[Phil P]

I have a pair of RM-40's(TRT,FST). They are currently being driven by a Mark Levinson #335 stereo monaural amp(500watts into 4 ohms-no gain control) with a Lexicon MC-12B as my preamp. I am thinking about biamping. I have two Proceed HPA2 amps (2-channels each-also 500watts into 4 ohms-no gain control) available. My options are:

1) keep everything the same (ie. do not biamp)

2) biamp passively with the two identical proceed amps

3) biamp passively using the ML #335 for the bass and one of the Proceed amps for the midrange/treble

4) biamp actively with a Marchand electronic crossover using the ML #335 for the bass and one of the Proceed amps for the midrange/treble

5) biamp actively with a Marchand electronic crossover using both identical proceed amps

Any experience or recommendations on what to do?

[zybar]

Phil,

The easiest thing to do is passively biamp.  Any other way wil require an external crossover which will also mean making some changes inside the speaker to bypass the internal crossover.

However, do you like the Levinson amp more than the Proceed?  

What are you hoping to gain?

I thought about the biamp route since my Kora Cosmos amps (tubes) just didn't like running full range on the 40's.

At the end of the day, I decided I didn't want to be hassled with biamp and external crossover so I went with Rowland 201 mono blocks and I couldn't be happier.

Another member (Horsehead) just got the 201's and when he compared them to his Pass X350 amps he preferred the 201's.

Hope this helps.

GW

[Sedona Sky Sound]

First, if you are not already bi-wiring the RM40s with your ML 335, then that is the first thing to do. Giving a fat cable to the bass and a skinny cable to the mid/treble does wonders on the RM40.

Next, just try passively bi-amping with the ML335 on the bottom and the Proceed on the top. I have not looked at the specs, but the actual gain on each might be close enough that you can use the pots on the RM40 to make up the difference. Even if they are not exact, you may want to just use the amp with the highest gain on the bass section (since + dB on the bass is prefered by many people).

Best of luck.

Julian  
www.sedonaskysound.com

[Phil P]

The easiest thing to do is passively biamp. Any other way wil require an external crossover which will also mean making some changes inside the speaker to bypass the internal crossover.

However, do you like the Levinson amp more than the Proceed?

What are you hoping to gain?

Thanks for the reply GW. How do you bypass the internal crossover? And, I do like the ML amp a lot. I am hoping that biamping will give me even more resolution and clarity.

Julian-Do you feel biwiring is better then using single wire with a high quality jumper? Also, with passive biamping, is the matched gain between two different amps the critical factor? I thought with passive biamping, it is important to use identical amps.

Phil

[PLMONROE]

Actively biamping will reduce intermodulation distortion. It will give flexibility in matching up the channels if using diferent amps. Basically you have to shortout a big coil inside the RM-40. I did in in conjunction with adding TRTs and found it very easy to do. Big B can give you the specific steps.

Paul

[John Casler]

Actually the RM40 is designed to be either biamped or biwired simply by flicking the toggle switch.

Zybar is correct, No outside x-over is needed, unless you wish to overide/change the factory set x-over frequency.

I think Julian nailed it and that you should just hook it up and give it a try and see if there is any problem.

I have taken a 60wpc Bryston and a 300wpc CineNova and horizontally biamped and beleive it or not it sounded well balanced.

I have also vertically biamped with two 125 wpc amps and got the same result.

So just try it and see how it balances.  If you do use an active x-over just for controlling the woofers gain levels, make sure and cross it over well above the 166hz, or you will lose valuable upper bass due to the x-over's slope.

So in essence, your only concern need be balancing the SPLs of the top and bottom, if the amps are dissimilar in their sensitivity/gain specs.

[rblnr]

Probably not what you want to hear, but having owned the MC12B for a long time, I'd look at something else as a front end DAC or preamp, however you're using it, to feed the 40's for music listening.  I own 40's, and I know firsthand that changing this can do a lot.

If you're interested in what I've listened to vs. the Lex. A/B, and where I ended it up, PM me.