| Chronology | Current Month | Current Thread | Current Date |
| [Year List] [Month List (current year)] | [Date Index] [Thread Index] | [Thread Prev] [Thread Next] | [Date Prev] [Date Next] |
air
An example of this is putting isolators under speakers to prevent
coloration
due to interactions. But most of the interactions are mediated by the
which carries far more energy, so it is a 3rd order effect. Andis
interaction
through the floor is impossible on a concrete slab floor. Also imaging
conveyed by the first signal to arrive at the ear and the interactionspeakers
through the floor will be a delayed signal which contributes nothing to
imaging. So isolators are worthless under speakers! But raising
slightly can dramatically change the sound and reduce some roomresonances
so using cheap wooden shims would probably produce the same effect but
would
not look as nice. Technobabble is used to sell a cheap fix at an
expensive
price.
Imaging can, I think, be influenced by delayed signals--if such signals
end
up out of phase with the original. Bob Carver used this in a remarkable
$300 add-on that he called Sonic Holography. Here is the basic idea.
When
you listen to a sound source directly in front of you, you get the same
signal in each ear, at the same time, and at the same loudness. For
sources
to your right or left, the signal arrives at your ears at slightly
different
times and louder in one ear than the other. This latter works fine for
stereo speakers, but the 'centered' signal has a problem. If you put the
same signal in each speaker, the sound does arrive at each ear at the same
time and with the same intensity--just like a live source--BUT a few
microseconds later, the left speaker signal gets to your right ear and the
right speaker signal gets to your left ear--each somewhat diminished
because
your head is in the way. This is enough for our brain to say that
something
is not quite right. The audible effect is that stereo speakers tend to
produce a very two dimensional sound stage--right, left, center, but
basically seemingly all from the same distance. What Carver did was
produce
a box that took the some of the signal from one speaker, delay it a few
microsecond, put it out of phase, and then sent it to the other speaker.
If
one sits midway between the speakers, then this effectively 'erases' the
cross-over signal--the one from the left speaker to the right ear. If
done
only with those signals that would be common to both speakers, the result
is
to 'fix' the 'two speaker doesn't produce a proper centered signal'
problem.
Audibly the effect can be spectacular. Sound sources are much more
localized in space and seem to come from close, far, right, left, (even
right of the right speaker and left of the left speaker). Some recordings
are quite interesting when heard on this system. Despite being a 'studio'
recording, the original Jesus Christ Superstar album sounds like a stage
play--with voices well positioned and moving about the stage in a
realistic
way. The point is, this is done with delayed signals--they can effect
imaging. Of course having your speakers out of phase can do so as well--
but
now you get a diffuse sound with almost no localization (in early 4
speaker
setups, one often did this intentionally with the rear channel setup to
increase the spaciousness of the sound.)