[Q]

We're waiting here with bated breath for news on the sonic changes of the higher crossovers in the RM40s, et al.  Please post your impressions as soon as you can!   All I can think is that the changes must be so good, they cant get away from the sweetspot long enuf to get to the computer!    

Ready to order, check in hand, need input!!!

[Ric Schultz]

I could be wrong but I don't think there are any xover mods except a different coil value which controls the high frequency rolloff on the mids with units using the FST tweeter.  Brian said the mods were to the low pass filter on the midrange.  The low pass filter controls the high frequency roll-off.  Many people here think a low pass filter means the low frequency cutoff....no, that would be the high pass....ie the highs pass and the lows are cut-off.  Would be nice if Brian would chime in here and straighten this out.

[ekovalsky]

Based on the inductor swap, looks like it is the low pass on the midrange section that is affected, i.e. the 7khz filter like Ric says.  Changing the high pass (i.e. 166 > 200 hz) on the midrange section would involve swapping the six pack of capacitors, which are upstream to the target inductor coil.  There is a second inductor coil after the capacitors which is a shunt to ground, making the high pass filter a second order circuit.

From the RM-40 and RM/X pictures in the gallery, the midrange section looks topology looks like this:  (+) post > second order high pass (caps with inductor to ground) > potentiometer > first order low pass (inductor, target of swap) >  neo panels > (-) post = ground

Wonder how shifting the 7khz filter improves midbass performance  

[Q]

Well that information certainly doesnt follow what was purported to be a change to the 166Hz rolloff.  

WTF is up with that?
Q

[Brian Cheney]

The change was about a 1% shift in the midrange lowpass filter.  The mid highpass was never involved.

[zybar]

Ok.

Brian, what exactly does a 1% shift equate to?

It seems like a little more vocals are coming from the 10" drivers.  If I understand correctly, I am hearing this now b/c the midrange panel cuts off a little bit higher now?  The vocals (or anything else) were always there, but not as easily audible b/c the midrange was stronger at that point?

I need to do more listening, but the midbass doesn't really seemed to have changed a whole lot.  Of course I didn't have lots of fly time with the pre-crossover 40's...

I'll see what Horsehead says next time he comes up.

GW

[ekovalsky]

The change was about a 1% shift in the midrange lowpass filter.  The mid highpass was never involved.

The nomenclature is slightly confusing  

Midrange lowpass filter passes signal below ~ 7khz
Midrange highpass filter passes signal above ~ 166hz

There is no intuitive reason why the inductor swap would increase the level of vocals from the 10" woofer.  But, as we all know from the bass damping, there isn't always a logical explanation for what we hear.

[zybar]

Ok.

I obviously didn't understand that - thanks for setting me straight.  

So why did I even change the crossover?  I thought the crossover change was supposed to improve midbass?  

I am totally confused.

Brian, could you please state clearly what the crossover change was supposed to accomplish?  

GW

[Q]

Yeah, I was under the impression from a previous post that due to the improved sonic character from the RM30s using a higher crossover (as in 200Hz) from the woofs to the NEOs, that the change would be tried and (if successful) implemented in other VMPS models.

Perhaps here is another good reason to use an electronic active crossover.  One could fine tune that crossover point easily, thereby finding the best compromise.  

I'm wondering that since the woofs are crossed relatively low in the 40s, if baffle-step compensation is included with these.  Baffle step for this size of panel should be like 400Hz, I'm guessing.  SO, the baffle-step must be in line with the neo's.???  How would this affect an electronic crossover setup?

[PLMONROE]

I am using a Marachand crossover to actively biamp my RM-40's. As per Brians suggestion I tiried both 166 and 200 as crossover points. To me crossing over at 200 sounds far better.

Paul

[zybar]

Paul,

Couple of questions.

1.  Which Marchand model?

2.  What did you have to do to the speakers to use the active crossover?

3.  What amps are you using?

4.  What size is your room?

5.  What sounded better when you crossed over at 200?

Sorry, that was more than a couple.  

Look forward to hearing your reply.

GW

[Q]

"2. What did you have to do to the speakers to use the active crossover? "

Good question.  It would be meaningless to go active unless you bypass internal passive filter components.  This is why my earlier question about the baffle step compensation.  These passive baffle step components will have to be left in place, but will the total transfer function of the baffle step be affected by removing the passive crossover components.????  Aso, any equalization components or impedance matching components must be dealt with.

[PLMONROE]

Zybar -- Per Bryans recommendation I used a Marchand crossover. I initially used the XM-1 and it worked great.  However I have since switched to an Ashley because it has a mute button for each output. This greatly eases set up. My RM-40s have the TRT caps but not the FST tweeter (yet).  I made the internal modification to actively biamp (shorting the induction coil) when I did the TRT modification. My room is really smaller than I would like. It is 12.5 X 17 X9 feet and I listen nearfield with speakers along the short wall (a necessity since I also use this as my home theater room). The room has extensive acoustic treatment with bass traps at the four corners, absorption panels, and RPG diffusors. For music I  use a highly modified Shanling CDT-100 player, a highly modified MSB Gold Link Dac, Krell preamp, two VTL-250 monoblock amplifiers (triode mode) for the mids and highs and a Music Fidelity solid strate amplifier for the bass. Also I use a Vandersteen subwoofer with each RM-40.  Interconects are Monster 520i's and speaker cable is AudioQuest Momouth. Power is regulated my a Monster AVS-2000 and balanced using a  B-P Tech unit. As to the difference in sound with the crossover set at 200hz versus 166, thats a good question. It is not dramatic but mids have a bit more focus,  more bite and are a  bit richer.  Active biamping reduces intermodulation distortion  but apparently Brian did a great job on the innerds of the RM-40 because the difference between passive and active biamping is not that great. The fantastic improvement was the TRTs!

Paul

[zybar]

Paul,

Thanks for the response.

Sounds like for now I won't try an active crossover.

I am still debating whether I will try to biamp.  I tried briefly and was having some problems trying to get the bass to integrate with the rest of the music.  I know that I need a bass amp that is adjustable and might also need a way to adjust the midrange/treble amps as well.

GW

[PLMONROE]

In theory, active biamping which reduces intermodulation distortion should be a vast improvement. It is most likely less of an improvement with realy high quality components. I have not found it practical to pasively biamp using different amps as it is too difficult to get proper matching, so you are forced to vertically biamp using identical units. The beauty of active biamping is that matching things up, which you discovered to be a difficult thing to do becomes  a pieace of cake! Since I wanted to go with tubes on the top and solid state on the bottom, I had to  horizontally biamp. With an electronic crossover  using different types of amplifiers was no problem. So  active biamping was the obvious best choice for me.

[audiochef]

Paul,you should replace the receticles in your avs2000 with Leviton prograde 5252 .  I just did this mod to my hts3500 last week and the diferrence is night and day.
A friend of mine did it to his HTS5000 with same results. I'd go so far and say this is the most dramatic improvement of any mod I've had done.
And it all cost $25 dollars.
I've just been in awe, rediscovering all my CDs since then.
These speakers do deserve the purest signal you can offer.

[PLMONROE]

Thanks for tip. Every little bit helps and its nice to find a mod that doesn't wreck the budget for a change!

Paul

[John Casler]

We're waiting here with bated breath for news on the sonic changes of the higher crossovers in the RM40s, et al.  Please post your impressions as soon as you can!   All I can think is that the changes must be so good, they cant get away from the sweetspot long enuf to get to the computer!    

Ready to order, check in hand, need input!!!

Hi Q,

While Brian is the best person to totally answer your question, it is my understanding that the midrange highpass on the RM 30 is 280Hz, and the lowpass is 6940Hz.

While Brian did mention that some of this might "trickle up/down" to some of the other models, it will likely not be a "straight" swap all the way around, since each model is different having a different number of panels to handle the all important "mids/highs", and specific bass drivers or bass systems, to handle the low end.

And the RM40 is a different animal all together being a hybrid D'Appolito/Line Source combo, there is a fine art to balancing the frequencies to blend properly.

For example, crossing the upper woofer in the RM40 at 280hz probably wouldn't improve the qualities of the speaker.

Could it be "crossed" higher and still sound accurate?  Only B, can answer that.

I think the "retro" fit that Big B was talking about being available is the "low pass" winding mentioned above.

I'm sure if you talk to Brian, however, he will tell you that this small, subtle change, in this area, will sonically affect "all" the frequencies.

Now about that check......