User manual ALTEC LANSING 291-16L HF DRIVER

[. . . ] REFER REPLACEMENT TO QUALIFIED SERVICE PERSONNEL. The exclamation point within an eqilateral triangle is intended to alert the user to the presence of important operating and maintenance instructions in the literature accompanying the device. WARNING: THIS APPARATUS MUST BE EARTHED 3 Operating Manual -4048A digital signal processor & 1. INTRODUCTION Your new 4048A is a flexible four input/eight output digital signal processor capable of precise control of a broad range of audio functions. Because it has no user controls, it is ideal for applications where real-time changes are unlikely or when tamper-proof security is required. All adjustments are made using Altec Lansing MaestroTM software for WindowsTM. [. . . ] It is well worth the time becoming proficient with parametric EQ filters, as they offer the best solution to many EQ problems. Narrow (Low) Bandwidth Wide (High) Bandwidth +20dB +10dB 0dB -10dB -20dB -30dB 20Hz 200Hz 2KHz 20KHz 4048A Parametric Filters 4048A parametric filters have a boost/cut range of +15dB to -30dB. There is more cut than boost because one of the more common uses for parametric filters is to dramatically cut, or "notch out", very narrow frequencies (low bandwidth) in order to eliminate system feedback problems. Every instance of a parametric EQ filter has a center frequency selected. The factory default is 1kHz, but each filter's center frequency is adjustable from 19. 7Hz to 21. 9kHz in 1/96 octave steps. Carefully sweeping a narrow bandwidth filter through a problem feedback area, with just a slight boost, is a quick way to find the exact frequency causing trouble. Once the offensive frequency has been found, cut the filter's level, and then adjust the bandwidth as narrow as possible while still eliminating the feedback problem. Bandwidth is adjustable from about 1/64 octave to four octaves, and the lower the bandwidth, the less audible the filter action will be. Finding the problem frequency is relatively easy, but finding the best combination of cut and bandwidth takes a little practice. Again, it is well worth the time getting comfortable with the notching procedure, so that problems can be quickly addressed with a sufficient but minimal amount of correction. 11 Operating Manual -4048A digital signal processor Shelving EQ filters: 1st order filters use a gentle 6dB per octave slope, while 2nd order filters use a 12dB per octave slope for more a pronounced boost or cut. Low shelving filters have a frequency range from 19. 7Hz through 2kHz, and the high shelving filters range from 3. 886kHz through 21. 9kHz. Shelving filters are most useful as 1st Order Filter broad tone controls to boost or cut the high 2nd Order Filter Low Shelf High Shelf end or low end of an audio signal's frequency +20dB content. When a Butterworth HPF and LPF of the same crossover frequency are summed, the combined response is always +3dB. With 12dB per octave Butterworth crossover filters, one of the outputs must be inverted or else the combined response will result in a large notch at the crossover frequency. Bessel These filters, as implemented on the 4048A, are always -3dB at the displayed crossover frequency. Bessel filters are used because they have a maximally flat group delay. Stated another way, Bessel filters have the most linear phase response. When a Bessel HPF and LPF of the same crossover frequency are summed, the combined response is +3dB for 12dB/oct and 18dB/oct Bessel filters, and -3dB for 24dB/oct Bessel filters. One of the outputs must be inverted when using either 12dB/oct or 18dB/oct Bessel crossover filters or else the combined response will have a large notch. Linkwitz-Riley The 12 dB/oct and 24dB/oct Linkwitz-Riley filters individually are always -6dB at the displayed crossover frequency, however the 18dB/oct Linkwitz filters individually are always -3dB at the displayed crossover frequency. The reason for this is that Linkwitz-Riley filters are defined in terms of performance criterion on the summing of two adjacent crossover HPF and LPF filters, rather than defined in terms of the pole-zero characteristics of individual filters. The 18dB/oct Linkwitz-Riley individually are 18dB/oct Butterworth filters in that they have Butterworth polezero characteristics and also satisfy the criterion for Linkwitz-Riley filters. When a Linkwitz-Riley HPF and LPF of the same displayed crossover frequency are summed, the combined response is always flat. [. . . ] TROUBLESHOOTING 9. 1 Audio Troubleshooting Tips 1. ) No power - Is the detachable AC cord fully plugged in?2. ) Software controls don't work - Is the RS-232 cable properly installed to the PC?If set to <Lock Processor>, then unit is "view only" and controls cannot be changed. Check the selected audio source(s) for each output, making sure there is signal applied to the designated input(s). [. . . ]