Southwestern Bell CM660, CM860 S T R I B U T E D a U D I O P L a C E M E N T, I N T E N a N C E

D I S T R I B U T E D A U D I O P L A C E M E N T

The Sound Advance Prommercial series speakers possess extremely smooth and predictable off-axis frequency response. The chart below shows how far apart the speakers can be placed in a distributed audio system. The calculations are based on +/- 45 degrees of coverage from the speaker, and listener ear heights of 62" for standing and 40" for seated.

Speaker spacing in feet for a distributed audio system

	Standing Listener		Seated Listener
8 foot ceiling	5.7'	9.5'
10 foot ceiling	9.7'	13.5'
12 foot ceiling	13.7'	17.5'
14 foot ceiling	17.7'	21.5'

Distributed Audio Placement

A M P L I F I E R S E L E C T I O N

When choosing an amplifier the maximum number of speakers and the output level of each speaker must be known. The sum of the tap settings should never exceed 80% of the amplifier’s rated output. For example, if there are 5 speakers and the taps are set at 15 watts, the load would be 75 watts (5 x 15 watts = 75 watts). To arrive at the needed power for this number of speakers, simply divide the total load by .8. In this case, 75 / .8 = 93.75 watts. Therefore, a standard 100 watt amp would safely drive this load. To calculate the amount of usable power an amp offers, simply multiply the rated output by .8, i.e., 100 watts x .8= 80 watts.

W I R E G A U G E — 7 0 / 1 0 0 V O L T S Y S T E M

The most common wire used on commercial 70 volt systems is 18 gauge, 2 conductor, stranded, and jacketed without a shield. The wire starts at the amplifier location and is paralleled at each speaker location.

Wire length using 18 gauge is appropriate up to 700 feet with a 100- watt load. If you double the load (sum of your tap settings), you will reduce the footage by half, to 350 feet. Conversely, if you halve the load, you may double the acceptable wire length, i.e., a 50 watt load is safe over 1400 feet of 18 gauge. Stepping up to 16 gauge wire extends the allowable run length by approximately 35%. For example, a 100-watt load can go 700 feet on 18 gauge; the same load may be placed on 1100 feet of 16 gauge.

W I R E G A U G E — 8 O H M S Y S T E M

When using the CM860 and CM660 in an 8 ohm system the total wire resistance should be less than 10% of the speaker impedance. The CM860 and CM660 nominally 8 ohms impedance, so your total wire resistance should be no more than 0.8 ohms.

In simple terms, the extra resistance from the wire will have a very negative affect on the sound quality of the speaker. The sound can be less dynamic, definition of bass frequencies can be reduced, and in extreme cases, the high frequencies can be attenuated. Amplifier power is also wasted in the wire, reducing the maximum output level of the system.

Please refer to the following chart when deciding on the appropriate wire gauge for your installation.

Wire resistance in Ohms vs. length of cable run

Distance in Feet	50'	100'	150'	200'	250'	300'
20 gauge	.86	1.73	2.59	3.45	4.32	5.18
18 gauge	.65	1.30	1.94	2.59	3.24	3.89
16 gauge	.43	.85	1.28	1.71	2.14	2.56
14 gauge	.27	.54	.81	1.08	1.35	1.62
12 gauge	.17	.34	.51	.68	.85	1.02
10 gauge	.11	.22	.33	.44	.56	.67

PAINTING THE SPEAKER S AND G RILLES

The Sound Advance CM860 and CM660 speakers feature a tough weather-resistant ABS finish that may be painted to color match their surroundings. Use a weather-resistant outdoor paint and a spray gun. First remove the grille by carefully prying it away from the baffle. The driver components must be protected from paint when spraying. If necessary, you can fashion plugs by placing the speaker grille on a piece of cardboard and tracing around the outside of the grille. Cut just inside the line you drew on the cardboard and place the paint plug on the speaker baffle. Remove the paint plug when you are finished painting.

The metal grilles may also be painted. Use very thin paint (5:1). It will be easier to paint the grille while it is off the speaker. Avoid plugging up the holes with excess paint.

M A I N T E N A N C E

No maintenance is required when installed in accordance with installation and wiring guidelines described in this manual.

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