I did the math.  $272.00 is too much.

i used a multimeter 5 years ago... my cheap JL audio w0 and rockville amp have done an amazing job since.

Stopped by local shop here just to find out where my deck maxes out, The guys told me they were backed up for a month and it'd be like $100 to do it.  crazy. So now I've got the O scope

Long story short: do a multimeter if you understand rms and use it instead of numbers you just see. Use an oscilloscope if you're pushing the maximum possible waves.

Kicker amps all have a chart online with specified voltage reading, specific volume to have radio on and even has a free audio clip which plays the specific hertz needed for proper gain settings with a Multimeter. Gotta love kicker

This video sounded like a sales pitch for a fancy equipment 😂

The 75% rule is good if you dont know the output voltage for the head unit, but if you know the preout voltage from the datasheet, you can measure that on the RCA cables in AC on the center pin and the shield. Turn it down just a smidge when its at the target voltage.

Then you hook up the head unit to the amplifier, and match the input voltage with the output voltage of the head unit. You can do this by reading the datasheet from the amp manufacturer, and it should have a place it says Input voltage, usually something like 0-4/5v. Then adjust the gain knob for gain, until its in the area of the output voltage for the preout. The simplest way for this is to divide the gain into percentage, so for 5 its easy, each volt is a 20% increment. Again, adjust it down just a smidge to be safe. This allows the amp to run at full juice at max volume without clipping.

If you want to match the RMS of the speaker, to the output of the amplifier, complete step 1 to find the unclipped voltage of the head unit, then use the math method of sqrt(Watt*Ohm) of the speaker, to get a rough estimate of the voltage you need to set. Play a 40hz/1k test tone, and set the voltage to around that, and then turn it back just a smidge.  

After this you should be golden, no distortion, no speaker blown and happy days!

If you have no multi-meter, reset the amp gain, turn up the head unit to max, listen for distortion and turn it down until its gone. Then turn up the amp gain to max excursion for the speaker, or until it distorts, then bring it back down until it doesn't and you're golden (Less accurate method though, even compared to multi-meter)

My buddy Justin just showed me how to set my gains with a multimeter a few years ago!

I use a below $50 oszilloscope and it works fine. A more expensive one would hopefully have some more auto-adjustment to see automatically a wave or two of the actual voltage and frequency, but it works manually as well.

I love how you circled back on this topic. Great info.

I can't remember the last time I bought an amp that didn't have a clip indicator on it. Also up sizing the amp a little from the rms actually needed is a good way to stay away from clipping.
As far as the "75% rule", you use the oscilloscope to see where the head unit clips.

Thank you, I was able to use the multimeter to verify gain against the built in light on Key 500.1, worked perfectly

Most people will confuse voltage with power not knowing you're talking about the RCA voltage. Welcome to the world of car audio.

Love your video's! very easy to listen to and understand.  I do think i need to get you DD-1+ for Christmas. It's a lot more to that than i think you realize :).    FYI: If you want to know how much power your amp is actually presenting to a sub, we have the AMM-1.  Not trying to push my stuff on your channel my brother, sorry. I'm just sayin' we have something for everything.  Also, i would like to point out that there is a lot more to setting gains than just watching for a light or watching for the wave form to start clipping.  Whether it is a DD-1 or an O-scope, the proper procedure when using them should be talked about (because there is important  things like gain overlap to consider).  I almost ALWAYS tell people to buy and learn how to properly use the scope first and then there is no way they won't like the "upgrade" the (i won't say it because i ain't trying to spam your page with my product haha!)  Thanks for the mentions! Watch for an email!

sound clips didn't give me a jumpscare on this video.  i believe one day we can add limiters on old youtube videos.  i have an old hamburger phone video that has audio that makes me cringe really bad whenever i watch it.  

thanks DIY Audio Guy.  your videos are most effective in helping me learn about audio amplifiers.

Thank you.  Just bought an Abestop Oscilloscope. New to checking anything electrical. Normally read manuals buy what seems right, connect,  power on and go.

I appreciate you making this update vid, but I’ve been using your metod every since I watched that video and I haven’t had any problems! Although I have noticed that with amps that have a clip light, after setting gains with multi-meter it will clip and I’ll have to turn it down just a little bit. Anyways, thank you, I’ll look into an O-Scope! 💪🏽

This is one of the main things that I have preached for YEARS. I bought my first o-scope for $25 on amazon. There is never ever any reason to just out right guess at gain settings.

After a life time of doing my own subwoofer set ups, i always did it by ear... recently used a meter for a bew AMP and boy was that a mistake. My super reliable 16 year old MTX terminator dual 12 inch subs burned out.

Picked up a scope for 40$, should be good to go now!

I admire your honesty and transparency!! You're my new hero!