Checking amp volts

[OrionStang]

Why is it neccessary to disconnect the subwooofer speaker wires from the amp before checking output with a DMM?

[alan412]

Why is it neccessary to disconnect the speaker wires from the amp before checking output with a DMM?

are we talking door speakers or subwoofers?

[OrionStang]

Subs. Sorry bout that.

[esteagall]

i never even knew you had to disconnect the speakers before checking output

[OrionStang]

i never even knew you had to disconnect the speakers before checking output

When setting the gains on the amp, disconnect the speaker wire and attach the DMM to the corresponding pos and neg. You never heard this?

I just want to know why its always suggested.

[alan412]

When setting the gains on the amp, disconnect the speaker wire and attach the DMM to the corresponding pos and neg. You never heard this?

I just want to know why its always suggested.

so you aren't listening to a 45 hz tone at full volume night next to your dome. lol

[kirill007]

so you aren't listening to a 45 hz tone at full volume night next to your dome. lol

x2

So you wouldn't blow the woofer while you're setting you're gains.

[Lowroll]

So you wouldn't blow the woofer while you're setting you're gains.

Thats word for word what I was gonna say. I left the sub hooked up in my girls truck & it was pretty loud right next to my ear but it was also clipping like hell & it took a good 10 or 12 tries to get it set right. It smelled like coil so bad.

[Nightshade]

It depends on what you are trying to do. If you are setting the gains then yes you need to disconnect the speaker wires going into the amp and probe the terminal with the dmm and setting to ac voltage.

Now if you are trying to measure output to calculate for power then no you need to leave the speaker wire connected. Still set the dmm to ac voltage, but also have an ac clamp meter around the positive wire. Assuming that it's a mono block amp you will only need to meter one set of wires going from amp to subs for accurate power. If it is a multi channel amp then you need to probe all + and - wires for ac voltage as well as clamp all + wires going to the speakers for ac amperage.

To find the power you multiply the ac voltage by the ac current to get the power in watts. To find what your impedence has rose to divide the ac voltage by the ac current.

Hope that answers your question