[TzeYang]

Dear DIYers,

I'm going to ask someone to build me a PIMETA so i can drive the Yamaha HP-1.

Do you think the PIMETA is capable of driving the Yamaha HP-1 to decent levels?

I don't have the technical background, so can anyone here please enlighten an ignorant soul?

Thank You.

 

[ericj]

Orthodynamic headphones are relatively easy to drive. I have a pair of YH-2 headphones that sound good with any amp I've plugged them into.

I don't know the specs of the HP-1, but the YH-2 is about 270 ohms, and due to the planar construction the load is not particularly inductive.

The pimeta should be more than adequate.

 

[TzeYang]

thank you ericj.

The HP-1 is rated at 120ohms, and it will take up to 10watts of power O_O.

That's why i'm a little bit worried of it's efficiency.

 

[ericj]

Ah, I understand your concern.

Well, if nothing else, if you search this forum (and others like it), there are a few fans of planar drivers here, and so far nobody has mentioned any trouble driving them.

I'd sure like to get my hands on a pair of HP-1 headphones one of these days. I'm still trying to get all the decomposing foam rubber bits out of the right-side driver of my YH-2's. That crap gets stuck between the ferrite and the membrane and causes nasty distortion. Eventually I'll have it all out.

By the way, have you seen this site?

http://home.hccnet.nl/joop.nijenhuis/headwize/rhp1e.htm

Very detailed instructions for the proper refurbishment of Yamaha ortho cans.

 

[wualta]

Quote:

Originally Posted by ericj Well, if nothing else, if you search this forum... there are a few fans of planar drivers here, and so far nobody has mentioned any trouble driving them.

They're an easy load, but they're not very efficient by today's standards, so you'll need an amp with a decently high rail (aka power-supply) voltage. I find a standard CMoy to be perfectly adequate even with bass boost, but I'm not a headbanger.

Quote:

Originally Posted by ericj I'd sure like to get my hands on a pair of HP-1 headphones one of these days. I'm still trying to get all the decomposing foam rubber bits out of the right-side driver of my YH-2's. That crap gets stuck between the ferrite and the membrane and causes nasty distortion. Eventually I'll have it all out.

Wow! Any possibility of your posting photos of this? I've got two HP-1s and two of the later YH-1s, and haven't come across a foam problem yet, but knowing how many foams from the '70s came undone, it's surprising that I haven't seen what you've seen.

 

[ericj]

Quote:

Originally Posted by wualta /img/forum/go_quote.gif They're an easy load, but they're not very efficient by today's standards, so you'll need an amp with a decently high rail (aka power-supply) voltage. I find a standard CMoy to be perfectly adequate even with bass boost, but I'm not a headbanger.

There's a thread on That Other Forum where an ortho enthusiast recommends gluing a disc of felt to the back of the driver to improve bass response. I haven't tried this on my YH-2's yet.

But yes, they do need some voltage gain. A pimeta with two 9v batteries ought to do it, though.

Quote:

Wow! Any possibility of your posting photos of this? I've got two HP-1s and two of the later YH-1s, and haven't come across a foam problem yet, but knowing how many foams from the '70s came undone, it's surprising that I haven't seen what you've seen.

Well, there's nothing to take pictures of anymore, really. I threw away what was left of the foam damping material a week ago.

When i got them off ebay a couple years ago they had some bad distortion and i basically put them in a ziplock bag and forgot about them. I'd only paid about $25 anyway.

When i found the url i mentioned above, I realized that there IS a use for my old pair of MDR-V200's, stole the earpads off them, and started opening up the YH-2's.

What i found was bits of brown foam all through 'em. The foam damping material behind the drivers had just completely broken down.

FWIW the YH-2 and HP-1 construction is identical. They even have the same size drivers. The YH-2 is just a funky maroon color. At least mine are.

Several rounds of softly puffing air at the drivers later, i think i have almost all, if not all of it out. I need to do some more listening tests.

I can only presume that it was a low quality foam, or that the headphones were used in an environment unfriendly to foam rubber.

The pictures in the refurbishment url show a yellow foam in the HP-1, that appears to be in good condition. Probably better foam.

Once I'm satisfied that i've got these as clean as they can be, i'll probably start experimenting with felt and poly-fill as replacement damping material.

 

[wualta]

Quote:

Originally Posted by ericj There's a thread on That Other Forum where an ortho enthusiast recommends gluing a disc of felt to the back of the driver to improve bass response.

Yeah, that crazy, enthusiastic ortho-enthusiast.. cough, cough. Ol' whatsisname..


Quote:

Originally Posted by ericj A pimeta with two 9v batteries ought to do it, though.

Agreed. If that isn't enough, something's wrong.


Quote:

Originally Posted by ericj What i found was bits of brown foam all through 'em. The foam damping material behind the drivers had just completely broken down. I can only presume that it was a low quality foam, or that the headphones were used in an environment unfriendly to foam rubber.

Yikes, must've been a very unfriendly environment indeed, but yeah, it's amazing the 'phones weren't completely ruined. I've never owned a YH-2, but I'd think the foam used would be the same as in the YH-1. Maybe not.


Quote:

Originally Posted by ericj FWIW the YH-2 and HP-1 construction is identical. They even have the same size drivers.

I'm pretty sure the drivers in the YH-2 and HP-2 are both 46mm diameter while the HP-1 and YH-1 drivers are 55mm.


Quote:

Originally Posted by ericj I'll probably start experimenting with felt and poly-fill as replacement damping material.

I started with polyester fiberfill and moved on to felt because it was far easier to glue if that was necessary, and it was certainly more dense. The problem becomes one of finding the densest possible felt in a reasonable (1/8") thickness. Whatever happens, be sure to slide on over to the Other Forum and keep us aware of your experiments and the results.

 

[ericj]

Quote:

Originally Posted by wualta /img/forum/go_quote.gif Yeah, that crazy, enthusiastic ortho-enthusiast.. cough, cough. Ol' whatsisname..

You know what, you look just like him.

Quote:

Yikes, must've been a very unfriendly environment indeed, but yeah, it's amazing the 'phones weren't completely ruined. I've never owned a YH-2, but I'd think the foam used would be the same as in the YH-1. Maybe not.

One possible theory is that the original owner used some sort of petrolium distillate to lubricate the swivle point at the back of the capsule. Something like WD40 (which is mostly kerosene) would be gradually sopped up by the foam rubber, and would possibly weaken it.

The refurbishment instructions recommend WD40 but i think spray silicone is probably a better idea. It's far less volatile if nothing else.


Quote:

I'm pretty sure the drivers in the YH-2 and HP-2 are both 46mm diameter while the HP-1 and YH-1 drivers are 55mm.

Yes. my mistake. I misread the specs for the HP-1.


Quote:

I started with polyester fiberfill and moved on to felt because it was far easier to glue if that was necessary, and it was certainly more dense. The problem becomes one of finding the densest possible felt in a reasonable (1/8") thickness. Whatever happens, be sure to slide on over to the Other Forum and keep us aware of your experiments and the results.

Yes, lets continue this discussion over there.