Dusty Diaphrams
Hi Pelanj,
Please don't worry about the absolute db level in my measurements. I used DATS V2 to drive the JBL's and it's certainly not putting out even 1 watt at maximum output.
I went ahead and pulled the diaphragm out and as I drew it out ever so carefully I could immediately feel the voice coil scratching its way out of the gap. Oh dear!
Under there it was very dusty and dirty.
First I got the vacuum onto the phase plug and gap with the brush attachment. Then I sent several strips of masking tape around the gap.
First pass treasure...
Second pass....
I had a hell of a time bringing out several small pieces of magnetic schwarf. You can see it circled here. I think the area of the phase plug with the arrow is pitted, I wonder if this is from bits smashing around in there?!
Here is the big one stuck to some double sided tape:
Anyway she's all cleaned up and back together. I'll definitely do this first for driver 2 before measurements!
Hi Pelanj,
Please don't worry about the absolute db level in my measurements. I used DATS V2 to drive the JBL's and it's certainly not putting out even 1 watt at maximum output.
I went ahead and pulled the diaphragm out and as I drew it out ever so carefully I could immediately feel the voice coil scratching its way out of the gap. Oh dear!
Under there it was very dusty and dirty.
First I got the vacuum onto the phase plug and gap with the brush attachment. Then I sent several strips of masking tape around the gap.
First pass treasure...
Second pass....
I had a hell of a time bringing out several small pieces of magnetic schwarf. You can see it circled here. I think the area of the phase plug with the arrow is pitted, I wonder if this is from bits smashing around in there?!
Here is the big one stuck to some double sided tape:
Anyway she's all cleaned up and back together. I'll definitely do this first for driver 2 before measurements!
Attachments
Last edited:
Horn 2 measurements
I cleaned the second CD before measurements this time. It was about 5 times worse in the gap on this one. Heaps of metal bits in there. Took ages to clear them out.
Some measurements all with 5ms windowing, at 90cm distance, Omnimic and driven from DATS V2:
On axis no smoothing...
Off axis 0-40 degrees 1/2th smoothed...
Polar 1/2th smoothed.....
Horn 1 vs Horn 2 on axis no smoothing:
Using my first try crossover presented previously here's the simulated XSim response Horn 1 in green, Horn 2 in black...
For horns stamped with build dates in August and October 1986 I'm thinking that's pretty good agreement between this pair 34 years later?!
I cleaned the second CD before measurements this time. It was about 5 times worse in the gap on this one. Heaps of metal bits in there. Took ages to clear them out.
Some measurements all with 5ms windowing, at 90cm distance, Omnimic and driven from DATS V2:
On axis no smoothing...
Off axis 0-40 degrees 1/2th smoothed...
Polar 1/2th smoothed.....
Horn 1 vs Horn 2 on axis no smoothing:
Using my first try crossover presented previously here's the simulated XSim response Horn 1 in green, Horn 2 in black...
For horns stamped with build dates in August and October 1986 I'm thinking that's pretty good agreement between this pair 34 years later?!
Attachments
Last edited:
......I dented the foam in the back chamber with a thumb, it isn't springing back...
Replace the old foam before it starts to crumble.