nrenter
Active Member
This is an extension of a thread I posting in over on the Pioneer forum. I was suggested I move the content to the Speaker forum, as the content may be more relevant to the speaker-centric crowd.
I scored a beautiful set about a year ago. Both the cabs and all the drivers are in pretty good shape (I used to say "amazing" shape, but since I've been more up-close and personal lately, I've noticed more blemishes - but in their normal position, they do look "amazing"). I got lucky. Very lucky.
I re'cap'ed the crossovers myself, but always felt like these speakers weren't reaching their potential. I contacted Sean @ skiingninja.com about a complete crossover rebuild. After 5 hours of bench time, he diagrammed the schematic (Pioneer doesn't even have a copy of the HPM-200 crossover schematic).
After reviewing the circuit, Sean broke the news to me: He could reproduce the crossover with premium parts and I'd hear a significant improvement. But I'd be better off taking my speakers to Danny Ritchie w/ GR Research to have each of the drivers measured and (most likely) have a new crossover designed. I may be crazy, but I was interested in seeing what these things can do...so I pack them up and make the 2 hour trek to Iowa Park, Texas.
Surprisingly, the HPM-200s are very flat for the vast majority of the audio range (like +- 2dB for most of the audio band) w/ the stock crossover design.
However, there are a few caveats:
The horizontal off-axis response is pretty amazing for the low end (obvious) and the high end (as it should with a cylindrical tweeter / super-tweeter). However, the mids start to suck-out off-axis.
Vertical off-axis kinda sucks...so make sure your ear is about at the bottom of the top panel. Even though they are big speakers, stands (blocks) should be considered to get them to ear-level.
That's not to say the crossover is completely optimal - but it's pretty damn good for a 40 year design. I'll have some of the shortcomings fixed in the rebuild. Let's say that I now have an appreciation for the rollover points for the SX-1250 tone controls.
The impedance plot didn't look too wicked, either.
The waterfall plots of the frequency response shows that the cabinet causes some very interesting artifacts - both for the mid-range drive and the tweeter / super-tweeter. Even a little bit of tweaking using some heavy felt made some easily-measurable differences. The "shelter" that houses the tweeter / super-tweeter and the crossover is not your friend.
Danny and I experimented with some absorption materials to dampen the resonance of the "shelter" and provide a bit of off-axis absorption and not only does that decrease the "ringing" but it smooths the frequency response a bit. Same thing with placing some heavy felt around the mid-dome and the small protrusions on the sides of the cabinet (normally covered by the grille). Even minimal changes were visible on the frequency response and waterfall plots.
I'm going to have Sean get started on the rebuild of the crossovers. I'll post pix and whatnot as I get them. I may see if I can get Danny to re-measure them w/ the new crossovers and some resonance tweaks.
I scored a beautiful set about a year ago. Both the cabs and all the drivers are in pretty good shape (I used to say "amazing" shape, but since I've been more up-close and personal lately, I've noticed more blemishes - but in their normal position, they do look "amazing"). I got lucky. Very lucky.
I re'cap'ed the crossovers myself, but always felt like these speakers weren't reaching their potential. I contacted Sean @ skiingninja.com about a complete crossover rebuild. After 5 hours of bench time, he diagrammed the schematic (Pioneer doesn't even have a copy of the HPM-200 crossover schematic).
After reviewing the circuit, Sean broke the news to me: He could reproduce the crossover with premium parts and I'd hear a significant improvement. But I'd be better off taking my speakers to Danny Ritchie w/ GR Research to have each of the drivers measured and (most likely) have a new crossover designed. I may be crazy, but I was interested in seeing what these things can do...so I pack them up and make the 2 hour trek to Iowa Park, Texas.
Surprisingly, the HPM-200s are very flat for the vast majority of the audio range (like +- 2dB for most of the audio band) w/ the stock crossover design.
However, there are a few caveats:
- The crossover tested had all the stock caps replaced with Dayton caps
- The tone controls on both the tweeter and super-tweeter must be in maximum position.
- The tone control on the mid should be in the center position.
- On-axis listening height is basically the bottom of the top of the cabinet.
- Grilles are off
- And most importantly, the polarity of each of the drivers must be "correct" (the way my drivers were initially connected to the crossover were not "correct"). This took a little playing around to figure out. And...this explains why I thought I wasn't get the most out of the speakers.
The horizontal off-axis response is pretty amazing for the low end (obvious) and the high end (as it should with a cylindrical tweeter / super-tweeter). However, the mids start to suck-out off-axis.
Vertical off-axis kinda sucks...so make sure your ear is about at the bottom of the top panel. Even though they are big speakers, stands (blocks) should be considered to get them to ear-level.
That's not to say the crossover is completely optimal - but it's pretty damn good for a 40 year design. I'll have some of the shortcomings fixed in the rebuild. Let's say that I now have an appreciation for the rollover points for the SX-1250 tone controls.
The impedance plot didn't look too wicked, either.
The waterfall plots of the frequency response shows that the cabinet causes some very interesting artifacts - both for the mid-range drive and the tweeter / super-tweeter. Even a little bit of tweaking using some heavy felt made some easily-measurable differences. The "shelter" that houses the tweeter / super-tweeter and the crossover is not your friend.
Danny and I experimented with some absorption materials to dampen the resonance of the "shelter" and provide a bit of off-axis absorption and not only does that decrease the "ringing" but it smooths the frequency response a bit. Same thing with placing some heavy felt around the mid-dome and the small protrusions on the sides of the cabinet (normally covered by the grille). Even minimal changes were visible on the frequency response and waterfall plots.
I'm going to have Sean get started on the rebuild of the crossovers. I'll post pix and whatnot as I get them. I may see if I can get Danny to re-measure them w/ the new crossovers and some resonance tweaks.