# Tandem woofers, low combined DC resistance - effects on amplifier?

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#### Zoodle

Effects on amplifier of tandem woofers having low combined DC resistance?

(Re-posted from 'speakers')
Gentlemen, I have two nominal 'ohm8' woofers to tandem, giving 2.8 ohm DC resistance. I understand the amp won't see that at audio freqs, but that number is still a little scary, and I'm concerned about how the amp might perform. Could this be a problem? I'm aware that designing a good speaker means not making life too hard for the amp, hence my question.

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#### EWorkshop1708

If your amp can push a 4 ohm load, then you are ok.

DC resistance is usually lower than the impedance of the speaker.

Two 8 ohm speakers in parallel are 4 ohm impedance.

If your amp can not push 4 ohms, then just use the speakers in SERIES which doubles the ohms, instead of halving. (16 ohm impedance) And as an added bonus, your speakers draw less current, so you can drive them with a bigger amp without blowing them, as they are dividing the volts between them.

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#### AndrewT

Two 8ohms in parallel is equivalent to driving a 4ohms speaker.
Two identical 8ohms drivers in identical boxes wired in series is equivalent to 16ohms.

An alternative is to use one amplifier to drive each 8ohms speaker.

#### Zoodle

Thanks. It's just that many 8 ohm (nominal impedance) woofers have RE 6.x, while the ones I'm looking at are RE5.6, yet are still described as 8ohm impedance. I've even seen some with 5ohm RE, still with an 8ohm rating. My amp will drive 4 ohm impedance and less, but will two parallel 8ohm woofers with combined RE of RE 3.1 be somehow easier to drive than two parallel 8 ohm woofers with a lower RE (eg 2.8)? I'm hoping to get the perspective of someone who builds amps.

#### AndrewT

....................My amp will drive 4 ohm impedance and less,....................
Two 8ohms in parallel is equivalent to driving a 4ohms speaker.
and that was a re-statement of EW's post
Two 8 ohm speakers in parallel are 4 ohm impedance.

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