Wiring several speakers, PA horns or subwoofer voice coils to one amplifier channel changes the load (impedance, in ohms) the amplifier sees. Use this calculator before you connect anything: too low a load can overheat or shut down an amplifier.
Nominal impedance is a rating, not a fixed number: the real value changes with frequency. Use it to match the amplifier's rated loads, and avoid mixing different impedances in parallel, because the lower-impedance speaker takes more of the power. For the details of DVC wiring, read subwoofer impedance and voice-coil wiring; for outdoor horn arrays see how to wire multiple PA horn speakers.
The amplifier tries to deliver more current than it was designed for. It can overheat, go into protection mode, distort or fail. Keep the final load at or above the amplifier's minimum rated impedance for that channel or bridged mode.
Yes. A higher load is safe for the amplifier; you simply get less power. For example, many amplifiers make roughly half the power at 8 Ω that they make at 4 Ω.
Each DVC 4 Ω sub is 8 Ω with coils in series or 2 Ω with coils in parallel. Two subs with coils in series and subs in parallel give 4 Ω; coils in parallel and subs in parallel give 1 Ω.
You can calculate the load, but in parallel the 4 Ω speaker gets twice the power of the 8 Ω speaker, and in series the 8 Ω speaker gets more. Matching speakers sound more even.
More free audio tools: Speaker impedance calculator · Amp wattage & SPL calculator · Speaker wire gauge calculator
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