Yep, I would hope to see an additional WG to play with as well. Might be kind of hard to use the other even if it was available.
Yep, I would hope to see an additional WG to play with as well. Might be kind of hard to use the other even if it was available.
Always fun learning more.......
Hi there folks, first message here on the forum but I've be looking around since a looooong time and finally took the chance to contribute to the forum and give a little back myself.
So. I'm the happy owner of three new D2415K compression drivers I bought for my DIY projects and I wanted to share some pictures and findings that followed their unboxing.
First, a picture to illustrate the size of the driver next to an SEOS 12 waveguide :
With the SEOS 12 on top
Driver size is really small when you compare it to this 12" horn, we will need an adapter plate to attach it to an 1" Waveguide or a custom one. More on that later. Note that spacing between mounting holes on the driver are about 40mm.
Next is a closeup of the throat. I just quickly throw the SEOS 12 on top to snap some pics, here are the results
Closeup pic reveal the protective mesh ring that is about one inch in diameter. Speaking of which... (see next post for more pictures, Audio Heritage limit is 5)
The mesh ring can be popped up !
I First give a try with my nail and feeling that it could come off, I grab a flat precision screwdriver, gently lift and the ring came out effortlessly with breaking or bending. In fact, there is only little glue bonding it and the remnants can be easily removed.
Closeup of throat
Closer
From a different angle we can see better the exit of the phase plug
For the next stage I made some basic impedance measurements...
And was pretty surprised to see the two drivers in series were 17.9 ohms !
Each driver are respectively 9 and 9.2 ohms
I measured the other two drivers and also found an impedance around 18 ohms
Driver physical measurements done with a digital caliper. Of course I rounded some values but if one want to make a precise Waveguide or scaled down M2, I think we need some precision.
Throat 19.6mm/0.77"
Outer ring 25.9mm/1.02"
Throat depth 30.2mm/1.19"
Ring mesh outside 25.35mm/0.998"
Ring mesh outside 20.86mm/0.82"
Ring mesh height 1.3mm/0.047"
Mounting holes 40mm/1.575"
Driver dimensions
Height 73.24mm/2.88"
Diameter 70.2mm/2.76"
Mounting ring diameter 45.9mm/1.8"
Mounting ring height 6mm/0.236"
The biggest disappointment for me is that I couldn't find the exit throat angle of the D2415K, I even asked Speaker Exchange but they could only get for me the same data as in the VTX-V20 brochure... bummer.
Any JBL Gurus out there who help us find this information ? Or is there any DIY way to get it, for instance, make a mold of the throat ? Or find a way to measure more deeply inside the throat with a caliper ?
Thanks.
Hi Stephane , thanks for taking the time to post these excellent pics and info.
To guage the exit angle I would suggest you make a round ball of childrens play putty and gently work it into the throat. You should be able to get enough of the angle left on the material so that you can measure it.
You will be safe doing this as the moving parts are not near the throat.
As it happens I am helping POS with the problem of mounting. In your case mounting to a bolt on , in his case mounting to a 1 1/8" screw on.
If you can find the angle it will be easy to design an adapter for bolt on.
Screw on has some complications but we think we have a solution , waiting on adapters that will then be modified.
Anyone have the faintest idea of the mounting screw guage ? metric or imperial ?
I am so glad you are helping me with this!
Regarding bolt size, here is the info I was able to gather so far:
http://www.audioheritage.org/vbullet...l=1#post397881
0.14" inner diameter, and I could not find any metric bolt that fits.
could be #8-32 : http://www.audioheritage.org/vbullet...l=1#post397891
I can't remember if I tested this, and I don't even know if I have 8-32 bolts at home.
Hi Stéphane,
I don't think you need to match the exit angle here.
This compression is supposed to present a flat wave shape at its exit up to the UHF, so that means the best bet is probably to consider it a 0° exit angle.
Regarding the best horn to use, a scaled-down version of the D2 waveguide would be the ticket as you mention.
It would be usable down to 1600Hz with a 8" woofer underneath, à la SCL-2: http://www.audioheritage.org/vbullet...0470-Jbl-scl-2
Scanning a D2 waveguide and printing the scaled down version would be a solution (hint: I have the D2 waveguides here, if you have the scanner and printer )
I plan to measure this compression with a 6" PT waveguide (the one used in the AC16), and compare it to the 2407 on the same waveguide (including off axis measurements).
All that should be possible soon thanks to the wonderful work Mac is doing on the adapters!
Just in case anyone out there is looking to use the 2415 on a thread in horn herels how I went about getting a fit.
The driver is tiny , and as described and measured the exit is 20mm . Most adapters are 24.5mm entry and for some reason a smidge smaller at the exit ( 0.94" ) but that seems to be the entry diameter for 1 3/8" screw on.
So the problem is that in the absence of ready made adapters and not having a lathe readily to hand i figured out a cheap way to McGuyver the modification of an off the shelf adaptor.
POS and I stumbled a little at the first hurdle , we got an adapter from Blue Aran here in the UK. Nice enough unit but it had a strange constriction in the middle where the bore reduced to about 16mm. I'm not sure what that was meant to do but it was not a fit for our cunning plan. Back they went.
So , POS went on the hunt on the www and among others came up with this.
https://www.ebay.fr/itm/282944921113
and about a week later they arrived in my post.
I was immediately impressed with the machining quality and overall finish , plus , the mounting slots and pre drilled holes offer just about every option you are likely to encounter.
So I'm looking to reduce the entry diameter to 20 mm. This drill has a 20mm step on it so .....
I then got some worktop laminate ( melamine ) that I had kicking about and drilled a hole in it. It helps if you drill a backing hole as the laminate is brittle so needs support. Then I cleaned off any rag edges and stuck it on the entry side of the adaptor. I just used solvent based household glue. Nothing too permanent.
Then I centered it by eye to get this Let it set.
The next step is to apply 2 part filler ( Bondo , Isopon etc ) It will help to scratch the surface inside first. Use a popsicle stick or similar and build up the taper. Don't be too heavy with the filler , you will end up with more sanding than you need to do.
Sanding can be done with copper pipe and 80 grit.
As is the way of these things the second one went much easier than the first. I found that it is best to sand from the snout end as this allows more control over any chance of expanding the entry hole
Let that cure and then remove the hole template and clean up glue residue.
The next step is to provide the mounting holes for the 2415. These are on a 40mm PCD and the snout threads are 33mm so there is only 3.5mm from the center of the hole till you whack the threads.
As far as I can gather the mounting screws are 4mm dia max so a 5 mm hole will be ample and allow some wiggle room to center the entry with the throat of the driver.
I did think about just extending the slots and started on one. Too much work.
I have a plan but I need to get in a pillar drill to get these accurately placed.
Carry on ....Mac
I just tried 8-32 UNC and... it does not fit.
Hi Ari,
Thank you.
Are you sure of that? It looks much bigger than what I measured.
There seems to be some confusion regarding the mounting screw spec for these tiny drivers.
It is NOT the same as on the D2 2430K. In European size the hole is just less than 4mm which translates to 5/32" Anyone have the faintest idea what thread this will most likely be ??
Anyway I pressed on and after much measuring I came up with this.
Using a 6mm drill and resting against the threads I drilled the 4 holes. As it turned out this provides a very good 40mm PCD for the holes , just what is called for on the driver.
As you can see I have filed away a little at the base of the snout to allow the screw head to seat properly.
Depending on the screws that POS gets he may have to do a little more filing.....
otherwise I think he will be good to go
Hopefully this will help anyone wishing to get a 2415 HF working with a screw on W/G or Horn
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