Understanding OHMs has hurt my head! HELP

[knokinnakamichi 10+ year member]

Lol, everytime someone posts an Audio Shop set their gains, they say that they turned it up until they could hear distortion then turned it down a little and said "your good"

Exactly!

 

[knokinnakamichi 10+ year member]

The articles told you to move around your gain aimlessly? You need to set it correctly. Either take your vehicle to an audio shop and pay them to use an oscilloscope, or buy a digital multimeter and set them that way. Your amp might be overworking itself, hence the extra heat. But remember, the metal casing around your amp isn't just to protect it from a beating. It is supposed to absorb the heat, moving it away from the circuit board.


Exactly. 4 ohms = 4 ohms. What's the problem?

No problem, I got it now! TY

But, it may seem I moved it around aimlessly from the explanation, but you weren't there and this wasn't the case...however, even if I got a DMM I wouldn't know WTF I would be doing.

 

[VisceralSound 10+ year member]

No problem, I got it now! TY
But, it may seem I moved it around aimlessly from the explanation, but you weren't there and this wasn't the case...however, even if I got a DMM I wouldn't know WTF I would be doing.

Get a DMM and a (IIRC) 50hz test tone.

do the math here:

(rms*ohms)=x

Square root of x = (Number)

Play the test tone at the maximum volume without distortion and hook the leads up to the +/-

with all your EQ's/Bassboost off turn the gain up until you reach that number, and your good.

 

[knokinnakamichi 10+ year member]

Get a DMM and a (IIRC) 50hz test tone.do the math here:

(rms*ohms)=x

Square root of x = (Number)

Play the test tone at the maximum volume without distortion and hook the leads up to the +/-

with all your EQ's/Bassboost off turn the gain up until you reach that number, and your good.

Last moronic question of the night...is this for the combined subs? or each one individually? I would be looking for 37.4 ish then?

 

[MisterDeadeye 10+ year member]

No problem, I got it now! TY
But, it may seem I moved it around aimlessly from the explanation, but you weren't there and this wasn't the case...however, even if I got a DMM I wouldn't know WTF I would be doing.

If your subs had dual voice coils, or if you were wiring the subs to the same channel, it would be different. Because you're wiring them separately, there's no need to worry about the load.

Using a DMM to set your gains isn't perfect, but it's incredibly simple.

1. Get a test tone(either on here, or somewhere else)

2. Put it on a CD, iPod/MP3 player, etc.

3. Play it on your headunit

4. Turn up your volume to the highest you'd possibly listen(or even higher if you want to be really safe)

5. Set your DMM to Volts through an AC, and put the leads on the speaker output of your amp

6. (This should actually be done first... Forgot to put it up there, and I don't feel like transposing the numbers) Calculate the voltage you need. It's done this way: sqrt(power*impedance), power being the wattage you plan on giving your subs(usually the RMS rating of your amp or sub, whichever is lowest), resistance being the nominal impedance of your sub. So in your case, you'd be looking at 350W RMS for your 4 ohm subs. sqrt(350*4) = sqrt(1400) = 37.4166. Your DMM would likely only be as accurate as one decimal point, so you'd want to try to get 37.4 Volts AC from your amp.

7. Then just move the gain knob until you get 37.4 V.

The real problem is that there are many variables that need to be taken into account when calculating your actual power, which is the most important part in setting gain. An oscilloscope allows you to actually see when the amp is clipping.

 

[MisterDeadeye 10+ year member]

Last moronic question of the night...is this for the combined subs? or each one individually? I would be looking for 37.4 ish then?

Your amp should have a separate gain knob for each set of channels, so you'd want to set each one individually.

 

[knokinnakamichi 10+ year member]

If your subs had dual voice coils, or if you were wiring the subs to the same channel, it would be different. Because you're wiring them separately, there's no need to worry about the load.
Using a DMM to set your gains isn't perfect, but it's incredibly simple.

1. Get a test tone(either on here, or somewhere else)

2. Put it on a CD, iPod/MP3 player, etc.

3. Play it on your headunit

4. Turn up your volume to the highest you'd possibly listen(or even higher if you want to be really safe)

5. Set your DMM to Volts through an AC, and put the leads on the speaker output of your amp

6. (This should actually be done first... Forgot to put it up there, and I don't feel like transposing the numbers) Calculate the voltage you need. It's done this way: sqrt(power*impedance), power being the wattage you plan on giving your subs(usually the RMS rating of your amp or sub, whichever is lowest), resistance being the nominal impedance of your sub. So in your case, you'd be looking at 350W RMS for your 4 ohm subs. sqrt(350*4) = sqrt(1400) = 37.4166. Your DMM would likely only be as accurate as one decimal point, so you'd want to try to get 37.4 Volts AC from your amp.

7. Then just move the gain knob until you get 37.4 V.

The real problem is that there are many variables that need to be taken into account when calculating your actual power, which is the most important part in setting gain. An oscilloscope allows you to actually see when the amp is clipping.

So, if I take it to a shop and ask to borrow an oscilloscope, how would I use that?? Otherwise, how much is a RMM? If I wanted to be safer would I go for a lil lower or lil higher reading?

Also, why is it better to leave everything flat on the HU (i think I understand)?But, I'm proposing here that if one wanted to take less off the amp couldn't you set the gain on the HU and therefore not need to set the gain on the amp-or does this cause clipping?

PS love the sig pic....where did you grab that?

 

[VisceralSound 10+ year member]

So, if I take it to a shop and ask to borrow an oscilloscope, how would I use that?? Otherwise, how much is a RMM? If I wanted to be safer would I go for a lil lower or lil higher reading?
Also, why is it better to leave everything flat on the HU (i think I understand)?But, I'm proposing here that if one wanted to take less off the amp couldn't you set the gain on the HU and therefore not need to set the gain on the amp-or does this cause clipping?

PS love the sig pic....where did you grab that?

Easiest method versus having to go out to your local audio shop, just buy a DMM for $20.00 and follow our steps.

 

[knokinnakamichi 10+ year member]

So, say I set my gain properly but then I'm listening at a lower volume and want to turn up the sub via the HU to get something extra, will this cause clippings, problems, etc???

 

[trumpet 5,000+ posts]

http://forum.sounddomain.com/ubbthreads.php/ubb/showflat/Number/65167/page/1

scroll down to post #1294233 by keep_hope_alive

Do this.

 

[DonH 5,000+ posts]

Since when did gain and ground become plural for one amplifier? That crap bugs me. Op check the gain on the amplifier. If it was a ground issue his amp would be turning off.

 

[knokinnakamichi 10+ year member]

Since when did gain and ground become plural for one amplifier? That crap bugs me. Op check the gain on the amplifier. If it was a ground issue his amp would be turning off.

Yah, hence my confusion.....with that post!! I'm not one to call another a moron, but.......

 

[CHEMMINS 10+ year member]

Go get a SMD DD-1 and follow the directions......./thread.

 

[knokinnakamichi 10+ year member]

Hey, thanks all. I'll let you know what conclusions I get

 

[DonH 5,000+ posts]

Also, you might be asking to much of the amplifier you have now. Understand that a class a/b amplifier will run hot. Some can get extremely hot but still function. You wont blow the amplifier if it has a good thermal protection in it. Most cheap amplifiers thermal protection wont kick in untill its to late. A good idea would be to educate yourself on how to properly set an amplifier like previously stated. An o-scope is not necessary by any means if you have a good amplifier. If you want a great little class d amp pm me i may be able to push you in the right direction