Vintage Silvertone speaker capacitor question

[grindfix]

I picked up these speakers before holidays and just now had time to check them out. Both high frequency horns are not producing sound. I opened one cabinet to investigate. 2 caps, HF rheostat and 3 drivers. No inductors. I took AC voltage test on both side of HF cap and it's obviously dead. I get fluctuating voltage on one side and -0- on the other side. I had 3.9uf Solen film cap laying around. Soldered it in place of original 4uf non-polar and horn is on! With one horn and all other drivers working, these speakers are not bad sounding!

My question is: should those old caps be replaced with regular non-polar litycs or litycs, bypassed with small film cap? Or just replace them with films? They would be much bigger and more expensive. There is plenty of room but will going with films sound any better?

Original values are 4uf for HF and 30uf for Mid crossover.
I have 33uf Solen caps and missing another 3.9uf to make a quick decision

 

[grindfix]

Bummer. I opened second cabinet and tested. Horn diaphragm is blown. What are my options aside of finding identical driver? I have 2 Klipsch klf-20 original poly dome diaphragms that measure 8+ohms. Their voice coil fits the groove in the magnet. I can use signal generator to center them without rubbing because alignment and mounting holes do not line-up.
I have 2 Magnavox console horns. I believe they are called Hepner. They have greenish styrofoam cap in the back. Any suggestions?

 

[toxcrusadr]

I'd use the Heppners, they can sound pretty good and seem to be on par with the rest of the system here. But nothing wrong with fiddling with the Klipsches either. You will probably find a difference in output no matter which you use, so it's good you have a treble level control.

Definitely replace those caps. The 4 uf is pretty cheap in a film cap, for the 30 uf I'd use a nonpolar electrolytic due to size and cost of films in that value.

Woofer looks very familiar, maybe a Utah? What are the numbers on the back? If you see a 328 that's Utah.

 

[halkaloogie]

Woofer is an Oxford, and I would guess the others are too. Funny enough I just picked up a pair very similar to those. I've been trying to decide what to do with them.

 

[grindfix]

Heppners have wider horns. They are at work. I’ll post a picture with Heppner and original side by side tomorrow. Problem with going with Klipsch diaphragm is that I’ll have to open up perfectly working original and it will get destroyed. The way it’s constructed, diaphragm is assembled on the motor and coil leads are soldered to terminal plate which is a part of the motor. When horn is separated, diaphragm is stuck to it and coil leads detach from terminals. No way to save it.

Here is the woofer closeup.

 

[toxcrusadr]

Sho 'nuff, 465 = Oxford Speaker Co. of Chicago. I have a pair of those woofers and thought they were Utahs but never looked at the codes. Good to know.

 

[grindfix]

Maggie horns are too big.
I shared my dilemma with one of my crafty employees and with joint effort, looks like we saved the original diaphragm. We tested voice coil and it was still good. Looks like moisture damaged one of the coil wires between phenolic diaphragm and terminal. We soldered short pieces of small electric motor windings because they are coated. Solder joints are sandwiched between phenolic lip of the diaphragm and fiber gasket below it. I used red anaerobic sealer under the diaphragm to seal the magnet groove and keep moisture from damaging solder joints. I used my signal generator after each step to confirm that voice coil or former is not touching the metal. I think it's saved!!

 

[toxcrusadr]

Well done!

 

[grindfix]

Next, after I get horn and capacitors in, I want to experiment with the port tube. My first thought was to just extend it and see if I get more bass. Then I thought that moving that tube to the back of the speaker will get better result against the wall and will be somewhat adjustable with the distance from the wall. Any thoughts?
I know that extending the tube adds bass, meaning that larger tube diameter will likely reduce the bass response, correct?

 

[toxcrusadr]

Well, it all depends on the woofer parameters. It would be best if you could get the T/S parameters for that woofer, which involves either finding someone to test it, or finding the results online, or buying a test rig (about $100). That way you can use an online free design program and optimize the cabinet. Now let me check whether the woofers I have are actually identical. Is the above upside down pic of the numbers from the back of your woofers? If mine are the same driver, I have a Dayton DATS2 gadget and I'd be glad to test mine and post the results.

 

[toxcrusadr]

Basically the way ported enclosures are usually designed is to create a resonance peak just below the resonant frequency (Fs) of the woofer. Usually the response of the driver drops off dramatically below Fs so the cabinet resonance will extend it downward a bit before it drops off. As a result there is only so much you can do with any given woofer because it's limited by its own Fs.

OTOH depending on how old this beast is, it may or may not have been designed using T/S parameters already. Only one way to find out!

 

[grindfix]

Well, it all depends on the woofer parameters. It would be best if you could get the T/S parameters for that woofer, which involves either finding someone to test it, or finding the results online, or buying a test rig (about $100). That way you can use an online free design program and optimize the cabinet. Now let me check whether the woofers I have are actually identical. Is the above upside down pic of the numbers from the back of your woofers? If mine are the same driver, I have a Dayton DATS2 gadget and I'd be glad to test mine and post the results.

It is a picture of my woofer. It posted twice for some reason. Thanks!

 

[toxcrusadr]

Well my pair of woofers look very similar but not quite the same.

Pic swiped off the web of the Utah HS1-C they were used in. They have a 328 code which is Utah. So they are not going to have the same parameters as yours.

 

[bowtie427ss]

Any thoughts?

Damping.

 

[CrazyOldIvan]

I just picked up a pair of the Silvertone 7486. I’m sure they need new capacitors. They don’t sound too bad right now. I have never repaired or restored a vintage speaker so this will be my first attempt. I bought them cheap in case I have a problem I am not out too much. Any advice or direction to recapping would be appreciated. This is my first adventure into vintage electronics.

 

[Drugolf]

I just picked up a pair of the Silvertone 7486. I’m sure they need new capacitors. They don’t sound too bad right now. I have never repaired or restored a vintage speaker so this will be my first attempt. I bought them cheap in case I have a problem I am not out too much. Any advice or direction to recapping would be appreciated. This is my first adventure into vintage electronics.

Should be an easy task. These are usually simple crossovers and many will have a small value cap (likely 4uf) and maybe something larger similar to the OP's above. Order in kind values from Parts Express. If it's a 4uf get this https://www.parts-express.com/Dayton-Audio-DMPC-4.0-4.0uF-250V-Polypropylene-Capacitor-027-421
If there is a larger value cap in there like 3o or 33 or 40 or whatever, get these NPE's but match the value of yours. You can combine a couple (look up caps in parallel) to get to the needed value. Don't worry if you miss the number by a couple. https://www.parts-express.com/speak...zed-electrolytic-capacitors/capacitance/33-uF
Both of those can be installed in either direction so don't worry about any of that.