Appendix B:

Connections

XLR Connectors

The SRM1801 has two female XLR input jacks that accept balanced line-level signals. When connecting a balanced signal, be sure it’s wired per AES (Audio Engineering Society) standards:

Balanced XLR Connectors

XLR

Pin 1 – Shield (Ground)

Pin 2 – Hot (+)

Pin 3 – Cold (–)

You should use high-quality, shielded cable to connect the signal source to the INPUT jacks on the SRM1801.

•High quality microphone cables work well.

•Foil shielded cables are commonly used for audio wiring.

•The better the shield, the better the immunity from externally induced noise (like EMI and RFI). Route the cable away from AC power cords and outlets. These are common sources for hum in an audio signal. You can purchase quality cables from your Mackie dealer.

There are also two male XLR connectors on the SRM1801 labeled FULL RANGE and two labled HIGH PASS. These are also wired according to the AES standards listed above.

The FULL RANGE connectors allow you to connect several SRM1801’s. Simply plug the signal source (e.g., mixer output) into the SRM1801 input jack, and patch that subwoofer’s full range jack to the next subwoofer’s input jack, and so on, daisy-chaining multiple subwoofers.

There is a limit to how many you can

daisy-chain together. A general rule is

to maintain a load impedance ten times

or more than the source impedance to prevent excessive loading on the source. For example, if your mixer has an output impedance of 120 ohms, then you can daisy chain up to nine SRM1801’s. This is a load of 1222 ohms (SRM1801 input impedance=11 kohms;

9 of these in parallel=1222 ohms). Since microphones typically have a higher output impedance, you should limit daisy-chaining from a mic source to two SRM1801’s (assuming that loudspeakers are also connected to the subwoofers).

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