Subwoofer making strange noise during some test tones .......

Discussion in 'Speakers' started by Joe Mihok, May 18, 2004.

  1. Joe Mihok

    Joe Mihok Second Unit

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    I just finished building and testing my Adire Tempest SBB4 sub and I'm quite impressed with the results. It's my first time hearing a decent sub in my HT so I was actually floored when I watched Matrix Revolutions and Finding Nemo over the weekend. Anyways, last night I decided to throw in an old CD full of test tones I downloaded on the internet (15hz-100hz) just to see what this sub can do. Well, all was great until I reached the 23hz mark. While the room felt pressurized and the walls were vibrating, I could also hear a faint pulsating noise. The niose was almost like a very quick "airy buzz" ??? It's very hard to describe. It got more and more intense as it got lower down to about 15hz until I could feel no vibration except for the "airy buzz" (the room did feel pressurized though.). Anyone know what this is and if it can be fixed ? I haven't painted or finished the exterior yet so I can always alter the ports if need be.

    The specs for my SBB4 are:

    Driver - Tempest 15"
    Enclosure - 24" x 24" x 24" @ 194L
    Ports - Dual 3" PVC @ 29.3 cm + internal/external flares
    Stuffing - 64 ounces of PolyFil
    Amp - Kenwood AVR (125watt x2 @ 8 OHM)
     
  2. Jeremy Stockwell

    Jeremy Stockwell Supporting Actor

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    Joe,

    It's hard to say what you're hearing/feeling from your description, but it could be several things.

    Where did your tuning point end up? (25Hz, 20Hz, 18.8Hz) Looks like you ended up using that unusual flange instead of a rounded flare (per spec.). I'm wondering if those could have affected your tuning point and what you're hearing is significant port noise below tuning point?

    Could also be a room node at that frequency? Or possibly just significant room gain below 23Hz? Could be something buzzing in your room making a weird noise?

    Watch out for playing those sine waves at loud volumes. They are totally different than the signal from a bass-heavy DVD. You can ruin your driver if it gets too hot, and I know you don't want that.

    JKS
     
  3. Mike Keith

    Mike Keith Second Unit

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    If it's a ported sub then it sound's like the description of Port Noise. Anything over 18m/s will give you audible port noise. What’s the Fb, volume and port size?
     
  4. Joe Mihok

    Joe Mihok Second Unit

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  5. Joe Mihok

    Joe Mihok Second Unit

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    There was actually quite a bit of air coming out of both ports ......

    All of the info about my box size should be found in my previous posts .....

    With movies cranked very loud I get no port noise at all. Even with Matrix Revolutions cranked and running approx 5 db hot, I get no port noise, just my floor and pant leg shaking insanely. So it does not really affect real world performance ..... I might just ignore the noise produced from the tones until I see this problem actually happen during a movie. What do you guys think ?
     
  6. ChrisBee

    ChrisBee Stunt Coordinator

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    Any chance the buzz is from internal wiring vibrating sympathetically? The sound could be carried out of the port at critical frequencies.

    Is your wadding well clear of the driver and hasn't sagged into the wrong place?

    ChrisBee
     
  7. Joe Mihok

    Joe Mihok Second Unit

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    Nevermind, I was playing the 20 hz test tone after work today while the wife was in the washroom doing her hair. I played the test tone about 5 times so I could isolate the "buzz" and then all of the sudden my wife yelled accross the house, "What the f'ck are you doing ????? My head's going to explode!!!". I quickly started the tone and ran to the washroom and the whole washroom was shaking and rattling with amazing sound pressure. I then walked to various parts of the HT room and indeed the metal lamp + pictures on the other side of the room were creating the noise. I couldn't believe it though, it's unlike any bass I have ever felt or heard, and it snuck so far past the listening position and accross the house!!!. I'm speechless ...... I never knew bass could make the strangest effect happen in ones home ....

    I can't hear/feel the 20 hz tone from the main listening area but I can hear it effect different parts of the house. Does this mean I should re-arrage my setup ? I'm thinking that's what I'll do tonight for fun.

    Anyways, sorry for asking such a silly question when in the end it was indeed vibrations (thanks Jeremy). The sound was just too strange though .....
     

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