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Sealing a vented magnet speaker

Discussion in 'Amps and Cabs [BG]' started by kringle77, Oct 11, 2013.


  1. kringle77

    kringle77 Supporting Member

    Jul 30, 2004
    Massena NY
    I am going to be building a sealed cab based around some eminence alpha-10a woofers. They work pretty good and have a good tone for bass. But, they also have a bit of a spike at 3khz which can get clacky if you boost treble on your amp. Im going to try a parallel notch filter to remove this first but, I also had another idea.

    Replacing the hard paper dust cap with cloth or zurrite will smooth out that peak and possibly sound great. But, the alpha has a vent in the magnet to cool the coil. If you remove the solid paper dust cap the air can escape through it and therefore the cab wouldnt' be sealed anymore. So, the question is, can I simply seal up the vent and rely on the cooling of the cloth dust cap? This seems to be exactly what is done on the B810 driver, webers, vintage ampegs, etc.
     
  2. 1958Bassman

    1958Bassman

    Oct 20, 2007
    Lots of vented pole pieces have a hard/non-sealed duct cap. If the cone moves out, it sucks air in and when it moves back, it pushes it out. I don't see a problem. If the dust cap is cloth or has a screen, how would it cause air to move as efficiently?

    What is zurrite? I googled it and found nothing but a link to this thread and the rest were in German.

    If you have a peak at 3KHz, do you really need to boost the treble?
     
  3. kringle77

    kringle77 Supporting Member

    Jul 30, 2004
    Massena NY
    I meant zurrette. Basically mesh. I'm pretty sure sealing the vent and replacing the dust cap will cool the coil in the same way. It would cool from the front rather than the back. I'm really wondering if there are any other un-knowns. I've already tried this with another driver and it worked fine.
     
  4. seamonkey

    seamonkey

    Aug 6, 2004
    Don't boost the treble or notch filter is the best. Changing the driver method of cooling doesn't sound so good.

    Or put a passive shield of piece of acoustic foam in front of the driver to smooth down the highs. It's usually a little bridge of plywood with a center disk sitting in front of the dust cap.
     
  5. Arjank

    Arjank

    Oct 9, 2007
    Above Amsterdam
    I did remove the dustcaps of 4 Alpha 8a's I used for a 48. Then I installed aluminium phase-plugs to conduct the heat away from the voice-coil (I did blow an Alpha8a before this modification, afterwards it could take hell of a lot more power). This mod also smoothed out the response up to 4khz, no resonance peak anymore.
    So best would be to install a phaseplug, after you remove the dustcap. The magnet vent is there for cooling and for lowering mechanical resistance in the moving parts of the driver.
     
  6. tjh

    tjh Supporting Member

    Mar 22, 2006
    Minnesota
    The alpha-10a is only available in 8 ohms, correct? what are you thinking for configuration?
     
  7. kringle77

    kringle77 Supporting Member

    Jul 30, 2004
    Massena NY
    Thanks Arjank! I'll look into it. I'll try the filter first though.

    Yes, only 8 ohms. Sealed 6x10. When all things are considered the alpha looks like the overall best contender.
     
  8. Jebus, I have listened to your youtube vids of your 12's with headphones, sounded great, just find your niche and play! Tone seeking can go too far.
     
  9. kringle77

    kringle77 Supporting Member

    Jul 30, 2004
    Massena NY
    Oh, that is where you are wrong! :smug: I really enjoy this stuff. And I do play.
     
  10. Tonequest is up to you. I wish you well.

    Just know that a full range mic on your cabs will get you to a wider audience if you play big enough gigs.
     
  11. will33

    will33

    May 22, 2006
    austin,tx
    Arjank has a good point about the vent also lowering the resistance of the moving parts (less air pressure inside the motor). Even if it cooled itself good, you'd still be changing the mechanical specs of the driver to some degree. How much and what effect that would have on it's performance is something I can't predict.

    Sounds like a cool experiment.