16 ohm 1" shaft L-Pad tutorial (L300 and others)

[elshout]

I have received help on this site many times from the kind members, so I thought I would make a return contribution. I have seen this issue raised many times.

I needed to replace the L-Pads in my JBL L300A speakers as the old ones were very scratchy and one of them would not even turn. It was locked in place. The problem is the 16 ohm L-Pads on the internet only have a 3/8” shaft. A 1” shaft is needed. So, here is the fix.

First I ordered, from Parts Express, 2 - 16 ohm 100 watt 3/8” shaft L-Pads: part number 260-261 and 2 - 8 ohm 100 watt 1” shaft L-Pads: part number 260-265.

See two pictures below:

[elshout]

The 100 watt 8 ohm and 16 ohm are the same size except for the shaft. The BIG news is that the shafts are interchangeable! (and the values of the respective L-Pads stay the same) So, here is how to do it. First, take a paint scraper or putty knife and gently pry open the 4 tabs on the top that hold the back in place:

[elshout]

With the back off, loosen the nut on the top that holds the shaft in place. Remove the nut and remove the shaft. (It helps to press the bottom of the shaft toward the L-Pad as you remove the nut, as the metal connector on the bottom of the shaft works as a spring against you when you first loosen the nut):

[elshout]

After you remove the 1” shaft from the 8 ohm L-Pad and the 3/8” shaft from the 16 ohm L-Pad, put the 1 inch shaft in the 16 ohm L-Pad, replace the nut and tighten the nut securely. (The gold colored shaft has a flat spot on it, make sure this lines up with the flat spot on the L-Pad before you apply and tighten the nut. This keeps he whole shaft from turning when you turn the knob) Then reapply the 16 ohm metal back and gently bend the 4 tabs back over the front to secure:

[elshout]

Now the Midrange will have a 16 ohm 100 watt 1” shaft L-Pad. There is not room on the board for 2 – 100 watt L-Pads, so I ordered a 8 ohm 50 watt 1” shaft L-Pad: part number 260-255 for the tweeter. The new 16 ohm L-Pad is a direct replacement using the parts that come off of the old 16 ohm L-Pad when you remove it. However, the 8 ohm 50 watt L-Pad has a longer shaft than the original 8 ohm L-Pad. So I added 1 new nut and the old nut to the 8 ohm shaft in addition to the original spacer to the shaft so the two L-Pad shafts would be the same length after mounting:

[elshout]

When mounting both new L-Pads, I used the flat washers on the front behind the new nuts prior to tightening to prevent the nuts from cutting into the mounting board. (The original L-Pads just had the nuts, and they were cutting into the mounting board):

[elshout]

Before and after.

[elshout]

Total parts used:
2 - 16 ohm 100 watt 3/8” shaft L-Pads: part number 260-261
2 - 8 ohm 100 watt 1” shaft L-Pads: part number 260-265
The 4 above are for the midranges

2 - 8 ohm 50 watt 1” shaft L-Pads: part number 260-255 for the tweeters


I hope that helps someone.
Scott

[Audiobeer]

Nice Thread! Thanks!