Bi-amping

 

New member
Username: Discgolfdoug

Post Number: 1
Registered: Sep-05
Just wondering if using a receiver's A and B outputs for bi-amping is effective or not? It's a Sony Str-697, if that matters. I'll put in a e-mail to Sony as well. Anyone that has advice, feel free.
 

Gold Member
Username: Jan_b_vigne

Dallas, TX

Post Number: 5573
Registered: May-04


Free advice. Don't wait for an answer from Sony.

More free advice. Don't think your biamping from the A and B outputs.


That could be a costly mistake.




 

Silver Member
Username: Stu_pitt

NYC, NY

Post Number: 481
Registered: May-05
Doug - Using the A and B outputs from your receiver is bi-wiring, not bi-amping. Some people swear by it, and others think it's a waste of time. Personally, from experience and a little knowledge of audio, don't see how it makes any difference, other than getting someone to buy extra speaker wire.

Bi-amping does have audible results. Very few if any people would doubt that. To bi-amp, you need a second amp. One amp would run the high and midrange drivers, and the other would run the low driver.
 

Silver Member
Username: Danman

QUEBEC CANADA

Post Number: 502
Registered: Apr-04
I bi-amp and really enjoy the sound. Stereo imaging is much better. I also have everything in bridge mode which also changes the damping factor of each amp to more appropriate levels. However, I use the vertical bi-amp method which means each amp drives one complete speaker not one for the highs and one for the lows. Most manufacturers recommend this method when using the exact same amps.

The major problem (if you want to call it that!) is I have SO MUCH power that I have to be careful not to get carried away. Everything is so much better with this method.
 

Bronze Member
Username: Bunny

Big D, Texas

Post Number: 28
Registered: May-05
Danman,
How do you accomplish the Bi-amping?
I also have two NAD amps in bridge mode, each driving its corresponding speaker.
Hope you can assist me.
Thanks

 

Silver Member
Username: Danman

QUEBEC CANADA

Post Number: 505
Registered: Apr-04
You ARE bi-amping!!!!!!!!! One amp for each speaker.......one right channel, the other left channel!

You don't need any help!
 

Gold Member
Username: Jan_b_vigne

Dallas, TX

Post Number: 5595
Registered: May-04


That's not bi-amping. That's merely using monoblock amplifiers. If each amplifer runs the speaker full range (assuming no subwoofer) without utilizing a crosssover to separate the woofer from the upper frequency driver(s), that is not bi-amping.


Using a powered subwoofer and a typical HT receiver is technically bi-amping the front channels. You have one amplifer handling the low frequencies and another amplifer handling everything above that XO point.


There is vertical bi-amping and horizontal bi-amping. They work differently and have somewhat different benefits.


Stick the term into a search engine to find information on how to do it and what the beenfits actually amount to.


 

Silver Member
Username: Danman

QUEBEC CANADA

Post Number: 507
Registered: Apr-04
Jan........there is more than one form of bi-amplification:

What is bi-amping?
Bi-amping is the technique whereby two power amplifiers are used to improve the sound quality of a loudspeaker that can be bi-amped.

Monoblocs

The simplest form of bi-amping is to use two monobloc amplifiers, one for the left channel and one for the right channel. Most mono amplifiers will have higher power outputs per channel than their stereo equivalent. This has the benefit of having more power on tap than by using one stereo amplifier, as well as reducing the 'crosstalk' that occurs when both left and right channels are housed in the same box.

Vertical stereo bi-amping

Our preferred method of bi-amping is vertical stereo bi-amping. This is when two identical stereo power amplifiers are used, one for the left speaker and one for the right speaker.

If we consider just the left speaker and amplifier, one channel is used to drive the high frequencies and one is used to drive the bass frequencies. The same, of course, applies to the right speaker and amplifier.

To analyse why this works so effectively, we need to appreciate that the load characteristics of the tweeter and woofer are very different. The woofer requires a large current and if driven with a single channel of power amplifier, a heavy bass transient can absorb all of the available current, causing the amplifier to clip and distort. By separating the current to the tweeter and woofer, we are apportioning the power with a more equitable split -- thereby allowing the amplifier much more 'headroom'.

Horizontal stereo bi-amping

This is when two stereo amplifiers are uses with one amplifier driving both left and right tweeters, the other driving both left and right woofers.

Whilst this configuration will offer a performance advantage over using just one stereo power amplifier, because of the increased total current available, the amplifier driving both woofer channels will be working much harder then the one driving both tweeter channels -- this will mean the bass will bottom out faster under heavy transients than it would if a vertical orientation were used -- also crosstalk between amplifier channels is the same or worse than it would be with a single stereo amplifier


 

Gold Member
Username: Jan_b_vigne

Dallas, TX

Post Number: 5602
Registered: May-04

Yes, I think if you read my post carefully, you will see I mention the two forms of bi-amp conenctions. I assume you feel you have accomplished the vertical bi-amp configuration by using two mono amplifiers, one for each speaker cabinet.


*


"I also have two NAD amps in bridge mode, each driving its corresponding speaker."


This implies one bridged amplifier driving one speaker cabinet full range. Maybe that's not how it's hooked up; but that's what I read. Otherwise, biamping this system would require at least four amplifier channels, bridged or not, to bi-amp two speakers cabinets.


*


"If we consider just the left speaker and amplifier, one channel is used to drive the high frequencies and one is used to drive the bass frequencies. The same, of course, applies to the right speaker and amplifier."


This approach does not use bridged amplifiers nor monoblock amplifiers. It utilizes two separate stereo amplifiers with the left channel, let's say, driving the low frequencies and the right channel driving the higher frequencies. In this configuration, a crossover, usually an active device, would be placed in front of the amplifiers to make the division between frequency bands. Using a mono amplifier, whether in bridged or dedicated operation, to drive both low and high frequencies (full range operation) cannot be considered bi-amping by any defintion of bi-amping I have so far come across.



*


From what I read in bugs question and in your reply, "One amp for each speaker.......one right channel, the other left channel!", I see no sign of bi-amping the individual drivers. I see no mention of any manner of dividing the frequency bandwidth before it reaches the amplifiers. All I can detect from what I read is a mono amplifer driving each speaker cabinet full range. The XO in the speaker cabinet is still doing the division of frequencies. Correct me if I am wrong about the hook up.




Also, if that information came from an outside source, please give a link to your source. These two statements:

"Most mono amplifiers will have higher power outputs per channel than their stereo equivalent"

and

"Whilst this configuration will offer a performance advantage over using just one stereo power amplifier, because of the increased total current available ... "


are somewhat suspect in their accuracy.




 

Silver Member
Username: Danman

QUEBEC CANADA

Post Number: 508
Registered: Apr-04
Jan I would need clarification on something. If I wanted to vertically bi-amp in stereo with the equipment I have and followed the instructions that I quoted, would I not lose stereo separation? After all, if the left channel is driving the mids and highs of each speaker and the right channel the lows, would this not be the case? Would you reverse the channels on one of the amps to compensate?

One thing I have noticed about my monoblock method, is that stereo separation is amazing since each channel is driven by one amp only. I do not use any type of crossover just my basic equipment. What do you suggest that would be the best method for my type of gear?
 

Silver Member
Username: Danman

QUEBEC CANADA

Post Number: 509
Registered: Apr-04
Jan, I also found this link which is basically what I have now (Vertical method) except no bridging.

http://www.symphonysound.com/articles/biamp.html
 

Gold Member
Username: Jan_b_vigne

Dallas, TX

Post Number: 5609
Registered: May-04


It is typically the shared ground plane between the channels that accounts for the crosstalk, and lack of separation, between channels. By separating the two amplifiers left and right you will maintain separate grounds and there should be no crosstalk between left and right channels other than what is introduced by components ahead of the power amplifiers.

If you are running vertical bi-amping you have to separate the signals that drive low and high frequencies. The best way to accomplish this task is with an active XO placed before the power amps. This keeps each channel of the amplifier using the amount of power those signals require. The benefit in the low frequencies is minimal in this arrangement since the bass will be where most power is drawn anyway. The larger advantage is in the upper frequencies where the smaller signal levels will allow the amplifier channel more headroom and more clarity since they are not being swamped by the voltage and current swings that drive the low frequencies. Does that make sense?

Lacking an active XO, you can still do vertical bi-amping, if your speakers allow their XO network to be divided after the power amplifiers. You will hook up your pre amp to the stereo power amplifier with a stereo interconnect going to the two channels of each amplifier. Four interconnects total. Then the amplifiers will be connected to the speakers as if you were doing vertical bi-amping with four separate channels of amplification. Which you are. This places the XO after the power amp and so you loose the advantage of the smaller signals not being swamped by the current/voltage flow through that channel. The channels feeding the small signals of the upper frequencies will still be reporducing the bass frequencies but they will be filtered out of the signal at the XO. But you still gain in that the ground plane between channels has been eliminated at one more point - the speaker XO. Which method you like is really up to you.

Often vertical bi-amping is done with two large amplifers running the low frequencies and then two smaller amplifiers running the upper end. The general recommendation is to stick with the same company's product if they are consistent in their sound, i.e. all NAD, McIntosh, Mark Levinson, etc. Some people will do vertical bi-amping with solid state amps on the bottom and tubes on the top. Voicing of the amplifier is more problematic when this approach is taken though good results, actually probably some of the best, can be achieved with that technique if you are careful. Personally, I've listened to tubes for so long, I just can't listen to solid state bass and think it correct though many people prefer its punch.

I really can't tell you which method will satisfy you the most. Everyone listens for different qualities and every approach has its good and bad points. One thing to decide is what you will give up if you are running your amps bridged. Some amplifiers are bridged in series which will increase your voltage drive and some are bridged in parallel which increases the current delivery of the amplifier. Whether your speakers need/like lots of current would be the first determination I would make and then find out how your amps are bridged. You're correct that damping factor changes in the bridged mode as does output impedance, the two being tied together with one affecting the other.

I wish I could be more specific but it is another of the many suck it and see problems of what you like in your system.


 

Gold Member
Username: Jan_b_vigne

Dallas, TX

Post Number: 5610
Registered: May-04


"(Note: In each of these scenarios, obviously two monoblocks could be used in place of one stereo amplifier)."

Two monos per channel equaling one stereo amp. Thus four channels of amplification.


"discrepancies in rise times will result in mismatches between the left and right channels."


Even the function of bridging an amplifier into mono can cause these discrepancies. It is uncommon for the left and right channels of an amplifier to be exactly identical. They may be close enough that they appear similar when viewed on a scope and used as a stereo amplifier; but when combined their small differences in linearity can present more problems than what the task will accomplish to the good. This is particularly true of any amplifier that utilizes some amount of negative feedback. The resulting mono amplifer can have comb filter effects, time distortions and become less stable. To name a few of the possible downfalls you could face.

What you have from Symphony is a fairly well written article that gives more thought to the operation of bi-amping than your original text. The problem is the numerous methods all have to be considered and in most cases tried to find which, if any, works best. It is impossible to run through all the scenarios in the short amount of space alloted to an article or a forum message.



 

Silver Member
Username: Danman

QUEBEC CANADA

Post Number: 510
Registered: Apr-04
Sorry for not responding sooner but work had a priority!

I want to thank you for your wonderful insight! I have re-done my system into the Vertical method explained in the Symphony text and have noticed a better resolution over all than being in Bridge mode. I had a little (or lot!) more power but at the expense of some sound. Sometimes you have to experiment to find what you want with sound.

One thing I can definately say, using 2 amps and a pre-amp was the best money I ever spent and would have to pay a very big chunk more to get better sound in my opinion!

Thanks Jan......I appreciate your help.
 

Gold Member
Username: Jan_b_vigne

Dallas, TX

Post Number: 5629
Registered: May-04


No problem. Good luck.
 

Gold Member
Username: Dmwiley

Post Number: 1042
Registered: Feb-05
Whether bi-amping is effective is very much equipment dependent (amplification, preamp, speakers, etc). Hoping not to insult, I doubt one would realize a measurable/audible difference using most Sony audio equipment for amplification.
 

Bronze Member
Username: Bunny

Big D, Texas

Post Number: 29
Registered: May-05
Danman and Jan,

While I did not actively participate in the discussions, I have read with great interest your posts and I thank you both for your input.
Just as Danman already did, I will think about changing my configuration to compare and decide what sounds best to my ears.
Once again, I greatly appreciate your contribution.
Regards
 

Silver Member
Username: Danman

QUEBEC CANADA

Post Number: 525
Registered: Apr-04
Well, to bring this up again.......I have been experimenting this weekend and after many hours of plugging and unplugging, I have returned to the Bridge mode vertical bi-amping method. This is definately the best sound for my speakers. They seem to like the current. The only difference amp wise would be slightly higher heat but nothing dramatic and it would seem that NADs like this mode of play! They certainly do well with all currents and that to me is amazing for this price range. The dynamics and power are incredible but it is especially the stereo separation that two amps can't be beat. I will no longer change my configeration as this is the best for me.
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