Start with biamping the RM40's?

ctviggen · « **on:** 6 May 2004, 03:22 pm »

I have a Jeff Rowland #10, which is 275 W/channel at 4 ohms and has two channels. I also have a Lexicon NT512, which is really a Bryston 9B. It has five channels and is listed at 200W/channel at 4 ohms, although the test results that came with it listed it about 40W/channel higher than spec. at 8 ohms. I currently use only three of the Lexicon channels. I was thinking of biamping the RM40s when I first receive them, using a channel of the Lexicon for the bass and a channel of the JR for the mids/tweeters (I'd use the JR because it's sweet sounding in that range).

Should I do this or just try the JR at first?

The reason I ask is that I have to reterminate my speaker cable to go from triwired to biwired and it would be just as easy to make the wire biampable. Also, it's a freaking pain to get to the JR, as it's on the bottom of a rack of gear -- it takes me several hours to get to the JR and put everything back together. So, if I want to biamp in the future, I have to do all this stuff over again. (The only detriment to biamping is that I'd have to buy XLR splitters and new XLR cables or new XLR Y cables.)

Thanks for all suggestions!

zybar · « **Reply #1 on:** 6 May 2004, 03:51 pm »

Bob,

I would try single amp first. Your life will be much easier that way.

If you do have to biamp, how will you control the volume of the individual amps? The two amps won't match otherwise.

George

Sedona Sky Sound · « **Reply #2 on:** 6 May 2004, 04:30 pm »

If you were using the RM/X, then I would say that bi-amping is absolutely necessary to get the best possible sound. With the RM40, it is not quite as important. You can squeeze the last little bit of performance out of the RM40 with a bi-amp configuration, but in many cases it is actually possible to do more harm than good. When I use 4 Ampzilla monoblocs I got an incremental improvement but when I mixed and matched other amps into the mix I thought the standard dual Ampzillas was just as good. My personal recommendation is that if you have a high quality, high current amp, then there is no need to bi-amp. If you have a cheaper amp or want to run tubes, then bi-amping becomes important.

Properly bi-wired with a high quality amp like the JR, the RM40 should sound great. When I say "properly bi-wired", I mean give the bass a big thick wire (10AWG or so) and the mid/tweeter a much thinner wire (14AWG or 16 AWG). The fact that some manufacturers use the same size wires for both really amazes me. You will get a slight improvement using the same size wire (probably since you are bypassing the internal switch on the RM40) but not the full benefit.

I hope that helps.

Julian
www.sedonaskysound.com

ctviggen · « **Reply #3 on:** 6 May 2004, 05:03 pm »

George,

That is a good point. I was just going to wing it for now to see what happened. If it weren't so hard to do, I'd do it just to try it. Maybe I'll use an extra amp from the Lexicon to biamp the RM30C (used as a center channel) for kicks.

Julian,

My cable is Linn cable made for my Linn speakers. I'm going to change cable in the future (I need another foot or so of distance), but for now I was going to basically rip off one of the three sets of wires (Linn's are tri-ampable). They are the same size. I'm not sure of the size of each wire, but it's thick and very heavy.

Thanks! So, I'll try one amp and see what happens.

zybar · « **Reply #4 on:** 6 May 2004, 05:23 pm »

Bob,

I tried the "wing it" approach and it didn't cut the mustard.

I know Julian said you can get benefits bi-amping (I agree with that), but you should think about the costs associated with doing the bi-amp and decide if the incremental improvement is worth it to you.

I realize you own the some of the gear needed, but you will need to buy some additional components to do this correctly. Maybe just sell some of your current gear and use the money elsewhere or put it in your pocket?

George

ctviggen · « **Reply #5 on:** 6 May 2004, 06:10 pm »

George,

Well, I definitely don't want to start down the path of active crossovers or anything like that. There's a ton of stuff I'd rather have before I go that route. I just have these two extra channels of amplification that I'm trying to figure out what to do with, and people keep saying how power hungry the RM40s are. I was originally going to do a 7-channel setup, but I really don't have a good room (without ripping out walls to run cable and mount two channels) for this. I think I will bi-amp the RM30C just to see what (if anything) happens, although it seems a waste to biamp a speaker primarily used for voices.

John Casler · « **Reply #6 on:** 6 May 2004, 09:32 pm »

Quote from: ctviggen

George,

Well, I definitely don't want to start down the path of active crossovers or anything like that. There's a ton of stuff I'd rather have before I go that route. I just have these two extra channels of amplification that I'm trying to figure out what to do with, and people keep saying how power hungry the RM40s are. I was originally going to do a 7-channel setup, but I really don't have a good room (without ripping out walls to run cable and mount two channels) for this. I think I will bi-amp th ...

Hi Bob,

You are correct the RM40s "DO" Love a lot of power. I had 600wpc pushing mine and they loved every watt of it.

I agree that you should try "single amping" first, but if you are set on Bi-Amping, do so in either a vertical or horizontal Bi-amp configuration, using either 4 of the exact same monoblocs (like the AmpZillas, or JR's) or dual stereo amps that are "exactly" the same.

In this way, you don't have to worry about any gain/sensitivity differences, and all the connections are simple.

If using dual "stereo" amps, use the "vertical" configuration, since this will more evenly balance power supply drain (usually bass) over two power supplies.

I am considering that very type of set up using two 3 channel amps (600wpc x 3) and biamping my next pair of RM40's, and using the 3rd channel to power "stereo" LARGERS. (1800 watts per bank!!

)

ctviggen · « **Reply #7 on:** 7 May 2004, 12:29 pm »

Thanks, John. I doubt I'll go the biamp route, then, as I could biamp using four channels of my Lexicon/Bryston, but I think that the JR is a much sweeter sounding amp. I don't think I could buy another JR, as it was $7,500 MSRP (although I didn't pay that, and now the #10 is a "classic" amp and is no longer being made). That'd be 15,000 MSRP in amplification just for the RM40s. Plus, that'd be somewhere in the neighborhood of 180 pounds in amplification (I already have around 120 pounds), and I don't think my rack could take that! So, I'll have to hope my JR can hack driving the RM40s. (One thing I will do is wire in a 15-amp circuit just for the amplifiers. That should give them some more power.)

zybar · « **Reply #8 on:** 7 May 2004, 01:37 pm »

Bob,

At some point I can come up and bring my 201's (since they are so small).

Also, if you are going to put in a dedicated line, make it 20 amp. Not really more expensive, but gives you more flexibility.

George

ctviggen · « **Reply #9 on:** 7 May 2004, 02:23 pm »

Thanks, George, and you're right about the 20 amp vice 15 amp. I have one breaker opening left in my box, and I'd only have to go 10 feet or less to wire that in. Maybe I could lug my JR to where you are -- I'd like to compare the new JRs to the old JRs. The nice thing about my #10 is that even though it weighs 60+ pounds, the power supply is separate from the amplifier portion, so you can carry them separately. Also, the prices are really diving for the #10 -- on Audiogon, a guy is selling one for less than half price.

PLMONROE · « **Reply #10 on:** 7 May 2004, 03:51 pm »

John, for the internal modification to actively bi-amp the RM-40 is the lead for the large coil cut to remove it from the circut or is it just shunted out ? Thanks

Paul

John Casler · « **Reply #11 on:** 9 May 2004, 09:26 pm »

Quote from: PLMONROE

John, for the internal modification to actively bi-amp the RM-40 is the lead for the large coil cut to remove it from the circut or is it just shunted out ? Thanks

Paul

Hi Paul,

I assume by "actively biamp" you are also asking about bypassing the passive crossover network?

If so, that is a question for Big B.

B, are you there?

PLMONROE · « **Reply #12 on:** 11 May 2004, 04:30 pm »

Sorry I wsn't more clear in my earlier post. I am speaking of biamping using a Marchand 2 way electronic crossover (crossing over at 166hz) and feeding one amplified output to the RM-40s cones and the other to the ribbons.

Paul

Ric Schultz · « **Reply #13 on:** 11 May 2004, 05:43 pm »

Yes, you would remove the coil completely on the woofer and hook up the woofer amp directly to the woofer and also remove the coupling cap in series and coil to ground on the midrange ribbons and run the upper amp directly to the ribbons.....be careful with DC! Without a coupling cap on the midranges any DC that comes from the upper amp could damage the ribbons. Brian will probably say nay. The tweeters will still have to have the pot, cap and coil on them running from the upper amp.

This is assuming that the crossover has a volume control so you don't need the speakers pot on the midrange.

Good Luck! Bi-amping done right is killer!