Other than the proximity bass effect which is typically effective under ~100Hz and only when the mic is close(~12" or less) from the sound source, are there any other reasons why cardioid mics are not used in speaker measurements ?
There are many studio and recording mics with very good noise and distortion performance. and we calibrate our mics anyway for FR, so wouldn't these be good candidates for measurement purposes also ?
There are many studio and recording mics with very good noise and distortion performance. and we calibrate our mics anyway for FR, so wouldn't these be good candidates for measurement purposes also ?
While I see your point, I think the proximity effect is more of an issue than you might think. You can only calibrate "flat" at one distance. Moving by a few metres might change things by 3dB and while that isn't a huge difference, I wouldn't count it as a "reference" mic any more.
The proximity effect can also reach up past 500Hz - it's a bell curve, after all.
Chris
The proximity effect can also reach up past 500Hz - it's a bell curve, after all.
Chris
I do not think that is true, connect any reasonable omnidirectional mic to a micpreamp and listen to the output with headphones or loudspeakers, there is a huge difference. Our hearing is a lot more sophisticated and complex then a simple mic
Bell Curve ??
The only situations I can think of this being a problem is for nearfield and port response measurements, both of which are not all that common nor absolutely required for xover or box design.
I am not an expert on microphone capsules, but here are some ideas:
- The pattern of a cardioid capsule is not a perfect cardioid. This gives a false sense of security, as sounds outside of the pattern are still picked up at some frequency ranges.
- An omni pattern is OK because time gating is possible, meaning reflected sounds can be filtered out at the cost of frequency resolution.
- If reflected sound must be avoided, time gating is required anyway, because a cardioid pattern is not likely to fully reject sound coming from outside its pick up pattern. It would only reduce them, which might not suffice.
What would be the advantages of a cardioid microphone?
- The pattern of a cardioid capsule is not a perfect cardioid. This gives a false sense of security, as sounds outside of the pattern are still picked up at some frequency ranges.
- An omni pattern is OK because time gating is possible, meaning reflected sounds can be filtered out at the cost of frequency resolution.
- If reflected sound must be avoided, time gating is required anyway, because a cardioid pattern is not likely to fully reject sound coming from outside its pick up pattern. It would only reduce them, which might not suffice.
What would be the advantages of a cardioid microphone?
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It is in the very nature of cardioids that they are super-sensitive regarding placement. You get the alignment wrong slighty - and you will get a different response measurement. Every time.
This can surely be overcome to some extent, but why bother with the extra trouble and insecurity? Tools are supposed to make things easier (at least we'd like to think so). Cardioids do that for recording, but separating instruments is very different from getting a repeatable measurement.
/G
This can surely be overcome to some extent, but why bother with the extra trouble and insecurity? Tools are supposed to make things easier (at least we'd like to think so). Cardioids do that for recording, but separating instruments is very different from getting a repeatable measurement.
/G
I have used a cardioid mic for years to measure room EQ. I checked its calibration against a calibrated cardioid. For me it works better than an omni in matching what I see on the FR graph to what I hear in the room. Why? Maybe because my ears and head are not omni-directional, trending to pick up more from the front than the back. The cardioid mic is like that, too.
And yes, I also use an omni mic.
And yes, I also use an omni mic.
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