Can I bi-amp like this...?

FranklinD · 04-04-2008, 01:11 AM

If I wanted to bi-amp my l/r mains in a 5.1 setup, couldn't I just use the DVD player optical out and go into my receiver, then hook the l/r outs on the DVD player into another amp? Of course from there I can send the signal to whichever set of speakers I choose. This is the only way I can think of to do this since my receiver isn't cut out for this task.

I've been reading for a few hours(mostly in random forums I guess) and this method has not been mentioned yet. There seems to be a bit of confusion about bi-amping in general on a lot of forums.

The crossovers in the speakers would be used though, right? Is this necessarily a bad thing though? I mean, if the speakers were built with two sets of terminals, wouldn't they take into consideration that a lot of people would use them bi-amped?

Hmmm...?? Can someone shed some light on this? Thanks!

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troy evans · 04-04-2008, 01:36 AM

Removed

Allan Jayne · 04-04-2008, 12:40 PM

The L/R outputs going to a separate amp should work out quite well.

A crossover is still needed before the midrange and tweeter speakers. The crossover is used here to block lower frequencies that would overload and burn out those speakers.

If the speaker unit has two sets of terminals that are connected to each other, those terminals are meant only to accept one amplifier channel feed together with a daisy chain to another speaker system. Do not connect two different amplifier channels to those terminal pairs respectively. You will need to rewire the speaker system so one set of terminals goes only to the woofer and the other set of terminals goes only to the crossover.

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FranklinD · 04-04-2008, 01:51 PM

I've noticed that most speakers that can be bi-amped have a strip of metal to connect the like terminals together. You're saying that just removing the strip of metal between the posts and hooking them up like I described above isn't really the best option then(which would use the speaker crossovers)? Like, in a 3 driver speaker with a tweeter and midrange driver hooked to one x-over and a bass driver hooked up to a separate x-over, wouldn't that take care of what frequencies go where(to a point at least)?
I'm thinking another issue would be getting the surround/center speakers balanced to the l/r set of speakers hooked up to the receiver since it's all on one volume control.
I think I'm missing the point. Heh. Thanks.

JohnRice · 04-04-2008, 04:22 PM

No, the method you describe in your initial post is NOT the proper way to bi-amp and it could result in tragically screwed up sound. Beyond that, essentially everything that has been posted so far in the thread (I don't know about Troy, since he deleted his post) is incorrect.

If a speaker is configured for bi-amping, it will have two sets of connectors with jumpers connecting each positive and neagtive set. To bi-amp, you remove the jumpers and feed them with identical signals, coming from two identical amps. You can't do this with just any piece of equipment you have sitting around, and most lower end receivers aren't even capable of configuring this setup. You are FAR better off in virtually every situation to just use a better, single, power amp to power the speakers conventionally. Of course, from previous experience, I have found that when someone gets the idea to bi-amp speakers, they are hell bent on doing it regardless of the risk of destroying their equipment or if there will even be any sonic improvement.

FranklinD · 04-04-2008, 08:42 PM

I see what you're saying. But...
The amps have to be identical to do this? Seems like they could be similar in output and work fine(I don't know though obviously).

Also, isn't the optical out and the composite outs on the DVD player the same signal? As in, what you hear from them will be ultimately be interpreted as the same analog sound.

I still don't understand how it would be possible to do this without a high end receiver. Actually, I still don't even know the proper way to even do it at all...
And I don't see how I'm going to damage something unless I crank it too hard or use mismatched stuff.

Now do you see what I mean about the confusion in forums?

Thanks for replying.

Allan Jayne · 04-04-2008, 09:32 PM

I don't think you need identical amps.

If amplifiers of different powers are used, arrange the inputs so that the higher powered amp channels go to the woofers.

You might even use unused channels in the same amplifier unit for biamping, for example a 7.1 amp feeding a 5.1 system has two leftover channels. But there must be individual inputs for each channel in order for you to do this.

FranklinD · 04-04-2008, 10:09 PM

I've read about using the left over channels in a 7.1 receiver to bi-amp. I've only a 5.1 so that isn't an option for me. I wish that speaker b was actually a separate amp and I could use it with surround. Oh well, maybe more expensive receivers can do this?

Not saying anyone's wrong here but I agree that the amps wouldn't have to be same. My, probably flawed, thinking is power is power.

Now I'm confused about whether or not I should use the l/r outs on the DVD player for this. I'm thinking that the composite signal would be identical to the optical signal. The signals would just be processed in a different way in the DVD player but I'd think that the actual signal would be the same because they, well, sound the same. Or no?

Yeah, this might end up sounding like crap but I don't think I'm going to destroy anything. I'm just experimenting folks.

Wayne A. Pflughaupt · 04-05-2008, 12:18 AM

Quote:

Now I'm confused about whether or not I should use the l/r outs on the DVD player for this. I'm thinking that the composite signal would be identical to the optical signal.

It isn’t. The former is two-channel analog. The latter is a digital signal that is decoded to 5.1 analog channels by a Dolby Digital processor. What would be coming from the front two channels from the digital output would be much different from what’s coming from the L/R outputs.

You can check it yourself by plugging the DVD player’s L/R outs to a separate input on your receiver. Compare that input to the DVD input with the center channel disconnected.

The reason you can’t really use the DVD L/R outputs in the manner you mentioned, “hooking the l/r outs on the DVD player into another amp” is because you’d then have two separate and fully independent volume controls. Not a pretty picture, having to turn the tweeters up separately from the woofers...

Regards,
Wayne A. Pflughaupt

JohnRice · 04-05-2008, 09:57 AM

Quote:

Originally Posted by FranklinD

Not saying anyone's wrong here but I agree that the amps wouldn't have to be same. My, probably flawed, thinking is power is power.

Yeah, this might end up sounding like crap but I don't think I'm going to destroy anything. I'm just experimenting folks.

The problem is, you are asking questions when you think you know the answers already. Wayne already pointed out the significant problem with one approach you suggested. I will continue. The amps for bi-amping really do need to be identical. Power is NOT power. The most significant aspect which must match for both amps is the gain. It is also ideal for every other aspect to match, such as how the amp responds to varying loads. In theory, you could find two different amps which would match for bi-amping, but it is just simplest to use matching units, or four channels from a multi channel amp, as mentioned.

And yes, you CAN destroy equipment. If you don't know what you are doing and mistakenly run two amps head-to-head into each other, which is a distinct possibility when you are bi-amping and don't understand how it works. Also, the jumpers and multiple speaker inputs are most definitely NOT for daisy chaining, which can also lead to destroying amps.

Wayne A. Pflughaupt · 04-05-2008, 11:40 AM

To hopefully further explain what John said, “The amps for bi-amping really do need to be identical. Power is NOT power. The most significant aspect which must match for both amps is the gain.”

When you biamp, the amp’s levels need to matched so that the tweeter’s volume is correct in relation to the woofer. This is done via the amp’s input stage, as some amps are more “sensitive” to the input signal they are fed (a.k.a “gain”) than others. IOW, in order to be driven to its maximum output level, some amps require a hotter input signal to accomplish that, others require less.

Most pro audio and car audio amplifiers have “gain” controls to adjust the level of the input signal. Curiously, many (if not most) home amplifiers do not. And this is why you would need both amps to be make-and-model identical if you biamp: If they are not you may end up with a mismatch between the woofer and tweeter levels – the tweeter being way too loud, for example. If this happens, you would have no recourse for balancing the levels between the tweets and woofs. Using identical amps, this problem would not occur.

Hope this makes sense.

Regards,
Wayne A. Pflughaupt