Looking at this product brief, the 4, 5.8, 6 and 8 mm models all have a nasty HF peak whereas the 9.7 mm is pretty flat.
New Audio Solutions | HD Series Microphones
I seem to remember that you want a small cross-section for flat response under 0° incidence. For these models, this does not seem to be the case.
I wonder about the role of how they are constructed. The 8 mm easily has the nastiest peak at 15 dB, and overall, there is no correlation with size. Even the pin version of the 5.8 mm fares better than the surface mount version of the same size?!?
Does anyone know which type of FET is used? The S/N is unrivalled except for some of the newer Primo microphones which incidentially have the sam S/N for each size class.
New Audio Solutions | HD Series Microphones
I seem to remember that you want a small cross-section for flat response under 0° incidence. For these models, this does not seem to be the case.
I wonder about the role of how they are constructed. The 8 mm easily has the nastiest peak at 15 dB, and overall, there is no correlation with size. Even the pin version of the 5.8 mm fares better than the surface mount version of the same size?!?
Does anyone know which type of FET is used? The S/N is unrivalled except for some of the newer Primo microphones which incidentially have the sam S/N for each size class.
9.5mm is still small, its one wavelength at 35kHz. Response patterns are complicated at the best of times, at least you get to see the curve! The capsule itself will have resonances both of the air and itself, and these will interact and with the natural frequency of the diaphram, there's an inordinate amount of physics involved!
For these small electrets S/N is probably limited by diaphram area, not just the FET.
For these small electrets S/N is probably limited by diaphram area, not just the FET.
Yes, the bigger the diameter, the higher the sensitivity and the better the S/N. I suspect they use the same FET in all the HD series, the S/N of each of them being way better than for sister parts without the HD.
Same thing with Primo. Their EM-100 (EOL, most recent data sheet from 2007) specifies > 60 dB which is not stellar for a 10 mm capsule (which is pretty flat at + 4 dB). Their 2015 EM-172 (also EOL) has 80 dB for the same size and is a tad flatter but also droops towards 20 kHz. It's successor, the 2017 EM-272 has the same S/N and response but slightly higher max SPL (so FET with different parameters?).
Same thing with Primo. Their EM-100 (EOL, most recent data sheet from 2007) specifies > 60 dB which is not stellar for a 10 mm capsule (which is pretty flat at + 4 dB). Their 2015 EM-172 (also EOL) has 80 dB for the same size and is a tad flatter but also droops towards 20 kHz. It's successor, the 2017 EM-272 has the same S/N and response but slightly higher max SPL (so FET with different parameters?).
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This is from Richard Lee's SimpleP48.pdf
EM172 - It uses a NEC 2sk4027 FET which is about 10dB quieter than the Panasonic one in WM61A.
and
Present (2018) EM172 production may not use the NEC 2sk4027 FET . This has max Idss
340uA while EM172 and present Primo spec max Idss 600uA. Eric #293696: thinks they use
the SM version of NEC 2sk660 max Idss 500uA
EM172 - It uses a NEC 2sk4027 FET which is about 10dB quieter than the Panasonic one in WM61A.
and
Present (2018) EM172 production may not use the NEC 2sk4027 FET . This has max Idss
340uA while EM172 and present Primo spec max Idss 600uA. Eric #293696: thinks they use
the SM version of NEC 2sk660 max Idss 500uA
Yes, 110 dB is not great and much worse than the 120 dB of EM172 or 122 dB of EM272, but that wasn't my question here. Interestingly, it does not seem to originate in the membrane and back plate assembly, as reports of 130 dB achieved with the 5024 capsule after adding a voltage feedback cap have been reported.