Impedance

[Lucille]

I'm not familiar with the concept but I understand that differing impedences can sometimes present a problem and I have heard that receiver damage can occur in certain situations. I want to use my Denon 3805, 8 ohm speakers, but 4 ohm Boston Acoustic subwoofer.
Will that work?

 

[j_garcia]

Receiver damage will not occur from low impedance unless it overheats, though nearly all receivers have thermal overload protection these days.

If your sub has it's own amp, it's impedance doesn't matter to your receiver.

 

[MDS]

Simply stated impedance is a measure of how much resistance the speaker puts up to the flow of current. It may be a problem if you use lower impedance speakers than your receiver is rated to handle because it will cause more current to be drawn than the receiver can supply without overheating. A search should find many threads where the gory technical details are discussed, but I think that simple explanation is sufficient.

If that subwoofer is powered; ie has its own amp and is connected to the receiver in the usual way - subwoofer cable from the LFE out of the receiver to the line-in/lfe of the sub - then the impedance of the subwoofer is of no concern. Its own internal amp was speced and designed to handle that woofer. The receiver is doing nothing but sending the low level audio signal to the sub to be amplified.

 

[Lucille]

Thank y'all