Help me understand Ohms please

[thedoc46]

OK, so I've got a Yamaha RX-A2010 receiver, that is set to 6ohms, because my Kef home theatre speakers are 6ohms. (the default on the receiver is typically 8ohms, but i changed it to 6ohms)

However, today I decided to make good use of the second zone that my receiver supports. So i ran speaker wire to a separate room, and purchased a pair of JBL bookshelf speakers. However they're rated at 8ohms. But my receiver doesn't allow for a change of ohms for the different zones.

So i'm in effect, running my 8ohm speakers, via a receiver that's been set to 6ohms!

They sound fine. The Yamaha is not hot, so do I have anything to worry about?

 

[Grimley]

I wouldn't have thought so unless you plan on playing anything on this setup at loud volumes. I'm sure Lucid (the resident forum expert) will be along shortly to confirm this.

 

[lucid]

lol @ Grimley

thedoc46, the way you have it set now is fine. The impedance figure (Ohms) is only a rough average anyway.

The resistance of a speaker alters with respect to frequency. An 8 Ohm speaker can dip as low as 2-3 Ohm and go up to 16+ Ohms

 

[thedoc46]

lol @ Grimley

thedoc46, the way you have it set now is fine. The impedance figure (Ohms) is only a rough average anyway.

The resistance of a speaker alters with respect to frequency. An 8 Ohm speaker can dip as low as 2-3 Ohm and go up to 16+ Ohms

Thanks Lucid. So would you say I would be better setting the receiver back to its default of 8ohms? Or leave it at 6ohms

My speakers are 6ohm Kef Q70 fronts (from the 90's), My center is a 6ohm Kef 90 again from the 90's and the rears are recently purchased in ceiling 6ohm Yamaha's. My sub is an active HSU VTF-2 MK4, so i guess that makes no difference.

My zone 2 which is in a different room altogether are JBL bookshelf 8 ohms.

 

[lucid]

Thanks Lucid. So would you say I would be better setting the receiver back to its default of 8ohms? Or leave it at 6ohms

Which bit of "the way you have it set now is fine" was difficult to understand??

 

[thedoc46]

Which bit of "the way you have it set now is fine" was difficult to understand??

I understood it fine, i was asking if there was a preference to one way or another. Fine can be taken in two ways.

 

[lucid]

Lower ohms on the amp into higher ohms at the speakers.
Amp on 6 ohm for speakers a mix of 6 ohm and 8 ohm.

 

[wonko]

For a given voltage output from an amp, a lower impedance speaker draws more current than high impedance speaker, resulting in more heat being generated within the the amp.

I've recently been looking at what this switch does on on my A2020 and I understand that setting it to 6 ohms simply reduces the voltage that the power amp rails run at, which in turn limits the maximum power output/current/heat. It's one of the protections against the amp being 'overdriven' but at the expense of some dynamic headroom for handling transients.

Attaching 8 ohm speakers to the amp set to '6 ohm' is fine - this is what Yamaha recommends when you've got different impedance speakers attached, and you can think of it as putting a limiter on the volume control.

However, running 6 or 4 ohm speakers onto the amp set to '8 ohm' is also fine providing you're not pushing the amp too hard (which you shouldn't anyway).

Bottom line? Probably just leave it set to 6 ohms. If you're inquisitive or fussy about 2 channel music then you could try the 8 ohm setting to see if you hear (or think you hear ) any difference.