Welcome to the all new Geo Metro Forum. We hope you enjoy your visit.You're currently viewing our forum as a guest. This means you are limited to certain areas of the board and there are features you can't use and images you can't see. Registration is simple, fast, and completely free. If you're already a member please log in to your account to access all of our features: Join our community! |
| Watts test | |
|---|---|
| Tweet Topic Started: Aug 26 2015, 08:25 PM (995 Views) | |
| evmetro | Aug 26 2015, 08:25 PM Post #1 |
![]()
|
I picked up a Kicker 125.2 amp awhile back, and just put it in. I decided to test it to see what it really does, since I keep hearing people refer to the max watts for their amps. Amps are marketed to a persons ego, which is why they print all of the crazy watt claims on them. Anyway, the box for my amp has big letters on the box that say "250 watts max". When I look it up on crutchfield, the specs say "30 watts x 2 at 4 ohms." This is a lot more realistic, and what I expect to find during my test. I turned up the music as loud as I could, and kept messing with the volume until I had a solid feel for where the threshold of distortion was. While I was doing this, I kept an amp meter hooked up, so I could keep an eye on it while I pushed it back and forth from where I could hear audible distortion and back to where it was clean. The maximum amps never exceeded 4 amps, and 4 amps looks like the most that you can draw from the battery. I have the amp hooked up to a pair of 4 ohm speakers, and my input voltage stayed steady at 13.8. Anyway, if you multiply 13.8 volt x 4 amps, you get 55 watts, which in my case would be 27.6 watts per channel of good clean, continuous power. Not too far off of the crutchfield specs, but nowhere near the 250 watt max that was printed on the box. This amp is a 55 watt amp. It does a fine job of rocking the rear speakers in my 93 hatchback, so maybe I will get around to doing something to the front. |
![]() |
|
| evmetro | Aug 26 2015, 08:42 PM Post #2 |
![]()
|
In case anybody is curious, I have a bank of the original JL Audio 1000/1 amps to power my four JL Audio 10W7 subs in my shop truck, and I can pull about 65 amps per amplifier, at 13.8 volts. Not quite 1000 watts each, but not too shabby for having the 1000 watts printed on the amp. |
![]() |
|
| t3ragtop | Aug 26 2015, 08:48 PM Post #3 |
|
Turbo3 and Twincam Tweaker
![]()
|
not exactly the specified test per ftc rules but close enough for government work. ![]() one thing to consider is that the input current will be higher than the output current considering conversion losses. no amplifier can have unity in the real world. considering the output transistor biasing scheme it can convert a large amount of the input current into heat. class a amps turn about 30% of their power supply current into heat. class d amps are more efficient but still burn around 10% in conversion. i use a math formula to calculate power from output voltage into a load that uses the square of the load to come up with current and then rolls the current back into the speaker impedance to derive power in watts. that gives me a more accurate calculation of the rms power. years ago the government stepped into the madness of home audio output power ratings and the ftc required all audio manufacturers to use a specific testing methodology that included total harmonic distortion levels and rms wattage outputs to level the bullshit the marketers were coming up with. car audio never got put under the same requirements and that's why car amplifiers always tout "ils" power ratings. ils stands for "if lightning strikes."
|
![]() |
|
| evmetro | Aug 26 2015, 09:03 PM Post #4 |
![]()
|
I understand that the actual testing procedures are probably done in a lab, that's why I like to test them this way. It gives a real world perspective that I don't think they test for in the labs. My guess is that the Kicker can probably test at a full 30 watts per channel, but it is nice to see what I can expect in the real world. I tested a Boss amp a few years back with my real world test, and was absolutely disgusted. |
![]() |
|
| t3ragtop | Aug 27 2015, 05:10 AM Post #5 |
|
Turbo3 and Twincam Tweaker
![]()
|
another way the car audio manufacturers cheat is that they use 14.5 volts when they make their calculations for power output instead of 12 volts.
|
![]() |
|
| terry8750 | Nov 15 2015, 12:03 AM Post #6 |
|
terry8750
![]()
|
not really sure how many amps my system pulls but i am curious. when i had my cs130d it would drop down to 8 volts before it shut down until i put a agm battery from xs in.after that it dropped to 10 volts as low as i got it before i turned it down.we all know the cs130d puts out 105 amps. so its safe to say my system load is alot higher than 100 amps.not really sure though i have 2 ssl 4000 evo d amps and a class a/b ssl evo 2000 watt amp.im guessing somewhere around 3.5k watts true power |
![]() |
|
| evmetro | Nov 15 2015, 01:30 AM Post #7 |
![]()
|
You may benefit from an additional battery or two. I run a big system that will pull the charging system down like that, but a second battery allows me to run my system pretty hard. The big current draws in my music do not happen continuously, so my average current draw is far less than the big peaks. I can pull my system down to 10 volts or so within about a minute with a single battery, but with two batteries it takes almost two minutes. I knew I was going to be making my truck into an spl truck when I bought it new, so I opted for the tow package with the 160 amp alternator when I bought the truck. Two minutes of more than 150 decibels is pretty extreme, and I rarely go that high for more than a few seconds. Even rolling around town in the upper 140s for a half hour messes with my ears for the rest of the day. It would be interesting to do some "real world" testing on your amps to see what is really happening, since they have have obviously inflated watt figures on them. Those kinds of amps would really be the most interesting to test compared to amps that retail for $1 per watt @ 4 Ohms. |
![]() |
|
| terry8750 | Nov 15 2015, 01:18 PM Post #8 |
|
terry8750
![]()
|
my whole system including mids and highs are wired down to 1 ohm.that makes a huge difference as far as power output.my subs muasure .95 ohms and my left and right channel is wired down to .75 ohm each side lol |
![]() |
|
| t3ragtop | Nov 16 2015, 08:59 PM Post #9 |
|
Turbo3 and Twincam Tweaker
![]()
|
when you say that they "measure" down to..... just how are you measuring them? voice coils being coils, they are inductors. the measurement of an inductive load has to occur at some frequency. sticking an ohm meter across the terminals will give you a measurement of resistance. inductors are measured by impedance which varies with frequency. you have to use very sophisticated measurement instruments to measure the impedance of a speaker as it has to be done across a frequency band. the resultant measurement can vary a good bit within just a few hertz. due to the complexity of the wave shape of a musical signal you have to average current over time. you can use a signal generator to play a tone and measure the voltage as it drives the speaker. then you apply averaging to the measured voltage to indicate the rms value to derive the applied current mathematically. there are other tests that need to run as a part of the analysis. your amps will also generate distortion which usually increases pretty drastically as power increases. a great many transistor amplifiers can output a lot of current but very few of them can output a lot of current and stay under a level of distortion of 10%. most car amps have total harmonic distortion percentages of higher than 20%. by comparison, i have vintage nakamichi amps that will put out 100 watts with a thd rating of a tenth of 1%. a 2000 watt car amp will most certainly be over 10%, or a hundred times more distortion. maybe the easiest way to actually get a good idea of how much current your amps are putting out there would be to use a signal generator set at 60 hz and then using a good clamp on ammeter on a positive speaker cable. it wouldn't be dead nuts accurate but it would give you a good representation without the chance of math errors. |
![]() |
|
| terry8750 | Nov 16 2015, 10:19 PM Post #10 |
|
terry8750
![]()
|
Yea i need to get a clamp meter.as far as my measurement its with no load .supposed thd on my is supposed to be .01% but somehow i doubt that its true although i try to tune it by ear with my bass boost. It is usually set on 8+ db with the deck set on -6 db bass and my sub pass low filter set to 20hz to 200hz range with gain maxxed out on 100mv to 2v setting.mids and higher set to 200hz high pass filter gain maxxed out as well. |
![]() |
|
| t3ragtop | Nov 17 2015, 06:08 AM Post #11 |
|
Turbo3 and Twincam Tweaker
![]()
|
thd can be very low when power output is low. it's when the amp approaches its max output that thd goes way up. an amp can be rated for 2000 watts and be clean and musical at 200 watts but sound like ass when you try to play it loud. in practice and because speakers are really pretty inefficient, for every 3 db or a doubling of loudness an amp needs to produce 10 times the electrical energy. that means that if you play at 200 watts, to double the volume you would need the amp to put out 2000 watts. to double the volume again you'd need the amp to produce 20,000 watts! |
![]() |
|
| 1 user reading this topic (1 Guest and 0 Anonymous) | |
| « Previous Topic · Audio Section · Next Topic » |


Welcome to the all new Geo Metro Forum. We hope you enjoy your visit.







7:56 PM Jul 10