DBG@SLACVM.SLAC.STANFORD.EDU (10/31/90)
I need a modest Public Address system for a nonprofit organization with
a modest budget, just something to boost the voice of a quiet president
a bit. Budget limit $300 max.
I thought a nice solution might be a boombox with a mike input, and
bought on trial a Panasonic RX-DS20 with CD player and tape and FM radio,
figuring it could also provide background music for parties etc.
This might work, though I wonder if the 5-inch speakers are up to it.
It seems loud enough but I think I sense a resonance at a few hundred
Hertz which might be annoying, and perhaps it won't be loud enough in
a room with a hundred people. (price $199)
For a microphone, I thought the ideal would be a wireless mike which
broadcasts to the FM radio, and bought (on trial) a Radio Shack 33-1076.
The first one seemed hopelessly distorted, so I exchanged it for a
second which is better but still useless. (price $20)
There seem to be a few problems with this approach. The RS mikes seem to
be no-fidelity. (Are there mikes of usable quality which broadcast FM?)
One part of the problem is the Panasonic receiver is digitally tuned,
and it is very very hard to tune the mike accurately. However, transmitting
to an analog-tuned radio also results in awful fidelity, so that isn't
the whole problem. Second, the FM band is pretty full here so it may be
hard to avoid interference.
Does anyone have relevant experience with PA systems for modest-size
groups? We don't want a bull-horn, and don't need rock-band volume, but
want good fidelity and enough volume to handle say 100 people inside a
community-center-type room (typically hard walls, tile floor, acoustic
tile ceiling).
Is there a convenient clip-on mike with wire connections if the FM
broadcast scheme fails?
Any suggestions for an alternate system? We could do without the
CD player and tape and radio if necessary.
-- David B. Gustavson, Computation Research Group, SLAC, POB 4349 MS 88,
Stanford, CA 94309 tel (415)926-2863 fax (415)961-3530
-- What the world needs next is a Scalable Coherent Interface!
-- Any opinions expressed are mine and not necessarily those
of SLAC, Stanford University or the Department of Energy.mm@lectroid.sw.stratus.com (Mike Mahler) (10/31/90)
How about a cheap (used even) CB radio that has a PA switch on it? You'd just need a speaker and power supply (both cheap also) then...
gary@ke4zv.UUCP (Gary Coffman) (11/01/90)
In article <90303.202207DBG@SLACVM.SLAC.STANFORD.EDU> DBG@SLACVM.SLAC.STANFORD.EDU writes: > >Does anyone have relevant experience with PA systems for modest-size >groups? We don't want a bull-horn, and don't need rock-band volume, but >want good fidelity and enough volume to handle say 100 people inside a >community-center-type room (typically hard walls, tile floor, acoustic >tile ceiling). There are numerous tradeoffs in a PA system. The fidelity/cost tradeoff is one of the toughest. First let me urge you to avoid wireless microphones if possible. Good wireless systems with diversity receivers and using crystal controlled clear frequencies (requiring a license) are very expensive. Nothing less is satisfactory except in rare conditions. Without diversity reception you will have null zones with sudden fades and odd noises. Without crystal control you will have drift problems similar to those you described. Expect to pay upwards of $1000 for a decent wireless microphone system. If possible use a podium mounted stick mic such as an Electro Voice EV635, this is the best all around microphone you can buy. It's extremely rugged, you can drive nails with it, and it has good voice fidelity. Most broadcasters use it. If the speaker must move about, use a lapel mic like a Sony ECM50 or let him hand hold the EV. Using a hand mic properly is a skill that some speakers find difficult to master. These are professional microphones in the $50 to $90 dollar class. For a hall holding 100 people you need an amplifier of about 50 watts. With very efficent speakers you can get away with 20 watts. You will need an equalizer to balance the system and prevent feedback. Bogen makes a suitable amp for about $150. If the PA is to be a permanant installation, ceiling mounted speakers sprinkled about the hall are best. No one gets blasted and people in the back can hear clearly. Cost will be about $10 each for 5 inch ceiling mount speakers and 70 volt line transformers. Otherwise you will need two or three floor standing speaker cabinets. If you want good fidelity, and you do else feedback becomes very difficult to control, these can be very expensive. Expect to pay at least $150 each for floor standing speakers. You can make suitable speakers yourself out of plywood and speaker components by EV or even Radio Shack. Cost about $50 each. An empty hall and one containing 100 people have very different acoustics. Try to get some volunteers to sit in the seats while you are equalizing the system. Otherwise you will be unpleasantly surprised. Also a system that sounds plenty loud in an empty hall will be inadequate when sound absorbing bodies are present. Try to do all your testing with the hall filled. So with care you can put together a system for around $300 that will do a fine job. Get to know your local sound reinforcement technicians and the distributors where they shop. You'll learn a lot. Gary KE4ZV