CD protection caps for all drivers in system?

[Doc Mark]

Greetings, All,

I'm getting ready to work on a few projects that have long been in the works, and as I'll be using some older Crown amps in these systems, have a few questions about DC protection for all the transducers involved.

The drivers I'll be using, and their crossover frequencies, are as follows:

2245H - 300HZ
2123H - 300HZ to 1,200HZ
2445J - 1,200 to 8,000HZ or 10,000HZ
2405 - 8,000HZ/10,000HZ

In another system, I may use the two 4645 cabinets, with 2245H's in them, crossed over to the L250 cabinets at 40-50HZ.

So, my question is what sized caps should I use to protect each of those drivers against DC, both cone and CD, should the Crown amps go South on me? I've used the "search" function to see what others have suggested, and found conflicting information about the CD's and no info on protecting the cone transducers. Any and all info or help will be greatly appreciated!! Many thanks, and God Bless!

Every Good Wish,
Doc

[audiomagnate]

Are you using an electronic crossover and four separate amps?

[danvprod]

I have a similar-ish system, I think. Electronic crossover in front of 6 channels of amplification. JBL 2226 600 Hz, 2445 600Hz - 8000 Hz, 2405 8000 Hz +

I've contemplated putting a series cap in front of the 2445/2405 but haven't yet. I have 16 ohm drivers, so a 47 uF for the 2445 (6 dB/octave at 200 Hz) and a 5.6 uF for the 2405 (6 dB/octave at 2k). This is outside of the passband by 1.5 octaves and 2 octaves respectively, but still would protect the driver if something goes wrong.

For now I am living on the edge...

[Doc Mark]

Hi, audiomagnate,

For the 4-way, yes, electronic crossover to each driver, and four different amps. For the L250 system, IF I feel the need for subwoofers, it will be only one crossover electronic crossover point, and only two amps. For that system, I'll use either a Crown DC300A or Peavey CS1200 for the subs, and my Harman Kardon components system for the L250's (HK 870 amp 100WPC high current capable); HK 825 preamp; HK EQ8 (with low frequency filter which is variable from 5HZ to 30HZ); and HK TU 915 tuner. I may use that same system with the L300's, and the subs powered with the CS1200.

The amps for the 4-way system will be the following:

2245H - either the Peavey CS1200, or a Crown DC300A;

2123 - Crown DC 300A;

2445H - Crown D150A II;

2405 - Crown D45.

I hope that answers your questions, but if not, please let me know what else you need, and I'll get right back to you. Thanks for your help, and God Bless!

Every Good Wish,
Doc

[Doc Mark]

Hi, danvprod,

Thanks for your comments. With JBL diaphragms and recone kits becoming more and more scarce with each passing day, I am more than a little frightened of "living on the edge"!! :eek: I'd rather be as protected as I can be, and hopefully, my JBL's will continue doing what they have been doing, for many, many more years to come. Good luck with your own system, and I'll post how things for me when all the info has come in, caps have been secured, and the system(s) are up and running. Thanks, again, and God Bless!

Every Good Wish,
Doc

[Doc Mark]

Evening, All,

I found an Harman Kardon setup just like the one that I will be using on the L250s. Here's what I have. Got it all at a swap meet, many years ago, from the original owner, for just $300, and it came with all the original boxes, and paperwork, too. Got it home, hooked it up, and everything was great, other than the preamp, which works wonderfully, but takes a little longer to get out of the standby mode. That got better as I used it, for some reason. Anyway, here it is:

http://www.ebay.com/itm/181709768790?_trksid=p2055119.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT

I'll the CS1200 for the subs, and VFX-2A for the crossover. Take care, and God Bless!

Every Good Wish,
Doc

[audiomagnate]

If you're worried about blowing a woofer, I would recommend a fuse, not a blocking cap.

[Doc Mark]

Hey, audiomagnate,

Good idea, and one for which I'll find info here on the forum. I guess, to be really safe, I should fuse the 2123's, too, right? Having seen, first hand, what a Crown DC300 amp can do when it passes DC to speakers, I'd like to have protection on all the drivers in the 4-way. In truth, I'm not worried about the L250s and the subs, as the HK gear which will run the L250s has plenty of protection for the speakers, and so does the CS1200X. It's the 4-way, with multiple Crown amps about which I'm really concerned. Thanks, again, and God Bless!

Every Good Wish,
Doc

[jfine]

I was told by a speaker repair guy that even fuses aren't "fast" enough.

[Ruediger]

A fuse spoils a technical property of a cone driver, which is most important for the bass driver. A proper electroonic xover should contain a per-output limiter, making the fuse obsolete.

Ruediger

[Allanvh5150]

A fuse spoils a technical property of a cone driver, which is most important for the bass driver. A proper electroonic xover should contain a per-output limiter, making the fuse obsolete.

Ruediger

Pretty sure he is meaning if the amp goes DC.

Allan.

[Doc Mark]

Good Afternoon, JBL Friends,

Well, my problems and worry about an older Crown amp passing DC to one of my transducers, seem to be solved, and in a very unexpected way. I found a Crown PS400 on "the bay", a few days ago, and sent BMWCC a private message, asking if he would please check it out and share his thoughts on it's condition, and price. After hearing what he had to say, I decided not to go for that one. He urged patience, and I was prepared to go the distance to get one of those safe Crown amps. I had not idea that I would not be waiting long!! Phil sent me a link to one he found day before yesterday, and the seller was only a 3 hour round-trip from me! I contacted the seller, made a deal on his amp, drove over and picked it up, and now own a very nice, little used Crown PS400, with it's proper Crown XLR adapter!! Got it for just $200, and since I picked it up, there were no shipping charges.

I've been testing it all morning, and am pleased to report that it sounds very good, indeed, is totally quiet in it's operation, and exhibits only a hint of warmth to the touch, even after playing all morning. My sincere and very heartfelt thanks to BMWCC for his very kind and generous help in this venture!! Huge thanks, Phil, and should you need a favor in the future, please don't hesitate to give me a shout!!

I hooked it up to an Harman/Kardon 825 pre-amp & an H/K CD changer. Despite how lovely the amp appears, I hooked it up to the very first set of satellite speakers I made way back early 1980's. It's a small, sealed box system, with a 6 1/2" Peerless polypropylene woofer, and Peerless fabric dome tweeter. I used those little satellite speakers to go with a single, 12 dual VC subwoofer, and in truth, it sounded pretty darned good back then. I did a better job on the sub, looks-wise, than I did on the sats, but hey, they are what they are. After a few hours of happy listening, I swapped out the speakers for some JBL L19's, and the bottom end really came alive! Bought the L19's on ebay, and the seller had had the woofers refoamed, and it was done wrong, being sealed to the front of the cones, and not the rear. They still sound good, though.

Here's the amp, the setup for testing it, "part 1":

6516965170651716517265173

I'll post the other four photos in "part 2", as soon as these post. Stay tuned....

[Doc Mark]

"part 2":

65174651756517665177

I'm as happy as if I'd just won the lottery!! Amp remains totally silent in operation, without even the least hint of hiss or hum. It sounds wonderful, accurate, and quite punchy, with no listener fatigue, even after all the hours I've been enjoying it today.

NOW, with huge thanks to BMWCC, without whose help, I'd have never seen, or had a chance to own this wonderful amp, I feel comfortable moving ahead with my JBL projects, on several fronts! This amp will be used with our L300's, just for fun; with the L250's, both with, and without a subwoofer setup; and also in my 4-way JBL system, to power and protect the 2123s. The huge Peavey CS1200X will power the subwoofers safely, as it has total protection from passing DC, and now the 2123s will also be protected, thanks to the circuitry contained in this excellent PS400 amp! I'll use a 47mf, 300V cap on the 2445's, and a 4.7mf, 300V cap on the 2405's, and feel very confident at, now, all of my transducers will be safe and sound, each protected from DC melt-down!!! Thanks, again, Phil, for your help in this!! Take care, and God Bless!

Every Good Wish,
Doc (Happy as a kid, trapped in a candy store all night long, with no supervision!!)

[JeffW]

You just missed my PS400/PS200 giveaway by a couple of years, Doc. Gave a guy here a PS200, another member here a pair of PS200s, and a guy returning from Afghanistan a PS400. But I kept a nice example of each for myself ;)

But really, you'd have a huge wad of caps to pass an unadulterated signal to a 2245. And I bet those caps would have cost more than $200.

[Doc Mark]

Howdy, Jeff,

You, my friend, are a very generous, and kind Gentleman, and I thank you, not only for helping me, but for all the great help you've doled out to others in need. And, very well done on gifting a PS400 to that returning Vet, after he served in Afghanistan!! I look forward to seeing you again at a future JBL event, if not before. Take care, and God Bless!

Every Good Wish,
Mark