Capacitors...debunking the shame of vintage crossovers

I’m in the capacitor upgrade camp. First speaker I really upgraded was a pair of AR5’s. They sounded sooo much better with modern caps. Amps, too. Fishers, Dynacos…got to get good caps in them. I do like certain old, tubular caps in guitar tone circuits. It’s like the worse they sound as couplers, the better they sound in a guitar. For my Altecs, I haven’t really finalized the cap. I’ve got a big clump of poly types, 2 uf, 5 uf, a couple 1 uf’s, to get the value I wanted. But, I haven’t decided on the final cap. Was going to go PIO.

Maybe I need the MCap Supreme….hmm
 
I have a local dealer who is trying to assemble the parts for a crossover for my speakers. It is taking a fairly long time finding the paper in oil Western Electric caps he wants to use for the crossover. The midrange driver in my system-- Western Electric 713b--presents a bit of a problem because of its low impedance compared to the rest of the system such that high value or parallel caps will be needed. I don't know about crossover design so I am leaving this up to him, but, the caps he wants are quite expensive. The other problem is that even if the caps are within specification for capacitance and leakage, it is hard to find ones with low ESR and a number of caps have been acquired and rejected for this project.

I recently heard a speaker being built in this store where some vintage paper in oil caps were originally used for the build but they have been replaced with new Audio Note copper foil caps. The speaker sounds "drier" and cleaner than with the vintage paper in oils, but, I sort of like the sound. The dealer said that the caps were quite good for "cheap" caps (only about $1,000 each). I might inquire about the silver foil versions.
 
I have a local dealer who is trying to assemble the parts for a crossover for my speakers. It is taking a fairly long time finding the paper in oil Western Electric caps he wants to use for the crossover. The midrange driver in my system-- Western Electric 713b--presents a bit of a problem because of its low impedance compared to the rest of the system such that high value or parallel caps will be needed. I don't know about crossover design so I am leaving this up to him, but, the caps he wants are quite expensive. The other problem is that even if the caps are within specification for capacitance and leakage, it is hard to find ones with low ESR and a number of caps have been acquired and rejected for this project.

I recently heard a speaker being built in this store where some vintage paper in oil caps were originally used for the build but they have been replaced with new Audio Note copper foil caps. The speaker sounds "drier" and cleaner than with the vintage paper in oils, but, I sort of like the sound. The dealer said that the caps were quite good for "cheap" caps (only about $1,000 each). I might inquire about the silver foil versions.
That makes sense. I was just discussing this with a customer setting up a 713B/728 combo. Yeah, the "Feeling of Prescence" era Western Electric components... ie the WE755,WE728, the 713 drivers (most of them) etc were all very low nominal impedance for the era -- back then the norm of course was 16ohm for most all drivers, then 8ohm by the early/mid 60s. Other than WE and a few RCA other odds & ends, we didn't see low impedance in HiFi until the later Solid State, "wattage wars" era.

But it's no big deal.... just run the calculator and you can see the values of the chokes and capacitors simply change for the low impedance coils. For the bigger or lower uF figures, you can certainly find these values surplus online pretty quickly. In reality anything approximately close usually works pretty well. But when you go shopping for some of the fancy "Fru-Fru" audiophile caps -- strange values I've noticed are scarce or really expensive.

Last time I chatted with Joe, he had an interesting working theory, or perhaps just an observation that WECO had a nice ecosystem going with the lovely 171C OPT (arguably the best sounding, and most flexible in the world, really) -- and it has a nice 4 ohm tap perfect for the full range speakers.
By the time everything was plumbed into the crossover of the WE757 system – – I think the system was strapped for to present a 16 ohm load – – but will have to go back and look at that.
The other hi-fi era WE systems – – like the 753 came in a variety of impedances. But everything was wired up a little bit differently back then. The special KS version of the Jensen A15PM woofer, was 16ohm (reads around 11ish DCR as I recall)

Keep in mind, ESR is a test made in the non-audio domain (usually 100khz where the mosquitos listen?) , and "leakage" is a test for HV DC applications, not LowVolt AC like music.
Most types of "Leaky" caps subjected to HV 200~600V DC (aka 0 hz) will slowly reform, but some only to a point. How all this might apply to a LV audio signal (10 - 30 volts ish AC) is very much in the air, but to some extent is observable on a Freqency-Impedance sweep test. You guys might want to check those rejected caps that way -- results likely won't be what you expect. Will they sound good? Some will, and some won't -- depends on type and brand as per previous discussions, I guess.

Any rate, crossover circuitry is absolutely nothing special...do go there, and don't stay in the dark....get involved in your design (use a simple 1st order or 2nd order circuit and play from there) , and do some experimenting. Alligator clips will be your best friend and best teacher. You'll find what you like very quickly.

To that end, I think $1000/ea for any capacitor is too much...... I hate to say that – – because I do also sell very expensive capacitors, just nothing close to that..
I can't think of any that would be worth paying more than a a few hundred/each (max!)) for (at this time). That even covers the rarest of the Western Electric paper oil capacitors in perfect operating condition that are on top of the sound, also collectible. There are a few other capacitors that have specific uses and very rare cinema equipment that get a little bit expensive as well – – but I know what you were talking about.

It's those very expensive foil capacitors made out of various types of plastic and high-tech dielectrics and maybe some silver and other nice materials. I have a friend who got all into the Black Gates and did like the sound I know that they probably do deliver a bit for the money – – but nothing close to what they cost. There's absolutely got to be an alternative for 1/10 of the price at least that is my guess.

Even if you were looking for the sweet and dry – – Or clean and dry I've heard that description a lot of extremely high-end capacitors.
Actually, when you hook them up to test equipment you can kind of see that kind of result... They are fast, they don't leak, and they have a sharp cut off with a very clean looking curve . I think that can help out some systems or at least at least give a initial impression of a very clean and hi-fi sound.
The downside to this I think, might be a bit of notch out in frequencies – – because the capacitor is performing in such a strict manner. That might be what you're hearing. The clean and dry sound can be very alluring at first – – and also possibly lend itself to a very tight circuit --- don't spend big bucks on that discipline – – and also don't fall for that type of tonality until you have lived with it for a while... that can get your ears tired quickly, along with the feeling, you're missing some of the music (esp elements in the midrange).

And on the oil capacitors, you'll definitely have your work cut out for you if you want to listen to all the different kinds available. They all sound a little bit different. Friends and customers have told me that they often don't care for the kind of rough quality motor starting capacitors (YMMV, there are many different ones) – – but those tend to be the modern oil capacitors with different dielectric materials. When we're talking old paper and oil, are usually talking about the stuff from the 1940s or 50s – – companies like Aerovox, CDE, Sprague, and TOBE all made nice ones for the Military / Aerospace, you can still get really cheaply. Western Electric ones do sound better. And they aren't super expensive -- they come in very low values, with great voltage ratings. If you need more uF you can just strap them together..

My friends that like to make really bulletproof stuff – – scour eBay for military and aerospace surplus – – there are so many different types of exotic materials you can get for peanuts – – often brand new – – originally made with no price point (aka for the military/gov't). This also includes bi-polar tantalum caps which can be found in values very appropriate for your crossover.

While I do have a lots of customers that adore the oil capacitors – – me and friends kind of prefer the electrolytic type (functional ones, tht is)– – and I've also really had great luck with paper wax capacitors (aka WE437/439 or 137/139's) – that's what WECO used with your 713 (usually) – I think they sound more neutral with fewer colorations compared to any of the other types (nevermind the higher ESR). Me, other sellers or eBay -- those won't run you more than $50~100 /ea and sometimes way less AS-IS. Try to buy them tested unless you don't mind the gamble... or if you don't care. I just sold a pair of prewar 139 (2uf) for $200 tested ... Some would consider that a fairly high price. I think they are still on the rise – – and you can definitely get them for less if you shop around.
Even the leaky ones if they aren't too far gone are still playing well for many.

Still testing that bold statement – – and apologies for that test session I was going to have... Got my Solens lined up – – and my drifted / and not drifted or leaky Western Electric's lined up – – and will be getting them together on the bench hopefully soon.

That's why I wanted to get to some testing. Whether or not you like the tone of one capacitor or another – – that is definitely a thing as well.

Personally, I like components that screw around with the sound as little as possible (tweaks like that are, in effect, a form if analog EQ ...if you are say, rolling tubes, wire or caps to fix or alter). A neutral / natural sound is, itself quite revealing (and least fatiguing). These components are around, but you sure do need to hunt for them. Read what others say, and perhaps avoid the parts that have a collective reputation for brightness/harshness (as I find that can be the toughest thing to work out of a setup) (by the time the "harshness is out of the brite, it then sounds dull, etc, etc).

Sealed/ported/and many Reflex systems of the mid 60s~70s sounded way too dull / dark from the factory.... One theory as to why that may have been – – many silicon solid-state amps back then were super harsh. Mellow speakers sounded much better with them. By the late 70s mfr's caught on...they made adjustments and more-so when in the 1980s MOSFETs began to rule the roost...some got downright milky and dark! Bright speakers came back because then they sounded better with the mellow amps. Sort of like just industry adjustments/fads in reaction to changes in electronics we think. Nowadays when you fire up those old speaker systems from any number of the classic companies, and run them with a nice tube amp.... they sound too mushy... "Upgrading" the capacitors is sort of like tweaking the brilliance control and can definitely make those set ups sound "cleaner" and more precise....that's one theory, anyway.

Surprisingly that's what a lot of the old world materials frequently provide....neutrality
 
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hifitown,

Thank you for your very informative post. It sounds like you have a lot of experience with this kind of vintage gear. My local dealer, who puts together custom-built systems with mostly vintage drivers has a newly built system running WE 713A/32 horn midrange, 18" Goodman woofers, and currently manufactured Fostex tweeter. This is a really nice sounding system. He originally had a crossover that used, I believe, Sprague paper in oil caps, but, given the sonic taste of a particular potential customer, he changed out the caps for some modern Audio Note caps. This system is VERY dynamic, punchy, and has a lot of weight to the sound. I like the clarity of the Audio Note caps, but, it is taking quite a long time for the sound to stabilize.

What is particularly interesting to me is that the 713A driver and the Goodman woofers cost a small fortune, but the tweeters are very cheap. The builder chose the tweeters entirely by what he hears and the fact that he only requires the tweeter to play at the very top of its range. While I am not in the market for new speakers, I do lust after the Goodman woofers--this dealer has both 18" permanent magnet and field coil versions and they are my favorite woofers. The other drivers this dealer has, and I've heard in custom systems and I really love is the Jensen M10 field coil driver.
 
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