ohms, amps

Hey, this isnt really car related at all but im sure one of the experts on here will know,

parents want 2 other speakers hooked up to the hifi downstairs and the speakers/amp is rated 2x40w rms at 6ohms, is it possible to hook up 100W speakers rated at 8ohm? its only for one nite temporary to get the sound to another room. what would the effects be if i did this? could i blow the amp? or the speakers? or would the sound just be lower? i do also have 6ohm speakers but not as good quality!

Please help!

Thanks guys

adz

oh, also, ive bought a 2-ways stereo speaker contol box to switch the speakers on and off independantly - http://www.maplin.co.uk/module.aspx?detail=full&ModuleNo=29752&doy=31m1#more_info

and upon reading the technical info on the box it says do not use speakers less than 8ohms?

why would this be? one pair is 8 but the other is 6! am i going to kill them? ive just tested it and it seems to work fine with no problems.

adz

I was kinda wondering if you were going to wire up the 8 ohm speakers and the 6 ohm to the reciever. If only one pair OR the other were to be wired to the reciever it should be fine and the higher resistance ones will not allow the amplifier to put out as much power as the lower resistance ones HOWEVER if you are wanting to use the switch box you linked to, from what I can tell it is paralleling the speakers to the amplifier. It says the minimum load seen with all 8 ohm speakers is 4 ohms and that sounds like parallel wiring. A lot of recievers will not like this load as it is too low.

What you might want to do is buy a better selector box that is impedance compensating in that with 1 pair, 2 pair, or 3 pair of speakers the load will not go below the resistance of your lowest one which should be 6 ohms (as that was what was on it before with no ill effects). The better boxes will keep the load up that the amplifier sees so it doesn't overload it or burn it up from too low of a resistance.

Another option if the speakers are in another room is to wire in volume controls that are impedance compensating.

Jim

so i shouldnt really use this switch box? it dint seemed to cope fine. tested for around 10mins thought. unless i just daisy chain the speakers and forget about the switch box?

adz

I was just going off what I read and came to a conclusion. The only way to know would be to hook up the speakers to the switch box you linked to, turn both of the speakers on with the switches and then measure across the input terminals of the box to see what it reads without it connected to the reciever. If the resistance is down from having both speakers being paralleled then the reciever MAY not like it. If the switch box series wires the speakers then the reciever should like the load. I've seen it too many times with manuals not being correct too or people buying things they think will work a certain way only to have it work another way.

I've seen all kinds of equipment come through the shop I work with for repair and some home units are touchy with what load is hooked up to them. I just don't want to see something get burned up or have problems with it from using the wrong part(s) or wiring something incorrectly.

If you really think about it a speaker advertised as an 8 ohm speaker might only show that resistance at one frequency and above it or below it the reistance can vary maybe down to 6 or 7 ohms and possibly rise to 20 ohms or more. If an amplifier cannot handle these variables then bad things can happen.

Jim