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  • Bass Is Stuck In The Trunk

    I have a 2000 Volkswagen Jetta.
    Infinity Kappa Components all around ran off a JL Audio Slash v2 Series 300/4v2 (75x4) amp
    (2) Rockford Fosgate P3 12" Subs run off a JL Audio HD Series HD750/1 (750x1)
    Signal comes from my Intel DG45FC through (3) JL Audio CL-RLC Line Drivers.

    The JL HD750/1 amp is really nice, but its short-coming is that it lacks a bass boost. I have a JL Audio Slash v2 Series 1000/1v2 on order to Fix this issue.

    But what my real problem is that all the bass that I can produce gets trapped in the trunk of my car. Most of it I believe is getting absorbed into the back of seats.

    Before I had the line drivers I had insufficient signal to the amps but I still had tons of rattling in the rear deck under the rear window so I had to dynamat that area to stop the noise (the rattle was louder than the subs...) But by doing that I have blocked the sound that could be coming through that thin deck and now with the seats up and the amp cranked its not near what I want it to be. Put the seats down and the hair on your head moves and you feel the bass deep in your chest.

    Does anyone have any ideas on how I can get great bass response into the cabin of my car without having to put the seats down?

  • #2
    bass boost is a poor idea on any sub-- it artificially makes a frequency(or technically a small group of frequencies) and can lead to damaging the subs because ytou could be pushing them to hard at a frequency and level that they were never designed for...


    for the bass staying in the trunk, some seats use a plywood backing material so that the seat is more durable while it is laying down, and you have heavy objects on it.
    you can try to make holes in the plywood to allow the sound to escape through the seat. but do not expect it to be exactly as loud as it would be with the seats down--it should be quieter, but similar to turning down the amp 1 or 2 notches.--in all cars that have rear seats that i have sat in, there is a noticable difference in the output of bass with the seats up/down, but all with open backed/non-plywood-backing have very little effect.
    My OLD 2001 Mitsubishi Eclipse GT:
    "The Project That Never Ended, until it did"


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    • #3
      Originally posted by soundman98 View Post
      some seats use a plywood backing material so that the seat is more durable while it is laying down, and you have heavy objects on it.
      you can try to make holes in the plywood to allow the sound to escape through the seat.
      I'm going to have to look into this one for sure. Also I might try to cut some holes in the dynamat in areas that it is not touching anything.

      I've had other cars before with lower end subs and amps and never had this big of a change in sound with the seats up or down.

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      • #4
        Which way are the subs facing?
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        • #5
          They are facing forward firing into the the back of the seats.

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          • #6
            Are they seal or ported? I have an 08 chevy cobalt with 1 15 ported tc-sound 3000 & a kicker 1500w...with seat up it still have crazy bass...back seat down...you don't want to get in there.
            Try firing them backward.

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            • #7
              Originally posted by bratnetwork View Post
              They are facing forward firing into the the back of the seats.
              Try turning them around facing the outside.
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              Micro Control Center... Control Your Car Across the Internet
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              Website: (It's a work in progress, really. All my projects have taken me from ever really developing it.)
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              • #8
                Do you get more bass with the trunk open? If so, then turn the subs around facing the rear of the vehicle. Bass notes have a longer pathlength and it sounds like it doesn't have enough space to propagate. Having it reflect off the rear of the vehicle will probably help.

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                • #9
                  keep the JL audio hd750, as it is far enough. Bass boost is a stupid thing for kids.
                  The problem is your subwoofer enclosure or the method you placed and fixed it into the trunk.
                  Please supply some more info and maybe pics about the enclosure, wiring, placement, etc.
                  Also, I agree with soloxp and PaulF, try them facing backwards.
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                  • #10
                    The JL 1000/1v2 is already ordered and on its way. Even if i don't use the bass boost feature the extra wattage will be good. My subs can handle it, and right now my HD750 is crank up to the max and the gain is as high as it can go without distortion. I can never get enough bass. I was originally going to go with that amp when I initially did the system but opted for the HD750 mainly because it has a plug for the power, ground, and remote that you can just pop off and remove the whole box out of the trunk if I need the space, but I have yet to take it out since I installed it...

                    I am definitely going to try turning the subs around the other way and trying that. Also I'm going to cut out some of the dynamat in the deck in places it doesn't need to be like where its covering a hole and not touching anything.

                    I am going to look into the plywood in the seats also, but that is kinda a last resort deal as taking the seats apart and drilling them out would be a ton of work.

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                    • #11
                      I think adding some soundproofing and deadening in the car would help more than a bigger, but
                      inferior amp (+250W but more noise, distortion and 100A fuse instead of 60A)
                      750W with a proper installation would be far enough to damage your hearing

                      Try to turn down the amp a bit, and connect only one woofer to it, maybe you will have better sound.

                      or

                      Try to adjust the Input Sens and Input Voltage according to the manual.

                      Also, some questions:
                      What kind of enclosure do you have for the woofers?
                      How do you wired the woofers to the amp (parallel/serial)?
                      Check my worklog:
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                      Lord of the boards: DFI CP100-NRM

                      "Or you can try Ubuntu, but than don't tell everyone you are using linux,
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                      • #12
                        Might be a little extreme to some, but what helped me was to cut a rectangular hole in the rear deck to allow the bass to escape... my box was too large to mount facing backwards but that might help you in your situation... if not more drastic measures may be required

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                        • #13
                          Originally posted by simplex View Post
                          I think adding some soundproofing and deadening in the car would help more than a bigger, but
                          inferior amp (+250W but more noise, distortion and 100A fuse instead of 60A)
                          750W with a proper installation would be far enough to damage your hearing

                          Try to turn down the amp a bit, and connect only one woofer to it, maybe you will have better sound.

                          or

                          Try to adjust the Input Sens and Input Voltage according to the manual.

                          Also, some questions:
                          How do you wired the woofers to the amp (parallel/serial)?
                          Sealed box with seperate chambers for each sub. Dual 2ohm voice coils where each sub is wired to a 1 ohm load then they are parallel to eachother to bring it to a 2 ohm load at the amp.

                          Also just for your information the HD750 amp runs off an 80amp fuse. I ran into that info alot in my research that its advertised as a 60amp but in reality it requires an 80.

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                          • #14
                            If the gain is all the way up, you might need to look at getting a preamp. You should always try to keep the amp at no more than 3/4 gain, any more, and you are adding more distortion to the output. I have proven this in my own setup-before my preamps, I had all the gains all the way up, and the sound was adequate, but never as good as when I had a normal hu. After the preamps, i was able to turn down the gains, and the sound is much better, and I am much more satisfied with my setup.

                            If you love loud bass, then a preamp will only help make it better.

                            *phone post*
                            My OLD 2001 Mitsubishi Eclipse GT:
                            "The Project That Never Ended, until it did"


                            next project? subaru brz
                            carpc undecided

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                            • #15
                              Originally posted by bratnetwork View Post
                              Sealed box with seperate chambers for each sub. Dual 2ohm voice coils where each sub is wired to a 1 ohm load then they are parallel to eachother to bring it to a 2 ohm load at the amp.
                              Wait.. two 1 ohm with parallel wiring is 0.5 ohm...could be a problem...

                              To get them wired to 2 ohm, you need to wire the voice coils in series to 4 amp, and then wire
                              the two sub parallel. Or wire the coils parallel to 1 ohm, and then the subs in series to 2 ohm.

                              Or maybe I just misunderstood what you are saying.

                              Originally posted by bratnetwork View Post
                              Also just for your information the HD750 amp runs off an 80amp fuse. I ran into that info alot in my research that its advertised as a 60amp but in reality it requires an 80.
                              You just read that you should use 80 amp, or it really baked the 60 amp fuse?
                              Well, the manual says 60, so if it doesn't works that way, you should take it back to JL Audio.
                              If the amp burns the 60amp fuse, there should be a problem. +20A is not acceptable,
                              especially not from JL Audio.
                              Check my worklog:
                              Corsa + Atom + Gentoo Linux + 9" capacitive touchscreen

                              Lord of the boards: DFI CP100-NRM

                              "Or you can try Ubuntu, but than don't tell everyone you are using linux,
                              because it's just a secret unreleased prebeta of Windows 3829" :P

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