Tuning your subwoofer. What's the difference?

Discussion in 'Archived Threads 2001-2004' started by Ken Lopata, Aug 6, 2001.

  1. Ken Lopata

    Ken Lopata Agent

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    What does tuning your subwoofer from 18hz to 20hz do? Does tuning it higher give you more output higher and less lower? My dual Stryke HE15 6 p.r. sub is tuned to 18hz. What would tuning it to 20-22hz do? You can only play so loud anyways. What's the difference? Thanks.
     
  2. Julian Data

    Julian Data Second Unit

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    The higher the tune..the more midbass you get while sacrafices output downlow. Although, anything past the Fb point is pretty much Xmax happy as the PRs and the Drivers are pretty much past their Fb point.
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  3. Ken Lopata

    Ken Lopata Agent

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    Thanks Julian. Is there anything, anywhere that describes what xmax, fb, f3 etc. is. If I new what these terms meant, I could make more sense out of answers and understand the differences in different drivers, subwoofers, etc.
    Thanks.
     
  4. Julian Data

    Julian Data Second Unit

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  5. Brian Bunge

    Brian Bunge Producer

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    To add to Ken's question about tuning, could someone please explain to me why tuning below the driver's Fs gives more protection for the driver than tuning above Fs? I understand that the driver becomes unloaded below Fs and basically acts as a short across the voice coil terminals. I would think that tuning above Fs would cause the response to drop off dramatically more around Fs than tuning below. It's obvious that this is counter-intuitive from what everyone has said here but I'm just trying to understand. The only thing I can think of is that maybe the rolloff is steeper when tuning below Fs than tuning above.
    Would someone please explain this to me? Maybe a graphic example would be more clear to me?
    Thanks,
    Brian
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  6. Jack Gilvey

    Jack Gilvey Producer

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    quote: could someone please explain to me why tuning below the driver's Fs gives more protection for the driver than tuning above Fs? I understand that the driver becomes unloaded below Fs and basically acts as a short across the voice coil terminals.[/quote]
    That's not what happens, Brian. It's not an electrical problem, but an acoustical one dealing with the pressure in the box. Here's my basic understanding of it:
    It has nothing to do with the driver's Fs, it's the Fb of the box, the tuning frequency. In a reflex box, at Fb, the port and driver are acting in-phase. The port resonates in-phase with the driver at that frequency, augmenting the bass, and damping the motion of the driver.
    At approximately 1/3 of an octave below tuning, the port begins operating out-of-phase with the driver. As the driver is excursing out, the air in the port is travelling in, and vice-versa. This creates a situation where there's almost no air pressure to damp the motion of the driver. It's "unloaded", and very susceptible to bottoming.
    Simply put, the lower you tune a sub, the less chance there will be that a frequency will come along sufficiently low in frequency and high enough in amplitude to create this situation. Consider the set of all frequencies below 20Hz on all DVDs. Now consider the set of all frequencies below 16Hz on all DVDs. The 16Hz set is smaller, being a subset of the former set. Based on what I've read, and Pat Sun's experience with the 20 vs. 16Hz tune, there's apparently enough content in that range to make the 16hz tune worthwhile for him, even though you give away some output above tuning.
    Obviously, the higher the tuning, the greater the need for some kind of subsonic filter to attenuate those frequencies below tuning.
    [Edited last by Jack Gilvey on August 07, 2001 at 10:34 AM]
     

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