Results 1 to 5 of 5

Thread: Subwoofer Enclosure Q-Value ???

  1. #1
    Maximum Bitrate Raas's Avatar
    Join Date
    Jan 2001
    Location
    The Netherlands
    Posts
    626

    Subwoofer Enclosure Q-Value ???

    Hi all,

    I just got my new sub (USB2830), and now I have to make a case for it..
    I have built a box before, by just putting the numbers into blaubox.
    I already know I want a sealed box, my prev was one and I was pretty happy about the results
    But now this sub is a lot better, so I want a better box.
    Now I'm experimenting with the spreadsheet from Brian Steele's DIY Subwoofer Pages.
    But I have one Question.
    What does the Q-value in this spreadsheet mean ?
    I know I can set Q from 0.6 to 1.0 , but what does it do ??
    With some different Q values, the box size will be 2x as big.

    Here are some off the specs of my sub.. (maybe someone else knows a better box for this...)

    Revc (DC VC Res) = 3.6000 Ohm
    Fo (Res Freq) = 29,4787 Hz
    Zo (Zmax at Fo) = 56,0648 Ohm
    Sd (Piston Area) = 0,0491 sqM
    BL (Flux * Length) = 12,2001 TM
    no (Ref Effncy) = 0.6805 %
    SPLo (SPL at 1w) = 90,3463 dB
    Qms (Mech Q) = 5,8790
    Qes (Elec Q) = 0,4034
    Qts (Total Q) = 0,3775
    Vas (Acous Vol) = 110,8172 Liter
    Cms (Compliance) = 323,7024 uM/N
    Mms (Total Mass) = 90,0488 Gram
    Mmd (DiaphmMass) = 83,7929 Gram
    Continous Power = 400 Watt
    Diameter = 12 Inch / 30,48 cm
    Voice Coil = 50 mm
    Mass Added To Cone = 58,50 Gram

    These are all the specs I got with it..
    I was thinking about a sealed box of 37 Liters..
    Anyone prove me wrong ?

    Thanks in Advance !!!
    Greetz,
    Raas - The Netherlands
    ME: VIA epia m10000, lilliput 7', opus 150w, 80gb<br>
    GF: IBM Thinkpad 380, ext. 3.5 80gb, 40x4, PB-IR

  2. #2
    FLAC mp3z24's Avatar
    Join Date
    Apr 2001
    Location
    Chicago Suburbs
    Posts
    1,282
    i am far from an audio experts, but i think this is right:
    i believe the Q value determines the frequency range of the box... higher q values will narrow the frequency range, and opposite for the low...i cant recall which makes the box bigger

    now here's what you can do:
    most DIY speaker designers aim for a q of 0.707 when designing their enclosures.

    i reccomend you take a look at www.diyaudio.com , the people there are VERY knowledgeable adout all things audio, however they usually come across as a bit elite. some of them have homemade equipment that rivals the best commercial components and even betters many of the more store bought crap that the audio industry pedels as "high fidelity".

    dont be affraid of them though, just explain what you are doing and that you are trying to learn the ropes as far as enclosure building goes.

    ~Mike

    edit: i just found this on a speaker definitions page:
    Q - the magnification of resonance factor of any resonant device or circuit. A driver with a high Q is more
    resonant than one with a low Q.

    Qes - the electrical Q of the driver.

    Qms - the mechanical Q of the driver.

    Qts - the total Q of the driver at Fs. Qts = Qes x Qms/Qes + Qms.

    Qtc - value for the damping provided for a driver in a sealed enclosure. Denotes the enclosures ability to
    control the driver response at resonance. Qtc = 0.707 is the optimum value for sealed enclosures, providing
    flattest response and highest SPL for deep bass extension. Enclosures for this value are often rather large.
    Lower Qtc can give even better transient response, down to a Qtc of 0.577 for the best damping and
    transients, but the enclosure is usually huge and SPL's are down. A Qtc of 1.0 is a compromise between deep
    bass and transient response vs. smaller sized enclosure. Larger subs can go with an even higher Qtc, as their
    resonant frequency is often very low, but Qtc's above 1.5 can begin to sound very muddled and boomy, and
    sacrifice deep bass extension and transient response for enhanced mid-bass peaks (louder).
    Single Member of the "1000 Post and No MP3 Car" Club
    PROJECT ON INDEFINATE HOLD... BOUGHT A HOUSE
    2000 Cavalier Z24 [###-------] Only 30% Done ... Still

  3. #3
    Maximum Bitrate Raas's Avatar
    Join Date
    Jan 2001
    Location
    The Netherlands
    Posts
    626
    Thanks for the input !!
    It explain's some things...
    I had designed the enclosure with a Q of 0.7, giving me 37 liters.
    I designed a box of about 40 liters, taking into account that the sub will consume 3 liters in the box.

    inner measurements. 0,35x0,35x0,32m (WxHxD)
    and is made of 20mm MDF.
    The box has no braces.

    Right now it's drying from the glue, after work I will paint it, and tommorow I will put the sub in, and test it in the car..

    I will let you guys know how it performs...

    Greetz
    Raas - The Netherlands
    ME: VIA epia m10000, lilliput 7', opus 150w, 80gb<br>
    GF: IBM Thinkpad 380, ext. 3.5 80gb, 40x4, PB-IR

  4. #4
    Banned
    Join Date
    Jun 2001
    Location
    Adelaide, Australia
    Posts
    687
    20mm MDF??? you sure its not 18mm??? I looked for 18 but was told it was very rare.. :P

  5. #5
    Maximum Bitrate Raas's Avatar
    Join Date
    Jan 2001
    Location
    The Netherlands
    Posts
    626
    I think it was 20, if I'm not mistaken... (otherwise, it could be 18mm... but it's enough for this enclosure)
    My dad is some kind of carpenter, so obtaining these materials is not that hard..
    He brought me a big plate from which I told him to create the box..
    With my dad having more than 30 years experience with wood I'd better let him make the case.. (than, at least all the angels are right.. hehehehehe)
    (I only gave him the measurements, and told him to use lots of, I repeat lots of glue... He wanted to use staples, but I wanted screws and glue)

    I'm pretty curious how it sounds....

    Greetz


    EDIT:...
    I had a box.. But I got a new car.. (whoooo)... so I needed a new box.. (the other one didn't fit and was to big.. 56 liters...hehehehe)
    I had a Peugeot 405 Diesel,
    I Now have a Peugeot 406 Diesel... yeah.....
    runs great !!!

    Greetz
    Raas - The Netherlands
    ME: VIA epia m10000, lilliput 7', opus 150w, 80gb<br>
    GF: IBM Thinkpad 380, ext. 3.5 80gb, 40x4, PB-IR

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •