This is brief description of my project. Full
story is in Finnish here.
I visited Helsinki Hifi Fair in 2006. There was new Genelec
DSP speakers. I got interested, since I had some DSP background. Price
of the Genelecs was too high, and I decided to build my own DSP
speakers. I had done some school exercises with Analog devices Ez-Kits,
so I bought the latest model ADSP-21369.
Price of Genelec 8250 was 1500€ per piece, so I wanted to
limit the budget of the whole project to 1500€. So I had about
1000€ for the speaker elements and the cabinet. I ended
up Seas Excel (
W18EX001 ja T25CF002 ) elements, and AW-10 cabinet
kit. AW kits are quite well known here in Finland, and they have
usually a horn (waveguide?) loaded tweeter. I though that waveguide is
necessary, since steep crossover filters might cause problems to
directivity pattern of the speakers. Thats what I had been
learning when reading the local audio forums.
Some pictures during the construction.
Some final pictures. Painting of the cabinets failed somewhat...
The design process of the crossover filters was a long
story. In short, my system looks now like
this and crossover filters are designed like
this.
The room correction filters were calculated using drc.
Sharc development board
does perfectly both the crossover filters & some room
correction. After it has been flashed, it is robust and boots up in
less than 1 second. The board has served 2 years in our living room
set, and spouce has not been complaining complexity of use (actually
there is no other
features than
on/off). No visible I/O delay while watching TV.
Still there are few
cons:
The room
correction FIR filter length is limited to 1024taps, and therefore the
correction in bass tones is nil. Usually the bass octaves are in
highest need for room correction. Fortunately my wooden house has
almost none room modes below 100Hz. I do not have talent or motivation
to implement FFT (overlap&add) style filters.
The licence
restictions of VisualDSP (the only development tool) are annoying (but
they are not stopping my development).
Anyway, in my next
project I will use PC+brutefir platform. Next
project will be multichannel (5.1), so PC HW will become
cheaper per a channel.
The project description
is only in finnish at the moment.
