please don't let that take over the topic of gain matching and calibrating.

I've been experimenting with bi and tri-amping. I thought it might be cool to find out what practices others use to set up gain?

In verticle bi-amping I'ts pretty easy. But things get more complicated when you horizontal bi or tr-amp.

With verticle I literally use a db meter and average multiple samples to fine tune it in. But that would not work with horizontal.

I haven't done it yet… but I'm toying with verticle bi-amping my woofer and mids and then horizontal bi-amping my tweeters. But that would compliment gain setting a lot.

What do you guys do?
 
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Not going into the debates that you mention--just posting regarding my experience. My Kappa 9's are powered by 4 Krell monoblocks--one for each of the high/mid/mid-bass drivers and one for each of the double woofers using the passive internal crossover--probably not the most efficient/effective, but they still sound like Kappa 9's should.

My Maggie 3.6R's are currently bi-amped by 2 Aragon 4004's operating in stereo mode--one handles the highs and mids, the other handles the low end--again with a passive crossover network.

Gain has never been an issue, since I use identical amps fed from the same pre-amp. I know some people like to use tubes for the top end and bigger SS amps for the bottom end, and there can be gain issues related to the power output of the amps, input sensitivity and impedance matching.
 
As savatage1973 mentions, if you're going through the speaker crossovers then the amps need to have or be set to equal voltage gain, at least for starters. Of course, one can alter the balance from there if one chooses but equal voltage gain is the baseline.

For bi/tri amping with amps direct to the drivers, I think it's a similar approach except the voltage gains need to be adjusted to account for the (possibly) different driver sensitivities. And again, after that one can tune by ear to your preference or maybe run some sweeps with Room EQ Wizard, et al, if you were trying for for a specific response curve.

For basic setting of the amp voltage gains I'd probably use a 1kHz test tone input to the amps, then adjust each one to the necessary voltage output. Same in the case of going though the speaker crossover, with sensitivity figured in if direct to the drivers. In the latter case, say the woofers are 90dB/W/m and the mid is 95dB/W/m. You'd have to set the mid amp 5dB lower than the woofer amp (or the woofer amp 5dB higher). If you used a reference point of say 10V on the amp that's going to the woofers, you'd set the mid amp to about 5.6V. That should produce roughly equal overall voltage sensitivity with driver sensitivity factored in.
 
For the past eight years or so I have been horizontally passive bi-amping my AR3a's. I further do this with just the three terminals AR provided. Now these speakers came with "controls" so AR intended their customers to have some control over speaker voicing. Unfortunately these controls corrode and eventually the speakers become dull and lifeless. Replacing the controls was an option, but even when you do that, you still end up with laid back, bass heavy speakers.

Thus I decided to bypass the controls and instead bi-amp. When you bi-amp you gain full control over speaker voicing. That is my AR's can be laid back, bass heavy or with the independent volume controls on my amps I can turn them into bright, in your face West Coast speakers.

This was a very economical solution for me as I had a number of mid/low power receivers collecting dust in my basement. So, I just recycled one and that unit became the amp powering the mids/tweeters.

Naturally, when you use dissimilar amps you have all kinds of problems upon bi-amping. Fortunately, I have a dual trace scope so was able to verify the amps are in phase and also to adjust for exact equal power going to each half of the speakers. Eight years later, I no longer worry about equal power. I mean the whole idea was to provide me with voice control and I adjust voice ... FREQUENTLY!

In fact, I find I prefer bright speakers in the morning and bass heavy, laid back speakers late at night. To achieve this change is just a few tweaks of the volume controls.

Recently, I bi-amped my "newer" AR's. This time I purchased a unique receiver that has 4 full range 100 wpc @ 4 ohms amps in a single box. To bi-amp with this receiver is a dream. Phase is no issue and the digital readout volume controls make balancing power so easy. I can't believe the difference in what I went through eight years ago compared to my recent experience.

Now to adjust voice is as simple as a few remote clicks. Once again, I find I adjust voice for changes in source and time of day.

In summary, many speaker manufacturers provide controls to give their customers some limited control over voice. These are awkward at best. When you passive bi-amp, you effectively move those controls to the gain controls on the independent amps.

I like it - maybe I'm a "control freak" - but I'd never go back to a single amp on these complex three-way speakers.

Regards,
Jerry

PS: Don't forget, you still have to worry about phase in all of this.
 
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You can do it by ear. Many years later I still give the gains on the electronic crossover a tweak. Sometimes I think I am just compensating for my hearing loss, but the sound of my stereo has to please Me.
 
I use an electronic crossover. A Dayton EMM-6 microphone and REW simplify the process.
 
whoaru99 said:
For bi/tri amping with amps direct to the drivers, I think it's a similar approach except the voltage gains need to be adjusted to account for the (possibly) different driver sensitivities. And again, after that one can tune by ear to your preference or maybe run some sweeps with Room EQ Wizard, et al, if you were trying for for a specific response curve.
Click to expand...

This is where it gets tricky, because it involves an external (generally active) crossover--I have done this for pro-audio arrays. Now, not only do you have to worry about matching gain/volume levels based on the amps and driver sensitivities, but have to deal with crossover frequencies and slopes. You can try to tune them by ear, but a DSP of some sort is generally a lot easier--but also factor in that you have to KNOW the specs of your drivers. Even though it may "sound good to YOU", it does not mean that you are not pushing drivers to or beyond their designed limits--and then the list goes on with other factors like driver performance in a given cabinet volume, room size/dimension/placement. At a certain point, you end up "re-engineering" the original crossover network--for better or worse. My JBL's and Infinity's have pots on the crossovers to "damp" or "brighten" drivers, so I just use them. My Maggies are custom crossovers (modified originals), since the 3.6R's were not designed for bi-amping from the factory, but I still use the same crossover frequency and slope (their crossovers are external anyways, so not a big mod). I may have a PhD, but it is not in audio engineering/design, so I leave that to the "experts".
 
savatage1973 said:
At a certain point, you end up "re-engineering" the original crossover network--for better or worse.
Click to expand...

Arguably, there is no speaker crossover to rework in a true bi/tri amp system, except maybe a high pass "oops" capacitor before the tweeter and maybe mid.

But the OP doesn't want to discuss that aspect so we're just left to guess what's really going on, and provide grossly general suggestions.
 
whoaru99 said:
Arguably, there is no speaker crossover to rework in a true bi/tri amp system, except maybe a high pass "oops" capacitor before the tweeter and maybe mid.

But the OP doesn't want to discuss that aspect so we're just left to guess what's really going on, and provide grossly general suggestions.
Click to expand...
I was really hoping to learn how others actually adjust the gain. Do they measure with a db meter like I do? Do they use pink noise and match them? Should they be matched? I mean, would the original designer expect each driver to (realitive to their own frequency) hit the same db level?

As to my personal situation, my speakers are unique in their design. I dont need to use an active crossover. Each driver is completely isolated from the others. Each driver has its own filter.

But back to gain settings. It sounds great in its current state. Currently I'm verticle bi-amped. But is it right to assume that the Tweeter and Mid should be the same DB with pink noise as the woofer? ... And with that thought, Should it really be the Tweeter, mid, and woofer should each separately be at the same db? Does that mean the mids and highs are actually too low? Its kinda a big circle in my head... its interfering and distracting my intake of cheap whiskey.
 
Funky54 said:
...I mean, would the original designer expect each driver to (realitive to their own frequency) hit the same db level?
...
Click to expand...

I presume most, not necessarily all, designers want their speakers producing relatively flat response across the audio band.

For me, the answer is clear. I'd start by adjusting the amps as I described earlier then either fine tune to preference/by ear, or use something like Room EQ Wizard, TrueRTA, et al, to dial in (check for correct polarity at crossover points, smooth/flat response, etc.). More than likely the latter then if I didn't like I'd just tweak to preference.
 
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If you are using identical amplifiers and drivers of equal sensitivity it makes no difference if you are horizontal, verticle, or in a X pattern, upside down or backwards. The rub comes with different sensitivities of drivers and different amplifiers. The easy way is with a precision sound level meter and a pink noise source. But if you have a PC its cheaper to get a Dayton program with a precision microphone for around less than $400.00 and do it correctly. Its a long term investment that will payback many dividends over many years to come. Just like investing in any outstanding piece of HiFi gear.
 
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I don't know about vertical or horizontal I just bi-amp. To me that means using a 2 way electronic crossover which has it's own volume controls for two separate amps, one powering the HF and one the LF.

Or it means running my full range drivers, full range with no crossover in the signal path from a flea watt tube amp while low passing the woofers with a powerful plate amp. In this arrangement both amps use their own volume controls and I believe the signal is cleaner as there's no electronic or passive crossover to add it's own signature sound.
 
I use the little knobs on the crossover to adjust the gains. I've never used matching amplifiers in any setup*. Home amps usually don't have input level controls, thus the crossover's knobs are essential. Pro amps typically have input level knobs, and those are usually maxed, or trimmed down a bit, whichever method yields the best results. Adjustments are done with a mic at the listening position feeding a rectum anal-izer with pink noise playing. Easy-peasy to get setup properly in no time.

I suggest you drop the dB meter and noise for now. If you are using pink noise (equal energy per band), and the bands aren't EXACTLY the same number of octaves wide, then your target wouldn't be the same measurement for each driver. Likewise, for white noise (equal energy per frequency), and your range of each driver isn't EXACTLY a linear portion of the spectrum, again your target would be non-equal levels from each driver. Just get a mic and an RTA and you'll be done in five minutes. If you insist on using a dB meter, use sinewaves spaced just on either side of the crossover frequency, or better yet, VERY NARROW bands of pink noise on either side of the crossover frequency.


*Oh wait, I just remembered I've got the same amps on the front channels of my main system for tweeters and woofers. But a different one on the mids and subs.
 
I've tried the level matching, and the by the ear, and for me, the first gets you into the ball park
and the second tunes it in.

use one of your favorite tunes to dial it in.
 
House de Kris said:
I use the little knobs on the crossover to adjust the gains. I've never used matching amplifiers in any setup*. Home amps usually don't have input level controls, thus the crossover's knobs are essential. Pro amps typically have input level knobs, and those are usually maxed, or trimmed down a bit, whichever method yields the best results. Adjustments are done with a mic at the listening position feeding a rectum anal-izer with pink noise playing. Easy-peasy to get setup properly in no time.

I suggest you drop the dB meter and noise for now. If you are using pink noise (equal energy per band), and the bands aren't EXACTLY the same number of octaves wide, then your target wouldn't be the same measurement for each driver. Likewise, for white noise (equal energy per frequency), and your range of each driver isn't EXACTLY a linear portion of the spectrum, again your target would be non-equal levels from each driver. Just get a mic and an RTA and you'll be done in five minutes. If you insist on using a dB meter, use sinewaves spaced just on either side of the crossover frequency, or better yet, VERY NARROW bands of pink noise on either side of the crossover frequency.


*Oh wait, I just remembered I've got the same amps on the front channels of my main system for tweeters and woofers. But a different one on the mids and subs.
Click to expand...
I have a Rane 27 band RTA. For PA I tried it and it was the worst thing I ever bought... I tried to use it for years and finally realized that I could tune a room in much quicker and it sounded much much better doing it by ear. I went from Dual 32 band EQ on the mains and 27 on the monitors to just using 15 band EQ's and it was actually an improvement.
 
You can use an equalizer/analyzer that puts out pink noise and uses a microphone set up at the listening position. The equalizer display will show you the level of each of the bands. You can then adjust with either one of the biamp amplifiers, or with the equalizer.
 
I don't get the concept of amp level matching?

In my bi-amp system one amp makes 3 watts while the other makes 300 watts.
 
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