[Russtafarian]

Just wanted to pass on my experience biamping the RM30’s with an analog electronic crossover, rather than the digital Behringer that’s used in the SDE setups.

Up until now I’ve been driving the RM30s full-range with a pair of 50 watt Quicksilver monoblock tube amps.  Midrange and highs sounded great, and the overall coherency of the speakers was outstanding.  But low bass was non-existent and midbass was anemic and soggy.  I knew the SDE approach would help this but I’m just not willing to digitize the sound, especially the mids and highs.

A few weeks ago I got hold of a Carvin electronic crossover that had been used then retired from my church’s sound system.  It’s an op-amp based analog unit with 24db Linkwitz-Reilly slopes.  I’m using it on my stereo dipole subs and the RM30 woofers only.  Mid/tweeter drivers are driven directly by tube amps using the speaker’s passive crossover.

Subs are crossed over to the RM30 woofers at 50 Hz, which is the lowest point on the low-mid crossover knob.  The RM30 woofers are crossed over at 600 Hz, which is the lowest point on the mid-high crossover knob.  Amps for the subs and RM30 woofers are DIY Hypex class D.

The one change I made to the speakers was to bypass the bass coil.  This involved removing the side woofer to access the crossover.  The bass coil leads were disconnected (desoldered) from the negative binding post and the black woofer speaker wire.  The black woofer speaker wire was then connected to the negative binding post.  Pretty simple and easy to restore if/when necessary.

Once I connected everything and fired up the system, setting levels was easy.  I turned the midrange and tweeter L-pads all the way open, put on a female vocal track (Stacy Kent – Ice Hotel), and turned up the woofer level until the vocal started to sound slightly tubby then backed it off a bit.  Tweeter and sub levels were then readjusted to taste.

All I can say is WOW!  This opens up the sound of these speakers like nothing else I’ve tried.  I’m now getting incredible bass dynamics, articulation and slam.  But just as important, the overall coherency of the speakers is still there.  At first I thought the 600 Hz lowpass would be way too high for the woofers, considering the passive crossover point is 280 Hz.  But it sounds really good and fills in more of the gap between the woofers and the mid panels. 

So here we have an analog biamping solution for the RM30 that delivers many of the benefits of the SDE approach without digitizing the signal.  And the cost is pretty reasonable.  The Carvin crossover, or one like it, can be had for between $200 and $300 at any pro sound/MI shop.  Add a decent solid state amp and you’re in business. 

Now it’s time to pop the hood on the crossover and plug in some better op-amps…

Russ

[John Casler]

Hi Russ,

Sounds like you're having fun.

Brian also offers an "Analog" Outboard Crossover.  It is known as the OXO (for Outboard X-Over) and is all Analog/Passive.

In fact, very few order the "internal crossover" any longer although it is still available.

[Russtafarian]

Yup, I'm having fun.

The BIG difference-maker here is bypassing the bass coil and replacing it with an electronic low pass filter.  This really uncorks the low end of the speaker. 

I recommend this biamp mod to any RM30 owner who wants to maximize the performance of the speaker.  And using an analog electronic crossover means you don't have to digitize to do it.

[Brian Cheney]

In recent years I have become a big fan of active crossovers and biamping while acknowledging that many users don't like the complexity and expense involved.

On the analog side we offer the 1000W amp modded with a 280Hz 24dB lowpass filter, which takes the bass coil out of the circuit.  You have heard the difference that makes.

On the digital side I really like the flexibility of the modded Behringer DCX 2496, since it adds 8 bands of parametric EQ to the two way low and high pass filters of its electronic crossover.  This permits us to smooth over a 2.5dB "presence peak" designed into the mid panel, compensate for the treble rolloff of the CDWG, and have bands left over for room EQ.  The improvements are astounding and that's the way I play my system at home.

Mike Galusha's mods to the DCX, while expensive ($1600) give you a preamp with remote balance and level, state of the art analog inputs and outputs, and an entirely new ADC and DAC which all together sound wonderful.  It's then possible to hook up any digital source directly to the DCX and eliminate a preamp.

[simon wagstaff]

"Mike Galusha's mods to the DCX, while expensive ($1600) give you a preamp with remote balance and level, state of the art analog inputs and outputs, and an entirely new ADC and DAC which all together sound wonderful.  It's then possible to hook up any digital source directly to the DCX and eliminate a preamp.
"

Hmmm, if only he could include a fire wire input so that I could use my Pioneer DV79i as a source I would look at this very seriously!  A usb one would be useful as well.

[Brian Cheney]

Just ask Mike, he's on this board, or you can PM him.

[jonbee]

On the analog side we offer the 1000W amp modded with a 280Hz 24dB lowpass filter, which takes the bass coil out of the circuit.  You have heard the difference that makes.

I'm interested in looking at this further. I'm very happy with my front end, so I don't want to get involved in the deq right now, but I'd like to tighten up the bottom end of the RM30s. I assume this refers to the plate amps, so 2 would be necessary? The plate amps would feed the bass drivers of my RM30s, bypassing the passive xover totally and the main amp would run full range into the mid/tweeter xover sections? Will this really improve the tightness and impact of the 6.5s?
Cost?
Thanks,
John

[John Casler]

On the analog side we offer the 1000W amp modded with a 280Hz 24dB lowpass filter, which takes the bass coil out of the circuit.  You have heard the difference that makes.

I'm interested in looking at this further. I'm very happy with my front end, so I don't want to get involved in the deq right now, but I'd like to tighten up the bottom end of the RM30s. I assume this refers to the plate amps, so 2 would be necessary? The plate amps would feed the bass drivers of my RM30s, bypassing the passive xover totally and the main amp would run full range into the mid/tweeter xover sections? Will this really improve the tightness and impact of the 6.5s?
Cost?
Thanks,
John

Hi Jonbee,

What Brian is refereing to is the PBS.  This stands for "Powered Bass System".

It "is not" a plate amp in the RM30 as there is not enough real estate on that model to mount the plate version.

It is a modded Bass amp to accomadate the higher crossover point of the mains (280hz).

It is a component amp that can be rack mounted or placed close to the speaker depending on your system and set up.

The list price per pair modded to your speaker is $1198.

[Scottdazzle]

Roger Modjeski at Music Reference/RAM Labs custom made a 280Hz analog passive crossover with a gain control for me.  I inserted it between the preamp and the amps and it worked like a charm.  A low cost, high quality solution tailored specifically for VMPS RM30 speakers.

[woodsyi]

A few weeks ago I got hold of a Carvin electronic crossover that had been used then retired from my church’s sound system.  It’s an op-amp based analog unit with 24db Linkwitz-Reilly slopes.  I’m using it on my stereo dipole subs and the RM30 woofers only.  Mid/tweeter drivers are driven directly by tube amps using the speaker’s passive crossover.

Subs are crossed over to the RM30 woofers at 50 Hz, which is the lowest point on the low-mid crossover knob.  The RM30 woofers are crossed over at 600 Hz, which is the lowest point on the mid-high crossover knob.  Amps for the subs and RM30 woofers are DIY Hypex class D.

The one change I made to the speakers was to bypass the bass coil.  This involved removing the side woofer to access the crossover.  The bass coil leads were disconnected (desoldered) from the negative binding post and the black woofer speaker wire.  The black woofer speaker wire was then connected to the negative binding post.  Pretty simple and easy to restore if/when necessary.

Once I connected everything and fired up the system, setting levels was easy.  I turned the midrange and tweeter L-pads all the way open, put on a female vocal track (Stacy Kent – Ice Hotel), and turned up the woofer level until the vocal started to sound slightly tubby then backed it off a bit.  Tweeter and sub levels were then readjusted to taste.

All I can say is WOW!  This opens up the sound of these speakers like nothing else I’ve tried.  I’m now getting incredible bass dynamics, articulation and slam.  But just as important, the overall coherency of the speakers is still there.  At first I thought the 600 Hz lowpass would be way too high for the woofers, considering the passive crossover point is 280 Hz.  But it sounds really good and fills in more of the gap between the woofers and the mid panels. 
Russ

You are going to get a little peaky in the 280Hz to 600 Hz since your Neo's and woofers are both putting out here.  With some music it's nice but more bassy music will get boomy.  I use switching amps on the woofers too -- they are excellent at this.  Have fun trying different pole points. 

Brian, what slope is the passive high pass on the Neos?

[Russtafarian]

You are going to get a little peaky in the 280Hz to 600 Hz since your Neo's and woofers are both putting out here. 

That's what I would have expected.  Turns out the room has a FR dip in that range so the overlap actually helps.  I'm still playing with pole positions and levels.  Initial results are quite pleasing but still room for fine-tuning.

[Brian Cheney]

The lowpass to the bass is at 6dB/oct, highpass to the mids at 12 dB/oct, a consequence of the series first order network.

With the SDE the lowpass is at 24dB/oct and the highpass is 12 dB.