RM40 FAQ

SpeakerDoc · « **Reply #40 on:** 13 Aug 2010, 01:16 pm »

Is that airborne vibration coming from the woofers, I wonder?
This would explain it following the bass line.

I can turn the tweeter pad all the way down and see if it still
moves if so, then yes it could be the woofer pressure change.

SpeakerDoc · « **Reply #41 on:** 14 Aug 2010, 01:45 am »

OK, I see a lot of movement on another cut, very large excursion on
the strumming of a guitar; I'd say at least 1/16" at the center of the
ribbon. I left the volume in the position where I saw the excursion
and disconnected the woofer section, still does it. Played just the
woofer section, and no movement of the ribbon, stop the music and
no movement of the ribbon. It is clearly the source material.

SpeakerDoc · « **Reply #42 on:** 14 Aug 2010, 01:34 pm »

EDIT: Link to Aurum Cantus ribbon replacement instructions:
http://www.aurumcantus.com/aurumcantus-download/pdf/Repair%20Instructions%20for%20ribbons.pdf

Brian told me in a previous phone conversation that the Aurum Cantus G2Si
replacement ribbon is the right one and it is available from Parts Express:
http://www.parts-express.com/pe/showdetl.cfm?Partnumber=276-401

Any VMPS specific tips would be appreciated:
A maintenance sticky would be helpful, otherwise, John Casler could
you please point to the ribbon replacement instructions? TIA

A thread that mentions ribbon replacement:
http://www.audiocircle.com/index.php?topic=83201.msg803455#msg803455

SpeakerDoc · « **Reply #43 on:** 14 Aug 2010, 05:25 pm »

There was mention of this previously:
http://www.audiocircle.com/index.php?topic=3348.msg32452;topicseen#msg32452

SpeakerDoc · « **Reply #44 on:** 14 Aug 2010, 05:40 pm »

I measured the tweeter crossover frequency response when I had
the system open and decided to pull that response curve up and
take a closer look. This is a second order electrical but quasi first
order type but all I saw was a pure first order 6dB/oct rolloff. I had
noticed that the tweeter inductor did not seem to have any copper
or silver showing as it went into the solder joint and wondered if
the insulation had been scraped off or not. I measured across the
solder joints with the LPAD all the way up and the tweeter removed
and thought I measured continuity so did not resolder any of the
joints.

I removed the tweeter and turned the LPAD all the way up to take
it out of the circuit, now measuring DC resistance directly at the
tweeter leads should measure the DC resistance of the shunt inductor
to ground - it measured an open circuit. I am certain that the LPAD
was making a connection because I could hear a faint click from the
mid panels due to the caps charging and the common connection of
the tweeter and mids at the input terminals.

I got a spare .25 mH inductor and wired it directly across the tweeter
terminals and retested. There is no longer any visible movement of
the ribbon.

Time to try the bigger amps about 300W/ch on bass and 250/ch on
mid/tweeters.

Brian Cheney · « **Reply #45 on:** 14 Aug 2010, 06:24 pm »

If the previous owner replaced a treble cap then the coil lead would have been short, and he could have failed to make good contact with it when resoldering . The deinsulated part of the coil lead is quite long (about 3/4") and it is soldered originally at the factory along its full length to ensure continuity, then trimmed.

SpeakerDoc · « **Reply #46 on:** 14 Aug 2010, 06:43 pm »

Thanks Brian,

I'm going to have to open them up again to determine
exactly what the problem is and my post was from memory. It is good
enough for now and sounding even better.

John Casler · « **Reply #47 on:** 14 Aug 2010, 06:59 pm »

Quote from: SpeakerDoc on 14 Aug 2010, 01:34 pm

EDIT: Link to Aurum Cantus ribbon replacement instructions:
http://www.aurumcantus.com/aurumcantus-download/pdf/Repair%20Instructions%20for%20ribbons.pdf

Brian told me in a previous phone conversation that the Aurum Cantus G2Si
replacement ribbon is the right one and it is available from Parts Express:
http://www.parts-express.com/pe/showdetl.cfm?Partnumber=276-401

Any VMPS specific tips would be appreciated:
A maintenance sticky would be helpful, otherwise, John Casler could
you please point to the ribbon replacement instructions? TIA

A thread that mentions ribbon replacement:
http://www.audiocircle.com/index.php?topic=83201.msg803455#msg803455

Hi Doc,

Yes it sounds like your RM40's previous owner may have made a few errors. The Tweeter Ribbon should not be BASS Dancing.

The ribbon replacement instructions I am aware of are the ones you linked to above from the arum cantus.

I will copy and past them to the STE UP stickie since I can no longer create stickies.

SpeakerDoc · « **Reply #48 on:** 15 Aug 2010, 12:03 am »

Thanks John

SpeakerDoc · « **Reply #49 on:** 15 Aug 2010, 01:27 am »

The tweeter from the second system does not look to be in very
good shape can I just buy a G2Si from Parts Express?
http://www.parts-express.com/pe/showdetl.cfm?Partnumber=276-400

I noticed that foam is used around the FST tweeter shown in this
picture can I purchase those foam pads from VMPS?
http://www.vmpsaudio.com/pics/626R_FSTrosewood.jpg

I'm also interested in trying the original Aurum Cantus tweeter
face plates, does VMPS have those from tweeters that have been
dehorned?

Brian Cheney · « **Reply #50 on:** 15 Aug 2010, 01:29 am »

Unless the tweeter has a bad transformer you don't need to replace it. The foam pads are no longer available, we have slotted masks now. These are $12pr plus $3 shipping.

We don't have any faceplates for the ribbon tweeters on hand, unfortunately.

SpeakerDoc · « **Reply #51 on:** 15 Aug 2010, 02:17 am »

Are the slotted masks the one with the black goey stuff on the back?

When I removed the slotted mask, the black fabric covering the tweeter
pole pieces pulled partly off in a few spots, OK I could glue this back, but
some silver coating also pulled off of the pole piece and is now flaking.
I think it is paint, but looks shiny kind of like chrome.

Can the pole pieces be recoated or can I just scrape it all off?

Brian Cheney · « **Reply #52 on:** 15 Aug 2010, 02:20 am »

You may scrape off if you like.

SpeakerDoc · « **Reply #53 on:** 15 Aug 2010, 02:37 am »

And do you reglue the fabric or leave it off?

Brian Cheney · « **Reply #54 on:** 15 Aug 2010, 03:32 am »

Flip a coin.

SpeakerDoc · « **Reply #55 on:** 15 Aug 2010, 01:49 pm »

OK I will rebuild this old tweeter, but they are on sale at PE and I
thought I'd keep this old one as a backup. Is the one from PE the
same as yours or does it require mods?

Brian Cheney · « **Reply #56 on:** 15 Aug 2010, 04:08 pm »

You can use the stock G2si in a pinch. We dehorn and level match the tweeters in pairs, since there is about 6dB variation among stock tweeters.

SpeakerDoc · « **Reply #57 on:** 15 Aug 2010, 11:23 pm »

Thanks again Brian,

I'm redoing the midrange panels in the other box now and am
wondering if you use any chemical treatment on the ring terminal
to mid panel contact. There is what looks like dielectric grease
on these is that what VMPS uses if you don't mind my asking?

Brian Cheney · « **Reply #58 on:** 17 Aug 2010, 02:36 am »

We do not use any such grease, never have. I'd check those panels carefully.

SpeakerDoc · « **Reply #59 on:** 18 Aug 2010, 02:50 am »

I cleaned them all off and it is not difficult to get the compound off.

They seem to measure just fine also.

Thanks again for the info!