I have been buying the parts I need to make a set of Altec Model 19 crossovers for my HeathKit AS101's (Altec Valencias in nicer cabinets). My initial plan was to use all Solen caps and they have been purchased already. Each crossover uses a 6uF, 8uF, 16uF and a 21uF capacitor.
Well, at the local flea market I found a lot of stuff from a ham radio estate clean out. Box of vintage oil and paper caps, the big ones, mostly with stud terminals. Large rectangle metal cans, a few were even Western Electric!
With what I have, the 6uF, 8uF are covered. I have 4 each 10uF that test close to 10.4uF, so that gives me the 21uF. Just looking for 16uF caps now.
I have been told by an older audio engineer that works with Altecs that these caps will sound a lot better than film caps.
Does anyone have any direct experience with this?
Thanks
BillWojo
Well, at the local flea market I found a lot of stuff from a ham radio estate clean out. Box of vintage oil and paper caps, the big ones, mostly with stud terminals. Large rectangle metal cans, a few were even Western Electric!
With what I have, the 6uF, 8uF are covered. I have 4 each 10uF that test close to 10.4uF, so that gives me the 21uF. Just looking for 16uF caps now.
I have been told by an older audio engineer that works with Altecs that these caps will sound a lot better than film caps.
Does anyone have any direct experience with this?
Thanks
BillWojo
Well the Russian PIO are very popular right now for crossovers, so maybe your vintage caps will be good.
I have not used them. Mostly I bought modern motor run caps, which are oil filled. Used them with my Altec rig and liked them. Not expensive. For small values I used standard film caps.
I have not used them. Mostly I bought modern motor run caps, which are oil filled. Used them with my Altec rig and liked them. Not expensive. For small values I used standard film caps.
Just keep in mind that oil caps, like electrolytics will "dry out" in use over time. Of course the capacitance will go to hell in a hand basket. Most of my experience is with old guitar and bass guitar amps for the '50s and '60s. I've run across a few oddball, off brand guitar amps from that period with oil in paper caps in the construction and those were the first to replace as I went through these amps.
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lespaul, these are not tubular caps but the big metal can style with porcelain insulators on top. So far I have collected 13 pieces and they all test very close to the stated value. I do have one that is oily on the top, a leaker, that one will go in the garbage. No need to have PCB's loose in the house. These are 600VDC up to 1500VDC. Unless they were subjected to over voltage, I suspect they are still good. My cap tester shows most to be within 5% of stated value. I don't have the gear to test them at rated voltage however.
My plan is to try them in a crossover.
BillWojo
My plan is to try them in a crossover.
BillWojo
I am also an old audio engineer that has used both types of caps in different situations,firstly the cap value is for managing the slope ,and your measurements are fine,but the amp is the voltage driver that has to deal with the cap,so some amps love foil and some oil.most altec speaker systems I have used or modified I did feel the oil caps to be more luscious and fleshed out,they will need a long break in as you will probably not run more than a few volts into them,
Personally I use both as well as electronic crossovers.
Personally I use both as well as electronic crossovers.
That's some good information soulsheiksan. These will be driven with tube amps. My main amps at the moment are a set of restored Mac MC40 monoblocks. I also have a smaller 10 watt SET amp that I will be using on them. I suspect there won't be a lot of voltage driving them, the speakers are rated at 30 watt's I believe.
BillWojo
BillWojo
Nice way to put it.. foil and oil are the way to go with compression drivers. To me they have the 3D meat-on-the-bones sound. I have been using them for decades and whenever I've switched to modern "high end" capacitors in my crossovers the lushness of tone goes away. I still have a pretty sizable stash of Vitamin Q's NOS 🙂 I inherited from my Uncle the Guitar amp guru.Nice caps.
I like to shop here http://www.electronicsurplus.com/capacitors/oil-filled-capacitor
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I'm hoping that the guy I bought these from at the flea market brings more tomorrow. Looks like he did a clean out of some ham radio guys basement. Need 2 pc 16uF yet.
POOH, I appreciate your comment, sounds like I'm heading in the right direction. I like your shopping mall to, looks like a "mall for men".
BillWojo
POOH, I appreciate your comment, sounds like I'm heading in the right direction. I like your shopping mall to, looks like a "mall for men".
BillWojo
16uF might be a difficult find. If you don't find something vintage that you like, just pop down to your local HVAC store and pick up a 15uF motor run (not motor start) oil can cap.
Hang a 1uF foil cap off of that to get where you need to be. I've done that plenty with Altec and other gear and always been happy.
Hang a 1uF foil cap off of that to get where you need to be. I've done that plenty with Altec and other gear and always been happy.
Pano is correct cascading filter caps is the best ,and you can try many variations to get the best sound,mount your crossover outside at first and play away for a few weeks,Peter snell made all his crossovers this way ,some snells had 3 different caps ,I just rebuilt a e111 with some oil and film cap and was surprised at the sq.
MBGO caps from the 1980's have reasonable ESR, nearly dead on values, are affordable enough for charge-coupled application and imo "sound good" (and neutral with regards to not rolling off the top) fwiw I prefer those and KGB to things like Obbligato motor run poly caps. But then again motor caps in general are probably better buys than boutique caps. Stan Ricker said something about using a string of big caps in series and "plate area" for sound quality.
I just looked up those MBGO caps, very reasonable price wise. The guy who had the caps at the flea market didn't bring anything new this week, oh well, there is always next week.
I did stop by my buddies today and he gave me a set of 1uF 1000VDC oil caps, could use them with some 15uF oil caps.
BillWojo
I did stop by my buddies today and he gave me a set of 1uF 1000VDC oil caps, could use them with some 15uF oil caps.
BillWojo
Just to voice an opinion, the oil caps will soften the attack on the Altecs. I've been playing with the crossovers in my model 19s for over 10 years and found that while oil caps give a more relaxed presentation they also relax the impact of the horns.
I think that oil caps with a film bypass gives a better balance and retains the good part of the Altec sound while providing a more hifi sound.
I happen to like the Altec sound and have gone back to Solens on the low pass and film bypassed oils on the highs. I also tried both foil and wire air core coils but ended up back with the original Altec inductors as they sounded better to me.
I think that oil caps with a film bypass gives a better balance and retains the good part of the Altec sound while providing a more hifi sound.
I happen to like the Altec sound and have gone back to Solens on the low pass and film bypassed oils on the highs. I also tried both foil and wire air core coils but ended up back with the original Altec inductors as they sounded better to me.
I agree - a little - on the softening by big oil caps. It's subtle, but welcome in many cases. Since my crossovers always needed non-standard values anyway, they ended up with P.I.O. and polypro bypass anyway. Like Zelgall's combo. Works!
Looks like I will be on the look out for some small value film caps. Any particular size or will any small value (0.1uF) work?
Thanks for all the good info.
BillWojo
Thanks for all the good info.
BillWojo
0.1uf is pretty fine. Not likely you'd hear it. I usually tune by percentages, and 1uF and 0.68 come in handy for fine tuning. Getting finer than that you can measure the difference, but you probably won't notice it. At least in the ranges you are working at.
Pano,
I'm confident that you would have noticed this "softening effect" more-so, if you had been able to run your 288's fully up to their HF extremes ( without crossing into a tweeter, at 7K was it ? ).
I agree with zelgall, that Motor Runs are the way to go to build a sold, deep midrange upon .
FWIW, virtually all modern Motor Runs are Metallized PolyProp swimming in oil.
They are all heavily damped capacitors with ( to my ears ) slew rates ( or transient behavior ) that dramatically decreases with increasing frequency ( & this is their true value since it's a predictable behaviour ).
The Cascade philosophy that I employ is that if the RC ( HF ) correction filter has ( say 6 uF ) a cap bypassing the restive pad, then that same amount ( in uF ) of Modern Polypropylene cap is used ( paralleled with ) the base Motor Run ( to arrive at the combined value ).
- This allows the HF bypass circuit to have an equal ( high transient ) route ( in uF ) between the amp & the driver.
- OTOH, if one only adds 1/2 the uF needed to the base cap ( 3uF instead of 6uF ) one can build in a transient hole ( that somewhat emulates a BBC curve, not in FR, but in transient behaviour ).
Playing with the makeup of these composite caps allows one to implement the passive equivalent of a frequency selectable compressor that's also combined with an Aphex Aural Exciter ( for constructive UHF resonances ) .
- Small value bypass caps will typically create these constructive resonances for fake UHF ( which can be extremely useful when running without a tweeter ).
🙂
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