JBL 4313 Restoration

westend

Audiopile
Well, MaxZ28, with his C36 resto, has inspired me to get going on this pair of JBL4313's that function perfectly but have a heap of cosmetic issues. I thought I might document some of the work and technical bits for this model since what I've been able to find is scattered across a number of sources.

My camera happened to be close so I remembered to take the "before" pictures, for once.:yes:

This morning, I removed the drivers, foilcal that covers the L-pad mounting screws and the L-pad. Later, I'll removing the crossover network so that new binding posts can be installed. For now, I've left it on to prevent dust intrusion.

The woofer is gasketed to the baffle. The mid and tweeter are mounted with screws, only. After nearly 40 years, the drivers need gentle persuasion to remove. I used a small putty knife to slide under an edge and lightly fulcrumed an edge at a time. A little bit of the baffle surface came up but that is OK since they will be repainted and that bit of surface is behind the mounting flanges.

The foilcal was removed with a heat gun set on low and the same process with a putty knife. The L-pad mounting screws are under this thin metal foilcal. After removal, I placed one end of the L-pad board inside the port duct and taped it to the network board. That way, I don't need to desolder it from the crossover and it should be stable when I am shifting the cab around to sand and finish. Later, It will be removed with the network board and the L-pads will get cleaned.

Some links to more technical information and pics of the drivers will be posted later. Now, the cabs need to get masked and then sanded. The last pic attached shows some of the materials I'll be using for the restoration:denatured alcohol to remove dirt, oil, and grunge from the veneer before sanding, sandpaper, color putty for nicks and deep scratches, a color pencil to blend in any abnormalities left after sanding, and Watco oil for the finish.
 

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This is dejavu for me. I just redid a pair of 4313Bs a while back. It was well worth the effort though. Cant wait to see your results!:yes:
 
OK, keeping it updated, here.
The sanding is done. I cleaned all the veneer surfaces with denatured alcohol, first. This cleans up a lot of the oils, old finishes (if present), and 40 yrs. of grime. Sandpaper won't clog up as much, either. While we're on that topic <ahem>, there were two possible Nobel Prize winners, recently, the guy who invented 3M synthetic Sandblaster sandpaper and the other guy who discovered that a rubber stick will increase the longevity of said paper by about a factor of 10. These are pictured below.
The rubber eraser is available at Rockler.

The front baffle was masked and the wanut veneer was sanded using the two pad sanders pictured, A B&D 1/2 sheet sander (30 yrs. old, I believe) and a Craftsman 1/4 sheet sander. Both operate in an orbital mode. Progressive sandings of 100, 180, and 220 were used. A higher grit of 300-400 could be done but walnut is dense and you really don't get the veneer any smoother. These cabs were pretty badly gouged, in places and a little finger sanding and filing was done to smooth them out. Edge nicks were filled with Color Putty. Pic #1 below is a before and mid-way-sanding shot for comparison.

Next, is to get rid of the dust and start on the finish.
 

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waiting for finish to dry.....

Might as well share some of what I've found about these monitors: driver numbers and dimensions are listed Here in this thread at Lansing Heritage. Also over at LH, is the original Brochure.
The 4313 came in two different styles, the oiled walnut I'm working on here and a grey industrial matte finish. Grill cloth options were black with the grey finish and dark blue with the oiled walnut. As far as I know, both styles had a black baffle and a black back. When the 4313B was introduced, JBL changed the paint scheme to a light blue baffle. Here is a pic of an oiled walnut pair with black grills with the JBL logo's so maybe they were available in that option:Japanese for sale add.

The drivers that were used in the 4313 were: 10" woofer (LE111A) with cast frame using a 3" copper edge-wound magnet, developing 11,000 gauss. Midrange used a 5", copper ribbon wound,(LE5-9) woofer, developing 14,000 gauss from a 1 5/8 lb. magnet. The high frequency 1" dome tweeter (066), doped by aluminum deposition, also had a 1 1/2 lb. magnet that developed 14,000 gauss. The mid is housed in it's own sub-enclosure and the tweeter is shielded on the back. The internal volume of the enclosure, itself, is only 1.2 cu. ft..

Two changes I'm going to make to this pair are a set of new 5-way binding posts and replacing the plastic grill-holding pegs with neodyium magnets. I will be making new grill frames and have ordered new grill cloth.

Pics below of the second coat of Watco drying.
 

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Someone's been busy!!

It's taken me more than a month to sand down the L36's and I'm still not done!!
 
Someone's been busy!!

It's taken me more than a month to sand down the L36's and I'm still not done!!
Are you hand sanding? I can't do anything, anymore, without the use of a powered tool, lol. It makes it easy, using a 1/2 sheet sander like the old B&D I used. I don't use any pressure or downforce, just guide it over the surface. The only reason I switch to the smaller, 1/4 sheet sander is that it orbits a lot faster so any sanding scratches disappear.
I do some woodworking in my business so I'm pretty clear on what works and the easiest path to take. I finished 25 six-panel oak veneered doors for a customer and when I was done the finish was like their Steinway, lol. There are tricks and shortcuts. Here's one: you don't need to sand or rub with steel wool inbetween coats of oil finish. I apply the oil with a rag and remove dust between coats. After the final coat has dried, I may wet-sand with 600 or higher grit paper. It depends on what I'm working on and how smooth the finish needs to be. After that, I'll apply a coat of carnuba-based wax. These are speakers, after all, and I am not going to be installing them in a church.
 
Are you hand sanding? I can't do anything, anymore, without the use of a powered tool, lol. It makes it easy, using a 1/2 sheet sander like the old B&D I used. I don't use any pressure or downforce, just guide it over the surface. The only reason I switch to the smaller, 1/4 sheet sander is that it orbits a lot faster so any sanding scratches disappear.

I've got a half-sheet sander that might be older than yours-- it's an all metal body Black and Decker! Also have a little Makita quarter-sheet sander. :thmbsp:

I'm curious about where I could find sandblasting paper and rubber blocks up here in Canada...

It's been taking me a hwile because school's really been battering me recently and I just don't have the time :no:
 
I've got a half-sheet sander that might be older than yours-- it's an all metal body Black and Decker! Also have a little Makita quarter-sheet sander. :thmbsp:

I'm curious about where I could find sandblasting paper and rubber blocks up here in Canada...

It's been taking me a hwile because school's really been battering me recently and I just don't have the time :no:
The Sandblaster paper, made by 3M, is in every hardware store, down here. The rubber block-sand paper cleaner is sold at Rockler Woodworking.
You can use regular garnet paper and it probably works 80% as well as the 3M stuff. A big old school rubber eraser would most likely work, as well. Another thing I do that seems to speed up the sanding process is to fold a sheet in half and put it on the sanders so that the working sheet is backed by another sheet. I slap the working sheet with my hand every now and then to smack loose the dust, also. That's about all there is to it.
 
Very nice Lance. I'm looking forward to the final results.
Thanks, Jeff.
I hope to have the outside of the cabs done tomorrow and maybe some grill frames cut. The cloth is going to be coming soon and I have to get new binding posts installed. These were the two weaknesses of the Studio Monitors, IMO, the weak-ass plastic pegs that held the grills and the brittle plastic binding posts. I like to restore to original, if possible, but no need to pass on the misery.
 
Looking great, Lance! I didn't know I was an inspiring kind of guy, but I'm glad you're reviving your 4313's. They look excellent! The walnut really is poppin'! :yes:

FYI - I posted some pics of the finished L36's...just one more grill to cloth, hopefully done with the project by tonight. :scratch2:
 
Watching paint dry.....

Cabs were masked and the baffle and back were squirted with Rustoleum Satin Black. I wanted a little sheen so that is the paint I chose. I know others have used Flat Black with satisfactory results.

Another Nobel Canidate: Inventor of the 3M paper masking machine. It took me all of about 5 minutes to mask the cabs.:yes:

Note: I removed all the glue at the foilcal location and cleaned all the black surfaces with denatured alcohol, prior to painting. I don't paint dirt anymore.
 

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I love the Rustoleum Satin as well Lance.

Grills are black?
Yup, the Rustoleum Satin came out perfect. I'll post some more pics, later. The grill cloth is supposed to be Dark Blue. I've got it coming from the Zilchlab so should be official JBL material.:yes:
 
Anxious to see how the JBL blue looks, Lance! I have Nate's Craptastic L100's sitting in que for my next JBL resto project and am considering trying the blue fabric for them.
 
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