Actively biamp the RM-30 or not?

pugs · « **on:** 8 Jun 2004, 06:16 pm »

I'm getting ready to order my RM-30s, but was wondering if I should get them with the 10" crossover bypassed, and actively biamp.

I have bass issues in my room. the right speaker has a big (10-15dB) peak at 40Hz and a big (10-15dB) dip at 55-60Hz. The left speaker is pretty flat. I've only had rear ported designs (NHT 2.5i and Odyssey Lorelei) so I'm not really sure how the RM-30 will respond in my room. I'm not sure if adjusting the putty on the PRs and room placement can lessen the problem.

I don't know if it's a good idea to bypass the passive crossover to the 10" woofers or not. I could then actively biamp and use a parametric EQ. Is that just getting too complex for my own good. A Parts Express amp has been suggested, but I also have a NHT SA-3 sub amp.

I would like to know before I order so I can get everything done at the factory.

Has anyone done this? All comments and opinions would be appreciated.

Jon L · « **Reply #1 on:** 8 Jun 2004, 08:53 pm »

Quote from: pugs

I'm getting ready to order my RM-30s, but was wondering if I should get them with the 10" crossover bypassed, and actively biamp.

I have bass issues in my room. the right speaker has a big (10-15dB) peak at 40Hz and a big (10-15dB) dip at 55-60Hz. The left speaker is pretty flat. I've only had rear ported designs (NHT 2.5i and Odyssey Lorelei) so I'm not really sure how the RM-30 will respond in my room. I'm not sure if adjusting the putty on the PRs and room placement can lessen the problem.

I ...

How much discount would you get if you order the RM30 without ANY passive crossover? I can see no conceivable reason you would want to just bypass the woofer's x-over. If you are going to actively biamp, you should bypass the whole x-over. Digital x-over with auto-eq via mic would be preferable with your room nodes.

Use the saved money and get a nice active x-over, digital or analogue. As long as the active is flexible and adjustable for x-over point, slope, you can experiment to find the optimal settings, possibly different but better than passive x-over point/slopes. For example, you might be able to set a lower x-over point for woofer b/c you can use a steeper active slope, say >24dB/octave..

jgubman · « **Reply #2 on:** 8 Jun 2004, 11:38 pm »

Does the 10" driver share a binding post w/ the 6.5" drivers?

RGordonpf · « **Reply #3 on:** 8 Jun 2004, 11:46 pm »

An alternative to biamping the RM30s is to add a subwoofer. I have a pair of RM30s and a VMPS Large subwoofer. The RM30s are driven full range by SET tube amps. The signal to the subwoofer goes thru an external crossover and then to solid state monoblocks. This arrangement gives me an additional octave at the bottom (down to 17Hz) and incredible bass dynamics and slam. By being able to change the location of the subwoofer I was able to smooth out some of the peaks and valleys in the bass frequency response. YMMV.

Rory B. · « **Reply #4 on:** 9 Jun 2004, 01:20 am »

I'd be worried about putting too much more power to the Megawoofer than the 6.5" midbasses are getting. That would cause the midbasses to overexcursion, I think. The voice coil could begin to jump the gap and then the midbass would be all muddy for that period of time while the coil is out of the magnetic gap. For the best results, I'd recommend the RM-30C and a separate subwoofer, even if it is only a New Original sub. This sort of question leads me to wonder why VMPS stopped making the Smaller Subwoofer (which I plan to build in kit form for a friend of mine). A Smaller Subwoofer or a pair of them with Megawoofer would be a great match for the RM-30s, I would expect.

James Romeyn · « **Reply #5 on:** 9 Jun 2004, 02:12 am »

Replies inserted in italics.

Quote from:

I have bass issues in my room. the right speaker has a big (10-15dB) peak at 40Hz and a big (10-15dB) dip at 55-60Hz. The left speaker is pretty flat.

It appears one channel of parametric EQ with 2 bands would solve the above described modes.

I'm not sure if adjusting the putty on the PRs and room placement can lessen the problem...

It will help, definitely. Probably you will remove less putty compared vs. if no bass mode problem existed.

I can see no conceivable reason you would want to just bypass the woofer's x-over.

Here are some: VMPS discourages bypassing their OEM high pass XO hinges. The OEM passive HP XO has a tolerance of 1/2000th of 1%. All known commercial active crossovers have exponentially lower tolerance, probably above 5%. Tighter tolerance = less variation of the high pass crossover frequency between speakers.

Does the 10" driver share a binding post w/ the 6.5" drivers?

In the standard wiring schematic, yes.

If you are going to actively biamp, you should bypass the whole x-over. Digital x-over with auto-eq via mic would be preferable with your room nodes.

With all due respect, IMO, the HP XO's are unrelated to the stated room mode problem.

RGordonpf · « **Reply #6 on:** 9 Jun 2004, 03:37 am »

Quote from: Rory B.

"For the best results, I'd recommend the RM-30C and a separate subwoofer, even if it is only a New Original sub."

I bought the RM30Ms, rather than the RM30Cs, and the Large subwoofer with megawoofers, rather than any of the smaller subwoofers, including the 215 demoed with the RM30s at CES 2004. This was done after consultation with Big B. With the RM30Ms versus the RM30Cs you can crossover to the sub at a lower frequency which makes blending the sub with the RM30s a lot easier. Seamlessly blending a sub with the main speakers is always a problem. I have struggled with it before and always gave up in despair. With the RM30Ms and Large sub and an active crossover with variable volume and variable hinge point, the sub and RM30Ms blended seamlessly after only a little fiddling with the hinge point and volume.

With regards to the sub, bigger is better. Big B recommended two Large subs with the RM30Ms. My room is not huge and I don't play music all that loud, so one Large sub set up for stereo made sense for me. YMMV

I do drive the Large with two 400w mono block solid state amps. If you want to headbang at 110dB then two Large subs with megawoofers is the way to go. If you only listen to music at concert hall levels (90-95dB) and have a small or medium sized room, one Large should be adequate. I initially tried the Large bridged to mono with only one amp. Using the Large as a stereo unit with two monoblock amps yielded a small, but noticeable improvement.

Jon L · « **Reply #7 on:** 9 Jun 2004, 05:13 am »

"Here are some: VMPS discourages bypassing their OEM high pass XO hinges. The OEM passive HP XO has a tolerance of 1/2000th of 1%. All known commercial active crossovers have exponentially lower tolerance, probably above 5%. Tighter tolerance = less variation of the high pass crossover frequency between speakers."

Huh? I didn't know VMPS claims "1/2000th of 1%" tolerance for XO, but if it's demonstrable, why not make the claim on the website (I haven't seen this claim). I imagine it would be hard to actually demonstrate via normal instrumentation anywhere close to 1/2000th of 1%. Even if XO did measure so, the drivers (any driver in the world), not to mention the room, would measure distortions orders of magnitude higher. I also don't see where you come up with "5%" figure for "known commercial active crossovers." I've used active x-overs from Krell, Bryston, Purist Audio Design, KMF, and a few others, and while I can't recall their claimed tolerances, the better ones sure had great sonics.

"With all due respect, IMO, the HP XO's are unrelated to the stated room mode problem."

Huh again. Of course passive x-overs never CAUSE room nodes. Room nodes are caused by the room/speaker interface. On the same token, room nodes will never be corrected by a passive x-over. An active, digital x-over, with room eq has any chance of correcting room nodes, which was my point.

Not to seem like I'm attacking VMPS or anything. I was just relating my experiences with passive and active x-overs, and to me advantages of active outweighs disadvantages. Unless one is claiming a passive x-over with certain Unusual properties (notch filter, baffle step correction, etc) are necessary for a certain speaker, then that's understandable. But a well-implemented active will usually sound better than well-implemented passive in my book. Just my 2 cents.

pugs · « **Reply #8 on:** 9 Jun 2004, 02:18 pm »

I have a solution. I am going to get the RM30 with an added set of bass woofer binding posts. That set will bypass the crossover so I can actively biamp if I want. I'll also have the standard binding posts so I can drive the whole speaker with one amp. That way I'll always have the choice which way I want to run them.

Brian Cheney · « **Reply #9 on:** 9 Jun 2004, 03:25 pm »

No extra charge for the extra set of posts bypassing the bass xover.

Don't worry about overpowering the RM30 if you get the 6.5" Megawoofers ($380 sert of 4). Each has a 200W 1.5" 4layer voicecoil and a heavily bumped back plate so it can't bottom out under high power. Plus you have the 300W 10" Megawoofer standard. Plenty of power handling there!

dubravko · « **Reply #10 on:** 9 Jun 2004, 09:38 pm »

I've recently had a problem with my electronics, and as a result from it having some 5V DC at amplifiers line inputs. Sound of course started to be weird, but only when I sensed an ugly smell I realized something really bad is happening. Couple of seconds later I saw bass drivers standing firmly out as much as their mechanics allows them (that looks scary). All in all it took some 30 to 50 seconds from failure occurring until I switched off the amps. Bass drivers survived this horror without any damage. Imagine how much heat they received. I hope nobody will ever to go through this, but yes, power handling of 12" megawoofer is exceptional.

zybar · « **Reply #11 on:** 2 Aug 2004, 02:04 am »

Quote from: RGordonpf

An alternative to biamping the RM30s is to add a subwoofer. I have a pair of RM30s and a VMPS Large subwoofer. The RM30s are driven full range by SET tube amps. The signal to the subwoofer goes thru an external crossover and then to solid state monoblocks. This arrangement gives me an additional octave at the bottom (down to 17Hz) and incredible bass dynamics and slam. By being able to change the location of the subwoofer I was able to smooth out some of the peaks and valleys in the bass frequency response. YMMV.

Roger,

Which active crossover are you using? Also, did you bypass the passive crossover on the 30's?

George

RGordonpf · « **Reply #12 on:** 2 Aug 2004, 04:53 am »

George,

The active crossover that I am using started life as an AlphaSonics with variable hinge point and volume control. It was extensively modified several years ago. My preamp has two main outs. One goes to the external crossover to the sub monoblocks to the Large. The other main out goes directly to the SET monoblocks and then to the RM 30s. If you put an external crossover in front of the SET monoblocks/RM30s you can hear it. At least I have not found an external crossover yet that can't be heard, though I have not tried all of them. With my current arrangement, I no longer need to try. The crossover in the RM30 is quite good. Why not keep it?

Roger

zybar · « **Reply #13 on:** 2 Aug 2004, 01:52 pm »

Quote from: RGordonpf

George,

The active crossover that I am using started life as an AlphaSonics with variable hinge point and volume control. It was extensively modified several years ago. My preamp has two main outs. One goes to the external crossover to the sub monoblocks to the Large. The other main out goes directly to the SET monoblocks and then to the RM 30s. If you put an external crossover in front of the SET monoblocks/RM30s you can hear it. At least I have not found an external crossover yet that can't be he ...

Roger,

It is a little different with the RM 40's as most tube amps won't like the two 10" woofers, the below 4 ohm load, and the high current demands. Going active allows the tube amp to not see a full range signal.

Thanks for your reply.

George

JoshK · « **Reply #14 on:** 2 Aug 2004, 02:08 pm »

I have been kicking around the idea of going active biamping with the RM40's. My thoughts, were to find something like the late Welborne Reveille crossover that the low pass is active and the high pass is line level passive. If done right this should be quite an upgrade I'd imagine, especially with a good tube amp up top. In this setup I'd bypass the xo in the speakers (except for the tweeter/mid xo)

Rory B. · « **Reply #15 on:** 4 Aug 2004, 03:59 pm »

If you get the Larger subwoofer with the intention to set it up as stereo, always get it with the dual voice coils. Never send one channel to one woofer and the other channel to the other woofer. Not only will each woofer lend its own tonal character and transient response characteristics to the sound (bass sent to the subwoofer from each channel will sound different) but if there is a loud bass note sent to one woofer and nothing sent to the other woofer, then the bass loading provided by the cabinet and the passive radiator will be shot to heck and who knows what you'll hear. Make sure that each woofer is getting a piece of the final signal. If each voice coil is 4 ohms, then it is necessary in the case of the larger sub to have one of the voice coils on the megawoofer wired in series to one of the voice coils on the 15" and then the series pair then wired to the binding posts for one channel. Repeat this with the other channel. The result is that you'll hear the same bass from either channel of the Larger subwoofer.

Is there a photo of the 215 subwoofer anywhere? Isn't it just a Large sub with the other Megawoofer replaced with another 15"?

pjchappy · « **Reply #16 on:** 4 Aug 2004, 04:07 pm »

I believe the 215 is 1 15" w/ a PR.

p