OK, RJ

If you have to choose just one connector to carry all the signals in a sound reinforcement system, what would it be? Only a few years ago, this would have been a difficult decision. Now it is simple. The RJ45 can handle every signal with a little adaptation. Keep you crimping tool handy, this will be the connector that brings audio, video, control and (low-voltage) power to the entire system. Thanks to the ubiquitous CAT5 cable and this universal data connector (before the digital age, signals had identity and distinction) you can even use existing cable and conduit put in place for the information systems. (Which are like sound systems but with a real budget!)

The audio industry has a long history of borrowing from the telephone industry, such as the TRS patchbay and the decibel. The RJ45 is a "registered jack" with four pairs of connections (8 wires) that has become the generic term (even when the wiring doesn't conform to the Uniform Service Ordering Code standard on which the name was originally based) for these extremely inexpensive crimp connections on both shielded (STP) and unshielded (UTP) twisted-pair data cable. However, like many connectors, there is no guarantee that the signal in the cable will be Ethernet, let alone the specific network connection you were hoping to receive. Even within the audio industry this connector has been used for proprietary networks, such as later Crown bus (Crown IQ network current loop connections), inter-device audio and control signals, other incompatible network protocols and even as a power supply connector. There are probably equipment racks where you can see all of these in use at once (but not connected to one another) even today. After all, the adoption of this connector by audio manufacturers predated our current fascination with IP networks.

Not only are these connectors carrying the signals of a number of incompatible "universal media control systems", they also carry incompatible digital audio and video signals, analogue audio and video, and mixtures of each. Nothing is too complex for this simple plastic crimp connector. Even touring sound systems will become littered with these data jacks. Streaming data (audio and video) and burst data (control) get squeezed into a cable format that is more familiar to most journeyman electricians than sound techs. Better get used to it, while you still have time to learn how to use the termination kit. Sure, fiber optic cable is will replace that old copper - some day. But now, it will probably pass through RJ45 connectors on the way to the fiber optic interface.

It's not just the esoteric gear that sports this data jack of choice; even cheap gear can be had with the fat telephone jack. In fact, if you want to save some money, convert that video signal from coax/BNC to CAT5/RJ45. Disguised as data and using the low-capacitance twisted-pairs of UTP CAT5, the signals gain the price advantage of the most widely installed signal cable available. Volume, volume, volume. That's why it is so cheap. Not something the tiny pro-audio industry can generate on its own, but piggybacked on the giant data and telecommunication industry there is some real volume. Not that they are interested in the logarithms we use to describe volume. No, they are comfortable with the big numbers that result from linear measurements, the numbers that impress their stockholders…

Ethernet connections were where the RJ45 went into widespread use. Bringing 10baseT and then 100Mps computer networks to desktop computers in every office of every high-rise office tower. Then the power of IP (internet protocol) addresses began to spread the connection to more devices, and the smart building concept took shape. Now it is possible to find everything from wall-mounted thermostats to living room lights with an IP address. The audio industry joined in and now we have a number of methods of sending audio and control signals around using Ethernet connected with the RJ45. Of course, it is not just the connector and cable. If the signal is compatible with Ethernet, all of the low-cost hubs, switchers, routers and installation infrastructure can also be used. Computer geeks may not know audio (just look at their loudspeakers!) but at least they are numerous enough to keep all the bits in stock at every electronic supplier.

If you don't have a kit to terminate CAT5 cable onto an RJ45 connector, you may not be able to connect your next sound system together. We have been assimilated. Keep your head down and "they" may not notice that you don't belong in data land. You may get sound through their cable and back into real audio gear before they check and find that your gear's IP addresses don't answer their call.

United Entertainment Media Inc.
460 Park Avenue South, 9th Floor
New York, NY, 10016
Ph. 212-378-0400
FAX 212-378-2160

page construction