Very Minimal Sub Response...

Discussion in 'Home Theater Projects' started by MikeGee, Apr 9, 2006.

  1. MikeGee

    MikeGee Second Unit

    Joined:
    Dec 11, 2004
    Messages:
    291
    Likes Received:
    1
    I put together a 15" Quatro with the 240watt amp that everyone else seems to use.. its in a 5.5cu ft enclosure, ported with a.. hmmm i believe it was a 4"x10" port.
    Problem i'm having which i am guessing could be the port length.. i find the sub is barely doing anything during a movie. Super heavy bass movies (U571, Finding Nemo) the bass is crazy at certain scenes. However after just watching King Kong.. i couldnt believe the lack of any response from the sub.. to the point where it seems like its broken until i put somthing which is only super low bass. This is growing to be the case with any movie i throw at it.

    I tried playing with crossover settings on the receiver and on the plate amp with very minimal success. Tried tweaking it with Avia.

    Just curious as to what you guys would reccomend... and or any suggestions
     
  2. Brent_S

    Brent_S Second Unit

    Joined:
    Oct 5, 2000
    Messages:
    472
    Likes Received:
    0
    You need to get some test tones or frequency generator software and take measurements from your seat. Sounds like you could be sitting in a fairly broad null for certain frequencies. What are the dimensions of the room and connected areas? Have you tried moving arond the room during the "bassless" scenes where you're expecting bass? If it's a null, you should be able to find the missing bass as you move around the room...especially in the nearfield of the sub. What does something like the subwoofer sweep in the THX optimizer sound like...relatively smooth from top to bottom or wildly varying levels until the sweep finishes?

    WinISD says a 4"x10" port tunes 5.5 ft to 21.78 hz. Not sure what you were aiming for, but the SA-240 will start rolling your bass off below 20hz anyway. Dropping the tune to 20hz only gets maybe .5db more output at 20hz. Looks like a pretty good design.

    Another highly unlikely explanation for good bass from some movies/music and not others is the "missing" bass is well below the 20hz cutoff of your system.

    Haven't seen Kong yet...is it possible you're expecting something that's just not there. What other movies have similar results?

    -wbs
     
  3. Brent_S

    Brent_S Second Unit

    Joined:
    Oct 5, 2000
    Messages:
    472
    Likes Received:
    0
    Oh, yeah. You mention playing with the xover on the amp. If you're using the xover in your receiver, just turn the xover on the amp to it's highest setting to get it out of the way. You can get some wierd interactions if you start cascading different xovers.

    Did you try reversing the phase on the sub?


    wbs
     
  4. David_P

    David_P Stunt Coordinator

    Joined:
    Dec 12, 2003
    Messages:
    149
    Likes Received:
    0
    smells like crossover or receiver setting issues to me...

    Check receiver setting carefully. Speakers set to large or small? x-over setting? LFE level?
     
  5. MikeGee

    MikeGee Second Unit

    Joined:
    Dec 11, 2004
    Messages:
    291
    Likes Received:
    1
    My speakers are all set to small, bass is set on the receiver to 0db gain.
    Xover on the receiver is set at 80hz, the xover on the plate amp was set to around 130hz but i just set it to max 180hz (as suggested)
    I know the back corner of my room is where there is mega bass gain but my couch isnt anywhere near there nor can it be. I was standing in the back corner of the room and the bass was almost unbareable. Yet in the seating area its much much quieter.
    I'm starting to think of just relocating my sub somewhere else in the room because anywhere along the front is getting minimal bass response.
     
  6. Brent_S

    Brent_S Second Unit

    Joined:
    Oct 5, 2000
    Messages:
    472
    Likes Received:
    0
    If you can manage it (5.5 is a pretty big box), put the sub in your primary listening position and then walk/crawl around the room listening for the best bass response. Then place the sub in the best sounding location. Sometimes moving the sub as little as a foot makes a huge difference.


    wbs
     
  7. MikeGee

    MikeGee Second Unit

    Joined:
    Dec 11, 2004
    Messages:
    291
    Likes Received:
    1
    Cool, thanks for the help guys..
    I'll try that suggestion Brent... Just wondering if you can reccomend a movie with a certain scene that has pretty good mid-bass to do a quick setup with.
     
  8. eric nyhof

    eric nyhof Stunt Coordinator

    Joined:
    Mar 10, 2002
    Messages:
    76
    Likes Received:
    0
    another thing to check is the phase. If you amp has a phase switch try changing it back and forth.
    I was getting a giant null around 60 hz. with my sub. I changed the phase and it went to about a 5 dB null, enough that I could smooth out with the parametric EQ on the amp.
     
  9. Brent_S

    Brent_S Second Unit

    Joined:
    Oct 5, 2000
    Messages:
    472
    Likes Received:
    0
    It's hard to judge frequencies in soundtracks without objective measurements. Our brains can create a fundamental that's not there just by hearing the harmonic. Remember, the lowest note on a 4 string Fender Bass is only 42hz...yet a well recorded bass riff can still rattle the walls and give the impression that it's DEEP bass.

    There is a thread over in the speaker/subwoofer area that has objective frequency measurements of variuos movie scenes. That might prove helpful for picking DVD test material.
    http://www.hometheaterforum.com/htfo...hreadid=144887

    Test tones are you best option. I haven't actually worked out how to create an audio CD from them yet, but these sites have downloadable test tones.
    http://www.hometheaterhifi.com/down/
    http://www.realtraps.com/test-cd.htm (mp3 format)


    wbs
     
  10. MikeGee

    MikeGee Second Unit

    Joined:
    Dec 11, 2004
    Messages:
    291
    Likes Received:
    1
    Thought i'd update with my problem i was having...
    very odd problem i was having.. i noticed i wasnt getting much bass at all... I adjusted my plate amp a bit and after i played with the "Gain" dial (just putting it up and down quickly while having Get Rich or Die Trying on) the bass suddenly clicked on.. I have it set at about 50% gain, VERY noticable now.
    For some reason i think i have problems with the plate amp... more so the gain.. Before i was getting some bass output but it was like 10% of what it should have been. Movies are starting to sound good once again... I'm thinking this plate amp is a piece of crap but for right now it seems to work fine. (Parts Express 240watt plate amp)
     
  11. al lout

    al lout Stunt Coordinator

    Joined:
    May 6, 2004
    Messages:
    164
    Likes Received:
    0
    Sounded like you have a problem with auto on on your plate amp. The signal that is sending to your sub isn't strong enuf to power up your sub. I have heard couple of PE plate amps have this issue. You can check that with them. Or maybe get a better subwoofer cable. And also check the cable connection, maybe it might be loose. I would change cable first, if it still does the same thing. Look into your auto on mode on ur amp. Good luck.

    Al,
     
  12. MikeGee

    MikeGee Second Unit

    Joined:
    Dec 11, 2004
    Messages:
    291
    Likes Received:
    1
    i thought it might have been teh wire... personally i don't think the wire i have is much good. I basically have an RG6 cable wire with an adapter to plug in the plate amp and the other end to plug into the receiver. However this wasnt to blame on the wire unfortunatly cause all the connections were perfect. Just curious what kinda subwoofer cable you guys were using and would reccomend?
     
  13. Brent_S

    Brent_S Second Unit

    Joined:
    Oct 5, 2000
    Messages:
    472
    Likes Received:
    0
    Any decent quality RCA cable should do. Maybe try this one if 25' is long enough. http://www.partsexpress.com/pe/showd...number=181-644

    If it's not an auto-on problem like Al suggested, you might have some dirt in the contacts of the gain knob. With the amp off, try rotating the knob from stop to stop a few times to see if that'll clear anything up. I've got a really old B&O receiver around here somewhere that had a similar problem with it's volume know from time to time.

    I'm assuming you have the SA-240 from PE. It's generally considered to be a pretty decent amp. It's possible you got a bad one. If it is the SA-240, PE give's you a 1 year warranty...give 'em a call.

    wbs
     

Share This Page