Bi-Amping questions

[brad1138]

I am experimenting with my new Mirage M-3sis and Bi-amping. I am using my "Biamp" (that is the brand name, I'll call it "Main" amp from now on to reduce confusion) amp to run the highs & mids, it is a much cleaner/smoother/detailed amp than the other amp, an Adcom GFA545, which is running the woofers.

My question revolves around balancing between the 2 amps. My "Main" amp has level adjusts, where the Adcom does not. What I did was run 1 speaker through each amp and adjust the "main" amp to match the Adcoms level. I used my receivers test tone generator and my sons, wifes, and my ears for balancing (I know I need a SPL meter). Then once I had the Main amp and the Adcom as even as I could get them, I hooked both spks to the main amp and balanced the other channel to get proper balance in that amp.

This seemed like a logical way to do it and maybe the correct way. The only concern I have is that although the detail increased greatly and over all it sounds much better, I think I have less bass than when I was running the whole thing off the "Main" amp. I could turn the main amp down a bit to relatively increase the Adcom but if the balancing was done correct then I shouldn't mess with that.

It is likely that the Adcom is just underpowered and of a lesser quality compared to my "Main" amp. I think an Adcom GFA 555 would probably be a better match.

Did I do anything wrong? Your thoughts please.

Thanks,
Brad

 

[lsiberian]

I am experimenting with my new Mirage M-3sis and Bi-amping. I am using my "Biamp" (that is the brand name, I'll call it "Main" amp from now on to reduce confusion) amp to run the highs & mids, it is a much cleaner/smoother/detailed amp than the other amp, an Adcom GFA545, which is running the woofers.

My question revolves around balancing between the 2 amps. My "Main" amp has level adjusts, where the Adcom does not. What I did was run 1 speaker through each amp and adjust the "main" amp to match the Adcoms level. I used my receivers test tone generator and my sons, wifes, and my ears for balancing (I know I need a SPL meter). Then once I had the Main amp and the Adcom as even as I could get them, I hooked both spks to the main amp and balanced the other channel to get proper balance in that amp.

This seemed like a logical way to do it and maybe the correct way. The only concern I have is that although the detail increased greatly and over all it sounds much better, I think I have less bass than when I was running the whole thing off the "Main" amp. I could turn the main amp down a bit to relatively increase the Adcom but if the balancing was done correct then I shouldn't mess with that.

It is likely that the Adcom is just underpowered and of a lesser quality compared to my "Main" amp. I think an Adcom GFA 555 would probably be a better match.

Did I do anything wrong? Your thoughts please.

Thanks,
Brad

When Bi-amping I think it's wise to use the same amps for simplicity. You want to start with equal power to both drivers and adjust as necessary. To do this I use test tones and an SPL meter.

I wonder how true of a bi-amp your speaker gets. This would require opening the speaker to see though. But it's certainly a fascinating idea to me.

 

[walter duque]

If you go activ or passive bi-amping you still need 2 identical power amps. To do it right. Some people fudge it by using a more powerfull amp for the bottom, but it's not right, you'll never get the right sound.

 

[Loren42]

I am experimenting with my new Mirage M-3sis and Bi-amping. I am using my "Biamp" (that is the brand name, I'll call it "Main" amp from now on to reduce confusion) amp to run the highs & mids, it is a much cleaner/smoother/detailed amp than the other amp, an Adcom GFA545, which is running the woofers.

My question revolves around balancing between the 2 amps. My "Main" amp has level adjusts, where the Adcom does not. What I did was run 1 speaker through each amp and adjust the "main" amp to match the Adcoms level. I used my receivers test tone generator and my sons, wifes, and my ears for balancing (I know I need a SPL meter). Then once I had the Main amp and the Adcom as even as I could get them, I hooked both spks to the main amp and balanced the other channel to get proper balance in that amp.

This seemed like a logical way to do it and maybe the correct way. The only concern I have is that although the detail increased greatly and over all it sounds much better, I think I have less bass than when I was running the whole thing off the "Main" amp. I could turn the main amp down a bit to relatively increase the Adcom but if the balancing was done correct then I shouldn't mess with that.

It is likely that the Adcom is just underpowered and of a lesser quality compared to my "Main" amp. I think an Adcom GFA 555 would probably be a better match.

Did I do anything wrong? Your thoughts please.

Thanks,
Brad

First, it is unclear what you are actually doing. I guess that you have a 3-way system, but are you really bi-amping, or some strange variant that still employs the internal speaker crossovers?

The reason one does bi-amping or even tri-amping is to eliminate the phase delays inherent with passive corssovers. The capacitors and coils are the worst audio component you can use and introduce huge variations in phase delays, which is what we pick out as undesirable audio quality.

The second big win for bi-amping is that the amplifier is directly connected to the speaker, so the damping factor of the amplifier has the maximum control over the woofer. This is less critical with the midrange and tweeter, but a big plus for the bass.

There are other advantages, but none so important as the first two I cited.

If you leave all of the internal crossovers in the cabinet, then bi-amping does essentially nothing for you. Any improvement you think you hear is probably your ego, not ears.

Back to phasing. Since the biggest advantage to using separate amps is maintaining a consistent phase relationship across the frequency spectrum (particularly at the crossover points), the amps should all be of the same type.

Lastly, while went straight ti tri-amping, keeping the internal crossover for the tweeter is not such a bad thing (and bi-amping). The gains of true tri-amping over bi-amping are not said to be that great.

Also, you need an active crossover when you bi-amp, but I assume you are doing that.

You are right that you need equipment to balance the system correctly. Room acoustics can play hell on the process, so be aware of that.

 

[jozeph78]

So, if I may chime in on this thread, is it better to use A+B to bi amp my speakers or should i just use the plates which link a single connection to my speakers.

Or should I go series or parallel I forget on the input. If I remember correctly that drops the ohms which should make the amp work harder but I think it can handle it.

System is a Yamaha 4600 with Sapphire ST3 (TST3 from the speaker company now).

 

[brad1138]

In 1990 I started working in a local high end AV store, Desco Audio&Video. I worked there for over 7 years and still know most everyone that works there. They do custom home theater systems into the 6 figure range all up and down the west coast, so they do know what they are doing. It is always the high end Spks that have biamping ability, but none of them have quick access panels for removing the crossover components at the same time. Out of all the times BiAmping was brought up over the years, I don't recall anyone saying it isn't worth doing if you don't gut your crossover at the same time.

I have been doing a lot of googling on BiAmping. I'll admit I didn't realize that what I did wasn't "true" biamping, but I do believe that it offers some advantages. I have no active crossover components. The Speaker manual shows hooking them up just as I did. But lets not argue that point.

I fully understand what having an "active" crossover accomplishes and why it is beneficial, but I am never going to strip out the passive components in my Mirages. I have a (imho) very fine set of speakers with quality components and I am not going to mess with them, but I still believe I can gain from biamping.

The crossover point between Woofer and mid/high is 350Hz, Why couldn't you just put a low pass filter of about 400-500 Hz, making sure of proper slope etc.., in line before the woofer amp and a high pass filter of about 200-300 Hz in line before the mid/high amp, again making sure you have the proper slop so that none of the used frequencies are removed. This would reduce the load on each amp and you could still keep the speakers internal crossovers intact. Obviously if you went full active you would have the crossover points right at 350Hz and remove even more frequency from the amps but that wouldn't be a huge difference.

Brad

 

[bandphan]

Passive bi amping, that your doing, doesn't give the benefit other than spl. Adding an external active like the behringer dcx2496 will yeild greater results. Just beacause the AV company that you worked for bi amps passive, doesn't mean that its correct. AV companies do many things to add effect and perceived value to sales. If you want audiable difference out of the system other than spl, look for an external
Jmo.

 

[ski2xblack]

If you are sending a full range signal to your main amp, you're not really gaining the benefits of bi-amping. Ditto if your sub amp is seeing a full signal. I doubt this is the case if you are using an AV receiver w/ built in bass management, but I'm not sure. It almost sounds like you are trying to build a fully active speaker system, which would require active crossovers, removing passive crossover components from the signal path, and lots of calibration. I once got to listen to a fully active M&K system that was out of this world, so if thats what your doing its a worthy goal to have. Its too bad that fully active systems have not become more prevalent in todays market.

I think you're on the right track, and could just adjust the levels of your amps for a more optimum balance, but as you said, you may need more juice for the bottom end. What is it you are trying to do, exactly, create a fully active speaker system, or quasi bi-amping a la typical HT systems?

 

[Loren42]

I have a (imho) very fine set of speakers with quality components and I am not going to mess with them, but I still believe I can gain from biamping.

Brad

The two are mutually exclusive. You can not bi-amp and use the passive crossovers. I know there is a whole bunch of stuff about passive bi-amping, but that's just hype written by speaker companies and amplifier companies looking to get into your wallet.

If you are resigned to not modifying your speakers, just hook them up to a stereo amp and enjoy them. I am sure that the quality of sound you get will not be better any other way you do it.

I am sure that there will be some flames for me from other members, but anything less than true bi-amping or tri-amping is just a waste of time and a waste of money. Keep them stock and enjoy it.

If you really want to spend money, go buy some music and a bottle of good wine or beer.

"Why couldn't you just put a low pass filter of about 400-500 Hz, making sure of proper slope etc.., " Because the passive crossover corrupts the phase relationship of the audio. Bad jewjew. As long as you keep the passive crossovers you will never realize an improvement in sound, period.

 

[TLS Guy]

In 1990 I started working in a local high end AV store, Desco Audio&Video. I worked there for over 7 years and still know most everyone that works there. They do custom home theater systems into the 6 figure range all up and down the west coast, so they do know what they are doing. It is always the high end Spks that have biamping ability, but none of them have quick access panels for removing the crossover components at the same time. Out of all the times BiAmping was brought up over the years, I don't recall anyone saying it isn't worth doing if you don't gut your crossover at the same time.

I have been doing a lot of googling on BiAmping. I'll admit I didn't realize that what I did wasn't "true" biamping, but I do believe that it offers some advantages. I have no active crossover components. The Speaker manual shows hooking them up just as I did. But lets not argue that point.

I fully understand what having an "active" crossover accomplishes and why it is beneficial, but I am never going to strip out the passive components in my Mirages. I have a (imho) very fine set of speakers with quality components and I am not going to mess with them, but I still believe I can gain from biamping.

The crossover point between Woofer and mid/high is 350Hz, Why couldn't you just put a low pass filter of about 400-500 Hz, making sure of proper slope etc.., in line before the woofer amp and a high pass filter of about 200-300 Hz in line before the mid/high amp, again making sure you have the proper slop so that none of the used frequencies are removed. This would reduce the load on each amp and you could still keep the speakers internal crossovers intact. Obviously if you went full active you would have the crossover points right at 350Hz and remove even more frequency from the amps but that wouldn't be a huge difference.

Brad

The answer is that you would be cascading filters. For the sake of argument lets say the passive crossovers have second order slopes. Now add a fourth order active filter, and you have sixth order slopes. The result a huge dip in response in the crossover region. The next issue is that the power delivered would only change by the amount of the dip in the response. The point even if the full frequency spectrum is present at the amps output, it is only the power actually delivered that gives rise to any current flow.

We have had a lot of biamping/biwiring issues lately.

One thing is clear, the questioners/advocates, seem to have the poorest gasp and understanding of the physics and engineering involved.

I've read through enough bilge and nonsense on this lately for a life time.

 

[just listening]

Personally, I'm very curious as to the brand of the "Main" amp.

For everything you are proposing, I'd follow Isiberian's suggestion and get matching amps. It's the easiest solution, why re-invent the wheel? Otherwise, get the Behringer DCX 2496.

 

[TLS Guy]

Personally, I'm very curious as to the brand of the "Main" amp.

For everything you are proposing, I'd follow Isiberian's suggestion and get matching amps. It's the easiest solution, why re-invent the wheel? Otherwise, get the Behringer DCX 2496.

The issue with using different amps is level matching and phase. Level matching can be done with pots.

I have pointed out before, some amps have output in phase with the input some out of phase. It is about an even split depending on the output stage topology. Since when using a single amp, this is a non issue, this spec is seldom mentioned in the spec sheet.

In an unbalanced amp there is no easy way of correcting a phase inverting amp, by the manufacturer. -ve has to be ground. You can not reverse it in the amp case, or you risk someone inadvertently doing damage. You have to reverse the speaker connections.

I always check phase of an amp when using different amps, even by the same manufacturer. It requires a signal generator and scope to phase check and amp. I have different models of amp from the same manufacturer in my rig and some are in phase and some phase inverting. So the phase inverting amps have to have the speaker connections reversed.

When using different amps, having a phase reversal at crossover is a very common error. Also this is an issue when different amps are used to drive different speakers in surround system.

So if you use a two channel external amp for mains, and the receiver for center, there is a very good chance of having your center and mains out of phase, unless you do a phase check.

 

[DD66000]

Using a high powered amp of at least 200w will provide a very good sound, w/o bi-amping.

As mentioned, bi-amping with passive crossovers is useless. 99% of all passive crossovers are of the A/B class. That is they produce a phase shift at the cap's dielectric zero point.
Using an active crossover, instead of the passive, eliminates that phase shift.

A second way of eliminating the phase shift is to build passive biased crossovers. Biased crossovers eliminate the shift by placing a 9V charge across the caps. This keeps the caps always on as the dielectric point is at 9V instead of zero.

This requires replacing each original cap in the circuit with a pair of caps, each twice the value, wired in series. It is at this common point of all series pairs, where the positive side of the battery is connected through 6 megohm resistors.

The class A circuit provides a clear, smooth sound throughout the entire range.

 

[lsiberian]

TLS and others have made great points.

This is another example of misplaced energy. Speaker Placement and room treatments will do far more for your sound than bi-amping, or bi-wiring. Remember we want to focus on the things that make the biggest difference. Speaker placement and room treatments make a huge difference. Focus on what makes the biggest differences and take care of doing those right.