How old are your speakers

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My Infinity IRS Betas are 25 years old. They are excellent speakers, but they are showing their age. I am looking to sell them once I get enough money to put together a speaker system that can duplicate what they can do. I'd keep them if I could find someone to totally go through them and make them new again. Parts are impossible to find for them.
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Montaldo, I would not completely dismiss the importance of materials and technology in building a speaker.
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