Orthodynamic Roundup - Page 73

He's getting the original wualta tweaked Donuts. I'm almost done building my new MKII's.

Assuming nothing unusual happens in transit, of course.

HT-355/SFI ortho update:

* recabled to 26ga teflon copper, tri-braid (1 signal, two for gnd, per channel),5' length. Highs and mids about the same as before, but now I got excessive bass, actually too boomy for vocal (kind of like using 990 for classical). Still a little too much bass after I switch to Sony fabric pads. Housing stuffing is still the high density foam as before. The cable I used before was 26ga twisted pair cotton copper, 3', that was the only "tester" cable I got left at that time so I used it. All the wires were solid core, bought from HGA.
I know some of you will jump up and say cables don't make that much a difference, yes they do. I know because I heard the difference. The bass difference is undeniable. There is no way you can get that strong a placebo effect.
The deepth didn't improve, just more in quantity. It is not the "990 kind of deep bass", but still nice for rocks. If I can get the bass to go down a little more I will be really happy, still want to use it for vocal anyway

One thing worth pointing out though: recable might not get more bass than your factory cable. Factory cables are stranded so are usually more bassy, but the sound is not as clean.

HT-355/SFI ortho update: part 2:
Mod to tame excessive brightness (this was when I still had the cotton copper on them; with tri-braid teflon they are no longer too bright for me):

Add a small super strong neodymium magnet to the center of the driver front magnet, this will knock down the treble (alot) and make the mids stand out. Have a little effect on bass but not too obvious. The neodymium will stick to the center (and only the center) by itself, so no way to go wrong.

If you try to flip the neodymium arond and hold it down at the center of the driver magnet (they natually want to repel), the treble will be boosted. Have no idea how it will affect the bass since I couldn't get a good seal, the finger that was holding down the neodymium was in the way.

The HT355 eyes are staring at you

I am actually not too sure now. I suppose we can get super thump that way, but we might not be able to improve the deepth. With the tri-braid teflon there is already enough thump, but not as much deepth as I want. Any way to extend the bottom end? Do I have to be the guinea pig to peel off the back vent felt and see?

Yes or no. The SFI square midranges were my first.... er.....I don't even know if the squares will count as ortho or not. So maybe no. But the squares didn't work, I was Hopeing to make a pair of SFI-1000, float style







The strange thing with this HT-355/SFI is the felt or thick foam disc (againsting the back of driver) hasn't given me any special results, my tuning end up using the same method like how I tune dynamic drives in a small closed housing (have done KSC55 drives into CD180 and Koss TD-60, both end up using high density foam as stuffing, mainly to kill echo without losing too much bass. That was why I jumped to high density foam right away)...... Maybe I missed something, but nevertheless I like the result as now.


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TD60/SFI project:
1) Pull out the TD60 baffle. The baffle is connected to the housing via two ball/socket features, they pop right out when you apply force.





2) Remove the original driver from the the driver socket.




3) Cut off the protective plastic grid with a pair of sharp diagno pliers, so nothing will block in front of the SFI driver you are installing (except the grey sponge of course).




4) Install the SFI tweeter, using blue-tac to hold it in place and seal any gap between tweeter and baffle.




5) solder cable connection, then reinstall the original black foam pad.



6) Install damping/stuffing material in the housing cavity.
Then pop the baffle back into the housing. The project is now complete.




The sound, comparing to the HT355 (when with twisted copper teflon): mids about the same; not as bright, probably due to there is now a layer of 1/8" grey foam in front of the driver; Slightly less bass, which supprised me, I was hoping the smaller TD60 superaural pads can give more bass. Didn't improve when I pressed the phones against my head so my ears get closer to the drivers. So the ear/driver distance is not the cause of less bass here. There is probably some damping trick that I still have to figure out. Anyway, the sound is pleasant, I will use these as my computer phones (though I wish my sound card was more powerful).

That was a fast mod. Did you try adding extra damping material behind the driver because the backwave could be bouncing off the plastic enclosure. Maybe I should buy a couple of these drivers and pop them into my td/61.

Edit: I retract my question, I should'e read the last post more carefully

I also find that if you overstuff you lose insulation some material insulate better uncompress or packed in

Yeah, Steve is passing on his much loved Donuts.

I can't wait to hear them, though I've been told I will need YH-100 drivers for them to be at their best. So if anyone has a pair that needs a new home, keep me in mind.

Well I got the cups for the Chocolate Donut MKIIs finished tonight. You can see the difference compared to the originals in one pic. I just need to pick up some screws tomorrow for the earpad flanges and baffles, then they're off to Fitz for cables.
You have to kind of look for it, but there's an 1/8" inlay of Cocobolo just before the cup flares out at the bottom. I wanted it subtle.

Alright, shoulda posted this sooner.

I have received, opened, and photographed an SS-100 driver.

These were certainly made by Fostex. The diaphragm has a T50 foil pattern, and the same phenolic resin frame as the T50. I bet if i really wanted i could transplant the diaphragms into a T50.

Enough of my yackin. Here's a picture:



The magnets are a single slotted ferroceramic like a T30, rather than the steel plates with sticks of samarium-cobalt found in the T50.

The construction is a lot more spartan than the T50, probably to make it fit into a smaller and slimmer earcup.

In the T50, the plastic frame completely encompases the driver parts just like on other Fostex 'phones. But not in the SS-100. On the SS-100 driver, you can see the sandwich that holds the diaphragm in place clearly with the driver fully assembled.

The diaphragm's frame is suspended on each side with a narrow ring of foam. What i find interesting is that the forward ring is a low density foam such as seals both sides of the diaphragm frame in a T50, but the backside ring is a dense foam that has thoroughly degraded over the last 20+ years.

It's also interesting that the damping disc on the back of the driver is inside a plastic ring. There's no such ring around the damping disc on the T50.

As wualta has pointed out, the film seems to be mylar rather than the kynar in the T50.

For the record I recommend that you never open these drivers up unless you have contstructed a jig that will keep the halves centered while you reassemble it.

The T50 driver where the frame of the driver completely surrounds the diaphragm frame and holds it in place. No such convenience on the SS-100. The halves deflect eachother to either side, and the diaphragm deflects half-way, making it a royal pain in the kiester to keep everything lined up long enough to get a screw into it.

If you were really careful, four finish nails could be driven into a board such as would sit in the corners of the crenillations of the driver housing. This could potentially help a lot.

But really. Don't go there. Just don't open them.

well... after a listening session with audiocats...

We decided that a yh-100 felt damping really isn't the way to go. Screw reflex dots and felt. Audiocats' secret high density foam works wonders. Audiocats even said he preferred the sound of the yh-100s with secret foam and no felt to his dt990 600ohm in terms of bass! Not bad for 35 dollars and some secret ingredients...

Steve, the new Choco-donuts looks fantastic. Can't wait to read about how the finished product is!