[dabber]

I want to biamp my RM30M's using a Bryston electronic crossover. Would someone recommend the the crossover frequencies and slopes. Thanks, David

[Pez]

If I were you I would experiment a bit with the crossover. The factory crossover is at or around 300 hz using a 1st order crossover. But now that you have an active crossover the sky is the limit. Obviously you don't want to go much lower than 300hz, but I for instance use my active cross on my RM40s at 500 hz with a 2nd order linkwitz riley. That's the beauty of an active crossover. You can tweek to your hearts content. 

[BobRex]

The internal crossover to the woofers is at 280Hz.  The high-pass side is 6dB, I think the low-pass is too.  I use the PBS, so I've got the woofer plate amp at 280Hz, 12 dB for the low-pass and then the 6dB for the ribbons. 

I would suggest starting there or maybe overlapping a little, say 400Hz / 12dB for the woofers and 180Hz / 6dB for the ribbons if you don't plan on removing the internal xovers.

[Russtafarian]

Biamping RM30s?  Go for it!  You will definitely want to play with crossover frequency and driver levels.  The beauty of this arrangement is that you can tune the speaker to sound the way you like it in your room. 

I have the electronic crossover on my RM30s set at 600 Hz (4th order L-R) from woofers to mid-tweeters.  I use well-recorded female vocals to set frequency and driver levels to get just the right amount of lower midrange presence in the voice without any unnatural midbass tubbyness.

The next step to transparency is to remove the internal woofer low pass coil and midrange high pass cap, coil, and L-pad*.  This really uncorks the bass and unleashes the startling resolution of those midpanels.  Good luck!

Russ

*If you decide to do this, leave the tweeter crossover intact.  The ribbon is too delicate to direct connect to an amp.

[BobRex]

I have the electronic crossover on my RM30s set at 600 Hz (4th order L-R) from woofers to mid-tweeters.  I use well-recorded female vocals to set frequency and driver levels to get just the right amount of lower midrange presence in the voice without any unnatural midbass tubbyness.

The next step to transparency is to remove the internal woofer low pass coil and midrange high pass cap, coil, and L-pad*.  This really uncorks the bass and unleashes the startling resolution of those midpanels.  Good luck!


*If you decide to do this, leave the tweeter crossover intact.  The ribbon is too delicate to direct connect to an amp.

Actually, removing the internal bass and mid crossover isn't the next step, it's the FIRST step.  It's not a case of just "adding" transparency, it's also necessary to prevent response holes.  Ross, if you hadn't removed the internal crossover, you would have had a huge hole between 280 and 600 Hz. 

You can drive the tweeter directly, but that would be tri-amping, not bi-amping, and would require a different external crossover (I don't believe the Bryston does tri) and additional amps.  I've got a hunch something like the Transcendent SEOTL would sound fantastic on the tweeter ribbon.

[Pez]

Bobrex forgot one very important step in triamping for a tweeter, you need to have a non polarized capacitor on the positive terminal of the driver coming from the positive terminal of the amp. Without it you are pretty much gauranteed to blow your tweeter sooner or later with even a small DC spike.

[John Casler]

I want to biamp my RM30M's using a Bryston electronic crossover. Would someone recommend the the crossover frequencies and slopes. Thanks, David

Hi David,

As mentioned by others, implementing an external active X-OVER "without" disengaging the internal passive XO's will have limited result.

This is especially true, since Brian already has optimized the actual analog utilization for most purposes.

What you will end up with by adding an active "over" the existing network will amount to levels of prefiltering, which can be tricky and doubtful.

I am a BRYSTON Dealer but have not had any clients interested in the X-overs yet.  You didn't mention which BRYSTON you were using, but I think they are mostly 2 way units meaning you could select a single hinge frequency like 300hz and then adjusts gain and slopes above and below.

But again, you might find the "pre-filtering" over an existing network less than satisfactory.

I think to do a 3way you may need TWO crossover units.

Anyone feel free to correct me if I am incorrect on that.

[Hipper]

Please forgive my ignorance here but wouldn't people wanting to actively bi-amp RM30Ms be better off investing in Brian's SDE set up?

http://www.audiocircle.com/index.php?topic=54554.0

[dabber]

The VMPS RM30M's I want to biamp have the external crossover with auri caps. I want to biamp directly from Bryston to the bass amp to the bass input of the speaker and from the Bryton to the high mid frequency amp then to high mid  frequency of the external crossover.  Thanks,
David

[John Casler]

The VMPS RM30M's I want to biamp have the external crossover with auri caps. I want to biamp directly from Bryston to the bass amp to the bass input of the speaker and from the Bryton to the high mid frequency amp then to high mid  frequency of the external crossover.  Thanks,
David

An OXO will certainly allow you to have an easier time of it since you don't have to perform speaker surgery.

In that config you will be "lowpass" filtering with the 10B, and if it is the 10B SUB you will have a choice of 250Hz or 300Hz (it is not a variable adjustment)

The highpass however will still be 'fixed" via the OXO at 280Hz and stock phase and slope.

Unless you already have the 10B, Hipper is correct that it is likely a better option to use Brian's D-OXO, where he has programmed "all" the interactive relationships between drivers.

And with the D-OXO you have the "flexibility/tweakability" of many more signal adjustments.

[BobRex]

Actually John, since the 10B does have turnover freqs. for low and high pass you could run the woofers beyond 300Hz (450, 700, 1K??) and let the panels run from there.  That may cause phasing problems, given that the mids will see 2 high pass polls, not to mention lobing issues with pushing the woofers too high.  To me, the 10B appears to be too limited in frequency selections to truly be as effective as the DEQX, but what the hell.

[Russtafarian]

Actually, removing the internal bass and mid crossover isn't the next step, it's the FIRST step. 

Good point. Adding an electronic crossover without bypassing the passive speaker crossover will create more problems than it would solve.

[John Casler]

Actually John, since the 10B does have turnover freqs. for low and high pass you could run the woofers beyond 300Hz (450, 700, 1K??) and let the panels run from there.  That may cause phasing problems, given that the mids will see 2 high pass polls, not to mention lobing issues with pushing the woofers too high.  To me, the 10B appears to be too limited in frequency selections to truly be as effective as the DEQX, but what the hell.

Hi Bob,

You are correct as I was ignoring the higher hinges as not useful (according to Pez however he likes 500Hz)

But in the end the D-OXO is still a more comfortable option for most uses.

[Pez]

500 hz works well for the 40s, but I question whether it will be consistent across the line. I have used everything from 266 hz to 600 hz. I find I get a flatter FR @ 500 hz. That said I don't exactly have an anechoic chamber and expensive test gear. 

I want to add that perhaps instead of a Bryston active cross perhaps David would be wise to look at more flexible and versatile options like a modded DCX. An active cross over does little to nothing to tune out in room anomalies and while I don't doubt the Bryston active is a great crossover, it is limited to being just that.

[Scottdazzle]

This is a very interesting thread and it has gotten me interested in bi-amping with an external XO.  Unfortunately I have zip electronics know-how.  I know that you need to remove the woofer low-pass coil and the high-pass crossover parts, but something must remain in place to protect the tweeter from low frequencies.  The VMPS website provides this intimidating picture of a crossover.  My question is which of the parts shown must be retained to protect the tweeter?  A nice pictorial guide would prevent audiophools like me from removing the heart instead of the spleen!

[Pez]

You don't have to retain any of the parts. Take the crossover out completely and install it in your nearest waste bin. 

Seriously though none of it stays. You can try to use one of the caps as a tweeter protect and even midrange protect if you want to be really careful. Or you can buy a bigger cap that would be better suited. As long as it's non-polarized you should be fine.

[Russtafarian]

Here's my crossover explanation attempt based on the picture below.  If anyone recognizes that I've messed up here, please correct me.

The components in the bottom left part of the picture are the high pass filter for the tweeter.  You have a skinny cylindrical coil and three small caps.  The wiring should trace back to the smaller L-pad/level control and up into cabinet to the tweeter.  The wire colors are green and blue.  For reference I'll call this Group A.

In the very top right of the picture you can see part of another coil.  This coil is the low pass filter for the midpanels.  This makes it part of the midpanel/tweeter crossover so I'll include it in Group A.

The components in the middle are the high pass filter for the midpanels.  This includes the big black and white cap with one yellow and three brown caps piggy-backed on it and the 3.6 labeled coil.  The wiring should trace back to the bigger L-pad/level control.  The wire colors are red and red w/ green stripe.  This will be Group B.

Not pictured is a big, long coil that is the low pass filter for the woofers.  It's easy to locate because of its size and it being wired in line with the woofers.  Even though it's just one component it will be Group C.

The parts you remove will depend on how much of the crossover you want to control externally. 

For full external crossover bi-amping, you can leave Group A intact and remove Groups B and C.  The caution here is that the midpanels now have no protection from bass frequencies and could be overloaded if fed a full range signal from an amp.

Another option is to partially biamp by removing the woofer coil (Group C) and controlling the woofer's lowpass filter with an electronic crossover and leaving Groups A and B in place and feeding it a full range signal from an amp. 

I started by removing the woofer coil (Group C) and was impressed with the increased bass slam and control.  When I took the next step and removed Group B, I was absolutely blown away at the increased speed, resolution and transparency of the midpanels.  While I had the speakers torn apart I dynamatted the interior which was a huge PITA due to the narrow cabinet but well worth the effort.

Russ

[BobRex]

Pez, I'm not so sure you really need the DC blocking cap on the tweeter.  Ribbon tweeters are transformer coupled, so that will block any DC from ever reaching the foil.  Seems to me that adding the cap is just a belt and suspenders thing.  Now the Neos are a different story.

[Pez]

I've got a blown FST tweeter that says otherwise. Then again it was the previous owner that blew it. He told me it was because he did not have a coupling cap in line, but who knows for sure.

[Scottdazzle]

Russ, Pez, and Bob,

Thanks for the lessons.  Tell me if this makes sense.  I remove everything except the high pass filter for the ribbon tweeter.  I guess this is the 6.9kHz crossover between the mid panels and the tweeter.

Scott