Convert 4 Ohm Speaker to 2 Ohm

I have an 07 Acura TL. I've had to replace the rear stock speakers once in this vehicle - due to some typical jackassery on my part. When I replaced them I found that the originals were 2 ohm, but 4 ohm speaker won't cut it with the stock nav head unit. I bought some replacement 2 ohm speakers, but one of those took a dump on me - just through regular usage - no jackassery. I'm not willing to screw around with replacing the head unit, adding amps, buying new 2 ohm speakers (as the options are limited and don't trust the replacement brand), etc. I was talking with someone else and they suggested just jumpering a set of 4 ohm speakers, down to 2 ohm.

I want to take this route, but want to jack around with this setup with an old head unit and some old 4 ohm speakers I have.

My questions, since my electricity math sucks-

To make these 4 ohm speakers I have, would it be best to place a 2 ohm resistor across the + and -, or in series on either the + or -?

Is a 2 ohm resistor proper for this reduction or does the max watt rating of a speaker effect this resistance?

I am going to be trying this out, regardless if it's best practice. I won't personally hold anyone responsible for any thoughts they have and want to discount any replies that say I shouldn't do this because I'll wreck something.

Experiments always come with risk but are fun.

Thanks all!

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IT Services Provider

A 4 ohm speaker can not become a 2 ohm. There are several manufacturers that make 2 ohm drivers. Infinity is one that comes to mind.

Just in case you didn't catch that, a 4 ohm speaker can never become a 2 ohm speaker.

The issue at hand is that at 4 ohms you don't have enough power to get adequate results from a system that was designed to run at 2 ohms. If you take 4 ohm speaker and wire it in parallel with a 4 ohm resistor you WILL get 2 ohms of total resistance. However, your speaker will still get the same amount of power and all the additional power created by dropping the ohm load will go to the resistor and be turned to heat. If you were bright enough to properly size the resistor for the amount of power it will be dissipating and took care mounting the resistor away from anything that could catch on fire you may not start a fire in the car. If you undersized it or keep it near carpet / insulation you may catch the car on fire. Those resistors can get HOT!

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Kevin Pierson

here...

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It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."

The only way to convert a 4-ohm speaker into a 2-ohm speaker is to replace the voice coil.

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Or use a transformer.

PS - I'm not saying that's practical in this case, but it is - or was - a common technique.
But to apply to a big or LF sub etc - forget it! A new sub or amp would be far lighter. And impedance matchers - a new sub or amp would be cheaper.

oldspark wrote:

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Or use a transformer.

PS - I'm not saying that's practical in this case, but it is - or was - a common technique.
But to apply to a big or LF sub etc - forget it! A new sub or amp would be far lighter. And impedance matchers - a new sub or amp would be cheaper.

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But that still does not change the impedance of the loudspeaker, it only changes the effective impedance at the amplifier and it is a power-waster. :)

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Partly true. Obviously the speaker impedance does not change, but the amp sees 2 Ohms and thus delivers its full power.
Paraphrased, the 4 Ohm speaker receives the same power as a 2 Ohm speaker would (less a few% inefficiency).


PS - apart from the slight transformer inefficiency, no power is wasted - it is almost fully transferred.

100% true. You cannot change the impedance of the speaker using any sort of external device. Period. So, if your transformer has a 2-ohm primary causing the amp to produce, say, 100 watts at full power, and it is then coupling that into a 4-ohm load, how much power will be utilized by the 4-ohm load? The voltage ratio will still be 1:2, yes?

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100W.
No - not 1:2, ~1:1.4.


PS - I didn't specify a 2R primary. If you had a 2R primary, then it's only 50% transfer.
I assumed a close to a 0R primary RESISTANCE.
If the amp can't handle low ohmage DC then insert a resistance or use a 2R primary. Same thing - then you lose 50% of the power so there is no reason to do it - ie, the 4R gains no power (unless the amp pushes more than twice the power into a 2R than 4R).

But IMO it doesn't matter. As I said, impedance matching transformers simply are not practical - not for the power we are discussing, nor to match impedances of the same magnitude.

After reading this and looking around, I guess I may not have been looking at it properly. By adding a resistor, I'm increasing the resistance, not lowering it, correct? In that case is it possible to convert the opposite direction? I'm not looking to put it into practice, but just wondering.

As to the other post about other manufacturers that produce them, I purchased the mentioned brand's 2 ohm speakers originally and those are the ones that crapped out - without abuse - just listening to sports radio, etc.

2 ohm speakers have been terribly difficult just to find, and I am not going to replace the head unit as it is part of the nav and dashboard. Also, I don't want to screw around with digging around in the dash to add amps, etc. as I would need to do so for the dash tweets, the front door 6.5's and the rear 6.5's.

If there's an easy way to do this and I'm over thinking how much is involved, let me know.

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IT Services Provider

No. For your purposes there is nothing you can do.

Although you can make the "speaker load" look like 2 Ohm or 8 Ohm etc by adding another 4 Ohm resistor (or speaker), NONE of those will increase the power from your 4 Ohm speaker. It will still be a 4 Ohm speaker and hence the same power for a given voltage.


Replace the speakers.

The problem is that the unit only supplies for 2 ohm. I can't find any speakers that are 2 ohm, other than the ones I've already tried that are crap.

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IT Services Provider

It should be able to supply a 4 Ohm speaker without problem (despite what I once thought until educated by the12volt).

It will probably be at half the power and hence slightly lower volume but nothing will change that apart from different speaker (maybe more sensitive?) or a different amp or an additional amp.

if you bought infinity speakers im not surprised that they blew under normal conditions, they just dont last for whatever reason. but dont let that get you away from the best solution of buying new speakers, i think JBL makes 2 ohm speakers, a lot of higher end brands make 2 ohm speakers. the XXX components from RE audio are also 2 ohm speakers but those will probably require more labor to install than just screwing in a new speaker in the door.

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There's no such thing as an amplifier that can only supply into 2-ohms. ANY amplifier can supply any higher impedance than the minimum they list in the specs. And it is IMPOSSIBLE to change the impedance of a loudspeaker voice coil without replacing the voice coil.

Once more for clarity: If your amplifier is rated into 2-ohms, that means 2-ohms is the least amount of impedance it can handle. It will work just fine with anything higher than that.

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