Upgrading older RM40s with ribbon tweeters

Brax · « **on:** 30 Dec 2009, 04:18 pm »

Hello Everyone,

I have an older set of RM40s and have completed most every upgrade, except for replacing the spiral tweeters with a FST (ribbon) tweeter. Brain no longer offers the FST tweeter as a field upgrade, so I am looking at alternatives. AC G2s or even LCY-108s look like they would work. Those tweeters aren’t up to the standards of the VMPS FST, but I thought I could use two per speaker. I should have no problem with the cabinet work needed and even making custom face plates for these tweeters.

I am looking for advice on how to adjust the crossover point between the mid panels and the tweeters from the present 10 kHz down to 7 kHz. I have read that dropping the upper end of the mid panels improves their sound, but this is only possible with a tweeter that can reach down to 7 kHz like the FST.

I do have the TRT caps in my RM40s if that makes a difference. I don’t think I’m ready to upgrade to an active cross over just yet, maybe someday. Any help would be appreciated.

PMAT · « **Reply #1 on:** 30 Dec 2009, 04:58 pm »

Hi Brax, this is what I am putting in my VMPS speakers to replace the Infinity circular ribbons, The look matches the RM-40's and they also supply a round mount for $12 for these and it looks great.

http://www.parts-express.com/pe/showdetl.cfm?Partnumber=264-730

Check this out as well.

http://zaphaudio.com/nondomes/

John Casler · « **Reply #2 on:** 30 Dec 2009, 07:36 pm »

Quote from: Brax on 30 Dec 2009, 04:18 pm

Hello Everyone,

I have an older set of RM40s and have completed most every upgrade, except for replacing the spiral tweeters with a FST (ribbon) tweeter. Brain no longer offers the FST tweeter as a field upgrade, so I am looking at alternatives. AC G2s or even LCY-108s look like they would work. Those tweeters aren’t up to the standards of the VMPS FST, but I thought I could use two per speaker. I should have no problem with the cabinet work needed and even making custom face plates for these tweeters.

I am looking for advice on how to adjust the crossover point between the mid panels and the tweeters from the present 10 kHz down to 7 kHz. I have read that dropping the upper end of the mid panels improves their sound, but this is only possible with a tweeter that can reach down to 7 kHz like the FST.

I do have the TRT caps in my RM40s if that makes a difference. I don’t think I’m ready to upgrade to an active cross over just yet, maybe someday. Any help would be appreciated.

Hi Brax,

Only Brian can answer your questions properly.

I know some cabinet surgery is involved and a few years ago a couple RM40 owners did use dual FST tweeters, but obviously there was some equalization and cap adjustments to the XO.

Below is the picture of the result.

ctviggen · « **Reply #3 on:** 30 Dec 2009, 07:50 pm »

Are those gigantic surround speakers?

John Casler · « **Reply #4 on:** 30 Dec 2009, 07:58 pm »

Quote from: ctviggen on 30 Dec 2009, 07:50 pm

Are those gigantic surround speakers?

Hey Bob, Happy Holidays

No, I don't think these are used that way, but I do have a VMPS owner who has what I call VMPS STONEHENGE Home Theater.

It consists of the following:

CENTER: VMPS RM40 (horizontal orientation)
MAINS: Pair VMPS RM40s
SIDE SURROUNDS: Pair VMPS RM40's

It looks like STONEHENGE sitting in amongst that set up.

The sound is simply incredible

Brax · « **Reply #5 on:** 30 Dec 2009, 08:43 pm »

John,

I did PM Brian and he said he did not have crossovers for the AC G2s but I could experiment with the treble crossovers, using at least 12dB per octave for a 7kHz characteristic.

I really don't know much about crossovers, but could follow directions if someone could give me very detailed directions on how to change the crossover.

I do have a LRC now and hopefully will upgrade to an RM40 center once my HT room nears completion. (unless I am forced to purchase early because of a smoking good deal)

PMAT, let me know how those Neo3 tweeters work out for you, the look really promising. I like the fact that they will double stack in the same space the spirals take up. All you need to do is trim the faceplates and your set.

PMAT · « **Reply #6 on:** 31 Dec 2009, 05:05 am »

Hey Brax, the meat of the sound is in the bottom end and the mids. The FST is overrated as a huge improvement over the spirals. The BG tweets are sweet sounding alternatives that don't break the bank, and look right with the mids. They don't have the bite of the spirals and are not so easy to damage as the FST's. Your speakers are great to modify. Have fun.

ctviggen · « **Reply #7 on:** 5 Jan 2010, 11:58 am »

Quote from: John Casler on 30 Dec 2009, 07:58 pm

Hey Bob, Happy Holidays

No, I don't think these are used that way, but I do have a VMPS owner who has what I call VMPS STONEHENGE Home Theater.

It consists of the following:

CENTER: VMPS RM40 (horizontal orientation)
MAINS: Pair VMPS RM40s
SIDE SURROUNDS: Pair VMPS RM40's

It looks like STONEHENGE sitting in amongst that set up.

The sound is simply incredible

That's out of control!

audiochef · « **Reply #8 on:** 6 Jan 2010, 07:29 pm »

Hi guys, and there's still nothing else out there that I'd rather own.
My audiophile buddies have made sideways moves, I've watched and listened as my 40s still remain top notch. Mostly listening to vinyl now (again).

Brax · « **Reply #9 on:** 15 Jan 2010, 02:16 am »

John C., are you using red oak for the veneer on the light oak cabinets? I would like to match the finish of my 40's

Brax · « **Reply #10 on:** 18 Jan 2010, 01:15 am »

Does anyone know if VMPS is using red oak for the veneer on the light oak cabinets?

I would like to match the finish of my 40's. Mine have the black fronts and I'd like to veneer it tp match the sides. In my HT room I want to run the speakers without grills because I thing they are impressive looking that way.

John Casler · « **Reply #11 on:** 18 Jan 2010, 02:34 am »

Quote from: Brax on 18 Jan 2010, 01:15 am

Does anyone know if VMPS is using red oak for the veneer on the light oak cabinets?

I would like to match the finish of my 40's. Mine have the black fronts and I'd like to veneer it tp match the sides. In my HT room I want to run the speakers without grills because I thing they are impressive looking that way.

In my best Dirty Harry impersonation lip snarled and eyes squinting;

Ya know, in all the excitement, I don't remember if I answered 4 questions or five, and seeing as how this is the VMPS Circle and can blow your ears clean off, you have to ask yourself do you feel Lucky?

Anyhow, after all that, sorry I missed your question and to be honest, I don't know if B has any of the red veneer left.

Maybe he can answer this when he logs on.

Brax · « **Reply #12 on:** 18 Jan 2010, 03:16 pm »

John, thanks for the response. The veneer looks like flat cut red oak but I just wanted to confirm that it was red oak and not white oak. I assume Brian has these cabinets outsourced and getting veneer would be difficult. I can pick up the veneer locally so that's not a problem. I'm first going to veneer my subwoofer cabinets and if I can get them to match the 40's I'd like to veneer the fronts to match the sides. I guess worst case, I can just veneer the whole speaker.

Brax · « **Reply #13 on:** 29 Mar 2010, 11:05 pm »

On inspection of my LRC I see that a few of the “metal” rings on the spiral ribbon tweeter are broken and coming loose. I was playing with the idea of replacing the spiral ribbon tweeters in my LRC and RM40s anyway so I will just move up my timetable for replacing them. I keep going around and around about what to replace them with. My RM2s have the VMPS FSTs. Here are a few options I was thinking of.

LRC – Single Aurum Cantas G2
RM40 – Single Aurum Cantas G3

LRC – Single B&G Neo3 PDRW
RM40 – Double B&G Neo3 PDRW

LRC – Single LCY-110
RM40 – Single or double LCY-110

Any thoughts on these combinations or recommendations for others?

pjchappy · « **Reply #14 on:** 29 Mar 2010, 11:07 pm »

Why not just get the FST from Brian? I believe Brian still has mounting "brackets" (not sure what they're called) for them for those who make such an upgrade.

Paul

fredgarvin · « **Reply #15 on:** 30 Mar 2010, 12:10 am »

If I recall correctly the FST is a modified Aurum Cantus. I seem to remember it involved some simple routing of the cabinet to replace the spirals with an FST and Brian has brackets. I wouldn't think slapping in some NEo's would be so easy. No doubt the driver characteristics would call for some thoughtful xover changes to intgrate them properly with the mid panels.

Brax · « **Reply #16 on:** 30 Mar 2010, 12:39 am »

Brain said the FST is no longer available as a field upgrade for the RM40.

Brax · « **Reply #17 on:** 2 Apr 2010, 01:15 pm »

I have decided to use a AC G2 on my center speaker and a AC G3 on my RM40s. These will match up better with the FST tweeters in my RM2.

Mounting of the G2 will only require routing of the flange recess to the slightly larger diameter of the G2 and enlarging the clearance hole. This shouldn’t be too much of a problem. Replacing the dual spiral tweeters with the G3 for the RM40s is a little different. I think the best way to do this is to fabricate a new face plate for the G3 since the one it comes with is too narrow for recess the spirals occupy.

Still looking for any advice on how to drop the crossover point between the mid panels and the tweeter to 6.9kHz. I believe the existing crossover point is at 10kHz. Brian said “You can experiment with treble crossovers, use at least 12dB per octave for a 7kHz characteristic.” but really knowing nothing about speaker crossovers, I wouldn’t know where to begin.

PLMONROE · « **Reply #18 on:** 2 Apr 2010, 03:52 pm »

Might it not require less of a "learning curve" to simply bi-amp and use an electronic crossover such as the Behringer DCX2496 (street price $299 including shipping)? That way you could just dial in all the crossover settings and even experiment with changes to your hearts content. An added advantage would also be a probable improvement in sound.

Paul

Brax · « **Reply #19 on:** 2 Apr 2010, 06:22 pm »

To gain control of the crossover frequency between the mid range panels and the tweeters, I think I would need to tri-amp. Not only would I need the electronic crossover but I also would need to have three separate amp channels per speaker, install another set of terminals and remove the analog crossover completely out of the signal path.