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Help me push my subwoofers to the max

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  • Help me push my subwoofers to the max

    I finally got around to buying a better amp for my subwoofers. I had a pioneer GM-5300T, this amp was only feeding my subs 125 watts rms each. I bought a Kenwood-KAC-8103D, this amp is feeding the subs 250 watts rms each. I am using it with 2 JBL GT4 12" subs which take 250 watts rms each. They are wired to put a 2 ohm load on the amp. I am not sure how big my enclosure is because I bought a prefabbed one and I am not very good at building stuff like that. I would estimate each sub has about 2 cubic feet of air, maybe more. The enclosure is sealed. My carpc has a sound blaster live 24 bit PCI sound card.

    Here are some pics of my equalizer and amp settings.



    The problem I have is I was expecting a lot of bass. More bass than I would have even wanted. Maybe I am naive, but I am disappointed. I listen to music like megadeth, so I am wanting loud drum hits and loud bass guitar notes. I actually cant tell much of a difference between my old amp and my new amp. If I turn up any setting any higher my amp goes into power protect mode. So even at high volume, and low gain everything is still not very loud.

    I have upgraded the big 3 wires, checked all of my connections, and everything checks out. I am using 4 gauge wires all the way to the amp, and 6 gauge wires to the subs. The amp gets about 12 volts, but when idle it drops to 11.5 on hard bass hits at max volume. I would assume driving down the road it gets 12 volts, but maybe I am wrong.

    I am not an expert, or anything close to it, so can someone give me some pointers and explain what I am doing wrong? Am I expecting too much from my system?

  • #2
    The bass boost setting at 0db might be one reason...
    Have you looked in the FAQ yet?
    How about the Wiki?



    Under normal circumstances, a signature would go here.

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    • #3
      no. darque, your falling off your game! bass boost artificially enhances certain freq-- which can led to destroying subs when you push them to play a freq that they shouldn't normally play that loud.

      according to my old knowledge, doubling the power supplied to the subs will have a increase of about +3db. humans can usually tell a difference at a minimum of +6db. so there isn't much you can do with teh amp setup.

      one of the things you can try is to move the box around in the trunk, and experiment with it facing certain directions, sometimes this can help get louder bass as well.
      My OLD 2001 Mitsubishi Eclipse GT:
      "The Project That Never Ended, until it did"


      next project? subaru brz
      carpc undecided

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      • #4
        Turning the bass boost up even to 1 will make the amp shut off pretty quick. After some searching I think it may be my equalizer. I am going to re-tune it again with the equalizer turned off. I know these subs can play so much louder because when I turn up the settings to a level that sounds nice the amp cuts off after about 3 minutes.

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        • #5
          If the gains are at the top, something is definelty wrong. I would recommend googling "setup up a car audio amp" or something similar that gets you the results. You will need, at minimum a DMM.
          My 2007 Ford F350 Work Log located HERE

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          • #6
            Originally posted by soundman98 View Post
            no. darque, your falling off your game! bass boost artificially enhances certain freq-- which can led to destroying subs when you push them to play a freq that they shouldn't normally play that loud.
            I concur, but if you want to get bass from your sub (which is it's purpose anyway), increasing the bass frequencies at the amp should also increase the power to the subs, at least in my mind.
            Granted, it's not anything you want to crank all the way up at one time. I would think bumping the bass boost up a level to determine how it improves the bass couldn't hurt...
            Unless it kills the amp, as the OP said it does.

            I'm the first to admit that settings on specific pieces of equipment aren't my area of expertise.
            That's probably why I haven't tweaked my amps.
            I probably should.
            Have you looked in the FAQ yet?
            How about the Wiki?



            Under normal circumstances, a signature would go here.

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            • #7
              yes, a little bass boost would not hurt, but in general, people love to crank it all the way to max. so because of this, i stay with the method to keep it turned off, because most don't know how to utilize it correctly, or listen for distortion in their subs.. so combined, these problems lead to sub failure..
              My OLD 2001 Mitsubishi Eclipse GT:
              "The Project That Never Ended, until it did"


              next project? subaru brz
              carpc undecided

              Comment


              • #8
                If these are the correct specs

                Frequency Response: 28Hz - 450Hz
                Sensitivity: 93dB
                Impedance: 4 Ohms
                Voice-Coil Diameter: 50mm
                Cut-Out Diameter: 283mm
                Mounting Depth: 161mm
                Overall Diameter: 311mm
                Vas: 100.45 liter
                Qts: 0.43
                Fs: 24.75Hz
                Qes: 0.46
                Qms: 6.46
                Sealed Enclosure (vol): 28L
                Vented Enclosure (vol): 64L

                and your box is actually as big as you say (measure to be sure to find the volume), then the box is probably too big (unless you vent it). It needs to be about 1cuft per sub sealed. If you want more output then I would suggest a vented enclosure. If this is in a larger vehicle, you will not have the same gain from the cabin as you would a smaller vehicle so I would say you should look at venting. You haven't said what kind of vehicle this is in. I also notice you have the subsonic filter set at 25hz, that will affect the low lows. However, if you are listening to metal I think midbass should be your focus, but I really don't know what your expectations are or if you heard something else you are using as a reference.
                Last edited by durwood; 06-11-2011, 02:49 PM.
                System always under construction


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                • #9
                  I measured the box and I came to about 1.9 cubic feet per box. L30 X W18 X H 13 for the whole box. So I guess my box is twice as big as it should be. I have the setup in a 2000 cavalier with the back seat down.

                  I did set my equalizer to default and turned up the low pass filter to 100, the bass boost to 1, and lowered the gain by a hair. I managed to rattle off my rear view mirror, and my amp hasnt shut off(yet). The bass is pretty good now, but now I want to see about stuffing the box to cut its volume in half. I actually want to keep the box because I mounted all of my equipment too it so I dont have to mount it to my car. What is a good material to stuff the box with?

                  About the subsonic filter... If my sub only plays down to 28hz my understanding is that it would not affect the output. Am I wrong?

                  I was also thinking about tossing my 4x6 phoenix gold front speakers for some 6.5" alpine speakers to increase my midbass since that is what I am currently lacking. I also have some kenwood 6x9's in the back and I am not very happy with their performance. If the alpine speakers sound good enough I may take out the rear 6x9's so I can keep my back seat up and let the bass come through the speaker holes.

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                  • #10
                    If you can, go with the type "R" 6.5", not the "S". My ears, at least, can really hear the difference. Not a bad plan dumping the rears and running front stage only. What amp are you driving the fronts with, the leftover Pioneer?
                    My 2007 Ford F350 Work Log located HERE

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                    • #11
                      If the amp shut off so easy means that it can not handle the load of 2 Ohms.
                      Try to connect the subs at series to load with 8 Ohms your amp, that will make the amp deliver more power to the subs before it goes to protect mode and maybe you can have a little of what you wand.
                      Another thing that i have in mind that some times goes wrong is the polarity between the two subs or between the subs and the other car speakers.
                      Try to play only with the sub and only with speakers, if you hear that your sub sounds louder without the speakers or that the speaker bass goes down when you bring the sub on then it means that you have a polarity (i think its called face in english) problem. Some times i have see that the polarity between the speakers was wrong and have no bass at all with all front speakers playing together. With 4 x 6" and 2 x 6x9" you must easily make your rear view mirror shake without any sub connected.
                      If it's difficult to do the test then just try to change the polarity of the sub.
                      So please double check that you have connect the subs and the speakers polarity correctly (positive with positive and negative with negative).

                      PS. Sorry about my bad english and sorry if something that i have wrote has been wrote above and didn't see it.

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                      • #12
                        Originally posted by LeonGR View Post
                        If the amp shut off so easy means that it can not handle the load of 2 Ohms.
                        Try to connect the subs at series to load with 8 Ohms your amp, that will make the amp deliver more power to the subs before it goes to protect mode and maybe you can have a little of what you wand.
                        Another thing that i have in mind that some times goes wrong is the polarity between the two subs or between the subs and the other car speakers.
                        Try to play only with the sub and only with speakers, if you hear that your sub sounds louder without the speakers or that the speaker bass goes down when you bring the sub on then it means that you have a polarity (i think its called face in english) problem. Some times i have see that the polarity between the speakers was wrong and have no bass at all with all front speakers playing together. With 4 x 6" and 2 x 6x9" you must easily make your rear view mirror shake without any sub connected.
                        If it's difficult to do the test then just try to change the polarity of the sub.
                        So please double check that you have connect the subs and the speakers polarity correctly (positive with positive and negative with negative).

                        PS. Sorry about my bad english and sorry if something that i have wrote has been wrote above and didn't see it.
                        Thanks for the tip. I actually found out first hand what happens if you mix up the polarities. The subs will sound like crap, and they only play quietly. So if the polarity is reversed I will know as soon as I play music.

                        Right now I get very little bass from my 4x6's and my 6x9's. My 4x6's do not handle any bass at all.
                        My 6x9's are Kenwood KFC-6982IE
                        My 4x6's are Phoenix Gold Ryval V460

                        I thought I would have to cut my doors up to fit 6.5's in them, but it looks like I can buy a cheap adapter or even make my own.

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                        • #13
                          I got my hands on an oscilloscope. I tested both of my amps and my subwoofer amp was majorly clipping. Here are the highest settings my amp can go before clipping at max volume.



                          I set it according to a test tone first, but then I played several songs to make sure it wasnt clipping, and I was able to turn the gain down a small amount before I saw clipping in the signal.

                          I made sure to set all my gains to look like the wave below. If I increase any setting the wave starts to flatten at the top and bottom.


                          Now I am very disappointed in the volume of my subs. They barely even shake my mirror. So now what? Surely two 250 watt rms subs with a 500 watt rms can be louder, right?

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                          • #14
                            If the 2 subs are in separate chambers, try only 1 sub. You might be suprised. If the subs are inefficient (power hungry), the amp may not be up to the task of powering 2 of them even though the numbers on paper seem to work.

                            If they are in a shared chamber and you have (or have access to) a shop, throw together a box for 1 sub and try that. You might be plesantly suprised. Also positioning of the sub can make a huge difference so if you have a smaller single sub box, you can play around with positioning. I am a big fan of down firing if the sub is in the passenger compartment.

                            I am running 1-12" RD Sonance sub with 657w RMS and I'll tell you it can get pretty uncomfortable in there if you crank it up and thats in a very large crewcab truck.

                            The other thing I question is the sound card. Is it producing enough clean pre out voltage?
                            The quickest way to rule that issue out is if you have a decent head unit with pre-outs laying around: hook it up temporarily to the vehicle power, move your RCA's over from the amp and pop a cd in.
                            My 2007 Ford F350 Work Log located HERE

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                            • #15
                              You should make sure that your amp is stable at 2 Ohms. It seems like it is not.
                              Originally posted by Lincolnman
                              Your English is fine, don't apologize. You're doing better than most Americans.

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