Bi-wire/bi_amp?

myblzch

I'm a little confused on how to best Bi-amp my RT-55s with my Yamaha R-V1105. Do I wire the posts to my A and B connections seperatley and run both rcv. outputs?
Or, do I wire the posts together and run only the rcv. output for A? Any reasonable help would be appreciated.:)

steveinaz

That wouldn't be bi-amping, you'd be bi-wiring. To bi-wire, run one set of speaker cables from "A" to the bottom post on the speaker (remove the jumper bar); run a second set of speaker cables from "B" to the upper posts of the speaker.

True bi-amping is running seperate amplifiers dedicated to low frequencies and high frequencies respectively, called "horizontal" bi-amping.

You can also bi-amp by dedicating 1 amp for each speaker---the purpose of this? If you have bridgable amps, you can hook each bridged amp to each channel for more output, called "vertical" bi-amping. This is great solution if you have seriously inefficient speakers and want more output.

Another 2 cents....don't mess with the expense of bi-wiring/bi-amping until you move into seperate components, I'm not trying to be an "audio snob", its just not going to make much difference (if any) for the cost involved. FWIW, I have seperates and don't bi-wire or bi-amp; I tried it, but couldn't hear any improvement that I could "quantify." The speakers I own now are not bi-wirable. Nor are some of the most expensive speakers out there.

Flamesuit on....

Tour2ma

Well, I'll start by flaming you for mixing up the two bi-amping terms...
Vertical dedicates both ch's of each amp to one speaker.
Horizontal dedicates each amp to the same set of drivers in both speakers.

myblzch,
Welcome to the Club...
Steve's telling you true, you can't bi-amp with your current equipment.
If you want to bi-wire, you can either run both pairs form the A terminals, or one from A and one from B.

steveinaz

Damn! I had a feeling I had those backwards....I fixed it.

PolkWannabie

Originally posted by steveinaz
True bi-amping is running seperate amplifiers dedicated to low frequencies and high frequencies respectively, called "horizontal" bi-amping. In my opinion this is the only way to go if you're going to bother at all.

Steve,

Question ... taking a nice simple situation where you have two bi-ampable mains and two identical 2-channel amps ... Wouldn't it make more sense to have one amp drive the left and one amp drive the right as opposed to having one amp drive the upper and the other amp driving the lower frequencies ?

In the latter situation the amp driving the upper will be coasting while the amp driving the lower frequencies will be working hard. IMHO the load is better split left and right rather than upper and lower frequencies.

Your thoughts ?

steveinaz

PolkWannabie,

It depends on what you're trying to accomplish. If the 2 amps are internally bridgeable, and your goal is to provide more power for low efficiency speakers, then yes, you would want to dedicate an amp to each speaker.

In the other scenario, providing one amplifier for each frequency segment is done to attain absolute quality--albeit an expensive proposition. This helps especially in the mid/high range because the amplifier is only "seeing" the mid/high portion of the crossover. It also provides an absolute seperation of the bass/treble signals because you're using seperate speaker cables for each frequency spectrum.

An example; when I was running Bose 901's (alright, stop throwing things) I used 2 Soundcraftsmen PM840's, bridged for 600 watts/rms, one for each speaker--because the 901's are incredibly inefficient. When I sold the Bose for some Pinnacle towers I dedicated each amp (not bridged), 1 for L/R Lows and 1 for L/R Highs, because the Pinnacles were 93dB efficient, the 205 watts/rms provided by the PM-840's was plenty of power to run them in a non-bridged mode.

2 different goals, 2 different topologies.

PolkWannabie

For simplicity let's leave bridging out of this for now as this in essence makes two mono amps out of what was two stereo amps ...

Again assume we have two 2-channel amps capable then of producing four equally powered outputs ( See the crude drawing below for basic choices )

In your "other" scenario ...

I'm not sure why it's more expensive per se ... you have the same two 2-channel amps whether you are driving left and right or upper and lower ...

The only way the amplifier driving the highs & mids is not going to be "seeing" lower frequencies that it will then attempt to amplify is by having a crossover or a high pass filter in front of the amplifier, otherwise although the crossover in the speaker may be tossing the lower frequencies, the amplifier will still be dealing with them.

As far as this situation also providing an absolute seperation of the bass/treble signals because you're using seperate speaker cables for each frequency spectrum, this is true in either situation.

What am I missing ?

Rick

steveinaz

"Expensive" in terms of getting relatively little improvement given the cost involved. When bridging, you're getting a big payback, double, sometimes triple the output depending on the amps design. Of course using 2 identical amps, each one powering a speaker, is a total waste of money and time. There's NO benefit.

I wish I could remember the reference, but measurements show that when an amp is connected to a particular portion of a speaker crossover, it will "shunt" the output of the frequencies not "requested" (though no where near to the effect of an active crossover) Thereby conserving power and reducing intermodulation distortion, again I can't remember where I read this, but it makes sense.

I'll see if I can find this article, a very interesting read.

As far as I'm concerned bi-amping/bi-wiring is a waste of time and money unless you are using it to gain output via bridging or you are doing "true" bi-amping which involves the use of external crossovers.

PolkWannabie

Although it may not be clear that active .vs. passive biamping improves the low end much since that's the frequency range that any amp would spend most of it's oomph trying to deal with, one would think !? that using this technique prior to amplification of the hi's & mid's would be of value since one would be reducing the amps load by a significant amount having already removed the low frequencies. This technique is relatively simple to employ using passive modules available from Harrison Labs and others to filter out what you don't want going to you mid range and above drivers.

I'm not sure I follow your other comments given that you've stated that you believe there is value to separating the high & mid signals from the lows from point of origin all the way through to the speaker which btw I in essence agree with. I purposely used simple example of two 2 channel amps, but in an HT environment it can become significantly more involved in terms of matching amplifier capabilities with numerous channels to drive and then having to or wanting to decide on top of that whether to split L & R or Hi & Lo etc. for the mains and possibly center as well.

myblzch

Thanks to everyone for the info.

:cool:

Tour2ma

Glad you were helped, now let the hi-jacking continue...

Interesting question PW... My take is that a Carver type amp design, i.e., able to borrow power from one ch, would best be used in a vertical scheme.

Steve, I remember an earlier discussion (a few months ago I'm guessing) on horizontal bi-amping with me starting off where I think PW is. I think it was HBomb that got it through to me that the elements of the crossover in the circuit did in fact determine the frequencies to be amplified.

If I find the old thread, I'll post the link...

PolkWannabie

That would be helpful but I think I'd have to see it some sort of technical documentation with a scientific explanation to believe it. IMHO there IS a difference between active and passive biamping.

steveinaz

Tour2Ma:
I believe that is what I read as well, though it doesn't "brickwall" unwanted frequencies like an active crossover--you still would get pretty good results.

My point to all of this, is that bi-amping, to be done correctly requires alot of money. Of course if you're a Kennedy, go for it. I just can't see doing this with the average system unless you are doing it for power gain (vertical bi-amping) with inefficient speakers (bridging/bi-amping); that's a very practical purpose indeed.

steveinaz

Originally posted by PolkWannabie
That would be helpful but I think I'd have to see it some sort of technical documentation with a scientific explanation to believe it. IMHO there IS a difference between active and passive biamping.

Definitely a difference. Active crossover's are the way to go in a true high-end setup for horizontal bi-amping. Of course at this level of audio, your not messing around with a receiver (or shouldn't be). I'd do it if I won the lottery--WAIT, no I wouldn't, Wilson Watt Puppy's don't have bi-wire/bi-amp terminals.

hmmm, Imagine that? One of the most respected speakers in the industry at any price, and you can't bi-wire it....

Like I've said from the beginning, good base components don't require all this voodoo/money to sound good.

PolkWannabie

I have in the past used a receiver as a preamp or as fully what it was manufactured to do, but that's not what we were discussing ...

With regards to what is required in order to sound good, I heartily agree. However I thought we were having a more or less philosophical discussion regarding the different flavors of bi-wiring ( which I've personally never witnessed an advantage to doing ) and bi-amping.

I don't pretend to be an audio engineer or even an audiophile, but I'm not a complete idiot either ... I some how have trouble envisioning that the speaker calls for anything whether it be a certain amount of current or a certain frequency range.

The simple analogy I've always had is that an amp is more or less like a pump trying to move amperage downstream. A higher impedance speaker will slow or regulate the flow of that current across the entire frequency range more so than a lower impedance speaker but as far as frequency control goes I can't envision that some how the speakers can talk upstream to the amp and say something to the effect of don't bother amplifying anything below 40 hz because I don't want it.

If this is not the case than there would be no real differences between active and passive biamping. If however that is the case then one could make a valid argument that four channels worth of amplification going to two speakers are better used in a more load balanced way splitting that amplification left and right as opposed to high and low.

steveinaz

Originally posted by PolkWannabie
... I some how have trouble envisioning that the speaker calls for anything whether it be a certain amount of current or a certain frequency range.

The "current" issue i understand completely. A simple analogy here; you have 20 amps available at your standard wall outlet, however the outlet only provides the amperage necessary to drive the load. It's not a "smart" outlet, its just electrical fact.

If i remember the article right, I think its more about what the amp see's rather than the speaker. It had something do with amp recognizing that lower frequencies (on the mid/high crossover) were being "shunted" and therefore expending very little effort in these shunted frequencies--but like I said, I can't recall the exact verbage used, and I too, am no engineer.

I'll keep searching for that...

PolkWannabie

This might be a good one for one of the engineers at Polk to throw a few words at to allow us mere mortals to understand ... ( KEN YOU LISTENING ?) ...

PolkWannabie

Originally posted by steveinaz
If i remember the article right, I think its more about what the amp see's rather than the speaker. It had something do with amp recognizing that lower frequencies (on the mid/high crossover) were being "shunted" and therefore expending very little effort in these shunted frequencies--but like I said, I can't recall the exact verbage used, and I too, am no engineer.

I'll keep searching for that...

I hear what you're saying ... but without an active x/o in front of the amp then I don't see how the amp sees that something has been shunted by the x/o in the speaker unless the speaker is somehow able to convey that information back up stream like a feedback loop if you will.

Tour2ma

Found it or at least one from last August...

http://clubpolk.polkaudio.com/forum/showthread.php?s=&postid=111059#post111059

steveinaz

Excerpt from the Galen carol website:

Bi-Amping: Pleasure or Pain?

In the world of high end audio, bi-amping is (or has become) a very misunderstood concept. In an attempt to clarify the situation, we’ll have look at the ideal model, define it, and explore the advantages and disadvantages of implementation in a modern audio or video system. First, the definition and background.

Using two separate amplifiers, one for the bass frequencies, another for treble, is an idea that has been around for many, many years. In the professional audio industry (where the concept originated), using multiple amplifiers to serve different frequencies is more than just an option; in many cases an absolute necessity. Audiophiles and videophiles look at bi-amping (or tri-amping) as a way to improve performance, the pro audio industry sees multi-amping as a basic requirement.

Bi-amping or multi-amping (splitting the signal into more than two frequencies) is not only far more efficient, it allows a large sound reinforcement system to be scaled to meet the needs of the application. A traveling show, as an example, encounters many different venues, each with different requirements for good sound reproduction. Large settings demand more speakers to fill the space; some locales require a different mix of drivers to achieve the correct tonal balance (e.g. outdoor venues). A multi-amped modular system allows the flexibility required to fulfill the diverse needs.

The large scale systems for concert venues, auditoria, churches and stadiums require huge amounts of power to accomplish their given tasks. The number of speakers and amount of amplifier power necessary to fill a large auditorium or arena is mind boggling. Without multi-amping, the amount of power necessary would be exponentially greater. Why is this? The answer lies is an important part of multi-amping, and indeed the part of the puzzle most often overlooked by audiophiles; the use of the electronic crossovers.

Passive crossover networks found in consumer speakers waste an enormous amount of power. The often complex network is made up of large coils, chokes, capacitors and resistors. The circuit splits the full range signal into different frequencies (low, mid and high) appropriate for the different drivers in the speaker. Further, a crossover network compensates for efficiency differences in the drivers; woofers demand mode power than midrange drivers which in turn demand more power than tweeters, etc. Further, each of the drivers has different sensitivities, with some requiring far more (of far less) power than other drivers in the same speaker system. In a passive crossover, the excess power not required is dumped into resistors and burned off as heat. This makes for an incredible waste of power.

in addition, passive crossovers do much to degrade the signals that pass through them, and wastes a good deal of amplifier power, so bi-amping is an attractive idea. But there are pitfalls to be recognized before one embarks on that journey.

As we have seen, the key part of the equation is the electronic crossover. Splitting the signal at line level allows us to bypass the lowly passive network. So, buy another amp, an electric crossover and you are off to races. Ah, but it's not that simple. Now comes the task of calibrating the crossover to your speakers; making sure that the drivers are sent the specific frequencies their designers intended, and that slopes (the rate at which the transition between the frequencies occur, and how much they overlap) are correctly set. These adjustments are key to not only optimum performance, but system safety; operating a driver beyond its range will likely result in its failure. Maybe you've read the book, "Poof the Mangled Driver"?

Ok, so what about just using two amplifiers and forgetting about the electronic crossover? Simply using two amplifiers is not true bi-amping and does not offer the same advantages; we still face the limitations of the passive crossover. What about the notion that bi-amping reduces stress on the amplifiers since they are powering only limited frequency ranges? That would be true in a true bi-amp configuration where the frequencies are split ahead of the amplifiers, but in a passive environment both amplifiers receive a full range signal from the preamp and dump that power into the speakers, regardless of whether one is connected to the tweeter or woofer inputs. The only benefit (and it marginal at best) is simply the additional power offered by the second amp.*

Lastly (and maybe most importantly), the idea of using different types of amplifiers is a real issue. It has long been thought that the ideal situation was to use a sweet, refined low powered amp in top (tubes, for instance), teamed up with a powerful (usually solid state) amp to control the bass. This may indeed produce nice extreme top and bottom, but rarely did the two disparate sonic characteristics of the two dissimilar amplifiers mesh well in the critical midrange area. Further, matching signal level between both amplifiers extremely difficult, maybe impossible without sophisticated measurement equipment. So, more often than not, pseudo bi-amping, or poorly executed true bi-amping causes more problems than it cures.

In most cases, I am not a fan of bi-amping a high end audio or video systems. As we have seen, it can be a fairly complex (not to mention expensive) modification. Proper implementation requires the use of multiple amplifiers and an outboard electronic crossover. This mandates bypassing the internal passive crossover, which requires work inside the speaker, and will clearly void your warranty. There is significant expense in hardware: the additional amplifiers and crossover, not to mention the extra cables required. Further, we dramatically add to the complexity of the system. Though it can offer substantial benefits in the right set-up, in most every instance the listener is better served by using the funds to upgrade components in the system.

PolkWannabie

Thanks ... that brings some light to the subject.

So in essence my limited view is essentially correct in that ...

- Larger drivers use more power than smaller drivers which in turn implies that the load would be better balanced splitting left and right .vs. high and low ...

- Passive bi-amping while serving up additional power to the speaker overall will waste a lot in amping the high/mid frequencies because of the fact that although the power needs are less the whole range of frequencies will be amplified and it will be the x/o's job to in essence toss the frequencies it doesn't want from getting through ...

- Active biamping is a more efficient methodology but in turn has it's own set of more sophisticated problems and issues to deal with.

As far as my own situation goes, I have chosen to biamp my center and the satellites in the SRT's.

The first choice was easy, I had a spare amp channel and so why not.

The second is little out of the ordinary. The biamping that's going on is not about highs & mids .vs. lows per se but about the Stereo .vs. SDA arrays. There are at least two ways to hook these always separate connections on the satelites up. The first entails running speaker cable from the given amp channel output to the SRT control center which produces a modified output for SDA and basically leaves the stereo side alone. This in essence halves the power for the SDA & Stereo arrays. The second method entails running the given amp channel output to the SRT controller and the SDA only output of the control center to the speaker but when running the stereo side this is done directly from the amp by splitting the preamp output which results then in two channels of inputs to the amp or in essence the same wpc for both the SDA & Stereo arrays. So it becomes a matter of whether to use two different amp channels for the job and as a result twice the wpc or using one and having the control center feed both sets of terminals on the speaker each with half as much power. I elected to utilize two amp channels because the goal in this case was to get more power to the speakers which in the case of the SRT's can more than be handled.