Specifications

It’s useful to note the benefit of operating a powered loudspeaker system at

higher voltages (when possible). At 240V AC, current consumption is half

that of 120V AC and the resultant voltage drop for a given cable size and

length decreases by a factor of 4. This means that the cable can be four times

longer when used at 240V AC than at 120V AC. Higher voltages are

more efficient!

(1) Input Impedance and Level

The APL-10/12 speakers were designed to receive a balanced-line signal on

their 3-pin female XLR type connector. They are also equipped with a 3-pin

Male XLR output connector, labeled “looping output,” intended for the pur-

pose of daisy-chaining multiple powered speakers together on a common sig-

nal feed. These input and output connectors are hard-wired in parallel; that is

to say, no active or passive buffer exists between the two connectors, they

are simply wired in parallel. This means that the loop-through connector will

always remain functional, even if AC power is interrupted to a speaker

“upstream” of other speaker(s) on the same feed circuit.

The input impedance is 35k-ohm, active balanced, and is intended to receive

a nominal +4 dBv input level (+4 dBv = full power). Because it’s common prac-

tice to loop quite a few powered speakers together on a shared feeder cir-

cuit, care must be taken to insure that the signal source is capable of driving

the group of powered loudspeakers. For example, ten APL-12 speakers pres-

ent a 3.5k-ohm load to the signal source. This is well within the capability of

most line-level output drivers, but depending on the output impedance of the

source, some loss in level may occur. The formula to calculate such loss is:

For example, let’s say you’re driving ten APL-12 speakers with a 100-ohm

source impedance. The formula to calculate loss would then be:

NOTE: It is important to be aware of the potential losses that may occur

from combining multiple powered speakers on the same feed circuit. This is

particularly important when attempting to adjust audio levels among a large

system that employs multiple feed circuits with different numbers of pow-

ered speakers on each feed.

Audio Signals

Voltage Loss (dB) = 20

Log

[

]

(

)

Where:

Source Equipment Output Impedance

Combined Input Impedance of all APL Speakers

Note:

Unloaded Source Equipment Signal Voltage

Loaded Signal Input Voltage to APL Speakers