[wualta]

Russian headphones at flea markets-- I can only sigh with envy. I'm lucky to find a modern toaster. And yes, when they haven't had something horrible done to them, the funny PMB-copy drivers actually have bass and a wonderfully smooth and rounded sound. I look forward to hearing someone describe the results of a damping job.
 
Germania's links to supposed SFI driver sellers in Europe currently lead to tweeters, not the bipole/dipoles we seek, but keep looking there and online here in the US. Somewhere there's some SFI bipole/dipoles left. It's too bad we had easy access to them for so short a time. 
 
 

 

[Tyll Hertsens]

Quote:

 Not too shabby if I must say so and a great bonding experience for us.
 
 
 
 

now that deal is hard to beat !! 
 
..dB
 

Suhweet!! Nice job, dad. 
 

 

[Keller1]

Quote:

Russian headphones at flea markets-- I can only sigh with envy. I'm lucky to find a modern toaster. And yes, when they haven't had something horrible done to them, the funny PMB-copy drivers actually have bass and a wonderfully smooth and rounded sound. I look forward to hearing someone describe the results of a damping job.
 
Germania's links to supposed SFI driver sellers in Europe currently lead to tweeters, not the bipole/dipoles we seek, but keep looking there and online here in the US. Somewhere there's some SFI bipole/dipoles left. It's too bad we had easy access to them for so short a time. 
 
 

I totally messed up my last pair, If i find more orthos in poor condition I'll try modding them , and even mabye recasing them with wood.
Currently, however, I can say it's a very good headphone, It plays along whatever music you throw at it. metal, rock and Electronica all sounded great. With a slight distortion in guitars. ( Too sharp ) 
But then again, i'm driving it off onboard audio without an amp/dac.
By the way, happen to know any other vintage piece of tech that I might find at a fleamarket?

 

[bluemonkeyflyer]

Quote:

I covered all the baffle slots around the ear side of my fake AT-ESW9 foster phones with electrical tape. Placed 1 inch squares of yellow fiberglass in the cups about 1/16" thick. I drilled one 3/16" bass port hole in the side of each cup 1/2" from the cable entry and inserted a brass servo eyelet in each. Made sure this bass port was not obstructed by the fiberglass. Then secured the 32 ohm SFI tweeters, that fit perfectly, with a bead of hot glue. I cut donut felt rings and placed one over the ear side of each baffle to cover the outer ring of holes and secured them in place with double sided tape. Finally, replaced the ear pads.

The result? Remarkable improvement across the frequency range but too much bass. EQ'd the bass down and they sound surprisingly good. Tomorrow I plan to remove one piece of tape from an an ear side baffle hole to open a vent between the cup housing and the ear side of the baffle. I think this will attenuate the bass. I may find that I have to open more than one per baffle.

For 32 ohm tweeters, I had to turn my Dacmini volume knob to 2 o'clock for 80-85 dB compared to 11 o'clock for my 50 Ohm LCD2's.

I'll take pix and post them tomorrow.

Thanks to rhythmdevils for the helpful tips.

 
I discovered a 9 dB hump around 250 Hz.  I can EQ it and it sounds really good with all other frequencies set to flat.  I tried the following to tune out the hump:
 
1.  Opened a small vent on the ear side of the baffle:  No change
2.  Replaced fiberglass with 1 layer of Paxmate:  Sounded like a cheap transistor radio.
3.  Removed Paxmate and left inside of cups naked. Back to good baseline flat EQ but no change to 250 Hz hump.
4.  Mass loaded the rear side of the baffles with plasticine:  No change to 250 Hz hump.
5. Closed off the 3/16" bass ports:  No change.
 
I'll post pix later if some modding genius has a tip to tune out that stinkin' 250 Hz hump I can try.
 
I'm at a loss for what else I can try so..... I'm gonna switch gears and start on that brand new pair of Rastapants.
 
 

 

[gurubhai]

Finally got around to take some pics of Peerless PMB-80 :
 




 
After some tweaking they are sounding pretty balanced to these ears plus they have a better soundstage than most vintage orthos.
One remaining issue is that they seem to be a bit 'grainy' compared to my other orthos.
I haven't tried any other PMB orthos so can't be certain if its a family trait.

 

[bluemonkeyflyer]

^ Those look great!  I would love to hear a set.  What tweaking did you do and how to they compare to other orthos you've heard?

 

[Dom de B]

If I intend to make my own Planar Magnetic headphones. What drivers are recommeneded/can be used? For example i saw that people used SFI tweeters when they were available. However i dont understand how a tweeter can be used to cover the full spectrum accurately? Maybe i'm missing something? If people used those tweeters could i use other tweeters?
 
Pretty much, I'm after Planar drivers as they offer better bass. Both in volume and quality. Atleast that is waht i can tell from reviews of planar headphones. However i dont understand how a tweeter rated at 5K - 20K can supply bass which isn't out done by the ecommeneded frequency range?
 
Thanks in advance, and sorry if it was poorly worded i will come back in a second and re-read it.
 

 

[gurubhai]

 
Quote:

^ Those look great!  I would love to hear a set.  What tweaking did you do and how to they compare to other orthos you've heard?

 
 
I haven't done much yet. The previous owner had sealed the baffle to the driver using some rubber foam & that's basically most of the job done.
I just redid damping behind the driver to my satisfaction & that's about it.
 
And I have already offered my comparison in the previous post, perhaps you missed it.

 

[rhythmdevils]

Quote:

I discovered a 9 dB hump around 250 Hz. 
 
I'm at a loss for what else I can try so.....
 

Have you tried wool felt?  Even the bass heavy RP18 can be tuned to be fairly basslite with enough dense felt.  But the felt does affect other frequencies as well, so it's kind of a balancing act.  But if you're only using fiberglass now, you might want to try felt against the driver or in the back of the cups.  You could also try another bass port which you could plug up if it sounds bad, but have around for tuning options. You could also open more vents venting backwave into the ear chamber...
 
Where did you get the fiberglass and paxmate?  If you're in the states, I'd be interested in trading you for some nice wool felt.  I've never tried either of those. 

 

[wualta]

 
Quote:

Have you tried wool felt?  Even the bass heavy RP18 can be tuned to be fairly basslite with enough dense felt.  But the felt does affect other frequencies as well, so it's kind of a balancing act.  But if you're only using fiberglass now, you might want to try felt against the driver...

I'm with RD on this. I didn't see where there was any damping applied to the back of the driver, but I figured I missed something. You might also try removing that "bass lens" felt donut from the ear side of the SFI.
 

 

[wualta]

 
Quote:

...i saw that people used SFI tweeters when they were available. However i dont understand how a tweeter can be used to cover the full spectrum accurately? Maybe i'm missing something? If people used those tweeters could i use other tweeters?
 
Pretty much, I'm after Planar drivers as they offer better bass. Both in volume and quality. Atleast that is waht i can tell from reviews of planar headphones. However i dont understand how a tweeter rated at 5K - 20K can supply bass which isn't out done by the ecommeneded frequency range?

 
Not poorly-worded at all. Are you missing something? just one little bit: the tweeters we were using aren't ordinary tweeters but dipole tweeters that were used in Sawafuji's big quasi-planar speaker systems. They're rated to reproduce only the top two octaves because in a speaker application they wouldn't put out any audible bass, or even much in the way of midrange. They're way too small for that, so they're classed as tweeters. As would a driver from a Sennheiser HD 800 uberkopfhorer also be, if you pulled it out of the headphone and stuck it out in free space or on a speaker's baffle board. Take the bassiest headphone you can find, crank it up to earbleed levels, then take it off your head and hold it up and ask people in the room if they hear any bass at all.
 
But if, instead of trying to make it drive a whole room, you give an SFI dipole just a little slug of air in an earcup, it can get enough of a grip on the air to produce bass. As long as you keep the backwave well away from the frontwave, of course.
 
The reason? Luck. We're just lucky that the fundamental resonance of the SFI dipole (aka "bipole") tweeter is low enough, which means the tension on the diaphragm is low enough, to give the excursion and the low frequency cutoff that we need for a planar headphone driver. Most--nearly all-- conventional tweeters, including SFI's nondipole ones, don't have the excursion and/or the low tuning and won't produce bass even in a headphone enclosure.
 
Does that help?
 
 

 

[dBel84]

OH WUALTA , i do like it when you talk dirty 

 ..dB

 

[bluemonkeyflyer]

Quote:

 

I'm with RD on this. I didn't see where there was any damping applied to the back of the driver, but I figured I missed something. You might also try removing that "bass lens" felt donut from the ear side of the SFI.
 

Thanks for the advice, wualta and rhythmdevils. I don't know which side of the SFI's is ear side and which is the rear side.  I'll try thin felt on the back of the SFI's.  
 
I made a guess that the grill cloth that looks "finished" or fine and uniform is the ear side and the grill cloth that looks coarse is the rear side. Is there some way to determine which is which?
 

 

[wualta]

 
Quote:

I don't know which side of the SFI's is ear side and which is the rear side.
 
I made a guess that the grill cloth that looks "finished" or fine and uniform is the ear side and the grill cloth that looks coarse is the rear side. 
 

Eh? we thought you had the SFI installed in the headphone already with a donut of felt on the ear side.
 
As for which side should be facing the ear, I'm guessing you're correct in your guess.
 
 

 

[wualta]

Quote:

OH WUALTA , i do like it when you talk dirty 

 ..dB

I knew you'd like "uberkopfhorer" ! You'd probably like it even better if I put the umlauts back in..