Can you test for power

[JAL232 10+ year member]

so with system being OFF, It will still show some kind of ohms, with no power?

 

[Flipx99 5,000+ posts]

Yes.

 

[johnson 10+ year member]

so with system being OFF, It will still show some kind of ohms, with no power?

Yes.

DISCONNECT THE SPEAKER LEADS FROM THE AMP to avoid any possible damage.

 

[Flipx99 5,000+ posts]

Wanna see something interesting...measure the resistance of the speaker free air.

Then move the cone. The number will change.

 

[tRidiot 10+ year member]

Ahhh

 

[Flipx99 5,000+ posts]

Ahhh

Is that not true or is my DMM busted?

 

[tRidiot 10+ year member]

Wanna see something interesting...measure the resistance of the speaker free air.Then move the cone. The number will change.

Naturally... as the voice coil moves inside the magnetic gap, the change will register as a change in impedance.

You can take a speaker sitting outside the box, hooked to nothing and measure impedance on a voice coil. That's essentially why we want you to disconnect it from the amp. Looky here:

http://www.beachdocs.com/pics/JL%208IB4%20004a.jpg

 

[Flipx99 5,000+ posts]

Can you measure resistance/impedance while the sub is being powered?

 

[tRidiot 10+ year member]

Can you measure resistance/impedance while the sub is being powered?

Sure... but it's gonna be constantly changing.

You trying to test me or something? I find it hard to believe you don't know the answer to these questions, Flip...

 

[Flipx99 5,000+ posts]

I have a good "general/practical" knowledge, but specific things I don't know...Plus 60% of my posts are in the lounge. I know enough to not break things, but not enough to say I know what I am talking about.

No, what I am doing would be testing...say for SPL.....

on a test tone, knowing the impedance at a specific frequency would be very valuable....and valueable to me in bass race.

 

[Decado2 10+ year member]

Indeed....
I don't even bother changing the batteries on my DMM.... I just toss it and buy a new one. //content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif

LOL

 

[JAL232 10+ year member]

Yes, they are 4ohm svc..I have them wired to 2 ohms buy: positive from one sub to positive to next sub to pos. on amp...same for negs...

So if i test the speaker terminal tonight for ohms and i dont get anythign or i get a very high number my vc is more than likely shot? Dont know how it would have done this..

 

[tRidiot 10+ year member]

I have a good "general/practical" knowledge, but specific things I don't know...Plus 60% of my posts are in the lounge. I know enough to not break things, but not enough to say I know what I am talking about.

No, what I am doing would be testing...say for SPL.....

on a test tone, knowing the impedance at a specific frequency would be very valuable....and valueable to me in bass race.

Well then certainly, yes you can test impedance at a given freq, if you're playing a test tone or sine wave. I've never done this either, but I know it's possible. They talk all the time about this stuff over on termpro. The impedance of a given sub at a given freq depends also on the enclosure (they call it 'box rise'). In other words, seldom if ever does an amp actually "see" the impedances we talk about when we say we've wired our subs to 1 ohm or .35 ohms or whatever. It's usually somewhat higher, can be DRASTICALLY higher, and changes with every frequency. It also changes with the temperature of the coil, and I believe end atmospheric pressure and humidity can have some effect on it.

I couldn't tell you how to accurately measure 'box-rise' or anything like that, though, it's definitely out of my realm of experience. Termpro would be the place to go for that kind of info, I'd think.

 

[tRidiot 10+ year member]

Yes, they are 4ohm svc..I have them wired to 2 ohms buy: positive from one sub to positive to next sub to pos. on amp...same for negs...
So if i test the speaker terminal tonight for ohms and i dont get anythign or i get a very high number my vc is more than likely shot? Dont know how it would have done this..

Ok, the way they're wired could help us....

If you measure it and it's between 3 and 4, I'd guess your far speaker is shot. If you get an extremely high reading, I'd guess your near speaker is shot. With no reading or an incomplete circuit, then I'd guess something came loose in the wiring inside the box.

These are just guesses.

If you get a reading between 1 and 2 ohms, I'd say most likely the speakers are fine.

 

[tRidiot 10+ year member]

Yes.
DISCONNECT THE SPEAKER LEADS FROM THE AMP to avoid any possible damage.

I don't believe it would hurt anything testing impedance while the amp is on. Long as you don't start connecting/disconnecting wires while it's powered. You're simply measuring.