Have you ever booked a speaker who was absolutely perfect for your meeting or conference? You know, the one who is easy to work with before the event, who arrives well ahead of your event to save you the stress of wondering where he is, who captures your attendees’ attention from the first moment and holds them on the edge of their seats until the end, and who joyfully greets every last person who lines up after the session. The perfect speaker is also the one who continues to impress you by sending an invoice that shows her necessary expenses for your event were kept to a minimum. And most importantly: the perfect speaker leaves you, the meeting organizer, looking like a hero!
The names and faces of a couple of your all-time favorite speakers are probably coming to mind right now http://itsnews.co.uk/ . These are speakers who were a pleasure to work with from start to finish, and who allowed you to focus on the 101 other ingredients of a successful event because you trusted that the speakers were on their game.
Okay, enough reminiscing. The question now is, how do you go about finding him or her for your next event? Is it purely a matter of chance that you make the magical selection or can you purposely find the “home run” speaker for your next event?
This is ultimately easy, but before explaining the process I feel it is necessary to provide a warning. Multiple sets of speakers usually can not be hooked directly to a standard audio amplifier without some sort of impedance matching device. This is in reference to those persons whom might want to run speakers in several rooms at the same time (distributed audio). If several sets of speakers are run from one set of speaker terminals the amplifier will usually overheat and shut down, and may blow the output stage (see footnote 1). These remarks do not apply to PA style amplifiers with 25 or 70 volt outputs, which require special speakers with transformers.
The correct solution is to use either an impedance matching speaker selector with the protection enabled, or use impedance matching in wall volume controls. Notice the underline in the sentence above. This is because most speaker selectors are made with a dangerous feature: a button, right in front, to disable the protection. If the switch was in back to prevent accidental deactivation of the speaker protection it would be much better. If the protection is accidentally switched off while running multiple pairs of speakers the amplifier will shut down, may blow output fuses, and very well may damage the output stage of the amplifier. There are really only 2 reasons to turn this switch off, the most relevant being that impedance matching volume controls are being used on ALL pairs of speakers. The other reason would be if only one pair of speakers are being run, making impedance matching unnecessary. In this event, though, leaving the protection switched in will make only a very small difference to the sound, so why not leave it on?
Remember it this way: only put one speaker per pair of terminals (usually red and black) on the amplifier. Do not try to use a surround amp to feed several rooms with one room on the center, one room on the rear surrounds etc. This is due to the way a surround receiver distributes the sound as you may end up with only the voice in one room and only the music in another! The correct hookup for a surround receiver puts surround sound in the main room and sound from the left and right main speakers is distributed. My recommendation for hooking up a surround receiver is as follows. Run the speaker selector from the front left and front right outputs on the amplifier. Hook your front left & right speakers to the first speaker switch on the speaker selector. You will need to re-balance your surround system by running the pink noise test as the speaker selector will decrease the output to the left and right speakers by a small amount. This allows running the main speakers & the other speakers connected to the speaker selector without one set being louder than the others. If your speaker selector has volume controls, you need to make sure when you use your surround system for movies the volume control is at the same setting it was when doing the pink noise test. You may hook the speaker selector to the ‘b’ speaker switch on the amplifier if speaker volume balance between your main left & right speakers and the rest of the speakers is not an issue.
Another variation is amplifiers with a direct speaker output for zone 2, 3, etc. These are set up to drive 1 pair of speakers, and must be used with impedance matching if more pairs are to be used. The zone outputs allow a second (or third etc) source, for example CD in one room and radio in another.