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Orthodynamic Roundup - Page 448

post #6706 of 19952
1/5/09 at 1:18am
Quote:
Originally Posted by cetoole View Post
Is that as big as the high end 'stats get? Dang, I thought they were bigger. My SR404 looks to be about 90mm high, but only half that wide, if I am even measuring the right place. Havnt opened them up or anything, I can just see the red ring inside, and figured that was the outer clamp for the stators. No idea though on the other big stats, ESP/950, O2, or HE90.
From in production stats ESP950 has the largest diaphragm radiating surface area: 46.6 sq. cm.

I am not sure what SR-007's radiating surface area is, but I believe it has a slightly smaller driver.
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Gear mentioned in this thread:

Yamaha Stereo Headphones
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Fostex T50RP Closed Ear Stereo Headphones
post #6707 of 19952
1/5/09 at 1:27am
doesn't the patent covering these square drivers explain how more of the surface area is active?
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post #6708 of 19952
1/5/09 at 1:31am
The RP woody could be made as a screw together. Due to the thickness of rim necessary to allow screws a good grip, the cup would need to be wider or get rid of more of the old baffle and cut off the driver mounting lugs to reduce it's size further. Then you could do it more easily. I was after the most solid/inert construction so it's put together with liquid welder or E6000 24 hour slow set rubber type glue over the largest driver plate area. However, the glue I used was purposeful in that I can fairly easily remove it if necessary without damaging anything, too much

Also, the bass can be tuned by increasing or decreasing the vent size. The detail level is fantastic as is the speed without that forced sound/loss of bass that lots of damping can induce. It's a heck of a driver. I'd love to devise a variable port... if only I had brains. A small carburettor screw valve might work.
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post #6709 of 19952
1/5/09 at 1:41am
Thread Starter 
Quote:
Originally Posted by ericj
doesn't the patent covering these square drivers explain how more of the surface area is active?
Could be. Have you got that patent handy?
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post #6710 of 19952
1/5/09 at 1:50am
Quote:
Originally Posted by wualta View Post
Could be. Have you got that patent handy?
"Whole Surface Driven Speaker" - Fostex Corp.

Whole surface driven speaker - Google Patents

Sure looks like it, anyway. I haven't read through it.
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post #6711 of 19952
1/5/09 at 1:57am
Thread Starter 
Quote:
Originally Posted by smeggy
The detail level is fantastic as is the speed without that forced sound/loss of bass that lots of damping can induce. It's a heck of a driver. I'd love to devise a variable port...
If by "lots of damping" you mean "too much damping", I agree. By definition, if the sound sounds "forced" or if the bass goes away, it's too much.

As for the port, why not drill several of varying lengths and simply cover/plug some and uncover others til you find the length that sounds best? No moving parts, no downdraft headphones.
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post #6712 of 19952
1/5/09 at 2:07am
Thread Starter 
Quote:
Originally Posted by ericj View Post
Sure looks like it, anyway. I haven't read through it.
That's a very interesting patent. It's a cross between a dynamic and an isodynamic-- the diaphragm is a rigid foamed-mica plate with a flexible surround. It reminds me of the flat tweeters Sony used to sell with their APM series speakers.

I hope that's not what's in the T50RP, but it could be. Totally different engineering goals..

PS: I just happened to recall that one of the reasons I suspected the T50RP driver wouldn't have quite the bass output of the earlier drivers was the thickness/stiffness of the diaphragm. I wonder if they figured they could find a middle ground between the foamed-mica plate and a thin, stretchy Mylar diaphragm...

.
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post #6713 of 19952
1/5/09 at 2:19am
I doubt that is the RP design, considering the RPs PCB extends beyond the magnet cage for all to see, it would be difficult, if not impossible, to add a flex surround in the middle of it. I'm guessing it's just what we thought it was.

Edit

I think I found what that belongs to... RP microphones.

"in the RP system, a flat, thin diaphragm is driven with absolute phase uniformity, in true piston motion."
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post #6714 of 19952
1/5/09 at 2:22am
well like i said i hadn't read through it. Maybe it's some other oddball idea that never went to market.

probably beats NXT at any rate.
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post #6715 of 19952
1/5/09 at 3:23am
Thread Starter 
Quote:
Originally Posted by smeggy View Post
I doubt that is the RP design, considering the RPs PCB extends beyond the magnet cage for all to see, it would be difficult, if not impossible, to add a flex surround in the middle of it. I'm guessing it's just what we thought it was.
I think you're right-- I'm pretty sure it's just a regular iso type. But they could have floated a small rigid plate on what looks like a conventional diaphragm. This would be similar to my idea for the Pioneer HPM drivers.


The patent does say "speaker", though maybe there is a microphone application. Fostex did sell a line of professional RP mics, although none I've seen disassembled show a mica plate.


Quote:
Originally Posted by ericj View Post
Maybe it's some other oddball idea that never went to market.
Agreed, though patents sometimes are mined for the good ideas they contain, so a given product might embody parts of one patent and parts of another. Willi Presutti implied that the PMB diaphragm was pleated to make it move more like a piston. A very weird piston, but...

By the way, pleats don't substantially increase a diaphragm's "grip" on the air. That depends more on the diameter of the diaphragm compared to the wavelength of the sound it's producing. Surface area is increased, but it doesn't help move more air. A downside is that there's more diaphragm mass to move, and thus lower efficiency.
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post #6716 of 19952
1/5/09 at 4:02am
I don't know about in practice, but conceptually, pleats allow for less rigidity of the diaphragm while keeping a stable geometry and allow for more excursion and evenness of excursion, although since the pleated sheets don't directly face the magnets it would be less efficient, and there's more mass to move, not to mention the magnets having to be farther away from each other to make use of the extra excursion.

I thought the T50RP drivers are made from Kapton (polyimide film). Also I really like tympani with the T50RPv2. Might have something to do with Fostex coupling the drivers to the cups. Also, I'm starting to really like the pads, too. Really quite soft and comfy, and don't make my ears sweat even after extended periods of listening. Nice.
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post #6717 of 19952
1/5/09 at 5:25am
I can't hear anything wrong with the soundstage of the HOK and the pads for sure are solid and sealed. Maybe I've got to measure it, but without listening too carefully, it seems to be the width of my head least. Should it be much larger? If it sounds odd, then I'll listen again. The Grundig also has nice up/down orientation in addition to left/right. I've not checked that so carefully on the HOK yet. (but taking the Grundig apart and putting it together too many times, the narrow cup opening for the cables seems to have cut one of them off :-(
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post #6718 of 19952
1/5/09 at 5:34am
Yeah, the pads are pretty nice. I'm good for a long sessions with mine. As the days and playtime wear on the RP is settling in very nicely. I pitted them against the t30 and T50v2 again and the RP now has these two beat for bass, modded as I have them all.

I'm in love
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post #6719 of 19952
1/5/09 at 6:44am
Quote:
Originally Posted by Faust2D View Post
Yeah, it seems that 60-65mm is the right upper limit for planar headphone driver. It has to be slightly bigger than average sized ear to sound good and have nice bass as Stax and Fostex proved.
Forget ye not the 16 square inches of the Jecklin electrostatic.
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post #6720 of 19952
1/5/09 at 6:47am
I wonder if thick leather could be an alternative to wood? Could it work? Any ideas about that?
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Gear mentioned in this thread:

Yamaha Stereo Headphones
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Fostex T50RP Closed Ear Stereo Headphones
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