View Full Version : L 300 summit hF response

09-27-2003, 06:40 PM
Seems I am experiencing some hF tinnyness from my system on both sides. Just had all drivers re-diamphramed, remagnetized, and reconed. mids and lows sound great. However, HF response seems tinny and somehow "dirty". I have manipulated the controls on the front panel to see if this frees up any oxidation that may have occurred. Looks like it is the Lpads. Any direction on what is the most efficient way to remove the Lpads??


Jim Griffin

Tom Loizeaux
09-27-2003, 06:49 PM
There's been a good bit of discussion lately on L pads; you might want to use the SEARCH button to see what you can find.
Generally the first thing to do is to spray a high quality pot clean/lube into these from behind and rotate them a bit to see if that helps the high end signals. RThey cn be replaced, but it can get a bit involved.
Try the cleaning and report back to us.


09-28-2003, 01:16 PM
Hey, Jim...

:wave: Welcome!

After you do Tom's bidding and post the findings, can you also add:

A) were the HF's fine before the reconing of the MF and LF?
B) did you yourself remove and re-install the transducers?
C) if so, did you reconnect all the wires correctly (i.e., not switch polarity)?

If the answer to A is "yes", I'm suspicious of phasing, as is my exiled role. :hmm:

With Tom, waiting....

(ps - removing L-pads can be tricky. That dang face-plate was installed with no forethought on removal)

09-29-2003, 11:27 AM
"ps - removing L-pads can be tricky. That dang face-plate was installed with no forethought on removal"

Your Authorized JBL Service Center knows how to properly service JBL loudspeaker systems ;)

10-02-2003, 10:48 PM
My thanks to those of you experienced JBL speaker owners who have given me tips on rectifying my L300 summit HF response. I attempted to clean the Lpads, and the response is still the same. I bartered these speakers with my dad's long time friend, so I didn't have much time with them before I began to spec them. My next step will be to switch the tweeters between cabinets, for the left tweeter has better response than the right, but both are able able to be cut off with the MF resonse turned all the way down. Is -3 then, the off position? I doubt it, so my next step will be to replace the Lpads.

My father owned and built from plans a JBL paragon which was enjoyed for 30+ years. I have owned a myraid of JBL's, including currently LSR 32s and 4735 sr IIs. I am a novice at this, and just enjoy the sound.

much appreciated again.

Jim Griffin

10-04-2003, 08:21 AM
Use Caig Laborotories products.
Deoxit D5 or Pro gold G5. spray in through the vents with the red tube or pop the metal back off and spray on the wire wound resistor. This is the only contact cleaner that I have found that works and it is extrememly good but expensive.