AVS Forum Special Member
Join Date: Dec 2007
Location: Southern California
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100 watts is the maximum rating of the transformer. You will seldom if ever run the system at full power, so the transformers are really overrated.
The tap you choose on each transformer is determined by the relative volume you want from each speaker.
For example, if you decide that speaker B needs to be a bit less loud than speaker A, then you might select the 100W tap to use for A on its transformer, and the 50 watt tap to use for speaker B on its transformer.
I very much doubt that you need a 600 watt amplifier, but if you want to be bullet-proof, it couldn't hurt. 300 watts is probably fine.
If you use the JBL JRX112M speakers I mentioned, I would mount them on the end walls about two feet below the ceiling facing straight into the room, or maybe tilted downward VERY slightly. This will give the most effective dispersion, with minimum absorbtion by keeping the sound projected HORIZONTALLY above the people and furnishings, so that it reaches their EARS with less attenuation.
I think four of them will be all you need; two at each end of the space. Facing speakers straight down, vertically, gives very poor sound dispersion; the power is absorbed by the bodies and the floor and does not travel far from the speaker. You really do not want to do that.
As a matter of fact, one of the reasons for using down-facing speakers in an office or other PA system is that it limits the sound from a given speaker to a small area, and then you can avoid disturbing other nearby areas too much by strategic placement. If you go to a restaurant or other venue with ceiling speakers, you will observe that you don't hear them worth a damn unless you are almost right under them. Think about that...lol.
I would use at least 12 speakers if they were going to be downward-facing speakers. You will need them.