Orthodynamic Roundup - Page 288

more SFIing

I think I have a pretty good fosterfone here.

I picked up some cheapo 70's/80's "sonic stereo" headphones off the bay with the express purpose of fitting the SFI's and I think we have 'near jackpot'

The SFI's are extreme damped - dunked in glue with thin felt then reflex dotted and finally Ludo's thick felt tacked down around the rim. The front damping was removed due to prior exuberance with the pliers and I used acoustic mesh glued around the rim and pulled taught to protect the drivers.

I cut the ear baffle to fit the drivers and temporarily bluetacked them in - I will get some epoxy putty now that I have such good results. The rear chamber was opened enough to just hold the edge of the Driver/Felt. The ear pads have the look of the Yamaha's pads - flat and soft, the SFI driver comes very close to the ear. My only gripe is that the headband is a little flimsy and doesn't clamp as well as I would like - the result is that the deeeeeep bass becomes deep bass. I put a layer of damping felt into the open chamber but it doesn't make any perceivable difference.

So far so good - next is to try and rig up the Beyer headband onto these cups and then they would ( I think ) be perfect.

A few pics .....







..dB

Unfortunately they are pretty nondescript. The Box gives little information about them other than they were made in Taiwan. I am assuming the company was Sonic and they are the 'S/40 STEREO HEADPHONE'.

Here is a picture of the box.



..dB

They look nice. Have you tried to bend the headband vigorously? By vigorously I mean bending it into a figure 8 or such. It worked well with one of my hybrids.

yes, I have tried bending them and last night I bent the wire that holds the actual cup to near 90 deg - it provides a much better seal now..dB

Just got a call at work about some important mambo-jambo and lost PMB100 auction. Oh well, there was no pictures anyway so I was hesitant to bid a lot.

OK, I've changed a few things on the OCTODYNAMICS (I used your name and changed it a bit, thanks Smeggy).



Here is a shot of the capsules disassembled...I decided after one assembly/disassembly that having individual tuning discs for each driver was a complete pita, so I made large discs!

I took Wualta's advice (thank you sir) on ensuring a good seal between the drivers and baffle, and also between earpads and baffle. I cringed at the thought of rolling out thin beads of blutak to use as gasket material between driver and baffle and decided to just a apply a thin layer of epoxy(I was frugal in application and I "think" I will be able to take it all apart if necessary).



The driver capsules assembled...





Um, the bass is back in force(which is kind of appropriate, since they look like spinners). I am continuing to burn them in and may dampen the drivers even further...

This looks awesome. Next step is to make a Float frame like thing with 6 drivers per side. If only I did not have 2 left thumbs.

those octodynamics look great; how do they sound?
i hope my sfi drivers will arrive soon, as my new float frame is standing here unused; begging me to play with it

i also just got hold of a pmb100 from germany (not the one on ebay it seems) so im looking forward to see how it compares to the pmb85 DA; i will also be able to use it as a reference when tinkering with the ortho float.

i was almost finished writing my "giant" float/sigma comparison when i had to pack them all down for storage because of moving, so i guess i´ll have to ad these two floats to that comparo as well (that makes it 5 floats and a sigma!)

Are so it was you who outbid me by half a Euro

Oh wait you are saying it's another one....scratch my comment.

Well I broke off a wire in my HP-50S whilst experimenting with damping. I had to use a Lot of damping, even more than Ludoo's bassy HP-3 and I wasnt even done yet.

The sound was starting to open up. I was using ludoo's thin dense felt, and also dress material similar-ish to silk (similar air resistance to Ludoo's dense felt) as my damping materials.
I have a soldering iron on order, I think these will sound v.good. And quite different to the HP-50.
I think Ludoo will concur, that the HP/YH-3, HP-50 all the variants, also can all vary in sound quite considerably, im thinking even two of the same model...

Thanks F2D(I can call you that, right?). I have some 1/4" polycarbonate sheet from a past project and I have been looking at instructions on how to heat form it. Luckily I can fit a strip long enough to make a Jecklin type frame(approximately 4"x20") diagonally in my oven. Of course I am out of drivers at the moment. Also, with four drivers per side we are definitely into the "ear speaker" category, going up to six might require some sort of neck crutch attachment.

bjarnetv,
Thanks, it is hard to be objective about your own babies....and I need to listen to them with more(and different) types of amplification...but right now I have to say pretty "f"n dynamic sounding As far as I can tell there is some type of cavity resonance happening in the upper mid frequencies that I might (if it continues) try to dampen with some type of random baffling or absorptive layers in the negative space between the ear and baffle. I think this might be caused by the totally symmetrical layout of the drivers.

The decca has a certain appeal, but I will resist any further temptation. I really do like the look of the octa and such a simple concept - well done.

I had a look too and couldn't find a single reference to them. I do however think they would be dead simple to duplicate out of wood, the back of the cup is purely cosmetic as the driver itself is seated on the front "disc" and merely supported by the rear piece - using a smeggy approach, this would be real simple. The earpad itself is also simply done and should be easy to sew up. The trick would be finding something cheap to hang them on ..dB

Yeah, one of the reasons I hadn't built these yet (I've had the drivers for awhile) is that I was thinking of a focused array arrangement of the drivers, with each of the four drivers on axis with the ear canal. Unfortunately this greatly complicates the construction.
The sandwich construction works well for ease of assembly/disassembly and tweaking. I think you could still keep it down to four drivers and keep one on axis with the ear canal if you did a propeller sort of layout with a driver in the center and three others placed every 120 degrees around it. The chassis would have to change to the bale type(an old DT770 frame would work). Or the Jecklin concept

Having said that (and keeping in mind that I can't hear above 15khz anyway) I don't really notice a shelving down of the high frequencies with my current layout.

If this version continues to impress I might try a truncated pyramid cup with a driver on each facet.