Checking a speaker

Jerry Roller · Post by **Jerry Roller** » 7 Dec 2002 10:01 am

Would one of you electronics guys tell me how to check a speaker without taking a chance on damaging an amp if the speaker is shorted out?
Thanks,
Jerry

Jim Smith · Post by **Jim Smith** » 7 Dec 2002 10:54 am

The way I've always done it is to hook up a 9-V battery to the terminals. If the speaker is working you'll hear a noise plus you can check the phase of your wiring. When the + of the battery is connected to + on the speaker, it will push the cone out.

If you want to hear music through the speaker, just hook into the earphone jack of a boombox.

Stephen Gambrell · Post by **Stephen Gambrell** » 7 Dec 2002 4:42 pm

I don't know if this works for everybody, but I disconnect the speaker and push the cone in and out. If it makes a static-y noise, it's bad. Don't know what causes this(HELP, KEN!!) but it's always worked for me.

Ken Fox · Post by **Ken Fox** » 7 Dec 2002 6:00 pm

Steve's method is pretty good. Some speakers have tight voice coil gaps, so you must be careful to push evenly or a good speaker will rub. If a speaker is short out it will read "0" ohms on the ohmmeter. If you don't have an ohm meter the 9 volt battery test as stated aboove is pretty valid. If the speaker make a thumping sound and moves a bit it is likely not shorted.

Terry Downs · Post by **Terry Downs** » 7 Dec 2002 6:33 pm

I use a 6.3V filament transformer. If you can find a wall wart (wall transformer) with a 4-9 volt AC output, just cut off the plug and either put on a 1/4" phone plug or clip leads to connect to the speaker under test. Make sure the wall wart is an AC output. DC will just cause the speaker to pop. The AC transformer will make the speaker output a 60Hz tone.

Regards,
Terry

Terry Downs · Post by **Terry Downs** » 7 Dec 2002 6:52 pm

Here is a 10VAC adapter that will give your speakers under test a 12.5 watt workout.

http://www.allelectronics.com/cgi-bin/category.cgi?item=ACTX-1024

Ken Fox · Post by **Ken Fox** » 7 Dec 2002 6:54 pm

Good one, Terry! We used to use 24 ac transformers on 25 volt, commercial speaker lines (schools and other paging applications) to ring out speakers! I had forgotten about that. Be careful if you use a class 2, wall wart, one short and they blow instantly! An inline fuse holder and fuse can be used. For a 6.3 transformer you are at about 5 watts of power on the speaker. That's about 1 amp of current. A 2 amp fuse in line would be a good idea. The NEC requires class 2 transformers to be current limited and they blow immediatley on a short circuit! A good example of a Class 2 transformer is a household bell transformer (typically 16 VAC at 10 VA). A filament transformer is not Class 2 and will not have any current limiting built in.

Terry Downs · Post by **Terry Downs** » 9 Dec 2002 4:43 pm

Very good point Ken.