Boogie Posted January 22, 2009 Share Posted January 22, 2009 I Have a set of monitors made by a company called 'classics pro audio' CPA from the 1990s in London - they are passive – 12 inch speaker – with a tweeter. How do I tell what ohms they are and the amount of watts they will put out – I have looked on the back / side – and they have no markings what so ever – anybody got any ideas. Link to comment Share on other sites More sharing options...
mackerr Posted January 22, 2009 Share Posted January 22, 2009 You could measure them with an impedance meter, but not that many people have one. The other option is to measure them with an ohm meter to get the DC resistance, and understand that the impedance at audio frequencies will be higher. It is common to see an 8 ohm speaker measuring at 6 ohms for instance. Speakers do not put out watts. The consume watts if anything. The wattage rating on a speaker is the maximum power they should be driven with. You will rarely reach that power as audio is by its nature variable in level, hence variable in voltage and power. You can use as big an amp as you please as long as the average (depending on how the rating was done) power doesn't exceed the rating. It is often easy to know when you have crossed this boundry because things start to sound bad. If you turn it up loud and it starts to sound bad, you have turned it up too much. Mac Link to comment Share on other sites More sharing options...
mostlyharmless Posted January 22, 2009 Share Posted January 22, 2009 Again, measure the resistance- then round upto the nearest sensible number. eg 6.2ohms is likely to be an 8 ohm driver. To work out the power rating, connect a volt meter in parallel, and using V=IR and P=IV , work out the power "wattage" you are currently driving the speaker with. Keep turning it up playing broadband noise, and at the point it stops working is its power rating. (well, techically its power rating is a level it can sustain for 100hours).However, I wouldn't advise this if you wish to continue using the speakers. Link to comment Share on other sites More sharing options...
AndyL Posted January 23, 2009 Share Posted January 23, 2009 I Have a set of monitors made by a company called 'classics pro audio' CPA from the 1990s in London - they are passive – 12 inch speaker – with a tweeter. How do I tell what ohms they are and the amount of watts they will put out – I have looked on the back / side – and they have no markings what so ever – anybody got any ideas. Open the box/take the drivers out, see if there are any markings on the backs of the drivers, e.g. Make, model, impedance. If there are, google away! Most loudspeaker manufacturers (especially the small ones, but even some very big ones) do not make there own drivers but buy them in from a smaller number of loudspeaker component manufacturers so that although the company which made the boxes may not be around any more there is a better chance that the driver manufacturers will be. Link to comment Share on other sites More sharing options...
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