Understading ohms :)

[Fetchez la vache]

I've just bought an amp and was hoping to use some old speakers with it - at least until I can justify the cost of some new speakers (this is for a flat and not the main house hi-fi).

The amp states "ensure they have an impedance of between 4 nd 8 ohms".
The speaker impedance is 3 ohms.

Can I use them or am I risking something going pop?
Many thanks

[Plotloss]

Using a speaker which is rated outside the 'stable' ratings of your amplifier whilst not advised at normal listening volumes will probably be fine.

The lower the impedance rating of the speaker, the more sound will be produced for each watt, meaning that the amp will be working harder with a lower impedance rated speaker than it is rated to drive so you'll be operating outside its 'safe' parameters.

It'll get warmer than usual but if you keep the volume down you shouldnt experience clipping or meltdown...

[DavidY]

To drive a lower impedance the amplifier must generate more current, and therefore needs a more manly power supply.

If the amplifier states ensure they are between 4 and 8 ohms then I suspect that it is not a powerful current driving amplifier and would struggle seriously at decent volumes with anything less than 4ohms.

Most speakers do not have a flat impedance response against frequemcy, my speakers dip below 2ohms at one point in their frequency response.

There is a good chance that at low volumes everything will be fine, but unless you are comfortable that if something blows up/catches fire/etc, I personally would just go any buy a suitable pair of speakers. I don't know what amp it is (or speakers) but you can pick up decent budget used pairs of speakers from eBay for less than £30. So what's it worth to you?

davidy

[Fetchez la vache]

Ah right, ok thanks for the replies
I wouldn't mind so much the speakers going, but I'm not sure I want to stress the new amp.

Its not an expensive one by any means - a Fatman iTube carbon, but it does sound like some speakers are on the cards - dont want my new shiny valves going pop.

Thanks

[DavidY]

If you want some good ones s/h then I'd suggest a pair of Morduant Short MS10i's (a great little loudspeaker) There were two later ersions as well MS10i Pearl and MS10i Classic. At one time I've all three versions (still have the Classics in my wife's studio) and they are a cracking little liudspeaker. Appear quite often on eBay (but the MS10i's on there at present are a bit rough!). Expect to Pay £30ish for MS10i's, £50 for Pearls and £70 for Classics.

Hope that helps

davidy

[telecat]

Not only do you need to look at the Ohms but the DB rating. Valve amps tend to prefer the more efficient Speakers designs. These are 90db and above.

[DavidY]

Thats a fair point, however that statement would certainly be true for Low Power Valve Amps (The Fatman's quite beefy in valve terms for a low cost valve amp at 28W per channel)

Fatman's own speaker is only 85db sensitivity, so they must be fairly confident of generating reasonable volumes from their systems. This gives the OP quite a range of potential speakers. I still reckon the MS10i's would be a good match (especally for rock/pop music) and especially the Classics which were £300 when new.

davidy

[PJR]

Valve amps are not generally tolerant of extreme impedance variations. So personally, I wouldn't risk your old 3 ohm boxes with it.

P,

[cjs]

3 ohms is a very strange impedance, does it say 3 ohms on the speaker or are you using a meter to measure?

[Technonotice]

My old AV amp(6-8omhm rating) worked fine with my 4 ohm speakers. The amp just turned it self off at very high volumes and required you to turn it off at the wall to reset it. I assume it was getting too hot or the ps couldn't handle it. It worked for years and never did any lasting damage. In fact I bet its still working in my mates house.

• disclaimer

I am no way responsible for you breaking your new fancy amp.