[joelpearce]

All right, looks like I'll be moving ahead on some SFI projects (orthos really are addictive).
 
A couple quick other questions (I have been searching and reading, though I'm finding it hard to get specifics).

• Are the 32ohm ones actually efficient enough to be driven from a portable player?  Is there any special reason to go with them over the 120s?  Has anyone tried both enough that could explain the sonic differences?
• Do they work in larger enclosures?  I have an old pair of Realistic Nova Pros that have the drivers removed, and I'm considering using them as foster phones, but it's an awfully big space in there.

 

[Rick]

I prefer the 120ohms, some say they can't hear a difference, but I find the more power going into them makes them really "sing". A matter of preference.
 
hmm....Depends if you're going open cups or closed. Closed cups I wouldn't recommend large spaces. 

 

[dBel84]

I have to say, I am in the camp of those who don't really see much difference. I have 8 ohm, 32 ohm and 120 ohm SFIs and every one of them needs more power than a portable device can deliver. That said, I have enjoyed listening to them very much out of a portable device, just aware that they are not nearly where they could be in performance..dB

 

[joelpearce]

Thanks, guys.  It's just a lot cheaper to get a larger number of 120ohm ones, which would give me a lot more experimentation materials.
 
With the Novas, I'm thinking of trying a vented design a la Thunderpants.  There are already vents in the cup, and places where it was easy to drill smalls holes in the baffles as well.  The cup and baffle are both made of awesomely thick plastic, so there will be plenty of room inside to place in better sonic materials.  Not that much to lose with them, really.

 

[DefectiveAudioComponent]

Fellow orthoheads!
New pictures of a russian orhto, the portable N-21S,  is now on the wikiphonia
(pictures aren't in the main article yet, but some of you might want to have a look at once I thought....)
 
N21-S

 

[ujamerstand]

Cool, this unit is made in 1992 huh? Looking at the orange foam makes me think these won't have a lot of bass...

 

[Armaegis]

I can't figure it out... what is the SFI acronym?

 

[Rick]

Sawa Fuji Industries.  They make refridgerators now

 
Quote:

I can't figure it out... what is the SFI acronym?

 

[joelpearce]

Okay, I just redamped one of my pairs of PMB-80, and WOW.
 
Blocking the area around the driver in the baffle makes a truly massive difference.  They are now almost completely open, with just a thin layer of poly batting in place behind the driver to prevent dust from going into the driver.  I have 1" foam pushed in surrounding the driver, and a piece of rubber foam pushed into the baffle, sealing off the driver.
 
Suddenly, these things sound truly phenomenal, not just better, as they did with my original scheme.  They don't have a really wide soundstage, but it's wider than any other ortho I've used.  The bass is nice, but not the "pushed" bass that I've heard from other orthos.  The upper range and midrange is truly incredible.  At least as good as the T40v1.  I still find it hard to believe that the designers of ortho headphones haven't played around to develop the best possible sound.  Seriously, one small piece of foam turns it from flimsy and anemic to rich and full.
 
It even sounds good with electronic music.
 
I'll make sure I get a shot of the insides soon, for anyone who is messing with a similarly open pair and wants to ramp up the bass a bit (I realize that most of you have figured out the whole "seal the baffle" thing a long time ago, but I've mostly seen it in association with sealed cans.

 

[wualta]

Sounds like what you've done is seal the back of the driver to the cup, just as we normally seal the driver to the baffle. Is that what the foam's doing, or am I off target?

 

[wualta]

Quote:

Fellow orthoheads!
New pictures of a russian orhto, the portable N-21S,  is now on the wikiphonia

Them's really cool. I like the simplified construction, too: they used two ring magnets and two button magnets and the part we see with the holes in it is just a pole piece made of sheet iron or steel. Do we have a description of the sound?
 

 

[Sambones]

I was thinking of doing the same thing. All I need now is a material to use to glue the magnets onto, to maintain a level plane....hey, no duh, I could just use twice the magnets and crisscross them....
 
I wouldn't at all worry about the magnet's strength. The seller isn't so much an idiot, as just poorly informed. Yes, strong magnetic fields can interfere with electronics, but you're talking much stronger magnetics than that.
 
To quote Emporer Palpatine, "DooOOO iiiiiiiit!"
 
Btw, that pic is showing a ring magnet. I think the easiest thing to use would be bar magnets. Also, for your reference, the SFI's are 4cm (40mm, 1.57 inches) long, meaning that you need to get a longer bar magnet than you're looking at.
Quote:

noob question..if i strengthen the magnet of my ortho driver, will it improve the overall sound quality?
 
i'm thinking to done that with this neodymium magnet:

general specs:
1cm x .5cm x .5cm (LxWxH) nickel plated (silver looking) bar shaped magnets.
Rated at 12000 gauss *2 pcs of the magnets can lift up a 1.25 kg weight.

 

[joelpearce]

Okay, strange question ahead.
 
The two pairs of PMB-80s both have a driver that only works if the volume is turned quite high.  Now here's the odd thing.  Neither pair will work consistently with my tube amp.  Sometimes, the sound will drop out, and sometimes, I can't get them to come to life at all.
 
With my solid state amp, I can't seem to get them to NOT work.  Even at relatively low volumes, both pairs work just fine.
 
What's up with that?

 

[ericj]

Quote:

I was thinking of doing the same thing. All I need now is a material to use to glue the magnets onto, to maintain a level plane....hey, no duh, I could just use twice the magnets and crisscross them....
 
I wouldn't at all worry about the magnet's strength. The seller isn't so much an idiot, as just poorly informed. Yes, strong magnetic fields can interfere with electronics, but you're talking much stronger magnetics than that.
 
To quote Emporer Palpatine, "DooOOO iiiiiiiit!"
 
Btw, that pic is showing a ring magnet. I think the easiest thing to use would be bar magnets. Also, for your reference, the SFI's are 4cm (40mm, 1.57 inches) long, meaning that you need to get a longer bar magnet than you're looking at.

 The idea that i had back in the day was to go to the hardware store and get four steel drain or vent grates and pave them with cheap and small neodymium magnets - little cubes or sticks or whatever - and then apply a layer of shellack or something to keep them from moving around.

 

[wualta]

JP: Just a hunch: measure the DC offset, if any, of the two amps.
 
Keep in mind as you envision DIY drivers that the magnet's shape should mirror and parallel as much as possible the traces on the diaphragm. We see this in the serpentine-trace Fostex drivers particularly. I believe ericj's experience reassembling a T50v1 type driver showed this practice to be more than just tradition. In fact, his idea of using a floor drain grate (in steel, not brass) as the holder/pole-piece for some NdFeB magnets would give us something very like the early version of the LCD-2.