[Danny Richie]

I have had a lot of questions sent to me regarding the upgrade I made on the VMPS 626R and I thought I would post the questions and answers that are getting asked over and over as I am sure others may have the same questions.

Question 1). Can the mod be made on my older 626 with the circular tweeter?

The same woofer and tweeter network can be used but the tweeter network would be completely different and would require more design work.

Recommendation is upgrade the tweeter too.

The heart of the great performance of this speaker is more centered around the tweeter than before.

Before it only played from 10kHz and up. Anything could have been used there and the current ribbon was under utilized.

Now crossing at 3.5kHz the ribbon is a strong asset.

Go to E-speakers and order the G2si. http://www.e-speakers.com/products/ac-ribbons.html

They are only $80. each. Maybe Brian will match that price and you can order them from VMPS too.

The impedance of the G2si is listed at 6 ohms. The impedance of the one I measured in the 626 measured 8 ohms, but everything else appeared identical. I have some G2si's in stock for reference.

The face plate on the VMPS is slightly different too, but performance and sound are all the same. The response curve is pretty much the same too.

Because of the different impedance a slight adjustment to the resistor value in line with the tweeter can be made to adjust it.

If they fit the same hole, and I bet they do, then it should be an easy drop in replacement.


Question 2) Will you be coming out with any mods for the RM-40 like you did for the 626R?

Not likely. Think of the RM-40 as a wide spread WMTMW design.

Crossover points are dependant on the distances of the acoustic centers.

The acoustic centers of the tweeter to mid panels looks to be about 15". The crossover point needs to be less than 1/2 of that wavelength to avoid the same vertical cancellation errors that plagued the 626R.

This would put the mid tweeter crossover point in the 500 to 600Hz range.

I don't believe that tweeter can play down that low.

Correcting the cancellation errors like what was done with the 626R is not possible. It can be made a lot better by lowering the crossover point but there will still be some cancellation in the vertical plane, so listening height will be limited to tweeter level.

There were many more questions but there were a lot that in one way or another were just like these two.

If you have other questions feel free to ask and I'll do what I can to answer them.

[JoshK]

Wow, not to put words into your mouth but from reading between the lines it seems as though you are suggesting that the RM40's are fatally flawed and not worth fixing.

[Danny Richie]

I wouldn't say that.

I just can't correct those issues in a way that I was able to with the 626R. Acoustic centers on the 626R are much closer.

Anything can be improved. Even my own speakers are subject to ongoing improvements.

I tend to think the RM-40's could see considerable improvements too.

As many people that have asked me about it, I wouldn't be surprised to if someone decides to send me a pair for upgrading.

[JoshK]

K, thanks.  Was just curious what was meant.

[Mad DOg]

...Anything can be improved...

this comment is right on...

anything and everything can be improved upon...just depends on how much time and money one wants to or is willing to spend...

[Andrikos]

I hope this thread doesn't degrade like the last one...
People who are offended by such unthinkable suggestions that something maybe improved upon, need not read. My 2c anyway...

[brj]

Regarding modifications to the RM40:

Correcting the cancellation errors like what was done with the 626R is not possible. It can be made a lot better by lowering the crossover point but there will still be some cancellation in the vertical plane, so listening height will be limited to tweeter level.

I seem to recall that Brian specifically designed the RM40 around the listening height of a seated person, and the tweeter height reflects that design goal.  I guess I interpreted the above statement to basically support that position... if you are listening with your ears at the level of the tweeter, any cancellations will be minimized.  Shift out of that spot and the cancellations become noticeable.  Yes?  No?

The one RM40 I've heard (older spiral ribbon model, but driven by excellent gear in a well treated room) sounded stunning in the sweet spot, but definitely changed character as you moved outside of this spot, especially in the vertical direction.  (The importance of sweet spot size and sound quality outside of the sweet spot is obviously a personal preference.)

[Danny Richie]

I hope this thread doesn't degrade like the last one...

Me too.

... if you are listening with your ears at the level of the tweeter, any cancellations will be minimized. Shift out of that spot and the cancellations become noticeable. Yes? No?

Yes, you are correct.

What I noticed with the 626R was that even a slight movement (like 2") caused big shifts.

With the crossover in the RM-40 also being in the 10kHz range I would suspect them to be as bad or worse.

Shifting it down to the 3kHz range or so would solve a lot of it and give a much larger vertical window with smoother horizontal response as well.

But there will still be some cancellations in the vertical plane there is just no way around it.

[Tyson]

The 40's cross over to the new FST tweeter in the 7khz range.  The old dual-spiral tweeters were at 10khz, but not anymore.

I'm still wondering why the upper woofer does upper bass, but not the lower woofer.  It seems like a lot of the issues w/the 40's mid & upper bass would be fixed if both the top and bottom woofer did mid-bass, and the crossover point was raised a bit.

[Marbles]

With the crossover in the RM-40 also being in the 10kHz range I would suspect them to be as bad or worse.

Shifting it down to the 3kHz range or so would solve a lot of it and give a much larger vertical window with smoother horizontal response as well.

But there will still be some cancellations in the vertical plane there is just no way around it.

The XO has been in the 7Khz range for a while now (with the FST).  There may still be early ones with the 10Khz XO floating around though.

[pjchappy]

Yeah, that 626 sounds like the older ones to me, too.

Also, I'm 90% sure they come w/ fiberglass installed, too, even the old ones.

Could the one you modded have been a KIT?

p

[Danny Richie]

The 40's cross over to the new FST tweeter in the 7khz range.

That makes sense because the comb filtering effects of having a line of the planar drivers stacked up like that will eat away at the highs and could cause them to start rolling off before they ever reach 10kHz.

Also, I'm 90% sure they come w/ fiberglass installed, too, even the old ones.

There was insolation in these too. Just a small handful at the top of the box.

Could the one you modded have been a KIT?

I don't think so. These were a pair that was owned by John Casler.

[pjchappy]

Danny,

Just out of curiosity, could you make some general comments. . .even pre-mod. . .of the sound of your Criterion 2-way vs. the 3-way of the VMPS. . .

I've heard neither, but, I was just wondering about your comments regarding the use of a planar mid and it's blending into the ribbon tweeter, etc. . .

Thanks!

p

[hoosier21]

Danny

If you have already posted the price I missed it.

How much is the modified 626R crossover from you?

[wshuff]

Danny,

Just to confirm, this mod is only for the 626R with the FST (ribbon tweeter), not the spiral, but with your mod a G2 or whatever the tweeter used in the Criterion/Diluceo could be added.  Correct?

Also, does the $60.00 x-over mod measure as well as the more expensive mod?  And do they sound comparable?

Thanks.

[Danny Richie]

Just out of curiosity, could you make some general comments. . .even pre-mod. . .of the sound of your Criterion 2-way vs. the 3-way of the VMPS. . .

Nope, no way I could do that without somebody getting pissed.

They do basically use the same tweeter... and sound the same throughout that range.

The both have a low 85 to 86db sensitivity. You know, the obvious...stuff, I'll say all that.

I've heard neither, but, I was just wondering about your comments regarding the use of a planar mid and it's blending into the ribbon tweeter, etc. . .

Blending the planar and the ribbon is no problem.  Blending the Planar and a cone driver is a greater transition.

If you have already posted the price I missed it.  How much is the modified 626R crossover from you?

See info: http://www.gr-research.com/vmps626r.htm

"Right now parts total comes to less than $160. per speaker for Alpha Core foil inductors, Sonicaps, and Mills resistors.

Using Axon caps, foil inductors and Links resistors the parts total per speaker comes in at less than $60. a speaker"

Just to confirm, this mod is only for the 626R with the FST (ribbon tweeter), not the spiral,

Yes.

but with your mod a G2 or whatever the tweeter used in the Criterion/Diluceo could be added. Correct?

The G2si tweeter (just like the one used in the latest Criterion) can be used. It does appear to be the same tweeter used in the 626R.

Also, does the $60.00 x-over mod measure as well as the more expensive mod?

Sure. Electrically it will measure exactly the same.

I posted the prices for the parts that way so everyone could see that these could be modded without spending a lot of money.

And do they sound comparable?

The Mills resistors are better and have a cleaner sound than the lesser expensive Links, but it is not huge.

The Sonicaps are a significant upgrade over the Axon caps. Similar to the TRT upgrade over the Axon caps. There is added clarity, detail, lower noise floor, air and space that exceed what is possible with the Axon caps.

I personally feel (having used the TRT's too) that the Sonicaps are a better cap. They are more neutral (less coloring) and offer a clearer picture into the music. They are also very reasonable.

[wshuff]

Thanks Danny.

Like the person above, I also have the LRC, and mine is the older model with the spiral ribbon tweeter.

I don't know that there is much info about it anywhere except here:

http://www.vmpsaudio.com/lrcpic.htm

and here:

http://www.vmpseurope.com/e/p-ht.htm

Not much to go on.

[DFaulds]

I would suggest that one of you LRC owners forward their speaker to Danny and let him give it a thorough going over.

[Danny Richie]

I am guessing that there would be the same issues with the center channel that I saw with the 626R's.

I would have to have one here to upgrade it the way I did the 626R.

Seams like the Planar could have been laid on its side and crossed to the tweeter, positioned above, at around the 3.5kHz to 4khz range and it would have an even response to the left and to the right.

Woofers could be pulled in closer too... Hmmmm.

If enough people are interested to make it worth while I'll do it.

First I think it is important that people hear this new one and compare it to the older one so you guys can have un-biased feedback.

[BrunoB]

They do basically use the same tweeter... and sound the same throughout that range.

The both have a low 85 to 86db sensitivity. You know, the obvious...stuff, I'll say all that.

I looked at the specs for the Diluceo and Criterion. The dual woofer speaker is much more sensitive (91 db). I just wonder why (curiosity question).

I guess that the LRC is more sensitive than the 626 because of the two woofers?.