Thanks Claudio,
So with my 5cm diameter mid that's about 2200Hz. Just scrapes in 🙂 Just curious does it make a difference if its a cone, or a dome?
Also, what is the theory behind it not being usefull, is it because the high freq's are too directional, so if you are too close you are not getting everything?
Tony.
So with my 5cm diameter mid that's about 2200Hz. Just scrapes in 🙂 Just curious does it make a difference if its a cone, or a dome?
Also, what is the theory behind it not being usefull, is it because the high freq's are too directional, so if you are too close you are not getting everything?
Tony.
Hi Tony,
I don't think it makes difference between cone or dome, keeping in mind that the Far Field response is already usefull from 300Hz with a 4 ms. of useful gated data.
In the NF at higher frequencies pressure waves from different points of the driver diaphragm may arrive out of phase to the mic, therefore some cancellation can happen in the response.
If, for example,you want to measure a ribbon driver, the near field cannot be taken very close, (as for the known formula) since the ribbon dispersion depends on distance; so every situation has to be studied individually.
Regards
Claudio
I don't think it makes difference between cone or dome, keeping in mind that the Far Field response is already usefull from 300Hz with a 4 ms. of useful gated data.
In the NF at higher frequencies pressure waves from different points of the driver diaphragm may arrive out of phase to the mic, therefore some cancellation can happen in the response.
If, for example,you want to measure a ribbon driver, the near field cannot be taken very close, (as for the known formula) since the ribbon dispersion depends on distance; so every situation has to be studied individually.
Regards
Claudio
Besides the frequency limit to nearfield that Claudio posted, you're also assuming pistonic behavior with negligable contribution from the surround. These are good approximations in the bass, but certainly not in the midrange.
If you see a dip at 1.2K and at its harmonics, there's a 99% probability that you're measuring an interference effect.
If you see a dip at 1.2K and at its harmonics, there's a 99% probability that you're measuring an interference effect.
Thanks Claudio and Sy.
Looks like I need to do some more experimenting to determine where the interference is coming from. Probably be a good idea to model it in the baffle diffraction spreadsheet I downloaded from the FRD site. I just have to get through the docco
Tony.
Looks like I need to do some more experimenting to determine where the interference is coming from. Probably be a good idea to model it in the baffle diffraction spreadsheet I downloaded from the FRD site. I just have to get through the docco
Tony.
Sorry I dig up such an old thread. I have built Rod elliots project 93 mic preamp for use with an electret mic I bought. The mic datasheet is here AOM-4544L-R I did not buy the panasonic mics coz it costs quite abit with shipping and since I am also not confident of building the preamp. So i bought the mic in the link which was pretty cheap just for playing around.
I built figure 6 schematics of Rod elliots project 93. Powered it using 9V battery and connected to my soundcard. When i put the mic close and speak into it, I am able to hear. However once I put the mic further away from my mouth and speak I can't hear. Have I messed something up ?
I built figure 6 schematics of Rod elliots project 93. Powered it using 9V battery and connected to my soundcard. When i put the mic close and speak into it, I am able to hear. However once I put the mic further away from my mouth and speak I can't hear. Have I messed something up ?
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