[HAL]

You might look at Alpha Core air core ribbon inductors.  Like the Alpha Cores in other passive crossovers I have. 
 
I would go with a single large value and a smaller bypass cap for the tweeter circuit.  Sonicaps are very good and they make a platinum bypass cap.  They will match pairs as well.  Also have them in passive crossovers here. 

If you cannot find them, GR Research might be able to help with inductors for the rebuild.

Good luck!

[LosGatosSTI]

Thanks HAL.  Please explain what a "bypass" cap tweeter circuit looks like.  How and where would the big cap and bypass cap be installed based on my photos in the thread?

[HAL]

The same place as the present tweeter capacitors in the crossover, the two caps are in parallel just like I am suggesting. 

The alpha core ribbon inductor would replace the ferrite core coil in the tweeter circuit that presently exists.

This all would be after figuring out the reason for the tweeter melt downs, but as stated most likely the amp.

[Tyson]

In a crossover, a capacitor cuts off the low frequencies, an inductor cuts off the high frequencies, and a resistor lowers the overall output. 

So, a capacitor on the tweeter will cut off the low frequencies (say, everything below 3khz).  Maybe a 5uf capacitor does that.  Many times a manufacturer will use a cheap main 5uf cap and then 'bypass' it with a much smaller, higher quality cap.  This keeps overall costs down, while giving a 'taste' of the sound of the better cap.  Which is what Brian did here.

[jules]

Scott, could I suggest this as a useful guide to understanding and making passive crossovers:

http://sound.whsites.net/lr-passive.htm

If you're DIYing the xover a schematic would seem essential.

There's a lot of useful information on the Elliot site about anything you could possibly want to know about audio electronics.

[LosGatosSTI]

Thanks HAL, Tyson and Jules.

What wire diameter wire inductor should I use here or does it matter?    The wire that Brian used seems pretty small gauge.

Also seems some inductors are ribbon.  What is the best way to solder these into the circuit? 

[LosGatosSTI]

Jules.  I looked at some of Jeff's posts on this site and he seemed to recommend Solen Perfect Lay inductors a while ago...has the consensus changed to Alpha Core or Goertz or Solen now? 

With ZAKski's help I located these on madisound:

Solen 0.22 mH Perfect Lay Inductors 14 AWG
https://www.madisoundspeakerstore.com/solen-14-awg-perfect-lay/solen-0.22-mh-perfect-lay-inductors-14-awg/


Goertz CF.25 (14 AWG) Copper Foil Inductor
https://www.madisoundspeakerstore.com/goertz-14-awg/goertz-cf.25-14-awg-copper-foil-inductor/

[LosGatosSTI]

I read on audiogon that Solen are very hard to use as you need to strip the lacquer off each conductor. 

https://forum.audiogon.com/discussions/alpha-core-or-perfect-lay-inductors-for-upgrading

They go on to say that Goertz are pretty good sounding for higher and mid frequencies.

I haven't heard either so I have no idea.    ZAKski may have the Goertz in his RM40's if I recall a conversation we had last week or so. 

[LosGatosSTI]

Sorry...I figured out that Goertz was same as Alpha-core so no worries.  I will get the Goertz copper foil.

There isn't a lot of room on the crossover board it seems.  I should probably stick with the smallest form factor which would be the 16 gauge size. 

t Is there a compelling reason (sound wise) to go to the largest gauge like the 14 gauge or 12 gauge size at all costs?

16 gauge:  Alpha Core Goertz 0.25mH 16 AWG Copper Foil Inductor
DCR: .120
Diameter: 1.6”
Height: 1.42”
Weight: 0.39 lbs

14 gauge: Alpha Core Goertz 0.25mH 14 AWG Copper Foil Inductor
DCR: 0.076
Diameter: 1.8"
Height: 1.42"
Weight: 0.57 lbs

12 gauge: Alpha Core Goertz 0.25mH 12 AWG Copper Foil Inductor
DCR: .047
Diameter: 2.0”
Height: 2.00”
Weight: 1.09 lb

[jules]

Good idea to replace the iron core inductor with the Alpha core but there's no reason to go with a gauge any thicker than what's in there now. If it's capable of carrying the current delivered to it, that's all you need. If you had a much higher power rated speaker you'd need something more. You could even lose some sound quality by using a larger than needed coil.

You shouldn't have any trouble soldering the ribbon, though if you haven't done it before a little practice would help. I'd suggest you get hold of some Cardas eutectic solder from Michael Percy. It flows well and doesn't require cleaning off excess flux when you've finished.

It's worth spending up on the tweeter cap [and the bypass in parallel with it] partly because it's only a single, not very big cap  and also because our hearing is quite acute in the range of the tweeter [actually from about 200Hz to 3,000Hz give or take a bit at either end]

You are going to have the amp checked aren't you  ?

[LosGatosSTI]

Hi Jules and thanks.  I'll just go with the Alpha Core Goertz 0.25mH 16 AWG Copper Foil inductor then.  I was planning on getting the cardas solder as well. 

So instead of getting quantity two matched 1.5uF Jupiter copper caps (One for each speaker) I should get two pairs of matched 1.0 uF and 0.47 uF jupiter copper caps correct?  Two caps per speaker.

Or do I get a larger cap of some uF rating and use the 1.5 uF Jupiter cap in parallel?  I'm a little confused on this. 



Yes I will get Bryston to take a look at the amp. 

[jules]

When you use caps in this situation, what the smaller cap is doing, is to allow through higher frequencies that the larger cap might not. Like everything else, there's debate about its usefulness, though in some situations people will use two caps in parallel with the large cap, each one being maybe 1/100th of the value of the next highest one. Certainly not needed here!

In this case you need a bypass cap of 1/100th  [or even 1/1000 the value of your 1.5uF Jupiter]  which makes it .015 uF. So you can keep the same value for the 1.5uF cap.

If you find a schematic please post it. Surely VMPS can come up with something since you're an owner?

[Stimpy]

Hi Jules and thanks.  I'll just go with the Alpha Core Goertz 0.25mH 16 AWG Copper Foil inductor then.  I was planning on getting the cardas solder as well. 

So instead of getting quantity two matched 1.5uF Jupiter copper caps (One for each speaker) I should get two pairs of matched 1.0 uF and 0.47 uF jupiter copper caps correct?  Two caps per speaker.

Or do I get a larger cap of some uF rating and use the 1.5 uF Jupiter cap in parallel?  I'm a little confused on this.   

I just looked at the Sonic Craft store, and the only small values Jeff offers in the Jupiter Copper caps are 1.0uF and 2.2uF.  No 0.47uF either.  Jeff does have a 1.5uF cap in the Jupiter VT series, or a 1.5uF Mundorf Supreme Silver/Oil.  So, is Jeff having a custom 1.5uF Jupiter Copper made for you?

http://www.soniccraft.com/index.php/film-capacitors-jupiter-c-301_38

http://www.soniccraft.com/index.php/mundorf-silveroil-c-301_45_46

Also, as to how to configure the capacitor, if you can find a single capacitor, that's best.  Some feel that combined parallel caps can exhibit phase distortion, which can sound like the music has a very faint echo effect.  And as high quality as the Jupiter and Mundorf capacitors are, they probably wouldn't benefit much from a bypass.  Bypass caps are typically used on cheaper caps, to improve their sound.  Also, bypass caps are used to improve the discharge rate of a larger capacitor.  Since you need a 1.5uF value, those would already have a very good discharge rate.  But, Jeff does make his Sonic Craft Platinum bypass caps, if you feel curious?  Though I'd wait until you've listened to the new caps for a good while, to ensure they're completely broken in, before deciding if they'd benefit from the bypass?

http://www.soniccraft.com/index.php/sonicap-platinum-c-301_49_52

Good luck.

Oh yea, I've used Mundorf capacitors.  EVO Oils, Supremes, and Supreme Silver/Oils.  All very good to excellent.  The Supreme Silver/Oils would make an excellent tweeter capacitor.  IMO.

[Stimpy]

If you find a schematic please post it. Surely VMPS can come up with something since you're an owner?

I'm not sure if you are aware of the fact that VMPS, as a company, no longer exists.  Brian Cheney, founder, designer, and owner, passed away in December of 2012.  The company passed away with him. 

[jules]

Yes, sorry, I realize that Brian passed away some time ago but I suppose I was hoping that some of the entities still running the circle, might have access to such a resource. Maybe not?

I guess  the other way of looking at it is, that it should be relatively easy to "back-engineer" from an actual crossover to draw up a schematic. 

[Stimpy]

Yes, sorry, I realize that Brian passed away some time ago but I suppose I was hoping that some of the entities still running the circle, might have access to such a resource. Maybe not?

I guess  the other way of looking at it is, that it should be relatively easy to "back-engineer" from an actual crossover to draw up a schematic.

Yea, I understand.  I wish the Mods did have some type of insider-information.  But, sadly, that isn't the case.  Brian seemed to be pretty much a one man show.  So, whatever proprietary information, that documented what was involved with the design of his speakers, went with him. 

I've been hoping for years, that we could organize a Thread here, and populate it with any official documentation that various owners had.  Sales fliers, schematics, spec sheets, anything, just to try and organize any information that might be helpful to owners, in order to try and keep these speakers up and running!   

[HAL]

The tweeter crossover looks very similar to the QSO-626R kit I have.  Posted that one a long time ago.  Might be worth a search to see if it is around.  If not, will try and find it.

[ZAKski288]

Here’s a simple drawing of the tweeter crossover wiring.

[LosGatosSTI]

Is there a schematic of the RM40 crossover as a whole?