Mono amp or Bi-amplification

wes · Jan 24, 2013

Hello

I am new on your site and was kindly invited by RBFC.

My system is as follows: http://www.blu-ray.com/community/gallery.php?member=wes&folderid=3141

I need to update pictures, but any way I have a dilema nad am wondering what you think?

Is it best to use a monoblock let' say of 600W or a stereo amp of 300W per channel and bi-amp the speakers?

GaryProtein · Jan 24, 2013

The answer is going to depend on who you ask.

Both sides have their devotees. It depends partly on your speakers and how easily you can separate out the drivers at its crossover level, the crossover points you want or need to use which will be determined by the drivers and the size of the amplifiers you are using.

I would prefer to use a bi-amplified system with four channels of 300 watts than two channels of 600 watts. Each amplifier will work more efficiently with a specified frequency range than working full range. Plus, there will be less wasted power with a bi-amped system because passive crossovers waste a lot of the amplifier's energy. You will need an active crossover after your preamp and before the power amps.

You have a very nice theater.

treitz3 · Jan 25, 2013

Hello and welcome to the What's Best Forum, wes. Your home theater is impressive. I love the attention to detail, even down to the door hinges. To answer your question, Gary summed it up pretty well and I can concur with what he said. Well, with only one difference, my preferences just so happen to lay on the other side of the fence.

Tom

FrantzM · Jan 25, 2013

Hi

Welcome to the WBF,well laid out Theater. Simply beautiful!

I am mostly with Gary. But I am not not entirely convinced by the passive bi-amping approach. Passive bi-amping, i-e using the speakers passive crossover doesn't seem to me as efficient. I would have preferred active if at all possible. A more complicated but better, IMO, option.

Steve Williams · Jan 25, 2013

simply beautiful room Wes

welcome to WBF

One question........isn't there any concern for heat generated by your Classé gear inside that wooden cabinet.

microstrip · Jan 25, 2013

Great room - if I had a wider room I would also hide everything except the source components and the speakers!

The Classe's CA-M600 have a microprocessor controlled fan - if there is no glass on the doors they would easily survive in this nice cabinet.

The answer to the bi-amp question is not simple. Most of the time the sound quality of the 300W or the 600W amplifier will not be the same, and this will be a major issue. I am going through a similar process - my speakers can be tri-amplified!

wes · Jan 25, 2013

Steve Williams said:
simply beautiful room Wes welcome to WBF One question........isn't there any concern for heat generated by your Classé gear inside that wooden cabinet.

The cabinet is completely open in the front and back so the heat doesn't accumulate. Also the CA-M600 have really cool technology "

"Heat management in Classé’s new Delta series amplifiers is providedby the ICTunnel™ (pronounced Icy Tunnel), a sensor- and microprocessor- controlled technology inspired by the heatsinks found in high-power laser and medical equipment. Mounted inside the unit, the ICTunnel™ actively regulates the amplifier temperature to ensure both optimum performance and reliability.

From room temperature, the amplifiers warm up fast. They reach their ideal temperature in less than fifteen minutes and remain there regardless of how hard they are driven. No conventional heatsink can do this."

http://www.classeaudio.com/ctseries/ct-explained.htm

Classé Audio CA-M600 Monoblock Power Amplifier reviews
http://www.classeaudio.com/reviews/reviews-pdfs/Secrets_Review_Classe-CA-M600-PowerAmplifier.pdf
http://www.classeaudio.com/reviews/reviews.../ca-m600_tas_2_2011.pdf
http://www.classeaudio.com/reviews/reviews-pdfs/stereophile_cam600_feb2011.pdf

vinylphilemag · Jan 25, 2013

wes said:
Is it best to use a monoblock let' say of 600W or a stereo amp of 300W per channel and bi-amp the speakers?

Hi Wes, and welcome! I too am a member over at Blu-ray.com (I'm richteer there); you'll see quite a few familiar names here.

To answer your questions, with all else being equal, I'd say go the monoblock route. You'll have greater power reserves, and it doesn't rule out the possibility of bi-amping with another pair of monoblocks in the future!

wes · Jan 25, 2013

vinylphilemag said:
Hi Wes, and welcome! I too am a member over at Blu-ray.com (I'm richteer there); you'll see quite a few familiar names here.

To answer your questions, with all else being equal, I'd say go the monoblock route. You'll have greater power reserves, and it doesn't rule out the possibility of bi-amping with another pair of monoblocks in the future!

Yes that would be ideal but I am unlikely to add more amps!

DonH50 · Jan 25, 2013

Two 300 W amplifiers provides no more power than a single 300 W amp, the power is just into two frequency bands. If you need more power, you need a 600 W amp (two if you want to bi-amp).

IMO, the biggest benefit from bi-amping occurs from using an external line-level crossover and connecting the amplifier outputs straight to the drivers, no crossovers in the speaker box. That allows the amplifiers to control the drivers directly, and the crossover allows you to precisely set the crossover frequencies, gain, phase, delay etc. to optimize the speaker's output. You can use DSP (or analog, though a lot more work and less precise) to provide much steeper crossover slopes, limiting interaction among drivers, time-align everything to provide the best possible step/pulse response, etc. All assuming you have the equipment, knowledge, and time to dial it in.

GaryProtein · Jan 25, 2013

DonH50 said:
Two 300 W amplifiers provides no more power than a single 300 W amp, the power is just into two frequency bands. If you need more power, you need a 600 W amp (two if you want to bi-amp).

IMO, the biggest benefit from bi-amping occurs from using an external line-level crossover and connecting the amplifier outputs straight to the drivers, no crossovers in the speaker box. That allows the amplifiers to control the drivers directly, and the crossover allows you to precisely set the crossover frequencies, gain, phase, delay etc. to optimize the speaker's output. You can use DSP (or analog, though a lot more work and less precise) to provide much steeper crossover slopes, limiting interaction among drivers, time-align everything to provide the best possible step/pulse response, etc. All assuming you have the equipment, knowledge, and time to dial it in.

I agree completely with your second paragraph. I don't understand your first paragraph. How do two 300 watt amps produce no more power than a single 300 watt amp?

Four channels of 300 watt amps [two channels of amplification for the left, and two for the right] will be needed to get the same power as two channels of 600 watt amps [one 600 watt amp for the left and one 600 watt amp for the right].

wes · Jan 25, 2013

GaryProtein said:
The answer is going to depend on who you ask.

Both sides have their devotees. It depends partly on your speakers and how easily you can separate out the drivers at its crossover level, the crossover points you want or need to use which will be determined by the drivers and the size of the amplifiers you are using.

I would prefer to use a bi-amplified system with four channels of 300 watts than two channels of 600 watts. Each amplifier will work more efficiently with a specified frequency range than working full range. Plus, there will be less wasted power with a bi-amped system because passive crossovers waste a lot of the amplifier's energy. You will need an active crossover after your preamp and before the power amps. You have a very nice theater.

Thank you, I don't see myself messing with the passive crossover inside the B&W 800 Diamond, that would void the warranty plus I have no idea what I am doing

So if don't add an active crossover is it still worth it? to do Stereo amps or Monoblocks

RBFC · Jan 25, 2013

wes said:
Thank you, I don't see myself messing with the passive crossover inside the B&W 800 Diamond, that would void the warranty plus I have no idea what I am doing

So if don't add an active crossover is it still worth it? to do Stereo amps or Monoblocks

Welcome to WBF, Wes. I think you'll find many topics of interest here!

If you don't want to use an external crossover for active biamplification, my recommendation would be to have more powerful amplification. One or two 300 watt monoblocks will still lose "x" amount of power as heat into the passive crossover components if you do "passive biamplification". A 600 watt monoblock will have more power to push through that resistance, IMO.

Lee

microstrip · Jan 25, 2013

Wes,

B&W skilled engineers developed the passive crossover of your excellent speakers. IMHO it is crazy to assume that some one that is not an expert in speaker designing and crossover should remove it and replace it with an active crossover just to benefit of the magic of direct connection of the amplifier to the driver. If you want active speakers you should buy the great B&W Nautilus with its four way active crossover - it was designed from start to be an active system.

Anyway, if you want go active I hope I am the first in the line to get the old passive crossover - it uses a Mundorf Gold/Silver Capacitor in the tweeter circuit and several other Mundorf goodies.

BTW, one of the good thinks of WBF is that you will listen to many conflicting opinions.

GaryProtein · Jan 25, 2013

wes said:
Thank you, I don't see myself messing with the passive crossover inside the B&W 800 Diamond, that would void the warranty plus I have no idea what I am doing

So if don't add an active crossover is it still worth it? to do Stereo amps or Monoblocks

You HAVE TO add the active crossover between the preamp and power amps. That's how bi-amping, tri-amping or quad-amping, etc., works. That's how my system is set up.

opus111 · Jan 25, 2013

microstrip said:
B&W skilled engineers developed the passive crossover of your excellent speakers. IMHO it is crazy to assume that some one that is not an expert in speaker designing and crossover should remove it and replace it with an active crossover just to benefit of the magic of direct connection of the amplifier to the driver.

As those skilled engineers used to be my colleagues I think perhaps I'll point out a potential error in your thinking here. They are aware of the advantages of active crossovers, when done right. But the market pretty much demands passive for reasons of compatibility with the installed base (amps, dealers etc.). Once a passive XO has been designed (the hard part) its relatively easier to copy its response in a line-level circuit.

If you want active speakers you should buy the great B&W Nautilus with its four way active crossover - it was designed from start to be an active system.

Its a bit pricey for what it delivers (to my ears too 'metallic') but you are right about it being designed as active from the start. It uses LR4 slopes. Interestingly the designer has gone back to passive with his 'Vivid' range and I guess that's because he wants to fit in with the market rather than having any notion that passive is superior.

P.S. its jolly hard to source a decently transparent active XO - good luck if you're deciding to go that route. A compromise would be to activate the bass only, that's the part which benefits most I reckon due to the compromises inherent in having a series bass inductor which is necessarily huge.

DonH50 · Jan 25, 2013

GaryProtein said:
I agree completely with your second paragraph. I don't understand your first paragraph. How do two 300 watt amps produce no more power than a single 300 watt amp?

Four channels of 300 watt amps [two channels of amplification for the left, and two for the right] will be needed to get the same power as two channels of 600 watt amps [one 600 watt amp for the left and one 600 watt amp for the right].

There's a thread in the Tech Forum that shows this, IIRC. Been a while since I did it. Bi-amping does not provide more power, unless you use more powerful amps, just better directs the power you have.

I'll try two ways:

1. If you have a single 300 W amp then all drivers get a maximum of 300 W. If you split the signal into two bands, high and low, and use two 300 W amps, then the highs get a max of 300 W and the lows get a max of 300 W as before. Just through different signal paths.

2. Amplifiers look like voltage sources to the speakers. (I'll ignore esoteric design configurations.) The power into a resistive load is P = V^2 / R. A 300 W amp can deliver a certain maximum voltage and thus a certain maximum power (if it has enough current drive ability). If you use two 300 W amps, then the maximum voltage has not changed, and you do not get more power into a given R load. The only way to increase the power is to use a higher-power amp that has more voltage swing.

In practice you might realize a hair more power at clipping if say the LF signal is at clipping and the HF are not since they are usually much lower in amplitude; then when the LF amp clips the HF amp does not. The benefit is minor at best (I would say insignificant in the real world).

HTH - Don

p.s. For me it's a no-brainer if I am not pulling the speaker crossover out: a pair of 600 W mono amps provides 3 dB headroom compared to a pair of 300 W amps on each side.

vinylphilemag · Jan 25, 2013

GaryProtein said:
You HAVE TO add the active crossover between the preamp and power amps. That's how bi-amping, tri-amping or quad-amping, etc., works. That's how my system is set up.

Not strictly accurate: it's perfectly possible to take a bi-wired speaker and add another pair of amps to the mix to make the speakers bi-amped.

microstrip · Jan 25, 2013

opus111 said:
As those skilled engineers used to be my colleagues I think perhaps I'll point out a potential error in your thinking here. They are aware of the advantages of active crossovers, when done right. But the market pretty much demands passive for reasons of compatibility with the installed base (amps, dealers etc.). Once a passive XO has been designed (the hard part) its relatively easier to copy its response in a line-level circuit..

I would love to know how someone copies the sound of a Mundorf silver/gold oil capacitor.

opus111 said:
Its a bit pricey for what it delivers (to my ears too 'metallic') but you are right about it being designed as active from the start. It uses LR4 slopes. Interestingly the designer has gone back to passive with his 'Vivid' range and I guess that's because he wants to fit in with the market rather than having any notion that passive is superior.

We debated it several times in this forum. Guessing is a very nice exercise, I will have an opinion only when he designs an active that can be compared with his excellent best passive designs.

GaryProtein · Jan 25, 2013

vinylphilemag said:
Not strictly accurate: it's perfectly possible to take a bi-wired speaker and add another pair of amps to the mix to make the speakers bi-amped.

I would not consider that. To me it's a second rate application. Bi wired is extremely over-rated and adding amps without an active crossover is a waste of amplifier power. They will be amplifying signals that will never be used by the drivers. If you are going to the trouble of doing this, use an active crossover. It makes no sense to ignore that component.

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