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Download In-Wall Volume Control Installation Instructions
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In-Wall Volume Control Installation Instructions Stellar Labs™ In–Wall Volume Controls are designed for connection between the speaker output of an amplifier, speaker selector, or distribution box, and a speaker pair. They adjust the volume of remote speakers by attenuating the audio signal, after the amplifier. To assure maximum power transfer and efficiency, and minimal heat, these controls use autoformers instead of L-pads or resistor networks. These controls are available in four different colors, with models capable of handling 100W or 300W of peak music power. All Stellar Labs™ Volume Controls represented here are impedance-matching type. While they are perfectly suitable in applications utilizing only one pair of speakers, they also enable a typical stereo amplifier to drive up to 16 pairs of speakers, without impedance related problems. Impedance Matching Volume Controls White Ivory Almond Black Model 100 Watt 50-7820 50-7821 50-7822 50-7823 300 Watt 50-7840 50-7841 50-7842 50-7843 Stellar Labs Division of MCM Electronics 650 Congress Park Drive Centerville, Ohio 45459 www.mcmelectronics.com © 2010 MCM, a Premier Farnell Company SPEAKER and AMPLIFIER IMPEDANCE Calculating Speaker Impedance All speaker systems place a load on the amplifier driving them. That load, determined by the impedance of each speaker system, is measured in ohms (designated by the Ω symbol). The actual impedance of a given speaker system will vary depending upon the frequency at which that impedance is measured. To ease impedance calculations, speaker manufacturers rate speakers at average (or nominal) impedance, across the rated frequency response of that speaker. For consistency, most in-wall and ceiling speaker manufacturers follow an established standard of 8Ω. This ensures that multiple–speaker installations have power distributed evenly across the entire system. From this point forward, all calculations will be with regards to one amplifier channel. In stereo applications, the same consideration must be given to both the left and right channels. Since all speakers in a given system are typically be the same impedance, we will use a very simple method to calculate the total impedance of multiple speakers connected to an amplifier. Simply divide the impedance of the speakers by the number of speakers connected. If one pair of 8Ω speakers is connected to a stereo amplifier, the resulting load on each amplifier channel is 8Ω. If two pairs of 8Ω speakers are connected, the resulting impedance is 4Ω. If three pairs are connected, the resulting impedance is 2.67Ω, four pairs result in 2Ω and so on. The challenge encountered with distributed audio systems, is they normally involve many speaker pairs connected to a single amplifier, and most amplifiers cannot handle speaker loads below 4Ω (although some models handle loads as low as 2Ω). Because of this, systems utilizing more than two pairs of speakers on a 4Ω amplifier must have the speaker impedance increased to ensure the load does not become too low. Stellar Labs™ Volume Controls This is where Impedance Matching Volume Controls come in. Each Stellar Labs™ In-Wall Volume Control includes an Impedance Matching circuit, with selectable multiplier taps, enabling a single amplifier to drive a large number of speaker pairs. Located on the rear of each control are jumper pins, with an attached shorting bar. By selecting the appropriate pins, the impedance of the connected speaker is multiplied by x1, x2, x4 or x8. For example, an 8Ω speaker connected to a control set for x4, now becomes a 32Ω speaker load. If the control is set for x8, the speaker load is now 64Ω. As you can see, this enables a far greater number of speakers to be connected to a standard amplifier, and maintain a load above 4Ω. Additionally, if multiple speaker pairs are used, that happen to have differing impedance, the multiplier can be used to even out the actual impedance load of each speaker. When connecting multiple speaker pairs to a stereo amplifier, a separate volume control should be used for each pair. Also, depending upon the number of speaker pairs used, and the impedance of each speaker, it may not be possible to achieve a final impedance of 4Ω per channel at the amplifier. Since most amplifiers operate most efficiently between 4Ω and 8Ω, it is perfectly acceptable as long as the resulting impedance falls within that range. If that value is not possible, a resulting impedance above 8Ω is also fine, although the amplifier will not operate as efficiently. The critical issue is not to fall below 4Ω (unless the amplifier happens to be 2Ω stable), because at that level many amplifiers will fall into protection mode and shut down, and possibly sustain damage. If you are not certain of the minimum load of the connected amplifier, assume it is 8Ω. INSTALLING IN–WALL VOLUME CONTROLS Mounting All Stellar Labs™ in-wall volume controls are designed for installation in a standard single–gang electrical box. Take note that depending upon model, these controls will require at least 3" mounting depth. Because volume controls are considered a low– voltage device, they may suitably be mounted in open-backed boxes, brackets or mud rings. This type of mounting is often considered desirable as it allows for more space behind the control for routing cables. Multiple gang brackets and electrical boxes are available for installing multiple units in one location. These types of mounting devices are readily available from most home building centers, and various models from Carlon, Caddy and Arlington are readily available directly from MCM Electronics. Caution: Low voltage devices, such as volume controls may not share an electrical box with standard AC wiring devices such as wall switches, AC receptacles or dimmers. Connections When routing cable through walls to speakers and volume controls, care should be taken to avoid close proximity to AC power lines. This is important for safety reasons, as well as reducing the possibility of noise being introduced on the line. When selecting in–wall speaker wire, be sure to use cable designed for that purpose. Two or four conductor, 16AWG or 14AWG wire is recommended, and most local electrical codes require cable to carry a CL2 or CL3 rating. Be sure to verify compliance with local codes prior to installation. Caution: Speaker cabling and AC power lines should never pass through the same opening drilled in interior wall studs. FINAL SETUP AND USE Testing Once all controls and speakers are installed, it is recommended that the system be tested prior to connection to the amplifier. This will ensure that the desired speaker load is present at the amplifier output, thus preventing possible amplifier shutdown or damage. The most effective way to accomplish this is to measure the impedance at the amplifier (without the amp connected). An impedance measuring device such as the Tenma Model 72-6947 is required to accurately accomplish this. This meter measures the impedance of a speaker system, at an audio frequency of 1KHz. This step can serve as a reliable method of preventing unreliable and potentially damaging operation later. Note: Using a standard DMM, ohmmeter or multimeter is not effective for this purpose, as these devices measure impedance at DC, not at an audio frequency. Since a speakers and volume control devices impedance varies with frequency, a standard ohm meter will not provide accurate readings. Setup • Once the amplifier is connected to the system, prior to turning on the power, make sure that the amplifier gain (volume) is set to the MINIMUM setting • Be certain that all of the In–Wall volume controls are set to the MAXIMUM setting • Turn the amplifier on and select a desired music source • Slowly increase the volume of the amplifier until sound is heard from the speakers • Walk through all areas in which speakers are installed, and make certain that sound is present at all speakers o If sound is not present at any speaker, turn off the amplifier power and check speaker connections • Adjust the volume or balance control fully to one channel (either left or right) • Again, walk through all areas, noting that sound is present at only one speaker • Change the volume or balance control to shift fully to the opposite channel (either left or right) • Walk through all areas, noting that sound is present at the opposite speaker than in the prior walkthrough o If incorrect results occur, turn off the amplifier power and check speaker connections • Adjust the volume or balance control so that the left and right channels are now equal • Now adjust the volume of the amplifier to just above the level that will be considered the maximum listening level from the system • Move through each area, adjusting the in–wall volume controls to a comfortable listening level Note: If at any time, the amplifier temporarily disengages, or shuts down, the system should be powered down and checked for proper connections. If it is determined that all speakers, volume controls or other devices are connected properly, and the system continues to shut down, there is possibly a speaker impedance problem. In this case, power down the system, remove the volume controls from the wall, and select the next higher impedance multiplier setting. For additional information regarding distributed audio system installation, please consult documentation included with other components. For additional questions, please contact the MCM Technical Support Department at 1-800-824-8324, or send an email to [email protected]. Specifications White Ivory Almond Black Power Capacity (RMS) Power Capacity (Peak) Frequency Response Impedance Multipliers Rotary Switch Positions Attenuation step Position 1~7 Position 8~11 Position 12 50-7820 50-7840 50-7821 50-7841 50-7822 50-7842 50-7823 50-7843 25W 100W 100W 300W 35Hz~20KHz x1, x2, x4, x8 12 3dB per step 6dB per step Off (fully counter clockwise) Dimensions 25W RMS / 100W peak models 100W RMS / 300W peak models MCM Custom Audio and Stellar Labs™ products are warranted, by MCM Electronics, against manufacturer defects for a period of one year from the original date of purchase. This warranty is limited to manufacturer defects, in either materials or workmanship. MCM Electronics, or any other worldwide divisions of Premier Farnell PLC, are not responsible for any consequential or inconsequential damage to any other component, structure or the cost of installation or removal of said items. For questions or specific information regarding warranty replacement or repair, contact: MCM Electronics 650 Congress Park Drive Centerville, Ohio 45459 1-800-543-4330 www.mcmelectronics.com