Reconsidering my choice of drivers...

Discussion in 'Home Theater Projects' started by Dan_M, Jul 2, 2004.

  1. Dan_M

    Dan_M Agent

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    I built a 142.5l Adire style sub that was orignally designed for the famous Shiva. After looking over the gain graph in WinISD it looked like "upgrading" to the more expensive Dayton Titanic MK3 would give me more SPL and a flatter FQ. I didn't notice until it was too late that the Dayton is considerably less sensitive, and will actually play quieter than a Shiva.

    I could probably switch to the Shiva with no cost to me. Do you guys think it'd be worth the trouble? I'm unclear if I'd be gaining or actually loosing any performance by doing so.
     
  2. ThomasW

    ThomasW Cinematographer

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    Say what?

    The MKIII is 1.6 dB less efficient ([email protected] vs [email protected]). But given it's longer Xmax, the MKIII can play louder since it has higher Vd, and slightly higher overall power handling.

    BTW, what's FQ?
     
  3. Dan_M

    Dan_M Agent

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    I meant FR, frequency response, sorry. How does Vd affect things? I've been staring at all these driver parameters and don't really know what 90% of them mean. From what I understand about efficiency I thought the Shiva would get louder with less power. Looking at WinISD it looks like the Shiva has about 3db of output over the MK3.

    Another thing I was wondering about is excursion. How easy are people bottoming out their 142l subs? My reciever has a 10db attentuate setting I had to turn on to keep things from getting distorted. I'm only running a 250W amp into it.
     
  4. ThomasW

    ThomasW Cinematographer

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    Vd is volume (amount) of air displaced by the total in/out motion of the cone. It's calculated by multiplying Xmax times Sd. The higher the Vd (meaning the more air is displaced) the louder a driver can play.

    You need to understand that sub performance is highly room dependent. So there is no generic answer to you question.

    For most people using a 12" driver, 250 watts is plenty
     
  5. Cam McFarland

    Cam McFarland Supporting Actor

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    I can add very little amp gain to my 214l (I think)ported Tempest without it really getting noisy...( noises you DONT want to hear)
     
  6. Dan_M

    Dan_M Agent

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    Before I attentuated the LFE signal 10db on my reciever the sub made some pretty horrible sounds. Does a bottoming driver always make a metallic clang? Mine didn't do that, it just sounded horribly distorted like it was going to tear itself apart.
     
  7. Cam McFarland

    Cam McFarland Supporting Actor

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    That sounds pretty close to what mine will sound like.
    Everybody always describes it as you did, a "meatllic clang".
     
  8. Dan_M

    Dan_M Agent

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    Is it a pretty safe bet that if I'm ok during Darla's tank tapping I'm calibrated at a safe level? So far I havent heard any material that works the sub that hard.
     
  9. Cam McFarland

    Cam McFarland Supporting Actor

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    I just watched that movie for first time last weeekend.

    I was adjusting the volume through the whole movie!
    There were several times that I had to back it done.
    Unfortunately, even though that scene is talked about alot, I cant remember it...dang adult ADD....lol
     
  10. HowardLi

    HowardLi Extra

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    Sensitivity is how loud a driver can play with a given amount of power. The higher the sensitivity, the more "efficient" the driver.

    Vd is the maximum SPL limit of the driver at any given frequency. So if you have a driver with a Vd of about 3L and a sensitivity of [email protected], and a driver with a Vd of about 2L and a sensitivity of [email protected], the driver with 3L of displacement will have a higher maximum loudness (SPL). But, to reach an SPL that both drivers can play, the driver with the [email protected] sensitivity will use about 1/4 less power.

    Also, you need much more Vd to play at the same SPL as you go down in frequency. If you halve the frequency, you need four times the Vd (which is 16 times the power) to maintain the same SPL. If you want to increase SPL by 6dB at the same frequency, you need twice the Vd (which is 4 times the power). By the way, that doesn't take into account power compression.

    Clear things up?
     
  11. Dan_M

    Dan_M Agent

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    I think I'm beginning to understand. Vd is the volume of air the driver can displace, the product of its xmax and cone surface area. To play low frequencies loud you need to displace more air. From what I've read the Dayton sacrifices some efficiency for displacement over the Shiva.

    I wouldn't be gaining anything by going to a more efficient driver in my enclosure. I know I already have enough power(250W) to push my driver to it's excursion limits, so improving efficiency doesn't really matter.
     

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