Information request C12 and Ela M251 headbasket

Checking to see if anyone can provide data on the C12 and Ela M251 headbasket mesh specs and well as dimensions.  I'm thinking about getting a retrofit headbasket manufactured to fit Alctron HT-11A and Apex 460 donor bodies.

That would be a cool product to offer.

I don't own either mic, but I believe the C12 has a fairly open single-layer headbasket, while the 251 has a larger, 3-layer headbasket. This is supposed to account for a lot of the difference in top-end response between the two mics. The C12 has two sideposts but I'm not sure about the 251.

Good picture of a C12 reproduction headbasket here:
http://www.tab-funkenwerk.com/id91.html

I believe that Jim at JJ Audio modifies the 460 headbasket to look like a C12. Not sure if he would be willing to share methodology or not:
http://jjaudiomic.com/Dutch.php

Interesting reading here:
http://repforums.prosoundweb.com/index.php?topic=30791.0

Edit: realized that wasn't really what you asked. I don't have specific information on mesh size or headbasket dimensions... maybe someone more knowledgable will chime in.

I don't have any info on the headbasket but I have made a C12 clone from the C24 schematic using an HST-11A as a donor so I would definitely be interested in picking up a new headbasket.

I would focus on the C12-style headbasket. It is more open (for a change) plus the 251 is thicker/wider than the HST-11A anyway.

I believe that Jim at JJ Audio modifies the 460 headbasket to look like a C12. Not sure if he would be willing to share methodology or not:

Click to expand...

He shared his method on several occasions on the Gearslutz forum. Can't find all the posts right now, but the bottom line is he uses the stock 460/HST-11A headbasket and modifies it. The bottom ring stays, a side bar is added and the single layer mesh is soldered to the frame. He then sends it to someone to have it chromed. (From the back of my head.)

Good picture of a C12 reproduction headbasket here:
http://www.tab-funkenwerk.com/id91.html

Click to expand...

After looking there, go here:
http://www.flea-microphones.com/parts.html
Go to mechanical kits & parts, click on C12 and then open the C12 gallery.
Image 2 is a great close-up of the headbasket.
Don't forget to view image 17, and following, and compare with the Tab-Funkenwerk pics.

Are the 460 and hst-11 the same mic, or do they have different dimensions? There's a video on YouTube of a moded 460, and the guy claims to have taken out two of the three layers of mesh from the head basket.

They're identical. Alcon are the manufacturer, Apex just brand it and sell it.

Hmmm. .  . no solid data appearing yet.  I have a lot of internet pictures only.  Well, I know the HT-11A is wider than the original C12 so I will not be able to get this thing exact.  My best bet is to look at the proportions and try to make something similar-ish while retaining the stock HT-11A headbasket base-piece while using a similar mesh.

From Tim Campbell's notes, it seems mesh with gaps larger than 1.5mm begin to compromise hum and noise rejection.  The stock Alctron GT-2B mesh material has ~1.47mm spacing and eyeballs at least closer.  The factory is requesting a dimensioned drawing, so here's where I'm at so far.

I'm not a solidworks pilot of any sort so a little sketchup will have to suffice.  hopefully it will give them the info they need to adapt the design.

FWIW, 797 Audio from Beijing once did a C12 "clone". Well, it had a K67 to begin with so never mind, and the headbasket wasn't so spot on either, but at least they did add the side bar:

http://recordinghacks.com/microphones/797-Audio/CR998

If you click on the picture to enlarge it, you'll notice that the bar is loose at places. Something to watch for.

FWIW, the headbasket is slightly curved at the top. It looks as though your sketch up flattens out in that region.
You should also be aware that a single mesh layer is gonna have less acoustical interaction with the capsule than a more standard three layer design. So, other than removing that "headband" that covers a little bit of an upgraded capsule (34mm) on the HST-11a, you may not notice much of a difference. I guess there is only one way to find out...  :

-James-

the headbasket is slightly curved at the top. It looks as though your sketch up flattens out in that region

Click to expand...

What/which headbasket is curved at the top?

a single mesh layer is gonna have less acoustical interaction with the capsule than a more standard three layer design

Click to expand...

Yep, that's the good news of the original design IMO, especially since it's such a narrow headbasket. 

From the pics I've found, the C12 headbasket has a bit of curve to the top. It could be a strange camera angle. Does someone who has owned/seen a C12 know for sure?

-James-

I seems to vary a bit. . . some seem to have more curved edges and "rounder" tops. . . some seem to be very square with a definitive flat top.  Flea's headbaskets are definitely flat on top.  Wide variation also seems to exist in U47 headbaskets.

Apparently, these are not all that common, or folks who have them do not routinely take the dial calipers to them and measure.  Information is scarce.

I'd definitely be interested in a custom Apex 460 heabasket to fit my already-built C12 clone. I never liked the fact the stock headbasket's headband is too low for the aftermarket 34mm capsules. It depends on price though...

-James-

messed up a little. . . had the base rotated 90 degrees the wrong way.  A couple of fixes.  Shap is a bit on the "rounder" side than some I've seen but I'm diggin' it.

There are two lengths of headbasket on the c12 also... my vintage c12 headbasket is shorter than for instance what flea make.

Im on tour right now but when i get back to LA I can take exact measurements for you.

tweaking more. . . actual measurements are helpful, but from FLEA and AKG photos, it seems I needed to make it taller and the curve radius smaller.

chunger said:

Apparently, these are not all that common, or folks who have them do not routinely take the dial calipers to them and measure.  Information is scarce.

Click to expand...

Not really, rent a studio for an hour that has a C12.

http://www.thehookstudios.com/

Or try rental companies in LA.

http://www.audiorents.com/

Mark

chunger said:

tweaking more. . . actual measurements are helpful, but from FLEA and AKG photos, it seems I needed to make it taller and the curve radius smaller.

Click to expand...

looking good so far mate..

Here is my c12 folder full of collections from the net and images of my own c12, i zipped it up for you and uploaded it.

hope this helps

www.JessJackson.com/sessions/C12.zip

Biasrocks said:

chunger said:

Apparently, these are not all that common, or folks who have them do not routinely take the dial calipers to them and measure.  Information is scarce.

Click to expand...

Not really, rent a studio for an hour that has a C12.

http://www.thehookstudios.com/

Or try rental companies in LA.

http://www.audiorents.com/

Mark

Click to expand...

or just link with me if your in LA.. i have one

Another forum member relayed to me some key C12 dimension data on another thread.  Thought I'd cross-post here in case someone was searching.

headbasket height including base ~66mm

mesh 12 per inch .025" wire diameter

Hoop width 5mm