--Richard
> On 12 Mar 2014, at 14:11, umashankar manthravadi <umasha...@hotmail.com> > wrote: > > 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: rich...@blueripplesound.com > To: umasha...@hotmail.com > 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 > Sursound@music.vt.edu > https://mail.music.vt.edu/mailman/listinfo/sursound _______________________________________________ Sursound mailing list Sursound@music.vt.edu https://mail.music.vt.edu/mailman/listinfo/sursound
