Replacing capacitors in Dalquist DQ-10 Speakers

If your capacitors are the original, yellow, metalized Mylar pieces; they don’t need replacement.      They’re not affected, by age.     Of course; there are numerous newer capacitors, that would offer a different presentation.            Whether such a change would be for, "better" or, "worse", would be a matter of your taste.      If you’re happy with your sound, leave them alone.

You might want to see here:

https://community.klipsch.com/index.php?/topic/124268-dahlquist-dq-10/

As for age, no, film caps don't break down.  As for quality... I'd replace the film caps and the resistors.

I'd also carefully replace the electrolytic. That one WILL age, but you have to measure the ESR to avoid causing impedance issues.

I appreciate your responses. 
These are the original capacitors so I think I will just sit tight at this time until I notice some diminished sound quality around a particular frequency range.

I would in fact replace that electrolytic though. You might find it’s better. To be safe, stick to another electrolytic, Belnic, same uF, equal or higher voltage.

+1, on the Mid-Bass' electrolytic, being replaced.     Back when I was upgrading/mirror-imaging the DQ-10s, in my shop; those caps hadn't been compromised yet(it's been a minute).  Easy to forget, how many years it's been(denial, I suppose).

www.regnar.com is what you are looking for. They have everything you need for your DQ-10's

@andyhifiman

I’ve rebuilt a few dq 10’s. I don’t have schematics in front of me, but I recall 8 caps..... C1 in woofer or mid woofer circuit, C2, C3 are in the midrange, C4, C5 & C6 are in the tweeter and C7 & C8 are in the Piezo.
I am going by memory and am most likely off on exact sizes, so take the essence of what I am saying and adjust sizes accordingly.
C1 is large, maybe 80 to 100 mfd, Try to get at least 10 percent of this in a good metalized Polypropylene, So say its 85 mic’s, use 75 mics electrolytic and 10 mic’s of Polyprops.... Basically, the more film the better. The more you go up in frequency, through the tweeter section, the more the caps make a difference. I know the mid has a 16 mfd in there and there are a few 6.5 mfd caps. If you can afford it, I like Janzten Superior Z or Clarity CMR or CSA. If these caps are too high, Look at Janzten Audio cap or Solen PPE.... If these are both too high, go on ebay and find some cheaper caps called Audiophiler caps , they are cheap and still decent.
On the mids and tweeters, try to change all the resistors with metal oxide or metal film resistors, try to get 10 to 12 watt resistors, Look for Mills, Jantzen or Mundorf or again if price is an issue, look for Lynk resistors, if you need lower price, make sure that any wire wound resistors are non inductive....
Lastly, the Piezo. Others will most likely tell you that this is crazy, but I’ve been modifying speakers for 40 years. Take the piezo’s apart. you will see a paper diaphram..... get some latex paint that’s been on the shelf, get and open it carefully, not shaking it up in any way. You will see a milky or clear liquid on top, this is where the latex has separated from the latex, put a thin clear coat on this. It goes a long way to dampening and getting rid of most of the harshness that this tweeter puts out, if possible, coat the rear also. This should all help you end up with a very nice sounding pair of Dalquist, enjoy, Tim

I so greatly appreciate your various responses. I love my system and started building it back in 1974. I currently utilize a Mac MC302 amp, Mac C48 Preamp, Rega P3 table with a Kesiki Purple Heart MC cartridge and a SVS 4000 sub.
Thanks again.

Good afternoon, did anyone hear how Duelund RS Mylar 200Vdc capacitors sound in speakers? Nowhere is there any feedback on how they sound. Maybe someone listened to them in acoustics and can share their impression of how they are compared, for example, with Jensen Aluminum Foil, Paper in Oil or Jupiter Copper Foil Paper or with Duelund more expensive ranges. Play naturally or is there synthetics in the sound? Thanks in advance for any advice.