Infrasonic DIY Sonotube

Discussion in 'Home Theater Projects' started by Michael_Collins, Dec 10, 2003.

  1. Michael_Collins

    Michael_Collins Auditioning

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    Hello All,

    I've been reading about Sonotube subs as well as having looked at the various different designs on the Sonosub homepage link.

    After looking at the designs, I've got a few questions and ideas that I'd like opinions on:

    1) It looks like most sonotube subs are single port/single chamber or closed box design. Has anyone tried a dual port/dual chamber (6th order bandpass) design?

    2) I've been playing with LspCAD from Adire.com and came up with a design that looks pretty good for In-room response, even thought the 1 M 2Pi space plot isn't all that great. Essentially, the in-room response is -3dB @ 13.5 Hz and 50Hz. At 20W the output is +/- 1dB 16-45Hz at an SPL of 102dB.

    3) If I ran a Behringer EX1200 out of the LFE channel of my preamp, would it be better to use the LspCAD sub, or go with a couple of butt kickers on a platform?

    4) Any better ideas to boost the SPL at those freqs? An Infinite Baffle design has been recommended to me, but I don't have the physical space to accomodate a design like that without upgrading the house right now (not within the budget constraints) [​IMG]

    5) Will the Bass Expander EX1200 really work down to 10Hz? If so, what's the best way to extend my lower range @ High in-room SPL? I've got cone excursion problems with the Shivas, and the total volume of my box is starting to get huge as I up the driver size.....

    Thanks for any feedback/opinions!

    Michael


    Here are the specifics about the design....

    BANDPASS BOX TYPE 3
    FilenameIn Room Flat Optimized.box
    Rear box
    Vol700.00 l
    Qa30.0
    Ql15.0
    Fill0 %
    Front box
    Vol120.00 l
    Qa30.0
    Ql15.0
    Fill0 %
    Rear port
    Length133.16 cm
    Area324.29 sq.cm
    Dia20.32 cm
    Flange radiusinf.
    Max dia20.32 cm
    # ports2
    Simulation of port non linearity ON
    Res freq.13.50 Hz
    Front port
    Length6.88 cm
    Area81.07 sq.cm
    Dia10.16 cm
    Flange radiusinf.
    Max dia10.16 cm
    # ports2
    Simulation of port non linearity ON
    Res freq.50.00 Hz
    Driver
    ManufacturerAdire Audio
    ModelShiva 2
    Filename
    # drivers2
    Extra mass0.0 g
    Simulation of BL non linearity ON
    Simulation of voice coil heating ON
    Simulation of Cms non linearity ON
    Double voice coil with
    voice coils connected in parallell
    Electrical connection of drivers : Sep. sources
    Room and Cabinet
    Roof height2.600m
    Room depth10.210m
    Room width3.960m
    Speaker pos.X=3.000m Y=0.000m Z=0.750m

    Meas. pos.X=2.13mY=0.80mZ=5.49m

    Reflections from
    Speaker backwall (0.19), Left side wall (0.19), Right side wall (0.19), Floor (0.36), Roof (0.36), Cabinet edges,
    Response 1/3 octave smoothed
     
  2. ThomasW

    ThomasW Cinematographer

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    The answer hasn't changed since you first posted this question on AVS.....

    Infra-sonic (aka sub-sonic) means below the threshold of audibility for humans. This means that it can only be 'felt' = tactile, not heard.

    10Hz is inaudible, 15Hz is inaudible. So all any tuning at ~15hz or below is doing is shaking the room, and it's only doing that IF there is adequate power and displacement available. And believe me, one can't differenciate if a room is being 'excited' by 10Hz or 15Hz info, house shake is the same regardless of frequency

    You're certainly not going to get usable output from Shiva's at those frequencies, that is unless you have a dozen of them....

    Behringer specs are, Frequency Response: 16 Hz to 150 kHz, +/- 3 dB. So I doubt that it's going to be much help.

    You can play with computer models all you want; but in the real world nothing is going to work unless you use MULTIPLE high excursion 15"s-18"s mounted in MASSIVELY big tubes, driven by HUGE amplifiers.

    Or as I stated in my AVS post use the Buttkicker brand of bass shakers...
     
  3. Michael_Collins

    Michael_Collins Auditioning

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    Thomas,

    Thanks for your input. I thought that I'd try here posting here for other opinions as well. I haven't really got much experience with the butt kickers, so I'm not sure if you'd just feel a buzz every time that someone spoke on screen, or if it would just react to the low freq responses. I took a look at their site, and the freq response goes all the way up to 200Hz (if I remember right) for the butt kickers. That just doesn't seem like it would work well with male voices... Would the Buttkickers work well in combination with the EX1200?

    Thanks again. M
     
  4. ThomasW

    ThomasW Cinematographer

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    Any device, sub or bass shaker/ButtKicker, must have a crossover to filter the higher frequencies out of the device.

    Just to make sure everyone's on the same page, the limits of human hearing are usually quoted as being from 20Hz-20Khz. Now if the SPL's are loud enough the one can 'hear' slightly lower than 20Hz, but basically no one can 'hear' 15Hz. A person can feel (not hear) the vibrations created by 15Hz (or lower) sound via bone conduction, and the fact that the room itself will vibrate from the pressure.

    To reproduce sound ~15Hz and below requires (as previously stated) huge woofers and massive amounts of power. Believe me when I say it ain't going to happen with a single Shiva...

    So it's up to you to decide whether or not you really want to reproduce sound frequencies that low, or if you just want to feel the vibrations produced by a device like a ButtKicker.

    Understand that devices like the Buttkickers/Bass Shakers aren't speakers. They don't reproduce 'sound', they're simply an electrical metal hammer that impacts/pounds whatever it's attached to....(floor, sofa, etc.)

    Note that most people are satisfied by having a high output/high excursion sub that's tuned to so ~18Hz or so. Others like the sensation of everything vibrating.....
     
  5. Michael_Collins

    Michael_Collins Auditioning

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    Thomas,

    Ok, taking the cross over into account, I should be ok there because I can limit my subwoofer out line level from my preamp to anything less than 80Hz. But what about harmonics coming off of the sub. Is it possible for the sub to output something other than the freq that it's fed?

    For instance, you feed the sub a 60Hz input, but there is resonance at 120, 180, and 240Hz. How do you account for that in subwoofer design - Do you just make sure to fill the open volume up with lots of stuffing?

    Also, would you get a similar resonance problem from the buttkickers?

    Thanks - Mike
     
  6. ThomasW

    ThomasW Cinematographer

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    >>>>Is it possible for the sub to output something other than the freq that it's fed?

    No

    >>>For instance, you feed the sub a 60Hz input, but there is resonance at 120, 180, and 240Hz.

    These don't go to the sub the crossover filters them out.

    >>>How do you account for that in subwoofer design - Do you just make sure to fill the open volume up with lots of stuffing?

    Damping absorbs some of the higher freq not filtered outby the XO. But it should'nt be over used.

    >>>Also, would you get a similar resonance problem from the buttkickers?

    No they're just an elec hammer not a speaker.

    You might want to read up on loudspeaker design. Start with
    "Great Sound Stereo Speaker Manual" by David Weems and G. R. Koonce.
    Then read "The Loudspeaker Design Cookbook", 6e by Vance Dickason
     
  7. TimForman

    TimForman Supporting Actor

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    If you don't have a spot for an IB go with a QWT. Many have been made and work well, especially if you have somewhere to tuck a 9 ft. tube. If not, a 6 foot tube will work with 6 lbs. of PolyFil. For sub-sonics just use shakers of some kind. There's no point in damaging your home just 'cuz it's cool.
     
  8. Michael_Collins

    Michael_Collins Auditioning

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    Ok, I don't recognise what a QWT is. Can you help with a little more info?

    Thanks.
     
  9. Michael_Collins

    Michael_Collins Auditioning

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    Thanks all. I guess I'm re-thinking my ideas on what I need in a subwoofer. After reading a website on how the ELF function works, I am thinking that I may just build a sealed or bass reflex box and then just use a BFD to equalize the lower freqs up to the rest of the frequency band levels.

    Any idea why this wouldn't work or is a bad idea? I can only think that it would be cutting down on my dynamic range in the sub.

    Thanks again.
     
  10. ThomasW

    ThomasW Cinematographer

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    You'll find that room gain fills in a lot of the lowest octaves.

    Sub's don't really have a lot of 'dynamic range' ( = the difference between the loudest and most quiet passages in the music)
     
  11. Jeremy Stockwell

    Jeremy Stockwell Supporting Actor

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    Thomas,

    I interpreted "dynamic range" in his context to mean "headroom," and eq'ing by BFD or otherwise does, indeed, eat up headroom.

    Michael, maybe you should try the sealed design in room and see what you get. It should be easy to add a BFD if you decide it's necessary after the fact.

    JKS
     
  12. Michael_Collins

    Michael_Collins Auditioning

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    Thomas,
    That's what I think I'm going to have to do. My room is "L" shaped with a Cathedral ceiling in part of it - oh, and it's also open to the basement!!!!

    If I can't get enough EQ with the BFD, I think that I might get a Linkwitz Transform built up and try that with the BFD. Now I just have to make sure that I've got a DIY sealed sub that gives me enough excursion in the drivers to play around!

    Thanks for all the help, and have a Merry Christmas... More next year after I get all the stuff hooked up!

    Mike
     

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