Reference Studio Monitor Crossover Questions

[wwiztab]

I ordered capacitors based on the schematic attached to this thread. I opened it up to start working and things aren't matching up. (Picture attached) The coils are good, but some Cap values are different. Is this normal? It looks like original factory parts and work. Do I use the schematics or replace with exactly what's on the crossovers now? Also on the schematics, if I follow the input - and + , the + input ends up on the - of the tweeter and mid, and the - input ends up on the +. Are these schematics even any good?

 

[goodolpg]

Infinity RSM crossover

wwiztab, I just pulled one of the woofers in my RSM's. My crossover is exactly the same as yours and I know mine is as delivered from the factory as I am the original owner.
So it appears the schematics in the link are NOT CORRECT at least as far as our RSM's are concerned.
I see three silver caps, 125 mfd, 8mfd (trust me as they don't show up well in the photo) and I can't see the #'s on the other but I'm pretty sure it is the same as yours (20mfd).
I'm not sure on how the wiring traces out, maybe you can tell from my picture.
I'm hoping a picture of my crossover appears. I'm not real good at attachments.

 

[slowpat]

In some design, they may reverse the phase on the tweeter and/or midrange, so I wouldn't worry too much about it. You will want to replace the caps as you have them on the crossover board, as manufacturers sometimes change their design during midstream, and the schematic is not always reflected. For the 125mfd, you may need to go electrolytic as they can get expensive with the polypropylene versions. Non-polarized. My second pair of RSM's came with the grey poly woofers waiting for a refoam...I just love them.

 

[goodolpg]

Slowpat, I have been looking at caps online and see many different types. Electrolytic, polypropylene, polarized, non polarized, etc.
Do you know what type the original RSM caps are?
I have no idea which ones to purchase if I do decide to do a recap.
Any suggestions would be appreciated.

 

[glum]

check this link infinity classics ther have most revisons.
My 1.5's have a few.http://www.infinity-classics.de/

 

[slowpat]

Slowpat, I have been looking at caps online and see many different types. Electrolytic, polypropylene, polarized, non polarized, etc.
Do you know what type the original RSM caps are?
I have no idea which ones to purchase if I do decide to do a recap.
Any suggestions would be appreciated.

Most caps used during that vintage were electrolytic, non-polarized. Polarized just means that the (-) end of the lead goes to the (-) on the board. If non-polarized, you can install it either way. Most people agree that using modern poly caps makes them sound better, but as the capacitance value moves up, the more expensive and bigger the capacitor gets. So, depending on your budget, you may have to go with a electrolytic cap in those cases. Another school of thought is to replace electrolytic caps with the same, but modern ones of course.

The path I take is based largely on my budget, so I normally just go for Dayton poly caps from Parts-express, and I have used electrolytic caps from both Parts-Express and Madisound. I think you should get better performance using either ones. Just have fun. Try to recap one speaker first, and do a side by side listening with the original one to see if you even notice anything different. In some cases you don't have a choice - like the pair of KLH Model 12's I had, the caps were so old, there was no signal getting to the drivers, and I had to recap the whole thing. I couldn't do a before/after comparison in that case.

 

[goodolpg]

Thanks for the help slowpat!

 

[wwiztab]

SLOWPAT

As you can see by the picture of mine and the one from goodolpg the large capacitor is different. My RSM's have the clear woofer so I think it's a little newer. Anyway, my large capacitor says: T1 8k 200V, goodlopg says: BEC-4118 8.5 +/- 5%.

So I am assuming that 8K means 8.0uf and 8.5 is 8.5uf. Is that correct? Guess I'll have to send back some capacitors to Parts Express and order different ones.

 

[goodolpg]

I guess I wasn't sure those were caps also.
Wish I retained more of the electrical courses I took 20+ years ago.
That would sure help with the tracking and troubleshooting.
I purchased my RSM's new in Jan. 1983.
Serial #'s A067xxx

 

[slowpat]

SLOWPAT

As you can see by the picture of mine and the one from goodolpg the large capacitor is different. My RSM's have the clear woofer so I think it's a little newer. Anyway, my large capacitor says: T1 8k 200V, goodlopg says: BEC-4118 8.5 +/- 5%.

So I am assuming that 8K means 8.0uf and 8.5 is 8.5uf. Is that correct? Guess I'll have to send back some capacitors to Parts Express and order different ones.

You shouldn't have to swap that one out. Just swap out the three silver electrolytic caps, and you should be golden. For the 125mfd, you may need to get the electrolytic type, and the other two smaller ones, get the poly ones.

 

[goodolpg]

I appreciate the help so far!
I hope I haven't hijacked the op's thread and this info is helpful to him as well as myself.
A couple more questions if I may.
Looking online for caps, does 20mfd = 20uf? The caps in my crossover are labeled as mfd, caps online are listed as uf.
Also, my caps are 100V, I have found some rated at 250V and 400V, are these interchangeable?
Can a 8.2uf cap be sustituted for an 8.0 cap? What is an allowable variance from the specified rating?
Sorry, that's more than a couple questions.
It appears that I need 8uf, 20uf, and 125uf caps to recap my RSM's.

 

[slowpat]

I appreciate the help so far!
I hope I haven't hijacked the op's thread and this info is helpful to him as well as myself.
A couple more questions if I may.
Looking online for caps, does 20mfd = 20uf? The caps in my crossover are labeled as mfd, caps online are listed as uf.
Also, my caps are 100V, I have found some rated at 250V and 400V, are these interchangeable?
Can a 8.2uf cap be sustituted for an 8.0 cap? What is an allowable variance from the specified rating?
Sorry, that's more than a couple questions.
It appears that I need 8uf, 20uf, and 125uf caps to recap my RSM's.

mfd=uf is correct, so you do need the 8uf, 20uf, and 125uf. I don't even see caps rated for 100v anymore, and 250v is perfect, since it can handle more power than 100v. 400v will be wasting your money.

The allowable variance is the tolerance feature that you pay for. 8.2uf to 8.0uf can be satisfied by the 10% tolerance caps, since the variance can be up to 0.8uf. If you go for 1% tolerance caps (a lot more expensive) then, you will need to match it closer. The caps used by Infinity were 10% or more tolerance levels anyway. Also, you can combine smaller values to get to the target value, just install them in parallel (i.e. 2uf + 6uf, and tie each end together before soldering.)

 

[wwiztab]

Thanks Slowpat. Back to PE to order what I really need. Guess I learned my lesson by relying on schematics.

 

[goodolpg]

Thanks slowpat. Your info will help if/when I decide to attempt a recap.
I didn't want to mess with pulling a woofer but now I'm glad I did. I had the speakers
"zero'd in" for the best sound in my room and pulled the woofer while the speaker was upright so as not to change the vertical angle and toe in. Much easier to do it with the speaker laying down!

 

[wwiztab]

Finally recapped them

Here are before and after pictures of the recap. I went ahead and spent the extra $20 for those big 20 uf Solen caps on the mids. I'm glad I did. Wow, mids and highs are crystal clear now. No distortion at louder volume levels either. I'm playing some Denis Solee and it sounds like he's sitting here in front of me. The Pink Panther theme is awesome.

 

[slowpat]

Here are before and after pictures of the recap. I went ahead and spent the extra $20 for those big 20 uf Solen caps on the mids. I'm glad I did. Wow, mids and highs are crystal clear now. No distortion at louder volume levels either. I'm playing some Denis Solee and it sounds like he's sitting here in front of me. The Pink Panther theme is awesome.

Great job! Congrats...they will open up even more after the caps had the chance to break in...

 

[goodolpg]

How difficult was it to do?
I'm a handy kinda guy but have hardly no soldering experience. But if it's not that hard to do I might give it a try.

 

[slowpat]

How difficult was it to do?
I'm a handy kinda guy but have hardly no soldering experience. But if it's not that hard to do I might give it a try.

If you look at his pictures, the wires were mechanically twisted before soldering. So, just make sure you leave enough of the old wire when taking out the old capacitor, put in the new one and twist the two wires together, and you won't even have to solder. You can test it out that way first, and if everything is well, then solder it for the final touch.

 

[goodolpg]

I ordered new capacitors today. 8uf and 20uf Solen poly fastcaps and a 125uf Bennic electrolytic....did not want to pay the $$ for the Solen combo of 125uf.
I bought a solder gun, and ordered a solder sucker.
I feel like the cowardly lion....I just need some courage for when all the parts and pieces get here.
Any help/info for desoldering and soldering will be appreciated.
And yes slowpat, I'll heed your advice to twist and test everything before final assembly.

 

[slowpat]

I ordered new capacitors today. 8uf and 20uf Solen poly fastcaps and a 125uf Bennic electrolytic....did not want to pay the $$ for the Solen combo of 125uf.
I bought a solder gun, and ordered a solder sucker.
I feel like the cowardly lion....I just need some courage for when all the parts and pieces get here.
Any help/info for desoldering and soldering will be appreciated.
And yes slowpat, I'll heed your advice to twist and test everything before final assembly.

Search for "how to solder" on the web, and you should get some pretty good information. Basically, make sure the wires themselves are heated up before you melt the solder onto them to bond them. Soldering is not like gluing two pieces together. The wires themselves need to be hot enough so that the melted solder is "electrically bonded". The twisting of the wires is to "mechanically bond" the connection. Also, buy a few bare alligator clips and clip to the wire close to the capacitor as you solder to draw away the heat.

You may want to take out a crossover from an old speaker and do a test run with that until you fill comfortable. And don't worry about messing anything up, as you can always redo it. Just relax, and take your time, and don't burn yourself.