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Wiring subwoofers — what's all this about ohms?

How wiring affects your sub's output

Kicker 44DCWC102

Kicker DCWC102 ported enclosure with dual 10" CompC subwoofers

Confusion concerning watts, amps, and ohms has been around for as long as people have been putting subwoofers in cars. Watts and ohms are entangled in a series of mathematical formulas that link them intimately together such that when one of them undergoes a change in value, the other often does too.

Briefly, here's how it works

Amplifiers provide the electrical pressure in a circuit; ohms measure the resistance, or load, against that pressure; and watts measure how much power is released as work. So, using one of those math formulas, an amplifier that provides 100 watts of power through a 4-ohm speaker, will produce 200 watts through a 2-ohm speaker, because it's easier to push that reduced load.

Voice coil makes sound — amplifier pushes it

At the heart of every speaker and sub is a voice coil. This is the device that puts up the electrical resistance and performs the work. (The amplifier provides the power.) The resisting property of a coil is called its impedance and is measured in ohms. The lower a speaker's impedance, the easier it is for an amp to supply power to it. Problems arise when the amp's output meets very little resistance (low impedance) and it tries to put out more power than it was designed to produce. This leads to the amplifier overheating and then, hopefully, shutting down to protect itself from burning up.

You don't want the amp to over-do it

So the capability of an amplifier has to be considered before applying a load to it (hooking up a speaker). The manufacturer's specifications indicate an amp's minimum impedance requirements. Almost all amps can drive a 4-ohm load. Most amps can work with 2-ohm loads on each channel, but not when the channels are bridged together. Some amps can drive a load as low as one ohm.

Pioneer GM-A3702

The two channels of this Pioneer GM-A3702 amp can be bridged by wiring the subas indicated

Wiring options change a sub's impedance

To add to the confusion, in multiple-sub systems, the total impedance depends on how the subs and their voice coils are wired together — in parallel or in series. Parallel wiring means that the connection ends of each device are connected to the same things — plus to plus, and minus to minus. Series wiring means that the devices are wired one after the other — a plus of one to a minus of another.

When speakers or voice coils are wired in series, you add their impedances together to find their total impedance. Two 4-ohm speakers wired in series have a total impedance of 8 ohms. When speakers or coils are wired in parallel, however, the formula for their total impedance is more complicated. When the impedances of all the devices are the same, their total impedance, when wired in parallel, is that impedance value divided by the number of devices. For example: four 4-ohm speakers wired in parallel have a total impedance of 1 ohm.

Rockford Fosgate T1D212 sub

This Rockford Fosgate DVC 2-ohm sub has a built-in jumper so you can choose whether it has a 1-ohm or a 4-ohm total impedance

Dual Voice Coils give you even more wiring options

Subwoofer manufacturers make subs with dual voice coils (DVC) to take advantage of this difference in wiring schemes, so the user has more freedom of system design. A DVC 4-ohm sub can be wired into a system as a 2-ohm or as an 8-ohm load. A DVC 2-ohm sub can have a total impedance of 1 ohm or 4 ohms.

An example using 4 subs:

If I wanted 4 subs in a system, I might consider using 4 DVC 2-ohm subs, each with their voice coils wired in parallel to make them each 1 ohm subs, and then wire the 4 of them in series so my amplifier could drive them as a single 4-ohm load. Or, I could wire the voice coils in series, making them all 4-ohm subs, and then wire the subs in parallel so the amp would see the total load as one ohm. It would depend on my particular amplifier — which load it would do the best with.

Match power to power — use RMS only

To make subwoofers sound their best, they should be powered by an amp whose RMS output rating comes close to or even slightly exceeds the total of all the subs' top RMS ratings. If you want to run three subs whose RMS ratings are 300 watts each, you'll need about 900 watts RMS of power to run them.

Underpowered subs won't sound good or play very loud. Then, if you were to turn up the input to compensate, the amp could end up sending out clipped or distorted signals that could damage the subs. It's okay to overpower your subs a little bit, as long as the signal's distortion-free, because they're made to withstand occasional peaks well beyond their normal RMS rating.

What's right for you?

The sub and amp you need depends on what you want to hear. If you plan on listening to music at moderate volume levels or have a smaller car, a subwoofer with a lower power handling rating, say 100 to 250 watts, and a matching amp is a good combo.

The ultimate goal is to have the amp send its full power to subs that can handle it. The object of using different wiring options to optimize the impedance is to get the most power out of the particular amp and subs you have at hand. This also happens to be the most efficient way of running an amp & sub system. For more wiring specifics, check out our subwoofer wiring diagrams.

If you want to get right into choosing a subwoofer, take a look at our top-rated and best-selling subs.

  • Jake Stockett from Brigham City

    Posted on 10/5/2021

    I'm looking at adding (2) 10" shallow mount subs that are rated at 500 watts rms/800 watts peak. Should I go with the 10" - Dual 2 Ohm or the 10" - Dual 4 Ohm? The amp that I'm looking at is a 1,200 watt amp. Conservatively rated at 1,200 watts RMS power at a 1-ohm load, with the capabilities of reaching beyond 1,600 watts at max power output. Would this be a good amp to power both subs?

    Commenter image

    Buck Pomerantz from Crutchfield

    on 10/12/2021

    Jake, If you're asking will a 1200 watts RMS rated amplifier work with two 500 watts RMS rated subs, the answer is no - the amp will probably blow them to smithereens. But without knowing precisely what amp and subs you're referring to, we can't help you with accurate advice. If you want a question answered about a system, you must identify the gear by brand names and model numbers so we can get the right information to you.
  • Anthony from Jersey

    Posted on 9/24/2021

    I wanted to know how to connect 2 (6 1/2) mid-range loud speakers at 4ohm, 300 watt each to a 2000 watt, 2 ohm at 4x500 watt, 4 ohm bridged amp. Should/Can I bridge both speakers together and then connect to one side of the (bridged) location so that I may do the same to the other side with 2 (6x9) loud speakers? If so, can I connect a pair of 1 inch tweeters to offset the remaining power being given from amp to speaker? Or; So basically, with the 2 (6 1/2) speakers as mentioned above and the amp as mentioned above. What else (if any) can I connect to the amp and use its maximum power?

    Commenter image

    Buck Pomerantz from Crutchfield

    on 9/28/2021

    Anthony, It sounds like you need to talk to an Advisor about what you have, want, and what's possible for your sound system. To start with, sending 500 watts to a speaker rated for 300 will kill it. So there's no reason to describe how to wire them together. Also, tweeters don't off-set power, they play different frequency ranges at the same power level as their matching woofers. Plus, without knowing precisely what amp and speakers you're referring to, we can't help you with advice. If you want a question answered about a system, you must identify the gear by brand names and model numbers so we can get the right information to you.
  • Aaron Brown from Gand Island

    Posted on 9/4/2021

    So im thinking about buying a pair of Polk Audio DB 1242 SVC DB+ Series shallow-mount 12" 4-ohm subwoofer and Soundstream Reserve RSM1.4000D Compact mono subwoofer amplifier - 1200 watts RMS x 1 at 1 ohm. I can wire the subs down to 2 ohm correct?

    Commenter image

    Buck Pomerantz from Crutchfield

    on 9/7/2021

    Aaron, Yes, two SVC 4-ohm subs can get wired together to form a 2-ohm load. However, you should be aware that that amplifier is capable of putting out 850 watts RMS at 2-ohms, which is enough to blow those two 370 watts RMS, 740 watts RMS together, rated subs. We recommend getting a less powerful amp for those subs. Give us a call, so an Advisor can help you pick out the perfect gear for your system.
  • Darwin dunlap from York haven

    Posted on 8/22/2021

    I would like to know if I have a 12" dvc subwoofer rated for 500 watts rms at 4 ohms, will the rms watts changed when it is then wired in parallel to push 2 ohms? Or does the rms watts always stay the same wether it gets wired at 2 ohms or 8 ohm?

    Commenter image

    Buck Pomerantz from Crutchfield

    on 8/23/2021

    Darwin, The output of most amplifiers will react differently to different impedance loads. Theoretically, an amplifier will put out four times the power through a 2-ohm load as it would through an 8-ohm load. In the practical real amplifier world, the results will vary.
  • Leonard puga from Hanford

    Posted on 8/18/2021

    I got 2 jl audio 12w v2-d4 with 300 rms each and a memphis 16-mcd 1000 at 2 ohms is 600 rms is this a good set up and if so whats the best way to wire them up?

    Commenter image

    Buck Pomerantz from Crutchfield

    on 8/19/2021

    Those subs are rated for 600 watts RMS each, so that amp will work well with them wired like this.
  • Raymon M Smith from Tucson

    Posted on 8/13/2021

    Question.. I have a 2018 Kia Soul with a all 4 ohm Rockford Fosgate door speakers, which replaced 4 ohm factory speakers. Same factory head unit. My question is I recently bought a Cerwin-Vega VPAS10 10" 2O 550W Max / 200W RMS powered subwoofer. Will the fact that this sub is 2 ohms clash with my setup?

    Commenter image

    Buck Pomerantz from Crutchfield

    on 8/16/2021

    Raymon, The impedance of a component sub inside a powered subwoofer assembly is irrelevant to any other system consideration and won't affect any other component.
  • kam from Barnegat

    Posted on 8/11/2021

    I would like to start by saying cruthfield is on OG status and l always learn something new when l search for information. Now lets get into the the past mono amps would only have 1 + and 1 what you said (past) is accurate but now a days most mono amps have 2 + and after further research l came to find out that if you take 2 dvc 4 ohm subs and run in line it will equal 1 ohm....or in series 4 ohms...dvc 2 will equal .5 in line or 2 ohm in series. l found this out by experience lately....l have modified 3 systems in 60 days...ordering speakers give me the same headache as buying a car...everyone is loud and #1...

  • Aaron Bozigian from Lancaster

    Posted on 8/4/2021

    I plan on getting a set of four Kicker KS coaxial speakers rated at 4ohms (2 at 150 RMS and the other 2 at 75 RMS), a Rockford fosgate T1000X 5ad amplifier (RMS: 100 Watts x 4 + 400 Watts x 1 @ 4O 100 Watts x 4 + 600 Watts x 1 @ 2O), and a kicker Comp RT 12" down firing subwoofer rated at 2ohms (500 watts RMS). Will this all work together? Are there any glaring issues with this that would be damaging to any of these components? If so is there a way to minimize the risk or make it work together using all of these components?

    Commenter image

    Buck Pomerantz from Crutchfield

    on 8/4/2021

    Aaron, That amp is powerful enough to fry your rear speakers and subwoofer. But you should be alright as long as you set the amp gain low enough to never allow distortion to play.
  • Corey from Bolingbrook

    Posted on 7/18/2021

    I just got off the phone with one of your reps and was told that a 4 ohm sub (RF P3d4-12) could only be wired to 1 or 4 ohm and I wanted it to be wired to 2 ohms. Can the DVC RF 12 be wired to 2 ohms?

    Commenter image

    Buck Pomerantz from Crutchfield

    on 7/19/2021

    Corey, A single DVC 4-ohm sub, like a Rockford Fosgate P3D4-12, can only be wired as a 2-ohm load or an 8-ohm load. A single DVC 2-ohm sub, like a Rockford Fosgate P3D2-12, can only be wired as a 4-ohm load or a 1-ohm load.
  • Josh from Sioux City, IA

    Posted on 6/15/2021

    I am currently running two mtx 9512-44 on a taramps smart 3k. I'm considering getting them reconed with upgraded parts but they told me the only coils they have available for it are dual 1 ohm coils instead of 4ohm. How would that effect the sound and power handling of my subs?

    Commenter image

    Bruce Southall from Crutchfield

    on 6/16/2021

    Josh, That'll depend on how your present subs are wired. Two DVC 4-ohm subs can be wired as a 1-ohm, a 4-ohm, or an 8-ohm load. If yours are set up as a 1-ohm load, two DVC 1-ohm subs can also be wired as a 1-ohm, so the sound quality and power handling will remain the same.