QuestionI am confused about which ohm impedance to choose for a single Kicker L7 (12 or 15"). I cant find an answer that I understand. I read that I should match impedance of the amp (likely Kicker 1000.1) to the impedance of the sub (1000RMS). Others talk about wiring them down. I just need a clear answer.
AnswerHi Jamarcus,
Here's my rule of thumb: I try to choose an amplifier that's rated between 50-100% of the subwoofer's RMS power rating. For example, if you have a subwoofer rated at 1000 watts RMS, then any amplifier that can produce 500 to 1000 watts RMS should be fine.
The impedance rating makes things a bit trickier, because most amps will produce different power at different impedance ratings. The thing you have to remember is that impedance is a characteristic of the load--which means, in this case, the subwoofer or subwoofers. The impedance of the system will be determined by which sub you choose, and the way that you wire it.
For example, let's look at the Kicker ZX1000.1 amplifier. This amp is rated for 500 watts RMS at 4 ohms, and 1000 watts RMS at 2 ohms. There's no switch on the amplifier to change the output impedance. That will be determined by the subwoofer you use. If you connect a 4-ohm load, the amp can produce 500 watts; if you connect a 2-ohm load, the amp can produce 1000 watts. Most Kicker amplifiers (and many other brands) produce their maximum rated power with a 2-ohm load.
So, if you have a Kicker ZX1000.1, and you want it to produce 1000 watts, then you need to connect a subwoofer system that will present a 2-ohm load when it's connected to the amp. The amplifier doesn't know how many subs you're connecting, or whether they're dual voice coil or single voice coil designs, or what the individual impedance of each sub is. The only thing that affects the amplifier is the load impedance at the speaker terminals. That's why I'm using the term "load" instead of just saying you need a 2-ohm subwoofer: when you combine multiple subwoofers, or use dual voice coil subs like the L7, the load impedance on the amplifier might be different than the impedance of each sub.
The L7 is available as a dual 2-ohm or a dual 4-ohm. When you wire the L7 to an amplifier, you have to wire it so that both voice coils are connected to the amplifier output. You can wire the two voice coils in series or in parallel.
If you wire the voice coils in series, the load impedance will be double that of a single voice coil. If you wire the coils in parallel, the impedance will be half that of a single voice coil. These are your options: you can't just use one coil. You have to combine the two, either in series or in parallel. That means a dual 2-ohm sub can't be a 2-ohm load; it has to be either 1 ohm or 4 ohms. A dual 4-ohm sub can't be a 4-ohm load; it must be wired as 2 ohms or 8 ohms. When you combine multiple subwoofers, things get even more complicated. Luckily, you're just going to be using one sub.
So here's the answer: if you want to use a single L7 with a ZX1000.1 amplifier, and you want the amplifier to produce 1000 watts RMS, then you should buy a dual 4-ohm subwoofer and wire the coils in parallel to get a load impedance of 2 ohms at the amp. (The Kicker sub's manual will include parallel and series wiring diagrams).
By the way: if you're buying the 12" version of the L7, or if you're using a ported box, you probably wouldn't want to use a 1000-watt RMS amplifier. Kicker reduces their subs' power rating when used in ported boxes, and the 12" L7 isn't rated for 1000 watts anyway. You might want to consider using a ZX750.1 instead.
Hope this helps!
Brian
