weird observation with my amplifier.

[Beatin' 10+ year member]

I unhooked the subs and attached the DMM leads on the amp speaker terminals.

I played a 50hz 0db tone. The HU was set at 25/50. I got 30 volts from the DMM.

Then I played a 40hz note, nothing else was messed with, still 25/50 on the HU.........and I got 40 freakin' volts!! wtf is going on? Is the DMM crap or is that how the amp is supposed to work?

30 volts at 2 ohms is 450wrms

40 volts at 2 ohms is like 800wrms.

When I hook up the subs, both the 40 and 50hz tone sound similar in volume.

anybody know what the hell is happening here? It makes me question the validity of using a DMM to tune your amps.

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[trumpet 5,000+ posts]

If you unhooked the subs you're not getting a 2 ohm load. Your math is wrong. Check the voltage with the subs hooked up, and you should be turning the HU volume up a lot more than 1/2 unless it causes your speakers to distort. Leave the EQ flat.

 

[Beatin' 10+ year member]

If you unhooked the subs you're not getting a 2 ohm load. Your math is wrong. Check the voltage with the subs hooked up, and you should be turning the HU volume up a lot more than 1/2 unless it causes your speakers to distort. Leave the EQ flat.

The point is everything is flat, the HU level was set at 25/50, and a 50hz gave me 30volts while the 40hz tone gave me 40volts. Why is that?

 

[Fattony911 10+ year member]

^^ lol what he said If done right it's a solid way of checking/tuning your system. i love my DMM

 

[Huge2na]

The point is everything is flat' date=' the HU level was set at 25/50, and a 50hz gave me 30volts while the 40hz tone gave me 40volts. Why is that?[/quote']
Different tones or rolloffs in the source material could make the difference,

That is why when you do SPL and then do SQ RTA testing you have to make adjustments.

If you were using pink noise or something that covered all frequencies your results would be different again.

This is how cheap Chinese amplifiers would rate some of their wattage and THD numbers.

At a certain frequency point to obtain a false wattage reading and another frequency point for their THD.

All amps dont play all tones equal.

 

[Beatin' 10+ year member]

Different tones or rolloffs in the source material could make the difference,
That is why when you do SPL and then do SQ RTA testing you have to make adjustments.

If you were using pink noise or something that covered all frequencies your results would be different again.

This is how cheap Chinese amplifiers would rate some of their wattage and THD numbers.

At a certain frequency point to obtain a false wattage reading and another frequency point for their THD.

All amps dont play all tones equal.

then how would you know if you were tuning your amp correctly if different frequencies give off different voltage?

30volts when given a 2ohm load, which is how my subs are wired, will give 450wrms. 40volts at 2ohms will give 800wrms. Both tones were 0db in amplitude.

 

[Huge2na]

copied and pasted--------->

There is no way to make a hertz to watts conversion. This is due to the simple laws of physics. Simply put, hertz is a measure of frequency and is usually represented in cycles per second. Watts, on the other hand, is a measure of power. They are closely related however. This is easily seen in when looking at radio stations. When a station has a certain number of watts, or power, that creates a certain frequency for their transmission. The frequency is where they are located on the radio dial.

My words------------> Hertz is only cycles per second, the 40hz tone pulses are longer therefore causing your amplifier to make more energy (volts) The 50hz tone is pulsing quicker and has shorter pulses.

People swear by using different methods of setting up their system, some use RTA's some use SPL meters, some use the DMM, in the end it is what comes out of the speakers that matter. I used a low level spl meter and tuned my system at low volume. And dont forget your gains on your amplifiers are not volume controls. They should be matched to your input voltage accordingly.

 

[Beatin' 10+ year member]

i just now used a 100hz and 70hz tone at 0db, HU 25/50.

I got around 43volts with the 100hz tone and 41volts with the 70hz tone..............the 50hz tone once again gave me 30volts.

Either my amp is funked, the cheap azz $5 DMM is funked, or using a DMM is not an accurate way of tuning an amp.

by the way, the gain has already been set a while ago with the 50hz tone. I just wanted to see what would happen if I used different frequencies without messing with the gain and the results, obviously, have been wildly different.

 

[trumpet 5,000+ posts]

copied and pasted--------->There is no way to make a hertz to watts conversion. This is due to the simple laws of physics. Simply put, hertz is a measure of frequency and is usually represented in cycles per second. Watts, on the other hand, is a measure of power. They are closely related however. This is easily seen in when looking at radio stations. When a station has a certain number of watts, or power, that creates a certain frequency for their transmission. The frequency is where they are located on the radio dial.

The amount of transmission power of a radio station does not determine the broadcast frequency. The frequency is assigned to the station by the FCC, as well as the maximum power output. What we do much more than car audio at Easy Way Electronics is RF communications using FCC licensed radios. The radios are programmed for certain frequencies and the power output can be regulated.

The DMM method of gain setting is for getting the amp set in the ballpark. It's only accurate at the frequency of the test tone. We set the head unit to the loudest it can be without clipping the pre-outs or without causing the speakers to be distorted because that's when the amplifier is getting the strongest input signal. Tuning at an intentionally lower volume for any reason besides protecting the speakers powered by a head unit's internal amplifier is setting yourself up for failure.