Distortion, impedance & the 10:1 rule.

PROBLEM: I am troubleshooting an audio system installation in a large conference room that can be divided into three separate rooms. Each room has a dedicated powered mixer with distributed ceiling speakers and the source equipment is in a roll around portable rack. The idea obviously is that the customer can take the source equipment to, whichever room is in need or it can be shared between any combinations of the three. The only problem is if one of the powered mixers is turned off because a room is not in use it causes distortion in the other areas. From what I can tell who ever did the original installation has simply paralleled the sources to all three mixers. How can we alleviate this distortion.

Speakers; A cluster of polarity desparity.

PROBLEM: We just installed two speakers in a small auditorium. They are hung in a tight cluster at about a thirty-degree angle to each other. The problem is that we are experiencing drastic phase cancellation right down the center of the auditorium. It starts as an approximately three foot wide area and slowly expands to about nine feet and the rear of the auditorium. With an SPL meter we are reading about a 12-15db difference in and out of the area of cancellation.

Powered stage monitors make me buzz…

PROBLEM: We are using powered stage monitors and we are experiencing a loud buzz. We’ve switched cables and speakers to no avail. The monitors are fed from the FOH up in the organ loft. Are we picking up noise somewhere along the way?

SOLUTION: The stage and the main equipment location in the organ loft are probably not on the same circuit. This is causing two problems;