View Full Version : tuning passive radiators

09-03-2003, 05:41 PM
hi, is there a faq that describes how i can tune the passive radiators in my l-220s? i don't think the bass sounds quite right. thanks, dustin

09-04-2003, 06:31 AM
Here is the latest tuning information for the PR15C which is used in the L220 with the LE14A and LE14H.

09-04-2003, 06:32 AM
Here is the older tuning information for the PR15C.

09-04-2003, 06:36 AM
Here is the PR chart from 1977

09-04-2003, 10:01 AM
I always wondered about the math for those things.Thanks Giskard for answering a question that I always had. Kinda like discovering the meaning of life-ya-know ! Your knowledge is incredable. Best regards,Oldmics

Steve Gonzales
10-13-2004, 10:21 AM
I am amazed at the Quality and amount of information available on this site!. Thank you Giskard. The first pair I got my hands on were the L222's with beat cabs and the 076 ,L94/LE5-9 intact. I want to show the literal "basket case" LE14-H's and PR15c's.

Steve Gonzales
10-13-2004, 10:24 AM
The Pr15c's were bare baskets

Steve Gonzales
10-13-2004, 10:59 AM
The LE14H's and PR15c's needed alot of TLC and so in the meantime I hunted down some replacments and found them in Illinois so I traded a clean pair of ESS Heil Air Motion Transformers for some LE14A's and PR15c's and installed them in the L222's. Thanks to alot of determination and a"alittle help from my friends" I set out to restore the original drivers. I looked high and lo' far and wide and got so many confusing answers about the weights for the PR15c's and until Giskard just showed me the Light, didn't know that the PR15c was tuned with fiber discs! THANK YOU SIR!! The LE14H's looked like they been dragged face down on the road for a few blocks. My brother and I carefully used a belt sander to 'erase' the damage done to these fine drivers Luckily the flanges are quite thick and the metal is of high quality (JBL). I then set out to find the original cones. That wasn't easy.... After almost giving up on them a friend in NEW York and I were talking "JBL" and I mention that I would give my 'eye teeth' for some original LE14H cones and he says: "Oh I have had a pair of them sitting on a shelf for a long time that I couldn't use and just couldn't throw away"; "I'll put the them in the mail today" COOOOOL!!. I found a guy that owns MB Sound here in Bakersfield that was willing to install the cones and put new (correct) spiders on for a reasonable price and wa-la!

Steve Gonzales
10-13-2004, 11:01 AM
Here is a closer shot of the rehabed metal

10-13-2004, 11:13 AM
Originally posted by Steve Gonzales
I want to show the literal "basket case" LE14-H's... Whoa... Spider and voice coil - that's all, that's it? Wonder what the Fs of that is...? :spin:

Steve Gonzales
10-13-2004, 11:37 AM
The PR15c's were a different story. I bought the a copy of the JBL tech note about passive radiators on ebay and just assumed that there was no difference between PR15's and PR15c's. I really had called all over the country trying to find information and parts to restore the 15c's so I just 'winged' it. I took a hard bound book that ironically is titled "how to fix almost anything" that I picked up at a yard sale and cut two approx. 4" circles out of the hard cover- this material appears to be the same as the original- and used epoxy to bind a "T"nut in the centers of the new circles and also bent the 'claws' of the t nut over on the other side too. I didn't want to take a chance on the T nut pushing through accidently so I mounted it on the outside of the circle. This left a gap when the weighs were snugged up against the circle so I made a shim out of cardboard to take up that space. I took the whole thing to the owner of MB Sound and he Reconed the PR15c's and attached my new fabed parts. Here is a shot of the finished product.

10-13-2004, 12:00 PM
The PR15C recone kits are available but JBL is quite proud of them. I haven't bothered to order any for my one remaining PR15C.

Steve Gonzales
10-13-2004, 12:06 PM
Thank you again for this wonderful information!!! I wonder if anyone has some of those tuning discs? I guess you have provided the info to enable me to make them but it would be nice to have originals.