Getting The Bass Sound You Want - Orban Optimod-FM 8300 Operating Manual

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OPERATION ORBAN MODEL 8300

Getting the Bass Sound You Want

Probably the most frequently asked question we get regarding 8300 setup is "How
do I get a (such-and-such) bass sound?" It seems that individual preference varies in
this area more than anywhere else.
There are no magic formulas. The 8300 has extremely versatile controls affecting
bass sound and will allow you to get almost any sound you want as long as that
sound respects the laws of physics—or, in this case, the laws of psychoacoustics.
The ear is far less sensitive to bass than to midrange sounds. You can see this for
yourself by examining the classic Fletcher-Munson "equal-loudness" curves. This
means that if you want robust bass, this will take up a great deal of room in your
modulation waveform. This room could otherwise be used for midrange, where far
smaller amounts of energy yield the same amount of loudness. Accordingly, there is
an important tradeoff between loudness and bass—if you want more bass, you will
have to accept either less loudness or noticeably more distortion, which occurs when
the bass waveforms push the midrange and high frequency material into the 8300's
final clipper.
There is one psychoacoustic trick you can use to create more apparent bass while us-
ing modulation headroom efficiently. For hundreds of years, pipe organ makers
have tricked the ear into hearing non-existent fundamental tones (which would re-
quire huge, expensive pipes) by replacing them with several, smaller pipes tuned to
the lower harmonics of the missing fundamental. In the 8300, you can use the bass
clipper to make harmonic distortion for this purpose. As explained above, the bass
clipper has three settings—S , M , H —that determine the amount of
OFT EDIUM AND ARD
distortion the clipper makes when its clips bands 1 and 2. S provides the purest
OFT
sound, but M and H create progressively more distortion on bass. Because
EDIUM ARD
H can make noticeable IM distortion, the factory programmers prefer M for
ARD EDIUM
most presets.
However, if you are willing to trade off IM distortion against bass punch, then you
could also use H . H is particularly effective in increasing bass punch because it
ARD ARD
flattops bass transients and this allows the waveform to accommodate fundamen-
tals that have a larger peak level (by up to 2 dB) than the peak level of the flat-top.
(The fundamental of a square wave has a peak level 2.1 dB higher than the peak
level of the square wave.) In essence, by doing this, your bass fundamentals can ex-
ceed 100% modulation without having the composite stereo waveform itself exceed
this level. In H mode, you can use the B control to determine if the
C S
ARD ASS LIP HAPE
knee of the transfer curve is more abrupt (B C S set toward 0) or gentle
ASS LIP HAPE
(B set toward 10). Abrupt curves make more high-order harmonic dis-
C S
ASS LIP HAPE
tortion but less IM distortion; gentle curves make more IM and low-order harmonic
distortion.
The attack time of the band 1 compressor also affects bass punch by determining
the amount of bass transient material that is allowed to pass through the compres-
sor before the attack clamps down the rest of the waveform. Any transient that
passes through the band 1 compressor will hit the bass clipper, so slower attack
times on band 1 will increase bass punch at the expense of distortion (particularly on