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The right amp for a subwoofer comes down to two numbers: how much RMS power your subs can handle in total, and the final impedance (ohms) they present once they’re wired together. Get those right and the rest is just picking a model. Here’s how to work it out in a few minutes, with examples for popular subs.
The short version
- Add up the RMS ratings of all your subs. Ignore “peak” and “max”.
- Work out the final impedance from how the voice coils are wired.
- Choose an amp that makes about 75–100% of that total RMS at that impedance.
- Check that your wiring and electrical system can feed it.
Step 1: add up your subs’ RMS power
Use the RMS (continuous) rating, which every reputable brand lists. A Kicker CompR 12 is rated 500 W RMS, so two of them total 1,000 W RMS. The 1,000 W “peak” figure on the same box is irrelevant here.
Step 2: find your final impedance
Amps make more power into lower impedance, but only down to the load they’re stable at. How you wire the voice coils sets the load:
| Your subs | Coils wired | Final load |
|---|---|---|
| 1 × dual 4 Ω (DVC4) | Parallel / series | 2 Ω / 8 Ω |
| 1 × dual 2 Ω (DVC2) | Parallel / series | 1 Ω / 4 Ω |
| 2 × DVC4 | Each sub series, subs parallel / each parallel, subs parallel | 4 Ω / 1 Ω |
| 2 × DVC2 | Each sub series, subs parallel | 2 Ω |
| 2 × single 4 Ω (SVC4) | Parallel | 2 Ω |
| 2 × single 2 Ω (SVC2) | Parallel | 1 Ω |
Step 3: match the amp
Look at the amp’s RMS rating at your final load, not its headline number. For example, the Rockford Fosgate P1000X1bd makes 1,000 W at 1 Ω but 500 W at 2 Ω and 300 W at 4 Ω. Aim for 75–100% of your subs’ total RMS at the final load; a little more is fine if you set the gain carefully.
| Total sub RMS | Look for an amp that makes | Examples (rating at that load) |
|---|---|---|
| 300–400 W | 250–400 W | Rockford R2-500X1 (300 W at 4 Ω, 500 W at 2 Ω) |
| 500–600 W | 400–600 W | Kicker CXA800.1 (600 W at 2 Ω); Rockford R2-500X1 (500 W at 2 Ω) |
| 800–1,000 W | 750–1,000 W | Rockford P1000X1bd (1,000 W at 1 Ω); Rockford R2-750X1 (750 W at 1 Ω) |
| 1,000–1,200 W | 1,000–1,200 W | Kicker CXA1200.1 (1,200 W at 1 Ω or 2 Ω); Rockford R2-1200X1 (1,200 W at 1 Ω) |
| 2,000 W and up | 2,000–3,000 W | Taramps Smart 3 Bass (3,000 W at 0.5–2 Ω) |
Worked examples
- One Kicker CompR 12 (DVC4, 500 W): wire the coils in parallel for 2 Ω and look for 400–600 W at 2 Ω. The Kicker CXA800.1 (600 W at 2 Ω) or Rockford R2-500X1 (500 W at 2 Ω) fit.
- One Rockford P3D4-12 (DVC4, 600 W): 2 Ω again, so 450–600 W at 2 Ω. The CXA800.1 suits it; the R2-1200X1 (800 W at 2 Ω) gives headroom if you set gain carefully.
- Two CompR 12s (1,000 W total): wire to 1 Ω and pick 750–1,000 W at 1 Ω, such as the P1000X1bd. See our two-12s guide for more.
Step 4: check your power and wiring
A 1,000 W RMS amp can draw around 90 amps at full output. That needs 4 AWG copper wire on a typical run; bigger systems need 1/0. Our amp wire gauge calculator gives the exact size and fuse, and our wiring kit guide covers what to buy. Above roughly 1,500 W, check your alternator too.
Underpowered vs overpowered
Neither is dangerous by itself. What damages subs is a clipped (distorted) signal, which usually comes from a small amp turned all the way up, or any amp with the gain set too high. A slightly bigger amp with sensible gain is safer than a small one pushed hard. Our clipping guide explains how to set gain properly.
FAQs
Should the amp match the sub’s peak rating?
No. Peak ratings are marketing. Always match RMS to RMS at the final impedance.
Is a 1-ohm amp always better?
Only if your subs can be wired to 1 Ω. If they can’t, look at the amp’s 2 Ω or 4 Ω rating instead.
Can I use a 4-channel amp for a sub?
Yes, bridged, but most 4-channel amps make far less bass power than a monoblock of the same size.
What about a powered sub?
If you just want better bass from a factory stereo, a powered sub such as the JBL BassPro SL2 avoids amp matching altogether.