[SpeakerDoc]

Thanks for the tips, these already have lambs wool, and I will check
the seal as you suggest.

It would be nice if people upgrading to the newer 2.7 ohm panels
would trade-in their 4.7 ohm ones or make them available for
those of us who just need to replace one and don't want to do
the entire array.

Are yours 4.7 or 2.7 DC resistance?

[DFaulds]

I am considering buying a few spare mid panels. I don’t ever plan on replacing my VMPS speakers (well maybe upgrading the center to an RM40 once my HT room get built) and the supply of these drivers is limited to what Brian has in stock. With 13 panels total in my system one may just go or get damaged somewhere down the line.

Is that true?  I thought that Brian had a new OEM supplier for the panels.

[SpeakerDoc]

I've decided to redo all the connections to the mid panels since the soldering is not that clean, and the screws are protruding a lot.  I purchased 1/4" stainless steel 4-40 screws, nuts and #6 nylon washers and Amp ring terminals that look exactly like the originals.  I think the screws are 1/8" shorter and do not protrude like the originals.  The nylon washers help with the issue of the nut coming close to the metal frame.  It seems that the screw head is on the inside because the ring terminals would not work well with the larger nut.  The ring has to touch only the central part of the metal conductor and might short elsewere if pushed down by the larger nut at a larger diameter.  Put a bit of DeOxit on the metal ring terminal where it makes contact.

Also purchased #4 X 5/8" stainless steel machine screws to mount the panels in place.  These are the same size as was used by the factory but they catch in the frame of the mid panel as did the originals.  I plan to very gently drill out the hole in the mid panel so that the screw only grips the wood of the enclosure as it should.

[SpeakerDoc]

EDIT:  This was operator error, the gain setting was inadvertently different for one run in LAUD.  Reran and now all panels (even the 2.7 ohm with a 1.3R pad) match within about +/-.5 dB below 2 KHz and mostly +/- 1 dB above 2 KHz.  This is excellent!  They are far from flat but they are not mounted - simply laying on top of 2 large panels of acoustic foam.

EDIT: Disregard the mismatch issue mentioned here:
Measured the 4 midrange panels with LAUD in MLS mode.  2 of the 4.7 ohm panels match very well, with their curves nearly being right on top of each other, the 3rd is about 3 dB less efficient which is not at all good.  Was there more than one production run with different strength magnets?  I am going to redo the measurement just to be sure.

The 4th is a 2.7 ohm version and requires a 1.3 ohm resistor in series with it to match the voltage sensitivity.  The match with this resistor is also excellent.

The poorly matching panel is unfortunate, anyone know what is going on with it?

[Construct]

Measured the 4 midrange panels with LAUD in MLS mode.  2 of the 4.7 ohm panels match very well, with their curves nearly being right on top of each other, the 3rd is about 3 dB less efficient which is not at all good.  Was there more than one production run with different strength magnets?  I am going to redo the measurement just to be sure.

The 4th is a 2.7 ohm version and requires a 1.3 ohm resistor in series with it to match the voltage sensitivity.  The match with this resistor is also excellent.

The poorly matching panel is unfortunate, anyone know what is going on with it?

I wonder if one is an alnico and the other a neo magnet???     Either that, or if the two ribbons are from different companies like B+G, Monsoon etc...

[SpeakerDoc]

EDIT:  Panels are not Monsoon, see next post by BC:
They all look identical, the 2.7 also looks the same but with a bar code label.  I was told here that they are the Monsoon units as I understand it, anyone know if these were made with different types of magnets?

[Brian Cheney]

The panels from earlier runs had quite a bit of varying sensitivity, the later low impedance panels are a lot more uniform.  All magnets are neodymium.  All panels are Sonigistix/Level 9, not the automotive panels or computer speakers marketed as Monsoon.

[SpeakerDoc]

EDIT:  See post 23 there is no mismatch, it was operator error - this is very good news!

EDIT:  No need for a new panel:
Thanks Brian, so it would seem that the best solution is to order a 2.7 ohm panel to match the other one.  I'll put the low sensitivity panel at the bottom for now and do some more listening.

[SpeakerDoc]

Here is an overlay plot of the four midrange panel FR curves, note that the maroon curve is the 2.7 ohm panel without a pad resistor and is higher as it should be.  I adjusted the pad resistor to 1.2 ohms to bring the 2.7 ohm panel closer to the norm, it is a very small change.  Image quality is not so good unfortunately:

[Brian Cheney]

I should note the crossover includes a series filter which flattens the 11kHz peak and smoothes the response above 5kHz.  The active crossover in the SDE versions also reduces the "presence peak" around 2kHz by the requisite 3dB or so.  With these corrections the panel is flat and extended.

[SpeakerDoc]

Ok, I have tested and retested this to be sure:
Looking at the acoustical pulse measured by the MLS system
the older 4.7 ohm panels seem to produce a negative going
pulse for a positive input as labeled on the panel. 
The newer 2.7 ohm panel produces a positive going acoustical
pulse with the same input.

I've checked it and rechecked it, and have done a sanity check
on the measurement system with a cone midrange that has
known correct polarity.

Has this been noted before?

Are the 2.7 ohm panels wired with opposite polarity as compared to the older 4.7 ohm?

Do all RM40s have the mid panels wired in phase with the input, that is neg on the input terminals to neg on the panel array assuming the terminals are properly labeled?

[Brian Cheney]

Yes, all drivers are electrically in phase.  We check for polarity with a 0V battery, an easier test that what you're doing.  We have run across 4.7 Ohm panels that were reverse magnetized, which is why we check.  If you find reverse magnetized drivers just switch the wiring.

[SpeakerDoc]

Yes,  I just tried a 1.5V battery and it works fine and confirmed what I previously
found.  Tried the other speaker with them in place since the panels are in series
they are somewhat isolated from the crossover inductor.  All the panels in the
other speaker are reversed.  I did this by jumping the battery to the panel posts
protruding out the front of the speaker - system disconnected from the amp of
course.

Thanks for the info Brian, I'm anxious to get these back together - with the panels
in the correct polarity!

It might help if you provided some sort of permanent marking to indicate the true
positive terminal when you test them at the factory.

[SpeakerDoc]

Is there any particular type of solder suggested by Brian?

[SpeakerDoc]

Just looking over the crossover and all the caps but two, are red are these TNT caps,
can anyone confirm?

There is one smaller yellow cap in parallel with the midrange bundle, is this a film
and foil cap, anyone know the brand?

There's a very small orangish poly cap across the woofer terminals, a 103 or .01 uF.

[John Casler]

Just looking over the crossover and all the caps but two, are red are these TNT caps,
can anyone confirm?

There is one smaller yellow cap in parallel with the midrange bundle, is this a film
and foil cap, anyone know the brand?

There's a very small orangish poly cap across the woofer terminals, a 103 or .01 uF.

TRT Dynamicaps are generally RED and LARGE

[Brian Cheney]

I use 4% silver solder from parts express.

The caps are all TRT, either Infinicaps or other kinds.

[SpeakerDoc]

I have a few more comments on how I reassembled this speaker
but thought I'd mention this first:

First unit is back together and playing, sounds very good.
These have the dehorned tweeters with I think a slotted
Dynamat sheet covering the guts of the tweeter.

The Dynamat was not on evenly so I pulled it, also to check
the tweeter connections, and now the tweeter is completely
open with a good view of the ribbon.

We can see it moving about 1/16" to the bass line, LOL, woha!
and I'm not pushing it that hard only 100W/ch amp, I really want
to go to my other 200W amp but this is concerning.  Actually I
want to run 200W to the each side high end and 200W to each
woofer section with matching amps that I have.  Not going to do
it until I figure this out.

One of the two tweeters had the ribbon replaced and I wonder
the tension is right.  Is the procedure for replacing the ribbon
available online somewhere?

[Brian Cheney]

That is likely airborne vibration causing the ribbon deflection, since the moving mass is only 13 mg.  You can reduce this motion by installing the tweeter faceplate and wire mesh cover.

Ribbon replacement instructions have been posted here recently, John Casler will know where.

[SpeakerDoc]

It is moving to the bass line beat of the music.