Bi-wire

rnp614 · February 2005

If I split the signal for my left and right fronts coming out of the preamp and plug each of them into a channel of my amp, could I plug one into the high and one into the low plug of my LSi9s thereby doubling the power I'm giving them? My amp is an 100x5.

dorokusai · February 2005

What are you using for amplification? What AVR?

rnp614 · February 2005

i have a Rotel RSP980 as the preamp and a Carver AV-505 as the amp. It was tested at 103Wattsx5channels by sound and vission.

rnp614 · February 2005

oh and the reason I'm doing this is that I dont have rears. I'll just have 2 LSi9s and a CSi30 thats just layin around.

dorokusai · February 2005

In order to "Bi" anything, it must come from the amplifier, not the pre-amplifier.

rnp614 · February 2005

yeah thats what i'm saying...let me try this again. What I mean is I split the signal from the preout thereby having the amp receive 2 left front and right front signals. Meaning I have Left and Right main EACH going into 2 channels on the amp. Then I have 2 sets of speaker wires going into each speaker from those amp sections. One into the upper set of bind posts of each speaker, one pair to the lower of each speaker. Is that doable? Dangerous?

rnp614 · February 2005

maybe this will make more clear what i'm trying to say...maybe not

dorokusai · February 2005

You are Bi-wiring, not Bi-amping. You cannot Bi-amp with that Carver. You need two amplifier sections to Bi-Amp, or two individual amplifiers....as in monoblocks or bridged amplifiers.

It doesn't matter how you split the input signal, it is dependent only on the output signal of that amplifier.

rnp614 · February 2005

Thats what I meant maybe? To bi-wire. Is my diagram doable them? Would this damage the speakers in any way? Or is this actually preferable. Would using an adapter to split the RCA's into 2 left and 2 right signals cause too much degradation?

I'm not so clear on what you mean...it only matters what the amp is putting out? If i give the amp 2 signals for left and 2 signals for right I still cant bi-amp?

Sorry to belabor this but i'm just not getting it.

dorokusai · February 2005

You mentioned "doubling the power" earlier....so that's what I was trying to clear up.

There is no real reason to split the pre-amp outputs for your application....it might increase the gain, but otherwise it's not useful.

rnp614 · February 2005

ah ok, i just thought that by doing this I would give these speaks more power and therefore possibly a better sound.

Whadyasay · February 2005

I believe that what you are doing is called 'passive bi-amping', in which the high and low frequency drivers of your speakers are each getting power from their own amplifier channel. I think true bi-amping involes the addition of an external active crossover that filters out frequencies that are not within the range of the specific drivers...probably run between the preamp and power amp. Here's a link to a thread that explains it.....

http://hometheaterhifi.com/forum/archive/index.php/t-503.html

and a dedicated page....

http://sound.westhost.com/biamp-vs-passive.htm

rnp614 · February 2005

do some Pre/pro's actually have a high freq preout and a low freq preout?

rnp614 · February 2005

yeah ok, now THAT clears up why what I'd be doing wouldnt work as intended.

unc2701 · February 2005

What you're describing is Bi-amping. Done right w/ an active crossover you will see noticable gains. Done how you're describing you will see some gains. The major difference will be that each channel will see an 8ohm load instead of the 4ohm load. Your carver probably does ~175 watts into 4 ohms and 100 watts into 8 ohms, so:
1) You'll have a much easier load and
2) You'll pick up 25 watts (100X2 vs 175x1)

So you might get some slight gain. Give it a try & let us know what you think!

oh, and you probably know this, but be absolutely certain you remove the binding straps on the posts.

gatemplin · February 2005

unc,

An 8ohm woofer and a 8 ohm tweeter in parallel are still 8 ohms.

The LSis use a 4 ohm woofers and a 4 ohm tweeter.

rnp614 · February 2005

would you guys recommend this passive bi-amping in this case?

gatemplin · February 2005

You've got the extra channels, go for it. Cant hurt, tell us what you think.

rnp614 · February 2005

yeah but i gotta buy somethign to split that female RCA

Tour2ma · February 2005

Yup, split away...

With your 5-ch Carver, you have bi-amp capability in one unit with a channel to spare. I do something similar with my 5-ch Sunfire.

As for needing an external cross-over... true bi-amping or not, not employing one is what the vast majority of we "bi-ampers" do. Given that a speaker's internal cross-over is in play, adding a 2nd one between the Pre-amp and amp is problematic.

Enjoy...

rnp614 · February 2005

any particular splitters u guys like? The ones off dayton? or the ones like from radio shack? I might actually need a cable from dayton so if you think those are good I might do it.

rnp614 · February 2005

also, finally, how much more power does bi-amping in this way get me? The only reason I'm doing this is that I hear LSi9s are power-hungry, I was hoping that this would help satiate them.

unc2701 · February 2005

gatemplin- two 8ohm speakers in parallel= 4ohms.
1/(1/8+1/8)=4ohms Trust me, or look it up, you can find plenty of circuit calculators on the web.

Two 8ohm speakers in series=16ohms.

Those binding straps have the speakers in parallel... Now the woofer circuit and the tweeter circuit might not both be exactly 8ohm, but they each MUST be higher than 4 ohms for them to parallel to 4ohm nominal.

rnp614- see what your carver will do into 4 ohms and what it will do into 8 ohms... the amount of power you pick up will be about 2x(8ohm wattage)- 4ohm wattage. It probably won't be much. However, you LSi9 will go from a hard load to drive that'll trigger a thermal overload occasionally to an easy load to drive.... ie, not so power hungry. So for the cost of two splitters, it's worth a shot.

rnp614 · February 2005

Ah, right thanks for the explanation

rnp614 · February 2005

putting in the order tonight

gatemplin · February 2005

Originally posted by unc2701
gatemplin- two 8ohm speakers in parallel= 4ohms.
1/(1/8+1/8)=4ohms Trust me, or look it up, you can find plenty of circuit calculators on the web.

Two 8ohm speakers in series=16ohms.

You have obviously never built speakers before. Two 8 ohm drivers in parallel have an 4 ohm DCR. An amp doesn't see DCR, it sees impedance in an AC circuit. A 4 ohm tweeter and a 4 ohm woofer combine for a total of 4 ohms impedance. Trust me.

unc2701 · February 2005

oh, crap... forgot about the crossover... You're right- the formula only applies for shared frequencies. I was thinking of speakers as a whole where each unit which would cover the full spectrum.

My bad, I flaked on that... I guess that would be another advantage of bi-amping- you don't get the problem of the impedence dropping around your crossover frequencies... which will make your speakers a little easier to drive.

So ignore what I said about the power.

Whadyasay · February 2005

I was considering going with passive biamping a while back, but it seemed that you should ideally have identical amp channels driving each driver. So if I were to get another amp, it should be the same as the one I have (Marantz MM9000), or use multiple channels on the one amp. Aside from power, different makes/models of amps have different input impedences and gain characteristics.

However, someone else told me that if you get amps with variable outputs (volume dials on the back), you could calibrate to the same level with an SPL meter (e.g. to 85dB) for each amp into the speakers by themselves and then go from there, but there's a chance that at a given preamp volume other than that used for calibration, the level ouput of the two amps would be mismatched. Seems like it would be easier and more cost effective (at least for the affordable Lsi's as opposed to more exotic hi-end multi-driver speakers) to get a more powerful single amp.

Many powered monitors, like ones used for professional sound mixing, are true biamped systems. But their electronics and crossovers are all specifically designed for that system and self-contained. Even though they may distribute their power more efficiently, most are near-field monitors that would probably require considerably more power for listening more than 6 feet away, thus requiring larger enclosures.

Like many have said, trying passive biamping probably couldn't hurt, but if you don't notice a night & day difference, don't be surprised, and try not to convince yourself that you have to take more steps ($$) towards what would ultimately be the same thing.

Bi-wire

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