Low voltage to speakers?

[chaseincats]

Hi guys,

I just noticed when replacing my speakers that the voltage going to the speakers themselves is very low.  I used a test light and the light that shines from the left and right speaker power wires is very dim.  I tried using a multimeter for an exact reading but I must not be doing something wrong because it's reading basically 0.

Is the speaker voltage stepped down from 12v or are they supposed to be getting a full 12v?

Edited March 21, 2023 by chaseincats

[Captain Obvious]

Couple things... First, it's not DC, so if you're using a meter set on DC, you won't see anything. Then next, if it's music, it's a whole bunch of frequencies all mixed together up to about 20KHz. So even if you have a meter set on AC, it might not recognize frequencies that high.

And finally, the voltage peaks will be proportional to how loud the music would be. So trying to make some sort of "portable scale" to measure things... If you've got a 20W system turned all the way up, it would/could/should? light a 20W bulb to a reasonable brightness. But if you've got the volume turned down to a reasonable listening level, the brightness will be way lower.

Not sure I'm doing a good job of explaining this... Does any of that make sense?

[chaseincats]

That does and since I had the volume at a mid level, the bulb being half-lit makes sense then.  Thanks

EDIT: Why wouldn't setting the multimeter to DC work though?  Doesn't the car run off of DC power?

Edited March 21, 2023 by chaseincats

[SteveJ]

What exactly are you trying to do? It sounds like you're looking for a non-existent problem.

[dutchzcarguy]

7 hours ago, chaseincats said:

EDIT: Why wouldn't setting the multimeter to DC work though?  Doesn't the car run off of DC power?

Hihi.. As i have worked some time in studio-audio... long time ago.. i find this a funny remark..

CO thanks for the explanation.. it's not a bad explanation.. i wanted to ad: IF you DO measure some DC on your loudspeaker cable.. your amplifier is leaking DC and this kills your speaker if it's a lot.. It also distorts your sound as your speakercone will come to far out of the speakerchassis or if it's a negative DC it wil got to far inside and get stuck..  DC on a speaker is always a very bad thing. 

If you want to get rid of a speaker, put some 200 volts DC on it and look how fast the cone will get out of the unit! 

BTW.. 200 volts AC does the job aswell 😉 

[chaseincats]

3 hours ago, dutchzcarguy said:

Hihi.. As i have worked some time in studio-audio... long time ago.. i find this a funny remark..

CO thanks for the explanation.. it's not a bad explanation.. i wanted to ad: IF you DO measure some DC on your loudspeaker cable.. your amplifier is leaking DC and this kills your speaker if it's a lot.. It also distorts your sound as your speakercone will come to far out of the speakerchassis or if it's a negative DC it wil got to far inside and get stuck..  DC on a speaker is always a very bad thing. 

If you want to get rid of a speaker, put some 200 volts DC on it and look how fast the cone will get out of the unit! 

BTW.. 200 volts AC does the job aswell 😉 

Wow this makes sense.  Basically my speakers kept blowing out after about a year so I thought it was because of the beating they take being bolted directly to the metal of the car so I insulated one with a rubber grommet between the speaker metal and bolt which saved one side but not the other.

So you're telling me that my testlight lighting up when I touched the power wire to the speaker with music playing is bad and can blow speakers even at a low volume?

[SteveJ]

If you're getting a steady medium to bright light off a test light, yes. 

[Captain Obvious]

I'm thinking seeing a light up on the test light might not be a problem. Kinda depends on how the amplifier is designed and where you have the test light connected.

And a test light is different than using a digital meter... The test light doesn't care about DC or AC. All it cares about is average power. So the test light might light up some even if you read zero on your meter on the DC scale.

So how did you have the test light connected? One side clipped to body ground and the other side probing the speaker wires? And if yes, did you probe both speaker wires? What happened?

[chaseincats]

5 minutes ago, Captain Obvious said:

I'm thinking seeing a light up on the test light might not be a problem. Kinda depends on how the amplifier is designed and where you have the test light connected.

And a test light is different than using a digital meter... The test light doesn't care about DC or AC. All it cares about is average power. So the test light might light up some even if you read zero on your meter on the DC scale.

So how did you have the test light connected? One side clipped to body ground and the other side probing the speaker wires? And if yes, did you probe both speaker wires? What happened?

Yep, no DC voltage on the multimeter and a dim bulb on the test light when the clip was connected to the body.  I probed the power wire, not the ground.

[Captain Obvious]

Yeah, I'm not yet convinced some light on the test light is a problem. As for what you're hunting..... Blown speakers? 

First question would be "What's your typical listening volume?"  

[chaseincats]

10 minutes ago, Captain Obvious said:

Yeah, I'm not yet convinced some light on the test light is a problem. As for what you're hunting..... Blown speakers? 

First question would be "What's your typical listening volume?"  

The speakers keep blowing every year or two.  Regarding the volume it really isn't very loud, just loud enough so I can hear them while on the freeway.

I took them out yesterday and the blown one had some rubber insulation or something dangling (it looked kind of like like a rubber band that fit between the cone and magnet).

For the record, these were the speakers that I'd bought twice and blown twice: https://www.amazon.com/gp/product/B00BF6HWF4/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

I got some JBLs this time so we'll see I guess

Edited March 21, 2023 by chaseincats

[SteveJ]

Does the stereo manual specify 4 or 8 ohm speakers?