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Another bass cab project

Discussion in 'Amps and Cabs [BG]' started by leosep, Jun 2, 2014.


  1. leosep

    leosep

    Sep 12, 2012
    Hi, how are you?

    The thing is that i have a little car and i need something compact, something easy to transport for rehealsals . I have one 12" speaker: http://www.mcmelectronics.com/product/55-3242 . it was damaged and someone repaired it for me. And mi brother sold his car and stored his slot port car subwoofer cab. So i was thinking in combining the cab and my speaker. I uploaded the dimensions of the cab. I was thinking of dampening with foam pads.

    Speaker:


    • General Specifications:
      • Nominal Diameter: 12 inch
      • Rated Impedance: 4Ohms
      • Operating Bandwidth: 35 ~ 3.2KHz (-3dB)
      • Power Handling Capacity: 350W RMS
      • Sensitivity (1W/M): 96dB (±3dB)
      • Voice Coil Diameter: 2.5 inch


      Thiele-Small Parameters:
      • Resonance Frequency Fs: 36.23Hz
      • DC Resistance Re: 3.4Ohms
      • Mechanical Q Factor Qms: 2.823
      • Electrical Q Factor Qes: 0.446
      • Total Q Factor Qts: 0.0.385
      • Equivalent Cas air load Vas: 121.67 L
      • Surface Area of Cone Sd: 0.0552 m2
      • Efficiency Bandwidth Product EBP 81.2
      • Voice Coil Over Hang X-max 7 mm


      Physical Information:
      • Cutout: 11.10"
      • Mounting Depth: 5.51"
      • Basket: Die cast aluminum
      • Magnet Type: 67 oz.
      • Cone Material: Non pressed paper
      • Surround: Cloth
      • Dust Cap: Paper
      • Damper: Cloth
    So, should i give it a shot? would you try it?

    Just trying to make something like the Eden EX112...With some usable sound.

    Ill use it with an Ampeg portaflex pf-350.
     

    Attached Files:

    Last edited: Jun 2, 2014
  2. vaesto

    vaesto

    Jun 21, 2010
    Hi,

    When I did a box for my cab I too thought of taking a car sub and couple it with my driver. But every car sub box I've found was either too small or too heavy. But you can just put you speaker into that box and try if it sounds good. Be careful not to blow the driver by over-excursioning it (fart-out).

    Also, you can drop all the measures into bass box calculation programs (WinISO and similar) and see if this box suites your driver.

    P.S. I've actually done this software estimation - this box is way too small for the driver to get the deep low bass. It has F3 point at ~68 Hz and over 3dB peak at ~115 Hz which means "boomy" mid-bass.

    P.P.S. You may cut off the slot making box sealed. It will sound much better.

    Vaesto.
     
    Last edited: Jun 2, 2014
  3. leosep

    leosep

    Sep 12, 2012
    Hi, thanks for the response. I put the values in WinISD but im not sure if im doing it right, i dont undertand WinISD completely. I never know what to look exactly. Take a look.
     

    Attached Files:

  4. vaesto

    vaesto

    Jun 21, 2010
    Box sizes doesn't match in your 1 post and here in winisd. In any case you are looking for the less graph over the 0 Db (red line) and green line crossing the purple one (F3 point) further left (at lower frequency). Try diiferent box sizes and see how the graph changes.
     
  5. will33

    will33

    May 22, 2006
    austin,tx
    The box works out to about 1 cubic foot before accounting for the port and driver. That's pretty darn small for a ported 12. The good news is your driver specs say it could work acceptably well in a sealed box. Seeing as you already have everything there, I would load the driver in it, seal off the port, and experiment with different amounts of stuffing in the box. See if that produces a sound you can live with.
     
  6. leosep

    leosep

    Sep 12, 2012
    Thank you for your responses. Any recomendations on sealing the port so i can unseal it later. Bloking it with foam or something?. Or the only way is cutting and sealing it with wood?
     
  7. will33

    will33

    May 22, 2006
    austin,tx
    I'd be inclined to use wood, but with a bit of weatherstripping or strip of rubber around it for a snug, airtight fit without having to glue it in permanently.

    Just for testing purposes, could just jam some styrofoam or whatever you have laying around in there just to plug the hole and see how it sounds.

    Can also experment with just blocking off say 1/4, then 1/3, then 1/2 of the port to hear what lower box tunings sound like with your speaker.

    Sort of a trial and error/tuning by ear way of doing it.
     
  8. leosep

    leosep

    Sep 12, 2012
    Last edited: Jun 3, 2014
  9. will33

    will33

    May 22, 2006
    austin,tx
    I'd just get a bag of polyfill/pillow stuffing, maybe a pound?, and try different amounts. Not enough can sound kind of boxy/hollow, too much can sound kind of dead/not "lively".

    With the box being a bit smaller than optimal, it'll reduce low bass output, but increase high bass output, like around 100-150hz, but I don't know by how much, just have to try it and see. Some increase there can help it sound fat. Too much can make it boomy where the pitch if the notes loses clarity.

    The box is decent size for a 10". Might work as a sealed 12" but I don't know how well. No modeling programs on the phone. :D
     
  10. will33

    will33

    May 22, 2006
    austin,tx
    You already have the box and the speaker, so you've really nothing to lose by experimenting with it.
     
  11. will33

    will33

    May 22, 2006
    austin,tx
    When you calculate the box size for the speaker, you only use the airspace inside the box, so you measure from inside wall to inside wall, and also subtract the space taken up by the port, the speaker itself, and anything else that's in there like braces, etc.

    If you close the front of the port to make it a sealed box, you can then include the airspace inside of the port as part of the internal box size, but you're still probably down around somewhere 20-25 liters -- 3/4 cu.ft. or so?
     
  12. leosep

    leosep

    Sep 12, 2012
    Hi thank you for your time really. Here is a recording with my zoom h2 of the cab without the polyfill(just sealed with foam and silicone heat gun inside the cab), Im going to buy the polyfill on weekend. Im recording to listen to the difference after. What do you think of the sound before the polyfill? Used a precision bass with seymour duncan quarter pound and everything eq flat in the amp and bass.
     

    Attached Files:

    Last edited: Jun 3, 2014
  13. leosep

    leosep

    Sep 12, 2012
    anyone? :smug::smug:
     

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