Boundary Gain Compensation - JAMO 250 Owner's Manual

Most of today's subwoofers have an auto on/standby feature whereby the
subwoofer switches itself on if it senses a signal and switches in standby mode
again a certain time after it has last sensed a signal. However, in movies (or
typically classical music) with relatively quiet passages the subwoofer can
switch to standby mode thereby "missing" the start of a new action packed
sequence like for example an explosion or a kettledrum. Besides the auto
on/standby mode we have therefore implemented a mode were the subwoofer
is always on.

Boundary Gain Compensation

The deep frequency response of SUB 550 and 650 grants reproduction of the
most extreme bass contents of e.g. movie soundtracks with full authority.
However, under certain circumstances such deep frequency response can
create a problem, which is why some A/V receivers/decoders feature a
Boundary Gain Compensation filter.
This filter compensates for the room influence at low frequencies, as any room
amplifies the lowest frequencies.
The magnitude of the room's amplification 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 bass level from approx. 60 Hz and increasing
downwards.
In the range between 20-30Hz it easily peaks up to 10dB!
At first impression this could sound really impressive, but especially when
listening to music the sound can be "boomy" and rather annoying.
Therefore, the SUB 550 and 650 have a quite unique feature:
Boundary Gain Compensation is built into the amplifiers to compensate for
the room influence at low frequencies.
With the usual adjustment
such as cut-off
level it will be impossible to obtain a
linear in-room
However Boundary Gain Compensation
will allow an additional fine tuning
possibility which will compensate non
optimal placement of the listening
position and
properties in most rooms.
possibilities
frequency and volume
frequency response.
"difficult" acoustic
Off Off
On On
Illustration of how the Boundary Gain
Compensation technology works. Note that in both
off positions the peak around 20-30 Hz is much
higher than 40-100 Hz, whereas in the on position
the bass response is more linear.
Off Off