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View Full Version : L300 Summits that need a little work



intotubes
02-20-2010, 02:00 PM
I stumbled on a pair of L300's and brought them home. They are a bit rough but able to be restored I think. One of the HF drivers was not working, measured 36 ohms DCR. I took the cap off and measured again - 6.1 ohms. Must have been a bit of corrosion. Cleaned off the dust and put them back together and gave a listen. Ugh!
One MF driver is toast. The other doesn't sound so great either. So I took the cap of the offending driver and found the diaphragm broken in many places. Obviously these have been abused. Clipped to destruction I'd say.
Anyway here are some pics. Missing the trim pieces on the top. Any repair ideas for that? Grill cloth is filthy and pilled. Not sure it can be resurrected. May have to study the Zilch grill fixing thread. It has the black grills but I s'pose I could use JBL blue. I think that is a stock color for these.
They have consecutive serial numbers and it looks like the woofers have been reconed. A little sloppy around the dust cap but otherwise looks good.
The LE85 says 8 ohms but the replacement 'phragms are 16 ohms. Can anyone shed some light on that?
BTW I found some used drivers for 6 bills a pair. Heck that is the same price as diaphragms. I may pull the trigger on that. All in all I have about a grand banked to restore these. any help, advice, or tips before I do irreversible damage will be appreciated.
-Mark

http://i257.photobucket.com/albums/hh225/idustrialsupplies/JBL%20L300%20Summit/DCP_5368.jpg

http://i257.photobucket.com/albums/hh225/idustrialsupplies/JBL%20L300%20Summit/DCP_5367.jpg
http://i257.photobucket.com/albums/hh225/idustrialsupplies/JBL%20L300%20Summit/DCP_5362.jpg

http://i257.photobucket.com/albums/hh225/idustrialsupplies/JBL%20L300%20Summit/DCP_5361.jpg

http://i257.photobucket.com/albums/hh225/idustrialsupplies/JBL%20L300%20Summit/DCP_5363.jpg
http://i257.photobucket.com/albums/hh225/idustrialsupplies/JBL%20L300%20Summit/DCP_5387.jpg

As you can see one is missing the back door. I'll need to somehow fabricate a new one. But they are more than just a door. It supports the MF driver.

http://i257.photobucket.com/albums/hh225/idustrialsupplies/JBL%20L300%20Summit/DCP_5389.jpg

Doc Mark
02-20-2010, 02:22 PM
Hi, Mark,

Congrats on securing a pair of L300's! As another '300 owner, I think you will love them, once they are restored back into good condition! You've got all the bits, and the rest is time and dollars. As to the midrange diaphragms, you will have to look around a good bit, me thinks, but once you get those LE-85's back to the way they should be, they are very nice, indeed. I might suggest that you check out your crossover, too. Lots of ways to go, there, including going for the whole banana and building what I think are called "CC crossovers" for your new L300's. In any case, if yours were overdriven, it's possible that the crossovers suffered, too. So, check them out, and see how they turn out. Best of luck to you on your project. Restoring your L300's is a very worthy goal, and if you do a bit of looking around in past posts here at LH, you will see some simply stellar work has been done in that regard!! Do yourself a favor and spend the time to seek it here here. You won't be sorry. Take care, and God Bless!

Every Good Wish,
Doc

demon
02-20-2010, 02:27 PM
...and if you do a bit of looking around in past posts here at LH, you will see some simply stellar work has been done in that regard!! Do yourself a favor and spend the time to seek it here here. You won't be sorry.thats a good one:
http://audioheritage.org/vbulletin/showthread.php?t=24773
i think the L3oo are VERY stylish!
(but i never heard em)
cheers,
mikey

intotubes
02-20-2010, 05:53 PM
I wonder if anyone can address the LE85 diaphragm issue, 16 vs 8 ohms? Will the 16 ohm diaphragms work in my "8 ohm" drivers?

Earl K
02-20-2010, 06:49 PM
I wonder if anyone can address the LE85 diaphragm issue, 16 vs 8 ohms? Will the 16 ohm diaphragms work in my "8 ohm" drivers?

- AC impedance is a curve , & one can pick any point on that curve and still be technically accurate in the labelling ( if one wants to be stubborn )


- I won't bother to spell out in detail JBLs' policy of mislabelling some things while deciding to properly label others, except to say that they did.

- The following is from an official JBL Customer Service Department publication called ; " Compression Driver Test Specifications " ( circa 1983 ) .
- ( "DCR = DC Resistance" )


LE75 , DCR ( min to max ) , 5.4 - 6.6 (ohms) , "Nominal Impedance" = 16
LE175, DCR ( min to max ) , 5.4 - 6.6 (ohms) , "Nominal Impedance" = 16
D175 , DCR ( min to max ) , 5.4 - 6.6 (ohms) , "Nominal Impedance" = 16
175 , DCR ( min to max ) , 5.4 - 6.6 (ohms) , "Nominal Impedance" = 16
2410, DCR ( min to max ) , 5.4 - 6.6 (ohms) , "Nominal Impedance" = 16
2420, DCR ( min to max ) , 4.8 - 5.8 (ohms) , "Nominal Impedance" = 16
275 , DCR ( min to max ) , 4.8 - 5.8 (ohms) , "Nominal Impedance" = 16
LE85 , DCR ( min to max ) , 4.8 - 5.8 (ohms) , "Nominal Impedance" = 16
2421B, DCR ( min to max ) , 5.7 - 6.9 (ohms) , "Nominal Impedance" = 16
2425J, DCR ( min to max ) , 5.7 - 6.9 (ohms) , "Nominal Impedance" = 16

2421A, DCR ( min to max ) , 3.6 - 4.4 (ohms) , "Nominal Impedance" = 8
2425H, DCR ( min to max ) , 3.6 - 4.4 (ohms) , "Nominal Impedance" = 8

- Ideally, when looking for a substitute diaphragm ( because the original is NLA ) one wants to match the impedance curves as closely as possible .
- Failing having those curves on hand , one should strive to at least get the DCR values as close as possible ( within 1 ohm is nice ) .

Anyways:

- The 2421B replacement diaphragm should have a close enough DCR ( @ 6.3 ohms ) to your original 2420 ( le85 ) diaphragms . Plus they are all aluminum and the "weight of the dome & coil" will be correct . The 2410 / LE175 has a lighter weight, dome & coil assembly ( according to the book ) / thus not recommended for substitution into the more powerfull magnetic assemblies of the le85/2420 or 2425 drivers .

<> cheers

intotubes
02-21-2010, 07:06 AM
Thank you!

As always, this is the most technical source of info on the web for JBL/Altec.

As far as cosmetics, I was thinking of making new trim pieces for the top and then sanding down the veneer in order to finish it together to match. Any ideas of what ind of veneer was used, is it available, can I match it for the trim? What is the finish?
I'm no cabinet maker so this will be tough for me.

Earl K
02-21-2010, 07:44 AM
Thank you!

Your welcome !

One Note :

- Make sure that JBLs' modern replacement diaphragm actually has a DCR value in the range I posted ( I see one on eBay right now that appears to be out of spec according to some printing on the styrofoam packaging ) .
- The info I posted is 27 years old and JBL may have changed the DCR values for some of these older diaphragms ( though I doubt it ) .

- ie ; Don't buy till you are sure it'll work .

>< cheers

CountD
02-21-2010, 08:29 AM
Awesome project. I would say talk to many people before sanding and or/refinishing. There are lots of knowledgeable people in this area. For example, I have talked to some local restorers on how they do things - and as you know everyone does it differently. I would take a few moments before jumping in because it looks like you have a real sweet foundation with which to start and sometimes you can get ahead of yourself. Nice find and rescue.

macaroonie
02-21-2010, 11:42 AM
Missing the trim pieces on the top. Any repair ideas for that?

I cant see the condition of the sides of the cabs but basically if you hunt around your local lumber merchants you should be able to score a small piece of WALNUT that can be grafted into place. You will need a small sharp plane to clean up and fit in a tidy fashion.
You might wish to check out my (long ) thread on building L300 style speakers as there are details in there that will help you no end.

http://audioheritage.org/vbulletin/showthread.php?t=17238&highlight=backyard

Paticularly of interest posts 65 - 68. I post veneered ie after the cabinet construction and it was my first effort and it all came out very well indeed. I would guess that your veneer is a little tired if the other aspects of the cabinets is anything to go by. Do a search here for veneer and you will get loads of info. There are plenty of iron on veneers available that make the job a breeze.

good luck

intotubes
02-25-2010, 05:35 PM
I called two JBL authorized service centers in Denver about rebuilding my LE-85's and 077's. Both were primarily pro-JBL dealers. One said he would do it but had to buy parts from NY. I'm a little nervous about taking them to JBL pro service centers who may not be experienced in these older drivers.
Who does everyone else take their legacy drivers to? Ship them to CA? Do it yourself?

HCSGuy
02-25-2010, 05:55 PM
If the service center is new, I'd be worried. Otherwise, they have probably seen dozens of your drivers, just with different model numbers as the LE-85 was sold to pros as a 2420 and the 077 as a 2405, then later as a 2405H. Maybe you should require that the tech be at least 50yrs old?

Mr. Widget
02-25-2010, 06:13 PM
I called two JBL authorized service centers in Denver about rebuilding my LE-85's and 077's. Both were primarily pro-JBL dealers. One said he would do it but had to buy parts from NY. That's the wrong answer.

He should use JBL Pro parts from Northridge. I guess, you told him you had some consumer speakers and he assumed they needed consumer parts... these old JBLs actually use Pro parts. Unfortunately the LE85/2420 diaphragms are long gone... the high impedance 2421B diaphragm is still made and is the best replacement. JBL part#D16R2421. For the 077, you need JBL part#D16R2405.


Widget

louped garouv
02-26-2010, 01:43 PM
Who does everyone else take their legacy drivers to? Ship them to CA? Do it yourself?


if you are up for a scenic drive, there is a shop that is very well regarded in the Springs...

Audio Analysts
3286 N El Paso St.
Colorado Springs, CO. 80907
P. 719-632-8855
F. 719-632-3638
speakers@audioanalysts.net (speakers@audioanalysts.net)


worth a call IMO.

intotubes
02-26-2010, 01:56 PM
Yup, I saw the shop in the Springs on the list. Without prior recommendations I called the two closest to me. I will call the one you mentioned. It's reassuring having good word about a shop. I didn't get a good vibe from the two in Denver.

Thanks for the p/n's Mr. Widget.

OK, I called Al at Audio Analysts. If I have him do it I actually save $100 over paying list price and doing it myself! Super! Both MF drivers rebuilt by a service tech for less than $500. Both 077's for less than $300 (if they need it). These prices sound very reasonable. I hope I'm not breaking any rules by posting them.

intotubes
02-26-2010, 03:55 PM
Missing the trim pieces on the top. Any repair ideas for that?

I cant see the condition of the sides of the cabs but basically if you hunt around your local lumber merchants you should be able to score a small piece of WALNUT that can be grafted into place. You will need a small sharp plane to clean up and fit in a tidy fashion.
You might wish to check out my (long ) thread on building L300 style speakers as there are details in there that will help you no end.

http://audioheritage.org/vbulletin/showthread.php?t=17238&highlight=backyard

Paticularly of interest posts 65 - 68. I post veneered ie after the cabinet construction and it was my first effort and it all came out very well indeed. I would guess that your veneer is a little tired if the other aspects of the cabinets is anything to go by. Do a search here for veneer and you will get loads of info. There are plenty of iron on veneers available that make the job a breeze.

good luck

Thank you. I enjoyed your thread. It take away some of the trepidation I have toward veneering. My speakers only have a few small nicks on the edges and a bit of surface scratching. I was thinking of lightly sanding the veneer after the new walnut trim pieces are installed and finishing.
Have any idea how thick the original veneer is? Worst case, I'll fill the nicks and veneer over the top.

http://i257.photobucket.com/albums/hh225/idustrialsupplies/JBL%20L300%20Summit/DCP_5409.jpg

http://i257.photobucket.com/albums/hh225/idustrialsupplies/JBL%20L300%20Summit/DCP_5408.jpg

intotubes
02-26-2010, 04:36 PM
Well, I couldn't stand seeing these sit and wait for two new rebuilds so i hooked one up for a mono listening session with a Fisher KX-200 tube integrated.

Good Lord. :blink: Not sure what I expected but it sounds absolutely magnificent. Much as I hate to admit it, I think it fairly blows away my Model 19's. I know. I didn't think it could get much better. More bass, more sparkle and still golden midrange. I don't know what to think...

I think I better get those LE-85's in.

cosmos
02-26-2010, 08:59 PM
Well, I couldn't stand seeing these sit and wait for two new rebuilds so i hooked one up for a mono listening session with a Fisher KX-200 tube integrated.

Good Lord. :blink: Not sure what I expected but it sounds absolutely magnificent. Much as I hate to admit it, I think it fairly blows away my Model 19's. I know. I didn't think it could get much better. More bass, more sparkle and still golden midrange. I don't know what to think...

I think I better get those LE-85's in.

Good Lord, we have another convert! Step back and say "Yes" if you believe... :applaud:

Based upon the pics, I don't think your going to be able to "fix" your veneer.. I'd bet you end up re-veneering them.

Best of Luck. They are a prize worthy of your finest efforts.

intotubes
02-28-2010, 11:39 AM
I needed to remove the L-pads because I couldn't adjust the presence.

I had to remove the foilcal's from the L-pads in order to remove them - the presence (midrange?) pot knobs are both stripped. Now that I have removed the units I can see why. The presence pot is at least twice the physical size of the brilliance pot. They are both stiff and a bit hard to turn. Is this normal?

Is there a supplier of knobs out there? I hate to glue the knob on in case I ever have to remove the pot. If that's my only recourse I may simply leave the knob off.

I also found out that the foilcal's are extremely fragile and susceptible to marking from the putty knife I used. Although the marks are minor, they are noticeable. I will try to smooth them out but take heart in knowing there is a reputable supplier of replica foilcals as gleaned from a previous thread. At any rate I found the "correct" way to remove them easily and without ANY damage is to use a heat gun with a putty knife. They practically fall off.

Mr. Widget
02-28-2010, 01:15 PM
Is there a supplier of knobs out there? I hate to glue the knob on in case I ever have to remove the pot. If that's my only recourse I may simply leave the knob off.

I also found out that the foilcal's are extremely fragile and susceptible to marking from the putty knife I used. Although the marks are minor, they are noticeable. I will try to smooth them out but take heart in knowing there is a reputable supplier of replica foilcals as gleaned from a previous thread. At any rate I found the "correct" way to remove them easily and without ANY damage is to use a heat gun with a putty knife. They practically fall off.There are people who make reproduction foilcals and knobs. Before the reproduction knobs were available, I sourced them by buying some inexpensive JBL crossovers on eBay from L100s.

If you do a bit of searching you will find all that you need, including info on L-pad maintenance etc.


Widget

intotubes
05-25-2010, 04:25 PM
I tried a wood working friend of mine to make the back door I needed. He didin't have the time to get it done so after a month and a half I asked for the original back. He gave it back along with a piece of black walnut to make the top trim pieces. Great! but I still need the work done.

Asked another wood working friend if he could fab a single door and I gave him the original. "Sure", he said. I cannot believe the results. He made me TWO. They are as an exact replica as I could have hoped for. And now I have a spare!

He's going to make the 4 top trim pieces from the black walnut that I now have and I will give him the rest.

Finally, some progress. Check the pics. Pics are of the original and one replica.

brad347
05-25-2010, 05:14 PM
Awesome! Can't wait to see how this progresses.

Altec Best
06-07-2010, 11:50 AM
I too am looking forward to seeing your progress.I noticed you thought they sound better than your 19's Let me ask have you ever had the Crossovers in the 19's rebuilt.If not after changing the caps & resistors,make sure you bypass the ground lugs with wire connections,and have the L-Pads cleaned the difference was Night & Day difference completely blew me away in the sound Quality.

But I can't wait to see your progress on such an Awesome vintage speaker what could be better than having a pair of Model 19's and JBL L300's "What Else Could You Ask For" The best of both Worlds. ;)

AWESOME FIND !!!! :applaud: :bouncy: