Please explain sub tuning

Discussion in 'Home Theater Projects' started by Larry Alan, Dec 14, 2003.

  1. Larry Alan

    Larry Alan Auditioning

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    This is probably a question for the basics forum but I really spend all my time here, learning all I can. I'm committed to DIY speakers. I have my Tempest that I ordered from Acoustic Visions and I took advantage of the recent sale on PE 250 amp.
    Here is my question: I don't understand how a sub is tuned to a certain freq. and what freq. is best for what type of listening? Please explain "tuning"
    Please bear with me on such a basic question, I'm trying to learn.

    Larry
     
  2. Wayne Ernst

    Wayne Ernst Cinematographer

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    Larry,

    From my view, "tuning" could mean a few things:

    1) You have a driver and want to make a cabinet. The cabinet size could determine how low the subwoofer can go. Also, adding items such as polyfill to the cabinet could change the tuning a bit.

    2) While designing the cabinet, one might prefer a sealed box. Another might prefer a ported box. The length and size of the ports have a direct affect on the sound. Also, the box size for a vented sub might need to be enlarged a bit to take advantage of the porting.

    3) Others might prefer adding passive radiators to the boxes when they design and build them. Again, this has an effect on the sound and how low the sub itself might go in regards to frequency response.

    4) Additionally, other "items" might be considered to influence the tuning of a sub some more. Items such as Linkwitz transformers might be used along with some form of equalizer - maybe even a parametric equalizer to adjust some of the frequencies going to the sub itself.

    Those are basically what I think of when it comes to sub "tuning."
     
  3. Patrick Sun

    Patrick Sun Moderator
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  4. Mike Keith

    Mike Keith Second Unit

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    Just remember your Tuning the Cabinet not the driver, the driver is a resonate device and the port is a secondary resonate device that in conjunction with the driver and enclosure will have a specific frequency that will allow the greatest output of that frequency with the least mechanical effort. This is known as the Fb of the box.

    Anyway the link provided by Patrick is most excellent and a must read for the real details.
     
  5. Jonny K

    Jonny K Second Unit

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    I think "tuning frequency" also has something to do with when the sub will start to bottom out/distort.

    My Tempest sub is in a box with tuning set at 15 Hz. Apparently this means that the sub will perform well all the way down to 15 Hz. At this point, the sub is at maximum performance (moving the most). But lower than 15 Hz it won't be able to handle the sound and will pop and bottom out. I think...

    Car subs are tuned for higher frequencies, maybe 30 Hz. This gives them better performance at higher frequencies that are more common in music (because the closer to the tuning frequency, the greater the sub movement and power I guess). But if you use a car sub with 30 Hz tuning on a home theater, it will sound bad because home theater uses frequencies below 30 Hz. By having my home theater sub tuned to 15 Hz, it won't start having troubles until below my hearing range, and I don't think there's much bass in movies that is below the hearing range.

    Keep in mind, this is just my own understanding of the issue - I could very well be wrong!
     
  6. Jeremy Stockwell

    Jeremy Stockwell Supporting Actor

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    Also, remember that it is possible to tune an enclosure too low.

    You probably won't hurt anything by doing this, but you can definitely lose the advantage of porting your enclosure. You'll basically have a ported enclosure that will behave as though it is sealed.

    It's all in the link that Patrick provided, but wanted to emphasize this point.

    JKS
     
  7. Jake K

    Jake K Stunt Coordinator

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  8. Jonny K

    Jonny K Second Unit

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    Ok, so I guess I was wrong. [​IMG]
     

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