JAMO C 80 SUR, Brochure

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frequency and so is the negative feedback. Consequently, the woofer receives less
power in this area and, when combined with equalization the frequency response
reaches down to an impressive 20Hz (-6dB).
It is possible to make a subwoofer this size reach 20Hz just with pre-fi ltering/
equalizing, but that would create severe timing problems. In practice, this would
be heard as the subwoofer constantly “rumbling” – i.e. not able to start and stop
correctly. This might sound quite impressive initially, especially when listening to
soundtracks with a lot of explosions etc. Ultimately, however, it is also the reason
why many audiophiles prefer to turn off the subwoofer when listening to music - it
simply sounds annoying no matter how low you adjust the subwoofer level.
Combining a powerful amplifi er with MFB makes for a bass reproduction that’s
deep, precise and detailed.
Variable Boundary Gain Compensation.
Reaching down to 20Hz grants reproduction of the extreme bass content of e.g.
movie soundtracks with full authority.
However, in certain environments this can create a problem, which is why some A/V
receivers/decoders feature a Boundary Gain Compensation fi lter.
This fi lter compensates for the room infl uence at low frequencies, as any room am-
plifi es the lowest frequencies.
The magnitude of the room’s amplifi cation depends on the actual room and where
you are positioned – normally it increases the closer you get to a wall, which also
means that the problem gets worse the smaller the room.
This can result in too high a bass level from approx. 60Hz and increasing down-
wards. In the range between 20-30Hz it can easily cause peaks of up to 10dB!
On fi rst impression this could sound really impressive but the sound will rapidly
seem rather boomy, especially when listening to music, and ultimately it’ll just
sound very annoying.
To compensate for that, the C 80 SUB has a quite unique feature:
Variable Boundary Gain Compensation is built into the C 80 SUB to compensate for
a room’s infl uence at low frequencies.
If you only employ the usual adjustment options, such as cut-off frequency
and volume level, it will be impossible to obtain a linear in-room frequency re-
sponse. Variable Boundary Gain Compensation, however, allows an extra de-
gree of fi ne tuning which will compensate non-optimal location of the listen-
ing position and any “diffi cult” acoustic properties encountered in a room.
All the controls (level, phase, cut off frequency, boundary gain and auto/on/off ) are
placed on the front of the C 80 SUB, elegantly integrated into the design so that