Bose Personalized Amplification System Troubleshooting Manual page 16

Figure 10. "Heavy" Bass, total of 8 bass modules
Ideally, at low levels all bass configurations should produce the same spectral balance, and the
main difference between the "light" system and the "heavy" system should be that the "heavy"
system can produce 18dB more SPL before the limiter kicks in.
If we label the system with 2 bass modules "nominal" and assign it a relative level of 0dB, we
would have to apply the following gains to achieve equal spectral balance.
Total number
of bass modules
2
1
4
6
8
Unfortunately, the first power stand (which provides the EQ and gain for all bass signals) has no
way of knowing how many bass modules are connected to the second external power stand and
currently there is no user interface that would allow the user to specify that in any way. There-
fore, we have chosen to implement a constant drop of -6 dB whenever something is connected
to the bass send output. This will work perfectly for the first 3 cases in Table 5, but lead to exces-
sive bass in the last 2 cases. The amount of excess bass is 3.5dB for 6 bass modules and 6dB
for 8 bass modules. Given the fact that the user probably wants lot of bass in these configura-
tions, the excess bass is deemed acceptable.
THEORY OF OPERATION
External Power Stand
With 6 Bass Modules
Bass
Send
Ideal EQ Gain Actual EQ Gain Comments
0 dB
+6dB
- 6 dB
-9.5 dB
-12 dB
Table 4. Ideal and actual bass EQ gains
16
All Amps
In
0 dB
+6dB
-6 dB
-6 dB
-6 dB