View Full Version : Help with my JBL L300 "fuzzy" in one speaker.

01-13-2005, 07:54 PM
Does anyone have the speaker builder article they can send to me that details how to rebuild my L300 speakers? One speaker is very muddy sounding compared to the other. I think the 30 y/o crossover needs to be rebuilt. Any information anyone can send would be a huge help. I have owned these for almost 4 years and they are capable of making some great sound when they are working correctly. I could use some help here folks. :) I did reverse the amplifier leads to make certain it was the tube amp malfuntioning or the speakers. Sadly it is the one speakers sounding poorly. Do I access the crossover after I remove the 15" woofer? Thanks. If that is the case maybe I can remove the crossovers and then send them out to be rebuilt for me? After 30 years no doubt the capacitors are drying out. I would also like the speaker builder article to tune up the 2 tone controls on the front. Thanks for any help and advice! To my ears vintage and newer (like my JBL 4648a-8) are sleeper speakers. I also cobbled my Dad a 6' tall 2-way using the 4649a-8, JBL 2360A 31" x 31" biradial horns. I used a pair of tad td-4001 drivers in the jbl horns. My Dad's speakers are about the best I have heard. My Dad is severely hearing impaired. With these 2-way horn speakers he can hear female voices for the first time in 60 years. That made them worth the money to me for that alone. My cousin owns the top of the line B&W and my Dad's speakers sound better to my ears. Someday I want one the VERY large JBL pro version monitors to replace my L300. For now I just want the L300 back making good sounds in my apartment in Fall River, MA. I never overpowered the L300 and they have been babied by me. If anyone can scan and send the article to me my email address in jpchleapasnospam@verizon.net Be sure to remove the "nospam" from my email address before emailing me. Thanks for taking the time to read this! Best Regards, John Chleapas

01-13-2005, 08:22 PM
Hello John, have you messed with the L Pads by turning back and forth on the speaker that is the culprit?

01-13-2005, 11:01 PM
John I'm also from MA (Pembroke) and just had my L200b speakers professionally rebuilt and upgraded with 2405 tweeters and 3106 crossovers making them quasi L300 only differing with the shorter horns on the LE85. Prior to the overhaul by Pro Sound (Braintree, MA) they sounded poorly with mismatched/wornout diaphrams and cones, also the LX200b crossovers were original and tired. As Audiobeer suggested I'd start with the least expensive items, the L pads, mine were well worn and were replaced. I have to say the speakers now sound spectacular and worth every dollar spent on the refurbishing which wasn't cheap. I can highly recommend Pro Sound, John the technician who worked on my speakers was terrific to deal with and is highly skilled. Re removing the crossovers you are correct you will have to remove the 15" woofers and also the foilcals which can be damaged if not done with care. You will have to heat them up with a heat gun or lamp and use something like a very thin puty knife to lift them off. I think you would be amazed with the sound of your L300 speakers if you had them overhauled. I followed the advice of the senior members of this board and the experts weren't wrong and I now have some beautiful sound to prove it. Someday I hope to hear a pair of L300s to see how close my L200bs with 2405 tweeters sound to the L300.

01-14-2005, 02:11 AM
Hey there in Fall River! You got some "BIG GUNS" in your back yard! I'll bet when they "played" it was LOWUD!!!! You know what I'm talk'in about...

Big Mamie ain't kiddin' around when she shouts...

01-14-2005, 03:38 AM
Hello John, have you messed with the L Pads by turning back and forth on the speaker that is the culprit?

Yeppa. I have moved the L-pads on the speaker with little (no) effect. I really think it is the crossover(s). I know how good these sound with a good tube amplifier and even for a while a high quality SS receiver. They "sing" with a small tube amplifier of between 8 and 20 wpc. Since these are in an apartment I am not really able to crank them anyway. They are (or were) great for nearfield listening at lower volumes. The bass was always very good and the midrange was really nice to my ears. But what do I know? My stereo consists of mainly older tube equipment. I do have a pair of Klimo Kent mono blocks to hook up soon as I get the one speaker squared away. I think I will end up having both crossovers rebuilt. I am even considering triamplifying them. I have a few tube amps to do this with. The prohibitive expense is buying another Marchand XM-126 vacuum tube crossover. I got a 2-way unit for my Dad. The 3-way version is much more expensive.. So rebuilding the crossovers sounds more likely to me. Anyone have that article from speaker builder on rebuilding the L300 speakers? John C.

01-14-2005, 04:36 AM
Hi John;

the AudioXpress magazine published an article a year or so ago on rebuilding the JBL L-300. I have the issue packed away somewhere and will look for it when I have a chance:)


In the meantime, you could go to their site as they sometimes have back issues available.

Good luck;


01-14-2005, 06:21 AM
the AudioXpress magazine published an article a year or so ago on rebuilding the JBL L-300.
audioXpress September 2001

"JBL L300 Summit Renovation"

I am even considering triamplifying them. I have a few tube amps to do this with.Excellent idea! The designer of the L300/4333 highly recommends keeping as many passive components as possible away from the old ring radiators! ;)

scott fitlin
01-14-2005, 07:45 AM
I read your post, and in trying to help, I will say that properly rebuilding the crossovers is a good idea, and the L-pads, new ones will significantly improve the sound, particularly the transparency!

But I also notice something else, you say your using older tube gear, and I am wondering have you switched the speakers to the opposite channels of your amp, to see if the problem your having goes into your Good? speaker? Tube amps require tweaking every once in a while, maybe you need to re-bias your amp, maybe it needs some new tubes, just a thought, and should be looked at!

In the meantime there are guys here who will help you get those L300,s sorted out, and with a little time and effort, and a couple of bucks, you can get em even better than they originally were!


01-15-2005, 05:45 AM
I have the audioXpress (Sept 2001) on the L300 Rebuilt. PM me please if you'd like me to fax you a copy (sorry, I don't have access to a scanner).

I have a pair of 4333 that I'd like to tri - amp as well. I was thinking of getting a 3 way Ashly electronic x-over for this. My concerns are whether it'll be difficult to set the gain levels correctly across all drivers, and whether ground loop may be a problem with 3 amps. If anyone has any experience with this, I'd love to hear your thoughts. Thanks.


01-15-2005, 06:03 AM
Ok, I'll scan it and post it for you.

01-15-2005, 11:05 AM
Ok, I'll scan it and post it for you.Yes, please.

Others here are interested as well.... :yes:

03-03-2005, 11:04 PM
Thanks guys for the suggestions. I took off the rear access plate to the midrange horn. The black colored lug on the horn was loose. I simply pushed it in and it clicked and the horn is back on. These speakers rock. John C.

05-05-2005, 11:01 AM
Dougie did you find the mag and if so Giskard did you ever get to scan the article and post it? I do not think that they still have that issue for sale.


05-05-2005, 11:07 AM
He faxed it but it was unreadable. :(

05-05-2005, 11:14 AM
Giskard Thanks
I just sent Audioexpress an email to see if they still had a copy. There web site shows it but without a price. If I can get one I will scan it and upload it to a website.

Thanks Again

05-05-2005, 12:53 PM
Ok just got a reply and ordered 4 copies @ 7 dollars each shipped. Below is the email reply if anyone is interested.


Yes, the September 2001 issue is available. The cost is $7.00 postpaid in the US. You may call 1-888-924-9465 to order by credit card or send a check to Audio Amateur Inc., PO Box 876, Peterborough, NH 03458-0876. When ordering by mail, please be sure to indicate which issue you are ordering.

Best regards,

05-05-2005, 02:57 PM

28 dollars, 1 email and 3 posts later. Well at least I get the pictures.