mattsd
Super Member
I think I have finally figured out the sweet spot for modding the crossovers on these things! I had really been wanting to take the harshness out of the HPM's for a long time and a week ago I decided to do something about it. The current crossover points were about 1600Hz, down 6dB at 3200Hz for the woofer and a staggering 5300Hz, down 6dB at 2650Hz for the midrange with the new 4.3uF poly cap I had in there (I had previously recapped them following the HPM-100 recap thread on here).
I started calculating about what the crossover points would need to be and came up with 2400Hz for the midrange and 1200Hz for the woofer, which would put the midrange down 6dB at 1200Hz and the woofer down 6dB at 2400Hz so one would pick up where the other left off. Of course, that is on paper figures and not real world, using paper figures and figuring 7 ohms to be the impedance of the drivers (which it was, I checked) it would ne667-ECW-F2154JAQed a 9.47uF cap for the midrange and a .92mH inductor for the woofer, nether of which is made. So, I went with a 10uF cap, this one here: Dayton DMPC-10 for the midrange, this one can also be used: Dayton PMPC-10 and a .90mH inductor, this one here: Jantzen 0.90mH 18 AWG Air Core Inductor for the woofer.
After waiting in suspense for them to get here, they arrived and I almost instantly got the crossovers out, but only redid one as I wanted to compare the two. Put the redone one in my left speaker and the right stayed original. Hooked them up to my recapped SX-1980 and put on a song that I had always noticed a lot of harshness with. Press play and listened to it through the right speaker, then switched to the left. No way, am I hearing what I think I am?! The harshness is all but gone, listening to the right speaker there is a blare and harshness, the left is sweet and unbelievably clear compared to the right, the treble and midrange in the left sounds tenfold better in clarity and definition compared to the right. The honk and blare of the woofer is all but gone as well. I am in shock, I never expected this much of a improvement. I going to be trying more songs to see how they sound, stay tuned!
Edit 9/25/17: The replacement I used for the .15uF cap come from Mouser, part number is 667-ECW-F2154JAQ.
I started calculating about what the crossover points would need to be and came up with 2400Hz for the midrange and 1200Hz for the woofer, which would put the midrange down 6dB at 1200Hz and the woofer down 6dB at 2400Hz so one would pick up where the other left off. Of course, that is on paper figures and not real world, using paper figures and figuring 7 ohms to be the impedance of the drivers (which it was, I checked) it would ne667-ECW-F2154JAQed a 9.47uF cap for the midrange and a .92mH inductor for the woofer, nether of which is made. So, I went with a 10uF cap, this one here: Dayton DMPC-10 for the midrange, this one can also be used: Dayton PMPC-10 and a .90mH inductor, this one here: Jantzen 0.90mH 18 AWG Air Core Inductor for the woofer.
After waiting in suspense for them to get here, they arrived and I almost instantly got the crossovers out, but only redid one as I wanted to compare the two. Put the redone one in my left speaker and the right stayed original. Hooked them up to my recapped SX-1980 and put on a song that I had always noticed a lot of harshness with. Press play and listened to it through the right speaker, then switched to the left. No way, am I hearing what I think I am?! The harshness is all but gone, listening to the right speaker there is a blare and harshness, the left is sweet and unbelievably clear compared to the right, the treble and midrange in the left sounds tenfold better in clarity and definition compared to the right. The honk and blare of the woofer is all but gone as well. I am in shock, I never expected this much of a improvement. I going to be trying more songs to see how they sound, stay tuned!
Edit 9/25/17: The replacement I used for the .15uF cap come from Mouser, part number is 667-ECW-F2154JAQ.
Last edited: