# amp question



## scrappy (Jun 30, 2002)

I have a kicker 1200.1 running two 12L7. I finally broke down and had a shop build me a box for my subs. I had the amp installed in my Durango. How do I tell where to set the low pass filter? Also why do we buy such expensive amps, components and subs if we cant max out the potential. On my old Kenwood Excelon amp I can gain it anywhere with no problems and it sounds good but people say only gain it to the voltage of you hu. So then it seems like you never really get the most out of your equipment. I have the gain on the kicker set around where it should be but its not loud all the timeike it was in my car. Any help would be appreciated


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## Zac (Mar 10, 2004)

A single KX1200.1 is SERIOUSLY underpowering 2 L7s. I run a KX1200.1 on a single L7. How is your voltage looking...IIRC our amp is not regulated and mine drained all of the power from my car until I went with a Yellow Top with 750CCAs, 4 guage terminal rewiring and a 1 farad cap.

What type of box are you running?


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## scrappy (Jun 30, 2002)

I have a ported 2.5 cf box. Not real sure about the voltage. Im not sure if the amp is regulated I had a yellow top and 1 farad capacitor in my car so Im not real sure. I had the subs in my car for a while and it sounded good


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## captain_shrapnel (Sep 10, 2004)

scrappy said:


> Also why do we buy such expensive amps, components and subs if we cant max out the potential. On my old Kenwood Excelon amp I can gain it anywhere with no problems and it sounds good but people say only gain it to the voltage of you hu. So then it seems like you never really get the most out of your equipment. I have the gain on the kicker set around where it should be but its not loud all the timeike it was in my car. Any help would be appreciated


You are looking at it the wrong way. When the amp gain is set to match the output of the headunit, then the amp makes full rated power when the headunit puts out full signal strength. To crank the amp gain higher will make the amp work closer to full power more often on quieter passages in your music, but when the bass hits the amp will clip the signal and distortion will occur. This is a bad thing. You may not even hear the distortion occuring, but it is there, damaging your speakers. What you hear as "louder" from your previous (improperly set up) amp, is an illusion caused by signal compression. This effect is like watching a movie on tv (full of quiet and loud sounds). You turn up the volume to compensate, but when a commercial comes on the volume rips your head off. This is because commercials are intentionally compressed to provide a perceived volume increase in order to get your attention. Ever notice how the same song you have on cd seems louder on the radio, all thing being equal? Same thing. Compression is a bad thing for sq, because it does not demonstrate the dynamic range of a good system. It is very bad when it happens in an amplifier, because the output reaches a higher duty cycle as the signal is clipped, which leads to heating in the voice coils. In modern subwoofer design, this is the leading cause of driver failure. Did that answer your question?


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## scrappy (Jun 30, 2002)

The excelon amp I have had running 12w3s and now RE12s, not the L7s. I had the same kicker amp in my car as I do my truck. The shop I had install it in my car had the gain about 3/4 of the way up and it hit really hard no matter what. Does clipping occur in every amp? My understanding was that the box blew my subs, but what about the clipping could that have done it? Are some amps more prone to clipping than others? The low pass filter how do I know where to set that at? So the only way to get more out of my subs would be more power not turning the gain up. Maybe Ill get another 1200.1 and strap them together I wonder what kind of ohm that would put out?


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## captain_shrapnel (Sep 10, 2004)

scrappy said:


> The shop I had install it in my car had the gain about 3/4 of the way up and it hit really hard no matter what.


Every amp requires different gain adjustment. It hit hard because it was dialed in right.



scrappy said:


> Does clipping occur in every amp?


In short, yes. Eventually, a signal can be driven harder than the electronics inside of the amp/headunit/equalizer/crossover can accurately reproduce. This is the limit of its performance. 



scrappy said:


> My understanding was that the box blew my subs, but what about the clipping could that have done it?


Was the box built by a professional? Was it sealed or ported? Where did the specs for the box design come from, the sub manufacturer? A computer program like LEAP? Or just invented from thin air? The answer to that is complicated, but if it was built by a pro (at least someone who REALLY understands what they are doing) then it is unlikely that a poorly designed box was the issue. Operator error is the typical cause of blown subs. When an audio signal originates from its source, the waveform is a smooth, curvy line. As the signal gets stronger (louder), the waveform becomes stretched vertically, but still retains its curvy shape. All is fine until you hit the limits of an amp's power supply voltage. This is the ceiling that a waveform can accurately acheive. Since the wave cannot exceed the voltage ceiling at all, what happens is the tops of the wave become flattened as volume continues to rise. The nice curvy form now has sharp angles and flat spots. This is known as 'clipping' and doesn't jive well with the movement of a speaker cone. Under an un-clipped signal the cone moves out, slows down, changes direction, moves in, slows down, changes direction, etc.. It is a natural and smooth movement that is easy on the speaker. But an clipped signal take the speaker, slams it out hard as fast as it can, reaches its limits and just stays there for a little while, then as hard as it can, slams the cone the other way and hold it there for awhile. Terrible for the moving parts of a speaker.
Also, under a clean signal, the amp reaches full power for only a VERY small portion of the waveform (just the peaks). This is like duty cycle--the amp spends 99% of its time doing less than its full output. But under a clipped signal, the flattened peaks mean that a significantly larger chunk of the waveform is under full power, maybe 5%, maybe 50% depending on how badly you abuse it. The amp heats up and worse, the voice coil has to deal with potentially 10x the amount of thermal loading. Most of the time, this is what happens. The voice coil gets so hot so fast, that its tiny windings melt and burn. The speaker is then 'blown'.



scrappy said:


> Are some amps more prone to clipping than others?


Technically, no. Every amp has its limits, but reputable companies tell you TRUE specs, while other companies find ways to bend the rules and exaggerate the performance of their amp. This is why a 1000 watt Pyramid amp is not the same creature as a 1000 watt US Amps amp. So realistically, you could say that some amps are more prone to clipping, but only because the manufacturer didn't accurately tell you where that point is. Just buy quality, you'll be fine.


scrappy said:


> The low pass filter how do I know where to set that at?


 Trial and error. For a sub, start at about 100hz and then start turning it down till you get to where it sounds right. Most people find that between 80-60 hz is the place to be, but it depends on the midbass drivers ability to go low.



scrappy said:


> So the only way to get more out of my subs would be more power not turning the gain up.


You got it. Unfortunately, there are no shortcuts when it comes to power. If you want it louder, get more power. No way around it.



scrappy said:


> Maybe Ill get another 1200.1 and strap them together I wonder what kind of ohm that would put out?


I don't know about the specific amps you are talking about, but it is a RARE thing to get amps that can be hooked together. Don't do it, unless the amp manufacturer says thats cool. They would also list the impedence that would drive.


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## scrappy (Jun 30, 2002)

Well Kicker makes the 1200.1 capable of being strapped together with another one, but it looks like it is a 2 ohm load wich doesnt make sense. At 2 ohm the amp is rated at 600 and at 1 ohm 1200 so wouldnt that be useless. That would be the same power. I wish my amp was rated at rms instead of peak then I would be good with a 1400 watt amp but now Ill need to look into this more thanks for the help. The box was a pre fab box and it was ported but really high I beleive. That is why I went with a box in my durango instead of my car. Everyone I have talked to has lead me to beleive the culprit was the box I had


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## captain_shrapnel (Sep 10, 2004)

That is a good possibility. Ported boxes have no room for error, so it is very likely that a pre fab box was not built to the specifications of that speaker. When ported boxes are matched to the speaker the sound quality can be phenomenal, but if you fudge the dimentions a little what you are left with is a big mess. For future reference, never buy a pre fab ported box. Have it custom build by a pro.


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## scrappy (Jun 30, 2002)

Yeah I know not to buy pre fab boxes but I though tthe shopknew what they was doing when they said they had boxes for the subs. I wonder if I could turn the gain up more like the shop had since I have a good box now.


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