has anyone redone the crossover on JBL L26?

[bolero]

I have a pair of L26's and I saw this webpage where he talks about redoing the crossover:


http://www.troelsgravesen.dk/JBL-L26.htm

I like the sound of my L26's except they have a nasty spike in the ( high mids? ) that pops out occasionally on high vocals/gtr/sax etc

since they are old I was going to replace the caps etc anyway; reading his page it seems it might tame the highs a bit

wondering if anyone else has done this, and if so, your results?

thx!

ps I also found this thread via search: but he is just replacing the caps rather than the whole x-over

http://www.audiokarma.org/forums/showthread.php?t=142355

 

[SoundOfSound]

I have some L26s and I was also considering a recap.

I'm considering replacing the .5 mH iron core inductor in the tweeter circuit with an air-core one. This supposedly helps reduce distortion and is how most modern speakers are built. I still have to verify the DCR of the original coil.

If the 8 uF cap is out of spec or damaged then new caps will help you out.

http://www.parts-express.com/jantzen-050mh-20-awg-air-core-inductor-crossover-coil--255-036

http://www.parts-express.com/jantzen-82uf-400v-crosscap-capacitor--027-930

http://www.jbl.com/resources/Brands...atedDocuments/en-US/technicalsheet/L26 ts.pdf

No affiliation

 

[bolero]

thanks for the links!

:thmbsp:

 

[bare]

Here you Go.. Fill yer Boots :yes:
http://www.troelsgravesen.dk/JBL-L26.htm

 

[bolero]

Here you Go.. Fill yer Boots :yes:
http://www.troelsgravesen.dk/JBL-L26.htm

yep, I included that URL in the original post, was wondering if anyone else had done it :thmbsp:

 

[bare]

Ooops sorry ...not an overly adept reader.
Not done that Troels' circuit but have done others of his in the past.
His circuits are solid.. they do Exactly what he claims they will do.
Try it ?... the instructions are clear and concise. The results are graphed.
Not much of a risk and it certainly couldn't worsen the oem crossover of those speakers.
My only criticisms (if even that) are of his sole use of Jantzen products.. But they they do supply him for gratis so there is reason / logic in it.

 

[SoundOfSound]

Ooops sorry ...not an overly adept reader.
Not done that Troels' circuit but have done others of his in the past.
His circuits are solid.. they do Exactly what he claims they will do.
Try it ?... the instructions are clear and concise. The results are graphed.
Not much of a risk and it certainly couldn't worsen the oem crossover of those speakers.
My only criticisms (if even that) are of his sole use of Jantzen products.. But they they do supply him for gratis so there is reason / logic in it.

What is wrong with Jantzen produts? :scratch2:

 

[bolero]

well I finally got around to opening mine up, the tweeter has stopped putting out any sound so I suspect the cap is dried out

( have not been running them loud, so I doubt I blew it )

picked up a pair of 8 uF 450v caps today to test

however, the x-over board is stapled & glued onto the front of the inside: nearly impossible to get at!!

lots of glue holding it on, too...had a go with a flathead screwdriver to try & pry it a bit, but no luck

any ideas?

pic here: I stuck my phone in & reverse shot to get the image

 

[teal'c]

Try a hair dryer and a putty knife, or the screwdriver..
It is possible that if the cap died as a short instead of an open that you could have fried the tweeter.

 

[showett]

The only downside I saw when I considered doing the troels crossover is the cost. It is quite the investment, almost approaching the value of the speakers.

 

[StimpyWan]

well I finally got around to opening mine up...

Well that didn't take long...!

Though, I can't complain. I've been rebuilding on my AR90s for 2 years. And they still have a ways to go.
One day I'll finish them. Following your example, I know I can do it.

As far as the recap, just clip the leads on the old cap, and wire to those. It might not be as pretty, but it works. If you want, you can glue the new cap to the side of the cabinet, to keep it in place.

Good luck.

Oh, which replacement capacitors did you get?

 

[hjames]

Well, the L26 is one of the cheaper JBLs of the era (I think the L19 in that series is under it)
with the L36 and L100 above it. You'll have to decide if its worth putting any money into them -
I doubt you'd recover the costs if you resell them.
(No flames meant - I bought L36s new and kept them for nearly 30 years).
But, they are pretty speakers if they are in immaculate shape.

 

[R Swerdlow]

… the x-over board is stapled & glued onto the front of the inside: nearly impossible to get at!!

lots of glue holding it on, too...had a go with a flathead screwdriver to try & pry it a bit, but no luck

any ideas?

If you're going to replace the caps and the inductors or if you build the Troels Gravesen crossover, you'll find it much easier to leave that old board in place and make a new board.

First, trace those red, green, black (etc.) wires to find where each one is attached, at both ends. Do not rely on memory, write it down. Trust me on that . They connect the crossover board to the main speaker wire terminals on the back of the cabinet and to the woofer and tweeter.

Then cut those wires. Leave enough length, at least 6", attached to the drivers or back-cabinet terminals to work with later when you install the new board. Leave the old board in place. Cap or tape the bare ends of the wires remaining on that old board, and wrap them to stay out of the way.

Cut some thin plywood or Masonite (press board), large enough to hold all the components. Build the new crossover on it. Attach wires that correspond to those you cut. Splice them to the wires on the drivers or terminals. You don't have to match all those colors, just be sure to write down what you do, and better yet label them with tape and a sharpie pen.

If you plan on building the new design by Troels Gravesen you will definitely need a larger board. Gravesen knows what he's doing, and based on his graphs and measurements, I would go ahead and do what he says. You don't have to buy the Jantzen parts, others from Madisound or Parts Express will easily substitute as long as the capacitance or inductance values are the same.

 

[bolero]

great advice!! thanks everyone

yes I hope the tweeter isn't fried.....can I test it by hooking a 9v battery up to it's leads? if it makes noise it's ok?

 

[bolero]

Well that didn't take long...!

Though, I can't complain. I've been rebuilding on my AR90s for 2 years. And they still have a ways to go.
One day I'll finish them. Following your example, I know I can do it.

As far as the recap, just clip the leads on the old cap, and wire to those. It might not be as pretty, but it works. If you want, you can glue the new cap to the side of the cabinet, to keep it in place.

Good luck.

Oh, which replacement capacitors did you get?

hahahaha...!!

well the speakers *were* working, so I was in no rush: other priorities made me forget all about it, until I noticed the one tweeter wasn't working

I just bought some cheap caps at a local electronics place: axial type & the brand appears to be "SC", with a lightning bolt in front of the "S"

 

[R Swerdlow]

yes I hope the tweeter isn't fried.....can I test it by hooking a 9v battery up to it's leads? if it makes noise it's ok?

A 1.5V AA battery has plenty of juice for this. It will make a driver's cone pop forward if the + end of the battery is wired to the + terminal of the driver, while the minus end of the battery is hooked to the driver's minus terminal. If the wiring is reversed, the cone pops backward. It won't make any noise other than that brief pop.

 

[litefootdan]

I wouldn’t go with a 9v. I’ve only ever needed a 1.5v to hear whether a tweeter functions. Also, I can’t speak to Troel’s handling of the L26, I can for the L36. For my money, he took those JBL drivers to another level. As said before, you don’t have to use Jantzen stuff. But I imagine you’ll hear some pretty sweet music.

 

[bolero]

well...unbelievably, the tweeter just started working again

I had some music on while working on a gtr tonight, and thought "wow, is that some high end I hear on the L side...? "

pressed my ear against the grill and sure enough, I could hear cymbals & hihats coming from the recently deceased

bizarre!!

it was 100% not working the other day, even after all my monkeying

only explanation I can think of: it took a day for the contact cleaner I sprayed into the pots ( I have two pots mated together in my tweeter adjust dial, unlike other pics I have seen ) to work it's way into whatever had oxidized etc

 

[R Swerdlow]

well...unbelievably, the tweeter just started working again…

it was 100% not working the other day, even after all my monkeying

only explanation I can think of: it took a day for the contact cleaner I sprayed into the pots ( I have two pots mated together in my tweeter adjust dial, unlike other pics I have seen ) to work it's way into whatever had oxidized etc

The only way to eliminate that problem is to eliminate those variable L pads. Old or new, they all oxidize enough to make the tweeter seem noisy or dead.

You may have noticed that Troel Gravesen's crossover design does away with them, using only fixed resistors. http://www.troelsgravesen.dk/JBL-L26_files/L26_new4th-order_XOv3.gif

 

[Mikerodrig27]

well...unbelievably, the tweeter just started working again

I had some music on while working on a gtr tonight, and thought "wow, is that some high end I hear on the L side...? "

pressed my ear against the grill and sure enough, I could hear cymbals & hihats coming from the recently deceased

bizarre!!

it was 100% not working the other day, even after all my monkeying

only explanation I can think of: it took a day for the contact cleaner I sprayed into the pots ( I have two pots mated together in my tweeter adjust dial, unlike other pics I have seen ) to work it's way into whatever had oxidized etc

Did you use the crossover for the L26 three way in your L36 speakers?