Bi-Amping for Dummies

AngelEyes

Distinguished Member
In a recent post I was asking a few questions about bi-amping but after talking to a couple of manufacturers I am getting confused. Can anyone help?

On this thread I was lead to believe that you can bi-amp speakers with only a single set of terminals but when I talked to Gecko (M&K UK Distibutors) they said that doing so would simply make the second amp the load with the speaker, which doesn't sound good to me!

What I wanted to do was buy a second Rotel RMB1075 and bi-amp the front three M&K LCR850s leaving me four spare channels for surround duties.

Can someone tell me (please) if this is possible?

Many thanks
 
R

recruit

Guest
I was always led to believe that with single speaker binding posts it is not possible to bi-amp and if you were to connect 2 amps to the same speaker wire it would certainly cause problems for the amps and probably speakers...I remember once when bi-amping my old Cyrus 7 and smartpower amps i forgot to take the links off the binding posts which caused both amps to shutdown which is what they are designed to do as a safety precaution and luckily my ProAc D15's were ok..but it certainly made me take more time when setting things up in future...:rolleyes:

I hope we are not getting confused with Bi-wireing which is ok to twist the wires together...?
 

AngelEyes

Distinguished Member
Well that just saved me some money ;) , shame as I was looking forward to having 2 1075s on my rack :rolleyes: I have to admit I was of the same understanding, at least i know for sure now.

Out of interest does the addition of the Xenons for rear duties make much difference from 5.1; and are your Xenons monopole or tripole?

Perhaps I should get used to my CS first... just waiting for them to arrive!

Thanks.
 
R

recruit

Guest
tbh Angeleyes i hardly ever use the Xenons now unless i am watching an EX or ES encoded film which is not too often, the Columns are excellent for surround sound and really do envelope you in sound which is hard to locate (speaker wise) so you will not be dissapointed.
 

Member 96948

Distinguished Member
May I back up Recruit. You absolutely CANNOT bi-amp speakers with a single pair of binding posts. Each amp will see the other amp as part of the load and try to drive it. Unwise at best, messy at worst.

Biamping is where two amps are used for one channel. Each amp is fed the same full range signal which it sends to the speaker terminals. If the speakers are biwirable (ie four binding posts - which means entirely separate HF & LF sections in the crossover), the amp feeding the HF unit has the LF part of the signal filtered out by the tweeters crossover so only HF arrives at the tweeter and the amp feeding the LF driver has the HF part of the signal filtered out. The crossover must be able to be split in two (remove jumper plates) to allow this.

It follows that a three way, tri-wirable speaker is tri-ampable.

M&Ks for the most part, do not allow this. They are not unusual in this respect. They (and for instance ATC) have very high spec crossovers made to absolutely minimise phase shifts through the crossover region between the two drive units, to ensure even dispersion of all frequencies for all listeners in the room. It's this even dispersion that makes both of these manufacturers speaker remarkably non room dependant.

The ultimate extension of bi-amping is where the amps connect directly to the drive units and the crossover is placed BEFORE the power amps. This is Active amplification and is most excellent. The crossovers do their work on a much easier to handle line level signal and no power is lost as heat in lossy speaker crossovers. Active amplification always goes ALOT louder than it's specs will suggest.

I digress.

What you could do, if you really want to spend more money and it does work, is either use a seperate stereo amp for the front pair such as a RB-1080 or buy a pair of RB-06s and bridge them to perform as mono amps - one for each speaker. I'd suggest the former as bridging dosen't quite deliver what it suggests when speaker impedances are already low - M&Ks = 4ohm?

The main gains from going the pre/pro route such as you have, is the isolation of power supplies between the different stages of amplification, allowing each amp to work with an optimal clean supply of power of it's own, unencumbered and uncompromised by the demands of other amps. Separating the power amps is the next stage along this path. A loud scene using all five speakers will drop the power available to each of the other speakers being used. Powering the fronts from their own amp(s) will give an increase in headroom, reduction in distortion with the added bonus of improved imaging and seperation at all volume levels.

It may seem wasteful having a couple of channels going spare in the 1075, but the center speakers output will benefit and you could always go 7.1 with the spares.

Just a thought.

Russell
 

AngelEyes

Distinguished Member
Hi Russell,

Thanks for the advice. I think the optimum for me would be a 3 channel amp (perhaps the Rotel RB993 if I can find one, 3x200W) and use four of the 1075 channels for rear duties.

Until I find/decide on the extra amp i will probably just enjoy the 5.1 setup for now.

Thanks to both of you for clearing that up, I was sure I couldn't do it either but when someone says you can... forums can be dangerous :D
 

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