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A stereo setup with the LXmini requires four power
amplifiers. For the two woofers I suggest a range from 50 W to 200 W max per
channel into 8 ohm. The frequency range above the 800 Hz crossover to the
mid/tweeter requires considerably less power as I have deduced from maximum
voltage measurements across the driver terminals. The maximum that I observed
occasionally would correspond to 20 W into 8 ohm, but since the driver is 4 ohm
the equivalent power is 40 W for the mid/tweeter.
For development of the LXmini, and because I had it on
hand, I have
used the Emotiva UPA-500, which is a 5-channel, 70 W/channel amplifier with THD
< 0.01%. The amplifier costs $350 and its performance-to-price ratio is
amazing. It is no longer available. A pair of Emotiva MINI X -
A100 might be an alternative.
I know that there can be sonic and imaging differences
between different amplifier designs, even when their frequency responses into
the load are identical. The UPA-500 with the LXmini sounds neutral and
spatially detailed over the whole frequency range, immediately and in long-term
listing. I also have listened to different amplifiers and front ends through the
LXmini and find the speakers revealing of sonic differences in equipment. Thus,
if you like to play this audiophile game - and often endless search - the LXmini
is a speaker that can make it fun and rewarding because it tells you right away
if you have come closer or moved away from "reality". Stereo is an
illusion, a mental construct of an acoustic scene, which the recording engineer
has sampled with n-microphones and processed. The only connection to reality is
your accumulated auditory memory of live acoustic events. The 3D rendering,
which the LXmini delivers to your
ear/brain perceptual apparatus from the cues in a well done recording, can be like a convincing magic show.
The difference in power requirements for woofer vs.
mid/tweeter opens the door to Class-A power amplifiers for the higher
frequencies, where amplifier differences are usually noticed first. But the
voltage gain of such amplifier must be made identical to the woofer amplifier's
gain in order to stay within the dynamic range of the mini DSP 2x4. Most likely
this requires a pre-amplification stage at the power amplifier input. Also, the
amplifier output impedance should be <0.5 ohm, i.e. small compared to the
rising voice coil impedance, in order not to affect the frequency response of
the speaker.
The LM3886 based amplifiers on the PLUTO pcb board are
another option. They actually measure quite a bit better than the Emotiva
UPA-500 or MINI X-A100 for low distortion at 1 W and 100 mW levels. I give some
guidance on the LXmini Owner Support page on how to adapt existing PLUTO
amplifier modules
for LXmini use, expecting some electronic know-how from the builder for
completing such project.
(The UPA-500 is no longer available. A-500 is the new
economic 5-ch amplifier from Emotiva. F:B:)
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