Owner's Manual

Wiring Signal to the Subwoofer

The input terminal is on the rear of the subwoofer and is covered by a hinged door. Open the door to expose the screw

terminals. There are four sets of screw terminals arranged in positive/negative pairs for parallel wiring. One pair is labeled

for input (receive signal) and the other pair is labeled for output (pass signal to next device). But be sure that the wiring is

consistent and paired properly.

The terminals are designed to accept wiring between 18 AWG (1.02 mm) and 12 AWG (2.053). Use a #2 Phillips-head screw

driver to loosen the terminal screw. Strip the insulation for the signal wire so that approximately 3/4 in (20 mm) of bare wire

is exposed. Place the bare wire under the screw down plate and retighten the screw as tightly as possible with a manual

screw driver.

The input and output pairs are parallel. The output terminals will pass exactly what is presented at the input terminals. If low

impedance full range audio signal is presented at the input (it is recommended that the subwoofer’s internal low pass ﬁlter

be used in this instance) then low impedance full range audio will be passed to the next device wired to the parallel output

of the AD-S28Tw. If high impedance 70V or 100V signal is presented at the input, then high impedance 70V or 100V signal

will be passed to the next device wired to the parallel output of the AD-S28Tw. If an external low pass ﬁlter is used and only

low passed signal is presented at the input, then only low passed audio will go to the next device wired to the parallel output

of the device.

Using 70V or 100V Drive for Distributed Audio Systems

High impedance 70V or 100V drive allows for a typically larger number of loudspeakers to be wired to one ampliﬁer output

and allows smaller wire gauge to be used over longer runs with less loss. When using high impedance drive, the internal

transformer on the AD-S28Tw MUST be engaged. To do this, rotate the tap selector switch so that it is aligned with one of

the four (three for 100V) transformer tap settings. The tap setting on the switch selects which tap of the transformer is used

to buffer the signal and is expressed in terms of the power draw on the ampliﬁer. The larger the tap, the more output from

the subwoofer. Transformer tap settings should be considered when selecting an ampliﬁer to drive the system. A good “rule

of thumb” is that the rated power of the ampliﬁer per channel should be the minimum of all of the connected taps added

together with an additional 20% for headroom. An example:

8 Loudspeakers each tapped at 50W

50 + 50 + 50 +50 + 50 + 50 + 50 + 50 = 400 or 8 x 50 = 400

400 + 20% = 480 Use an ampliﬁer with a minimum channel power rating of 480W

Multitap 70V / 100V transformers can saturate with low frequency energy. Saturation causes analog clipping distortion of

the signal. The transformer use in the AD-S28Tw is custom designed to saturate at frequencies below the functional low

frequency range of the AD-S28Tw. It is recommended that a -6 dB, 30 Hz high pass ﬁlter be engaged to prevent saturation of

the transformer.

Any unused attachment point can be used as a safety/seismic secondary attachment. Attach an eyebolt to an available

attachment point according to the Eyebolt instructions above. Be sure to leave less than 12 in (300 mm) of slack in the

secondary attachment cable.

The safety/seismic secondary attachment must be secured to structure that is capable of supporting

the weight of the subwoofer and must be connected using load rated hardware.

Once the subwoofer is secured in position, the QSC logo can be rotated if desired. If the logo is difﬁcult to rotate the ﬁrst

time, a tool may be required. A small ﬂat-head screw driver is recommended. Gently work the tool between the logo badge

and the grille to allow rotation. Exercise care to avoid scratching the grille surface.