i forgotten how, but in school, we use to make very annoying clickers out of pieces of photofilm. even if i can remember how to make it, where will i find photofilm? umashankar
i have published my poems. read (or buy) at http://stores.lulu.com/umashankar > Date: Mon, 10 Oct 2011 11:49:11 +0100 > From: dave.mal...@york.ac.uk > To: sursound@music.vt.edu > Subject: Re: [Sursound] Soundfield-type mics: inverting or not? > > On 10/10/2011 10:42, Neil & Marcia Adams wrote: > > > > Who is old enough to remember the Keith Monks 'Phaserite' Checker > > http://dl.dropbox.com/u/14586505/Keith%20Monks%20Phaserite.pdf ? I last saw > > one 'in the flesh' > > 30-odd years ago. > > > > If you live in Europe or U.S. you might be able to locate one, or maybe > > they're still made? > > > > I have to admit I remember when this first came out - the modern equivalent > is the Optogate > <http://www.optogate.com/html/phasee.html> which is about 110 ukp. We > couldn't justify buying a > Phaserite way back then but it did inspire me to knock up something I named > the "in-phase". > Basically a sinewave generator (discrete transistors!) feeding a half-wave > rectifier so that only > the positive peaks come out. With a scope, a microphone and a bit of care, > it's possible to check > speaker polarity (or cable/amp/whatever polarity). The box, being small and > battery powered, still > regularly gets used for quick'n'dirty checks on systems. > > These days I'm tending to include a Raised Cosine Pulse generator in my > plugins - in code it's > easier to make RCP's with separations that are much greater than than the > pulse width which in turn > makes it easier to spot polarity on speakers. You still need to be careful to > allow for the fact > that some cross-overs use driver inversions to even responses in the > cross-over region, because this > can really confuse the issue. If used for checking microphone polarity, and > you don't have a known > unit with positive electrical out for positive pressure in, you need to use a > battery (or similar) > applied directly (but via a current limiting resistor) to the speaker > terminals to determine that > the cone is going out (increasing the pressure in the room) for positive > voltage in, before you use > the RCP generator - don't forget to use a scope to check that the pulse > polarity at the input to the > speaker is correct! > > All that having been said, a clicker is easier! I used to have one that was > given out at a trade > show (AES?? APRS?? - can't remember) as a "Free Acoustic Tester" but it > eventually collapsed on me > and I keep meaning to get a new one but, as yet, I haven't replaced it. > > Dave > > -- > These are my own views and may or may not be shared by my employer > /*********************************************************************/ > /* Dave Malham http://music.york.ac.uk/staff/research/dave-malham/ */ > /* Music Research Centre */ > /* Department of Music "http://music.york.ac.uk/"; */ > /* The University of York Phone 01904 432448 */ > /* Heslington Fax 01904 432450 */ > /* York YO10 5DD */ > /* UK 'Ambisonics - Component Imaging for Audio' */ > /* "http://www.york.ac.uk/inst/mustech/3d_audio/"; */ > /*********************************************************************/ > > -------------- next part -------------- > An HTML attachment was scrubbed... > URL: > <https://mail.music.vt.edu/mailman/private/sursound/attachments/20111010/429893f7/attachment.html> > _______________________________________________ > 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/20111010/3644162a/attachment.html> _______________________________________________ Sursound mailing list Sursound@music.vt.edu https://mail.music.vt.edu/mailman/listinfo/sursound
