Head-Fi.org › Forums › Summit-Fi (High-End Audio) › High-end Audio Forum › PWB ( Peter W. Belt ) Yellow ---and Black---Stats
New Posts  All Forums:Forum Nav:

PWB ( Peter W. Belt ) Yellow ---and Black---Stats

post #1 of 34
Thread Starter 

Well. It has taken me quite some time to get around to this post. December 17 2011 exactly 5 months to this date. Wow never noticed that one.


Taking for granted you know about the infamous Peter Belt. If not look him up. I won't go into that here.


I'm sure many of you will be interested in a rare piece of electrostatic and general headphone ( oops earspeaker ) history.

In this case it's 2 pieces. My camera ran out of batteries so I dowsed my old pics and it should be enough for you to figure out the basic underlying construction involved with these incredible items.

 I have a Phantom Power supply and mic test kit I just got in from BlueMonkeyFlyer for some orthos so as, or rather WHEN,  I get that set up I can do a measurement compared to my Stax SR-5, S-001 MK2, NOS AT-705's and a few other planar types, orthos included.

 May take a while so figured get this out there first and see if there may be an interest at all in that aspect.

 I currently also have 2 of the next generation PWB earspeakers (as it says on the box) other than these two, which are black as opposed to the yellow here.( anyone selling some white ones???). Honestly I do not know what generation these yellow ones might be, perhaps the first (?). I will have to check on the construction of the known white versions of the stats he made. I do know however there are many versions of the adapter /transformer boxes.

[Thinking these are the first generation units due to all others seen using the newer wide double-row padding headbands ]

  Earlier in the Orthodynamic Roundup thread I posted a pricelist scan that came with a pair of the black models here which shows various options on that.


Any of the listed ones with the double-row padded headband on the  Wikiphonia site are obviously way more refined than these so I would hazard a guess as these being the protoype/first versions?


   So for some reason I made a random search on fleabay.de one day out of the blue, and found these ones shown in this post. They happened to be owned by some audiophile feller in Switzerland who apparently was cleaning out his "cottage" and found these again.  Yeah. EXACTLY...you should have seen his other stuff he had auctioned, that and these came in an extremely weak cardboard box from some ridiculous audio amp/component /speaker company that is out of the reach of most sane folks.  So basically it looks like they were a one owner, and well taken care of over their lives. I can find no scuffs in any upholstery, looks like the stock pads without major blemishes ( simply some collapsed foam ), and no nicks in any cabling. Adapter box is in similar shape more or less.

For some reason the planar dimensional beings that oversee the audio frequency realms were smiling upon me that day:


Nobody else bid.


Here is a basic translation of the auction description using ImTranslator:



"War vor ca. 40 jahren der beste kopfhorer uberhaupt
Wenig gebraucht, guter zustand
Habe diese 2 kopfhorer beim aufraumen in meinem lager entdeckt und sofort angeschlossen gepruft und fur gut befunden.
Preis war fruher fur 2 PWB Kopfhorer inkl. anchluss - und umschalt-gerat ca. CHF 600.- im detailhandel
Es handelt sich um einen sehr musikalischen und raren artikel
Fur sammler, die gelegenheit
Viel vernugen beim bieten"



"About 40 years ago was the best headphones at all little used, good condition I have these 2 headphones when cleaning up in my camp and immediately discovered connected tested and found to be good. Price was formerly for 2 PWB headphones including data port - and shift-device approximately CHF 600.- in the retail trade it is a very musical and rare article for collectors, the opportunity to offer much just fun."


I don't know what inflation /USD to CHF was way back then, but 600 CHF (Swiss francs) in the early 70's (?edit if they ARE based on the SR-1 it puts them further back in time even) not cheap. Just doing a present day conversion puts that at $638 USD In 1960's/ early 70's USD! And that's ~40 years ago so add some inflation to that one!. Yikes.



          The arrival that scared the absolute #!@# out of me. This was inside a plastic Canada Post bag with a large sticker on the front with an apology for the shipment being damaged in transit before it got to Canada.

 Well what to do. It was a scary moment.                                          

  Then the inspection after a little hesitation. Nice box hey. Maybe I am spoiled from real Canadian cardboard.



A quick look to see what was smashed and luckily nothing. Was there some slight dampness to the box? I think there was.



The pads seemed slightly oversized around the perimeter that folds into the typical groove behind the baffle. They did have the oblongish earside opening typical of the later Stax Sr-5 I have so I assume these were stock pads. Below you can see the aluminum sheathed Stax-type 6 pin plug. Funny these are single entry and on the right side, English drivers do drive on the wrong side I guess wink_face.gif



The very interesting guts and associated damping. Foams perfectly intact no decay. The driver is housed in a black rubbery-plastic enclosing surround. There is some black dense felt type material held tight to the rear, or at least inside the top opening there. Next is  a greenish foam disc, and on the outer part at the rear vents there is a disc of some black fibreglassy/hairy/longstrand fibre stuff. As best as I can tell the rear vents are unique to PWB and are the same thing seen in the white, black, and Dyna-x orthos.

It appears on close inspection that these are custom molded backs that were somehow cleanly glued/bonded almost imperceptibly into place into what appears a basic Stax housing ( slight colour differential between the two ).  Dig the padding on the metal headband which is actually extremely comfortable!




Shots of the adapter unit first two from the auction pics.







Very clean and perfectly functional. From what I can gather Peter W. Belt did not like the Stax adapter box designs, preferring to use his own for these boxes, for sure from what he saw as a safety standpoint with proximity of parts to housings and no doubt also from a possible TWEAKS view. ( Rainbow Foil sample yet to be applied to this, also the Creme Electret ).

  I contacted Peter's wife May Belt directly a while ago about their headphones and any associated info/history, hoping she had a secret stash of things laying about somewhere she'd part with, but only got a very basic reply and nothing I couldn't find myself already on the net. Too bad. Doesn't anyone keep quadruples of their own products for the future ???



I have to say that these are far better overall than the SR-5's and  NOS AT-705's ( decent bass on those 705's for sure ).

The overall tone of the things, as well as the elevated bass levels compared to the SR-5 is simply amazing. I would love to eventually get an SR-3 or SR-5NB/Gold to compare with. Sooner or later that will happen. In my mind I would expect this to compete with or best the Gold.

 I find myself forgetting what I have on at times when listening for any length of time. Is it a higher tuned ortho? a dynamic? hmm nope the details, speed and soundstage are too grand.

This has happened more often than I can remember.




As there are two pairs I should probably keep them on rotation ( both work perfectly ) to keep them functional. At least plugged in together at the same time. these don't take much time to get up to speed if used occasionally. Maybe under 30 seconds. Currently I swapped a set of pads from the black PWB stats for these. I should really get around to stitching up some low profile leather ones to keep the original pads original.


I can post up pics of the Black E.S.2 models and interiors later and their basic model adapter frown.gif, for now I would like to flesh out further insights and information this batch if anyone wants to bother contributing. For example :what's the deal with that black driver housing? I see that there's most likely damping on the earside in there too, but no idea how much, how far in the driver is recessed or what's in that. It is bonded to the baffle rear. Anyone seen something similar?


Oh yes here's the glamour shot.



Comments most welcome and don't expect me to be too accurate in sonic descriptions . Graphs will show a better objective display of the sound. As I get to it, after modding more orthos, after other things.L3000.gif



One other thing. On that price-list scan  linked above they also had Dynamics = " Moving Coil" models of which I have only ever seen one picture in a movie prop site ( what a shame ) and specifically notated with "  NOT FOR SALE ".  This is also in the same housing and black.

Edited by nick n - 5/28/13 at 3:25pm
post #2 of 34

Cute! and yellowy!

post #3 of 34
Thread Starter 

While I was checking out the guts of the later black PWB models' adapter I figured I'd take some shots. This is the base , as in lowest, adapter available for the second generation stats ( or 3rd however it falls ) . Also seen listed on the link in the first post for the pricelist as "  Natural Sound P.1 Connector Unit " for the E.S.2. ear speakers as the box I have calls them as seen below.

Scale is not shown but you can judge by the silver jack on the front there, roughly. Ignore the temporary wire splices this is now fixed. And I guess I will go take a shot of the headphones as well.

A bit of technical info it seems that for safety reasons ( or other ) Peter Belt went with an electret driver for these later model E.S.2.'s. It states such in the pricelist if you read closely. No idea what happened with the E.S.1.'s which I will have to go ahead and assume is the white ones kicking about from time to time and as seen on the wiki, due to the exact same headbands, unless he changed production halfways through for supply reasons and the colour was different.


You can see above that the transformers are embedded in place in a layer of parrafin wax that is poured into the bottom of the housing.  This didn't fare so well on it's trip here from England so I opened them up and flipped the rubber feet over and it now rests as is. For some reason ( backwards again ) this top view was the bottom (?) so they hung in place, not the best way. I  have a feeling maybe someone simply put the feet over top of the screws to make it look better at one point.  May have to do a driver swap soon as opposite sides on each have a slight imbalance.

Nothing too terribly exciting but here's the only markings on the box. There you have it so far.



I am still looking for the white versions or actually ANY of these, including adapters, as I seem to be one of the few with any interest in them. So if you have some you wish to flog at any point fire me a PM see what we can do. I feel they should be preserved as much as possible and hopefully the last adapter box I saw for sale a while ago didn't get scalped for parts.frown.gif

Edited by nick n - 6/20/12 at 7:56pm
post #4 of 34

Just saw this and thanks for posting.  The PWB's have been a bit of a mystery but the ties with Stax were always obvious.  Looks like a SR-1 shell (they did come in that color) with a variation of the SR-1 driver (could be a SR-2 driver too) and the transformer boxes use all the same parts as the old Stax units.  I'd be very interested to see the inside of the black units too. 

post #5 of 34

Cool - nice lookin' phones, would love to A-B them with my SR-5NB/Gold

post #6 of 34
Thread Starter 

I may have an SR-3 - not "new"-coming ( I passed on the old SR-1 due to unknown voltage and version ) but interesting about the enclosures the drivers are in.   I have to go and swap over drivers on the lower output sides of each BLACK set to make one perfect and the other more or less a bit more faint and needing more juice, so at that point I will take some detailed shots.


Plan is to acquire an SR-5 Gold sometime too,  ( eventually ) so at that point can do a graph with the kit I got from BMF also, assuming I can get the REW software rolling on Ubuntu fine.  Otherwisie unless there's a baseline someone's familiar with there's no point.


Appreciate the insight on them as there's little to no info otherwise, even from the "belts" themselves. Shame really.


So the dating on at least the first version(?) yellow coloured ones would be what roughly, mid to late 60's?  That would give enough time between the 3 (?) variations on them as the black ones were mid 70's if I recall off the pricelist I scanned.

Edited by nick n - 6/12/12 at 4:22pm
post #7 of 34

Spritzer will know, but I believe the SR-3 hit in '68. Stax USA was set up around 1975. Don't know what the situation was in the UK-- PWB might still have been their importer.


Trivia: according to the 1971 Stereophile test comparing the SR-3 to the ESP.9 (!), ESS, the Heil-type speaker company, was importing Stax-stuff.

post #8 of 34
Thread Starter 

OK so some shots of the interiors.

No damping in place when viewed from the earside, I can see the protective membrane and stator surface, and the big red "special red pen " dot on the middle.

As you recall I believe PWB went electret for these later models, sure looks like it  Especially compared to my SR-50 driver seen there below also. 

They must have had STAX chuck in the yellow fibreglassy damping material at the factory: it's underneath the struts there and a one-piece disc, which is why they sound so godly. It's the yellow stuff that has the mesh backing as you can see there. Not sure what's going on in the middle of the damping there. It is a donut with that random bit covering the hole, perhaps the white shrinkwrap is meant to go behind that?

I wonder if they were able to do the driver damping like that themselves though not sure about clearances under those struts. Sure hope so because that means I could do retrofit with this method !


But how to find out which version, 30/40/60 drivers ? I guess timeframes of introduction from Stax would do it. Looking at 1978 for this model I'll go check the WIKI.  Guessing the SR-40 for the 70's.


Only other stuff behind the rear yellow discs there is some thin black material to act as dustguard or hide the yellow when looking from the outside.


Drivers are secured to the baffle front with a small bead of clear adhesive.


My Stax SR-50 Driver ( I believe the same as the 40? )                         PWB Black



now to swap drivers from each pair.



While swapping sides out I saw the exact same scheme in both, the outer disc on this one is a solid disc, so most likely in the first one I took pics of, it was whatever scraps were around.  Big deal yeah I know but just saying.

Tried to shift around the direct damping under the struts and it's a no go. Must have been factory. If I go with replacement SR-40 drivers I'll slice that stuff out and make sure it goes into the new ones.

Looks like this is what I'll have to do, what's there is excellent, but it's what's not there that's bothering me. A bit too much imbalance in the better pair.





If only the ESS headphones were more readily available, they did have some if my memory is being supplied with enough power to drive it effectively, these days I wonder though.rolleyes.gif Didn't they?

Edited by nick n - 6/20/12 at 7:58pm
post #9 of 34

Do you mean the ESS Mark 1 Heil-driver (aka AMT) headphones?

post #10 of 34
Thread Starter 

yes thanks for the reminder

post #11 of 34

Both the SR-2 and SR-3 hit in '68 but nobody knows why the SR-2 was so short lived.  I have a review of it here in an old Hifi-News and that's pretty much the only proof we have of it ever existing.  Well that and the couple of units I was stupid enough not to buy... frown.gif


On the issue of SR-1's, there were many versions but anything with the "woven" metal covers on the outside should be a 200V bias version.  My set appears to be very rare as it has etched metal plates on the outside of the housings. 

post #12 of 34
Thread Starter 

Could it be possible that PWB did not source their electrets from STAX, but from Audio Technica? I just noticed khbaur's post again ( http://www.head-fi.org/t/111193/orthodynamic-roundup/19755#post_8339475 ) with his shot of the rare AT-707. And look what's in the back there. Same damping.

I have yet to open up the AT-705's I have ( it's bad luck to open up these NOS ones ) but certainly the deep signature would fit what I can hear decently in one side of the black ones.


Are there any existing Stax electrets that have this direct damping under the crossmembers that anyone knows about?

Wasn't there some sort of unsure thing about where Stax actually sourced their electrets from? Seem to recall something of that nature. So even if PWB got them through Stax the OEM could still be AT.


Want to pinpoint some replacements , think i will maybe look into some AT's

Edited by nick n - 6/18/12 at 7:09am
post #13 of 34

I'm pretty sure A-T made electret elements for everybody back in the day.  I once heard that Stax had a hand in the design (same as with the Micro Seiki sets) but the drivers were manufactured by A-T. 

post #14 of 34

It could even be that Stax and A-T swapped expertise a few times. The old 700 series 'phones look Staxian. And most likely A-T, who had early expertise in electrets (along with Sony), supplied their own diaphragms. Stax might have drawn up a blueprint for the driver itself. And who knows who did the actual manufacturing. We may never know. Then A-T did a changeup for the 1978 model line. Who helped 'em with those?


Electrets were a new thing back then. The first mass industrial application, oddly enough, was for drop-in replacements of carbon-button transmitters in telephones, and the wild-eyed radicals doing this were guys in the laboratories of Northern Electric (now Nortel), Bell Canada's manufacturing arm, back in the mid-1960s. NE sent me enough material so I could do a paper for my high school physics class in 1968. Here's a US magazine article from 1969 that takes a lot of its info from that NE material. This doc tosses in an article from 1971 showing how to make your own electret.



post #15 of 34

I doubt anybody writing an article today would encourage people to mess with the anode cable on a CRT...  biggrin.gif  Sony were certainly doing their own thing with the electrets but most of the other sets are cut from the same cloth. 

New Posts  All Forums:Forum Nav:
  Return Home
  Back to Forum: High-end Audio Forum
Head-Fi.org › Forums › Summit-Fi (High-End Audio) › High-end Audio Forum › PWB ( Peter W. Belt ) Yellow ---and Black---Stats