I Want To Actively Bi Amp My RM 40's With An Electronic Crossover ?

ka7niq · « **on:** 6 Sep 2006, 01:34 am »

I have acquired a Rane electronic crossover, got it cheap. http://www.rane.com/ac22b.html
So, now it is time to do what i have always wanted to do to the RM 40's, Bi Amp them.
I do not mean to "Bi Amp" them passively, I mean to bypass the internal crossovers, and use an active electronic crossover before the amplifiers.

I really wish I had a 3 way electronic crossover, then I could do away with the internal passive crossover altogether, as good as it is.
Mine is a TRT capped crossover!

But I think actively bi amping allows for total control of the sound, better amplifier control of the drivers, and a reduction of distortion, because each amp is only handling a limited amount of the frequency range.

It also allows for amps suited for their particular task, like a big solid state honker on the bass, a warm , thick tube amp on the neo panels, and an airy tube amp up top on the spiral tweeters.

Plus, it just so happens that my particular crossover has a CDWG EQ provision in it, as well as adjustable time delay.

My RM 40's are the bi wire versions, w/o the switches, so you gotta either bi wire em, or run jumpers.

I need to know how to go into the RM 40's, and by pass the crossovers in the woofers, and the midrange hi pass section.

Because I will not be tri amping, I will need to use the passive tweeter crossover, and retain it;s level control ?

Has anyone done this before ?

My crossover has 24 db per octave LinkwitZ Riley filters, and drivers will be in phase.

I think I read somewhere that Brian used, or uses a crossover with these slopes, and takes the Neo panels way down to 125 or 150 cycles!

Yes, the slope is steep, but it's way down in frequency, and I am HOPING it will allow me to run the woofers harder, and provide the lower mid range warmth I crave so much.

Any thoughts or Ideas ?
The crossover is waiting, and I have the amps to make this happen.

woodsyi · « **Reply #1 on:** 6 Sep 2006, 01:49 am »

I am doing just that. PM me if you want details. Brian can also tell you what you need to desolder inside.

John Casler · « **Reply #2 on:** 6 Sep 2006, 02:08 am »

Chris,

Maybe I'm not picking up everything here, but all you need to do to "Bi-amp" is run an amp into the top posts for the Woofer system, and the bottom binding posts for the Neos and Tweeter.

Brian can tell you exactly, but if memory serves me correctly, your low pass is around 155Hz or 166Hz and the hand off to the tweeter is around 9Khz to 10Khz.

Today's Low Pass is about 100Hz higher and with the tweeter hand off at 6.9Khz.

However, the reason for this, is that the Midwoofer upgrade made the higher Low Pass possible, and the FST, made the lower high pass possible.

Were you thinking of by-passing the Low Pass, and running it through the Rane?

If so, B, might be able to advise you as to what will and will not work (frequency wise) with that woofer system.

And or how to best attack raising the x-over to the Neo's, whilst still using the passive top hinge.

PLMONROE · « **Reply #3 on:** 6 Sep 2006, 03:14 am »

I asked Brian about this a couple of years ago and as I recall he said you had to remove the large coil (about the size of a hens egg) in the xover to bi-amp (as opposed to bi-wiring).

Brian Cheney · « **Reply #4 on:** 6 Sep 2006, 04:38 am »

Just short out the bass coil (upper terminal board) and biamp away!

warnerwh · « **Reply #5 on:** 6 Sep 2006, 05:24 am »

After doing much research on the subject of biamping I came to the conclusion that active biamping can cause more harm than good quite easily. Reasons are that the designer may not only have the drivers high/low passed but also other parts that correct various issues. Once you actively biamp you bypass this "extra circuitry" which is necessary.

Do what you want but be careful or you could end up with a can of worms I'd think. If I were going to actively bypass I'd want something like a Tact unit so I had alot of control over what is happening.

If you want to know what goes on in a speaker read Vance Dickason's "Loudspeaker Design Cookbook". Get on the Madisound and Partsexpress speaker building forums and ask questions. You'll learn real fast that even a 2 way speaker can be complicated to do well. You'll also learn if you're very smart that there's alot to designing a four way speaker like the RM 40's. Did I say there's ALOT to designing a four way speaker?

Changing crossover points and slopes can open up quite a can of worms imo. The only way I would do it is with the knowledge of understanding everything Before I did anything.

I'd ask Brian what he recommends specifically, period. This of course assumes you haven't already spent numerous hours studying how speakers work.

Then again I could be completely wrong

PLMONROE · « **Reply #6 on:** 6 Sep 2006, 06:00 pm »

Brian for a "quick and dirty" way of configuring my RM-40s for either biamping or normal amping why not solder a wire to each side of the coil, run the wires out through the cabinet, and seal the opening? Then if I wanted to biamp I could connect the leads thus shunting the coil and for normal amping just disconect them. Any downsides to this? Thanks.

John Casler · « **Reply #7 on:** 6 Sep 2006, 06:23 pm »

Normal Bi-amping requires nothing more than connecting two appropriate amps to the correct binding posts.

"ONLY" if you wish to "by-pass" the filters, is more "inside" work required.

woodsyi · « **Reply #8 on:** 6 Sep 2006, 06:57 pm »

John,

Who know what is normal, eh?

I suppose one could use a line level x-over on top of the passive filters if you don't want to go inside for the coilectomy. You just get double filtering which could conceivably work. No?

ctviggen · « **Reply #9 on:** 6 Sep 2006, 08:22 pm »

It would conceivably work, but you wouldn't get the control you need. You really want to be able to control the crossover points and the level (if possible) for each of the two ranges you'll need. If you leave the coil in there, you don't get control over the crossover points. For instance, with a 24db/octave slope, you might be able to have a higher crossover point with the same or lower amount of distortion.

I'm not sure why using a 24db/octave crossover instead of a 6db/octave crossover will let one drive the bass "harder" (the bass/midbass still has to be level matched with the midrange). Also, why would this reduce distortion? It might reduce distortion of the midbass driver, but I doubt it would reduce distortion of the bass driver. The only way it would reduce distortion of the midbass driver (or the bass driver) is if the 6dB slope allows some distortion to occur above the cutoff frequency. I'm not convinced that the midbass is going to be distorting because the midbass cutoff occurs at a relatively low point. So, one would hope that the midbass won't distort until frequencies that are well away from the crossover point. But I've been known to be wrong in the past.

As for your soldering trick, that should work. I believe the coil is in series with the bass/midbass, so shorting the coil bypasses the coil (one of the benefits of a first-order network).

John Casler · « **Reply #10 on:** 6 Sep 2006, 08:35 pm »

Quote from: woodsyi on 6 Sep 2006, 06:57 pm

John,

Who know what is normal, eh?

I suppose one could use a line level x-over on top of the passive filters if you don't want to go inside for the coilectomy. You just get double filtering which could conceivably work. No?

That's for sure.

I was justrying to add "clairity" (hope I didn't confuse).

The binding post configuration on all the present (non-direct drive) RM series speakers allow for (maybe the best term is) "simple bi-amping" as well as "bi-wiring".

I do this with my RM30s, by using two NuFOROCE 9.02's on each speaker. One goes to the Neo/FST binding posts and one to the Woofer system posts.

I didn't want someone to think they had to open their speaker for this.

For "Active" or signal processed biamping, Or "partial" as the original poster wants, then some degree of "surgery" may be required.

Now that we have the "Black Box" (OXO), and the DIRECT DRIVE Speakers, the next step is for B, to start fooling around with the DEQX unit to create "his design" of the best crossover for each model in that domain.

Many know I have been trying to put this in motion for some time, and now the "baby steps" are completed, all we have to do is get ANDRE to send B a unit to play with.

Just think of the possiblities.

ka7niq · « **Reply #11 on:** 7 Sep 2006, 04:48 pm »

Quote from: John Casler on 6 Sep 2006, 08:35 pm

Quote from: woodsyi on 6 Sep 2006, 06:57 pm
John,

Who know what is normal, eh?

I suppose one could use a line level x-over on top of the passive filters if you don't want to go inside for the coilectomy. You just get double filtering which could conceivably work. No?

John or Brian, I want to bypass the ribbons midrange lower crossover, as well as the woofers crossover, but keep the passive tweeter crossover, since my crossover is a 2 way ?

I want my electronic crossover to provide the whole crossover between the mid panels and woofers.

What is the best way to get inside an rm 40, and do all this ?

Where do I start ?

Brian Cheney · « **Reply #12 on:** 7 Sep 2006, 04:49 pm »

Detach the coil to ground on the lower board from the mid crossovers, then short around the caps. To take the mid Lpad out of the circuit lift the ground wires from lug 1 and wire lugs 2 and 3 together.

woodsyi · « **Reply #13 on:** 7 Sep 2006, 04:52 pm »

Here is a picture to get your visual cues.

PLMONROE · « **Reply #14 on:** 8 Sep 2006, 01:10 am »

OK here are some actual results for what they are worth. My RM-40s have spiral tweeters and otherwise are stock except for TRT caps. I passively bi-amped them with a Parasound HCA 3500 on the bottom. This unit has had some $2,800 worth of mods by Empirical Audio and sounds better than stock Parasound JC-1s which are pretty darn good (it also sounds better than my VTL-250s for that matter). On the top I hooked up my Bel Canto Set-40 with premium tubes ( 37 watts per channel). Sounded really good but had too much bass from the more powerful Parasound. I next took the large coil out of the circut and actively bi-amped trying two different Marchand electronic crossovers. With these by giving the Bel Canto 6-8 db more gain I was able to even things up. The first x-over was the solid state Marchand XM-9, crossing over at 200hz. With it the bass was ok but the treble was absolutely crap (and that's being charitable). The other was the Marchand XM-26 tube unit, crossing over at 150hz. WOW! This sounded like a million bucks with deep, tight, solid bass and lovely liquid, transparent treble! Admittedly the crossover frequencies differed but these were the only frequency modules I had and they are not interchangeable between the units. And I don't think the 50hz frequency difference made the difference but I could be wrong. For my part I feel that active bi-amping offers a lot of merit. The next step is to see what my DEQX will do if I can ever get over it's very steep learning curve, which is a nightmare.

woodsyi · « **Reply #15 on:** 8 Sep 2006, 01:40 am »

If you only disabled the coil, I am thinking you are still using the passive highpass on your speakers. Since the Neos are good down to 160Hz, I can't imagine you would want to set the pole that low. Fortunately, I am guessing the passive filter is attenuating the signal and protecting your ribbons. I think this is perfectly fine since you are not subjecting the ribbon amp to the woofer signals and 1st and 4th orders happen to be in phase.

You might want to raise the lowpass on the woofers though assuming you are using 24db slope there.

zybar · « **Reply #16 on:** 8 Sep 2006, 01:42 am »

Quote from: woodsyi on 7 Sep 2006, 04:52 pm

Here is a picture to get your visual cues.

How about a picture that actually shows some detail?

Can you simply make it larger and repost?

George

woodsyi · « **Reply #17 on:** 8 Sep 2006, 01:57 am »

Well,

I could've sworn that was bigger when I uploaded it. Somehow it shrunk.

I figured it out. I linked it to a tumbnail picture.

Now it's better.

ka7niq · « **Reply #18 on:** 8 Sep 2006, 02:02 am »

Quote from: PLMONROE on 8 Sep 2006, 01:10 am

OK here are some actual results for what they are worth. My RM-40s have spiral tweeters and otherwise are stock except for TRT caps. I passively bi-amped them with a Parasound HCA 3500 on the bottom. This unit has had some $2,800 worth of mods by Empirical Audio and sounds better than stock Parasound JC-1s which are pretty darn good (it also sounds better than my VTL-250s for that matter). On the top I hooked up my Bel Canto Set-40 with premium tubes ( 37 watts per channel). Sounded really good but had too much bass from the more powerful Parasound. I next took the large coil out of the circut and actively bi-amped trying two different Marchand electronic crossovers. With these by giving the Bel Canto 6-8 db more gain I was able to even things up. The first x-over was the solid state Marchand XM-9, crossing over at 200hz. With it the bass was ok but the treble was absolutely crap (and that's being charitable). The other was the Marchand XM-26 tube unit, crossing over at 150hz. WOW! This sounded like a million bucks with deep, tight, solid bass and lovely liquid, transparent treble! Admittedly the crossover frequencies differed but these were the only frequency modules I had and they are not interchangeable between the units. And I don't think the 50hz frequency difference made the difference but I could be wrong. For my part I feel that active bi-amping offers a lot of merit. The next step is to see what my DEQX will do if I can ever get over it's very steep learning curve, which is a nightmare.

Thank you for your reply!
A guy I have emailed in the past just RAVED about what a difference Actively BI Amping made on his Eminent Technology LFT 8A Ribbon Speakers.
Though his speakers used a simple passive crossover, there is still passive crossover components "in the way" of the amp/ribbon interface.
These passive components, good as they might be, are not as good as a direct amplifier connection.
They interfere with the amplifiers ability to control the speaker, and add their own sonic signature, even as good as they might be.
Someone once asked, "what is the best capacitor" and a wise man answered "No Capacitor" ...

Now, it must also be said that an electronic crossover introduces noise and colorations of it's own.

But all things being equal, I think active bi amping is the very best way to go.

I second John Caslers "nomination" for a direct drive option for all VMPS speakers.
With the advent of the Behringer and DEQX, as well as the DBX Drive Rack stuff, audiophiles are wanting more and more to bi amp actively.

Brian gives us level pots so us VMPS owners can tailor our sound to our liking.
I think providing us a direct drive option would be the highest expression of Brian's vision ?

As Casler suggested, Brian can provide "settings" for us to start with on our crossovers, and we can take it from there ....

PLMONROE · « **Reply #19 on:** 8 Sep 2006, 03:40 am »

I could probably be persuaded to loan Brian my DEQX for awhile if he would like to try his hand at coming up with some settings.