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Refurb and Revamp of Klipsch KP-301


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I've finally reassembled a pair of Klipsch KP-301s I've had in disassembled form for too long. I bought them three years ago from a musician who had used them in his travelling rock band for years. When I got them, they were beat up on the outside, grilles frayed, but whole. Upon more detailed examination, I found neither tweeter worked and one of the woofers had been replaced by an 8-ohm JBL 2226H. 


I pulled them apart, sanded all of the crackle finish off of the cabinets, repaired all dings and scars, primed, and repainted with semi-gloss black. It came out pretty well, but these will never be anywhere near mirror-finish. But now they're quite presentable.


Internally I used a good deal of 1" square wood molding to brace the cabinets, both along the length of all panels and braced across panels to eliminate resonance.  As an experiment and practice on how to brace cabinets this was a great exercise. Given how thick these cabinet walls are from the factory I'm sure the bracing will result in a rock solid box. 


Dead tweeters got new Crites Titanium tweeter diaphragms, and the crossover got Dayton 1% caps for mid and tweeter, new electrolytics for the woofer, and Mills resistors. The rest was kept stock. 


I filled the stock port holes with 6" tubes from Parts-Express. Using an online tube and frequency calculator I found this would lower the resonant frequency of the cabinet and add more oomph below 50 Hz. 


I just put these back together yesterday and ran a short demo on my restored Fisher 500C. My first impression was extremely positive. These are very lively and dynamic, which is no surprise. The Fisher is an ideal pairing and the efficient KPs really let it shine. The bass is accurate, full, and can extend low. I was expecting more with the port tubes but these do not bellow out of the box like me Series 1 CF-4s. I used the tone controls on the Fisher to lower the treble to 11 O'clock (leaving bass where it is) and this helped. With the right song (I tried Muse Madness) these are lower and hit hard. 


What really surprised me was how well these image - I had the speakers 1' off the wall, slightly toed in, about 10' from one another and 7' from me. These worked like monitors!


Overall I am very satisfied. And while I planned to re-cover the grilles with new cloth, my wife told me she likes the industrial look. So maybe they'll stay open. 


I also planned on playing with these for a while before selling/trading them on but now that I've heard them that may be difficult. At the least, they will go into my main system while I do a careful restoration of my Klipsch CF-4s.


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These look great! I like the industrial look as well. I have a pair I am planning to build. Do you recommend Crites titanium tweeters? Also did you keep the JBL woofer and if so did you notice a difference from left to right? One of my woofers is bad and I am trying to decide if I need to replace both of them or only one. Thanks! 

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I really like the Crites tweeters - to my ear they sound very smooth. When I tested them after installation of the diaphragms and before putting them in the speaker, 'smooth' was actually the first word that came to my mind when I heard them. That said, the speaker still tends to be extremely lively and has the Klipsch sizzle that I know from other Heritage models. If you have the money or need to replace defective diaphragms, I would recommend spending the additional money (about $30 over phenolic diaphragm replacements) for the titanium. I think that midrange diaphragms would provide even more of an improvement but I didn't budget for them, and really I like how the midranges sound now. 


I bought a replacement K-48 woofer on eBay to have two matching woofers in the speakers. I then sold on the JBL woofer to someone locally who was looking for one. Cost-wise it turned out to be a wash, which was great. Interestingly, the woofers while measuring the same are slightly different in frame construction (guessing different subcontractors) - the new woofer is a little bulkier. But the cones, surrounds, and magnets are identical. 


If you have one bad woofer and the other one tests OK, I would recommend trying to find another K-48 like I did, or replacing both at the same time. Klipsch may have replacements in stock (I did not check). Other places on this forum folks have recommended the Eminence Kappa Pro 15LFC as the closest drop-in replacement. If you go that route I recommend buying two new woofers and then selling on your remaining original woofer. If you are going to use yours as home speakers like I am, you can also consider going with a different 15" woofer with different frequency response or sensitivity to bring out more low-range if you like - the KP-301s did not reach super low but were able to take massive power, which would not be a requirement in near-field listening. If you do that then there are mods you should do to the crossover and perhaps box tuning that are beyond my capabilities. And after my restoration I'm fine with the low frequency response of these speakers as-is - I think with the right placement and amplification they will sound excellent. Interestingly enough I'm still playing with them and the port tubes to determine what difference the tubes are really bringing to the bass performance - this may take more A/B for me, and perhaps playing with room placement to isolate speaker performance from room performance. 




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