[facelvega]

Quote:

Originally Posted by wualta /img/forum/go_quote.gif If you can find a pmb4 in Kirk's posts on page 11, I'll send you that 300 dollars. You're thinking of the pmb6, perhaps.

Doh! I'm getting practice in for being an absent-minded perfesser. Just ask my students. I did get that 44mm bit right, though, didn't I? I'm pretty sure on that front. Of course, it's nearly 5 in the morning on a Friday night in Berlin, so I can scarcely be trusted--- though nevertheless, technically in this town that counts as going home early. This may also cast some light on how certain professors grew absent-minded in the first place. I'm really not the one to say.

Let me try to add something useful to my Duggeh-esque whisky-soaked rantings. Is there any reason within the realm of an isodynamic driver to expect that a 55mm diameter will outperform 44mm? Can a mere HOK80-2 hold its own with a properly-modded TDS-5? It seems that although decent performance can be squeezed form iso drivers in the 30-40mm range, that this can only extend so far. I've claimed in another thread that iso drivers need circumference to deliver bass, but upon thinking it through I recalled the smallest iso drivers I've yet heard, the HP-50a, had far more bass than any of the others. Is there a general rule we can expect to apply in these matters?

 

[AudioCats]

Quote:

Originally Posted by swt61 /img/forum/go_quote.gif Those Soviet semi clones are pretty interesting. My guess is that they were manufactured in China and the Soviet version sourced the same frame. ?

when was this Soviet copy made? if it was during the cold war era then I don't think China could have made any part for it. Sino-Soviet relationship broke up after 62 and didn't recover till 89, also China probably didn't have what it takes to make these frames during most of the YH-1 production period.

 

[ericj]

didn't have what it takes? plastic injection molding isn't that hard.

This website sells (among other things) NOS chinese mechanical watches of higher quality than today's average chinese watch, from about that same era:

http://www.pmwf.com/Watches/WATCHSAL...SalesTable.htm

But in principle i agree - russia probably made these themselves as much as they could.

 

[AudioCats]

injection molding isn't hard, the main problem was the material. Before the 90's Chinese plastic material either have lower quality or, for the good stuff, low production quantity. Not a lot of higher quality raw plastic were imported for production either. It is not likely that china have mass produced those frames.

I am not surprised that those 70's NOS watches are very well made. Production of those 17-jewel model were pretty low, they were considered as higher end models demanding lots of labor from very skilled workers, probably cost 6 month salary of an average engineer in the 70's, or even more. Some could even be models made specifically for governement purchase ("internal supply" sold only within the goverment system and to party members), not available to the general public. On the other hand, the current chinese mass production stuff are made to be inexpensive, say a $40 walmart watch probably worth around $30 in China, that is about one to three days salary for an engineer (depends on the job location). Those high end NOS and current mass production are more like apples and oranges...

Back to the isodynamics.... So the major problem of a isodynamic driver is always not enough bass? Has there ever been a model that is too boomy?

 

[wualta]

Quote:

Originally Posted by Inkmo What about dryer lint? Or socks? You suggested I try stuffing either into my T40...

Socks work for badly-tuned ported speakers, so why not headphones? That was speaker comedy at work, but the dryer lint might actually work, since it can be squished into little patties of about the right size and thickness.

Wet it, form it, let it dry or iron it flat. I bet it'll work as a damping pad. Without wetting it, using it as-is, try stuffing your T40's cups full of the stuff. Cram it in there as tight as you can. It may not be ideal or perfectly repeatable, but it should be enough for proof-of-concept and best of all, you can do it with materials already at hand.

 

[facelvega]

Quote:

Originally Posted by AudioCats /img/forum/go_quote.gif Back to the isodynamics.... So the major problem of a isodynamic driver is always not enough bass? Has there ever been a model that is too boomy?

Bass isn't a problem with all isodynamics by any means, it's just one of the ways to justify a larger circumference. As I say, the HP-50a had very strong and reasonably tight bass indeed, enough so that Duggeh said he'd never heard another supraaural 'phone that could compete, and I can agree. The problem with them is that their top end clarity only goes so far. So in that sense you can say they were too boomy, though probably some serious damping would have solved the problem.

 

[setmenu]

My own transducers had lots of low end grunt,you could feel the breeze!
I did initially go the mechanical damping route but found there was a penalty
to be paid at the top end.
They sounded most transparent and delicate with nothing other that a basic
protective grill between diaphragm/ribbon and the outside world,and running the ribbon as slack as practical.
The bass hump was controlled with a simple cap,a brutal but temporary approach.
The above is the reason I want to explore electrical solutions to the problem, before getting any further into resistance damping.



.

 

[setmenu]

You know, these things are not that difficult the make.
With all the enthusiasm and knowledge here, we could
design and build our own ideal planar phones!
Much more fun than tinkering with old ones I can
assure you!

wualta
What do ya think!
Could be a fun excercise...

.

 

[wualta]

Set, you bring up several interesting points.
I too would love to see you succeed in your ribbon project, and I think it can be done, and from the way you've described the Wharfedale, it's already been done! I would still like to see closeup photos of the Wharfedale diaphragm showing how it was suspended like a ribbon. I tried to get a 'dale for myself but the auctions went high and I was fighting a 2:1 dollars-to-pound ratio.

Now-- do a planar? from scratch? ..Ribbon, or plain planar?

Quote:

Originally Posted by AudioCats So the major problem of a isodynamic driver is always not enough bass?

To the extent that headphones always seem to be short of providing the sock-in-the-chest feeling good loudspeakers can, yes. Depends on what you mean by "enough" bass. Until 1981 and the introduction of the YH-100 (and maybe the YH-1000 and HP-1a, which I haven't heard) the only isos with real bass were the Fostex T50 and the T30 with their relatively huge diaphragms. The YHD series has no trouble producing bass but great trouble delivering it to your ears. YH-/HP-1 when damped has excellent bass quality but generally needs some low-bass boost to sound really great.

It bears repeating: an underdamped diaphragm, whether 'stat or dynamic or iso, will not give satisfying bass, no matter how much boost you give it.

Quote:

Originally Posted by AudioCats Has there ever been a model that is too boomy?

Any boominess is too much. If you mean too bassy, then yes, certainly. YH-100, YHD-1, T30 are all tilted up at the bass end. That's a promising sign, because it means they'll require and take lots of damping, so the result will be excellent transient response and a flattish response curve.

.

 

[ericj]

Alright, I've spent the last few hours listening to my Maior RPT-50's.

Much of it in the "Unsorted" directory on my mp3 server. This is dangerous business, because i once participated in a noise project, and my bandmate used to download music at my house. You can go straight from Men Without Hats to Merzbow. Or worse yet, one of our own impenetrably bad tracks - our own sound was somewhere between Merzbow and Whitehouse.

Though i admit that discovering the John Spencer Blues Explosion in there was interesting and pleasing.

The maiors have bass that is both warm and commanding, with plenty of smack. Good basso continuo on organ recordings. You can hear every part of the sound coming out of a bass guitar, and the low resonance of bongos in tracks like Ben Harper's "Burn One Down".

Mids are nice and crisp, highs are clear and do not fatigue the listener. If a track has been mastered with the chorous filter bumped up, you hear all the resonance of the vocals. There isn't quite as much air to them as there is to my K145, but i realize that this statement is meaningless for my readers.

Anybody got any questions? I'm not sure what else to say. Recommend some music if you like.

 

[ericj]

Quote:

Originally Posted by AudioCats /img/forum/go_quote.gif injection molding isn't hard, the main problem was the material. Before the 90's Chinese plastic material either have lower quality or, for the good stuff, low production quantity. Not a lot of higher quality raw plastic were imported for production either. It is not likely that china have mass produced those frames.

fwiw, if the YH-2 is representative, it would be a bit of a stretch to call the plastic used in the HP and YH series Yamaha frames "higher quality". I believe the technical term for it is "cheese".

Be careful with 'em. They are built so that most parts of them are unlikely to break, but they used those damned notched 'drill' type screws, and it may be worthwhile to see if they can be replaced with #4 brass wood screws, because otherwise, every time you remove them, you strip out the plastic a little bit.

If you break the little post on the earcup ball-socket, we have no ideas for fixing them that are both good and tested.

I think solvent welding with methyl-ethyl ketone, reinforced with a brad nail, might just do it, if the nail fits snugly enough. But nobody has tried this.

 

[swt61]

Quote:

Originally Posted by ericj /img/forum/go_quote.gif If you break the little post on the earcup ball-socket, we have no ideas for fixing them that are both good and tested. I think solvent welding with methyl-ethyl ketone, reinforced with a brad nail, might just do it, if the nail fits snugly enough. But nobody has tried this.

LOL. I tried precisely that when my YH-1000's broke in 85'. It was a panel nail instead of a brad nail, but in any case it didn't hold up for more than a few days.

I was so eager for any remedy, but alas none worked.

 

[ericj]

Quote:

Originally Posted by swt61 /img/forum/go_quote.gif LOL. I tried precisely that when my YH-1000's broke in 85'. It was a panel nail instead of a brad nail, but in any case it didn't hold up for more than a few days. I was so eager for any remedy, but alas none worked.

Did you use a glue or a solvent weld? I figure if any glue is going to bond at all well with this stuff, it'll have to melt it's way in.

 

[wualta]

Quote:

Originally Posted by ericj Alright, I've spent the last few hours listening to my Maior RPT-50's.

We should point out for the casual viewer that as near as we could tell without sending these things back and forth between Michigan and Utah, this "Maior" was the rare, renowned, redoubtable, mythical, magical, vaunted, touted, tooted, revered, envied, much-talked-about original one and only Fostex T50 in OEM disguise. Even Fostex's original North American importer didn't know anything about them.

However, we did send them from Utah to Michigan to be compared back to back on the XR10 digital amp and it turned out that OEM in this case didn't translate into "identical to the original T50". Compared to my T50, the Maior has an elevated treble and reduced bass (despite ericj's kind words about it below), almost as if it had been "voiced" for a particular [Europe?] market (this could be accomplished simply by increasing the diaphragm tension). So while the Maior is a nice 'phone, it wasn't anything like what we were hoping for.

Regardless, if anyone knows anything about Maior (Brazilian? Portuguese? something else entirely?), please let us know. I should point out that the Maior does have all the virtues of an isodynamic 'phone. It just lacks the well-judged overall balance of the T50.

This throws doubt on the NAD lookalikes too.

Quote:

Originally Posted by ericj The Maiors have bass that is both warm and commanding, with plenty of smack. Good basso continuo on organ recordings. You can hear every part of the sound coming out of a bass guitar, and the low resonance of bongos in tracks like Ben Harper's "Burn One Down". Mids are nice and crisp, highs are clear and do not fatigue the listener. If a track has been mastered with the chorus filter bumped up, you hear all the resonance of the vocals. There isn't quite as much air to them as there is to my K145, but i realize that this statement is meaningless for my readers. Anybody got any questions?

Sounds good, but I don't hear you saying "Wow!" [and now we know why]

Try some binaural. They won't excel at this, but the effect should be there, and they shouldn't sound closed. The planar coherence should give the phones a leg up despite their mechanically damped nature.

Quote:

Originally Posted by ericj fwiw, if the YH-2 is representative, it would be a bit of a stretch to call the plastic used in the HP and YH series Yamaha frames "higher quality". I believe the technical term for it is "cheese".

Unfortunately true. And yes, it is representative. Plastic that seems to be partly made from powdered milk. We've all gotten used to modern plastics which are [usually] amazing compared to their counterparts of 30 years ago. The Yamas are from the era that gave "plastic" a bad name. Just ask Dustin Hoffman.

Quote:

Originally Posted by ericj Be careful with 'em. They are built so that most parts of them are unlikely to break, but they used those damned notched 'drill' type screws, and it may be worthwhile to see if they can be replaced with #4 brass wood screws, because otherwise, every time you remove them, you strip out the plastic a little bit.

Unfortunately true also. Can't stress what ericj says enough. The screw holes are surrounded with positively stingy amounts of "meat". Almost as if there was a Japanese shortage of mediocre plastic. I've never completely stripped out a screw, and I've gone in for maybe six or seven opens-and-closes in some of my Yamas, but I can tell there's a finite number of these operations built in.

Quote:

Originally Posted by ericj If you break the little post on the earcup ball-socket, we have no ideas for fixing them that are both good and tested. I think solvent welding with methyl-ethyl ketone, reinforced with a brad nail, might just do it, if the nail fits snugly enough. But nobody has tried this.

Unfortunately true! I just dropped my Old No. 1 YH-100 and the strut didn't break all the way through but something got munged in the socket-and-ball so one earcup is permanently ****ed-- er, cocqued-- in the wrong direction. Still wearable, but that strut will eventually crack all the way through and then I'll try the long thin woodscrew fix. Even if that doesn't work, the YH-100's driver is the same size as the YH/HP-1's.

.

 

[swt61]

Quote:

Originally Posted by ericj /img/forum/go_quote.gif Did you use a glue or a solvent weld? I figure if any glue is going to bond at all well with this stuff, it'll have to melt it's way in.

Yeah I used methyl-ethyl ketone from a rubber supplier. I knew that glue wouldn't hold. I thought about wrapping it with a thin strip of fiberglass and resin, but I never got around to trying that.