@Hörnli
I’m glad you encouraged me to push forward with testing via dynamic microphones. Their high SPL handling capability means that their own self distortion are closer to being able to match the classically powered B&K and G.R.A.S. capsules with external polarisation.
As we can see, there’s variation in both H2 and H3. How much depends on how close the mic is to its limit, but also peculiar differences in the mic. Is it the mic capsule or the electronics?
I remember we were commiserating about how “DIY is dead”.
🤣 I wasn’t ready to accept that yet, so I dutifully followed your lead to look at STEPS. As I had to RTFM to set it up...I realised that Ivo had already down a mic comparison decades ago.
Well knock me down with a feather!
"Three microphones were compared: an inexpensive model (MM-1 T-Bone, costing around € 35), a mid-range model (Audix TM1, around € 300), and a class 1 reference microphone (NTI M2210, cost around € 1100)"
I was suspicious that
€€€€ could be the only factor, so went to look at the mic specs a bit closer and…
MM-1 has max
SPL of 110dB (1% THD)
TM1 has max
SPL of 130 (1% THD)
NTI M2210 has max SPL of 144dB (3% THD)
( ?
134dB @1% THD)
@IamJF showed us his ECM8000, MicW M215 and Earthworks M50 and B&K 40BD
—> large difference in maximum SPL, and corresponding differences in THD at specific observed SPL.
Now, with a dynamic omnidirectional microphones do not have flat perfectly flat frequency response, so there’s no free lunch (yet). A user has to create an electronic compensation file from a known reference. My own compensation file was created using the Earthworks M23 as a baseline comparator. And Earthworks mics calibrated using an ACO Pacific microphone AFAIK. So we are comparing a mic to a compared mic, so any error might add up, or average out; it’s hard to know which.
Sonarworks appears to be comparing their mics to a “ANSI reference mic”, and it appears that miniDSP are also using a microphone substitution technique.
But suppose we are off by even +/- 1dB), that seems close enough for
distortion measurements with modern software.
So it’s not calibration by an electrostatic actuator setup, but it’s certainly not “plug and play” . If one is not experienced in measuring speakers or microphones, I wonder how much error would creep in from using the generic curve from the data-sheet.
As
@bwaslo explained succinctly, a mic’s (or recording chain’s) non-flat frequency response doesn’t affect the ability to measure the frequency response- as long as it is known and be taken into account. On the other hand, it may affect dynamic range and noise if the compensation is excessive.
How much is too much?
Well, I’d think anything around 3dB compensation is reasonable. 6dB at the maximum. More than means that boosting the noise by double creates more imprecision. As you can see to the right of the graph, the uncertainty goes up as the frequency response of the Sennheiser MD42 falls off a cliff in the top octave.
Other microphones options include Sennheiser MD21-U, a classic dynamic microphone that has been around for 60 years. I’m not sure how the older models do, like speakers and voice coils probably shift with increasing age.
There’s also the Audio Technica 4022 omnidirectional condenser mic with self noise 13dB(A) and of 160dB @3 % THD
. ?110dB with 0.01%. This is as close as I can find without going for a classical setup.
Hopefully
@bwaslo can pull me out of this microphone deep dive by offering a wide bandwidth microphone out to 40KHz with good SPL handling capacity and low noise in the next iteration of Omnimic!
