Pioneer HPM-200 Speakers

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.

Pioneer  HPM 200.jpg

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.

Pioneer  HPM 200 horizontal.jpg

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.

Pioneer  HPM 200 vertical.jpg

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.

Pioneer  HPM 200 impedance.jpg

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.

Pioneer  HPM 200 csd.jpg

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.
 
Thanks for the thread, nrent.
I'm an avid fan of the HPM-200 and rank them up there and above most of the vintage speaker systems I've have and heard.
I must agree that the cabinet gets in the way and I've found they sound best raised enough to become ear level with the tweeters, though I'd prefer to have the cabinets on the floor for the sake of a bit better bass reinforcement.
My room is a bit bright and without treatments,so far, so I'll try damping the baffle and cabinet housing.
I wish I could interpret graphs:)
 
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 think this is the image that tells the most interesting story. A waterfall plot basically takes your typical frequency response graph, and makes it 3D - it shows how long each of the frequencies "play on". Sometimes the "ringing" is caused by the design of the drivers. Sometimes it's because of the resonance of the cabinet.

For the HPM-200, the most egregious culprit is the "shelter" that houses the tweeter / super-tweeter and the crossover. Not only do the individual frequencies bounce around and "echo", but the overlap of those bouncing frequencies from the tweeter and the super-tweeter reinforce (or cancel) certain frequencies (that's why you see so many ripples above 3-ish KHz, and some frequencies ring on for almost 4 ms).

With a small bit of damping material placed in the "shelter", you can see a significant decrease in ringing. Although it's not readily apparent, the overall frequency response smoothed a bit, too.

Pioneer  HPM 200 csd 2.jpg

I'm going to line both the top and the bottom of the "shelter" with no-res (or heavy felt) to address these issues.
 
^^^^^^
I just perused the GR Research website and it seems you are in good hands in their "blue room"
I don't know why I haven't done it before but this thread spurred me to treating the baffle around the midrange and see if I can hear any improvement.
I'd definitely like to see pics of the cabinet damping.
 
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The wood-veneered side panel that protrudes from the front baffle about 1"...there's a significant amount of reflection at that point that smears the mid-range. If you make the felt semi-permanent, make sure you take it all the way to the edge of the baffle and up that 1" veneered side.

Here's what Sean is going to use for the rebuild...

  • Custom substrates (satin black)
  • All new wiring (outside the cabinet) and label wire as previous colors
  • Sonicap capacitors
  • Mills resistors
  • Foil and Super Q inductors
  • Cardas quad eutectic solder
  • Custom board stand-offs
  • NoRez sheet x 2 (for cabinet tweak)
  • Electra Tube Connector set

Based on Danny's measurements, I'm going to take the tone control switches out of the circuit (but leave the panel for aesthetic reasons).
 
Tubes,

Here are how my drivers (should be / will be) wired (I'm trying to articulate the color of the wires to the position on the terminals that protrude from the cabinet):

----------------------
|..................RW|
|B..................B|
|W..................B|
|...................Y|
|....Y.W......R.W....|
----------------------

.......(Front)........

The tweeter and super-tweeter are optimally wired counter-intuitively. If you look closely at the wires that attach the tweeter and super-tweeter transformers to the quick-release posts that attach to the leads connected to the tweeter and super-tweeter, you'd instinctively would think the color of the leads would match-up with the leads coming from the tweeter and super-tweeter respectively. According to the measurements, you'd be wrong. The leads should be mis-matched. I hope that makes sense.
 
^^^^^^^
Rather disconcerting but perhaps an indication that tweeters are wired out of phase.
My friend who bequeathed the 200s to me managed to have things miswired:)
I wired all the woofers and mids back in phase and never knew whether or not the tweeters were wired correctly, which I believe to be out of phase by design.

I've read an improperly wired tweeter(in relation to its mid) will measure a dip at the crossover level.
So I assume the HPM-200 tweeter wired any differently would show a dip.
 
I've read an improperly wired tweeter (in relation to its mid) will measure a dip at the crossover level.

As stated, this is correct...and this is how we discovered the issue. The first measurement that Danny performed was a "step response" - this can be thought of as just a pulse of sound that only contains the first (positive) half of a sine wave. The output of a perfectly time-and-phase aligned speaker will look like a right triangle that points up (only a handful of speakers are truly time-and-phase aligned). The Pioneer HPM-200 is by no means time-and-phase aligned (it can be debated if this matters or not), but it does help us establish the absolute phase of the speaker.

The most significant components of the step response comes from the low(er) frequencies. Since the pulse is only "positive" in nature, the output from the speaker should be primarily "positive" in nature. And, again, since the woofers contribute most significantly to the output of the impulse response, you can tell if the woofers are in absolute phase (or, "wired correctly") if the output of the impulse response is primarily positive in nature.

Now you can start to look for irregularities or "suck-outs" in the mid or upper-frequencies. Sometimes those issues can be addressed by reversing polarity of the mids and / or tweeters. That's exactly what we did...and that gave us a very impressive frequency response for a 40 year old speaker.
 
Tubes,

Here are how my drivers (should be / will be) wired (I'm trying to articulate the color of the wires to the position on the terminals that protrude from the cabinet):

----------------------
|..................RW|
|B..................B|
|W..................B|
|...................Y|
|....Y.W......R.W....|
----------------------

.......(Front)........

The tweeter and super-tweeter are optimally wired counter-intuitively. If you look closely at the wires that attach the tweeter and super-tweeter transformers to the quick-release posts that attach to the leads connected to the tweeter and super-tweeter, you'd instinctively would think the color of the leads would match-up with the leads coming from the tweeter and super-tweeter respectively. According to the measurements, you'd be wrong. The leads should be mis-matched. I hope that makes sense.

I must say when I saw your diagram I was a bit confused as the tweeters on my 200s are reversed compared to yours. Also all the pictures I've seen show the red and yellow wires "on the right".:scratch2:

The color coded leads coming out of the transformers correspond inversely with the positive/negative leads going into the transformer and thusly match the tweeter wire color, or so it seems to me.
 
So...it's taken a bit longer than I expected to have my crossovers rebuilt. However, I should have them back any day now (with a few additional tweaks to improve performance).

In the meantime, I gave all the woodwork a good once-over with Howard's Restor-a-finish, Howard's Feed-n-Wax, and a buffer. Plus, I ordered some 1/4 wool felt to cover the face (and some addition points of reflection).

Front.jpg

I'm going to use a light 3M spray adhesive to attach to the front baffle (spray the felt, wait until it's basically set yet still slightly tacky, and press into place). This way, it's still easy to remove should I need / want to.
 
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nrenter, I saw this thread linked from the previous one in the Pioneer sub-section.

Very interesting information here and it's great that you "defining" and then "supercharging" the 200s. Your analysis makes me wonder what an ideal 200 would look like - no top "shelter", crossover mounted somewhere so it doesn't affect the tweeter/supertweeter's 360 degree emittance?

It also makes me wonder why the 200's superior design/performance hasn't been replicated by modern makers - perhaps because the specs were never fully defined? Maybe your research will make it easier to do so!
 
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At a minimum, the speakers should be mirrored pairs.

If you kept the same parts and (most likely) crossover design, it would be a stacked tower of drivers with the tweeter / super tweeter on top. However, once you start changing things, everything changes (how's that for analysis). :)

I'm removing the tone controls from the crossovers (simply tweaking the response for optimally-flat response), and the drivers leads will extend from the crossover directly to the drivers (bypassing the quick-connect tabs in the "shelter"). Pictures coming soon...
 
^^^^^^^
Quality stuff and clean point to point work.
With the tone controls removed I wonder which value resistor(s) were kept in the design that sounded best?
I really believe the tweeters are meant to be wired color coded to the transformers, out of phase.
The HPM 150 diagram shows how its top mounted super tweeter is wired.
Have fun finishing up!
 

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Just got a note that my crossovers are complete!

pioneer_hpm-200_1x1024.jpg

pioneer_hpm-200_2x1024.jpg

pioneer_hpm-200_3x1024.jpg

pioneer_hpm-200_4x1024.jpg

pioneer_hpm-200_5x1024.jpg

Once I receive them, I'll schedule some time with Danny to measure / tweak the results, and check the effect of the heavy felt. More to come!
 
Quite a dramatic difference when comparing the look the old XO to the new one, nice attention to detail on the covered/shrinkwrapped wire.
 
:lurk:

Great thread and looking forward to your impressions. I just picked up a pair of 200s yesterday to go with my 100s and 1500s.

Ordered new foams today and was looking for info on the xos
 
Just received my crossovers today, and I'm trying to schedule time w/ Danny to install / fine tune the response. I'm very pleased with Sean's work.
 
On the home stretch...Crossovers are installed, crossovers direct-connected to drivers, felt absorption material installed, polarity of all drivers verified, frequency response checked...

Only to find out I have a bad supertweeter in one of the speakers. I knew one speaker sounded different when I first tried to recap the crossovers myself, but I figured I botched a circuit.

I took the supertweeter apart, polished the contacts, and even tried to patch (what I thought were) bad connection points to the mylar w/ copper foil...but to no avail.

So...If anyone knows of a spare supertweeter for an HPM-200, let me know (I've posted a WTB to barter town).

Once I get some hours through the crossovers, I'll post impressions.
 
That might be a hard find . What frequencys does the super tweeter handle ? I guess my point is , will any other tweeter do for the short term ?
 
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