Sigurd O. Stefansson,
Bergen, Norway
So, it has taken me forever to finalise this project, and getting around to publishing some pictures and thoughts, but now finally
From where I left off a number of changes have been made, here's a brief overview (in no particular order)
1. Stripped the enclosures of old oil and added Danish oil, two coats, wet-in-wet. An exciting part of the work. The old oil came off quite easily with some wood-cleaner/stripper mixed with water, then lots of clean water to remove any residues
2. New Danish oil added, wet-in-wet, two coats, used the same approach we used when we were restoring wooden boats, stopping at two coats made a Nice, structured surface with the grain easily visible/Nice to the touch/not too shiny
3. Drivers: As mentioned above, I replaced the 2420s With 2421Bs, and in doing so I opened the back of the 2421s, and of course the old foam lining had transformed into some messy glue-like, black substance. So, I stripped the inside of old goo and made a couple of felt-liners for the covers, thickness about the same as the old foams. Came out quite nicely I think. In the process I also managed to ding one of the diaphragms when putting it back after cleaning the frame of old goo, , so I replaced them both with NOS JBL diaphragms
The rest of the drivers where in excellent shape, so no changes
4. X-over/system: Major Upgrade . I asked Guido to build a pair of CC 4343 x-overs, which now sit in the bottom of the enclosures. The system is now bi-amped, using a Rane AC22 (for now) @ 300 Hz 24 dB/octave, the woofers fed from a BGW 250E (for now) and a the mid/highs are driven by a Border Patrol P20 (you can see it in the Pictures). I will keep this overall set-up, but active x-over may be upgraded to a Pass, and I have a Plinius amp which will replace the BGW (which is actually a very nice amp as many have posted here)
5. Braking in: OK, this may be controversial, but I am now safely in the herd of the believers . When I put everything together, it sounded congested, dull, unresolved, boring, no air, I was well and truly disappointed. A lot of New Components to be sure, diaphragms, x-overs, cables (speaker cables are now Oyaide, one of my suspects). So, in desperation I put on a burn-in CD I had lying around (Purist Audio, Rev. B), and let it rund for 5-6 cycles. Didn't really expect much, then put on a CD by Gene Clark (yes I remember this in detail), and started to prepare dinner. The change was no less than a total transformation, punch, air, resolution, ...
OK, that's about it, thought it was about time I contributed some back to this exciting forum,
Sigurd
Last edited by S.O.Stefansson; 12-22-2015 at 01:53 AM. Reason: missed pictures
Sigurd O. Stefansson,
Bergen, Norway
must have hit the wrong key
Sigurd O. Stefansson,
Bergen, Norway
a couple more pictures
Sigurd O. Stefansson,
Bergen, Norway
Vemodig vakkert!
Johnny Haugen Sørgård
Very nice job.
43XX (2235-2123-2450-2405-CC 3155)5235-4412-4406-4401-L250-18Ti-L40-S109 Aquarius lV-C38 (030) 305P MkII
Sigurd O. Stefansson,
Bergen, Norway
Very nice. Normally wouldn't recommend using plastic / nylon standoffs and wire ties to secure the high power resistors, never can tell how hot they might get.
When faced with another JBL find, Good mech986 says , JBL Fan mech986 says
Beautiful!
Congratulations... and thank you for the wonderful report.
Widget
Beautiful results. Likely worth all of your time and effort to keep these bits of JBL heritage in use for a good many more years.
David F
San Jose
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