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Mirror Image a Pioneer HPM-100

A

acdc7369

Active Member
Thinking about cutting out the baffle board, flipping it around, refinishing it, then putting it back in the cabinet and resealing it. Obviously I want to do this to improve the imaging of my system.

Has anybody done this before? Any tips you'd like to give me? Is there any reason this wouldn't work?
 
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I find myself wondering what you hope to gain by doing that - and why the factory decided not to do it to begin with.

To me - the HPM-series is such a treat exactly the way they are. I wouldn't attempt it.
 
When I listen to the speakers with a mono source, it's the most noticeable. The mono image does not sound entirely focused straight down the center as it should...it sounds like its moving around a bit. I believe that mirror imaging the right speaker very well may correct it.

I think the factory decided to not go with it because it costs more money to mirror image speakers (because now you're technically selling two different products instead of just one), and also to keep track of selling them in pairs.

And yes, I was going to experiment, by purchasing a single beat up HPM-100 cabinet and trying it out. No way would I start blindly hacking up my speakers.
 
Does that drifting image only occur with those speakers? I ask because that would generally be attributed to the source material or the amplifier/pre-amp/receiver.
 
acdc7369 said:
When I listen to the speakers with a mono source, it's the most noticeable. The mono image does not sound entirely focused straight down the center as it should...it sounds like its moving around a bit. I believe that mirror imaging the right speaker very well may correct it.

I think the factory decided to not go with it because it costs more money to mirror image speakers (because now you're technically selling two different products instead of just one), and also to keep track of selling them in pairs.

And yes, I was going to experiment, by purchasing a single beat up HPM-100 cabinet and trying it out. No way would I start blindly hacking up my speakers.
Click to expand...

That is a safe way to do it. Let us know if you give it a try.
 
I highly modded my 100 crossovers very much to my liking. What weakness was then left was a "skewed" stereo image. My listening distance was about 12 feet.
This offset image bothered me to which I sold them. Otherwise I got to like the sound more than my NS1000s. So yes, I say your idea would be worth the effort.

Stan
 
Why the Fuchs not. I think it would be an interesting experiment. Only if you If if you have good woodworking skills and. And can make them look nice.
 
Interesting project. Thinking through it, I am wondering how you reattach the baffle once it is "cut out" and flipped. If you add some sort of strip internally to have a nail/screw surface, you have changed the cavity size. Granted this change may be minor but I think so will be the effects of flipping the baffle too.

Other than doing it "just for the hell of it", I would be surprised if the results are measurable. Stranger things have happened however!

I admire your willingness to push the envelope though. Please let us know if you find the outcome worth the effort. :thmbsp:
 
It will be an improvement...no question about it.Mirror imaging is always worth it.
I am going to do it to some Pioneer S 910s.
Since the baffle also has 90 degree corners,i am going to just add a new rounded corner baffle to both speakers.

Now the baffle will be twice as thick,mirror imaged and smooth edged.(that will improve edge diffraction)
All of these changes are proven,measurable improvements.

Adding a baffle to the existing front is in my opinion,easier than your current plan.
Plus,you could use some really nice wood if you like. :)
 
I.R.Brainiac said:
It will be an improvement...no question about it.Mirror imaging is always worth it.
I am going to do it to some Pioneer S 910s.
Since the baffle also has 90 degree corners,i am going to just add a new rounded corner baffle to both speakers.

Now the baffle will be twice as thick,mirror imaged and smooth edged.(that will improve edge diffraction)
All of these changes are proven,measurable improvements.

Adding a baffle to the existing front is in my opinion,easier than your current plan.
Plus,you could use some really nice wood if you like. :)
Click to expand...

Hmm... My S910's are already mirrored...
 
Imaging can be checked with a null test.

Basically just getting a microphone exactly centered in the sweet spot and measuring some pink noise at a reference level.

Then reverse the wires on one speaker and test again.
The cancellation will drop the dB measured...the more cancellation,the better the imaging.

If you do a sweep instead of pink noise you can even see which frequencies are canceling best.

Full cancellation is impossible at higher wavelengths for a number of reasons...mostly room acoustics but it is plain to see that mirror imaging makes a difference.

A null test is also a good way to see if you have optimally placed your speakers. :)
 
I just aquired my HPM-100's last week, but even prior to that I couldn't understand Pioneer's logic (or lack of) in non-mirrored pairs. Perhaps in this case cost cutting or even a certain laziness overuled. Or did they provide their reason behind this when these speakers were promoted and first released?

I listen to mine at close range but don't want to become overly aware of the possible imaging imbalence lest it become a main area of focus if not disdain. But for those with the patience and skilled hands and discriminating ears it may well provide rewarding results.
 
I could be wrong, but with the onslaught of kabuki speakers in the mid 1970s, I don't think anyone thought about mirror imaging back then...

Want even more bang for your buck? Since you'd be modifying the front baffle anyway, try replacing all the HPM-100 drivers with HPM-900 driver including the HPM-900 crossover. :thmbsp:
 
-reverb- said:
Interesting project. Thinking through it, I am wondering how you reattach the baffle once it is "cut out" and flipped.
Click to expand...

I was actually hoping somebody could clue me in as to how the baffle is attached and sealed to the cabinet in the first place.
 
pognoot said:
I could be wrong, but with the onslaught of kabuki speakers in the mid 1970s, I don't think anyone thought about mirror imaging back then...

Want even more bang for your buck? Since you'd be modifying the front baffle anyway, try replacing all the HPM-100 drivers with HPM-900 driver including the HPM-900 crossover. :thmbsp:
Click to expand...
Getting really close to doing just that. Read a lot of positive comments about the 900. I have the S.T. already. Wish I had someone nearby that I could run all the drivers through DATS and get some solid T/S specs to compare by. That would likely eliminate a lot of speculation. Also, based on posts, I'm thinking the heavier construction of the 100 cabinets may help things further.

Thought about mirror image. Planning on doing that with my AR3a speakers THOUGH I plan to build new boxes rather than mod the originals. Can't bring myself to destroying a classic.
 
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