I thought I would take some pictures and describe the process of removing the protection grids from the drivers. It was actually much simpler than I thought it might be with no real danger as long as some simple precautions are followed. I used a layer of Kapton tape over the grid then I used a scrunched up piece of aluminium foil stuck on top. I have a fancy Dewalt heat gun that lets me set the temperature and has some nice attachments to funnel the heat down to a small area. I set the heat gun to 200 Degrees C and moved it around in circles on the groove that the protection grid sits in for about 20 to 30 seconds. I used three bamboo skewers to lift the grid off on one side then using the skewers underneath to stop the magnet from pulling it back down, then moved to the other side and levered it out of the gap. Just be careful and only use non metal tools. The magnet is super strong and you don't want to pull anything into the dome. If you get the heat gun too close the magnet will pull it onto the protection grid.
You can see the remenants of the heat activated glue in the groove and also that on the T34A the surround is fixed to an area that is in line with the main face. The surround is an "outie" in case anyone was wondering. I still think a small spacer gap is worthwhile with this driver. I need to make a few smaller test prints of the throat opening to get the size where I want it to be.
You can see the remenants of the heat activated glue in the groove and also that on the T34A the surround is fixed to an area that is in line with the main face. The surround is an "outie" in case anyone was wondering. I still think a small spacer gap is worthwhile with this driver. I need to make a few smaller test prints of the throat opening to get the size where I want it to be.
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Yes it would the magnet is really strong, I suspect it is a belt and braces solution to try and make sure the dome isn't damaged by something knocking the grid out of the groove. The variable thickness domes Bliesma uses won't take much force to damage them. By taking the grids off with heat there is no damage to anything so the grid could just be put back in place and held by the magnet if that was wanted.
Anyway, who would have guessed a few years ago that you can take a 34mm dome and get a very wide constant directivity virtually up to 20 kHz - actually wider than with many smaller tweeters. And all you need is a tall hard dome and some stupidly shallow waveguide... I think I also showed somewhere what difference a flat-baffle mounting makes. It's simply a waste of such a great tweeter, used that way, so I think the grid should be easily removable 
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Wouah 200° !! even with some protection I would be reluctant to do that
Just as a reminder, the recommended procedure directly from Mr Malikov, put the driver in a oven set before at 60-70° (check the real temp before with instrument) for 5-7 minutes and voilà. I followed this procedure on several T25B and T34B
Just as a reminder, the recommended procedure directly from Mr Malikov, put the driver in a oven set before at 60-70° (check the real temp before with instrument) for 5-7 minutes and voilà. I followed this procedure on several T25B and T34B
No need to worry, it is not 200C when it hits anything, you can wave your hand in front of a gun at 400C as long as it isn't right at the exit or for too long. I started at 80C and I would have been there for a long time, so I ramped it up a bit. The exit of the heat gun attachment was about 15mm so it was directed right at the groove for a very short time. The rest of the driver was stone cold. I have a nice little oven for drying filament but I chose not to bake the drivers. I have a set of T25B to do in the future and won't be baking those either
I just use a small screw driver or tweezers, get in one of the holes of the grid and carefully lift it. You can use a pencil to form a lever to have more control. Just until it lifts a little, then do the next spot. The glue is not that strong.
Takes a minute to do.
Found a pic:
Sorry, a little bit ot: does anyone know if the T34A fits the Jantzen waveguide made for the Seas T35?
http://www.troelsgravesen.dk/TQWT-DTQWT-mkII-T35.htm
http://www.troelsgravesen.dk/TQWT-DTQWT-mkII-T35.htm
On a related point I have printed some test rings of different diameters to decide on the best throat size to print. The drawing I got from Stanislav had the diameter including surround as 38mm. This is too small, the manufacturing and use of a fabric do not match the CAD exactly. The printer usually ends up with the inside diameter of the ring being ever so slightly more than what was asked for which is not a bad thing. The ring that is big enough to clear the surround but leave hardly any space is 39.5mm (probably more like 39.7mm if measured, which is hard to do on a small plastic ring that can be compressed or stretched easily by the callipers). In the attached image you can also see the spacer which covers the mounting flange up to where the surround starts and fits nicely with some ears that slot into the mounting hole recesses. You can see the ring in the image although black on black is hard to see. If you zoom in you can see that the ring is pushed up against the surround at the bottom and the gap is at the top centre to right side.
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A dissapointing day of print failures where the CF Gremlins returned, but the bits that did print show that the fit is good for the throat and the heat set inserts fit nicely in their pilot holes.
I am hopeful that the QIDI ABSGF25 filament will not be so awkward in the feed tube as it has a solid layer of ABS all around the outside with the abrasive in the centre of the extrusion. ABS slides very easily in the PTFE tube normally.
I am hopeful that the QIDI ABSGF25 filament will not be so awkward in the feed tube as it has a solid layer of ABS all around the outside with the abrasive in the centre of the extrusion. ABS slides very easily in the PTFE tube normally.
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The GF filament was a total failure, back to the drawing board on that one. The other QIDI filament I bought, ABS Rapido lived up it's name and printed very fast and in decent quality. I was able to get a very smooth finish with minimal sanding and wiping some acetone from a paper towel. Some filling and sanding is still needed for me to be happy with how it looks for use in a speaker I could see though
These pictures are with the driver attached to the heat set inserts. Some extra inserts performed secondary duty as spacers due to not having the right sized M4 bolts available.
These pictures are with the driver attached to the heat set inserts. Some extra inserts performed secondary duty as spacers due to not having the right sized M4 bolts available.
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Measurements will come but I can’t promise when. I still need to finish the turntable and verify the new measurement equipment I have bought. Both are much harder to find the time for like finishing the CNC….
I bought the printer on a Black Friday sale but only got it out of the box about a month ago.
I bought the printer on a Black Friday sale but only got it out of the box about a month ago.