Sub problem still existant!!! What is this?

Discussion in 'Archived Threads 2001-2004' started by Greg P, Apr 15, 2002.

  1. Greg P

    Greg P Stunt Coordinator

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    Arrrrgh!

    I got my sealed 1503 up and going about a week ago. I had a problem a week ago which was partly due to my cabinate not being sealed. I have checked as far well as I can by ear and there are no leaks. I still have this bad distortion or tapping at lould volumes, around -10 with bass heavy music. For example I played some rap music to test my new filter setting ( with only 3 filters which sounds awesome this is the best sounding sub Ive ever heard.) Slim Shady (Intro) and the bass will just all of a sudden go to a bad distortion or something. The bass will go from boom, bom, bam(along with the song) to blaaam, bluuum,(basicly sounds like crap, not listenable) and the cone appears to be smacking something. Its just all of a sudden, not like the air leak. My amp is not clipping, nor is the BFD. I have a crest LT-1000 with 1300 watts, so it should not be bottoming out. Could this be a leak really small that Its only noticable, on loud passages, ( I dont think so though because its just happens all of a sudden, it is or it isnt) Is this distortion? Is there any issue with my tad bit higher Q of around .63 or .64 with using the BFD? I really need help guys.

    Thanks
     
  2. Greg P

    Greg P Stunt Coordinator

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    Any ideas guys?
     
  3. Richard Greene

    Richard Greene Stunt Coordinator

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    When I first hooked up my Behringer Feedback Destroyer to my Tempest sealed low Qtc. subwoofer everything sounded fine at modest volumes ... until I cranked up the volume and then the same type of distortion you are describing happened to me.

    The solution, and I have no idea why this solved my problem, was to change the BFD settings from the standard home -10dB setting to the pro audio +4dB setting

    (two switches in rear). Problem disappeared instantly.
     
  4. ThomasW

    ThomasW Cinematographer

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    Greg

    You can't effectively test for air leaks by ear. Use smoke.

    When testing Tube-zilla it was fine at low-moderate volumes. When the pedal hit the metal, there were some pretty weird sounds that were the result of air leaks

    Try Richard's suggestion. Also there are numerous switches on the back of the LT-1000, make sure you have the proper settings.

    Finally it's certainly possible that you're overdriving the system. At what SPLs is the problem occuring?
     
  5. Richard Greene

    Richard Greene Stunt Coordinator

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    I re-read the original post because I thought you wrote that you had solved the air leak problem and this noise was a new problem ... but maybe you still have an air leak.

    A loose driver and/or a small air leak in an enclosure that holds a powerful bass driver can make a huge sound -- I don't know why it gets so LOUD ... but after 30+ years of building speakers I'm used to this problem, and I no longer faint, believing I've just destroyed my new driver!
     
  6. Greg P

    Greg P Stunt Coordinator

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    Ok,

    I tried the +4 db and its seemed to give me more headroom before the problem was happening, however I did try to tighten the bolts a smidge more so Im not postitve, I dont know why no one usees the +4 db setting, it appears to give you more headroom before the BFD clips. I am going to take the woof out tomorrow and line the inside of the baffle with weatherstripping. Is this ok. I already have the outer baffle ring line, I think this will help. Is there any very good way to do the smoke test? I guess I dont see how its going to work when the woof is already moving air. I'll try it again but I couldnt seem to see anything.
     
  7. ThomasW

    ThomasW Cinematographer

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    Greg

    To do a smoke test hold a lit cigarette off to the side of the driver frame. If there is a leak it will blow the smoke sideways
     

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