Bi-Amping Front/Center on 7.1 System With 2 ROTEL RMB-1075

[Sl@mJ@ck]

Greetings Everyone, I am able to get a second ROTEL RMB-1075 Power Amplifier at a very good price. He is in mint condition, as mine. Does it make sens to use those 2 power amplifiers to bi-amping my Right/Left fronts and my center and use 4 channels left to power my Surround and new 2 Back Surround. I want to use passive splitters as XRCA-1x2 to plug RCA on my Sherbourn PT-7020A. All your comments are welcome, as well as feedback. Thank You

[repeetavx]

Stepped into the lions den have we. First, I hope that you already have the XRCA-1 splitters, because they haven't been available for months, and they don't know when they'll come in.

Next, I love biwiring/biamping. The RMB-1075 should work ok. But being an Emotiva forum, I feel compelled to mention that that much sound coming from out of such a "wimpy" amp will really (really) tax it.

[aboroth00]

I wouldn't bother passively biamping anything. Read up on the difference on passive and active biamping and you'll see active biamping (removing the internal passive crossovers and adding an external crossover) is the only way to go.

[zerafa]

What external cross over would you recommend?

[jackpine]

The op speakers are the weak link in his system. The most cost effective upgrade would be to replace them before he buys anything else.

To the last poster I see Behringer mentioned most often as making decent inexpensive ones. A lot of the inexpensive ones aren't very good.
Here's a good article explaining about bi-amping. sound.westhost.com/bi-amp.htm

[leonski]

The article linked is TOPS.

For the Cost-No-Object crowd, Pass Labs makes a crossover which is about a configurable as is possible to make. I think it goes for north of 1000$, which is pretty serious.

[audiosyndrome]

As Nelson Pass says "be careful what you ask for" as his crossover allows for greater than 1,000,000 combinations. ??

An NHT X2 analog crossover would make a good choice As would a Behringer digital crossover. 

Russ

[leonski]

A MILLION combos eh? There goes my Free Time for the next 60 years.

[leonski]

I KNOW its been nearly a year since this thread was active.
But new information means a new and much better answer.

First of all, Line Level crossover is the way to go. This consists of gutting the speaker crossover and DIRECT wiring to an amp channel. In the case of a 3-way speaker, replace the Bass to Mid/Tweet crossover while leaving the Mid-Tweet crossover alone. This means you need 2 amp channels per speaker. Books have been written about 1 stereo amp per speaker OR 2 amps with one channel from each to the bass and the Other channel to the mid/tweet of each pair of speakers. This is Horizontal vs Vertical biamping.

Now, you need a Line Level crossover.

I think that THESE DAYS the best or most affordable and flexible solution consists of MiniDSP. These are inexpensive boards which go between your amp and preamp. The 2-way solution would be the 2x4. 2 in and 4 out. While this is good and useful as a PAIR if you have say a 3-way speaker, the next model up called the 2x8 is very sweet indeed. It can be configured with balanced OR single ended connections and as with the REST of the Mini lineup, configured and programmed thru a PC or MAC. The software packages are 10$ per and very flexible. Each includes as many as 5 parametric channels per input AND output along with a massively configureable crossover section. The 1,000,000 combinations of the Pass system PALE in comparison.
ONE additional item is a Calibrated Mic which when implimented WITH a free program called Room Equalization Wizard provides a COMPLETE answer and allows multiple solutions.

The BEST first bet? Duplicate the crossover from the speaker. You'll still GAIN amplifier power based on no-longer producing out of band signals. Fine tuning is easy at that point and the computer can hold mulltiple configurations. Some of the MiniDSP products can hold as many as 3 configurations accessible with the optional add-on switch board. Any configuration from 6db/octave to 48db/octave of Butterworth OR LR can be accomodated.

www.minidsp.com/products/minidspkits/2-x-in-8-x-out

This is an intermediate DIY project.

[wilburthegoose]

Or just use a single amp and get 99% of the performance?

[leonski]

Actually, doing a proper biamp with a line level crossover can net as much as 3db additional 'apparent' amp power. The Flexibility which a miniDsp product with calibratin mic and REW brings to the table is well-worth the time and effort to do it right, IMO. Especially since you do it ONCE and when setup correctly, maintainance is zero.
I have 200x2@4ohm per speaker. This is roughly the same power output as the >2x more expensive A21 from the same line. After install / cal of a line level crossover? Easily nearly 2x the power. And my Panels can use it!

No question that a single amp solution is easy. or fast. Or even best for MOST.

The original poster asked about BiAmp. Going to a linelevel crossover solution would be one way to REALLY make the most of his ampliflier(s). I don't think using the multiple speaker binding posts on many speakers, including my panels, is necessarily a good use of extra amps. The gains are minimal.