Bi-amping question

messiah

Hey guys, got a ? for you. I've done some searching here and it seems that the consensus is that bi-amping with a receiver is pretty much pointless. There is at least one current thread with this topic, but in an effort not to thread-jack I thought I'd start my own. Here's the deal: I have the demo pair of Tsi500's in my possession, and they are capable of being bi-amped, and are rated to 275 watts. My receiver is a Pioneer elite 7.1 channel, and I only run a 5.1 setup do to the shape and size of the room in my condo. The receiver has an option in the setup to use the back 2 channels to power the fronts in bi-amp mode. This is how I have it currently set. Now here's the question: Lets say a receiver is capable of 100 watts per channel, all channels driven, and you're only using 5 out of the 7, why wouldn't the extra 200 watts re-routed to the front make a difference? The power supply is obviously able to handle it, and the receiver would feed the back speakers with 100 watts of power in 7.1 mode, so what keeps the fronts from receiveing 200 watts bi-amped in 5.1 mode? Based on the search I did, I already know I'm going to have responses like " just try it", and I do plan to. I'd just like to know the science behind it, not only for myself, but for friends of mine that may have the same question.

Thanks in advance, Christopher.

wutadumsn23

As you have stated, Bi_amping with an AVR IMHO is not going to make much of a diff. While on paper it would seem that you have an extra 200W out there not being used, but that is not the case. Your AVR has only one power source that powers all 5 (or 7) channels, and simply hooking up some speaker wire to the unused channels (typically the Surround Back L/R) isn't going to channel that 200W to your fronts. If it were that easy to gain an extra couple hundred watts of power external amps would be a thing of the past (not really but you see where I am heading with this, lol) You can try it as all of the other threads have suggested, but you won't gain much (or anything at all) IMO. I too don't know the "science" behind it but I know the main limiting factor is not having a power source for each channel (like an exteranl amp does) is my best guess.

Oh and hurry up with those 500's lol, I am on the list somewhere.


-Jeff

Marty913

As Jeff said, you won't pick up what you think you might. Here’s a simple example. Won’t fit all scenarios and certainly doesn’t go into the science behind it but does give you an idea of the trade-offs involved.

Using a brand-name 100 watt per channel receiver from earlier this year that was tested by Sound & Vision magazine, the real distribution of power was 100 X 2, 45 X 5, and 35 X 7. Using those numbers for example:

A 5.1 setup would generate 45 X 5 = 225. A Bi-Amp 5.1 setup wound generate Left=70, Right=70, Center=35, and Surrounds=35 each for a total of 245. Yes, you would pick-up 20 watts overall and more in the Mains. Of course you would lose in the center and surrounds, create a wattage imbalance (probably not a big deal), and probably reduce your overall receiver headroom since you would now be using the full output capacity of the receiver power supply.

Whether this all matters, sounds better, or is a worthwhile trade-off is all up to you.

Marty913

Just another note (too late to edit above post), all receivers are different with the better ones getter closer to the "all channels driven" numbers versus the variations between 2, 5, and 7. Still, you really have to know the real tested characteristics of a given receiver to evaluate whether bi-amping is right for you. You will almost always pick up watts. The real question is how many, and what are the trade-offs. I think my point (and Jeff's) is valid - that there is NOT a couple hundred watts laying around unused.

comfortablycurt

The only thing that would make it worthwhile, is if your AVR has a separate monoblock for each channel. Otherwise, bi-amping with an AVR is completely pointless IMO.

messiah

Thanks to all for the input, and I expected to hear what you've told me. I'm just looking for the "why". The receiver I have has bi-amping built in to it as an option, and I'm not sure why they would do that if it was useless. I'm not doubting any of you, and have been looking into external amplification, but would like to better understand the science of it. In other words, a 700 watt 7.1 channel receiver rated at 100 watts per channel, really isn't capable of producing that? And if it is, if you re-route it from the back channels, it isn't any help? Just trying to figure it all out. Thanks guys!

comfortablycurt

Well...most AVR's draw power for all channels from a single power block. With the speakers hooked up to a single pair of outputs, they will already be drawing the maximum capable amount of wattage.

When you connect them to a second pair of outputs, they're still drawing all of their power from the same common powerblock. The maximum available power from the amp hasn't changed at all, and the speakers are still going to be drawing the exact same amount of power.

The only exception to this is AVR's with individual mono-blocks on each channel.

Most AVR's don't even produce their rated power. Most of them can produce close to the rated power with only 2 channels driven...but most even fall a bit short there.

The theory behind "bi-amping" with an AVR is more centered around providing separate signals to the woofer, and the mid/tweeter array. Bi-wiring would be a much more proper name for it. The effects of bi-wiring are a somewhat debated subject.

I tried bi-wiring my RTi8's, and found there to be no improvements. If anything, the mid-range seemed a little bit drier and more withdrawn. Definitely not an improvement.

Other people have claimed big improvements with bi-wiring though, so it's worth a shot.

The way I see it, the bi-amp feature on AVR's is basically a marketing strategy.

wutadumsn23

comfortablycurt wrote: »

The way I see it, the bi-amp feature on AVR's is basically a marketing strategy.

Sounds like a valid point to me, with only one power source built into the AVR, it would have to be IMO.

Marty913

messiah wrote: »

Thanks to all for the input, and I expected to hear what you've told me. I'm just looking for the "why". The receiver I have has bi-amping built in to it as an option, and I'm not sure why they would do that if it was useless. I'm not doubting any of you, and have been looking into external amplification, but would like to better understand the science of it. In other words, a 700 watt 7.1 channel receiver rated at 100 watts per channel, really isn't capable of producing that? And if it is, if you re-route it from the back channels, it isn't any help? Just trying to figure it all out. Thanks guys!

I think the "why" is really "why not". In other words, it's like Curt said, a lot of it is marketing. Once you have added the 2nd zone channels which is worthwhile, it's pretty easy to sell that feature as a "way to get more power" for those people without 2nd zone needs. It only requires a simple redirection circuit and a menu option. Bi-Amping and Bi-Wiring for years have been associated with higher-end equipment, audiophiles, etc. so being able to advertise that capability in a low-mid-prices receiver is a "why not" feature that's more marketing oriented than sound-based.

I will say that IF you have a receiver that actually produced 100 watts (or whatever) on every single channel with all channels driven at rated distortion - then it may be a worthwhile effort. Most mid-range receivers do not meet those requirements.