
Home  Forums  Rules  Articles  diyAudio Store  Gallery  Wiki  Blogs  Register  Donations  FAQ  Calendar  Search  Today's Posts  Mark Forums Read  Search 

Please consider donating to help us continue to serve you.
Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving 

Thread Tools  Search this Thread 
24th September 2007, 07:06 AM  #1 
diyAudio Member
Join Date: May 2003
Location: N. Cal

Formula for pipe Q
Hi All,
I had read somewhere that there's a formula which relates pipe length to circumference and cross sectional area for determining the Q of a pipe. Can anyone provide the formula or point me to a link? I tried to Google this, but was unsuccessful. I'm evaluating a design for a Hegeman style subwoofer, but need to adjust the pipe dimensions to better fit a larger driver. I'd like to find out if there are any constraints I'll need to contend with. 
24th September 2007, 04:37 PM  #2 
diyAudio Member
Join Date: Jun 2003
Location: Chamblee, Ga.

Greets!
The basic material Q I'm familiar with is = (SQRT SoS)/net po, so a 1 m long pipe with a 0.1 m dia = (SQRT~342)/((1*(0.1^2*pi/4)*1.21) = ~1946. Then there's a pipe cutoff Q = Fc/F as discussed here: http://mmd.foxtail.com/Archives/Dige....11.05.03.html GM
__________________
Loud is Beautiful if it's Clean! As always though, the usual disclaimers apply to this post's contents. 
24th September 2007, 05:11 PM  #3  
diyAudio Member
Join Date: May 2003
Location: N. Cal

Quote:
SoS? net po? where does 1.21 come from? And is the above formula for the resonant frequency or the cutoff frequency? 

24th September 2007, 07:02 PM  #4 
diyAudio Member
Join Date: Jun 2003
Location: Chamblee, Ga.

Speed of Sound and depending on who you ask/read, it will vary a bit, but FWIW in case you want to use MJK's TL simming program: 342 m/sec, the one I used in the example
po = weight of air, which varies with temp and humidity, which MJK uses 1.21 kg/m^3 Neither, it's the quality factor of the air mass 'slug', which is what you asked for by description, but I doubt it's what you think you need to accomplish your task. Not knowing the design details of the sub I can't help further beyond saying that scaling rarely works well without knowing how to scale everything, including the driver's specs.
__________________
Loud is Beautiful if it's Clean! As always though, the usual disclaimers apply to this post's contents. 
Thread Tools  Search this Thread 


Similar Threads  
Thread  Thread Starter  Forum  Replies  Last Post 
box formula  crs1  MultiWay  29  23rd January 2008 09:53 AM 
Q formula  PeteMcK  MultiWay  10  17th January 2008 07:42 PM 
ElPipeO (ElPipeMino) ???  JDeV  MultiWay  21  26th October 2005 09:00 AM 
Need help on xover formula  Jay  MultiWay  3  12th August 2003 05:28 PM 
Anyone have the formula for...  Rino odorico  MultiWay  4  22nd January 2003 04:07 PM 
New To Site?  Need Help? 