Pioneer CS-33A Audio Speakers - Capacitor Replacmant

[sean0118]

Hi all,

I'm re-capping my set of Pioneer CS-33A speakers because one of the 50 year old Elna CE-BP axial caps has exploded (I think before I got it but only just removed the cover).

They are both part of the low and high pass filters (schematic below).

The Elna CE-BP series are bipolar electrolytics, but I'm thinking modern film caps might be better? At least for the 4uF? They should be a lot longer life, lower distortions etc, but just wondering if the lower ESR could cause some nasty resonances??

Thoughts? 

[Jeff eelcr]

Could be age or overvoltage. Try the caps you want to and see how they sound to you which is what matters. If you decide to make them out of electrolitic capacitors try to get values close or same as to what was there.
Jeff 

[CaptDon]

Buy good quality N.P. (non-polar) capacitors. Don't try the 'back to back 8uf polar = 4uf non-polar'. That trick doesn't work in the real world. I am surprised the cap blew before the woofer would have been fried. With extremely high power at very low frequencies the capacitor would look like an open circuit and not have much circulating current, and with enough power at the mid-low frequencies to blow up the capacitor I would have expected the woofer voice coil to also be damaged. I use a lot of the 63volt N.P. mylar capacitors for my passive crossovers between the mid-high and high horns in my front-of-house system. The caps are yellow in color. My F.O.H. is tri-amped with Low and Mids having their own amplifiers and a three way electronic crossover. The mid high horns and high horns are powered from one amplifier also but have a passive crossover within the horn cabinet which kind of makes my system 4-way.

[sean0118]

Thanks all.

I am surprised the cap blew before the woofer would have been fried. With extremely high power at very low frequencies the capacitor would look like an open circuit and not have much circulating current, and with enough power at the mid-low frequencies to blow up the capacitor I would have expected the woofer voice coil to also be damaged.

That's a good point actually, I noticed the woofer on that side does look a bit different, maybe it is damaged. I've had them in storage but they sounded okay to me when I last used them, but that doesn't mean the woofer is working. 

I picked them up off the street so don't know their history...

[andy3055]

That woofer cone must be stuck. Unless some one did some weird thing, some of these old speakers had the glue holding the magnet/pole pieces (or rings) failing and the center pole wold slide to one side locking up the voice coil.

Always use Non polar caps in the cross-overs.

[floobydust]

I would use film capacitors, they are superior to electrolytics in loudspeaker crossover use. Nothing to dry out, handle AC and ESR is not important because it's tiny compared to the driver's.
If that one cap exploded the driver would have seen some surges and might be damaged. It prob. took out the power amp for revenge. To play around with the woofer just connect a 1.5V AA battery (both polarities) and see how it moves. The surround looks crinkled and I have used steam to fix that.

[CaptDon]

Gently see if the cone moves with only minor stiffness. Do both woofers seem to move the same? One thing that happens (real common on Crate guitar amps) is a shorted output transistor putting relatively high D.C. voltage on the voice coil and also over-volting the crossover capacitors and blowing them up, which then usually takes out the tweeter. You did say however that these use to work, so probably old age and ESR caused the cap to blow.

[sean0118]

Well the good news is I don't need to source film capacitors anymore...  the bad news is the woofers in both are blown (coils open circuit)

I picked these up off the street and remember thinking they lacked bass and must be designed for jazz (they would have been only playing through the tweeters). I only used them for a bit then put them in storage. 

Explains why these were thrown out initially. I'm guessing most people would just replace the woofers? Rewinding the speaker coils would be a fairly involved process right?

[m3vuv]

May be worth checking the thin braided flexible wires from the voice coils to the solder terminals,ive seen that a few times where they were broken on speakers that had been big time over powered !

[Gyro]

There wasn't an amplifier lying in the street too was there? That left hand speaker definitely looks as if the amplifier suffered an output transistor failure. The output pegging to the 60-80V supply rail would account for the distorted suspension (voice coil jamming at the end of the magnetic gap), the open voice coil, and the exploded 50V cap. The o/c on the other speaker was probably abuse at the same time.

I suspect that the timeline was something like this... Volume cranked all the way up, amplifier overheated at high power, excessive power blew one speaker, then the output stage of the other channel blew, with the catastrophic damage to the left hand speaker.

Something tells me the parents were away!

[andy3055]

Well the good news is I don't need to source film capacitors anymore...  the bad news is the woofers in both are blown (coils open circuit)

I picked these up off the street and remember thinking they lacked bass and must be designed for jazz (they would have been only playing through the tweeters). I only used them for a bit then put them in storage. 

Explains why these were thrown out initially. I'm guessing most people would just replace the woofers? Rewinding the speaker coils would be a fairly involved process right?

Ah! Rewinding those voice coils is my specialty.  But then you are too far for it to be economical! 

[Stray Electron]

  I have a pair of those speakers!  My dad bought them in 1972 and they haven't been used in the last 10 or 12 years but they always sounded great.  <https://www.hifiengine.com/manual_library/pioneer/cs-33a.shtml>

[sean0118]

May be worth checking the thin braided flexible wires from the voice coils to the solder terminals,ive seen that a few times where they were broken on speakers that had been big time over powered !

Thanks, I checked this on both of them, but they are okay unfortunately, seems the coils themselves must be open. 

Ah! Rewinding those voice coils is my specialty.  But then you are too far for it to be economical! 

I would be tempted to give it a go myself, but I'm moving house soon, so I'll probably just list them for sale as is. I guess if they don't sell I might have a go eventually.

  I have a pair of those speakers!  My dad bought them in 1972 and they haven't been used in the last 10 or 12 years but they always sounded great.  <https://www.hifiengine.com/manual_library/pioneer/cs-33a.shtml>

Look after them, I think they are getting quite sort after! 

[CaptDon]

Andy3055, Can you rebuild Peavey Scorpion 8 ohm 10 inch speakers?? SP-10825 I believe is the original part number. Peavey still makes the 12" and 15" but dropped the 10". With Scorpions and Black Widows the entire basket comes off of the magnet with three bolts. I have a 10" Scorpion with an intermittent voice coil. I took it apart and soldered the fine V.C. wires at the start and finish of the winding. I secured with a tiny drop of super glue. It has been playing (used in a stage monitor cabinet) but I fear it will crap out again. Replacement baskets when found on Ebay are around 50$ to 75$.

[andy3055]

It can be done but how can you get it to me and back to you? Cost of shipping will be high isn't it?

[CaptDon]

Used to be a guy in York Pa and a guy near Lebanon Pa (Dave Mueller) and they did all my work. I could drive there. That was almost a lifetime ago when you could get a $150.00+ JBL 12" or 15" reconed for about $25 to $30. Now we have speakers like the Gauss KiloMax that can survive being plugged into the 120vac wall outlet!! You have to be a magician to blow up some of what is out there today!!