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A little help for a friend...
Hey, lpd...
You omitted the Link, but here's a few schematics for the 4333 series.
3133 and 3133A Network Schematics:
4333 crossover modifications
Hi lpd
Your link wasn't posted but Bo fixed that. I think an answer to your question has been previously addressed in this ( or the last ) forum quite a few times . Here's a worthwhile quote on the subject
Quote:
"If I were you I would just bypass your current stock JBL metallized mylars and NPE's with the 0.01 uF AudioCaps and give that a listen first."
Do a search within the whole forum structure for "Bypass Caps ". This will provide you with a basis of opinion that it's better to start your crossover renewel by bypassing the existing caps with .01 uf polypropylene types and then again "bypassing" the bypass cap with a .005 uf polystyrene type cap. This should "open up" the sonic qualities of your existing caps for cheap money.
Types to buy ? You can test-fly the "bypass" concept by purchasing caps from more mundane manufacturers. Try a local electronics shop for small quantities and for these values. You should still find that the concept offers great sonic improvements even from brands with little to no "Marque-value" .
If you've already done this "Bypassing"and aren't satified with the results then read the 4331 thread for a few " pricey " recommendations. Also do a search for " Dayton Caps ".
I'm personally quite happy with my "no name" main caps ( I actually don't know the type or manufacturer but they are smooth - & "slow" is not such a bad thing on a compression driver ). Because they're at least 20 years old they're likely Mylar types. ( Thats what I get for rummaging around in surplus parts bins). They resemble some of the caps found in 70's & 80s' Altec 1209 type crossovers. Mine are 75 VAC and I've never blown one apart - so I figure just about anything you buy these days ( usually over a 100 volts ) should be fine. I own a lot of Solen 400V "fast caps" but I find they aren't exactly complementary to JBL horn drivers.
I've never tried a "Charge-Coupled" topology to see if Solens sonic signature dissapears like I figure it might ( a worthwhile project to "eatup" my supply ).
regards ,> Earl K
Cheap, but good caps for JBL,s!
My experience with caps for JBL and other vintage horn gear is a cap called Xicon! They used to be known as Transcap and they have a smooth sound! They arent expensive, but I have tried some VERY expensive caps that I always found to be TOO bright and forward sounding with JBL and Altec horns!
Xicon caps are available from www.partsexpress.com!
:scoot:
Re: Cheap, but good caps for JBL,s!
"I have tried some VERY expensive caps that I always found to be TOO bright and forward sounding with JBL and Altec horns!"
Yeah, it's a balancing act to be sure. The polystyrenes should take off some of that brightness and forwardness associated with metallized polypropylenes while adding depth and transparency.
G.T. has said on numerous occasions to use the best polypropylene capacitors one can buy and then just charge couple them. That is the most expensive solution.
I'm pretty much done with funding dielectric research myself ;)
Re: Caps & their "Voicing Qualities"
Hi All
I've moved my post here ( where maybe it's more appropriate ) - away from the Cloning The 4435 Network thread . The original following quotes/thoughts from Giskard on charge-coupling are located at the above link.
Quote:
by Giskard
"This past week I built a pair of charge coupled networks using Dayton metallized polypropylene capacitors for mains and no bypass capacitors. ,,,, These things got very clear."
Thats interesting - do you still use this crossover ?
Quote:
by Giskard
"Overall the sound quality of the unbypassed, non-charge coupled metallized polypropylene's wasn't as good as the stock metallized mylar bypassed with polystyrene and polypropylene. (Duh! We've only known that for over twenty years now) Charge coupled, the metallized polypropylene's were slightly better than stock, with lower distortion, better top end, and exceptional attack, but not as much depth and warmth."
I'm experiencing something very similar right now. As some may remember my system is biamped. I've replaced the DC blocking caps on my compression drivers. The old caps were those unknown type, red-ended tubular types that you/Gisakrd once caught a glimpse of . The replacement caps are metallized polypropylene in oil ( AC motor-run, made by Mallory - more "dumpster-diving" - metaphorically ) . I haven't charge-coupled these yet ( I will this week ) but based on a comparison of their sonic signatures , my old caps must be a Mylar type. The comparitive difference is quite stark. The old caps actually seem to offer a type of spectral compression/limiting in the midband area that keeps my compression drivers from jumping into my face. This apparent "torque" decrease does help the compression driver work in closer concert with the paper coned tranducers. It now seems my whole kludged together MTM setup has been "balanced" around the speed signature of these old caps. FWIW, the new caps are certainly closer sounding to " a straight -wire ". Too bad that, because in fact I'm looking for some actual filtering/slowing-action to help in the blending/voicing of the disparate component types.
I also bought "paper & oil" AC motor-run caps. Interesting, but they didn't have quite enough of the "soft-compression" signature I was looking for. In fact , they are a lot more "straight wire" than I expected. They are quite charming on trombones and tenor saxes/voices but certainly not as "clear & accurate or fast" as the Mallorys'. Lets say they are like filtering the polyproylenes through an MP3 algorithm. Bypassing them with a mix of Solens and other mystery-bin poly-types created something truly horrid . Well, actually, if one is an electric quitar player, it's a dielectric combo that might be useful for creative expression.
Quote:
by Giskard
"I would say warmth is what was lacking most though."
- Did you ever recover that lost warmth ?
My system has lost apparent warmth and the front to back imaging has also taken quite a hit - I guess I should expect this when a compression driver is allowed to "straight-arm" the listener - like a rambling fullback in mid-stride. I've had to resort to using a 2123h instead of my usual le10 mid/bass to recover/invent/ some warmth. And I do love the neutrality of the le10 as a midbass driver but so far it just won't "shake-hands" with any polypropylene cap/compression driver combo . I like these Mallory caps and hear great promise in them which is why I haven't just turfed them and gone back to my mystery cap setup. Among the things that I like; - the apparent "Q" of my 45° horns changed when the polypropylene caps where intalled ( this also happened with the paper/oil type ) . Horn "Q" went down - and apparent midband dispersion went up.
Quote:
by Giskard
" Needless to say, I will be installing some good film and foil bypass caps this week. Hopefully the Daytons won't respond negatively like Solen's do when bypassed."
- Did you do ever do this and how did the Daytons respond to the bypassing?
- I'm going to try blending dielectric types in a charge-coupled topology this coming week. ( One dielectric type on side"A" - the other type on side "B" ).
- Last week I found I could submerge the sonic signature of the polypropylene cap if I "swamped it" with huge values of the "Mylar" type. A 6 to 1 mix ratio made the polypropylenes' signature dissappear . This is what has led me to try blending different types - even with the predicted "timing" errors - though the class A charge-coupling ought to remedy that drawback. Has anyone ever tried this ?
regards <> Earl K :)