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Sub completed, need help

Discussion in 'Home Theater Projects' started by Joey Skinner, Oct 8, 2003.

  1. Joey Skinner

    Joey Skinner Second Unit

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    I just finished my first sub, 18 in. square sealed enclosure filled with 20oz polyfill, a Stryke AV12 driver and a Parts Express 250w amp .
    It sounds great at low volume but if I turn the level knob on the amp past 1/4 the cone vibrates excessively with high distortion and sometimes the amp cuts off and I have to reset.
    The amp is wired like this: pos to one coil, neg to the other with jumpers pos to pos and neg to neg.
    Am I expecting too much from this enclosure? I have no experience with subs but I thought I would get more volume without distortion than what I am getting now. Any help would be appreciated.
    Joey S
     
  2. Jake K

    Jake K Stunt Coordinator

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    If I'm reading that right you have the driver's coils wired up in parallel, a 1 ohm load. If it is that would cause high levels of distortion and would shut down the amp. Wire it up in series. See this page
     
  3. Rob Formica

    Rob Formica Stunt Coordinator

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    If I'm not mistaken, each voice coil on the AV series is 2ohms… so wiring them in parallel (like you seem to have them) would give you a 1ohm load to the amp.

    This may be a little much for a parts express standard issue amplifier.

    If you wire them in series, you'll get a much more reasonable 4ohm load... (pos to one coil, neg to the other with ONE jumper from the unused POS to the unused NEG).

    Let us know if that helps and how it sounds...
    Rob
     
  4. Joey Skinner

    Joey Skinner Second Unit

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    Thanks guys, wiring in series solved the amp shut-off problem. There still is a lot of distortion at higher volume. Any ideas?
     
  5. Anthony_I

    Anthony_I Stunt Coordinator

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    TURN IT DOWN, or adjust the bass/Sub channel settingson your unit?
     
  6. Joey Skinner

    Joey Skinner Second Unit

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    I'm totally new at this; I've never had a sub or known anyone who has had one so I don't really know what is normal. The level knob on the amp is set at about 1/3. Any setting above that causes distortion in the low frequencies. I guess what I need to know if this is normal for a setup like mine.
     
  7. Jake K

    Jake K Stunt Coordinator

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    250 watts isn't a whole lot of power to an AV12, that distortion is probably the amp clipping.
     
  8. Brian Bunge

    Brian Bunge Producer

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    You also need to check the sub out level on your receiver.
     
  9. Jake K

    Jake K Stunt Coordinator

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    The level control on the amp is just there to adjust the input signal. If your input signal was unusualy low then the level control would be used to bring it up. Most receivers have a high enough output signal through the pre-outs so that the level control doesn't need to be very high on the amp.
     
  10. Joey Skinner

    Joey Skinner Second Unit

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    My receiver is a H/K AVR-225. Lokking through the manual I don't see a sub out level adjustment. If I need a bigger amp what would you recommend?
    Thanks for the help,
    Joey
     
  11. Jake K

    Jake K Stunt Coordinator

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    On the remote push CH. - DOWN - SET, there you are. [​IMG]
    For a bigger amp look at the Rythmik Basic amp or a pro amp.
    I have an AV15 with the Rythmik and it's not so hard to clip the amp, but I'll wait until it's in the enclosure to decide wether or not it's enough. Mine will be in a large vented enclosure which is very efficient, a sealed box is a less efficient design.
    Try lowering the crossover frequency on the receiver, I think that one can do it.
     
  12. Geoff L

    Geoff L Screenwriter

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    Make sure the encloser has no leaks around the seems, amp, driver, etc. Assuming that this may not have been done already.
    Seal all seems in the box no matter how tight they may fit.

    A "small leak" in a sealed box is NOT going to make a huge night a day difference, but will help to get the most from your current sub.

    As mentioned, you might look into a bigger plate amp like the Rythmik 380. This would buy you a few more adjustments and another 130 watts or so. Won't amount to a major increase in spl, but would allow for more headroom and a small bump in spl.
    The PE-250 would sell easily here, or in the FS area if you were to decided to go with a bigger plate or pro amp.

    If not already, experiment with placement of the sub. Corner loading will get you the most free gain (spl), but may not be the best place for over all smoothest/flattest response.

    As made mentioned above, make sure you have your entire system calibrated correctly and if the {~H/K-225 has a Bass peek limiter, LFE attenuator, ect}~, that it is set properly. This would be a seperate setting from the receivers sub out volume control.
    Not sure if your receiver has this, (others may comment).

    I don't know what the Q and F-3 of your sealed encloser is, but I would think that your current sub should do a decent job in a small to maybe med sized room.
    This assuming your sealed subs Q is around 6 to 7.

    A properly designed ported alignment with your same PE-250 amp would get you more output, but requires a much larger box obviously.

    =======>
    Whats the Q of your encloser along with it's F-3...???

    How big is your room and dose it have openings leaking into other areas of the home??
    =======>

    Regards
    Geoff
     
  13. Joey Skinner

    Joey Skinner Second Unit

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    Thanks, Geoff. The back panel is not glued on yet; it's just attached with screws. I'll get that sealed up then see how it sounds. My living room is 20'w x 15'd x 8'h that opens at one end into a 10 x 10 dining area. I don't know the Q or the F3 of the box. Should I do additional sealing to the driver and the amp? The driver has a rubber ring and the amp has a foam seal.
    I wouldn't be opposed to building a ported enclosure if you think it would sound better. MDF is cheap!
    Joey
     
  14. Geoff L

    Geoff L Screenwriter

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    Joey

    If your holes are cut fairly accurate (the amp & driver), the gaskets should seal just fine. Then just seal the inside seems with sealer. Let it dry before installing the driver as some sealers give off caustic fumes that can eat at the driver.

    As far as a ported design, yes it will play louder certainly... BUT any type cabinet, Sealed, PR'ed, Ported, etc, will only sound as good as the "design" and then it's construction.
    Good reason to build a proven design if your new to DIY.

    I've never used the AV-12, but I do know it's a very capable driver!

    Others who are running the AV-12 and or have simmed/modeled it in different enclosers would be better than I, with no experience with it, to comment on what might be a good ported alignment.

    This "Assuming" you do NOT have box size restrictions, as a Ported Box will certainly be larger.

    If "spl and decent extension" is what you want the AV-12 to produce "given the power your using, then a ported design will most likely be the best & cheapest bet for you....

    Buy the way, thats a good amount of air space your trying to fill with bass. Your current PE-250/AV-12 sealed sub will strugle to fill the room with bass, as you already know. [​IMG]

    Regards
    Geoff
     

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