user manual
TA-890
TA-890 user manual
Page 40
The typical Left to Right problem
One of the most common problems on large scale events results from the relationship
between the left and right bass stacks.
Due to the difference in distance and arrival time at any point between two point sources, in
this case bass arrays, there will inevitably be some positive addition and some negative
cancellation between sources.
A B C
D E F
The above graphs show the relationship between two point sources when separated by
different multiples of a wavelength.
The cancellations shown above are due to the phase relationship between two sources at a
given point between them. When the sources are perfectly in phase the addition between
them gives 6dB of additional gain. If, due to positioning, one of the sources is 180 degrees
out of phase complete cancellation is experienced.
To further illustrate the problem it is important to remember that since each frequency has a
different wavelength the summation and cancellation between enclosures will change at
different frequencies.
For example presume that two bass bins are spaced 11ft apart (a wavelength at 100Hz) so at
100Hz the dispersion from the 2 sources will be as figure C. At 50Hz the dispersion will be as
figure B. Similarly at 200Hz the dispersion will look like figure E.