Setting gain on amp with over head

[Booming]

So I think I know the answer, but I'd like to see what other options there are for setting the gain on an amp that is about 1.2k-1.5k more power than I'll need for my sub. I think I can just set it with a DMM but are their other ways to do it? I am assuming a scope is out because that'll just tell me if the signal is clean, which I'm pretty sure with it dialed back this far it should be a clean signal.

Any help would be greatly appreciated.

* The amp is an AA 3800.1 and the sub is a custom built 12" GCA Destroyer from Joseph Smith (with GCA)

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[adulbrich 5,000+ posts]

You could set it with a scope and make sure it is a clean signal, then turn it down as much as you want from there. Subs are a reactive load and (most) music is not constant sine waves, so there is no way to dial your amp down a specific wattage.

After impedance rise and voltage drop, your sub won't see all that power anyways

 

[Booming]

You could set it with a scope and make sure it is a clean signal, then turn it down as much as you want from there. Subs are a reactive load and (most) music is not constant sine waves, so there is no way to dial your amp down a specific wattage.
After impedance rise and voltage drop, your sub won't see all that power anyways

But if I set it to "full" power you're saying box rise will mean I shouldn't see "full" power, but wouldn't setting it with a DMM to say 2.5k insure that is the high threshold of the power I will ever see?

 

[adulbrich 5,000+ posts]

But if I set it to "full" power you're saying box rise will mean I shouldn't see "full" power, but wouldn't setting it with a DMM to say 2.5k insure that is the high threshold of the power I will ever see?

Depends on what tone you set gains with. If you play music recorded at 0 db and set your gains with something like -12, you will see spikes of higher than 2.5k

 

[Booming]

Depends on what tone you set gains with. If you play music recorded at 0 db and set your gains with something like -12, you will see spikes of higher than 2.5k

So there really isn't an end all "best practice" for doing this?

 

[adulbrich 5,000+ posts]

So there really isn't an end all "best practice" for doing this?

You can set it with 0 db and be fine with most stuff, but you won't get the most out of your amp on music recorded lower.

I don't know if there is a "best practice" per say. There are lots of methods. I'd just set by ear and not worry about it. Be smart and use your ears

 

[Booming]

You can set it with 0 db and be fine with most stuff, but you won't get the most out of your amp on music recorded lower.
I don't know if there is a "best practice" per say. There are lots of methods. I'd just set by ear and not worry about it. Be smart and use your ears

My ears are as good as they used to be //content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif but I guess that sorta answers my question. Thanks (unless anyone else wants to toss there $.02 in)

 

[trumpet 5,000+ posts]

It's still a good idea to examine the waveform with an oscilloscope. The 0 dB tone suggestion is good, but really there is no way to know without listening for the sub bottoming out or smelling it getting hot to know if it's too much power being delivered. I'm guessing with this kind of system you're not usually listening to jazz, so this amount of headroom could cause serious damage. An inline gain knob could be useful to quickly cut back the input voltage and reduce the power.

 

[Booming]

It's still a good idea to examine the waveform with an oscilloscope. The 0 dB tone suggestion is good, but really there is no way to know without listening for the sub bottoming out or smelling it getting hot to know if it's too much power being delivered. I'm guessing with this kind of system you're not usually listening to jazz, so this amount of headroom could cause serious damage. An inline gain knob could be useful to quickly cut back the input voltage and reduce the power.

Not much Jazz...lol But I will be running the knob for that reason!

 

[n2audio 5,000+ posts]

This isn't rocket science.

Do it by ear.

Turn the gain to min.

Put in a song with some bass you like.

Turn the HU way up.

Set the x/o to a reasonable base value (80hz?).

Slowly increase the gain until the sub sounds like it's struggling.

I've never owned a scope and I've never blown a sub -- except the 250w pyramid I plugged into the wall.

 

[keep_hope_alive Premium Member]

Playing music isn't going to be a good reference because signal level various by song. Simply match input sensitivity (gain) to head unit output voltage. That's it. With that method, the amp will never cause clipping. But rated power is only achieved with head unit on max and a peak in the recording.

Other methods attempt to achieve rated power at lower head unit volumes. Then the previous comments are applicable.

Feel free to shoot me a PM.

Sent from mobile device.

 

[Booming]

Playing music isn't going to be a good reference because signal level various by song. Simply match input sensitivity (gain) to head unit output voltage. That's it. With that method, the amp will never cause clipping. But rated power is only achieved with head unit on max and a peak in the recording.
Other methods attempt to achieve rated power at lower head unit volumes. Then the previous comments are applicable.

Feel free to shoot me a PM.

Sent from mobile device.

But I'm trying to prevent doing rated power because I know the sub can't handle the amps rated power. I'm trying to set the amp under rated power and keep it around the subs rated power.

 

[Jeffdachef 5,000+ posts]

So there really isn't an end all "best practice" for doing this?

http://www.caraudio.com/forums/advanced-sql-spl-discussion/613379-best-way-tune-your-enclosure-set-gains-based-your-music-library.html

Or do it N2audio's way, a little common sense goes a long way. You need to do 5 to 10 minute full blast tests afterwards to see the heat levels of your system and the voltage drops you are getting. Back it off some more if you do run into problems with either of those.