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Thread: 250ti Top End

  1. #1
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    250ti Top End

    Hi Everyone.

    I have a pair of 250ti's - the later gloss black early 90's versions.

    They sound great except for the top end. The best way to describe it is shreaky/steely - particularly on vocals.

    What can I do? Perhaps new caps may help or what about charge coupling the xovers?

    What do the experts here suggest?

    Thanks in advance.

  2. #2
    Senior Member rdgrimes's Avatar
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    The foam damper pads in the 044ti are known to degrade and fall apart. Replacing them requires taking the driver apart. There are a few threads around here about the process if you search.

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    Quote Originally Posted by rdgrimes View Post
    The foam damper pads in the 044ti are known to degrade and fall apart. Replacing them requires taking the driver apart. There are a few threads around here about the process if you search.
    Thanks for your reply. I will take your advice.

    I think these have the 035ti tweeters - could be wrong. Many years ago the Stereo Review article regarding the 250ti's raved about how sweet the top end was. I expected better.

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    Administrator Mr. Widget's Avatar
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    Quote Originally Posted by sweet212 View Post
    Many years ago the Stereo Review article regarding the 250ti's raved about how sweet the top end was. I expected better.
    Many years ago they probably did. Speakers do age. Yours may need servicing.


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    Senior Member rdgrimes's Avatar
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    Quote Originally Posted by sweet212 View Post
    Thanks for your reply. I will take your advice.

    I think these have the 035ti tweeters - could be wrong. Many years ago the Stereo Review article regarding the 250ti's raved about how sweet the top end was. I expected better.
    Ah yes, you have the Special Edition models. Those originally came with the 035ti and I think they even came later with something like a 052ti, but I could be wrong about the later. The same holds true in either case, they age. Although the 035ti is much easier to find to buy used than the 044ti. I'm pretty sure there are still some new reproductions of the 035ti being sold.

    Look at your crossover boards for any obvious signs of age like bulging caps. If you want to rebuild the tweets, I'd first find a used pair to buy and experiment on. The good news is that the 035ti is 10 times easier to remove than the 044ti models are.

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    Quote Originally Posted by rdgrimes View Post
    Ah yes, you have the Special Edition models. Those originally came with the 035ti and I think they even came later with something like a 052ti, but I could be wrong about the later. The same holds true in either case, they age. Although the 035ti is much easier to find to buy used than the 044ti. I'm pretty sure there are still some new reproductions of the 035ti being sold.

    Look at your crossover boards for any obvious signs of age like bulging caps. If you want to rebuild the tweets, I'd first find a used pair to buy and experiment on. The good news is that the 035ti is 10 times easier to remove than the 044ti models are.
    Thank you RD. When you say reproductions - you mean copies of the tweeter by 3rd parties? I had a look at the boxes - they are "Classics" and also marked BQRC or BGRC - hard to read.

    Would replacing the caps be an improvement? Made a definite improvement with my old 212's.

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    Quote Originally Posted by sweet212 View Post
    Thank you RD. When you say reproductions - you mean copies of the tweeter by 3rd parties? I had a look at the boxes - they are "Classics" and also marked BQRC or BGRC - hard to read.

    Would replacing the caps be an improvement? Made a definite improvement with my old 212's.
    Unscrewed the tweeters - they are 035tia's. For some unknown reason the authorized JBL service center will not recondition these speakers - 035ti's yes but not the 035tia's. What can the difference be, apart from contact placement?

    I have 2 options. Buy a Chinese drop in clone or repair the old tweeters. I prefer to keep the original components. Especially as their DC resistance checks out at 3.8 ohms, which I assume is OK.

    So how hard can it be for a novice like me to replace the foam?

    Who here has re foamed a 035tia tweeter?

    Please let me know.

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    Senior Member SEAWOLF97's Avatar
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    Quote Originally Posted by sweet212 View Post
    Unscrewed the tweeters - they are 035tia's. For some unknown reason the authorized JBL service center will not recondition these speakers - 035ti's yes but not the 035tia's. What can the difference be, apart from contact placement?

    I have 2 options. Buy a Chinese drop in clone or repair the old tweeters. I prefer to keep the original components. Especially as their DC resistance checks out at 3.8 ohms, which I assume is OK.

    So how hard can it be for a novice like me to replace the foam?

    Who here has re foamed a 035tia tweeter?

    Please let me know.
    this thread ==>>

    http://www.audioheritage.org/vbullet...ght=044ti+help

    is about replacing the foam in 044's, but same procedures for 035 (I think)
    “If you think that’s the dumbest thing you’ve ever heard,
    just wait a couple minutes!”

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    Senior Member BMWCCA's Avatar
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    Be very careful when removing the 035ti from your 250ti's not to bend the terminals as you pull off the Faston connectors. The very fragile diaphragm wires inside can be broken if the terminal tabs are disturbed by wiggling the wire connectors. Hold the terminal in place gently with small pliers as you remove the connectors. Don't be tempted to straighten "crooked" terminals! You'll see what I mean after you get them apart. Just be careful and the job should not be that difficult.
    ". . . as you have no doubt noticed, no one told the 4345 that it can't work correctly so it does anyway."—Greg Timbers

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    Quote Originally Posted by BMWCCA View Post
    Be very careful when removing the 035ti from your 250ti's not to bend the terminals as you pull off the Faston connectors. The very fragile diaphragm wires inside can be broken if the terminal tabs are disturbed by wiggling the wire connectors. Hold the terminal in place gently with small pliers as you remove the connectors. Don't be tempted to straighten "crooked" terminals! You'll see what I mean after you get them apart. Just be careful and the job should not be that difficult.
    Thank you both. This is not an easy job especially for a ham fisted and impatient one as myself.

    The best course is perhaps to buy some renovated 035ti's. The terminals are in a different position being 180 degrees apart. So the top of the cabinets will have to be cut out to accommodate the terminal.

    BTW: There is a fluid called ferrofluid - supposed to smooth out the sound of tweeters. Will this work on a 035ti?

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    Well these 035TIA's came apart very easily. The grilles prized off with a ball point pen and the 4 screws were a snack.

    They look to my untrained eyes to be in great condition. The foam is 22 x only 3 mm thick, I believe they should just touch the titanium dome. Can that be right? Wouldn't touching the dome mute the sound?

    The replacement foam pieces should arrive tomorrow.

    Thanking you in advance for any advice.



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    Yes, the function of the foam is ( by lightly touching the inside of the dome ) to mute spurious resonances made by the titanium dome .


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    Senior Member SEAWOLF97's Avatar
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    Quote Originally Posted by sweet212 View Post
    Well these 035TIA's came apart very easily. The grilles prized off with a ball point pen and the 4 screws were a snack.

    They look to my untrained eyes to be in great condition. The foam is 22 x only 3 mm thick, I believe they should just touch the titanium dome. Can that be right? Wouldn't touching the dome mute the sound?

    The replacement foam pieces should arrive tomorrow.

    Thanking you in advance for any advice.
    be best to take compressed air and blow anything out of the mag gap as long as it's opened.
    “If you think that’s the dumbest thing you’ve ever heard,
    just wait a couple minutes!”

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    Senior Member Don C's Avatar
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    I think that your foam is much thinner than it was when new. It's supposed to press up against the back of the dome and conform to it's shape. it should feel springy, not gooey.

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    Quote Originally Posted by Don C View Post
    I think that your foam is much thinner than it was when new. It's supposed to press up against the back of the dome and conform to it's shape. it should feel springy, not gooey.
    Thanks for your replies. The maker of the replacement foam says the foam should made hemispherical to match the shape of the dome and about 10mm thick. OK that will definitely touch. Too much contact and too hard will just about cancel all sound and too little will have no damping effect on resonances - a bit arbitrary. The trick is to get light contact - I assume.

    However I will try and let you know. I have to solder on new leads as the original leads are too short and just reach the tweeter and make it very hard to install.

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