One of the most important components in a paging system is the speakers. So before we define any paging system, we start by determining the amount of sound required at each location. Once we know the type of sound required, we can select the right speaker. After we have defined the speakers, we can determine the right amplifier to use.
What’s the best speaker for you? Well it depends on a number of things. For example, do you want to hear music or just voice paging? The type of speaker also depends on how large an area you want to cover with sound. The background noise and where you want to place the speaker is also important. It may be necessary to select a different speaker for each location. This article reviews how to select the right speaker for the job. We will review the sound output which is measured in decibels (dB), the sound quality (or frequency range), and the power required at the speaker.
Types of Speakers
You can only connect up to four 8-ohm speakers to one of the 8-ohm outputs of an amplifier. A 70-volt speaker system has a transformer inside each speaker, as well as a single transformer at the output of the amplifier. You can daisy-chain many 70-volt speakers to a single 7-volt amplifier output. For example, you can attach about eight 70-volt speakers to a single 70-volt amplifier, with 20-watt power output. The IP7-SS20 is an example of a 20-watt, network attached IP amplifier. The more speakers you attach the lower the power available to each speaker, and thus the lower the maximum sound output level from each speaker.
Power and Sound Output
Speakers are rated at a specific sound level (measured in dB), at a specific power level (1 Watt), and at a specific distance away from the speaker (1M). DB or decibel is the measure of sound level output. A Watt is the electric power that comes from the amplifier. For example, 60dB is the sound level of normal conversation. 120dB is the sound of amplified rock concert, and by the way experts recommend using earphones when the sound level is continuously over 85dB. For more about sound levels take a look at our other article, “How Loud is Loud”.
To increase the volume, we increase the audio power to the speaker. The rule of thumb is that every time we double the power, we get an additional 3dB of sound out. So if we select a speaker that has a specification of 94 dB @ 1W/1M, and we double the power to 2 watts, we increase the sound level to 97dB, and if we double the power again (4 watts), we get another 3dB or 100dB of sound.
Let’s take a look at an actual speaker.
Suppose we select the PH20T horn from Penton, and mount it on the side of the building. The specification says we get 105 dB @ 1W/1M. It also says that this speaker is rated at 20Watts maximum. This means we can power the speaker with up to 20W without damaging it. We can use an IP amplifier like the IP7-SS20 to provide the audio power. We attach the amplifier directly to the network, and the speaker to the 8-ohm output of this small amplifier. A separate power 24 VAC adapter is also needed. At the maximum power we will get about 118 dB of sound. This is the sound level at 1M from the speaker and it’s pretty loud so don’t stand too close to it.
Sound Level and Distance from Speaker
The further away you are from the speaker the less sound you hear. The sound level goes down 6dB every time we double the distance from the speaker. For example, a speaker that provides 118 dB of sound at 1M will have a sound level of 112 dB at 2 M from the speaker. At 4 m (13 ft.), the sound is 106 dB; at 8 m (26 ft.), it’s 100dB; at 16 m (52.5 ft.); and at 32 m (105 ft.), it’s 96dB, etc. Just for your reference, 96 dB is the sound of a power mower. So you can see that this speaker and amplifier would provide enough sound to allow children playing in a large yard, to hear an announcement.
Speakers are also rated by the angle of coverage. The coverage is measured in angle. If you are directly in front of the speaker it will sound much louder than if you are off to the side. For example, the Penton PBC6T mounts on the wall and it can best be heard at an angle within 115 degrees.
If the speaker is mounted on the ceiling, you would like to select one that has as wide a coverage area as possible.
Sound Quality or Frequency response
Just like your home stereo system, the wider the frequency range of the speaker the better the sound quality will be. The specifications will tell you the range of frequency response for the speaker. If you are playing music, you want a frequency range that’s as wide as possible. Better speakers will cost more, so you have to first determine what you want to hear. For example, the Penton LIS8T72 ceiling speaker has a very good frequency response of 60 to 20,000 Hz so it’s great for both music and voice paging. Other speakers have frequency ranges of 300 Hz to 15 KHz, which is just fine for listening to a person talking.
Where they are placed
There are a variety of speakers available, some mount in drop ceilings, others go on the walls. There are those you can use outdoors and others that are only used indoors. As we discussed the sound level changes the further away you are and the further off centered you are form the speaker. If you place a speaker in the ceiling it will sound very good when you are close to it. The higher the ceiling the more dispersion you will get. So if you have a room with 10 ft. ceilings you may be able to hear the speaker when you are about 5 ft. off center, but if you have a ceiling that’s 20 ft. tall you can be 10 ft. away from the center of the speaker.
If you have a drop ceiling and the room is less than 30 ft. by 30 ft. in size, you can usually use one of the Penton LIS8T72 ceiling speakers or the Quam System 5/70 speaker system. These are easy to install because they just replace a ceiling tile. If you want to save money, use the small round speakers that require a cut out of the ceiling tile such as the Quam C5 or Penton RCS ceiling speakers.
If you have a long hallway, there are dual speakers that send the sound in two different directions. You can select the Cell10BDT or the Quam System 11 bi-directional speakers. Outdoors you can use a weatherproof horn type speaker such as the Penton PH20T or the Quam QH16T paging horn.
The powered speaker is the easiest type of speaker to install, but they cost more. It includes a built in amplifier. The SPKR-11-BD-P, from Digital Acoustics, is an example of a bidirectional speaker that attaches directly to the network. The speaker includes a built in 8-watt amplifier. It’s very easy to install, since all you need is a network connection that includes PoE. The IP powered speaker includes software (for your PC) that allows you to send pages or music right from your computer. For more about network attached paging systems take a look at Paging Over IP Systems.
The best speaker for your IP paging system depends on where and how you want to use it. You can select the right speaker by looking at the speaker specifications. It describes the power required to achieve a specific sound level. It also shows the frequency response and angle of sound dispersal. You may also select the speaker for the ease of installation or even how it looks.
If you need help selecting the right speaker, just contact us at 1-800-431-1658 or 914-944-3425 or use our contact form.