Exactly. I'm thinking something's not right somewhere. "High" impedance (we had much higher back in the day) is no problem for one of these amps/receivers if everything (including the headphone) is working as it should. Do a basic check before buying another amp. Start with a DC offset test...

MuZo2: Might work, at that. Let us know.

Quote: Without going back to the Yamaha drawings to check, it looks good to me. Did you find a source of magnets like that?     Quote: Looks pretty ravagey to me. Now we know it's a pleated diaphragm, so thanks for doing that. As for why HOK (and others) sometimes made drivers...

Quote: If you're talking about the SFI tweeters, the diaphragms are most likely the same, and they're already push-pull, but since the back magnet is not perforated, the air trapped in there acts like a stiff spring, making the diaphragm tension effectively higher. That, plus the reflex...

Quote: Exactly. It's the 4-pi speaker-in-a-tree effect. But I'd imagine most tweeters don't have the excursion capability to produce bass anyway. They're engineered to be tweeters and nothing else.   Quote: Uh oh. This takes us all the way back to the beginning of the thread and...

Indeed. One of the fundamental tenets of this thread is that vintage ortho 'phones can often (not always, but often) provide almost any kind of sound, including bass sound-- call it your personal bassstyle-- from frighteningly tight to mellow and all the way to downright floomfy, depending on...

Don't forget that the HPM tweeters are piezoelectric and as such are capacitors and will read open circuit (infinite ohms DC), though not infinite impedance, which is ohms AC (audio is AC). Use a capacitance meter to test them.

As RGD pointed out, the Yamaha's headphone outputs are not anything special, though I like to imagine they used a "pad"-type resistor network instead of a simple pair of dropping resistors. The Orthodynamics were in fact close to the "standard" (cough) headphone output impedance and in addition...

Guys, don't forget to check out the turntable (+cartridge), speaker and vintage audio forums over at AudioKarma. Skylab's there-- you should be too. Sure, we have our share of crazies, but you're already used to that. Come take a look. The two search engines [mostly] work, and you'll probably...

Quote: That was my experience too. Surprisingly little difference with most (but not all) of the back taken out.

Depends on which "sound" it is you don't want to change. Depends on where you live, too. Many enterprising folks on the thread have found all sorts of substitute earpads. Some even have made their own. Use the dedicated search engine: http://headfi.qix.it/megathreads/orthodynamic-roundup

Whenever anyone asks a question about "enough power", I always think of the Magneplanar website's response, and I paraphrase: "How effin' loud do you want it?"    As long as you don't make the amp spend a good bit of its time in severe clipping (adding the powered sub would greatly help...

Yes, those non-stock pads may turn out to be a blessing if the covering is soft and pliable.   Doing a quickie look-around for the duct seal stuff, I find it's more often called "duct seal compound" or even "duct sealant". Amazon sells it (though the shipping kills the deal), Lowes, Home...

Quote: Sure. Open-back is especially risky. It means you have to get the [preferably large] diaphragm right up on the ear, or else have really really good sealing and density in your pads. An extreme case would be the oil-filled pads Koss and Sharpe used back in the day. With tight seals...

Quote: You're supposed to be the grownup and make sure it doesn't "has a spike".  Once the silistor is jumpered, you can determine if the 'phone is damaged. If not, replace the silistor.