[knabelmarc]

recently the response seems a little muddy, am thinking due to age the caps could use a mod. I am driving these beasts with an original Threshold S500 firt edition Stasis amp, it alone will reveal deficiencies, and drive these M3's into the stratosphere, any help on cap determination as well as dealer availability would be appreciated.

[Brett Buck]

recently the response seems a little muddy, am thinking due to age the caps could use a mod. I am driving these beasts with an original Threshold S500 firt edition Stasis amp, it alone will reveal deficiencies, and drive these M3's into the stratosphere, any help on cap determination as well as dealer availability would be appreciated.

     To refurbish the speakers, remove the drivers to get at the crossover, read the values off, then go to Mouser or Digi-Key to find the proper value capacitors. I would suggest polyester film caps, assuming they are (as they almost certainly should be) non- polar.  Do not use "audiophile" caps, and I would avoid non-polarized electrolytics, although those will work.

    Before you do that, I would suggest connecting the speakers to a different system and making sure it is not something more likely, like a problem with the amplifier or something else upstream. If something has become "muddy" I would certainly look at the amplifier first, and it's not like Threshold is noted for its reliability (in general). There are far more failure-prone components in the amp than the speakers.

    Brett

[Æ]

I would suggest polyester film caps

How about polypropylene instead? It is usually considered to be a better dielectric.

[Æ]

recently the response seems a little muddy, am thinking due to age the caps could use a mod. I am driving these beasts with an original Threshold S500 firt edition Stasis amp, it alone will reveal deficiencies, and drive these M3's into the stratosphere, any help on cap determination as well as dealer availability would be appreciated.

Mouser and Digi-Key are both good sources for capacitors, but Parts Express sells a wide variety of very decent and affordable capacitors, specifically designed for crossover use.

http://www.parts-express.com/dayton-loudspeaker-precision-1.cfm

http://www.parts-express.com/crossover-capacitor-index.cfm

 

[Æ]

recently the response seems a little muddy, am thinking due to age the caps could use a mod. I am driving these beasts with an original Threshold S500 firt edition Stasis amp, it alone will reveal deficiencies, and drive these M3's into the stratosphere, any help on cap determination as well as dealer availability would be appreciated.

Don't be afraid to consider the possibility that your amp might need a tune up. Also, your connections (interconnects, cables) might be getting tarnished, oxidized.

[Æ]

film caps, assuming they are (as they almost certainly should be) non-polar

OK, film caps don't have, don't need a polarity. Since a capacitor is an AC device then theoretically a capacitor has no polarity. The only reason why electrolytic capacitors are 'polarized' is because the electrolyte needs it.

[Brett Buck]

OK, film caps don't have, don't need a polarity. Since a capacitor is an AC device then theoretically a capacitor has no polarity. The only reason why electrolytic capacitors are 'polarized' is because the electrolyte needs it.

 I understand that perfectly. I am noting that the *originals* should be non-polarized. Some "audiophile" components, however, use electrolytics/tantalum polarized caps in places where they are NOT biased and should in fact be non-polarized.

     Brett

[Æ]

I understand that perfectly. I am noting that the *originals* should be non-polarized. Some "audiophile" components, however, use electrolytics/tantalum polarized caps in places where they are NOT biased and should in fact be non-polarized.

     Brett

Cool, I'm glad that you do, many people don't.
I personally wont use electrolytics in passive crossovers unless I absolutely have no other choice.
Anathema.

[Brett Buck]

Cool, I'm glad that you do, many people don't.
I personally wont use electrolytics in passive crossovers unless I absolutely have no other choice.
Anathema.

   Agreed. That's also why I at least suspect that the problem is not in the crossover. Assuming they did it right and used proper film caps in the first place, from that era, they should have good reliability. NP electrolytics, maybe bad. If they uses polarized caps in an unbiased application, they would likely have blown long ago.

   I would look upstream of the speakers.

   Brett

[Æ]

   Agreed. That's also why I at least suspect that the problem is not in the crossover. Assuming they did it right and used proper film caps in the first place, from that era, they should have good reliability. NP electrolytics, maybe bad. If they uses polarized caps in an unbiased application, they would likely have blown long ago.

   I would look upstream of the speakers.

   Brett

Still though, I'd open up and look inside the loudspeakers just to be sure.

Look inside to see if there are any electrolytic capacitors.

[Brett Buck]

Still though, I'd open up and look inside the loudspeakers just to be sure.

     I doubt you can tell much by just looking. If you are going to actually start testing parts, then it has to be disassembled, so might as well replace the parts anyway.

     BTW , if it is determined to replace the the parts, get a bunch of them of each capacity needed, and then pick those closest to each other. The absolute value of the part doesn't matter but matching them from side to side is pretty important.

     Brett

[Æ]

     I doubt you can tell much by just looking. If you are going to actually start testing parts, then it has to be disassembled, so might as well replace the parts anyway.

     BTW , if it is determined to replace the the parts, get a bunch of them of each capacity needed, and then pick those closest to each other. The absolute value of the part doesn't matter but matching them from side to side is pretty important.

     Brett

Or buy the one percent capacitors they have over at Parts Express.
I amended my previous reply.

[gstraley]

Hi Knabelmarc,
   I did upgrade the caps in a pair of Mirage M3si's. I requested a copy of the schematic from Mirage and they sent it to me. I believe if I look hard enough I can still find a copy of it.
   The biggest problem that I ran into is that the board has around 29 parts on it. It is laid out so that their parts fit close to each other. Most high end caps are generally much larger than the caps that the factory uses. You are gong to find that the caps from Parts Express for the same value as the factory ones are 3 times the size. You will have a fun time trying to shoe horn the caps in. I would also consider changing the resistors to the Mills resistors that Parts Express sells.
  It made a positive change but with all of the crossover parts inside, it will cost you a lot of money. Not sure if it is worth it for those speakers because of all of the parts in the crossover. For it to be the best, you may end up having make up a new X-over board and lay it out with the larger caps. Coils would be a good thing but no room with the stock board.

Gregg

[Brett Buck]

Hi Knabelmarc,
   I did upgrade the caps in a pair of Mirage M3si's. I requested a copy of the schematic from Mirage and they sent it to me. I believe if I look hard enough I can still find a copy of it.
   The biggest problem that I ran into is that the board has around 29 parts on it. It is laid out so that their parts fit close to each other. Most high end caps are generally much larger than the caps that the factory uses. You are gong to find that the caps from Parts Express for the same value as the factory ones are 3 times the size. You will have a fun time trying to shoe horn the caps in. I would also consider changing the resistors to the Mills resistors that Parts Express sells.
  It made a positive change but with all of the crossover parts inside, it will cost you a lot of money. Not sure if it is worth it for those speakers because of all of the parts in the crossover. For it to be the best, you may end up having make up a new X-over board and lay it out with the larger caps. Coils would be a good thing but no room with the stock board.

   As I recall they are second-order filters, not typical first-order, so there are going to be a lot of parts. Twice as many poles and zeros. Using larger parts shouldn't be an issue, the only caps that will be larger are the bizarre "audiophile" caps that shouldn't be used anyway. Conventional caps from today will be no larger than the originals and likely smaller.

     Brett

     

[Æ]

As I recall they are second-order filters, not typical first-order, so there are going to be a lot of parts. Conventional caps from today will be no larger than the originals and likely smaller.

A second order crossover would certainly be expected to have twice as many components as a first order. So yes, more components, but not a lot more components. Seriously, a first order high pass is one (1) capacitor and a second order high pass is one (1) capacitor and one (1) inductor. Since when are two (2) components a LOT of components?

The reason why the M-3 has twenty eight crossover components is because each enclosure has one woofer, two midranges and two tweeters!
The M-3si has twenty three components.

What is conventional? Electrolytics for crossovers are definitely smaller than film for the same uF. But buying new capacitors doesn't automatically mean that they will be smaller than the older capacitors. Their physical size is dependent not only on their capacity but also on the voltage rating.

One trick to cram several axial lead film capacitors onto a small circuit board, is to stand them upright instead of laying them down flat. Another trick is to use both sides of the circuit board.

Going small isn't always a good thing, you give up something. See below, three different inductors of the same mH, yet three different sizes. Why?
Yes, I already know the answer, but I'm posting the picture for illustrative purposes.