Passive Biamp

[vintage 5.0]

I have wondered what others have found when doing a passive bi-amp setup. I have done this twice. The first time I used a pair of Dynaco ST 70s that were real similar. I have just put both of my modded McCormack DNA .05 in a passive bi-amp setup. Both of these amps are alike. I found the highs and lows seem to have more kick and better sound. I think the real high and low points of the music sound better. I do think both amps have to be the same for this to work well. I know you do not end up with more overall power but it seems to me that it does sound better. I am not a guy that believes in anything and have to hear some difference. I did hook an amp to each speaker and that did not sound as good as one amp to the highs and one to the lows. Not sure why it sounded better but it did. I just was curious if others have had good luck with this.

 

[soundmig]

Yep ... vertical passive bi-amping (with identical amps) seems to make most any set-up sound better. Not real sure why, but ...... then again there's a lot of things in this hobby that are hard to explain at times. If i had to guess, the amp on the mid-high section isn't drawing as much power from the amp's power supply - since it working against high impedance at the lower frequencies - and may stay in the lower power region (where amp works in class A) giving a cleaner representation of the highs?

 

[Splatter Pak]

My main speakers are passively bi-amped. An 80 wpc amp runs the woofers, and a 50 wpc amp runs the mid and tweets. It works a lot better than when I had a 200 wpc amp powering the woofers and the 80 wpc amp on the mids/tweets. There is less bass slam now, but better integration. It's all about balance. I keep an eye out for an electronic crossover.

 

[vintage 5.0]

I think you have a great point soundmig. I was talking to the guy at SMC Audio. He said that similar thing. The bass amp is just pushing bass and therefore more dedicated power not having to push the highs. He also said the highs amp is not working as hard. Makes sense and again not sure why but it does sound better.

 

[MannyE]

I did it with my BP-2002 Def Tech towers and they never sounded better. I used 4 of the 5 amp channels in my Outlaw 750 and split the signal coming from the main left and right out of the B&K with "twofers". It was really nice. Later I did it again while I had an identical Outlaw 750 for a while and I really liked it.

Did it really sound better or was I making my self think it sounded better? I have no way to A/B that setup, but I really think it worked.

 

[KB007]

I started with a single Bryston 3B-ST, then bi-amped (passive) with 3 3B-STs and things sounded somewhat better. Then I sold the 3B-STs and bought a pair of 4B-STs and things did sound better, especially the bass - tighter, snappier, etc. Then I got a killer deal on a Krell 402e and went back to a single amp and things got much, much better.

 

[MannyE]

I started with a single Bryston 3B-ST, then bi-amped (passive) with 3 3B-STs and things sounded somewhat better. Then I sold the 3B-STs and bought a pair of 4B-STs and things did sound better, especially the bass - tighter, snappier, etc. Then I got a killer deal on a Krell 402e and went back to a single amp and things got much, much better.

Speakers?

 

[sqlsavior]

You can also make line-level passive RC filters to further separate the frequencies the amp sees. Two resistors, two capacitors, and three halves of an interconnect, per channel, to get a 6 dB / octave rolloff at a chosen frequency.

Before manufacturers started equipping speakers with 2 sets of connectors, this was what "passive bi-amping" meant, i.e. using line-level passive filters instead of active, powered crossovers.

 

[KB007]

Speakers?

Totem Mani-2s.

 

[Legrace]

Started out with a single 100 w/ch SS amp. Then switched this out for 125 w/ch tube power. On reading about biamping became intrigued so decided to give it a whirl. Speakers are Tannoys which are provided with the requisite dual binding posts. Liked it a lot, that is until I discovered passive triamping! Was surprisingly easy to setup. All I had to do was move interconnects around to insert the sub between the preamp and the power amps. Now I am able to take advantage of the subs' inbuilt high-pass filter. Before had the pre signal split so the towers were receiving the full range. But now with the high-pass engaged only the sub and its 500w amp assigned the lowest end. Tubes are feeding mids and back again to SS for the top end. Three amps handling three freq bands, SS/Tubes/SS. Very dynamic sounding. Because everything is in series with the pre signal the pre volume control scales all amps in sync.

 

[soundmig]

You can also make line-level passive RC filters to further separate the frequencies the amp sees. Two resistors, two capacitors, and three halves of an interconnect, per channel, to get a 6 dB / octave rolloff at a chosen frequency.

Before manufacturers started equipping speakers with 2 sets of connectors, this was what "passive bi-amping" meant, i.e. using line-level passive filters instead of active, powered crossovers.

Is there a source for a diagram of how to wire this and calculate the values?

 

[sqlsavior]

Is there a source for a diagram of how to wire this and calculate the values?

Here's one:
http://www.t-linespeakers.org/tech/filters/passiveHLxo.html

 

[Grenadeslio]

I have wondered what others have found when doing a passive bi-amp setup. I have done this twice. The first time I used a pair of Dynaco ST 70s that were real similar. I have just put both of my modded McCormack DNA .05 in a passive bi-amp setup. Both of these amps are alike. I found the highs and lows seem to have more kick and better sound. I think the real high and low points of the music sound better. I do think both amps have to be the same for this to work well. I know you do not end up with more overall power but it seems to me that it does sound better. I am not a guy that believes in anything and have to hear some difference. I did hook an amp to each speaker and that did not sound as good as one amp to the highs and one to the lows. Not sure why it sounded better but it did. I just was curious if others have had good luck with this.

Horizontal passive bi-amping, vertical passive bi-amping both have their pros & cons and suit different situations. I've used both many times in automotive audio installations, and home use and prefer the benefits derived from vertical for home use more often. All the benefits of monoblock amplification with the added benefits of the high frequencies not sharing the same filter caps and output devices as the lower frequencies.

 

[Powertech]

I think you have a great point soundmig. I was talking to the guy at SMC Audio. He said that similar thing. The bass amp is just pushing bass and therefore more dedicated power not having to push the highs. He also said the highs amp is not working as hard. Makes sense and again not sure why but it does sound better.

Almost, but not quite right. Both amps are running with a full range signal. The loudspeaker filters are each blocking what they don't want and converting it into heat. This follows the 1st law of thermal dynamics - energy cannot be created or destroyed, only converted from one form to another.
The only part that can be true is that the bass speakers will be drawing more current than the tweeters are, and because the tweeter crossovers are blocking bass power with what is effectively a high resistance (high resistance equals low current). Again, the bass crossovers are blocking the high frequencies with a hgh resistance, but there isn't much power there to block. So from this - the 'bass' connected amp will experience a greater current demand than the 'treble' connected amp.
If the 'bass' connected amp starts to clip, you won't hear that clipping at the higher frequencies where the human ear is more sensitive to it because that amp is not clipping.

I know what I am trying to say, but does that make sense?

Where full active systems win on this is that each amp only running with part of the audio spectrum. The amplifiers actually have more headroom as high frequency waveforms are not riding on top of low frequency waveforms.

 

[BobHol]

I tried biamping once with my AR9's and a 5 channel ADCOM 6000. I really couldn't hear a difference to make it worth the added complexity. The overly complex crossover in the AR9's may be part of it. I believe that an active crossover before the amp is the best way to biamp

 

[soundmig]

Here's one:
http://www.t-linespeakers.org/tech/filters/passiveHLxo.html

Thanks sqlsavior! I appreciate it.

 

[Grenadeslio]

I tried biamping once with my AR9's and a 5 channel ADCOM 6000. I really couldn't hear a difference to make it worth the added complexity. The overly complex crossover in the AR9's may be part of it. I believe that an active crossover before the amp is the best way to biamp

All channels are still sharing the same power supply in your example, not surprised you didn't hear much difference.

 

[twiiii]

Vertical bi amping using an electronic crossover is always the least preferred, because the bass channel can suck all the available energy from the power supply and compromise the HF section totally wiping out the sound of one channel. With horizontal bi amping of a three way system the mid and treble clarity will mask the bass failure in most instances when the bass amp is starting to strain. What is passive bi amping? Is that two amps operating full range driving different sections of a speaker with the passive crossovers left in place and the straps removed. The only thing you gain is changing the sound by using different amps with different coloring. You lose all the advantages of electronic bi-amping. Higher efficiency, lower IM distortion, less series resistance, better cone control of woofer and midranges better use of power available, high dynamics potential in addition to coloring the sound the way you want with the amps chosen.

 

[vintage 5.0]

powertech I will have to admit I got a little lost. So does it at all make sense that it sounds better. I tried the one amp alone. It sounded good but again the highs and lows are much more full using this way. I am not sure why but have done this twice with two different sets of amps. I am using a pair of Sonus Faber Grand Piano speakers.

 

[MannyE]

Totem Mani-2s.

Nice! Those remind me of the Jamo