Testing for a blown speaker?

[Newc]

Aside from cranking the amp to the max and listening for any unwanted fluffle, how do I test a speaker to see if it's blown?
I heard once that you can stick a 9volt battery on the terminals, but not sure how it's done or if it's accurate?

[jackson1]

If you can get to the front of the speaker... gently press the cone inwards and release. Listen for noise while doing so repeatedly. If you hear noise (scraping) there's a problem. Probably a burnt coil wire hitting the sides of the magnetic gap = replace unit.
Use all 5 fingers to press the cone down as centered as possible. Only press down half an inch or so.

You could also measure the unit with an ohm meter. An 8 ohm labeled unit should read 6 ohm or so on the ohm meter.

Finally, you can do the battery test, but it will itself make noise due to the DC being applied. If the cone doesn't move when a 9v battery is applied (shortly), its coil wire is damaged and the speaker need to be replaced.
Disconnect the speaker completely from the amp. Connect the battery + terminal to the speakers + terminal (red). Then hold the wire from the battery - terminal in your hand and SHORTLY connect it to the speaker - (black/blue) terminal. Just hold it there for 1 second or so and then release. Watch the cone. It should move slightly (outwards when battery is applied).

[Firebird V]

Well said.

[micha]

You could also measure the unit with an ohm meter. An 8 ohm labeled unit should read 6 ohm or so on the ohm meter.

interesting... so where did the other two ohms go?
is it some kind of inductive-resistance not measurerd on the ohm-meter?
I've been wondering that too, lately...
do you also know what a 16 Ohm speaker should measure?
thx!

[siggy14]

Basically when you are using a ohm meter you are measuring resistance, not inpedence which is actualy what a speaker is rated in. However measuring the resistance is a good way of getting a rough idea.

A 16 ohm speaker should measure between 12.5 and up to 16 ohms on a meter, just depends, like all things, not all speakers will be exact and you will get a rare way out of spec speaker sometimes.

But the most common would be roughly around 13 Ohms it should read for a 16 ohm speaker, and about 7 ohms for a 8 ohm speaker

Another way of testing a speaker cabinet to see if there are any blown speakers is to use a very clean channel on a amp, crank it up, if you hear rattleing or distortion then something is not right.

interesting... so where did the other two ohms go?
is it some kind of inductive-resistance not measurerd on the ohm-meter?
I've been wondering that too, lately...
do you also know what a 16 Ohm speaker should measure?
thx!

[Newc]

Thanks. Looks like the speaker in question (Roland MicroCube) is good - 4 Ohm speaker reads 4.4 Ohms.

The replacement I ordered for it (Celestion TruVox) reads 7.1 Ohms (rated at 8 Ohms).

Maybe if I didn't run my pickups so close to the strings, and turn the Gain down on the Clean channels?

[jackson1]

Huh? The speaker is good yet you ordered a replacement? I'm probably dense...

[Newc]

I didn't test the speaker first (doh!). I assumed the little farty noises it was making was because it was blown, so I went ahead and ordered a new one.

Yes, I'm backwards that way

[jackson1]

Good job, Newc!