Actually, a square or rectangular decoder's outputs are such that if all
four outputs are mixed together in equal amounts, the directional
components (X and Y) will cancel out automatically leaving just the W -
which is generally what would be sent to the sub...
Dave
On 21 October 2013 01:11, Marc Lavallée <m...@hacklava.net> wrote:
> Matthew Palmer <palme...@mymail.vcu.edu> a écrit :
> > I'm wondering if it (4 sets of Logitechs) can give me 3d
> > gratification for a little over $200. I know I'm definitely
> > sacrificing quality but it will take me ages to save up for a proper
> > set-up.
> > I don't understand what kind of amplifier would be needed though.
>
> Yes! 4 small speakers with one sub are enough as a starting point:
> I suggest reading "Localization in Horizontal-Only Ambisonic Systems" :
> http://www.ai.sri.com/ajh/ambisonics/BLaH1.pdf
>
> Use a square or rectangular configuration, and drive the sub with the W
> ambisonic channel; you can use a multimedia 5.1 kit (with integrated
> amplifiers), but the sub should be driven separately, not by a mix of
> the 4 decoded speaker channels (that's my comprehension).
> For un-amplified speakers, you can use cheap D-class amps.
>
> > I don't fully understand what cross-over frequency is (it sounds
> > obvious though) but maybe by reducing the center channels from the
> > set-up , I'd reduce the amount that is happening.
>
> I would not use the centre channel; there are experimental 5.1 decoders
> but I never tried. The cross-over frequency is between the sub-woofer
> and the satellites. Ambisonics works well at low frequencies in small
> rooms, at least down to the Schroeder frequency (usually around 150Hz,
> depending on your room size and acoustic treatment). That's why 300Hz
> is a bit high, but it's not catastrophic.
>
> Ambisonics with height is possible with a "3D7.1" configuration (using
> a 7.1 speaker kit). I yet have to try it.
>
> --
> Marc
>
> > On Sun, Oct 20, 2013 at 7:12 PM, Charlie Richmond
> > <charlie....@gmail.com>wrote:
> >
> > > On Sun, Oct 20, 2013 at 3:59 PM, Marc Lavallée <m...@hacklava.net>
> > > wrote:
> > >
> > > >
> > > > What matters is rigidity; if a plastic enclosure is rigid
> > > > enough (for its size), then it would sound the same than a hard
> > > > wood enclosure. In the specific case of the Z506 model from
> > > > Logitech, wooden enclosures for the satellites would make no
> > > > difference; the drivers, the amps, and the enclosures are too
> > > > small to shake. Only the sub-woofer enclosure is made of MDF, for
> > > > a reason.
> > > >
> > > > So, why not using the Z506 5.1 kit from Logitech? "Multimedia"
> > > > speakers are primarily designed as computer accessories; some are
> > > > probably well made, excluding the one in the MoMA's permanent
> > > > collection (unless aesthetic is the most important criteria). I
> > > > wouldn't trust its sound quality; it's a bit small unless the
> > > > listening distance is less than 2 meters, the centre speaker does
> > > > not match the four other satellites, the centre speaker have 2
> > > > mids and the satellites have one mid and one tweeter, and the
> > > > cross-over frequency for the sub-woofer is probably near 300Hz,
> > > > which is a bit too high. For Ambisonics, I believe that better
> > > > quality full-range or coaxial speakers, all matched, should be
> > > > preferred.
> > > >
> > > > I would only such use small multimedia speakers for a very compact
> > > > periphonic installation, along with 4 to 8 small sub-woofers for a
> > > > supplemental horizontal or periphonic low frequency decoder.
> > > >
> > >
> > > Agreed. That said, the Logitech self powered systems are generally
> > > extremely well made and sound very good, imho.
> > >
> > > C-)
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--
--
As of 1st October 2012, I have retired from the University.
These are my own views and may or may not be shared by the University
Dave Malham
Honorary Fellow, Department of Music
The University of York
York YO10 5DD
UK
'Ambisonics - Component Imaging for Audio'
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