Am I missing something?

[mccalljd]

I recently replaced the mid-ranges and tweeters in my 40 year-old speakers. Each box had a woofer, two mid-ranges, and three tweeters, all 8 ohms. Each of the mid-ranges and tweeters had their own simple crossover capacitor in series with the speaker and all of them were paralleled off the positive and negative terminal on the woofer. The original box they came in listed the crossovers at 600 and 1500 Hz. At the time, the original capacitors had a thick plastic coating on them which made it impossible to see the rating for them and I was afraid to try and cut it off without ruining them. When I re-capped the speakers, I went by the box listing but had to raise the crossover frequencies for both mid-range and tweeters to better match the range of the replacement speakers so I went with 25s on the mid-ranges, and 10 uf caps on the tweeters and which should have put the crossovers about 800 and 2000 Hz. Yesterday I got bold an figured since the new caps were working fairly well (though I have some issues with the sound I'm getting out of the speakers now) I would try to peel the plastic off the original capacitors and see what their values were. When I pulled the plastic loose, I discovered they were 4.7 uf on the tweeters and 14 uf on the mid-ranges, which should put the crossovers at about 2000 and 4000 Hz (approx.), way higher than the box listing. Am I missing something or are the frequencies listed on the box totally incorrect? I am thinking of re-capping again to get closer to what I think the originals should be (which would still work well, in theory, with the specs on the replacement speakers. The way they are hooked up in this case, shouldn't alter the crossover points on the capacitors, should it? Since each has its own cap in series with the driver and the drivers are paralleled, the capacitance values should remain the same, right?

 

[StimpyWan]

Out of curiosity, what are the speakers in question? And while I can understand the desire and need to recap, why the driver upgrades? Also, all 1st order crossovers? No inductors on the tweeters or mids?

As to what value replacement caps to use, if you liked the stock sound of the speakers, I'd probably recommend changing back to the original values. But, with new tweeters and mids, the resistance at least, of the new drivers, has to match the stock drivers, for the original cap values to work. Any changes in resistance between old and new, will cause crossover frequency shifts. Different sensitivities between old and new will shift the tonal balance of the speakers as well.

If me, I'd want to pick up a bunch of cheap NPE caps, of various values, and plan on experimenting, to see if you can hit on a combination that you like, with the replacement drivers. I'd get some low value resistors as well, maybe 0.2, 0.4, 0.6, 0.8, and 1.0 ohms, to wire in series, to adjust balance. Once you hit a sweet spot, you could then try some poly caps, if you want to go that route? But, you'd have to play with resistors again, to compensate for the differences in ESR, between NPE and poly.

Good luck.

 

[mccalljd]

Out of curiosity, what are the speakers in question? And while I can understand the desire and need to recap, why the driver upgrades? Also, all 1st order crossovers? No inductors on the tweeters or mids?

As to what value replacement caps to use, if you liked the stock sound of the speakers, I'd probably recommend changing back to the original values. But, with new tweeters and mids, the resistance at least, of the new drivers, has to match the stock drivers, for the original cap values to work. Any changes in resistance between old and new, will cause crossover frequency shifts. Different sensitivities between old and new will shift the tonal balance of the speakers as well.

If me, I'd want to pick up a bunch of cheap NPE caps, of various values, and plan on experimenting, to see if you can hit on a combination that you like, with the replacement drivers. I'd get some low value resistors as well, maybe 0.2, 0.4, 0.6, 0.8, and 1.0 ohms, to wire in series, to adjust balance. Once you hit a sweet spot, you could then try some poly caps, if you want to go that route? But, you'd have to play with resistors again, to compensate for the differences in ESR, between NPE and poly.

Good luck.

These are some old Sonic speakers (supposedly white van, but terrific sound, even beter than the Cerwin Vegas I had). Over the years, my kids managed to poke some holes in the original drivers even through the grill cloth, hence the upgrades to the Dynavox Phenolic ring tweeters (4.25 Round 6 oz 8ohm 3/4" VC Phenolic Ring Tweeter, similar to the originals) and some GRS 5SBM-8 5" sealed back midranges from PE. No inductors on the tweeters and mids. The speakers as they originally were, were the best sounding speakers I ever had and if I could duplicate that sound, I would be quite happy. As it is now, I think I am getting a steep drop off at around 800 Hz and then it rebounds quickly.. Spending that amount of effort to solder and unsolder and reassemble using different caps and resistors seems rather daunting for someone of my general laziness and inexperience with tweaking speakers.

 

[StimpyWan]

Going from a 14uF cap to a 24uF cap, would cause a fairly large frequency shift. That could definitely be causing the imbalance you're hearing. Since the GRS 5SBM-8 is rated from 600 Hz to 10 KHz, there's no reason you couldn't drop back to the 14uF cap, for the mid high-pass, to see if that improves things.