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fishinbob
06-12-2008, 04:03 PM
Hello all. I want to take a moment to say thank you for this forum. If I have learned anything, itís that there is a great deal I donít know about the subject.

In recent years my JBLís have been part of a 5.1 system with little emphasis on music. The system was used by the whole family and after the third Ortofon cartridge was broken I elected to remove the turntable and pretty much left it as a home entertainment setup. The room was such that the placement was far from optimum for a good soundstage anyway. Then the big CRT died and the whole thing pretty much fell into disuse. Things change. With the death of the Mitsubishi and the kids out of the house I see nothing but opportunity.:D

I recently sent my D130A's to be reconed intending to use my JBL's as mains for a new front projection theater system. The use of a retractable screen would allow me to relocate my mains to a more favorable position at either side of the fireplace. While I am anxiously awaiting their return, Iím spending quite a few hours searching posts primarily about this 001 system, which I've had since new. After much reading my focus has shifted somewhat, from theater to hi-fi, and I'm considering other repairs or modifications to improve my sound.

I have been looking for info on my crossovers, figuring that they could use some attention after 40+ years. This system is in a pair of Ď66-Ď67 vintage C35 enclosures which I would prefer to leave in tact. As far as I know the crossovers are working, though I have not played them in some time, but I doubt they're in spec. Looking inside the crossover, it looks like a mess to replace the caps unless there is a way to melt that pitch like material surrounding the caps and inductors. I assume the fix would be to clip wires and somehow fit the new caps in the remaining space. Anyhow, I seek advice, as I am looking at either replacing the N1200's with a new crossover and saving the stock ones, or maybe an active crossover could be the ticket. I think Iím getting a bug, because the idea of shopping for a new amp(s) sounds like a great idea.:D

This may be a subject for another thread but I've also seen a couple of posts regarding some of the sonic deficiencies of the 001 system. Some have suggested adding a mid bass to assist in the 600-1200Hz band. If I go with the active crossover is there a proper driver I might use between the 130A and the LE175DLH? I would prefer this mod to be in a separate enclosure. Could a pair of Minuets do the job? I see a pair on CL asking $600 (ouch!!). Also along these lines, do my 63 year old ears stand to benefit from a UHF crossed over to the LE 175 horn? I consider my hearing to be OK. Earlier I considered adding an 075 but decided against it because they had a reputation of being shrill sounding. I can build an enclosure if I must, but the tech stuff I leave to others, so the closer to plug and play, the better for me.

My current (HT) setup is powered by my (old by HT standards) Yamaha DSPA1- pre out to a Mac 2125 and LF out to a M&K mk10 sub. I also have a Mac C29 which will probably go back into the rotation when I dig out the Thorens and the LPís.

Feel free to tell me Iím barking up the wrong tree if this is the case.

Thanks in advance.

Bob

speakerdave
06-12-2008, 07:32 PM
I would focus on the good qualities of that system first. Of course it's very dynamic and efficient, and the fact that one driver covers the range from 50 to 1200, with back-loaded horn support for the lows, thereby limiting excursion, gives it coherency. It lacks low lows which you seem to have recognized with the addition of a subwoofer, and high highs, which you also mention. I would suggest going slow, and adding an N7000 or an N8000 with an 075 or 077 would be my first change. Those crossovers are available in the used market, but it would be better to replicate them with good quality components.

I agree the C35's should be left intact. Any additional midrange component could be placed on top in a separate enclosure, but frankly I wouldn't do that. You already have a treble horn, and I'm not aware of a cone midrange that would keep up with the efficiency of the 130A. Besides, that would in effect be to build a four-way. If you want to do that, I would start from scratch with a 43xx four way and retire the C35's. If you basically like their sound, it would be best to keep modifications to a minimum.

I'm told the icky stuff in the crossover is wax. The N1200, like a lot of classic JBL crossovers, uses a tapped choke which is not available, so if you are going to rebuild you have to get it out of the wax. I've never gone through rebuilding one of those old crossovers, so I'll let somebody else advise you on that.

Basically I guess what I'm saying is continue enjoying that system for what it is, with perhaps the addition of a supertweeter, or start over from scratch.

David

BMWCCA
06-12-2008, 08:12 PM
IOf course it's very dynamic and efficient, and the fact that one driver covers the range from 50 to 1200, with back-loaded horn support for the lows, thereby limiting excursion, gives it coherency. . . . .

I agree the C35's should be left intact. Any additional midrange component could be placed on top in a separate enclosure, but frankly I wouldn't do that. The C35, if that's what he has, is a reflex enclosure; not a horn. No problem to add an 075 since every C35 I've seen already has the mounting hole cut for it, sealed with a rear-mounted blank. There were several loaded horn cabinets available for the 001 system but Bob said C35.

speakerdave
06-12-2008, 09:06 PM
Yes--I was thinking C34.

I guess that doesn't change my recommendations that much. I still don't think I could hack the baffle in that cabinet, but I would find it easier to let go of.

David

BMWCCA
06-12-2008, 09:23 PM
Yes--I was thinking C34.

I guess that doesn't change my recommendations that much. I still don't think I could hack the baffle in that cabinet, but I would find it easier to let go of.As I said, no baffle-hack necessary in any I've seen, and I've got four of them. You would have to hack the back for the N7000. I've added an LE175DLH to an 030. The C35/37 were made for it. For what it would cost Bob to make such in incremental change, he could own a another pair of what he's got or another fine pair of JBLs, like the L7. Personally, I'd put that money in an investment account and try to keep up with inflation while saving for some L300s. But that's just me.

speakerdave
06-12-2008, 10:35 PM
As I said, no baffle-hack necessary in any I've seen, and I've got four of them. You would have to hack the back for the N7000. I've added an LE175DLH to an 030. The C35/37 were made for it. For what it would cost Bob to make such in incremental change, he could own a another pair of what he's got or another fine pair of JBLs, like the L7. Personally, I'd put that money in an investment account and try to keep up with inflation while saving for some L300s. But that's just me.

Did I say he needed to hack it to add a tweeter? He mentioned adding a midrange. And, actually, now that I think about it, I should say it would be perfectly fine to hack a C35 any way anybody wants to. What does it matter? It's just a box, and probably not a very good one. The C34 is of a higher order altogether.

BMWCCA
06-13-2008, 09:07 AM
Did I say he needed to hack it to add a tweeter? He mentioned adding a midrange. And, actually, now that I think about it, I should say it would be perfectly fine to hack a C35 any way anybody wants to. What does it matter? It's just a box, and probably not a very good one. The C34 is of a higher order altogether.I agree. I misread when you talked about adding a mid-range in a separate enclosure and assumed "tweeter". In my house we call the LE175DLH a mid-range (!), but you are correct. At any rate, we both agree any money spent to make the 001 what it isn't, is not money well-spent. Enjoy them for what they are.

fishinbob
06-13-2008, 01:12 PM
I'm sort of enjoying the discourse so far, but would like to sort of refocus this thread to the issue of the crossover.

From what I have seen, most would agree that my N1200's could stand some work. I don't think they are headed for some sort of train wreck or anything like that, but I would like to get the best performance out of these components as is possible.

In a word, I can live with the sound of the original system but seriously doubt I will get the most out of it with these crossovers. It sounds to me as that if I were to purchase any early vintage loudspeaker, from any of the esteemed contributors to this forum, an updated crossover would most likely be included. So I don't have any problem if there is a clean way to accomplish this with mine. I was just intrigued with the thought of an active network and preserving my N1200's for the heck of it. Seems like a nice non-invasive way to do it all, but I'm uncertain about the typical 24db slopes and how this application will work for the 001 in particular.

This whole foray into additional drivers just seemed to be more easily accomplished with the use of bi-amp technology, and I thought it might be fairly simple from an installation point of view and was not too concerned about the costs involved. If Iím headed in the wrong direction it is nice to know.

With regard to the plugged hole for the 075, none exists. If you have the info on the factory location I would be interested though. I assume the N7000 would be located next to the N1200? Probably won't happen soon, if at all. At least I would have a starting point for a hack job. Actually the mill/shop aspect of machining some holes is a no brainer for me. They used to pay me for that stuff.

As for the thumbs down to the C35, I realize it is just an opinion that may be reinforced by the popularity of the rear-loaded horns. The uniqueness of those enclosures most certainly gives them some cachet.. I'm sure the designer of the C35 might take some exception to the remark that it is "just a box and probably not a very good one" but I think we might be comparing apples to oranges. From a construction standpoint it couldn't be further from the truth. Someone in the forum states it's all about compromise, or words to that effect. I guess there are advantages and drawbacks to either design.

As for a comparison between the two, I have nothing other than photos, and in my opinion the C35, at least, looked better to me than the C40 which was the only rear loaded horn available at the time (both enclosures were designed by the same person) Sound wise, I'll leave that comparison to those who know what they're talking about. I'm assuming that the enhanced bass response, good, bad or whatever, was the hook for the rear loaded horns of that era. I have also read that the directionality of the horn-loaded enclosure is of most benefit in a fairly large listening area.

Enter the subwoofer.

speakerdave
06-13-2008, 01:40 PM
Yeah, I was a little harsh about the box. It was made in the day when boxes and drivers were sold separately. Since the 1970's they have been viewed as one system designed as a whole. You might try plugging your 130a t/s parameters into a box calculator to see what it would prescribe. You could also plug in the box size and see what porting/ducting would be suggested. I would figure in some additional bracing.

From an overall perspective, you shouldn't have a box that large and need a subwoofer.

David

Baron030
06-13-2008, 06:36 PM
Quoted by fishinbob
I have been looking for info on my crossovers, figuring that they could use some attention after 40+ years. This system is in a pair of Ď66-Ď67 vintage C35 enclosures which I would prefer to leave in tact. As far as I know the crossovers are working, though I have not played them in some time, but I doubt they're in spec. Looking inside the crossover, it looks like a mess to replace the caps unless there is a way to melt that pitch like material surrounding the caps and inductors. I assume the fix would be to clip wires and somehow fit the new caps in the remaining space. Anyhow, I seek advice, as I am looking at either replacing the N1200's with a new crossover and saving the stock ones, or maybe an active crossover could be the ticket.

Personally, I think you should leave your stock N1200 crossovers intact. And they are probably worth a lot more in that condition as well. Believe it or not, your 40+ year old caps may not have that shifted all that much over time. And the reason why I say this is that I once tested the 32 year old caps in my old N2400 networks. And I found all of the caps to be in good working order. So, even after all this time, your crossover networks could very well be operating within original JBL factory specs. But, if you are really are in doubt then you should test the networks.

After having said all that, you would get some very noticeable improvements just by replacing your old caps. But, the benefits are not without risks. The real risk to overhauling a N1200 network would be to the tapped 1.1mH coil. It is a totally irreplaceable part. And in the all the time that I have been following this forum, I have not seen anyone document what the inductance values are at each of the tap points. So, it would not be possible to hand wind a replacement coil should anything were to go wrong and a tapped coil were to get damaged.

Now, if per chance someone would do the research and get the exact inductance values for each of the tap points on this critical coil. Then it could be possible to hand wind all new tapped 1.1mH coils. And then it would be possible to build all new and improved versions of the N1200 network, using modern materials and techniques. In the low pass section of this network, a heavy gauge 1.4mH air coil would be a real improvement over the small stock iron core coil. This would result in a noticeable reduction in distortion, particularly when the woofer is being driven at higher power levels. And as for the 1.1mH tapped coil, I would suggest an "Erse Super-Q coil" as a good starting platform, for such a coil winding project. The large iron core would allow for good inductive coupling between the windings. And since this coil does act as an autoformer good inductive coupling does become a real critical issue here. So, for this one application, I would recommend iron core over an air core coil design.
And of course, using modern charge coupled and bypass caps as part of the new N1200 crossover's construction would most certainly make for some very noticeable improvements in sound quality. If you have access to an inductance meter and you are willing to try winding your own coils, then building new N1200 networks would make for a very interesting DIY project.

Baron030 :)

Mannermusic
06-14-2008, 05:44 AM
Agree with "The Baron" on all the above. Have checked ancient N2400 caps (caps in a wax box!) and they were right on the button. Have also tried the by-pass cap addition which does indeed yield a nice improvement. Also tried replacing the 13.5 uF high pass cap with a Solen (also with film/foil .01 by-pass). Just clip out the old one, as you suggested and solder in the new. Further gain in openess, clarity, definition. By the way, the C35 was always a favorite here in the Detroit area - optimum for the D130 generally. Many of us built DIY versions at home and tuned via ancient signal generator to JBL specs. Neat to plot the curves and see the Hemholtz phenomenon with your own eyes. Learn a lot as well. And, make sure the push button connectors are clean and tight - the most common cause of distortion, signal loss, et al. Another option is an active tube crossover if you can find one. Luxman 2003 tube is perhaps the best sounding of the old gear but Phil Marchand is making new ones as well, two and three-way. Not cheap. I guess if it was me, I'd get everything back to spec first, then perhaps add an 077 which is an astonishing improvement - silky smooth extention of the top end - musical. And, finally, if you want to get carried away, tri-amp the thing. Cables everywhere, amps, etc. Old D series Crown is hard to beat. And, you need an tube pre amp. Marantz 7C is one of the most musical but hard to find - getting old. There is new stuff out there, however. Seem to be older Macs and Luxman around as well. All "good-goods" but need maintenance, TLC (my Luxman C35 power supply just went South). But, one step at a time - surprising how good a custom tuned passive system can sound . . . and a lot less trouble. Mike

BMWCCA
06-14-2008, 08:11 AM
With regard to the plugged hole for the 075, none exists. If you have the info on the factory location I would be interested though.I'm assuming the "extra" hole was originally meant for another transducer since most of my C37/C35 cabinets predate home two-channel stereo systems. According to the JBL plans for building these cabinets, the holes would be positioned to make the cabinets right or left with respect to speaker placement. I'm assuming the factory-built cabinets then had both holes and perhaps the home-built versions had only one depending on the choice of the builder to make them right or left? I'm only guessing here as my cabinets are as old as I am so I have no real knowledge other than what I've seen and surmised over the past five decades of ownership. All I know is they make excellent pre-cut mounting positions for an 075 or, in my case, an LE175DLH.

Click on the image below for larger version:
http://www.lansingheritage.org/images/jbl/plans/c35-c39/thumbs/page2_small1.jpg (http://www.lansingheritage.org/images/jbl/plans/c35-c39/page2.jpg)

fishinbob
06-15-2008, 01:15 PM
:thmbsup:So.....I guess I may be selling these crossovers short. Sounds like it might be wise to look for another pair of crossovers to do the upgrades, should I choose, and leave well enough alone. That should readÖ to have the upgrades done, as I have little faith in my abilities and none of the proper equipment. The cap bypass doesnít seem too tough though, assuming I cut the right wire.

Baron, I'm curious about the damage issue with the 1.1mH coil. Is the risk due to potential mechanical damage like trying to remove the potting material or something else? One would think that the material would have a melting point low enough to heat the unit to allow its removal.


Another option is an active tube crossover if you can find one. Luxman 2003 tube is perhaps the best sounding of the old gear but Phil Marchand is making new ones as well, two and three-way. Not cheap. I guess if it was me, I'd get everything back to spec first, then perhaps add an 077 which is an astonishing improvement - silky smooth extention of the top end - musical. And, finally, if you want to get carried away, tri-amp the thing. Cables everywhere, amps, etc. Old D series Crown is hard to beat. And, you need an tube pre amp. Marantz 7C is one of the most musical but hard to find - getting old.

My interest in the active crossover was generated from a thread on the performance of the Ashly XR-1001. I was figuring on using my SS McIntosh pre-amp w/ the 2125 and perhaps a tube amp for the LE175DLH . Will I stand to gain that much benefit from a tube pre amp and or crossover?

BMWCCA: Thanks for the lead on the baffle layout. The one shown in your post matches mine only in the location of the bass cutout. My horn is on the vertical centerline about 4 3/16Ē down to center from the top of the baffle. Another major difference is the port. Mine is much smaller than the one depicted. It measures 3 1/8Ē X 8 3/16Ē for just over 25 Ĺ sq. in. Seems there is quite a difference as the one shown in your post is 40 Ĺ . There is just one horizontal brace on the interior which consists of a 2X4, applied on edge between the woofer and the port. Most likely a strongback for the baffle, as it stops short of touching either side of the enclosure.

Thanks again for the feedback. Iím a learnin.:)

Bob

Baron030
06-16-2008, 06:18 PM
Quoted by Fishinbob:
Baron, I'm curious about the damage issue with the 1.1mH coil. Is the risk due to potential mechanical damage like trying to remove the potting material or something else? One would think that the material would have a melting point low enough to heat the unit to allow its removal.

Well, I maybe I am exaggerating about the risks a bit. But, from what I hear the potting material can be melted without any risk to any of the crossoverís components. So, heat is not going to be an issue here. The only real risk to the tapped coils is bending and snapping off one of the wire leads. But, if you are very careful not to bend the leads any more then absolutely necessary, then you should be OK.

But, before you start cracking open the cases and swapping out parts. You should do a little research first. And donít limit your searches to just the N1200 network. I know a while back JBL4EVER overhauled a different JBL network and he successfully melted out the potting compound. Here is a link to his thread: http://audioheritage.org/vbulletin/showthread.php?t=13214
And I am sure that there are other threads here that also deal with removing potting compound. All you have to do is find them.

Also, a while back I posted thread on overhauling a N2400 network, and it might give you some ideas for your own project. And here is a link to that project thread: http://audioheritage.org/vbulletin/showthread.php?t=12938
And who know it might even inspire you to create a ďThe N1200 revealed and overhauled" thread. In 20-20 hind sight, I should have swapped out the original 20ga iron core coil for a large 14ga air core coil. But instead, I used a small 16ga ďI-BarĒ coil for no other reason other then I knew it would fit inside the case. Since, there is just no way to stuff a physically large air core into such a small JBL network case. The thought has occurred to me that a large coil could be mounted on the outside of the case instead. And a relatively simple way to do this would be to swap out the thin aluminum back-cover plate for a new plate made out of 1/8Ē thick fiberglass or plywood. By using some nylon zip ties, and a little adhesive, a large air coil could be mounted on the outside surface of the cover plate and some flexible stranded leads could be used to wire it all up.

Admittedly, it would look a little strange to see JBL network case with a big ass coil hanging off itís the back. :D
But, it would be one way to upgrade to and mount a large 14ga 1.4mH air core coil to a N1200 network.

Baron030 :)

hjames
06-16-2008, 06:50 PM
I opened up a pair of 3110 crossovers last year. I drilled out the rivits carefully and found they were full of some kind of yellow-tan material that was kind of sticky - its beeswax! (or something similar).

I put it in a pot on the stove and put some water in the pan, then very slowly warmed it up. as the beeswax turned clear and melted I poured it into a small container to save it while I could pull the crossover out of the metal housing.