Active Crossovers

Redbone · « **on:** 23 Jun 2004, 04:29 pm »

Has anyone tried using an active crossover with VMPS speakers, in particular, the RM40s ?

1) Is using an active crossover even a good idea ?

2) Do you have any tips/tricks on crossover points or slopes ?

Thanks

woodsyi · « **Reply #1 on:** 23 Jun 2004, 05:37 pm »

Redbone,

This is my first ever post and it is in response to your question. I will add that I have enjoyed reading your posts concerning your experience with RM40.

I have had RM 40 (TRT upgrade only) for about 5 months -- got them used. I have been passively biamping with an attenuator on the tube amp on the mid/high. I have ordered a Marchand xm44 three way with 200Hz and 50Hz (24dB/oct forth order) crossover frequencies to be used with a Larger Sub. Each module is $10 if I want to experiment. I wanted 60 and 40 but Marchand guy suggested 50 and he will exchange them for either 60 or 40 if I want. I am going to start with one sub and see if I need another or not. I have the crossover, but the larger sub has not yet arrived -- John Casler says that Brian shipped it last week. I should have it by Friday to play with it. I will post my findings.

P.S. I am using ARC VT 100 for mid/high, CJ MF200 for woofers on Rm40, and will start with Adcom 555 GFA

II on the sub.

Redbone · « **Reply #2 on:** 23 Jun 2004, 05:42 pm »

woodsyi, Yes I am ordering the Marchand XM44 also, 4-way. I plan on using a 5 channel Bryston amp to power all four woofers individually, then cross the Neos and finally the FSTs. The fourth order is very appealing both for the steeper slope and for phase coherence. Let me know what you find, I'll have more from my side in a few weeks, with luck.

doug s. · « **Reply #3 on:** 23 Jun 2004, 07:41 pm »

redbone, i suggest speaking w/brian before ordering a 4-way x-over. when i spoke w/him about this a coupla years back, he recommended against actively crossing over the midrange to the tweets, cuz he said the passive is not a simple x-over, but has different steps. mebbe things have changed since then? he *did* recommend going active between woofer & midrange...

woodsyi, even if you have enuff bass output, i recommend getting a second sub for soundstaging. unless the one sub is *directly* in the middle of the speakers, soundstaging will be degraded over using no subs. using two subs will actually improve soundstaging. at least, this has been my experience... of course, if you have each driver of yer larger wired separately, ya could place it in the center, & wire one driver to the left channel, the second to the right. mite be a decent compromise over a second sub. but, personally, i'd rather have two original subs than one larger, if that were the choice...

doug s.

zybar · « **Reply #4 on:** 23 Jun 2004, 08:10 pm »

Brian has told me numerous times not to try and mess with the midrange/tweeter crossover.

He also told me to get x-over with 4th order and 24db slope.

George

Redbone · « **Reply #5 on:** 23 Jun 2004, 08:15 pm »

Thanks for the info Doug.

The woofer XO is clearly a simple 1st order coil inductor,Coil in back. The midrange bandpass XO is a bit odd, Pic, with unusual pairings of inductors and caps. The tweet XO appears to be a standard 2nd order coil/cap XO, however.

Don't know for sure, but I'm willing to give it a try. I won't do anything that can't be undone, I hope.

zybar · « **Reply #6 on:** 23 Jun 2004, 08:17 pm »

Why not call Brian and discuss before doing anything?

George

OBF · « **Reply #7 on:** 23 Jun 2004, 08:44 pm »

Wouldn't a steep slope from an active on the woof / mid crossover further reduce impact in the midbass/lower mids as the cones would no longer roll off gradually from the current 1st order slope?

woodsyi · « **Reply #8 on:** 23 Jun 2004, 08:52 pm »

Doug,

Thanks for the info. I have read may discussions on single vs. stereo subs and the (non) directionality of sound below 50 Hz. Now I get to test the theories. I will start with one sub and add one more if I can't stand the skewed sound stage. For financial and logistical reasons, I hope I don't need the second one, but I have an inkling that I will eventully get a second one -- I sure hope they can be place right against a wall.

I wanted to get a larger sub with larger woofers to extend the bottom end. I don't know if my home theater experience is changing the way I listen to music or not, but I found the cannon blasts of 1812 overture on 2-channel SACD wanting on RM40 compared to the multi-channel SACD rendition of it on my run of the mill 7.1 home theater setup. Also, I am hoping that relieving the low bass duty on RM 40 will make the mid bass tighter and more forcefull. With the gain control on the XM44, I sort of have an 3 band EQ -- more stuff to play with. It's a good thing that my wife and daughter demand my time, or I would be a total recluse in the basement.

zybar · « **Reply #9 on:** 23 Jun 2004, 08:57 pm »

I have 2 Larger subs (currently only doing HT duty till I decide to go active or not) that I have been using and it is amazing how good they are.

With proper placement, I am getting decent output at 16hz!!

I have tried running a single Larger as an experiment. Although good, it was nothing like running both at the same time.

BTW, I also have RM 40's.

If I go active, I am not sure if I would get a 2 way or 3 way x-over. Seems overkill to bi-amp the 40's when the subs are in the picture, but I just might....

George

ctviggen · « **Reply #10 on:** 23 Jun 2004, 09:19 pm »

I've also read that sounds from subs are non-directional, but I could easily pinpoint my sub at my previous residence. I only had one sub and had it fairly far to the side, though. If you could get it in the middle it might not be bad. Were I to do this, I'd go stereo subs. For now, I use my sub solely for movies.

Redbone · « **Reply #11 on:** 23 Jun 2004, 09:50 pm »

Quote from: OBF

Wouldn't a steep slope from an active on the woof / mid crossover further reduce impact in the midbass/lower mids as the cones would no longer roll off gradually from the current 1st order slope?

Indeed ! If the order of the XO is changed, then the XO point must change as well. With a steeper slope, the lowpass for the woofs can be increased substantially, conversely, the highpass for the mids can be lowered. Where to go, what to do ? Too many choices !

I have already fooled around with some simple 1st order XOs on the woofs. IMHO, 10 or 20, even 50 Hz doesn't make any difference, at least on a ~200Hz XO point. At 5000 Hz, it takes 500-1000 Hz to hear a change, but it is the same in percentages, if you follow the logic.

doug s. · « **Reply #12 on:** 24 Jun 2004, 01:00 pm »

Quote from: Redbone

Indeed ! If the order of the XO is changed, then the XO point must change as well. With a steeper slope, the lowpass for the woofs can be increased substantially, conversely, the highpass for the mids can be lowered. Where to go, what to do ? Too many choices !

I have already fooled around with some simple 1st order XOs on the woofs. IMHO, 10 or 20, even 50 Hz doesn't make any difference, at least on a ~200Hz XO point. At 5000 Hz, it takes 500-1000 Hz to hear a change, but it is the same in percentages, if you follow the logic.

if yure going active w/24db/octave slope at the woofer-midrange x-over, ya may wanna try 250-300hz x-over point. i'd discuss w/brian about this...

doug s.