Can a receiver designed to run 4 ohms speakers @ 20 wpc drive two 8 ohms front bookself speakers?


Sanath Perera
I have a budget home theater in a box system designed to run 4 ohms speakers with 20 watts a channel at 4 ohms. Can I run 8 ohms bookself front speakers in this system designed for 4 ohms speakers? Would the receiver have enough power to drive the 8 ohms speakers? If the receiver produces 20 watts a channel at 4 ohms, would it produces a lesser amout of watts at 8 ohms? Thanks.

W = I*I*R = U*U/R
R = 4
I*I = 5
I = 2.1 A

U*U = 80
U = 9 v

80/8 = 10 W
5 * 8 = 40 W

your reciver will put out at least 10 watts and max of 40 watts into 8 ohms.

There should'nt be a problem driving 8 ohms.
you might get lower power.


As the previous post from Anonymous has set out in mathematical terms, you can get sound, but the resistance of the speaker to the power output from the amp is greater with 8 ohms than it is from 4 ohms, so the power delivered to the speaker is basically cut in half. So it effectively produces less musical power, but there is naother important factor to know when deciding if you can do this--that is, what is the sensitivity of the 8 ohm speakers (expressed in decibels)? If it is something like 91 db, then you can probably make it work. If it is something like 87 db or less, I would say it won't work.

I hope this helps.
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