OT: Vintage Loudspeaker Refurbishment

[oliver1850]

I have pair of 12" four way 1970s vintage Pioneer speakers with really nice walnut cabinets. They have two sealed back mid range drivers, two 2" cone tweeters, and a horn super tweeter in each cabinet. Both woofers and both super tweeters are working. The woofers have cloth surrounds and seem to be in good shape. There are issues with the crossover as there is no output to either pair of tweeters and one pair of midrange drivers. The crossovers have rotary level controls for the midrange and tweeters. Rotating them doesn't produce any crackling noise but I haven't tried to determine if they are functional.

What's the best approach to make them functional again? I'd just like reasonable response and clean sound. If they end up needing some frequency manipulation I have an equalizer. I don't know anything about analyzing the crossover problems but assume it's a matter of replacing capacitors and resistors. Parts Express has midrange drivers that will fit in the cabinets and I would guess I can find tweeters. Should I try to repair the crossovers or would it make more sense to buy complete three way crossovers from Parts Express? I'm not sure that they sell a four way crossover. That might mean either running the same frequencies to both tweeter and super tweeter or choosing a wider range replacement tweeter and eliminating the super tweeter.

[Ken Robb]

My personal opinion is that I never heard a Japanese speaker from the 1970s that I liked. I liked my Japanese amplifiers with American or British speakers. Of course it was all in the ears of the beholder.

[oliver1850]

I generally like speakers that will play loud with a modest amplifier. Think Klipsch, Cerwin Vega, JBL. I have multiple pairs of all three. The main attraction with the Pioneers is the cabinets. To get a real walnut cabinet currently from Klipsch, I think the entry point is the Heresy at over $2000.

[dgauthier]

Originally Posted by oliver1850

(...) What's the best approach to make them functional again? (...)

Making the speakers work again is comparable to building DIY speakers. Can you solder? Can you use a meter? Can you understand the specs printed on electronic parts? If they were mine and I felt like doing it, I would attempt to restore them part-for-part.

The crossovers can be rebuilt to be as good as new and the process is straightforward. The biggest challenge will be ensuring all the speaker drivers work. After 50 years the flexible paper, cloth, and rubber parts can deteriorate, and exact or similar replacement drivers can be difficult or impossible to obtain.

Remove all the speakers from the cabinets and visually inspect the cones and spiders for signs of decomposition. For the mids and tweeters that aren't producing sound, hook up a low level audio source to them and see if they actually work without the crossovers. Keep the levels very low to avoid frying anything. You just want to confirm the drivers produce sound.

If all your drivers are still in good shape and working, you might be in luck. (Be aware, though, that once you start running those old drivers again, they could start to fall apart with all the vibrations.)

If some of the drivers are decomposing or not working you can try searching on-line for identical or nearly identical replacements. There might be information printed on the drivers that will help with this. If you're not satisfied with what you find at this point you can abandon the project and you won't have spent any money.

You don't need to bother diagnosing what's wrong with the crossovers. It's been 50 years, so rebuild the crossovers with identically specced new components. The upside is it won't cost an arm and a leg and identical components are readily available so it's virtually guaranteed to work. The original circuit boards are most likely perfectly fine and can be reused. (If you can use a meter you can check if the circuit board traces still have continuity.) If you purchase high quality, high tolerance replacement parts, the crossovers will work at least as well and probably better than the originals.

Again, though, it's been 50 friggin' years. You have to decide if the payoff is worth the time and trouble.

[Peter P.]

Get a voltmeter. Disconnect the leads from each driver, one at a time so you don't confuse things, and label the wire and driver as to which lead is + and -. If you're lucky they'll be color coded to help with identification.
You could actually remove all the drivers from both speakers after you do the +/- and color code thing, and label each driver whether it was removed from the left or right speaker. Label the cabinets as well to avoid confusion.

Measure the resistance at each driver's terminals and write them down. Again if you're lucky, the nominal number will be stamped on the back of the driver. A variation of 1 or 2 ohms is common. No reading at all-the driver is blown open. Very low resistance i.e., 2 ohms or less; the driver is bad.

You can compare the left speaker to the right. That will give you a clue as to whether one driver is bad vs. the other driver.

Or let's say the tweeter in one speaker is dead and you don't know what's wrong. Take the tweeter in the working speaker and connect it to the suspect speaker's wiring. Whether the swap works or not will tell you if you have a bad tweeter or something else upstream from the tweeter.

Chart your results and report back. Then we'll go into checking the crossovers and potentiometers.

[Ken Robb]

Originally Posted by Peter P.

Get a voltmeter. Disconnect the leads from each driver, one at a time so you don't confuse things, and label the wire and driver as to which lead is + and -. If you're lucky they'll be color coded to help with identification.
You could actually remove all the drivers from both speakers after you do the +/- and color code thing, and label each driver whether it was removed from the left or right speaker. Label the cabinets as well to avoid confusion.

Measure the resistance at each driver's terminals and write them down. Again if you're lucky, the nominal number will be stamped on the back of the driver. A variation of 1 or 2 ohms is common. No reading at all-the driver is blown open. Very low resistance i.e., 2 ohms or less; the driver is bad.

You can compare the left speaker to the right. That will give you a clue as to whether one driver is bad vs. the other driver.

Or let's say the tweeter in one speaker is dead and you don't know what's wrong. Take the tweeter in the working speaker and connect it to the suspect speaker's wiring. Whether the swap works or not will tell you if you have a bad tweeter or something else upstream from the tweeter.

Chart your results and report back. Then we'll go into checking the crossovers and potentiometers.

I understand no reading=blown speaker/open voice coil but how does a low reading=bad driver?

[benb]

Do they make vintage voiced Hi-Fi speakers?

I know that doesn't fit with the industry practice of always declaring the newest & most expensive thing as a huge improvement even if no one can actually hear it but it's still surprising.

Musical instrument amps/loudspeakers/cabinets are still completely obsessed with recreating vintage spec speakers and the sounds they produced. But it is a little different because those speakers are almost never intended to produce a full range and full frequency response. The whole thing is incredibly confusing.

Rebuilding a speaker or replacing components on an ancient crossover PCB sounds like diminishing returns, I'd be looking at replacing with new stuff if possible. They gotta make crossovers with adjustments on them right?

How complex is a crossover though? Are we talking ten components or something?

[dgauthier]

Originally Posted by benb

(...) How complex is a crossover though? Are we talking ten components or something?

Probably. Not too different from this, I'd imagine:
https://www.ebay.com/itm/133747950341

I wish oliver1850 posted some photos (hint hint).

[benb]

Okay so exceedingly simple with maybe some Caps you could shock yourself on, but probably not high enough voltage to get really hurt?

[dgauthier]

There's no DC in a crossover circuit, so unlike a power supply the caps don't hold a charge. If in doubt enlist the help of a family member...

[C40_guy]

You're considering a lot of effort to put into a pair of speakers. Those speakers were originally designed to accompany the electronics manufactured by an electronics company. Allowed the company to sell an "all-in-one" package. They were not designed for superior sound reproduction.

If you check the local CL or FB Market listing you will find scores of similarly sized Boston Acoustics, Polk Audio, Klipsch, ADS and other speakers that were known for good sound quaiity and will probably run $100 a pair, or less.

Way less work, way better sound.

Just saying.

[oliver1850]

Thanks for the replies. I should have stated that the surrounds are gone on all the tweeters and at least one of the midrange drivers is dead.

I have lots of meters and soldering irons. I don't have the crossovers out of the cabinets yet but will post a picture once I have one out. Here are the speakers on hifiengine:

https://www.hifiengine.com/manual_li...r/cs-88a.shtml

As far as $100 speakers locally, I look regularly (more often than for bike stuff). If you can find me a pair of Klipsch or other quality speakers with real wood veneer and 12" woofers for $100 I'd like to see them. I did land a pair of functional KLH speakers for around that but they don't appear to be nearly the quality of the Pioneers. I don't believe that the Pioneers were sold as part of a music system. Last speakers I purchased locally were a pair of JBL 940s. I paid $250 for them and drove about 50 miles for them.

https://www.hifiengine.com/manual_library/jbl/940.shtml

[Bob Ross]

Originally Posted by C40_guy

They were not designed for superior sound reproduction.

^^^This.

I've heard a number of Pioneer (and similar) speakers from the 1970s that all had 12" woofers, two sealed back mid range drivers, two 2" cone tweeters, and a horn super tweeter -- and/or a similarly varied assortment of drivers -- and absolutely none of them sounded as accurate nor as satisfying as a well-designed two-way speaker with one woofer and one tweeter.

There are two things that plague a speaker design such as your old Pioneers:

1 - the more frequency divisions a crossover network has to perform, the less linearly it can perform at any given pricepoint. All things being equal, a two-way crossover network will sum the two drivers' outputs in a more linear and musically satisfying way than a three-way crossover. Or a four-way. Or a five-way. Plus, the more frequency divisions present -- 3, 4, or 5 -- the more likely that more than one of them is going to be in a register where your ear is particularly sensetive. Worst case, with a two-way there's only one crossover frequency to screw up your listening pleasure.

2 - multiple drivers -- especially multiple drivers of the same type (e.g., the two sealed back midrange drivers, and the two 2" cone tweeters in your Pioneers) -- if not time/phase-aligned in both the left-right (horizontal) planes and near-far (distance) planes, will always introduce sonic artifacts and anomalies that range from distracting to positively annoying, especially if you move your head even slightly while listening. This is pretty much a fact of physics, and while there have been plenty of innovative designs over the decades that have attempted to ameliorate those artifacts while still offering multiple similar drivers, the most successful designs (and the easiest to achieve) will rely on the simpler approach of one driver per frequency band, stacked vertically so there is no horizontal offset, and either physically time-aligned or set behind a waveguide that achieves the same result.

In short: You may have fond nostalgic memories of how those speakers sounded 40+ years ago, but unless you are just looking to throw money at a DIY project your time and dollars would be better spent replacing them with a more modern pair of speakers.

[Ozz]

Didn't William rebuild some speakers a couple of years ago? He might have some good info....

[C40_guy]

Originally Posted by Bob Ross

In short: You may have fond nostalgic memories of how those speakers sounded 40+ years ago, but unless you are just looking to throw money at a DIY project your time and dollars would be better spent replacing them with a more modern pair of speakers.

Listen to Bob. He (and I) sold audio equipment (true prosumer hifi) when these speakers were sold. They weren't good then. They haven't gotten better with age and degradation.