[Philimon]

Wait, what? Mini HP-1? Or is it a xl HP-1?

 

[Philimon]

Instead of felt on back of driver as air damping, I tried sealing vents. Used butyl because easy to mold, noise isolation, and mass for maybe enclosure resonance control. The cup still has a leak at the pivot joint where it attaches to headband. I left this open purposely for venting. I couldnt leave bare so added a foam disc for some absorption. This setup had the goal of more backwave dispersion vs direct coupling with felt behind driver. Ive not tried yet, but measurements are interesting.

 

[Philimon]

Probably too much damping. I removed foam. Replaced with wall lining felt.

 

[Philimon]

After removing foam I now disagree on the too much damping comment. Going to add more.

 

[JadeEast]

Great to see measurements with some of these older models and tuning efforts. Kind of amazing efforts at the time I think with the Yammy pieces... Italian design Japanese innovation and manufacturing. 30-40 years old and still having validity.

To deal with aging pads and to mess around, I've loosely stuffed some loose weave fabric (Polartec Alpha... a very loose synthetic knit insulation) under the pads of my HP1A around the interior covering a number of the outer holes of the driver. I don't have a measurement rig but it's improved the comfort and seal, if not overall sound to my ears. Reduced the volume somewhat in the cavity and should reduce a bit of the reflections inside the ear/cup. And subjectively I think it's helped tilt things down and smoothed HF. I'm sure there's a trade off with some of the tippy top end. But I'm pretty satisfied right now. But I think I'm just a sucker for this pair of headphones overall.

If you're messing with the back wave no reason not to play with the front as well.

 

[nick n]

For the Final Audio ortho, it does look interesting. Not in my price range and I've got a cache of vintage odd balls that I quite like, but I've been waiting and hoping for a "VolksOrtho" to emerge since the start of this thread. Was the old radio shack Pro-30 the cheapest one made? Who's the budget champ of all time?

Yeah the good old "Volks Ortho".
I used to think Philips would have jumped in on that but they are/were a little too corporate if that word fits.
Hard to say what the budget champ was, aside from Pro-30 you mentioned plus all the wierd and not too common SFI stuff.
Oppo tanked out I wanted an on-ears personally. Nobody wants to make one. I mean good one.
Yeah I know the on ears from overseas ...

don't talk to me or my son ever again

^ Oh that's a nice colour there Takato. Kalbee had a green one if I recall correctly. Hard to find those variants. ( if it is what i think it is = the HP-4 ).

 

[takato14]

Wait, what? Mini HP-1? Or is it a xl HP-1?

It's a rare alternate-color variant of the HP-2. I'm not sure of the story behind these commercially (how they were sold and such), but this unit is a rather high serial number and is in nearly perfect condition. It almost appears to have never been used.

Anyone know something I don't?

 

[nick n]

Other than those old brochures I don't know much.
There must be something early on in here about it.
Pretty sure the green one was sourced out of Japan.

The brochure does use Japanese writing.

https://www.head-fi.org/threads/orthodynamic-roundup.111193/post-5535931

 

[Philimon]

Great to see measurements with some of these older models and tuning efforts. Kind of amazing efforts at the time I think with the Yammy pieces... Italian design Japanese innovation and manufacturing. 30-40 years old and still having validity.

To deal with aging pads and to mess around, I've loosely stuffed some loose weave fabric (Polartec Alpha... a very loose synthetic knit insulation) under the pads of my HP1A around the interior covering a number of the outer holes of the driver. I don't have a measurement rig but it's improved the comfort and seal, if not overall sound to my ears. Reduced the volume somewhat in the cavity and should reduce a bit of the reflections inside the ear/cup. And subjectively I think it's helped tilt things down and smoothed HF. I'm sure there's a trade off with some of the tippy top end. But I'm pretty satisfied right now. But I think I'm just a sucker for this pair of headphones overall.

If you're messing with the back wave no reason not to play with the front as well.

Thats why hybrid pads are common these days. Just need to find some in decent size or order customs for $&$ or diy as youve effectively done @JadeEast . Another orthohead @stratocaster (unsure of his headfi handle) used felt underneath the pads. I tried this trick with Fostex T10 because the T10’s stock pads cover some of the driver side ear holes. I hoped the felt lining would allow more airflow for improved sound, but I did a poor job and seal was lost at pad edges so I lost bass. Ill try a hybrid something with YH-2.

@dBel84 mentioned to me that HP/YH-2 had a few known magnet variants. Most common is rough edged, then rarer is smooth with chamfered holes, then rarer still is square-holes. The one Im playing with now is smooth + chamfered. I tried searching this thread, anyone know more?

@takato14 Black does look much less dated. I sent the Pioneer SE-500 to @dBel84 . He tried them and maybe he’ll post impressions. I dont know if he used an amp up to @wualta spec but dbel is an experienced diy amp builder so he could tell us.

The orthos I lost interest in I passed to ortho virgins to spark more interest at other website. Sorry about your wallets but Im sure you guys have a nice collection already.

I mostly want a HP-1a and a functioning YHD-1. Let me know if you’re bored and willing to sell.

What are the chances of buying random HP-1s from ebay then opening to find an aniso magnet version? Has that ever happened?

 

[JadeEast]

@Philimon Yes, I've played around with a bunch of different fabrics, foams, and some selective covering of front facing holes with transpore. A "phase-plug" in the middle of the driver even. Nothings moved things as significantly as the harder damping of the rear as that's not really feasible without blocking too much. If you look at the new Final they look to have utilized some front damping as well with metal mesh. That's interesting as I've not seen much use of front facing damping in older Orthos. Potentials for a bit of tuning or comfort and so much easier to pop in and out for light listening comparisons.

It would be great if ear pads were easier to DIY. Make up some versions and try them out. I've thought a number of times of having a go, as I've got a few pairs that are not exactly common sizes... but it's always looked easier to just buy online and hope things kind of work. Two sided tape is a wonder.

My Ansio pair of HP1 were random. I'm not sure if at the time it was common knowledge that there were variations, I was surprised to see it. Maybe Walt or someone else knew at the time and mentioned it. It might be a bit of a loot box / lottery / Schrodinger's HP1 to pick up one off Ebay. Nick might have a gauge on how common they might be.

 

[MDR30]

@MDR30 The PMB100 sample I have uses a version of that PMB driver as well... a many holes type magnet but no steel plate.

I figured that, good to know. The steel plates may have been a later development. One of the people involved in PMB (Peerless/Mikrofon-Bau), Willi Presutti, commented on the company's orthodynamic headphones in the thread below, which newer members may not be aware of:

https://www.head-fi.org/threads/id-these.192939/page-2#post-2316885

 

[GREQ]

What are the chances of buying random HP-1s from ebay then opening to find an aniso magnet version? Has that ever happened?

That's how I got mine, first try.
Then I sent it to Nick

 

[JadeEast]

New wine old bottles. Reinvent the wheel. ETC.
This is probably what got me started playing around with the damping of the front ages ago.
I'll find random felt disks with foam in a box or bag. I'd forgotten about it.
But some good info there... not sure this is the cure for the "ortho wall" or not.

https://patents.google.com/patent/US4389542A/en?q=orthodynamic&oq=orthodynamic

"The inventive cushion of reticulate foam material which may be arranged relatively of or around the diaphragm of the transducer or even as a thin layer in front of the diaphragm, does not require any supporting elements and rests against the ear or the head while enclosing the ear. The cushion may in addition be coated with a thin sound transmitting tissue serving the purpose of making contact with the skin more agreeable. It is further possible to provide the outer surface of the cushion with a thin elastic skin to accumulate the base reproduction without causing reflections."

 

[nick n]

New wine old bottles. Reinvent the wheel. ETC.
This is probably what got me started playing around with the damping of the front ages ago.
I'll find random felt disks with foam in a box or bag. I'd forgotten about it.
But some good info there... not sure this is the cure for the "ortho wall" or not.

https://patents.google.com/patent/US4389542A/en?q=orthodynamic&oq=orthodynamic

"The inventive cushion of reticulate foam material which may be arranged relatively of or around the diaphragm of the transducer or even as a thin layer in front of the diaphragm, does not require any supporting elements and rests against the ear or the head while enclosing the ear. The cushion may in addition be coated with a thin sound transmitting tissue serving the purpose of making contact with the skin more agreeable. It is further possible to provide the outer surface of the cushion with a thin elastic skin to accumulate the base reproduction without causing reflections."

On the subject of damping, and since you also mentioned the Final Audio ones , I THINK the Final Audio ones are using creative venting and using air pressure to damp the drivers, nothing else.
I did read the odd impression that said they could not handle too much without bottoming out ???
Curious design choice.
off to see what MyST is up to on their closed backs.

 

[Philimon]

Mods:
1. Remove grill. Im learning for vintage ortho that air suppression > air blocking. A closed seal is not required because driver distance + leather(?) pads means I dont have to worry about rear wave cancellation so much. A porous seal will pressurize air enough for damping driver plus benefit of less reflection and easier escape for excess energy etc.
The grill I learned is not metal. Its soft plastic with a texture similar to fishing line. Reminded me of transpore. I took a photo side-by-side.

2. Damping. Felt sealed with micropore tape directly on driver rear. Then light density open foam and felt in back of cup. I do not know if this is more or less damping than stock. Stock is wool disc and open foam.

Measured poorly and sounds bad. All shrill and no thrill. I tried before/after with pad riser. I don't think seal was broken.

Reasons to dislike T10: Small fit, uncomfortable particularly with these thin pads that are of too small diameter to cover entire front baffle which also makes it difficult to measure on EARS rig. I also cant get over the vintage orthos like T10 with thick grills and small holes scattered for sound to get through. Dont know how much difference it makes but it bothers me knowing its there. 3D printed baffles would be awesome.

edit: In conclusion, I am better at arts and crafts than headphone modding.