Bi-Wiring - question

I’m no electrical engineer and I’ll not try to put myself over as any kind of expert but I understand Bi-amping to be using two amps. Basically taking advantage of the two speaker posts on a speaker to connect left/right from two different power amps. Essentially doubling the power that is driving the speakers by using two different amps. There is some thinking that using multiple channels on an AVR is a way to bi-amp and there fore send 4 channels of power to two speakers.

I say it’s all foolishness. I prefer to use equipment as designed and if I need it to sound better, I just buy better equipment. I do enjoy experimenting, I may run A and B speaker posts from my old Sansui to the biwire post on my speakers to see what happens but that wouldn’t be bi-amped because I’m just dividing the power of the Sansui. It only makes 110 wpc.

 

Bi-amp means two amplifiers as in two separate amplifiers each with its own power supply. Using multiple channels sucking off a single power supply such as found in an AVR is most definitely not bi-amping. In fact, when using an AVR the more channels used means it provides less wpc because of that single power supply. The result of multi-channeling (not bi-amping) is the bottom end is getting less power than it would otherwise.

You cannot rob Peter to pay Paul.

 

Your point about the power supply is a good one. In the case of an AVR, I had one that had a five channel stereo setting. I was using a separate power amp that measured 220wpc on a bench test, it Absolutely sounded like it was sending equal and full power to each of the five speakers in the room. If I were to take four of those channels on the power amp and send them to two speakers with the bi-wire connections, why wouldn’t that be bi-amping? I would be sending more than 400 wpc to each speaker where before it was 200.

Also, I would never do this. Just asking. although...I have heard Maggie’s like 400wpc.

 

It's not really as bad as all that. Only 2 channels need juice from the power supply; the other 2 feed next to nothing to the tweeters so most of the PS reserve is still available for the bass.

 

My Pioneer SC LX-76 AVR from 2012 has the option of bi-amp the two (left and right) or three front channels (l+r and the center speaker), what they do in this mode is instead of feeding 9.1 channels as in surround (it has 9 internal Class D power stages) it uses two of its power stages to feed a single speaker. I have tried all the possible connections, single wiring, conventional bi-wiring and bi-amp and I like how bi-amp sounds, it sound is cleaner and it has a wider soundstage.

 

A multi-channel power amp is a different beast than a multi-channel AVR. Generally speaking, the power supply in a multi-channel amp weighs more than an entire AVR meaning the power supply is beefy enough that it will drive all the channels without running out of juice.

Most multi-channel amps are using a single power supply, so it's still not really be bi-amping.

There are only two arrangements that can be called bi-amping, both require 2 separate amplifiers. You have passive bi-amping where the original crossover is used and true bi-amping where active crossovers are used.

 

That's multi-channeling not bi-amping because there is only one power supply.

 

So ok, let's say an AVR is rated at 120wpc, 2 channels driven at 1kHz. 5 channels driven it drops to 80wpc and with 7 channels driven it drops to 60wpc. That is very typical of all but the very best AVR's. The bass has to suffer.

 

I think you’re confusing the AC speaker circuit impedance with the DC loop resistance of the speaker cable. They’re two very different things. Sound electrical theory and practice specifies that as the gauge of a given quality wire (speaker wire in this case) increases in cross-sectional diameter the resistance decreases. You can measure it, I can measure it, anyone can measure it. For the record, DC loop resistance is the total resistance through two conductors looped at one end of the link. It is commonly a function of the conductor diameter and varies only with distance.

And what do you think you’re measuring? Anyway, DC loop resistance is a measurement taken by using a suitable (DC) battery-powered VOM to run a fixed voltage through the wire from one connector at one end of a speaker cable leg to the other end of the same leg and using the VOM probes as contacts to feed the result to the VOM.

What you’re failing to account for is the fact that the amplifier does not care about your connection. It outputs its signal into two pairs of cables and therefore sees a lower resistance electrical path. It is unlikely to make an audible difference of any kind if the gauge of the original single run of cable was already of sufficient size for the length of the run.

Anyway, all audiophiles should be aware of the fact that speaker cable resistance starts to have an effect on the performance of a speaker when it is greater (measured in ohms) than 5% of the overall speaker circuit impedance (also, confusingly, measured in ohms). As long as the speaker wire being used is 5% or less of the system impedance, the cable should effectively disappear and be inaudible. Bi-wiring thereafter might make a psychological difference, but it won’t make any measurable audible difference. Good quality connectors matter too, but that’s another subject.

Your example isn’t relevant, especially if the the runs of 12 gauge cable are already sufficient (given the length of the particular run) to avoid any appreciable resistance and therefore also aren’t increasing the overall system impedance.

At typical home speaker cable runs of 6’-12’, a 12 gauge speaker cable is more than sufficient. If, on the other hand, a run of 16 gauge cable is 50’ or more (because the wire, e.g., is routed through the walls and over the ceiling to get to speakers at the other end of a large room), that 16 gauge wire won’t quite do it and there will be noticeable reduction in volume for a given amp output. Replacing the wire with 10 gauge or larger lowers the DC loop resistance that the amplifier sees and corrects the overall AC speaker circuit impedance (because the large diameter wire also reduces the overall impedance of the circuit compared to the smaller diameter 16 gauge wire). That’s a good thing.

All of this is plainly measurable (and plainly audible in the extreme examples I offered) and well supported by the generations of engineering and electrical theory behind it. Any competent electrician or electronics technician will validate it for you. I’m not sure where you got the idea that it’s all an old wive’s tale but that’s not correct.

 

From an acoustical standpoint, 7 x 60 into a listening space sounds a lot better to me than 2 x 120. Nevermind that a test like this, of necessity, ignores the frequency variations in each channel when reproducing music. A 60wpc for bass plus 40wpc for treble has effectively the same power as 100wpc running full range.

I agree that discrete amps is best. For most of us it's the ubiquitous stereo amp with one PS. I had good luck with 1 amp driving mids horizontally and 2 smaller but identical ones driving bass/treble vertically in an active triamp system. It had incredible dynamic resolving ability with fairly little fade at high volumes, but one thing it lacked is tonal cohesion across the instrument spectrum. There are plenty of reasons why that would be, but some say this also describes a failing of simple bi-wiring...lack of cohesion.

 

Our host and another member had similar experiences: Anyone NOT Impressed With Bi-Wiring?

I am posting that (and another post from our host below) here because I almost spent a good deal of money recently on a second set of speaker cables, but reading the above helped me see that it would not be a wise choice for me, as my system already has plenty of mids and top end, and I wouldn't want more of it.

I also found this post on bi-wiring helpful, so I figured I'd share it here:

 

I also read this over at Bowers and Wilkins, one company that advocates bi-wiring:

 

Ok, so let me ask this: if i'm using 2 14 awg sets of cables in a biwiring combination, does this equate to 11 awg cable? Since there are 2 strands of 14 awg?

 

No. As has already been explained, each strand passes a different frequency spectrum, so the amp sees the same gauge across the spectrum. In other words, 14ga bass plus 14ga treble equals 14ga full range.

 

How come? 14 awg is basically 2 sq mm. 2 strands of 2sq mm equals 4 sq mm (around 10 gauge or so), so there s 4 sa mm of wire now, handling all the signal, from the amp to the speaker. I dont see how its its s 14 gauge (2 sq mm) when its actually 4 square millimeters of diameter....?

 

If you combined the two runs so they joined together at the binding posts by keeping the jumpers in place then, yes. Otherwise, no.

 

For DC, yes, but we're discussing AC with a wide spectrum. Bass travelling through one cable doesn't benefit from the cable supplying the tweeter.

 

Except leaving the jumpers in place is not what most people mean when they discuss bi-wiring.

 

True, but he was asking about wire gauge.

 

If he wants to double up the runs to each driver, then yes, the gauge increases.

 

....thats precisely what i was asking. I've got my speakers bi wired through vdh clearwater (14awg) - connected at the amp level to both A and B set and to both low and high frequency binding posta at the speaker (bridge obviously removed) - in that case I assume I'm now using the equivalent of one 11awg cable.

 

If you've removed the jumper, the it's as I said above...the bass driver does not benefit from the cable supplying the tweeter, hence, no increase in wire gauge.

 

yes, 11
Wire Combination Calculator

 

Consider the following diagram:

Assume each leg is 14ga; the woofer has a 14ga wire and the tweeter has a 14 ga wire. What you wind up with is a woofer and tweeter with 14ga wire, not 11ga...

The web page that diagram comes from offers useful reading:

Bi-wiring Speakers: An exploration of the benefits -

 

Only if you leave the jumpers in place. Of course, then you are not bi-wiring.