picking a paging system

picking a paging system
















Most phone systems allow you to make paging announcements through speakers in the phones. But if you want to reach people in places where there are no phones, or in a noisy area, you'll need a separate paging amplifier and speakers. Most amplifiers can be connected to your phone system with an inexpensive patch cord. Some can also handle background music and a microphone.

Here are some general guidelines for choosing equipment:

WHAT KIND OF SPEAKERS?

Optimal speaker selection for each installation can depend on the purpose of the speaker (i.e. background music, emergency announcements, etc.). Selection is also affected by the size and shape of the area to be covered, noise level, and whether the speaker will be used indoors or outdoors. For commercial applications in a 70 Volt system (more below), the speaker must have a transformer mounted on it.

  • In-Ceiling Speakers – best for 8, 10 & 12 ft high drop ceilings in office environments with low noise levels. Great for background music and/or paging. Ceiling support brackets should be used with in-ceiling speakers.
  • Wall Baffle Speakers – good for when the ceiling’s height is prohibitive to speaker placement and/or speakers can not be mounted in the ceiling.
  • PA Horns – generally used in noisy environments or when large areas must be covered. In addition, most PA Horns are weatherproof and are used for outdoor applications such as loading docks, parking lots and sports fields.
  • HOW MANY SPEAKERS?

  • The industry standard for calculating the placement and number of in-ceiling speakers  is to have twice the distance from the floor to the ceiling between the placement of each speaker on the ceiling. For example, if your installation involves an 8 foot ceiling, then the speakers should be placed 16 feet apart on a square footage basis, which equals 256 ft. of ceiling area covered.
  • If the ceiling is 10 feet high, figure that one ceiling speaker can cover a radius of about 20 feet in a "normal" environment.
  • If the ceiling is higher than 12 feet, or the environment is very noisy, the coverage radius will probably be about 10 - 15 feet.
  • The math gets a little funny. You might assume that lower ceilings should require fewer speakers because the sound doesn't have to travel so far, but that's not the complete equation. Speakers in lower ceilings can't distribute their sound as broadly as speakers in higher ceilings, so low ceilings may need more -- not fewer speakers. See our chart at http://www.ablecomm.com/howmacespdoy.html
  • For wall baffle speakers, take the square footage of the area that needs coverage and divide by 600. This 600 ft. is an average estimate based on the typical side sound distribution of a wall baffle speaker (10 ft. to each side), and the typical forward sound projection outward (30 ft.).
  • PA horns should be placed at a height of 15 feet and positioned at a 60 degree angle toward the ground. PA horns should NEVER be positioned facing each other. To cover 10,000 square feet (about 100 by 100 feet) figure on one horn for a restaurant or a store, two horns for a factory assembly area or parking lot or athletic field, or four horns for a print shop or metalworking shop. For bigger areas, use more speakers.

  • It's tempting to try to increase coverage (and use fewer speakers) by increasing the volume, but this can be uncomfortable, and unhealthy, for people near a speaker.


  • HOW MUCH POWER?
     

  • Most paging speakers are very efficient, and don't need much power to reach full volume.
  • Figure on about 5 - 10 watts per speaker. A 15-watt amplifier should be fine for two or three speakers.
  • If the distance from amplifier to speaker is more than about 100 feet, provide a few more watts.
  • We recommend that you use 18-gage stranded SHIELDED speaker wire. It's near the bottom of the page.
  • Most commercial amplifiers have speaker outputs for 4/8/16 ohms, and 70 Volts.


  • ABOUT 70 VOLT SYSTEMS

    In general, 70 Volt systems are much more cost efficient than an 8 ohm speaker system when you have lots of speakers (more than about four).
     
  • 70 Volt systems are easier to design than 8 ohm speaker systems. The designer does not have to worry about keeping the impedance matched throughout their speaker system as with an 8 ohm system. 70 Volt systems can have their speakers daisy chained in parallel together without worry. Because 70 Volt speakers come with transformers, impedance is not an issue unless a very large quantity of speakers is installed together. (Use multiple wire "home runs" back to your amplifier. This will make locating problems easier by isolating individual small speaker runs.)
  • It is easy to calculate the wattage needed for your amplifier. Take the total wattage requirement of your 70 Volt speakers, or "load", and include a 20% safety buffer to get the minimum RMS wattage your amplifier should have.
  • 70 Volt systems allow you to set the volume of each individual speaker by selecting the wattage taps on the speakers for the volume needed in the specific area. The higher the wattage taps are set, the more power the speaker consumes, and the louder the speaker will be.
  • The transformer on the speaker also serves as a safeguard to make sure individual speakers are not ruined by excessive wattage.