Hello everyone,
I’ve designed a large diaphragm condenser microphone capsule, but I’m encountering a few issues with the first assembled prototypes. Does anyone have any advice or suggestions?
The capsule is edge-terminated with a large diaphragm. It works, but it lacks high frequencies, making the sound quite muffled. I’ve tested it with both transformer-based electronics (similar to the KM84 style) and transformerless electronics.
Based on calculations (considering the area and distance between the diaphragm and backplate), I was expecting a capacitance of 100pF. However, when I measure the assembled pieces (only 3 so far), I’m getting 300pF, 350pF, and 390pF.
I suspect the lack of high frequencies is due to the high capacitance (the cutoff frequency is too low). I’m trying to understand why the capacitance is so high. It could either be due to parasitic capacitance or because the distances vary from the design during assembly.
Here’s a bit more detail to help anyone with experience on this chime in with their opinions...
My capsule, though different, is built similarly to a CK12. The brass backplate is housed inside a plastic support, and the outer ring that holds the diaphragm is screwed onto the plastic support. I’ll attach a couple of sectional images showing the construction (indicative drawing, not to scale).
The diaphragm is 5µm mylar with an aluminum coating, sourced from a supplier I’ve seen mentioned here on the forum.
I used 50µm kapton as the diaphragm spacer. The plastic material for the prototype is 3D printed PA12 nylon (MJF), and the brass backplate adheres to the design tolerances.
For the electrical connection to the backplate, there’s a small extension that protrudes on one side (as illustrated in the second image).
Could it be that the materials used (the PA12 plastic support or the kapton) don’t provide adequate electrical insulation, leading to parasitic capacitance? Or do you think parasitic capacitance could be forming elsewhere?
Another possibility I’m considering is that during assembly, the kapton spacer might be getting compressed, so instead of 50µm, the actual distance is less.
Please note, as shown in the first image, the plastic support is slightly thinner than the backplate (to avoid plastic tolerance issues), but there’s only a gap of about 0.2mm. I did this so the distances would rely only on the brass parts, where I have better control and precision.
Thanks in advance to anyone who can offer some insights or advice!
I’ve designed a large diaphragm condenser microphone capsule, but I’m encountering a few issues with the first assembled prototypes. Does anyone have any advice or suggestions?
The capsule is edge-terminated with a large diaphragm. It works, but it lacks high frequencies, making the sound quite muffled. I’ve tested it with both transformer-based electronics (similar to the KM84 style) and transformerless electronics.
Based on calculations (considering the area and distance between the diaphragm and backplate), I was expecting a capacitance of 100pF. However, when I measure the assembled pieces (only 3 so far), I’m getting 300pF, 350pF, and 390pF.
I suspect the lack of high frequencies is due to the high capacitance (the cutoff frequency is too low). I’m trying to understand why the capacitance is so high. It could either be due to parasitic capacitance or because the distances vary from the design during assembly.
Here’s a bit more detail to help anyone with experience on this chime in with their opinions...
My capsule, though different, is built similarly to a CK12. The brass backplate is housed inside a plastic support, and the outer ring that holds the diaphragm is screwed onto the plastic support. I’ll attach a couple of sectional images showing the construction (indicative drawing, not to scale).
The diaphragm is 5µm mylar with an aluminum coating, sourced from a supplier I’ve seen mentioned here on the forum.
I used 50µm kapton as the diaphragm spacer. The plastic material for the prototype is 3D printed PA12 nylon (MJF), and the brass backplate adheres to the design tolerances.
For the electrical connection to the backplate, there’s a small extension that protrudes on one side (as illustrated in the second image).
Could it be that the materials used (the PA12 plastic support or the kapton) don’t provide adequate electrical insulation, leading to parasitic capacitance? Or do you think parasitic capacitance could be forming elsewhere?
Another possibility I’m considering is that during assembly, the kapton spacer might be getting compressed, so instead of 50µm, the actual distance is less.
Please note, as shown in the first image, the plastic support is slightly thinner than the backplate (to avoid plastic tolerance issues), but there’s only a gap of about 0.2mm. I did this so the distances would rely only on the brass parts, where I have better control and precision.
Thanks in advance to anyone who can offer some insights or advice!
