Professional Sound - Indepth

Fox & Hound Sound System Optimization By JP Warren

Many of us have a Fox & Hound tone generator set or others similar such as Fluke’s Pro3000. These are great tools getting a fair share of use – especially when we encounter wiring installed by others during troubleshooting or retrofitting. Modern versions are amazingly accurate, built smart and durable, even capable of safely activating 70 V and 8 Ohm multi-driver speaker arrays while enjoying exceptional battery life. In this world of tracing wiring they are indispensable.

However, using the device for tone generation can prove problematic. Though it is sub-optimal to employ only a Fox & Hound type toner to ring-out zones, the deficiencies of doing so can be easily addressed.

First, such toners deliver only a low-output high-pass signal, therefore ignoring the main (non-tweeter) drivers; if a main driver were compromised (a 6-in. is rubbing, for instance) it would be difficult to realize this given the toner’s energy level, Q, and frequency centre. We are certainly going to notice dead tweeters, however, being the salient outlet of the energy.

No electrical ground is connected when this battery-driven device is employed, so unless we are also metering for shorts-to-ground, problems with the wiring could remain undetected.

Also, given the signal level, Q, and Hz-centre, any speakers outside the toned zone but cross-wired into that zone may not be noticed during a zone walkabout since the high frequency of the toner beams tightly and is absorbed readily. We may walk the zone and perimeter listening for speakers not meant to be in that zone, but these outliers might be missed. This could especially be the case if adjacent but physically separated (bulkhead or curtain-wall) zones are cross-wired to each other – so they are converged into one zone having two distinctly-labelled home runs – as those two amp channels would be feeding into each other as well as into the one great swollen zone.

In order to avoid all this, it must be suggested that we also tone zones with a capable power amp so music can be pumped through the system’s zones at a level nominal to a busy atmosphere and beyond. A hefty amp can also accept paralleling zones to discover if there are coverage/dispersion solutions available in the event we need to make changes to the positioning, number, or height of individual speakers early on. Of course we would also want to check for short-to-grounds before we hook up said amp.

In short, a meter and an amp should accompany our toning of zones. And of course we’d need a copy of “Crazy Train” to appease the trades so they don’t go to their truck and bring us the AC/DC CD that’s been on the floor for months. (It’s happened.)

John-Paul Warren, MES

Freelance AV Tech

GTAH, Ontario

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About Andrew King
Andrew King is the Editor-in-Chief at Professional Sound. He is also a co-host of Canadian Musician Radio and NWC Webinars’ series of free music and entertainment industry webinars.
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