ARENDAL 1723, Handbook, Page: 26 / 57

reduction in distortion for a given volume setting. Spread
the subwoofers further apart, and that advantage halves
to closer to 3dB. 3dB is still a useful output, but separation
makes a number of factors more diffi cult to deal with.
For one, rooms are rarely acoustically symmetrical.
Even if all of the walls are the same size and structure,
it’s unlikely that every piece of furniture in the room is
a mirror image and it all counts - Each subwoofer will
have a different in-room response and require a different
EQ solution. Also, whilst each subwoofer will be EQable,
different listening positions will have a different path
length to each subwoofer. You will just have made it harder
for your AVR or Processor to achieve an EQ solution as
now, not only is it fi ghting the room and it’s dimensions,
but also the changing dimension of listener to subwoofer
distance to not just one subwoofer, but two.
It is arguable that in the case of stereo programme, stereo
bass from two equally distributed subwoofers should be
superior. However, the ear/brain makes virtually no use
of the sub 80Hz subwoofer bass wavelengths to form a
believable stereo image and very few recordings actually
mix the bass into different channels - It is nearly always
summed into an equal mono signal. In acoustic recordings
where a double bass may have been recorded in real
space (as an example) it’s still the frequencies above the
normal 80Hz crossover that carry all of the directional
information. Thus, one source of better bass that serves all
channels, is the better overall solution, for more listening
positions.
But you mentioned stacking the two subs?
This comes back to the room and integrating the
subwoofers within it. In all practical terms, the raw bass
performance of the two subwoofers sitting next to each
other across the corner will be the same as two stacked, so
why risk slipping a disk trying to lift one up?
Basically, it’s an extension of working with the room in
the way the corner position does, with a couple of added
benefi ts.
If there is one dimension that corner placement (or all
other placements for that matter) does not deal with,
it’s that of the fl oor to ceiling - normally somewhere in
the 2.4-2.7m region which correlates with the 60-70Hz
region. Of course, being in the corner on the fl oor has
removed the fl oor’s contribution fi rst refl ection, just as it
did with the two adjacent walls, but stacking goes further.
The subwoofer effectively act as a point source, with
a spherical wavefront, restricted by the walls and fl oor.
When you stack subwoofers, this spherical wavefront
starts to behave more like a cylinder emanating from a
line source. Stack them all the way to the ceiling to achieve
a cylindrical wavefront, you then get a phenomenon
where bass power only halves with a doubling of distance,
rather than quarters. So, perversely, you can play the full
stack quieter, for the same perceived bass at the listening
position, meaning it’s actually less intrusive in the rest
of the house. The full stack also completely removed the
fl oor and ceiling from the room mode equation, making
it by far the easiest arrangement to EQ.
Even if we rewind to having just two stacked subwoofers,
you’ve gone a long way in terms of improving all of the
possible parameters that you can. You have gained the
most you can in headroom and distortion terms. There
are no differential path lengths to make EQ diffi cult. You
are moving toward a cylindrical wavefront, simplifying EQ
and reducing time domain distortions from fi rst refl ection
from the ceiling, improving impact, texture and timing.