Amp/Speaker Config help please???


wakedreams3

CarAudio.com Newbie
Aug 9, 2020
5
0
Dallas, TX
All,

I have a Kicker ZX250.2 amp powering 4 - KM620.2 drivers with seperate tweeters. (If you count the drivers and tweeters there are effectively 8 speakers) Essentially the original install has 2 speakers going to each channel of the amp.

My amp continues to clip out (protection light comes on and kills amp). I have checked voltage at the amp terminals on the Remote Wire and B+…voltage remains high before and after amp turns off (protection light on).

I assume my amp cutting out is because on the speakers it is trying to power?? My thought is upgrade to a 4 channel amp unless I am on the wrong path?

Here are the speaker/tweeter specs:

General
Design 2-way
Tweeter Design 3/4" Dome
Tweeter Composition Titanium
Woofer Composition Injection molded poly
Woofer Surround Santoprene rubber

Specifications
Sensitivity 88 dB
Frequency Response 35 - 21k Hz
RMS Power Range (Watts) 10-65
Peak Power Handling (Watts) 195
Impedance (Ohms) 4
Top-mount Depth (Inches) 2 13/16
Bottom-mount Depth (Inches) N/A
Cutout Diameter or Length (inches) 5 1/8
 

Lasherž

CarAudio.com Elite
Apr 27, 2020
1,016
233
United States
All,

I have a Kicker ZX250.2 amp powering 4 - KM620.2 drivers with seperate tweeters. (If you count the drivers and tweeters there are effectively 8 speakers) Essentially the original install has 2 speakers going to each channel of the amp.

My amp continues to clip out (protection light comes on and kills amp). I have checked voltage at the amp terminals on the Remote Wire and B+…voltage remains high before and after amp turns off (protection light on).

I assume my amp cutting out is because on the speakers it is trying to power?? My thought is upgrade to a 4 channel amp unless I am on the wrong path?

Here are the speaker/tweeter specs:

General
Design 2-way
Tweeter Design 3/4" Dome
Tweeter Composition Titanium
Woofer Composition Injection molded poly
Woofer Surround Santoprene rubber

Specifications
Sensitivity 88 dB
Frequency Response 35 - 21k Hz
RMS Power Range (Watts) 10-65
Peak Power Handling (Watts) 195
Impedance (Ohms) 4
Top-mount Depth (Inches) 2 13/16
Bottom-mount Depth (Inches) N/A
Cutout Diameter or Length (inches) 5 1/8
It seems like you may be overdriving the amp and it's going into thermal protect. Have you set it up using ohm's law on the output terminals? The speaker load is 4ohms per set, so doing 2 to each channel in parallel is fine. They're pretty well matched as well so I don't think that's your problem. Do you know how to set your gains on the amp properly? This seems to be the most likely problem. Kicker gear doesn't often exceed its rating, so if you're clipping on that amp there's a good chance it'll overheat.
 
OP
W

wakedreams3

CarAudio.com Newbie
Aug 9, 2020
5
0
Dallas, TX
Thanks for the reply, I have set the gain at 35-40% (below 50%)...I have run the system at the highest level I will run it at and it will clip. I have backed the gain down from 40% it's operated better but still clips.

Any advice on setting the gains properly would be great.
 

Lasherž

CarAudio.com Elite
Apr 27, 2020
1,016
233
United States
Thanks for the reply, I have set the gain at 35-40% (below 50%)...I have run the system at the highest level I will run it at and it will clip. I have backed the gain down from 40% it's operated better but still clips.

Any advice on setting the gains properly would be great.
So since your amp questionably has an overheating problem, here's how you set it based on the rating of the amplifier:

You'll need a multimeter (doesn't need to be particularly expensive, just your basic junky hardware store one would work even) and a variety of -0dB test tones to play, you can find these on google, they're just .mp3 files or .wav of various sine waves, make sure they're -0dB.

For a subwoofer you'll want to cover the ranges that it plays, but usually it'll be the most power between 40 and 80hz, each system is different. Mine peaks at 50hz.
For midrange speakers you'll want to play from about 100-1000.

Turn the gain on the amp all the way down on every channel, remove all of the speaker wires from it, and if you're using bass boost turn it off (you can always come back and do this test using it, but this is for a baseline and ideally you'd never use bass boost anyways), you can leave the HPF or LPF the same. Then turn your head unit to 3/4 of maximum using one of the -0db test tones that's within the hz range you're looking to play with the channel you're setting up. The reason you don't go max is because the head unit can introduce clipping near its limit.

Put the multimeter on AC voltage mode and attach the leads to the speaker terminals of the channel or bridged channels you're adjusting first and turn up the gain until your multimeter senses at least a volt or two. Now go through each tone looking for the voltage that's the largest without adjusting the volume of the unit or the gain of the amp, the goal here is to find the frequency that represents the hardest note for the amplifier to play. Once you find approximately the tone that's higher than all the others play that tone and follow ohm's law for the value you're trying to achieve. Turn up the gain until you get the voltage value for your RMS rating, this serves as the baseline and what your manufacturer advertises it to be able to play. Kicker isn't great at going beyond rating, but their products can at least achieve what they're advertised for.

For figuring out the voltage you're after, take the RMS rating or the channel (65W), multiply it by your eventual speaker impedance (4 ohms), square the result (260) to get 16.12v, this is the voltage you're looking for. Once you see that value on the meter leave the gain setting alone and reconnect the speakers. You should now very rarely if ever clip it again under that 3/4 volume level, any additional gain or volume that you give it will be overdriving it according to the manufacturer, which most good amps can handle, but since you've already had issues with your cooling I wouldn't stray very far above that gain position.
 
Last edited:

JRsmoothee

caraudio.com negative asshole
10+ year member
Aug 12, 2008
1,378
97
sitting on toilet
do not set your gains that way, you will blow something....DMM's are only really accurate at around 50-60hz (research it) unless you have a very expensive DMM.....any frequencies beyond that and your numbers are gonna be way off from what you expect....your best off to play music and adjust gain by ear (we dont roll around listening to test tones)
 

Lasherž

CarAudio.com Elite
Apr 27, 2020
1,016
233
United States
What's being referred to is true RMS. Technically it's true that voltage readings can fluctuate as the frequency changes, however the peak is going to be in the 200-500hz range almost certainly for that amp, which most meters are designed to accommodate within their accuracy tolerances. You'll hardly see a difference with most meters until after 1khz, but true RMS won't necessarily spare you from this. Multimeters of any sort are no replacement for an o-scope, and will often deviate above 1khz, TRMS or not.

What true RMS actually means is that the sine wave doesn't need to be a perfect sine wave to get an accurate reading. The non-TRMS meters are set to accept sine waves with an RMS value of 0.707, which represents a perfect sine wave. The sine wave on these tones are very close if not dead on to sinusoidal and thus it's not a requirement to have a true RMS reading so long as you aren't feeding it clipped signals from the headset (which you avoid by choosing 3/4 of the volume). Obviously if you have a TRMS meter it's generally better overall, but you shouldn't doubt the accuracy of your meter simply because it's not TRMS in this specific exercise.
 

Lasherž

CarAudio.com Elite
Apr 27, 2020
1,016
233
United States
Ok...just got back to this, thanks for the replies I did see a similar procedure that blend the multimeter and "tune by ear" so I am going to start with this:


Thoughts?
As long as your amp no longer overheats afterwards. From what it sounds like you've already done the equivalent of that method. My recommendation was to achieve no thermal issues since the amp is CEA rated for that RMS wattage. Above it is touchy territory that is worth claiming, but thermals can be annoying to deal with on amps that don't have much slack beyond their ratings (like Kickers tend to be). If that website's method works for you and you're able to avoid clipping as well as thermals at the same time that's the ultimate goal and it will give you the best result. Alternatively if you find thermals become a frustration again using the new settings (hot summer days or less air circulation around the amp can cause new bouts of thermal cutoffs) just know the "correct setting" for that amp and that environment is somewhere in the narrow gap between the one you find using the website's method and using the ohms law method I listed.
 
OP
W

wakedreams3

CarAudio.com Newbie
Aug 9, 2020
5
0
Dallas, TX
As long as your amp no longer overheats afterwards. From what it sounds like you've already done the equivalent of that method. My recommendation was to achieve no thermal issues since the amp is CEA rated for that RMS wattage. Above it is touchy territory that is worth claiming, but thermals can be annoying to deal with on amps that don't have much slack beyond their ratings (like Kickers tend to be). If that website's method works for you and you're able to avoid clipping as well as thermals at the same time that's the ultimate goal and it will give you the best result. Alternatively if you find thermals become a frustration again using the new settings (hot summer days or less air circulation around the amp can cause new bouts of thermal cutoffs) just know the "correct setting" for that amp and that environment is somewhere in the narrow gap between the one you find using the website's method and using the ohms law method I listed.
Thank you!
 

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