Impedance
Impedance
With One or Two Subwoofers
When one or two CM8SW subwoofers are connected to the satellite speakers, the overall system impedance to the amplifier lowers.
System Impedance in Ohms (Ω)
One or Two Subwoofers
| 8Ω Sats | 4Ω Sats |
1 Sub | 4Ω | 2.6Ω |
2 Subs @8Ω each | 4Ω | 2.6Ω |
2 Subs @4Ω each | 2.6Ω | 2Ω |
If the impedance is too low for your ampli- fier utilize a Niles speaker selector or IM volume control to match the impedance.
VLSA (Four or More Subwoofers)
A VLSA (Very Large Subwoofer Array) installation lowers the amount of excur- sion required to achieve a high sound pressure level. Lowering excursion dra- matically improves the quality of the sound. VLSA installations are most appro- priate when the listener appreciates detail and bass extension, but must have a con- cealed installation.
Each subwoofer should have its voice coils connected in parallel for full output, there- fore the impedance of each is four ohms. Because of this low impedance, a multi- channel amplifier stable to 4 ohms is the best way to drive more than two sub- woofers. Each CM8SW is connected to its own channel of a
Check Your Amplifier’s Specs
Every amplifier has a minimum impedance specifications. Check your owner’s manual to determine whether or not your amplifier is capable of driving a four ohm load. This
specification may also be noted on the rear panel of the amplifier. If your amplifier is not able to drive a four ohm load it may only be used to power a CM8SW satellite/subwoofer system when an imped- ance magnifying volume control is incor- porated into the system
An amplifier stable to four ohms may be connected without impedance matching devices. Parallel connections via the “A” speaker terminals to one or two CM8SW subwoofers (If the voice coils are not in par- allel) and one pair of eight ohm satellite speakers results in a four ohm load.
The “B” speaker terminals cannot be used to power a second pair of speakers any- more. The low impedance drive capability of your amplifier is already utilized by the satellite/subwoofer combination. If you are connecting other speakers in other rooms you must install either a speaker selector or impedance magnifying volume controls.
A few professional/audiophile amplifiers advertise the capability of driving two ohm speaker loads. These amplifiers may be used without impedance matching devices if the rating is quoted as “RMS” or “Continuous” power and the amp does not push too much power.
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