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Home-Made IEMs
Feb 24, 2015 at 10:28 AM Post #3,288 of 15,996
I poured the acrylic mix in the mold and put it in a pressure pot with hot water and filled it to 2,5 bars pressure, then let it stay for about 45 min. They came out a bit more rough on the surface than expected but the fit is still good. Now it's time for some trimming and polishing and to drill out the shell.
 

 
 
Quote:
cmos1138 said:
   
I have used dental acrylic successfully to make shells a few times. for me, it was a powder acrylic with liquid monomer. I was able to make the shell body hollow but still had to drill out the canal section. If you can find a way to make the body hollow it will save you the trouble of having to drill that section out and it will be more visually appealing.
Click to expand...

How did you manage to make it hollow from the start?
 
Feb 24, 2015 at 1:13 PM Post #3,289 of 15,996
I just completed another universal - was pretty interesting to make. I used a GR31587 which I've never seen before. Luckily it seems to sound pretty good. 
 
Drivers used: HODVTEC31618, BK26824, GR31587, SWFK31736
 
I used a 1mm teflon tube each for the GR and SWFK, and merged into a 2.5mm diameter stainless steel tube. A 1mm teflon tube was used for the BK. I also used a 10cm long 0.5mm silicon tube for low pass filter on the HODVTEC, which resulted at a cutoff at around 100-200Hz. There was actually too much bass from the HODVTEC, so I added a resistor on it, which I just attached to the shell as a pot to turn the bass. The Estron wires were really really convenient to use - I do recommend them as the connecting wires for drivers.
 
Thinking back, I might use a Sonion 3300 and 3800 instead of the BK and HODVTEC next time to change the sound a little. The mids are a little dry currently. I also need to improve the passive crossovers for the GR and SWFK.
 
 

 
 
Feb 24, 2015 at 1:24 PM Post #3,291 of 15,996
Yup, I don't like making shells, too annoying - getting them online is faster and their quality is really good too.
 
Feb 24, 2015 at 1:44 PM Post #3,293 of 15,996
xymordos said:
  I just completed another universal - was pretty interesting to make. I used a GR31587 which I've never seen before. Luckily it seems to sound pretty good. 
 
Drivers used: HODVTEC31618, BK26824, GR31587, SWFK31736
 
I used a 1mm teflon tube each for the GR and SWFK, and merged into a 2.5mm diameter stainless steel tube. A 1mm teflon tube was used for the BK. I also used a 10cm long 0.5mm silicon tube for low pass filter on the HODVTEC, which resulted at a cutoff at around 100-200Hz. There was actually too much bass from the HODVTEC, so I added a resistor on it, which I just attached to the shell as a pot to turn the bass. The Estron wires were really really convenient to use - I do recommend them as the connecting wires for drivers.
 
Thinking back, I might use a Sonion 3300 and 3800 instead of the BK and HODVTEC next time to change the sound a little. The mids are a little dry currently. I also need to improve the passive crossovers for the GR and SWFK.
 
 

 
Click to expand...

7 driver universal... impressive. Generally good driver choice.
 
Feb 24, 2015 at 1:54 PM Post #3,294 of 15,996
I got them off Mouser actually. They were very expensive but I can get them reimbursed. 
 
Feb 24, 2015 at 1:55 PM Post #3,295 of 15,996
Thanks! I actually really liked the GR for highs, but not sure if there would be enough extension if I didn't use the SWFK. The ~6kHz peak of SWFK is very difficult to deal with. Also the 10cm tube was very hard to fit into the shell :p
 
I would actually like to ask about which drivers were sub optimal in the config, and which I should improve on? I'd like to get a general driver config and then play around with XOs to improve sound.
 
Feb 24, 2015 at 8:20 PM Post #3,298 of 15,996
piotrus-g said:
  haha and I didn't want to say what you could change to avoid discouraging you.
 
I meant to say I'd swich from SWFK to TWFK because of SWFK's 6kHz peak :)
Click to expand...

 
Ooh interesting! Does the WBFK also have the same problem? I didn't choose the TWFK because the description mentioned about it being coupled with a low frequency FK, which I thought should work as a full range rather than a tweeter :p Would the TWFK be loud enough for the response in the 10kHz+ regions? Thanks for your input, there's no discouraging at all :p
 
Feb 24, 2015 at 10:40 PM Post #3,299 of 15,996
kellogsx said:
  How did you manage to make it hollow from the start?
Click to expand...

 
I used a salt and pepper application. I used a small squeeze bottle of the acrylic powder and an eyedropper for the monomer liquid. blow a little powder onto the mold using the squeeze bottle and than apply a little monomer over the same spot, I would keep doing that all around the mold until I built up a thick enough wall to be rigid and strong. I stopped making shells that way because they ended up with very thick walls and not as much space left on the inside for drivers as I would like and because the monomer is none to good for your health and It was making me feel a bit ill.
 
It looks like your shell is a bit rough around the edges. I recommend sanding that down until it is nice and smooth before putting it in your ear. I have scratched the inside if my ear before and it is not fun.
 
Feb 25, 2015 at 1:55 AM Post #3,300 of 15,996
kellogsx said:
 
I'm using a clear cold curing acrylic from Dreve Dentamid, since I'm already a customer of them but I've been in contact with Dreve Otoplastik to see if I could get hold of some Fotoplast as a sample.
 
When using the acrylic I'll be doing a solid piece which I then will have to drill out to make a shell, already done it once and it came out pretty good. But hopefully I'll get some Fotoplast instead and make some proper shells.
Click to expand...

 


If you use cold cure acrylic, you can do wait and turn down method for shells.There is blurry surface at inside of shell.

More explanation for method:
Heat the negative mold, then pour acrylic mixture(cold mixture is recommended) to negative. Wait until a rim begin at the border of mould, rim thickness means wall thickness of shell, then turn out the acrylic. Cold cure acrylic is using by westone as I know, it is very robust material. This info is expensive info for me, it costs to me about 3-4kg cold acrylic. :)
 
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