Trying to explore options for vintage speaker crossover

[topdownsound]

First, my speakers sound great so I'm trying to figure out what to do when they start not sounding great.

I've recently gotten some Pioneer HPM-1100s from a vintage shop. I don't know what, if anything, has been done to the electrolytic capacitors. They look original to me but in very good shape. At some point, though, I'm going to be faced with dealing with them failing. So I'm trying to get some options.

First is simply replacing the capacitors, like for like. The board is small, all the real estate used up. I have three capacitors, 0.47, 3.3 and 6.8. There's a 100 volt marker on the 3.3 that I could see but the others were oriented in a way that I couldn't check them directly but I'm guessing if one is 100v, they all are. Radial, bipolar, through hole type. FINDING replacements is tough. Most I can find are axials, which would mean some foostering around with standing them upright, gluing down, bending one lead down and maybe having to sit the cap on that lead to get everything on the board. On the upside, I like this because the caps I have, if original, are already 44 years old and if I replace them now, in another 44 years I'll be long dead, so it will be someone else's problem to replace again.

Second is to upgrade the caps but staying electrolytic. This is also attractive. Better quality but same size.

Third is to replace with polys. Better quality but the size issue is a problem. I've heard of extension boards or something to offshore the caps nearby but haven't explored that.

Fourth is to replicate the board somehow. I don't know where to begin on that suggestion, which was made on a different site.

Fifth is to maybe ditch the passive altogether and go with a totally new, digital crossover. I have zero clue about this. Some sort of miniDSP?

Am I missing an option? The easiest is option 1 and I'd be absolutely fine with that but I'm having trouble finding the electrolytics. The third option involves size considerations. Fourth sound expensive and the fifth is brand-new territory for me. Any advice about which direction to go in? Thanks!!!

 

[ElJaimito]

Non-polarised elctrolytics as used in crossovers tend to have an extremely extended life. Before considering replacing them, use/borrow a capacitor tester, unsolder one end, and test their characteristics. I have 45 year old NP electrolytics which are still in original spec. Others, of course have failed! IMHO there's an utterly unjustified obsession with "re-capping". Only replace faulty components!

 

[topdownsound]

I will do that! If I can avoid replacing caps, I will.

One thing I was thinking was finding the caps, buying them and putting them away to be used when needed. That way, I could take the time to learn to solder and go with option 1, which is the most straight-forward approach. But finding a source is proving tough.

 

[topdownsound]

Picture of an HPM-1100 crossover, if that helps. I could probably learn to solder well enought to get the two bigger cans out but that itty bitty 0.47one in front would be troublesome, given how squeezed in it is. But if I found some source where I could get the radial nonpolar through hole caps, I'd probably just go that way and call it a day. Digikey and Mouser don't seem to have any that I could find. Maybe I'm not using the site correctly, though.

 

[MaxwellsEq]

Google for something like "MINIATURE TAG STRIP 2 X 18" to practice soldering skills.

 

[GXAlan]

Fifth is to maybe ditch the passive altogether and go with a totally new, digital crossover. I have zero clue about this. Some sort of miniDSP?

The PWR-125 and PWR-250 will do exactly what you want, albeit a high cost for the speakers and the need for another enclosure. You can also find Crown amps with DSP as another example.

 

[Salt]

0.47, 3.3 and 6.8 of foils (WIMA or others) are not that big to not fit the PCB with some bending of the 'feet'; if necassary a bit of wire helps.

 

[mhardy6647]

Neat.
The HPM-1100 is seldom seen and not bad at all -- albeit hardly an ASR kind of loudspeaker.

Ahem. Probably goes without saying, but I have a pair of 'em in the basement.

Photo shows one of the pair being subjected to an intake inspection via CAT scan. Diagnosis: failed woofer surround.


Photo of one of the pair with re-surrounded woofer.

The most important question: have the foam surrounds on the woofers been replaced? The cones of the woofers are, as you probably know, extremely fragile. The surrounds are not exotic (very JBL-esque) but deserve proper replacements, as opposed to inexpensive generics. Proper replacements are available and not outrageously expensive. I successfully refoamed the woofers in mine. It was not difficult at all, but a bit of a white-knuckle experience given the fragility and irreplaceable nature of the cones. Note that the woofer surround is mounted to the rear of the cone.



The woofer is quite nicely made and resembles later TAD (Pioneer's prestige/pro brand) woofers in construction values.



(one woofer after re-surrounding)

Also, are your loudspeakers HPM "supertweeters" working? Their output is virtually ultrasonic, so it can be a bit hard to tell for certain (especially for aged ears like, ahem, mine).

Personally I would seriously consider replacing the NP electrolytics with some sort of non-electrolytic alternative (unless the capacitance value means film replacements are just too big or too expensive); doesn't have to be anything fancy. To the best of my knowledge, NP electrolytics are made out of two regular old electrolytics connected "back to back" (negative to negative). Polarized electrolytics have quite finite lifespans (in terms of maintaining capacitance and/or ESR values). I cannot claim to be a capacitor expert, though -- nor, in full disclosure, have I done anything to the XOs on the pair here.

Other than that, I would not try to re-engineer the XOs.

 

[mhardy6647]

Google for something like "MINIATURE TAG STRIP 2 X 18" to practice soldering skills.

I use things like pegboard to build XOs. I am not exactly an artisan.

N.B. Those "Audio Grade" capacitors are the cheap Bennics sold by PartsExpress under the "Dayton" brand.

 

[restorer-john]

Picture of an HPM-1100 crossover, if that helps.

The two black electros will need to be looked at for sure. They are glued down (all three) and they are notorious at the best of times for leakage. I would heat up the board with a hairdryer/heat gun to soften the glue and desolder and pull off the caps. Inspect, test and/or replace. And when you replace, match the capacitors in each speaker crossover.

 

[ElJaimito]

Just search for non-polarised elctrolytics. I'm in the EU:

Shopping for electrolytic capacitors?

At SoundImports.eu you will find a wide range electrolytic caps by Jantzen Audio and Mundorf!

www.soundimports.eu

 

[ElJaimito]

Neat.
The HPM-1100 is seldom seen and not bad at all -- albeit hardly an ASR kind of loudspeaker.

Ahem. Probably goes without saying, but I have a pair of 'em in the basement.

Photo shows one of the pair being subjected to an intake inspection via CAT scan. Diagnosis: failed woofer surround.

Yep. That's a cat-astrophic failure. Don't use cat-alytic glue to repair it, though. Results would be cat-alyptic (sorry)...

 

[topdownsound]

Wow! Great advice!!

The straight-forward play is to replace like for like. The problem I'm running into is that finding radial through hole bipolars is very difficult. The Nichicon U series would work but the minimum purchase at DigiKey is 2000. I need 2 each of the capacitance values I noted. Others are VDC and I'm not certain that will work as I'm new to this.

So, I'm looking at axial but I have three questions:

1) I've heard of turning an axial on its end and bending down the top wire into one of the holes, then dabbing some electronic RTV silicone to hold the cap in place. Wouldn't that mean the cap is sitting on that wire as it tucks under? Is that a problem? The same problem would arise if I went to a poly. Or would I avoid that by offsetting the cap a bit on that side to expose the hole?

2) I can probably fit two polys for the back 3.3 and the 6.8 but that .47 in the front is a bit dicey. It is pretty squeezed. But as a question that will make an audiophile's hair curl - isn't that tiny guy in the front in charge of filtering for the supertweeter? I can't hear that anyway. What is the downside of ignoring it and letting it eventually fail? Isn't it a high pass filter for the ultrasonic stuff and if that is not passed to the super, then the regular tweeter gets the full megilla. I mean, it is technically a 4 way speaker but functionally, it is a 3 way insofar as perceptible sound ranges. That super crosses at 16K Hz and that's entertaining the dog, not me. Just wondering.

3) A poly cap for the tweeter would likely brighten it and I've read about a resistor in line. Would that go in the segment from the the l-dap to the board or the l-dap to the tweeter? Or does it even matter?

Thank you!!

Seeing what is involved with the active speaker conversion, I'm not up for that. I'll learn to solder instead. And that Crown amp! Yipe!

And yeah, HPM-1100s are probably the red-headed stepchild around here but for me, they are the best speakers I've ever owned so I'm over the moon with them. They are newly foamed and working great. Even the supers - they can make my dog shake his head, anyway!

 

[mhardy6647]

They're not bad sounding at all. A darned sight better than the HPM-100s of the previous "generation".

You don't have to mount the capacitors close to the board. You do want them to be, in some way, securely mounted to something though, not flopping around. Look at the lovely XO I built (earlier post, above) to upgrade a pair of Cambridge SoundWorks Model Six loudspeakers for my daughter over 20 years ago. You don't want any short circuits, of course. If "lead dress" is a concern, slip-on insulation on the leads is fine. You're not building a UHF radio receiver (or transmitter)

 

[topdownsound]

This is very good information! From what I've read, my preference is to use polys and if I can mount them securely, somehow, that's what I want to do. I suppose I could build a mounting board, zip tie and silicone down a sonicap of the correct uF to it, run the leads to the original board. Then mount the outboard to the cabinet in some way.