Recap Infinity Quantum 3's

Discussion in 'Infinity Loudspeakers' started by micrometer, May 9, 2009.

  1. micrometer

    micrometer chameleon

    Should caps 1 through 5 be replaced in these 32 year old speakers?

    Should item 6 be replaced?

    Any advice is appreciated.


    Attached Files:

  2. Sir.Byrd

    Sir.Byrd Lunatic Member

    Yes, and yes.
    Item 6 is a group of resistors in series to make a higher value, you can duplicate it or replace with a single large resistor.
  3. avguytx

    avguytx AK Subscriber Subscriber

    Not necessarily.

    I'm sitting here listening to a pair I actually own, have refinished the cabinets, have cleaned every connector, and have redone new grills for and they sound outstanding with the "stock" caps and resistors. I actually took measured the stock caps and they were all within a few percent of their rating. Do you have the manual that shows what caps go to what? If you need that, shoot me a PM and I'll email them to you.

    Here's a quick breakdown....

    Group 1 is a 2.2uf + .33uf + .33uf for the Emits hi-pass crossover. All poly caps.

    Group 2 is 3.5uf and a 6.8uf for the dome midrange. All poly caps.

    #3 and 4 are 600uf caps that are for the Watkins DVC woofer. Mine were within 2% of their rating. I wouldn't touch them unless they are way off.

    #5 is a Poly cap used for the "mid bass coupler". Mine was within 3%. Didn't touch it.

    #6 being the resistors that they are, generally don't drift too bad, Replace them if you want to, though. I didn't.

    I cleaned the crud out of the pots which are the main problem with these like many other speakers. That made the biggest difference as they had sporadic control range. IF you want to spend money on replacing caps, I would do it for the Emits, dome mid and MB coupler but would leave the big 600uf caps alone. Unless they are off, of course.

    Just my $.02 from a Quantum 3 owner.
    Last edited: May 9, 2009
  4. bobrown14

    bobrown14 AK Subscriber Subscriber

    How did you take your readings while testing the caps? Did you check ESR for any of the caps?

    You can test capacitance good within spec and the ESR drifts up over time causing the capacitor to act like a resistor which causes degradation in sound quality before the caps drift out of spec for capacitance.

  5. avguytx

    avguytx AK Subscriber Subscriber

    My neighbor is a certified master electrician and has various meters including an ESR meter. (hmm....that sounded like that like from Spicoli in Fast Times at Ridgemont High) All I have are typical DMM's from my car audio days so I asked if he had one...and did. While they may not be perfectly in spec for ESR, they sound fine to me and I'm not ready to lay out the cast for the caps....just yet. But soon most likely. I've changed them on most all of the other speakers I've got, too. I've typically used Solen, Sonicap and the Dayton 1% poly caps.
  6. cdfac

    cdfac AK Subscriber Subscriber

    i found that after i took out the caps from my QLS1s, they also measured pretty close to spec (if anything they were over). i can tell you, however, that the performance after the recap was not pretty close! i'd consider a new air-core inductor for the midrange, too - Madisound makes their own very nice and well priced series. Also look to Madisound to get those resistor values - they have a better selection than PE.
  7. bobrown14

    bobrown14 AK Subscriber Subscriber

    Wouldn't you get more sonic improvement by upgrading the inductor for the low end bass circuit? I'm not an expert but I've been reading about inductors and gains made with upgrades and from what I've read so far it "looks" like more benefit would be had with new air core inductors for the low end and of course I'm sure it would help the mids as well. More bang for the buck the lower the range (or the area where there is the most power). Since mids are the most prevalent listening, common sense say lows and mids. I'm just curious why you dont mention the low end inductor upgrade?

    I recently bought a pair of used crossovers from the bay for the QLS-3 same as the pair I have so I'm gonna take a real close look for upgrades with the spare units and upgrade. I'll still have a all stock crossover if I ever would want to put it back the way it was designed (not that I would stray too far from original spec) but I sure would like to replace those big electrolytic caps with a poly or the like but man the cost... ouch! I doubt the gains would be worth the coin. The bass caps in these speakers are a real testament to just how powerful of an amp you really need to drive these babies. I know Cdfac you've been rebuilding your Infinity QLS-1 - what caps did you use to replace the electrolytic caps with? Next on my list is the crossovers in my QLS-3 so direction would be mucho Gracias!


  8. cdfac

    cdfac AK Subscriber Subscriber

    I guess I left a few things unsaid in my previous post. First of all, you're right in that technically air cores are better than iron cores when push comes to shove, but one issue with swapping out an iron core for an air core is that the air core has a much higher DCR. Luckily, in the case of Quantums and many other Infinities, as long as you're not dealing with the woofers, you should be able to turn up the driver pot enough to compensate (woofers don't have pots). Another issue is size - depending on the brand, I might have to settle for a 4" OD x 1" H 5mh piece (in my case, for the midbass coupler inductor) to replace an iron core that's only ~2" cubed. Then there's expense: the iron cores seem to be about half the price of the air cores. And finally, as you get into the bigger inductor values for lower drivers, you find that it's harder to get odd values in an air core.

    I guess now that I think about it, the only reasons for replacing the original midrange air core for a new one (which is what I was suggesting) is improved geometry and quality/gauge of wire. Probably doesn't make a huge difference in the end, but it isn't very expensive and it helps me sleep better :D In the future if I have a C note burning a hole in my pocket, I might try upgrading my 5mH midbass inductors to air cores, but I'm definitely not going to touch the woofers.

    The OP mentioned that
  9. micrometer

    micrometer chameleon

    Quantum 3 Woofers refoamed, next...

    I've refoamed the woofers and all is well. They're centered and I'm happy with the results.

    I've hooked these up to my Crown amp (200 WPC) using a Sony as the preamp. The sound I'm getting is not spectacular. It's rather dull and the next phase of work would appear to be recapping the crossovers.

    I've seen cdfac's recent list of caps for his QLS 2's. I'll use this as my inventory for the Q 3's.

    Also the top emit of one speaker is producing no sound. I'll have to wait to see the results of the recap. I've also seen prior posts regarding the delicate opening of the emits for repair work. I hope this is not necessary but will have to wait and see. I've recently seen two separate emit sales on *bay. I watched them for pricing in the event I need some in the future.

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