Modding old PA speakers. Fender 115XP…replace dual piezo with Fostex horn tweeter?

I found a pair of Fender 115XP speakers, w/ 15” Eminence woofers and a Motolora dual piezo horn, for almost nothing. Used them for an outdoor party with no problems.
However, to me the highs are grating and aggressive, even out on the dance floor, and eq just dulled them. I can make crossovers, so I’m tinkering with a filter, but these are not the supposedly higher quality Powerline models.
I also have a pair of old Fostex horns I could swap in, with a filter @2kHz. Would those be a better alternative? What‘s the CW on piezos vs. conventional dynamic horns for loudness plus sound quality.
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Your project is feasible, but to protect dynamic drivers:

1) use/confirm crossover meets Factory recommened specs and is 12 or 18dB/octave; plain simple capacitors are not usable here.

2) add a 12V 12/15W car lightbulb in series with horn driver, to protect from accidents such as unexpected feedback queals, microphones dropping on the floor, or dangerous program content such as synthesizers, over equalized Music, etc.
 
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A 2 kHz filter on those horns might still sound grating and aggressive. They look like 1” coil drivers, which can’t handle a spectacular amount of power and don’t like be crossed low. You can get a 1” exit driver to sound ”ok” with a 15 if you’re willing to sacrifice some off-axis response, but it takes a 2” coil driver to do it. 3kHz would work nicely with that type of tweeter, but the 15 would struggle. You could try it and see if you can live with the result.

The “proper” way to do it is with a 1.4” or 2” exit driver with a 3” coil, crossed over at 1200 or lower. But then you’re talking Real Money, and Real Work to make a proper crossover. To do it on the cheap I would consider a 6” closed back midrange, and the tweeters you have - then put effort into the crossover.
 
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Thank you both. The Fostex are 1” phenolic domes. They used to be paired with 12” woofers, and I remember the treble sounding better than the piezos. Maybe a 2nd order L-R at 2.5 to 3kHz and a protector of some kind.
The 2” horn drivers I see with enough HF extension and power handling are too pricey.
 
Just about any dynamic compression driver is better than a piezo, I say just about any because I have actually seen and heard a CD that didn't... no surprise that they came out of a set of white van speakers. Those piezos would sound acceptable at low to medium volumes if there were crossed at 5kz or above but that just trades one problem for another, so I suspect that if you follow the advice already mentioned and use a proper crossover on the Fostex drivers they will be an upgrade.
 
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