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Technical documentation for JBL L100 Classic Tweeter (JT025TI1-4)

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Hello everybody!

I'd like to restore a few older JBL Studio Monitors and I'd love to replace the old tweeters with newer ones from JBL, to keep it in the family. Does anyone know, how to get a data sheet for the new JT025TI1-4 tweeter they put in the L100 Classics? The size of the mounting plate would be ideal and I already have a seller for them, but nobody seems to know even the most basic technical specs like efficiency, DC resistance or nominal impedance. JBL/Harman support is giving me the runaround and even their local service partners say, they can't get any data sheets for individual drivers.

Any one here with connections to JBL Synthesis?
 
OP
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Nothing so far... I also have two pairs of 4412a. That 052ti tweeter is hard to replace. I'll order two of those new tweeters and do my own measurements. I have custom crossovers anyways, I'll just fix it in post haha
 

Vinylitic

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I was doing some reading, and if i remember correctly the JT025TI1-4 crosses over at 3khz in the L100 classic and the 052ti crosses over at 3.5Khz in the 4412a.
Therefore it should work without issue, with the stock 4412a crossovers.
Where are you ordering your tweeters from?
 
OP
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In the 4412a it should cross at 4k, but that's generally not that big of a problem for a tweeter in a 3way design. The "big" problem is, that the 052ti is rated at 96dB/1W at 8 Ohms, that is very, very efficient. The level matching will be the problem with the new tweeter. I have some hope, though, since the new L100 Classic are rated at 90dB with the L-Pads at -3dB. That would have to mean that new tweeter also pretty efficient.

I asked a couple of JBL service partners if they would send me a pair of JT025TI1-4s and the german support are so far the only ones who agreed to do it.

Are your 052ti completely gone? They are a truly wonderful tweeter when in spec, but horrendous as soon as the foam plug starts to rot. I changed the foam plugs on mine and then selected the two best tweeters for the main pair, but it was painful. I went through 8 different kinds of foam and a week of complete insanity. They sound great now :cool:
 
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I don't mind at all! I settled on a pretty stiff, closed cell damping foam from a camera case. I cut it so it protrudes 8mm from gap behind the dome and gets compressed when you reassemble it. It's pretty easy to do, since JBL prided themselves on their "field serviceable tweeters" in their pro equipment. The voice coil is basically self-centering and you only need a screwdriver and a steady hand. I was really impressed by how such an old, fairly primitive metal dome tweeter can sound. The 4412a are, to my ears, easily the best of all the classic JBL 3-way designs.
 
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Vinylitic

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I’ve been wondering how much of an improvement, if any, there would be to the 4012a using the L100 classic tweeter.. only because of the built in “wave-guide” to disperse the upper ranges better..?
 
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I’ve been wondering how much of an improvement, if any, there would be to the 4012a using the L100 classic tweeter.. only because of the built in “wave-guide” to disperse the upper ranges better..?
It's also a much more modern tweeter, with soft surround and a much stiffer titanium dome and a ferrofluid cooled voice coil. 30 years of engineering and material science between them. But I'm also very curious how much better it can be.
 

Vinylitic

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Curious to know how much the tweeters you are sourcing are out of Germany..?
 

Vinylitic

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Please post your thoughts on your mods, I am more than curious to know the outcome… Are you planning on using the original Xovers..? Or something different?
 
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Update: The JT025TI1-4 tweeters have arrived and I measured and installed them. They are indeed a drop-in replacement for the old 052ti. They measure 96dB SPL/1W and around 4 Ohms DC resistance, like the 052ti. Luckily, they also fit the 4412a cabinet without modifications (apart from new screw holes). The terminals are also the same size, but it's of little use, since the polarity is flipped. You will have to account for that when installing.

I haven't listened yet, but I assume it's fine. In the process I have also confirmed that a properly working 052ti is a damn fine tweeter :)
 

Vinylitic

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Wow..! All good to know..
Interested what your thoughts are after listening.. If there is any improvement in overall speaker performance/sound quality
 

Vinylitic

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Wondering if you have had the opportunity to do some listening listening to your 4412a’s with new tweeters..? And what your thoughts are..?
 
OP
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Sounds fantastic! A lot more detail above 10khz and dispersion is so much better. I can recommend this upgrade 100%. The faceplate is 2mm thicker than the old one, but a 125mm rotary sander fits the cabinet hole perfectly and it took me about 20 minutes to flush mount them. I reinforced the inner edge of the baffle hole with a metal band for extra stability (the screws just barely hit the wood) but that might not be necessary. If you're not someone who takes their speakers apart all the time, you can of course get a lot more creative when mounting them (blue tack works a treat).
 
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