Recap Your Speakers Like a Boss, Part 1

Hi all,
my Technics SB-A13 3-way speakers are acting strange, at lower volumes the tweeter won't work, unless I increase the volume. Once, increased the volume and lowered back, they work fine.
I suspect the capacitors are dying...any thoughts?

The capacitors that I observed, have unusual marking "50Y1R5K" and also NP 85°C 9305 M07, I tried searching the web to identify what that means so I could order replacement, but cannot find any relevant info except of NP=non polar and obvious 85 deg. Celsius. Any suggestions are welcome!
 
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Quick question. Did you test the crossovers before recapping? I just tested my old Klipsch KG4s with a tone generator app and discovered the crossover seems to be working perfectly. The horn tweeters cut in at exactly 1200 Hz. Anyone know what I am missing here?
 
I suspect the capacitors are dying...any thoughts?

Sounds more like the level pot is flaky.

I just tested my old Klipsch KG4s


The KG4 used 2 film caps and a non-polar electrolytic. The film caps are unlikely to be bad, the electrolytic may have drifted off value or gone high ESR. If that one goes, you'll get some more midrange through the woofer than you ought to, which makes the mids a bit too much. Having replaced mine with fancy caps that I got a good deal on, honestly if I had to do another KG4 I'd swap the electrolytic and call it a day. It did make a little bit of difference, mostly smoothing out the mids. The only cap that tested funny was that electrolytic.

Some speakers use a lot of electrolytic caps though, and they don't age all that well. High value or high ESR will either mess with your crossover points or speaker output levels.
 
That makes sense. Is the crossover a three-wayor two-way? Forgive my ignorance, but I actually don't know where mid-range stops and woofer frequencies start. My KG4s have two identical 8” cone drivers—I assumed these were combination woofers and mid-range and everything above 1200 Hz went through the horn. At some frequency do the 8” drivers stop being fed a signal? Could you shed some light on the design?
 
Its a 2 way, the woofer has a low pass and the horn has a high pass. The two woofers are wired in parallel, they don't get different frequencies. Not precisely sure of the crossover points either but if your tweeter is coming in around 1200, that sounds reasonable. Generally the woofers start to go away near the same point the tweeter picks up so you don't get a huge amount of overlap.

Crossovers have a slope. Beyond a certain frequency, the output tapers off. Exactly how fast it drops depends on the design of the crossover. The electrolytic cap in the KG4 has a lot of effect on how fast the woofers stop responding, so if its open or off value the woofers will try to reproduce frequencies higher than they ought to. That plus the output of the horn makes the midrange overly loud.
 
I understand. I think I will replace the electrolytics—the woofers/midrange do overlap the tweeters way, way up the frequency spectrum.
 
Trying to understand what’s important so i know if I should replace the electrolytic capacitor with and electrolytic one? I understand the replacement must have the same capacitance and ESR, but I often wonder if there is a missing property(s) here—such as the time it takes the capacitor to charge and discharge. Gadget 73, you seem to have tremendous knowledge here, so I thought I’d ask.
 
Excellent, I've fooled another one.

Honestly I replaced mine with film. Usually you just need to match it for value and minimum voltage, as well as whether its polarized or not. This one happens to be a non-polar, so if you're replacing it you want another non-polar. Matching the physical size can also be useful, I don't seem to remember a bunch of extra space on that board to accommodate a fat cap or one with different lead spacing.

Film caps also work fine, they're just bigger and you'll need to figure out how to support them. Mine have zip ties holding them in place. Its not particularly pretty but it works.
 
Super thread WWJones! Thanks a lot for sharing.
Will start a recap soon, still I've got a "first timer" question..
Q: what about the red thingies (resistors??) which also look a bit old, do I need to replace them as well? Filter comes from one of my Wharfedale E-30 cabinets.
Thank you all in advance for your kind assistance.

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Killer Tutorial!!!

I happen to have a pair of Nova's so this is a complete 1-1 for me which will be very confidence inspiring for future re-caps.. Cant wait to order the parts and do this for better sound as well as the learning exp.
 
Hi folks,

After stumbling on this fantastic post, a few weeks ago, I decided to give a shot at re-capping my set of Sansui SP-2500X which I found on the curb last summer. So, I went shopping on Parts Express and purchased the same non-polar capacitors as @Wigwam Jones used in his tutorial (different values, of course). Below is a before & after of the right crossover that I did a few hours ago. Some of the wood came with the old glue but I'm pleased with the result. The sound is noticeably better, there's way less echo in it and I can clearly hear the difference when rotating the crossover selector knob from Soft to Natural to Clear.

Note: For the 2nd crossover, instead of giving myself a hard time removing the old caps, I'll simply free them by cutting their wrappings and trimming the leftovers.

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