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This is designed to be a simple test so we can see what happens
when we record a swept sine wave out of various Akai MPC machines.
We can gain a better understanding of the different sonic characteristics
of these machines doing this, as a separate issue from any subjective
ideas of how the machines 'sound'.
This is the simple process:
a) Load in the 2kh
- 22khz swept tone into the sampler. On some earlier samplers,
it may be difficult to do this without physically recording the
sample into the machine. Just note that this is the way it was done.
On newer machine, it should be easy to load in the pure .wav sample.
b) Play back the sample from the machine (remember to remove any
effects, EQ, filters etc)
c) Record the tone back into your system, save it, and send
it to me!
d) As a final test, you can play the test tone straight back in
thru your system to give us a rough idea of what your system sounds
like by itself. Use Cubase or another multitrack sequencer for this,
simply place the test tone on a track, play it back thru an output
of your computer / mixer / soundcard, connect a cable back from
the output to the input, and record the input. Be carefully you
don't set up a feedback loop doing this. Send this to me, along
with all info about the methods and equipment used.
This is what started me off on this test - some unsubstantiated
claims on the internet that the MPC 4000 'rolled off the bass below
120 Hz'. Since I just got a 4000, and it sounded good to me, I wanted
to know for sure what was happening. As you can see from the image
below of the swept tone from 2hz on the left to 22Khz on the right,
it is basically flat, with a tiny hf roll of, about 0.1 db, from
around 7hz up until the 20Khz cut off point (you can see this at
the end where the sample dips to a point then rises again). The
sampler managed to reproduce the 2hz tone no problem, the small
rise in the frequency response on the very low end may be due to
my mixing desk offset compensation (see below).
AKAI MPC 4000 OUTPUT FREQUENCY RESPONSE
The MPC output is at the top, the flat tone is at the bottom.
As requested, here is the MPC 4000 input (record in) frequency
response. The waveforms are lower in amplitude because there is
a DC ofset at the start of the MPC file, I think this is due to
some automatic DC ofset compensation on the MPC. Remember this test
starts at 2hz, which is almost DC anyway. The lowest note we can
hear is around 20hz. Further up the waveform, there is a tiny bulge
at around 9Khz, then a droop to 20khz with a deep cutoff that starts
a bit lower than the output conversion waveform. This waveform overall
doesn't look as good as the output waveform, sugesting that anything
sampled into the MPC 4000 using it's own converters may have slight
high frequency losses, and that using a different converter will
lead to subtley different results.
AKAI MPC 4000 INPUT (Record) FREQUENCY RESPONSE
The MPC is at the top, the flat tone is at the bottom.
This is the 'control' test, where I put the signal out of my desk
(a Yamaha 01V96) and recorded it coming directly back in. As you
can see, the Yamaha's frequency response is very flat, with a small
bump in the very low end of about 0.2dB, probably due to DC offset
compensation kicking in on the 2hz tone.
YAMAHA 01V96 OUT TO IN FREQUENCY RESPONSE
The 01V96 test is at the top, the flat tone is at the bottom.
MORE TESTS NEEDED!
I am especialy interested in the MPC 1000, MPC 3000, and MPC 60
tests, but the MPC 2500, MPC 2000, and MPC 2000XL would be great
as well. I will also accept any other tests anyone wants to do any
any other aspect of their system, especialy other samplers and other
mixing desks. Just download the test swept tone, and follow the
instructions above, then email me the results! It should take you
about 5 minutes.
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