RSIIIA Crossover assistance please.

INeedInfo

New Member
Hi guys, I'm new here, hoping I can learn something.

I just acquired a set of RSIIIa's in kind of rough shape that I am trying to get back to spec. The cabinets are rough but I'm more concerned with the audio :)

I have replaced both emit tweeters and need to replace a woofer that someone reconed in paper.

It looks like the crossovers are all original and I'm trying to make list for the caps. What I can see in there are

"600mfd, 100v, NPE-RAD, 200-0030",
"16mfd, 100v, NPE-AX, 200-1221"
"6.8mfd 100v, NPE-AX, 200-0085"

Apparent from the Schematic I missed the 5uf. .

I went to madisound.com and came up with this list

(3) Bennic 200 mfd Non-Polar Electrolytic Capacitor 100V

Carli MET 4.7 mfd Non-Polar Mylar Capacitor 150V

Solen PB 7 mfd Metalized Polypropylene Fast Capacitor 400V

I'm not sure where to go with the 16.8, up to 18 or down to 15, I can't seem to find anything close or a 17. I'm not sure where to go with that.

Do the ones I selected look like they would work? I could use all the help I can get, if you didn't notice I'm really new at this.

Thank you very much,

Jon
 
you need 1200 uF altogether for the bass section...

here is the scheme, makes it easier

just refurbed a pair of my own...good luck, great speakers...

 
Here is what mine looked like at the end...Amoung other things I also replaced the input spring clips with heavy duty binding posts... I did away with the protection on the mids and tweets...My days of jamming Master of Puppets at 3:00 are behind me...

 
BK, Thank you, that's very helpful but a bit confusing.

It looks like there is double the woofer capstance(?) on the schematic you have as the Infinity one shows 600mf.

Is there a reason for that and what affect does the extra capstance have on the woofer? I'm completely new to this and am not sure what effect the capaciters really even have.
 
nope its 1200....nothing added...the stock crossover has 2 -600 uF non polar cans to get to 1200 uF....I used 3 - 400uf caps to get there...

componants have changed a lot since these were built...but the values need to stay the same or as close as possible for it to work as intended...
 
I just recapped my RS IIIa's...
From the Madisound packing list.
+/- $80

Bennic 200 mfd Non-Polar Electrolytic Capacitor 100V x2

Bennic 1000 mfd Non-Polar Electrolytic Capacitor 100V x2

Solen PB 6.8 mfd Metalized Polypropylene Fast Capacitor 400V x2

Solen PB 7 mfd Metalized Polypropylene Fast Capacitor 400V x2

Solen PB 15 mfd Metalized Polypropylene Fast Capacitor 400V x2

Solen PB 18 mfd Metalized Polypropylene Fast Capacitor 400V x2
 
Here's a good basic page on what components do in crossovers.

http://hyperphysics.phy-astr.gsu.edu/hbase/audio/cross.html

Basically a cap will pass frequencies above a certain frequency depending upon its value. So a cap is in series with the tweeter to allow treble through.

Inductors do the opposite, allow frequencies below a certain point. So you see one in series with the woofer.

The midrange often has a cap of a larger value than the tweeter to let lower frequencies into the mid.

If you add an inductor to 'ground' after the tweeter cap, it will increase the slope of the cutoff (becomes a 2d order crossover). Similarly if you add a cap to the woofer circuit after the inductor.

This particular speaker is a bit unusual having a huge cap as the first component in the woofer circuit. It also has additional caps and inductors, which basically contour the signal to each driver by emphasizing or de-emphasizing some part of the spectrum. This compensates for driver characteristics to get a more flat response across the whole spectrum.

That's the short version anyway. :D
 
I just recapped my RS IIIa's...
From the Madisound packing list.
+/- $80

Bennic 200 mfd Non-Polar Electrolytic Capacitor 100V x2

Bennic 1000 mfd Non-Polar Electrolytic Capacitor 100V x2

If the values are that far apart won't the 200 act like a bypass cap because it will power up much quicker than the 1000...?
 
OK, I went over the list and started figuring out what I needed then I realized that the listed schematic has different specs for the resistors also.

This is currently what is in my system now (From what I understand this may be one of the few times Infinity matched specs on these)

RSIIIa_zpsa52ac70e.jpg


So if I don't want to rebuild the entire crossover should I just stay with what I have or would the 1200uf still better?
 
Here is what mine looked like at the end...Amoung other things I also replaced the input spring clips with heavy duty binding posts...

How did you get the crossover board out? Mine are glued in, hard. There is absolutely no pliability in whatever glue was used.
 
nope its 1200....nothing added...the stock crossover has 2 -600 uF non polar cans to get to 1200 uF....I used 3 - 400uf caps to get there...

componants have changed a lot since these were built...but the values need to stay the same or as close as possible for it to work as intended...


OK, I went over the list and started figuring out what I needed then I realized that the listed schematic has different specs for the resistors also.

This is currently what is in my system now (From what I understand this may be one of the few times Infinity matched specs on these)

RSIIIa_zpsa52ac70e.jpg


So if I don't want to rebuild the entire crossover should I just stay with what I have or would the 1200uf still better?

Sure looks like the published schematic has a 600 uf cap not a 1200. If all else fails I replace whatever is IN there unless I have a compelling reason not to.

If the values are that far apart won't the 200 act like a bypass cap because it will power up much quicker than the 1000...?

I think I know what you're saying but the answer is over my head. :scratch2:
 
the hand drawn schematics are the original infinity documents. the ones with the NY address are HK's after-the-fact schematics and are frequently wrong (such as calling the RS IIIa/b a 2-way speaker).





.
 
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Hi folks, this has been covered many times....

The one BKphoto posted is for a later model -IIIa; the one from the NY address is a -IIIb, despite the title. Subtle changes in crossover networks.

G~
 
Do not go by those schems, they are vauge...the one i posted is the right one....also you really don't need one, just replace value for value....but no way is the bass side 600uF....Its 1200 uF
 
How did you get the crossover board out? Mine are glued in, hard. There is absolutely no pliability in whatever glue was used.

they are also screwed in, you need to take the scews out then use a wide chisel and run along the outside and it will come right off...
 
OK, I learned something new today. 1st, I'm an idiot who talks to soon. I went to pull up a pic for Karl of the crossover board and took a better look. Yeah, I'm completely wrong. It looks like there are two 600uf's in there. I'm at work now so I'll have to try and get a better look when I get home. I'm glad I didn't order anything yet.

Karl, my crossover unscrews from the back and everything is glued to that panel. It looks like it's going to be a royal pain to get the caps off though.

CAM00140_zps8bae8c53.jpg
 
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they are also screwed in, you need to take the scews out then use a wide chisel and run along the outside and it will come right off...

Screws were out, and tried prying with a 4 inch wide stiff putty knife, I felt I was at the point of breaking the board before I stopped, actually did have a small chip.

IneedInfo: You have a different design, the easy one. Later/earlier, I forget which, the ability to access the board from the back of the speaker dissapeared. Forget which came first, but mine only access is through the woofer holes, screwed and glued from inside.
 
Screws were out, and tried prying with a 4 inch wide stiff putty knife, I felt I was at the point of breaking the board before I stopped, actually did have a small chip.

I wonder if a heat gun would soften it up enough to get it open without damaging anything.
 
ahhh, i see you have to use a pair of needle nose pliers and pull out all the staples...then pry off some of the caps...looks odd, is that the back of the cabinet...?

must be an earlier model..
 
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