JBl L150 restoration thread

[Will2225]

Hi guys, I've been working on some JBL l150s that are in pretty rough shape and I wanted to share some photos of the work I've been doing and update it as I go along.

I bought the speakers for 275, there was some water damage on the bases, the dust cover on one of the mids has been pushed in, one tweeter isn't working in one of the cabinets, and the other needs to be replaced or needs a new diaphragm. I've found one seller for the tweeter here, and have found some cheap Jbl's for a 100 bucks locally with two good 033 tweeters and aftermarket woofers.

I tried recapping the crossovers on the first speaker I'm working on but unfortunately the tweeter is still dead. I also replaced the l pads. I'm thinking it must be one of the resistors in the crossover. Any advice on trouble shooting this would be appreciated.

I also sanded down and patched some of the areas of damage on one of the speakers. I stained the speaker but I think I'm going to sand it again and patch the veneer. The front and back baffles were also spray painted black.

 

[Will2225]

Some photos of the work so far.

 

[Will2225]

Hi I'm hoping someone can help me figure out how to fix the crossovers on one of these speakers. I replaced all of the capacitors on the faulty crossover but the tweeter still doesn't work. I've tried switching tweeters but it's definitely a problem with the crossover. Any advice on how to figure out the problem? Should I check for continuity throughout the circuit?

 

[NAD80]

Will2225 found the SM on the speakers here. https://www.hifiengine.com/manual_library/jbl/l150.shtml. Has the schematic Just register to download. Check your wiring (could be a open?), check the solder joints. Verify all the parts are correct. Disconnect the tweeter and measure the resistance across it. Make sure the L-Pad works. Just for a start. One thing also are both crossovers identical?

 

[HTHMAN]

You will love those speakers. I had the mid driver go out on one of mine and it was one of the ceramic resistors that went bad. Check them out.

Edit. Just looked at the schematic. Probably not a resistor. Try bypassing the pot and see if that is the problem. Maybe just needs a good cleaning.

 

[Will2225]

Good news! I ended up going home early from work today and decided to give it another go trying to figure it out. I checked continuity throughout the crossover and was a bit stumped because it all seemed to check out. (First time I've done this by the way, but pretty simple). I think checked the actual metal tabs that the wiring connects too and sure enough two of the tabs didn't connect with the joint they were connected too. Must have been a cold solder joint. I resoldered them, checked continuity, all good. I also replaced the two 6uf caps while I was working on them. They sound excellent now!! I've only been working on one speaker so far and it now sounds so so much better than the other one. I recapped the crossover with dayton film caps, plus I replaced the l pads with new ones from parts express. It sounds great!

 

[Will2225]

You will love those speakers. I had the mid driver go out on one of mine and it was one of the ceramic resistors that went bad. Check them out.

Edit. Just looked at the schematic. Probably not a resistor. Try bypassing the pot and see if that is the problem. Maybe just needs a good cleaning.

I'm very excited to get them in better shape! I lost a bit of steam working on the project but I'm going to get back to it now. I do really like their sound. The bass might be a bit too much for my apartment haha.

 

[NAD80]

Great work. Enjoy the speakers and the music. Now to get the other one done.

 

[Will2225]

Worked a bit more on the other speaker recently. Fixed the chips, sanded, painted front and back. I should have sanded down more of the extra wood filler as it left a bit of a mark.

Had a bit of trouble getting the stain to look great on the top but I'm going to leave it as is for now. I thought I ruined the top but I ended up wiping off a lot of the second coat I did on top and it looks okay now, not perfect but better than what it looked like before.

 

[Will2225]

Tried my hand at fixing the speaker grills today. One of them is an okay shape but the other was terrible. I tried to fix the one with the broken segments today using paint stirring sticks and hot glue. A little jankey to be honest and not the ideal fix in any way but it was kind of fun. I had some left over speaker grill cloth from my last project that I used.

Last time I reupholstered a grill cloth I used spray on contact cement. This time I used a hot glue gun and found the experience much easier, especially when doing the corners as the hot glue allows you to make quick little changes.

In hindsight I wish I had ironed the cloth before I used it and maybe put more work into hiding the fixes for the frame, but oh well. They were bargain basement speakers anyways so it's been fun messing around on them.

 

[Will2225]

So I'm a bit perplexed. One speaker clearly sounds louder than the other. I've tried switching them from left to right and one speaker definitely sounds louder.

I swapped the mids because I thought that might be causing it but it stays with the speaker. I've made sure the cabinets are air tight.

Could it be a poor solder joint, wiring problem, or something to do with the l pads?

Any advice on trouble shooting this? It's kind of crazy how much louder the one speaker sounds in comparison. I'm thinking it might be the l pads

 

[jfine]

You can bypass the Lpads to see if the volume level is the same between speakers without them, I forget which 2 wires to jump but you can google it.

You said the xovers were faulty, what was wrong? The yellow mylars rarely need replacing. Even the old metal electrolytics seem to work, even though they're likely out of spec. I've seen these xovers suffer heat damage, probably from under powered amp. Right underneath the sand resistors on the bass circuit. That kind of abuse probably takes out the tweeters too.

I've had similar issues with mine. It seemed to me that with all the spade connectors on the xover that sort of snap on but then are sort of a little loose anyway, and the circuit board tracings, led to inconsistency. But, you also need to measure the 033's with an ohm meter, they should be around 4 ohms. I had one that was quiet but still worked, measured up around 50 ohms if I remember. 033's seem to fail, maybe because of clipping from weak amps. Might as well measure all the drivers.

I ended up using my own board and wiring all parts directly, using very good quality wire from soniccraft. I also replaced the sand resistors with mills (not expensive at all), and went with sonicaps for the bass circuit, (used to be electrolytics I see yours have been replaced too), mundorf caps for the highs and jupiter caps for the mids.

Then when I got them to sound like I wanted adjusting the Lpads, I measured the Lpad and replaced it altogether with mills resistors. Lpads are usually cheap metal crap inside that the signal goes thru anyway, and I got tired of the eventual noise.

Cardas speaker terminals and nice speaker wire to amp, when you turn these up they can R&R.

 

[Will2225]

You can bypass the Lpads to see if the volume level is the same between speakers without them, I forget which 2 wires to jump but you can google it.

You said the xovers were faulty, what was wrong? The yellow mylars rarely need replacing. Even the old metal electrolytics seem to work, even though they're likely out of spec. I've seen these xovers suffer heat damage, probably from under powered amp. Right underneath the sand resistors on the bass circuit. That kind of abuse probably takes out the tweeters too.

I've had similar issues with mine. It seemed to me that with all the spade connectors on the xover that sort of snap on but then are sort of a little loose anyway, and the circuit board tracings, led to inconsistency. But, you also need to measure the 033's with an ohm meter, they should be around 4 ohms. I had one that was quiet but still worked, measured up around 50 ohms if I remember. 033's seem to fail, maybe because of clipping from weak amps. Might as well measure all the drivers.

I ended up using my own board and wiring all parts directly, using very good quality wire from soniccraft. I also replaced the sand resistors with mills (not expensive at all), and went with sonicaps for the bass circuit, (used to be electrolytics I see yours have been replaced too), mundorf caps for the highs and jupiter caps for the mids.

Then when I got them to sound like I wanted adjusting the Lpads, I measured the Lpad and replaced it altogether with mills resistors. Lpads are usually cheap metal crap inside that the signal goes thru anyway, and I got tired of the eventual noise.

Cardas speaker terminals and nice speaker wire to amp, when you turn these up they can R&R.

You definitely sound like the right person to talk to about upgrading these. I might try to do what you did with replacing the l pads with resistors. Plus I've been looking at cardas speaker terminals. I'd really like to get these into the best shape they can be sound wise. One speaker sounds fantastic.

I can't quite find the information on the right way to jumper the speakers without the L-Pads but I'll Keep looking.

I think this morning I'm going to pull the crossover and reflow the solder joints while adding more solder. I did this on the other board but on this one I just reflowed the joints quickly and didn't add any solder, maybe that will make a difference.

The only thing bad with the crossover was that it had a cold solder joint that made the tweeter don't work. I will measure the drivers too while I'm working on them today.

I've also been considering rewiring mine with better quality wire. Out of curiosity do you have a thread on building the new crossovers for yours? I would definitely like to try to emulate your build.

 

[Will2225]

Oh I figured out how to jumper the connections. It's just between two and three labelled connectors where the l pads wiring connects

 

[z-adamson]

Bypass the lpads completely until you get them working right.

Reflow all solder joints in the xover...put flux to the joint, heat the joint up till the solder melts and add a small amount of new solder.

 

[Will2225]

Bypass the lpads completely until you get them working right.

Reflow all solder joints in the xover...put flux to the joint, heat the joint up till the solder melts and add a small amount of new solder.

I'm going to try this tomorrow. I bypassed the l pads and I think the issue isnt in the l pads. I'll try reflowing solder joints with flux soon. I'm also going to see if swapping the passive radiator makes a difference as the one on the bad speaker needs new gaskets.

 

[Will2225]

Bypass the lpads completely until you get them working right.

Reflow all solder joints in the xover...put flux to the joint, heat the joint up till the solder melts and add a small amount of new solder.

I did this today, and it did the trick! Both speakers now sound excellent and are equal in volume.

The one thing I have to figure out is how to fix one of the passive radiators. It doesn't need new foam but the soft outer ring is a bit messed up. I tried fixing it with a replacement part but it wasn't quite oem and looks different, plus I'm not sure if I did it right. Still though, I'm making progress.

 

[Will2225]

You can bypass the Lpads to see if the volume level is the same between speakers without them, I forget which 2 wires to jump but you can google it.

You said the xovers were faulty, what was wrong? The yellow mylars rarely need replacing. Even the old metal electrolytics seem to work, even though they're likely out of spec. I've seen these xovers suffer heat damage, probably from under powered amp. Right underneath the sand resistors on the bass circuit. That kind of abuse probably takes out the tweeters too.

I've had similar issues with mine. It seemed to me that with all the spade connectors on the xover that sort of snap on but then are sort of a little loose anyway, and the circuit board tracings, led to inconsistency. But, you also need to measure the 033's with an ohm meter, they should be around 4 ohms. I had one that was quiet but still worked, measured up around 50 ohms if I remember. 033's seem to fail, maybe because of clipping from weak amps. Might as well measure all the drivers.

I ended up using my own board and wiring all parts directly, using very good quality wire from soniccraft. I also replaced the sand resistors with mills (not expensive at all), and went with sonicaps for the bass circuit, (used to be electrolytics I see yours have been replaced too), mundorf caps for the highs and jupiter caps for the mids.

Then when I got them to sound like I wanted adjusting the Lpads, I measured the Lpad and replaced it altogether with mills resistors. Lpads are usually cheap metal crap inside that the signal goes thru anyway, and I got tired of the eventual noise.

Cardas speaker terminals and nice speaker wire to amp, when you turn these up they can R&R.

Could you send me a link to which cardas binding posts you'd recommend? I like to use banana plugs. Also, any thoughts on upgrading the internal wiring? Or replacing the cabinet stuffing? On one speaker the stuffing seems to be falling off the side a bit.

Also I replaced all of the caps with dayton films. They sound great to me but how much of an investment would it be to build whole new crossovers?

Any other thoughts or links on fixing these up would be great.

 

[z-adamson]

I did this today, and it did the trick! Both speakers now sound excellent and are equal in volume.

The one thing I have to figure out is how to fix one of the passive radiators. It doesn't need new foam but the soft outer ring is a bit messed up. I tried fixing it with a replacement part but it wasn't quite oem and looks different, plus I'm not sure if I did it right. Still though, I'm making progress.

Since you bypassed the lpads and got them working right, you will probably want to install some fixed resistors to pad the mid and tweeter......unless you like it as is. See the pic. I bypassed the lpads and added fixed resistors. Lpads are always bad in my experience. Fixed resistors is the way to go.

 

[Will2225]

Since you bypassed the lpads and got them working right, you will probably want to install some fixed resistors to pad the mid and tweeter......unless you like it as is. See the pic. I bypassed the lpads and added fixed resistors. Lpads are always bad in my experience. Fixed resistors is the way to go.

View attachment 2005874

What are the values of the resistors you used and which brand? I'm pretty happy with the sound quality now to be honest but I sold my Cornwall speakers and these are my main ones at the moment so I want to make them the best they can be. I'm more interested in changing the internal wiring to a higher grade and upgrading the binding posts (even though I did replace them with banana plugs).

I did replace the l pads entirely with new parts from parts express but I can see the logic that bypassing them entirely with just resistors at a fixed value could make an improvement.