[wualta]

Quote:

...truly open... ie, undamped or extremely light like the LCD or HE is what I'm getting at. The old NAD is terrible in the open ... in it's native state [it] sound pretty awful to me.
 
The loading I'm referring to is air coupling. There are certain drivers which need close coupling (high loading) and others that need less. I'm not an audio or physics expert so ... all I'm going on is my extensive tests and trials which are hardly scientific but all I have... ...if you tap the NAD or fostex drivers you'll hear a .. sound ..that comes through when played.

Now I understand (or think I do). Don't worry, no one's questioning your knowledge of audio or physics-- we just wanted to hear you say it a different way so we could be a little more certain what it was you were describing. And what you say about the plastic Fostex driver having a sound if tapped is true. Once the driver is coupled (that word again) to the enclosure, this sound will, as you point out, change or go away, depending on how well resonance in the enclosure is handled, which is good, because I believe the original question concerned finished designs and orthos that were open-back in stock form, although the problems of diying an open-back ortho from scratch are certainly apropos as well.
 
Quote:

1.) All three share the common ancestor : the 70's fostex T50; the NAD being its OEM, the T50RP a cost reduced descendent & the LCD-2 a tweaked & improved version.
 

I'd call the '70s T50 the grandfather of the LCD-2 (ie, not the direct ancestor, but definitely related) and the T50RP an almost entirely different design meant for a very specific market. I've never seen the LCD-2 diaphragm in its entirety; I'm guessing, based on photos of partially-disassembled LCD-2s, that there's no center electrode (though there may be mechanical limiters in strategic spots, as there were in the Technics design) such that the entire diaphragm is free to move, thus making the LCD-2 a descendant of the T50 rather than the PMB/Yamaha. Beyond that, I'm certain some of the black art of headphone building has gone into the LCD-2 and that some of these are partly responsible for the reported greater headstage of the LCD-2.
 
In earlier discussions of this, we talked about getting the mass of the diaphragm down as much as possible and the area of the diaphragm up as much as possible and playing with the tension (and possibly adding a compliant annulus around the diaphragm) so that there'd be no need to damp a major resonance in the bass with headstage-sucking heavy absorbing material. Where Audeze placed the main resonance and how they dealt with it (damping, absorbing, reflecting, loading, coupling, primping, braiding, etc) are questions that can only be answered by someone who owns an LCD-2 and can measure such things. Tyll's setup might give us some answers, or at least better guesses. Even as we speak, he's heading out to the industrial supply store to get a dial gauge to measure diaphragm tension, figuring he can use it later on his brake rotors, and who can blame him.

 

[DefectiveAudioComponent]

Quote:

Now I understand (or think I do). Don't worry, no one's questioning your knowledge of audio or physics-- we just wanted to hear you say it a different way so we could be a little more certain what it was you were describing. And what you say about the plastic Fostex driver having a sound if tapped is true. Once the driver is coupled (that word again) to the enclosure, this sound will, as you point out, change or go away, depending on how well resonance in the enclosure is handled, which is good, because I believe the original question concerned finished designs and orthos that were open-back in stock form, although the problems of diying an open-back ortho from scratch are certainly apropos as well.
I'd call the '70s T50 the grandfather of the LCD-2 (ie, not the direct ancestor, but definitely related) and the T50RP an almost entirely different design meant for a very specific market. I've never seen the LCD-2 diaphragm in its entirety; I'm guessing, based on photos of partially-disassembled LCD-2s, that there's no center electrode (though there may be mechanical limiters in strategic spots, as there were in the Technics design) such that the entire diaphragm is free to move. Beyond that, I'm certain some of the black art of headphone building has gone into the LCD-2 and that some of these are responsible for the reported greater headstage of the LCD-2.
 
In earlier discussions of this, we talked about getting the mass of the diaphragm down as much as possible and the area of the diaphragm up as much as possible and playing with the tension (and possibly adding a compliant annulus around the diaphragm) so that there'd be no need to damp a major resonance in the bass with headstage-sucking heavy absorbing material. Where Audeze placed the main resonance and how they dealt with it (damping, absorbing, reflecting, loading, coupling, primping, braiding, etc) are questions that can only be answered by someone who owns an LCD-2 and can measure such things. Tyll's setup might give us some answers, or at least better guesses. Even as we speak, he's heading out to the industrial supply store to get a dial gauge to measure diaphragm tension, figuring he can use it later on his brake rotors, and who can blame him.

I didn't quite get the compliant annulus part. Could you explain that a bit more?
 

 

[wualta]

A non-active part of the diaphragm that's there simply to let the entire diaphragm move as a plate instead of "doming up" in the center. Rather like the half-roll surround of a typical woofer.

 

[DefectiveAudioComponent]

Quote:

A non-active part of the diaphragm that's there simply to let the entire diaphragm move as a plate instead of "doming up" in the center. Rather like the half-roll surround of a typical woofer.

If one instead corrugated the entire square membrane, like the ID-1, wouldn't that do the same trick?

 

[MDR30]

Made me think of this:
 

 
Technics EAH-830 driver, photo courtesy Mr Wualta.
 
How might this strange animal sound?

 

[scompton]

Back to Tyell's offer, I'm planning on sending him all of my orthos.  I wanted to send them before I left for a 2 week vacation, but didn't have time.  I'll be sending a few at a time starting after a meet June 18. 
 
Edit:  It takes hours to read this thread after not reading it for 2 weeks.  And I hate Spanish keyboards.

  Of course, Spaniards probably hate US keyboards.

 

[wualta]

Quote:

If one instead corrugated the entire square membrane, like the ID-1, wouldn't that do the same trick?

No, since the 'brane is still clamped at the top and bottom and only the center of it can move an appreciable distance, corrugations or not. The picture I have in mind is one of those flat passive radiators in loudspeakers. Not saying this is what Audeze did, mind you, just an idea we'd tossed around in the last year or so.

Quote:

How might this strange animal sound?

 
Rather blah, surprisingly. Lots of good ideas packed into a goofy wrapper there. Wish they'd had another run at making an ortho.
 
 

 

[DefectiveAudioComponent]

Quote:

No, since the 'brane is still clamped at the top and bottom and only the center of it can move an appreciable distance, corrugations or not. The picture I have in mind is one of those flat passive radiators in loudspeakers. Not saying this is what Audeze did, mind you, just an idea we'd tossed around in the last year or so.
 
 

Wouldn't the membrane have to be very stiff (thick?) to stay completely flat all the time then, and not dome up at all? Since the annulus would still need to grab the edges, even if it would be very flappy? Or is there a nice strong flappy material out there perfect for the annulus?
 
By the way, for the new crowd here, i'd like to mention that there are still some vintage orthos that are in the wikiphonia list but have not been found by anyone in here yet. For instance, the Hosiden DH-80S

 

[Antistase]

Thanks Sim1,
 
following your suggestion I tried to simply put on top of the existing pads a pair of original K340 pads I had around. You are right: the sound is gearing toward the right direction. The presentation is now drier than the ID1 but definitely of the same tonal kind.
 
 
 
Quote:

 
 
SS-100 are very nice headphones but it's hard to open... and imho not too much place inside to play. Inside you'll find just double yellow biscuits only.
Outer grlls twists but I can't remeber now if its clockwise or opposite. I wouldn't change anything inside it's ok, you can shape the sound with pads much better.
I tried SS-100 with O2 pads and those are the pads they need. Unfortunately pads were not firmly attached (compression was as good as it could) but used over original ones. That is I guess exactly what you look for.
Wide soundstage, trebles are getting slightly more gentle, it adds precision and moves SS-100 sonically towards stats presentation. And bass gets better, stronger.
The only problem that the construction (not too much pivot on headband, etc) makes it not so convenient to use with 1'' thicker pads or you need to bend them slightly to fit perfectly.

 

 

[Armaegis]

Regarding the complaint annulus thing...
 
Most of the pictures I've seen of diaphrams seem to have the traces running to the very edges, and I would assume the membrane are of constant thickness throughout. Would it be possible (well, more like economically feasible) to create a diaphragm with thinner outer edges, and contain the majority of the traces to within the inner thicker membrane? This would make the traced area stiffer (relative to the edges) and more planar rather than dome out.

 

[wualta]

 
Quote:

1. Wouldn't the membrane have to be very stiff (thick?) to stay completely flat all the time then, and not dome up at all?
 
2. Since the annulus would still need to grab the edges, even if it would be very flappy? Or is there a nice strong flappy material out there perfect for the annulus?
 
3. By the way, for the new crowd here, i'd like to mention that there are still some vintage orthos that are in the wikiphonia list but have not been found by anyone in here yet. For instance, the Hosiden DH-80S

1. No, because this is an ortho driver and, theoretically at least, the uniform magnetic field applies force equally over the active surface of the diaphragm: iso-dynamic. For a similar reason a flat passive radiator on a speaker can be a simple disc of foamcore or even plain styrofoam-- the pressure inside the speaker box is the same over every point of the passive diaphragm, so there's no force trying to make the disc flip or ripple. 
 
2. Speakers use lightweight foam formed into half-roll shapes. Take a look at the socalled re-foaming kits for woofers and passives being sold online. Ideally the material would be acoustically dead plus have some appreciable vibration absorbing properties. I'm not claiming this would be easy to design or make or that it wouldn't create twice as many problems as it was meant to solve. It's just a thought experiment to explore ways we might, without resorting to rigidity, let a driver move as a flat plate, which is what it wants to do and what we want it to do.
 
3. Yeah, come on, you new crowd-- get out there and find the Missing Orthos. There aren't that many left, so it shouldn't take you more than a few minutes. Har. Seriously, see if you can find the mythical HP-1a.
 
 
Quote:

/img/forum/go_quote.gif Most of the pictures I've seen of diaphrams seem to have the traces running to the very edges, and I would assume the membrane are of constant thickness throughout. Would it be possible (well, more like economically feasible) to create a diaphragm with thinner outer edges, and contain the majority of the traces to within the inner thicker membrane? This would make the traced area stiffer (relative to the edges) and more planar rather than dome out.

Remember, we want to avoid extra stiffness and rigidity in our diaphragms-- the metal traces stiffen them up enough to require "dummy" traces in some cases to prevent sudden changes in diaphragm stiffness over the surface. Extra material means more mass, less air damping, lower efficiency.  But the Russians did a variation of your thinking on I believe the TDS 15: the magnets and voicecoil traces only cover the center area of the diaphragm. I don't know if this helped or hurt.
 
 

 

[Sim1]

Quote:

Remember, we want to avoid extra stiffness and rigidity in our diaphragms-- the metal traces stiffen them up enough to require "dummy" traces in some cases to prevent sudden changes in diaphragm stiffness over the surface. Extra material means more mass, less air damping, lower efficiency.  But the Russians did a variation of your thinking on I believe the TDS 15: the magnets and voicecoil traces only cover the center area of the diaphragm. I don't know if this helped or hurt.
 

Afair the Fostex T50rp drivers have zigzag traces to improve diaphragm stiffness. I guess that's the only reason why they're not stright lines.
And speaking of diaphragm thicker in the center - imho SS-100 driver diaphtragm (so that should be truth for all variants of T50) are corrugated mostly close to the edge, and are rather flat in the center under voicecoil traces. So I think this is substitution of thickness variation.

 

[BoilermakerFan]

Well, I see that Rick, aka Warren Audio, aka Fidelity Audi, is now banned.
 
I'm really disappointed to report that he took advantage of my trust and I bought a cable from him for my KH-83s over 6 weeks ago and it has never shown up.  I filed with Paypal so we'll see how that goes.  He's blown off all of my attempts to reach him for a refund. 
 
I will put this out to all readers, if Rick contacts you regarding his supposedly developing orthos, stay far away or if you really can't resist, order them COD.  Personally, I don't believe they will ever exist in physical form, let alone become a viable commercial offering. 
 
Rick and I had many transactions that went smoothly and emailed regularly, so I'm stunned that he would hose me like he did, but lessons were learned and karma will come back to kick him in the balls. 
 
EDIT:  On June 2 he sent me an email with tracking info.  When the cable shows up and assuming it is in usable condition, I will further edit this email accordingly.  Thanks.

 

[Kabeer]

delete pls !

 

[DefectiveAudioComponent]

I decided to buy yet another vintage orthodynamic. Mainly because I liked the look of these grilles
Completely open mesh, and also vents around the edges, as the picture shows.
Drawback - it was competely packed with crumbling sticky goo that had once been foam.