I don't know if it's necessarily an error, it just seems to me that it's normalizing to the z distance and only the z distance, not the true driver to mic distance, which makes sense to me. So if the mic is at a z of 2m, the normalization is independent of where you place the mic on the x-y plane and therefore the low frequency spl drops as the microphone moves away from the driver in the x-y plane. It would be nice if it normalized for the overall distance but that also wouldn't really make sense for multiple drivers located at different points on the baffle.
I see where it seems that the cos angle would approximate similarly to a dipole but I believe this effect is coming from the distance not from the dipole effect
I see where it seems that the cos angle would approximate similarly to a dipole but I believe this effect is coming from the distance not from the dipole effect
I agree that if SPL was being normalized by z distance rather than true driver to mic distance as mentioned in the manual, then you would match the EDGE results for monopole.
Works for me.
... as long as people are aware of it when trying to match polar measurements with EDGE results.
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Since EDGE normalizes the response relative to on-axis SPL at the same distance, this is unnecessary. From the documentation: “The response is normalized so that the sum of all driver sources corresponds to 0dB if they had been located at the same distance to the mic.”
I haven't re-read the manual, but I understand that this applies only to multiple drivers in same baffle (they often have different path lengths) in one "measurement"
I haven't re-read the manual, but I understand that this applies only to multiple drivers in same baffle (they often have different path lengths) in one "measurement"
BY “sources”, the manual means the individual point sources that are used to represent a driver. If multiple drivers are used, all of the point sources making up all of the drivers would be summed to correspond to 0dB with all sources set at distance z from the mic.
You can test this with two small drivers on a HUGE baffle, and mic placed directly in front of driver #1 with z=1m. With driver #2 directly adjacent to driver #1 you get +6dB SPL level. Move driver #2 away from driver #1 and the SPL level (below the comb filter range) drops in agreement with hand calculations normalizing all source points for both drivers at 1m.
The math works 🙂
Normalizing by z certainly simplifies things when multiple drivers are involved and it is unclear what distance to use for normalization. However, this normalization choice does prevent the ability to easily create a set of polar response curves at incremental angles for a constant “true distance” from mic to center of a driver(or other reference point) as is typically done when measuring.
You can test this with two small drivers on a HUGE baffle, and mic placed directly in front of driver #1 with z=1m. With driver #2 directly adjacent to driver #1 you get +6dB SPL level. Move driver #2 away from driver #1 and the SPL level (below the comb filter range) drops in agreement with hand calculations normalizing all source points for both drivers at 1m.
The math works 🙂
Normalizing by z certainly simplifies things when multiple drivers are involved and it is unclear what distance to use for normalization. However, this normalization choice does prevent the ability to easily create a set of polar response curves at incremental angles for a constant “true distance” from mic to center of a driver(or other reference point) as is typically done when measuring.
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