when you wire a pair of cardioids to make up a figure of eight, you need to
invert the signal on one of the cardioids. the simplest (after some trivial
buffer circuits) is to treat the two capsules outputs as a single out of phase
unbalanced signal. if you tap the two signals and combine them without making
them out of phase, you would have an Omni signal. Once the capsule signal is
buffered, this is not difficult to do. I had built mine with four opamps, three
as differential circuits to amplify the figure of eight signal, and the fourth
as a summer with six inputs to produce the Omni. the circuit worked but I am
only now begin to match my capsules reliably and accurately to justify it.
the figure of eights themselves of course will not combine to produce an Omni
(that was a mistake).
umashankar
.
> Date: Thu, 14 Nov 2013 16:49:41 +0100
> From: netti...@stackingdwarves.net
> To: sursound@music.vt.edu
> Subject: Re: [Sursound] New native B-Format microphone!
>
> On 11/14/2013 04:42 PM, umashankar manthravadi wrote:
> > if you feed the figure of eights to a mixer you can actually generate
> > a better Omni.
>
> now i'm confused.
> fig8s can never be combined to an omni.
>
> but if the microphone has in fact four cardioids, then you could combine
> them two two fig8s and an omni.
> but i don't see how you get those four capsule signals out of the mike
> through five pins in any sane way (where sane == balanced).
> can you explain in more detail?
>
>
> > Or, if the circuit is made of four cardioids each to
> > one pin, the circuit is still a pair of figure of eights, but all
> > four pins summed is a good Omni. I built my Velan, a six cardioid
> > native B format mic, where all six capsules contribute to the Omni.
> >
> > umashankar
> >
> >> Date: Thu, 14 Nov 2013 16:28:12 +0100 From:
> >> netti...@stackingdwarves.net To: sursound@music.vt.edu Subject: Re:
> >> [Sursound] New native B-Format microphone!
> >>
> >> On 11/14/2013 04:08 PM, umashankar manthravadi wrote:
> >>> one ground pin, two figure of eights with one or both receiving
> >>> phantom voltage, and two pins, one from each figure of eight, out
> >>> of phase for the Omni.
> >>
> >> you mean the omni will be a phantom circuit? oh my god, i only hope
> >> he can tame the demons he has summoned.
> >>
> >> after reading a few of jörg wuttke's papers on what can go wrong in
> >> even a simple phantom _power_ circuit, this remark makes me very,
> >> very afraid :)
> >>
> >> unless i'm very much mistaken, the achievable common-mode rejection
> >> now also depends on the relative twist between two pairs, and the
> >> problems with impedance matching between hot and cold have
> >> increased by a factor of two. where i live (in evil places with
> >> thyristor dimmers and long analog multicores), that's scary.
> >>
> >>
> >> -- Jörn Nettingsmeier Lortzingstr. 11, 45128 Essen, Tel. +49 177
> >> 7937487
> >>
> >> Meister für Veranstaltungstechnik (Bühne/Studio) Tonmeister VDT
> >>
> >> http://stackingdwarves.net
> >>
> >> _______________________________________________ Sursound mailing
> >> list Sursound@music.vt.edu
> >> https://mail.music.vt.edu/mailman/listinfo/sursound
> > -------------- next part -------------- An HTML attachment was
> > scrubbed... URL:
> > <https://mail.music.vt.edu/mailman/private/sursound/attachments/20131114/0a1cd334/attachment.html>
> >
> >
> _______________________________________________
> > Sursound mailing list Sursound@music.vt.edu
> > https://mail.music.vt.edu/mailman/listinfo/sursound
> >
>
>
> --
> Jörn Nettingsmeier
> Lortzingstr. 11, 45128 Essen, Tel. +49 177 7937487
>
> Meister für Veranstaltungstechnik (Bühne/Studio)
> Tonmeister VDT
>
> http://stackingdwarves.net
>
> _______________________________________________
> Sursound mailing list
> Sursound@music.vt.edu
> https://mail.music.vt.edu/mailman/listinfo/sursound
-------------- next part --------------
An HTML attachment was scrubbed...
URL:
<https://mail.music.vt.edu/mailman/private/sursound/attachments/20131114/38494a65/attachment.html>
_______________________________________________
Sursound mailing list
Sursound@music.vt.edu
https://mail.music.vt.edu/mailman/listinfo/sursound
