dear richard we are almost there. The mechanics was easy, but figuring out a reliable calibration system proved quite tough. We now have a system where we take 40 measurements on a hemisphere using angelo's log sine sweep. the inverse sine is corrected once every session with a calibration microphone. We now have it down pat. The next stage was taking these 40 x 4 irs and producing a small 4 x 4 matrix of filters to use with brahmavolver. Angelo again provided the Matlab scripts he uses and Marc Lavallée has converted these to Octave and has sent me a virtual OS(also called Brahma, but it is a pared down Debian). We create a new microphone folder, copy all the ir files (five x four channels) and the program (also called Brahma) cuts the eight irs in each file to 256 samples, and then does all the math needed to generate the output 4 channel file - about 33 k in size. I have not listened with filters for the prototype Brahma with which I have done some recordings as it was only measured today. but using FilterMatrix derived for other microphones seems to work quite well. I had dismantled my ambisonics rig and have not set it up yet, but I use VVMic to test rotation and zoom etc. the most amazing effect I have heard is to zoom out and the sound almost disappears, and then rotate 180 degrees for closeup sound? The image does not collapse at all, and in one recording I can rotate and tilt the mic to centre on an airconditioning duct. Yes the Zoom H2 is a very good device and when it came out there was no other low cost four channel recorder. H2N is a higher quality device except for the annoying habit of treating the two channels at the rear as ms, converting to xy and then calling the file MS. You must have seen the photos of the brahma tetrahedron mounted in the h2n. Ten of them have been measured and 6 are calibrated with their own FilterMatrix files. But today, finally, I got to hear the standalone Brahma microphone with its Phantom power adaptor. Connected with shielded cat 6 cable and a five-pin adaptor to the zoom, it is dramatically better than the Brahma connected directly to Zoom H2N. I have a nice little circuit that has enormous gain (almost line level), very little noise and sweet sound! I wish there was a place to upload samples. I do not have rights to put out entire recordings, but small five minute samples would be nice. I have classical Hindustani music played on the saxophone, and a sarod and table recording. We have orders for nearly 50 all told (from the kickstarter). After that, I would like to send a few out (one to each continent) for people to try out and pass it on, sort of. My aim is not selling more, but get people to listen and tell me what they think. (this mail has gotten so long I think I should post it to the group as well. umashankar From: [email protected] To: [email protected] Subject: Zoom H2 / Brahma Date: Wed, 12 Mar 2014 13:42:37 +0000
Hi there! I was contacted last week by someone wondering about using the H2 unmodified for WXY ambisonic recording and I ran through the maths that Paul Hodges put at http://ambisonic.info/zoomh2.html - it looks right to me! I ran a quick experiment with my brother’s H2 and it seemed basically fine. I’ve emailed him to find out a bit more about whatever problems he was having. Anyway, I’m rather impressed with the H2 – I clearly hadn’t looked at it carefully enough and I can certainly see why what you’re doing around the Brahma mike makes good sense! I’d love to hear how this is getting on, and if we can help. Are the capsules behaving themselves in context (e.g. not collapsing too badly to mono)? Many thanks! Best wishes, --Richard -------------- next part -------------- An HTML attachment was scrubbed... URL: <https://mail.music.vt.edu/mailman/private/sursound/attachments/20140312/bd177975/attachment.html> _______________________________________________ Sursound mailing list [email protected] https://mail.music.vt.edu/mailman/listinfo/sursound
