View Full Version : Infinity Quantum 3 BIG cap opinions

12-21-2010, 11:21 AM
I'm getting ready to order capacitors for a lot of my speakers since I have a few weeks till Spring session starts for college. The 3's use (2) 600uf caps in them and I'd like to change them out but obviously, this is a rather large single cap. As you can see in the pictures, each crossover is different as to how they did the 600uf caps. One speaker uses a single "can" capacitor where the other side uses (3) 200uf caps in parallel to attain the value. They do follow the Quantum 3 tech diagram (, though. These caps are on the woofer side of the crossover and I'm wondering if they're really worth the expense of changing out. But, if I did decide to, has anyone else changed them? If so, what did you use?

Interestingly enough, my RS-IIIa's (which I'll order caps for, too) also show in the tech diagram to use (1) 600uf cap on the woofers but there are actually (2) of them on each pair. Weird. In addition, the tech diagram shows different mH values of inductors as what is stated on Infinity's RS-IIIa/b tech diagram (, too. Just shows you that you always want to look at your own speakers to see what's in there before ordering. See picture below.

Here are some pictures to give you an idea of how different they are and how the boards look. Thoughts? Opinions?

Quantum 3 crossover #1

Quantum 3 crossover #2

RS-IIIa crossover

12-21-2010, 11:31 AM
My pair of QLS1's were just like that, one cabinet had the coke cans, the other had the smaller black ones in multiples. I'm still using the coke cans plus a pair I acquired from another AK'er so they'd match. That AK'er used multiples of new non-polar electrolytics in parallel to add up to the proper values. There's no need to go with polys in this particular application.

12-21-2010, 12:46 PM
Definitely change them as those black/red Callins caps are known to explode when they die.

In my RSIIb's I had a single 200uF electrolytic cap on each woofer. Since I built a separate external enclosure for the crossovers I had lots of room, and I put a 200uF Solen polypropylene in the circuit in place of the electrolytic. It's the size of a beer can, however.

12-21-2010, 12:56 PM
the RSIIIA and B had different crossovers, so yours won't match what's on that PDF. and it's worth replacing the electrolytics with new ones, IMO. it's probably a good idea to parallel multiples together to get the right value because modern non-polar electrolytics don't seem to be built to handle the same amount of current as those originals were.

12-21-2010, 01:35 PM
Solen makes 200uf caps but at $52.50 per cap x 6 = $315, I don't see that happening. Now if there was a single 200uf per speaker, I could work with that. When I recapped my Polk SDA SRS II's, they each had 185uf worth of caps on one section and I used a 55uf and 130uf Solen in parallel. Those 130uf's we huge for sure. I googled "600uf can cap" and it came up with these ( big screw terminal radial caps for the low price of $122 each from Digikey. Ugh. Definitely not going to use polys for this situation. Looks like more searching. Thanks for the input, guys.

12-21-2010, 02:08 PM
Not sure the can caps you linked are non-polar, which I'd doubt. Cdfac will know better than I, but as I remember these caps don't have any effect on sound quality in this configuration. They determine the roll-off frequencies for the dual Watkins voicecoils. So NP electrolytics will serve you just as well here.

Here's a link to cdfac's thread on the crossover rebuild:

12-21-2010, 02:14 PM
That's what I was hoping....and was what I was gathering based on how they were placed in the circuit. The hardest part is coming up with a decent amount of voltage in some electrolytics to use in that spot...."if" I replace them.

12-21-2010, 02:18 PM
just get yourself 6 of these:

12-21-2010, 03:33 PM
Those were the exact caps I was looking at.... :) Thanks for the help, all!