[doug s.]

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

hi john,

i have been following this thread, and i am confused - if the rm30's x-o is outboard, then if disconnected, the 280 hi-pass is also disconnected, no?  only the x-over between midrange and tweeter (~7khz?)  should still reside within the speaker?

thanks,

doug s.

[Russtafarian]

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.

That's what I did including removing the midpanel L-pad.  With an active crossover, the woofers can be turned up to balance with the mid/highs, rather than mid/highs being turned down with L-pads to balance to the woofer.  The added bonus here is increased speaker sensitivity because the L-pad isn't burning off half the power before it gets to the panels.

I did leave the tweeter L-pad in place so I can still control that level.  I also left the midrange LPF coil in because I didn't want to introduce any potential HF nasties from the midpanels.  Maybe some day I'll disconnect it and see if that helps/hurts the sound.

Russ

[John Casler]

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

hi john,

i have been following this thread, and i am confused - if the rm30's x-o is outboard, then if disconnected, the 280 hi-pass is also disconnected, no?  only the x-over between midrange and tweeter (~7khz?)  should still reside within the speaker?

thanks,

doug s.

Hi Doug,

You are correct.

But I think the OP had suggested that he was going to use the Bryston 10B "directly" to the bass binding posts of the speaker (by-passing the VMPS OXO in the bass), but employ the VMPS OXO on the highs and mids.

I could have mis-read these intentions, but I think that was what he said.

<<<<<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>>>>

[BobRex]

Umm, actually Doug is wrong.  If you have the OXO, then all of the crossover parts are in the outboard unit.  The 7K tweeter crossover is also in the OXO box; connecting directly to the speaker's tweeter binding posts is a direct connection to the tweeter, without any filtering.

At least that's how it is in my boxes.

[Scottdazzle]

I have the crossovers inside the cabinets.  I want to be sure not to fry a tweeter  by taking out something (a filter cap?) that is necessary to protect it from midrange frequencies.  I would set the crossover at a good frequency (say 300Hz or 500Hz) to separate the woofer frequencies from the panels and ribbon.  I would rely on something passive between the mid and the tweeter to protect ribbon tweeter.   

[doug s.]

i would get specific instructions from brian about how to completely disconnect the low-mid x-over, while still keeping the mid-hi x-over intact, for proper bi-amping w/an outboard active x-over.

doug s.

[John Casler]

i would get specific instructions from brian about how to completely disconnect the low-mid x-over, while still keeping the mid-hi x-over intact, for proper bi-amping w/an outboard active x-over.

doug s.

Brian makes what we call a "digilog" bridge for that purpose.

Have not offered it separately but it is included in a D-OXO purchase.

It blends the FST/Neopanel in a way that B likes, so you can "biamp" using the D-OXO rather than "triamp".

[Scottdazzle]

Doug, good advice.
John, I'm not interested in upgrading a passive crossover.  If I change at all, it would be to an active crossover between the preamp and power amps. I hope Big B joins this discussion.

[John Casler]

Doug, good advice.
John, I'm not interested in upgrading a passive crossover.  If I change at all, it would be to an active crossover between the preamp and power amps. I hope Big B joins this discussion.

Hi Scott,

Maybe I should have been more "encouraging" for you to have gone with the OXO's back when you got your 30's.  Then it would be simply a matter of adding the D-OXO and your amps.

B, is busy getting ready to unveil the SURPRISE I mentioned earlier in the VEGAS thread.

He is a "workaholic"!! and until after the show he may be a little scarce, but who knows he may put in a quick appearance.

I should mention a quick caveat to all who are thinking of tweaking. 

Remember B has built these speakers over the span of a few years and when he comes up with an improvment, it is automatically in the NEXT speaker he builds.

Like Russ's RM30s which he has worked on were an "early" pair and may be different slightly than yours. 

I generally encourage tweaking away and having fun, but make every effort to ascertain that the advice you are getting comes from someone with knowledge and skills, and is talking about a speaker that is similar to yours overall, so the adjustments make sense.

Brian, doesn't always follow the "speaker designers" rule book.  He has his own

[Scottdazzle]

I want to resurrect this thread because my big questions are still unanswered.  How exactly does the internal crossover need to be bypassed or modified to accommodate electronic biamping (with a Marchand active crossover)?  This will take some work and I want to get it right the first time.

I think there must be a high pass cap in parallel between the mid panels and the ribbon tweeter that is necessary to protect the ribbon.  Is everything else safe to bypass? 

Is there any crossover part between the 6.5" midwoofers and the 10" that needs attention?

Is 300 Hz with a 24db/octave slope advisable?  The passive crossover is 6db/octave at 280 hz (I think).    Although that slope seems inadequate to protect the mid panels from dangerous low frequencies.

If anyone knows any of the answers, please chime in. Thanks!

Scott
 

[John Casler]

I want to resurrect this thread because my big questions are still unanswered.  How exactly does the internal crossover need to be bypassed or modified to accommodate electronic biamping (with a Marchand active crossover)?  This will take some work and I want to get it right the first time.

I think there must be a high pass cap in parallel between the mid panels and the ribbon tweeter that is necessary to protect the ribbon.  Is everything else safe to bypass? 

Is there any crossover part between the 6.5" midwoofers and the 10" that needs attention?

Is 300 Hz with a 24db/octave slope advisable?  The passive crossover is 6db/octave at 280 hz (I think).    Although that slope seems inadequate to protect the mid panels from dangerous low frequencies.

If anyone knows any of the answers, please chime in. Thanks!

Scott

Hi Scott,

Only Brian can properly answer your questions, but with the advent of the new RM50 and its XO options which are:

Passive Analog OXO

Active D-OXO

We now have an ACTIVE Analog OXO based on the Marchand XO ($1500) built specifically to fulfill the needs of the VMPS designs. (this has recently been added to the Price List here on AC under the RM-50, but can be employed on any new VMPS model.

However in my communications with B, he said the stock XO will not do what is needed due to the staggered poles, and other considerations, and the crossover we have built will allow the needed elements.  Now that does not mean that you couldn't use virtually "any" crossover and any configuration you might want to try, but the actual result will not be what Brian achieves which is part of his artistry.  His combination of specific staggered poles, 1st order, minimum phasing, and other such elements make it difficult to duplicate using conventional methods and wisdom.

Brian may answer further but the typical DIY'er might not get it right (or as intended) via the conventional XO route. 

And that is not intended to dissuade your direction, (which could end up totally satisfactory) but to offer information that might affect your approach.  Also, I'm not sure how much B, will disclose of his "bag of tricks" that make up the VMPS sound.

Seems to me he said that it takes a 4-way SS XO to do the job, but I may have misread (or remebered)

[Scottdazzle]

John,

Thanks for your response.  The Marchand uses a 24db/octave slope so it should not introduce any phase problems... unless Brian has skillfully used some combination of 6db and 12db crossovers which are combined to maintain phase.  If that's the case, I'll drop this idea and stick to what I have. 

My thought was that an active XO would be superior to the internal passive XO.  I love these speakers and only want to get them to their ultimate performance without introducing a digital XO.  I've become a bit of a troglodyte with regard to digital.

Scott

[John Casler]

John,

Thanks for your response.  The Marchand uses a 24db/octave slope so it should not introduce any phase problems... unless Brian has skillfully used some combination of 6db and 12db crossovers which are combined to maintain phase.  If that's the case, I'll drop this idea and stick to what I have. 

My thought was that an active XO would be superior to the internal passive XO.  I love these speakers and only want to get them to their ultimate performance without introducing a digital XO.  I've become a bit of a troglodyte with regard to digital.

Scott

Hi Scott,

And my intention was not to dampen you project, but to offer direction.

Recently with the introduction of the RM50 we have expanded our XO offerings:

1) Analog Passive Internal XO
2) Analog Passive External (OXO)
3) Analog ACTIVE External (A-OXO)
4) Digital ACTIVE External (D-OXO)

and the D-OXO has 3 optional upgrade levels in the works.

I am not aware of any other speaker producer that has such a broad level of XO options.

[BobRex]

I want to resurrect this thread because my big questions are still unanswered.  How exactly does the internal crossover need to be bypassed or modified to accommodate electronic biamping (with a Marchand active crossover)?  This will take some work and I want to get it right the first time.

I think there must be a high pass cap in parallel between the mid panels and the ribbon tweeter that is necessary to protect the ribbon.  Is everything else safe to bypass? 

Is there any crossover part between the 6.5" midwoofers and the 10" that needs attention?

Is 300 Hz with a 24db/octave slope advisable?  The passive crossover is 6db/octave at 280 hz (I think).    Although that slope seems inadequate to protect the mid panels from dangerous low frequencies.

If anyone knows any of the answers, please chime in. Thanks!

Scott

There's a litle more to it than you think, Scott.

Let's look at the midrange tweeter interface first.  The midrange panels have a high pass XO to attenuate bass signals (that's a 6dB filter at 280 Hz.  Notice I didn't say "block the bass",  a 6dB filter just attenuates the bass signal - the panel is still working at 35 Hz, it's just going to be down by 18dB.) That filter will probably be a couple of caps parallelled together to give the proper value.  The mid panels have an additional low pass filter to attenuate the highs above 7K.  That filter may be a coil.  (To be honest, I haven't pulled my OXOs apart to determine what makes up each pole, I'm just going by traditional first order theory.)  Now you have the low pass filter on the tweeter.  That should also be a cap (or a couple of caps parallelled.)  You would probably want to pull out the panel's high pass filter and leave the low pass and tweeter high pass alone.

As far as what's between the midwoofers and the 10", if I get time this afternoon, I'll pull the 10" and take a look.  My gut says that there is probably something there, but i'd bet it's for level matching.

Three hundred Hertz with 24dB might work, but I'm not convinced that there won't be a response hole.  Brian used 6db slopes on the panels for a reason, so I'm not sure what you will gain.

Why do you think that the panels need additional protection from "dangerous" low frequencies?  The panels are pretty rugged; I haven't heard of many blowing up (John? Brian?)

It seems to me that you don't have a firm grasp on filter theory.  What exactly do you hope to gain by gutting the speaker?  Seriously, this isn't a cheap ass POS speaker, whatever you do, please make sure that you can restore everything back to normal.

[Scottdazzle]

Hi Scott,

And my intention was not to dampen you project, but to offer direction.

Recently with the introduction of the RM50 we have expanded our XO offerings:

1) Analog Passive Internal XO
2) Analog Passive External (OXO)
3) Analog ACTIVE External (A-OXO)
4) Digital ACTIVE External (D-OXO)

and the D-OXO has 3 optional upgrade levels in the works.

I am not aware of any other speaker producer that has such a broad level of XO options.

John,

If I go with 3) Analog ACTIVE External (A-OXO), there must be some disabling of the internal passive XO required.  All my questions would still apply.  Brian, are you out there?   

Scott

[John Casler]

John,

If I go with 3) Analog ACTIVE External (A-OXO), there must be some disabling of the internal passive XO required.  All my questions would still apply.  Brian, are you out there?   

Scott

You are correct.  ALL of the drivers would be wired directly to three pair of binding posts.

Brian may have a "protective" device in the tweeter line. (as a precaution) for those who wish to "tri-amp".

For those who Biamp, the device will be included in the digilog bridge of the tweeter and panels.

[John Casler]

Why do you think that the panels need additional protection from "dangerous" low frequencies?  The panels are pretty rugged; I haven't heard of many blowing up (John? Brian?)

Hi Bob,

You are correct, the panels are amazingly rugged and robust.  Although B, has occasionally made reference to one failing, in all my years I have only had them fail from the "manufacturers defect" that didn't get fully repaired, or was damaged by rough handling which lossened the connection causing a buzzing.

[PLMONROE]

Brian may have a "protective" device in the tweeter line. (as a precaution) for those who wish to "tri-amp".

If you drive the tweeter directly from your amp be sure to put a big honking capacitor in the red lead just to be safe . 

Paul

[DFaulds]

If you drive the tweeter directly from your amp be sure to put a big honking capacitor in the red lead just to be safe . 

Paul

Actually, you would want a smaller value cap in series with the tweeter, unless you were referring to the voltage rating of the cap.  Large mfd caps create lower frequency crossover points and would provide very little protection for the tweeter.

[PLMONROE]

  All I know is Big B said that if I put a 10.0 uF in series with the tweeter it would work fine. So I installed a pair of  800v Jantzen Audio Silver Z caps. No degridation of sound and no fried tweeters. 

Paul