Parts Express - Your Speaker Building Headquarters - page 16

Speaker Building
16
1-800-338-0531
I was looking for an active system that
could be placed on a wall shelf and
connected to an Apple Airport Express
for streaming music. Luckily, I had some
small 2-way plate amplifiers lying around
from a past project. The system had to
be clean and modern looking to match
my living room décor, be no more than
10" (250mm) deep and provide big sound
from a compact package.
Driver Selection
1
Since I already had the plate amplifiers on hand, I needed some drivers that would work with the fixed 3500 Hz crossover point of the amps
and would work well in a small vented enclosure, while providing enough low end extension to be used without the subwoofer if desired.
I chose drivers from the Dayton Audio Reference Series for their quality and price. The mid-woofer is the RS100-8, the tweeter is the RS28F-4
and the subwoofer is the RSS210HF-4 that I purchased at the PE tent sale at
.
Since the plate amps have built-in electronic crossovers and
the sub plate amp has its own as well, there was no need for
any passive crossover design. I did want more control over
the sound and integration with the sub so I opted to use a
small DSP unit. A balanced version was chosen simply for the
terminal inputs so it could be placed in a custom enclosure
with rear panel connectors.
The processor is providing the crossover between the sub
and monitors. In this configuration, I am bypassing the
crossover (and level control) of the sub plate amp. This allows
for finer control of the frequency and level.
In order for the small mid-woofer to extend lower and provide
more output with less distortion, the DSP provides a high
pass filter on the monitor outputs to free the small 4" driver
from bass duties below 70 Hz.
A few EQ filters were also used to correct some frequency
response anomalies.
The 2-way full-range plate amplifiers used are very similar to the older Dayton Audio MCA2258 Bi-Amplifiers. My version has a fixed 3500 Hz
4th order crossover (24 dB/octave), quality polypropylene and polystyrene capacitors, gold plated RCA input jack. THD is 0.03%, S/N ratio
is 90 dB and power output is 40W @ 8
for the woofer and 30W @ 4
for the tweeter.
The sub plate amp is the Yung SD200, a compact and powerful Class D amplifier, providing 200W @ 4
to the subwoofer. The overall output of
the sub/amp combo allows for extra headroom when using the DSP to extend the low end response, while still providing plenty of output when
matched to the monitors.
Amplifier Selection
2
Crossover / DSP
3
by Michel Turcotte
Active 2.1 Speaker System with DSP
Active 2.1 Speaker System with DSP
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