I truly admire the work you have done to upgrade the JBL L100 Loudspeaker. It’s sort of like you’ve given an old man a new heart. I am retired now, but I worked in the audio/consumer electronics manufacturing industry for forty years – from 1960 – 2000. During the 1960’s I was Vice-President of Engineering Administration at JBL. I am not an engineer – but I did direct the L100 development program. L100 Design Engineer Ed May was a very dear and close friend. I coordinated the work of industrial design consultant, Arnold Wolf – who, with Doug Warner, was responsible for the visual design. Arnold later went on to become President of JBL and my boss. Larry Phillips created maybe the best audio promotion program ever: “Wednesday for Trombones, Thursday for Drums.” Years later, when I was introduced to Mark Levinson engineer, Tom Colangelo – Tom – smiling when he heard about my past JBL work experience, simply smiled and spoke that now famous marketing phrase. The best L100 story “never told” is that of JBL draftsman/audio enthusiast Carl Davis from Ottumwa, Iowa. Ed May told us all that microphone wind screen foam material would make an acceptable grille material. Arnold Wolf gave us stunning designs. The problem was that the foam industry was basically the packaging and filtering industry. Pressure cutting foam tolerance was about +/- .25 inch. No foam vendor could meet Arnold’s design requirements. Carl Davis, without degree, without assignment and working on weekends – was the first – in the entire industry – to discover that foam could be hot wire cut – and with the required precision. The L100 project had lingered more than six months in limbo while we struggled with the grille design problem. Meanwhile, the L100 market got off to a head start when studios began ordering 50 to 100 pairs of walnut 4310’s. We all new an unauthorized distribution process was under way. 

Thanks for giving me a reason to look back, Jim Barthell

20-08-2011
I've already sent my thanks once, but I still shake my head.
Soooo much better......John Drozdoff, Vancouver, Canada

21-02-2011
John/Canada:
Hi Troels, I finished installing my JBL L100 crossover (plus cabinet damping upgrade) last night, in Vancouver, Canada.
I am thrilled! The sound is wonderful. Thanks for making the product available. John Drozdoff

27-01-2010
Randy/US:
Hello in Denmark! I went to parts express for the L100 x-over upgrade per your suggestion. I really was pretty happy with the sound of my 4311B monitors, with a few exceptions, and bought the upgrade kit not knowing quite what to expect.  I had a great time assembling the kits, and while the speakers were down, cut up the cabinets and did a gorgeuos can't tell I was there job of mirror imaging the components.
Perhaps  most of the credit needs to be given to the crossover design and superior parts, but I now have a system in which the speakers have just disappeared.  I can see them, but wow, not there, just layers and layers of vocals and instruments. I now have a wall of music! !!
I have over the years been thru electrostats, Magnepans, big speakers, little speakers, and much in between, and nothing ever this pleasing overall.  Thank you Mr. Graveson, and staff,  I am as amazed as I am delighted with your talents.  There are true surprises out there, and anyone having skeptism or price issues, should talk to me about your offerings. {It did open up the mids and highs per the instructions, and somehow none of my amps open these speakers up the way my Mac Mc2500 does. Must be some magic there, wow!}
Many many thanks and very best regards,  Randy Pierce, Colorado Springs, Co.

04-12-2009
Victor/Hong Kong:
Hi Troels, Ihave ordered your modified crossover a year ago and the result is amazing! The mids and highs are more balance and transparency is significantly improved. It handles wide range of music and female vocals are magificant. I am also very happy that it also performs well for classical music. I love it very much and still enjoying the modified L100 now with my 100W hybid amp.

My L100 is bought from 2nd hand and the cabinet is nearly broken so I would like to have it renewed according to your lovely new cabinet design.

Since I am not good at wood work and with no tools, I would like to have the new cabinet built by carpenters instead of myself. I am not sure the size/diameters/rebates of the speaker units  are and not sure to tell the carpenter the exact outer and inner diameters and the rebates. I try to measure it myself but I am not sure if it is correct or not and I dont want to have it wrong. My carpenters are far away from my house and it is difficult for me to take the speakers to him and let him try and test the diameters and size of the rebates.
I have tried to search it from internet or JBL vintage forums but no infomation for the diameters/size are found. Would you please let me know how large should I tell my carpenter that the tweeters/mid/bass driver outer and inner diameters/rebates for correct cutting? Since both tweeter/mid and bass will be flush mounted, the exact size of the truncated mid frame and the square tweeter faceplate is important.
Thank you again for your excellent design and I look forward to your reply soon. Best regards, Victor/Hong Kong

Gilles/FR:
Thanks Troels !
I found my mistake. The JBL are rocking now. I think the sound is definitely better in the upper midrange and the fantastic JBL bass is still present. Listening to my Gainsbourg LPs is a pleasure. Your crossovers are really worth the price and the work. Regards, Gilles

Brian/US:

mail #1:
YAHOO!!!!!!!! I owe you dinner!!!!!
First- after using my big 4333's for years I did not realize how much they lacked midrange- only makes sense as there is not a mid component in the cabinet but..... the low end on those L100's- how ya do that from a 12" cone????? So smooth- and so nice to have mids back (so important on vocals) I took the glass out and put that poly stuff in too!!! I do not miss those big 4333's at all- I am in love with my reborn L100's- This week i am making the stands you suggested on the 5 degree tilt too- Pictures when all done going to Troels . Are you coming to the east coast for vacation this year- I hope so- How else can you cash in a free dinner here in beautiful Pennsylvania!!!!!!! See Hershey, PA see the chocolate factory, broadway show in NYC, etc., etc- c'mon go for it!!!! Its only money- hahahaha- We'll put ya up- you just need airfare to PHL!!!

Mail #2:
Made the stands to 5 degree tilt   (maple)  as per your suggestion over the weekend-stained and finished!!!! your KOOL  crossover in  -I'm in audio heaven!!!!!!! THANKs!  Brian.

Click image to go to PE website.

Volker/Germany

#1 mail:
Hello Troels, Today I finished building the JBL L100 Recreation I bought from you. I am very pleased with the result, but there is a problem with the second 123A. The bass "knarzt" - how can i say it in English? When playing music, it makes an ugly noise, and if I move the membrane forward and back without playing music, it makes a noise like "krrzztt". Can you imagine what the problem is? Do you have any advice for me what to do - how can I repair it? So far, even with that annoying fault, this speaker provides a very pleasant sound, and is so easy to listen to. I am looking forward to the moment when the bass is repaired, so I can enjoy it even more. With this mail I will send you some pictures of the building process. Regards, Volker

I suggested Volker that the unit had been fastened too tight as the voice coil gap is very narrow and tightening the screws too hard might bend the chassis and cause voice coil rubbing - and this turned out to be the case.

#2 mail:
Hello Troels, Now I know why the voice coil is rubbing. It was my mistake. Like you said, I tightened the screws very hard, and somehow twisted the chassis.
What a pity. Didn't think of something like that. When I took it out, the voice coil was still rubbing. So I ruined the chassis. Sorry, Troels. I will have to look after a new 123A. Do you happen to have a  third one you can spare? Pity, pity, pity. Regards, Volker

I suggested Volker trying to bend back the chassis by screwing the unit onto an plane surface and add small spacers here and there to see where the pull/perssure should be.

#3 mail:
Dear Troels, I did as you proposed, put the chassis on a straight piece of MPX and tried to bend it back into shape, so that no more voice coil rubbing happens. After an hour or more I finally managed to achieve a free cone movement except the last few mm of excursion. Then I put the chassis bach into the enclosure, and it works without any flaw with music now. These speakers play music in a way I like very much. It is an ease in the sound that makes it a lot of fun to listen to. In a time to come, when our children (5 and 7 years now) have grown up a little more, I hope to spend more time listening to music. Thank you very much for development, and for your help during the building process. Volker

Thanks Volker for your feedback and I'm pleased it all worked out. The lesson learned here is valuable for other builders so I have added all your notes. The cabs you have built look just great! Baltic birch - my favourite material.

John/US:
Troels, I want to thank you for the crossover kits I received.  I just got around to installing them, and have to say they have made a significant improvement regarding the performance of my L100s. I initially installed one of the crossovers to compare the upgraded speaker against the original, and the improvement is significant! The tweeters sound much, much better. That's not the only improvement, but that's the most noticeable.  I found while comparing the two speakers the treble on the original struck me as garbled, and non-defined. I hope that there are others out there that buy your crossover and realize the potential of these speakers. 
I am impressed! Thanks, John.

Stephen/UK:
Hello Troels, I thought I'd get back to you as I've now had a chance to re-test the crossovers and I owe you an apology - they're wonderful. However the issue causing the "bad sound" was neither the speakers nor the crossovers but my amplifier!! - I took the speakers to my local expert and he tested them on another amplifier and wow they sounded great, so we tested my amplifier and to say it is ruined is an understatement - the technician said it should go into the scrap bin.  I've therefore invested in a new amp and the result is fantastic.
So, thank you for a wonderful product and of course your expert advice. Kind regards Stephen.

Stesses/Belgium:
Hello, I was very pleased with the crossover kit for the JBL L100 and I want to inform if you have a kit for the pioneer HPM 100 speaker system.
Thanks, B. Stesses/Belgium.