Help with formula - Maximizing Performance from Loudspeaker Ports? - diyAudio
Go Back   Home > Forums > Loudspeakers > Subwoofers
Home Forums Rules Articles diyAudio Store Gallery Wiki Blogs Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

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
Reply
 
Thread Tools Search this Thread
Old 16th September 2013, 10:19 AM   #1
eqjive is offline eqjive  United States
diyAudio Member
 
Join Date: Jan 2013
Default Help with formula - Maximizing Performance from Loudspeaker Ports?

Can anyone clarify this formula from the AES paper 'Maximizing Performance from Loudspeaker Ports'? (see attached screen shot). I'm looking to create a spreadsheet (as the paper suggests possible) to determine tuning frequency of heavily flared ports (NFR .5 - 1).

It is formula number 11, page 14 of the paper 'Maximizing Performance from Loudspeaker Ports' or page 32 of the J. Audio Eng. Soc., Vol. 50, No.1/2, 2002 January/February

I'm having some trouble figuring this one out... what are the units to be used if speed of sound is given in meters, what should throught area, diameter, volume etc be?

Can anyone give an example using the formula so I can understand where I am getting confused?

Thank you!!

EqJive
Attached Images
File Type: png Screen Shot 2013-09-16 at 5.04.19 AM.png (104.6 KB, 103 views)
  Reply With Quote
Old 16th September 2013, 10:48 AM   #2
sreten is offline sreten  United Kingdom
diyAudio Member
 
Join Date: Nov 2003
Location: Brighton UK
Hi,

I'd uses cm, cm/s, cm squared and cm cubed for calculations.

Convert C to cm/s and Litres to cm cubed.

Really doesn't matter as long as your consistent.

What you uses to input parameters can be converted
in the calculations, so use whatever input format
you like like C in m/s and Vb in litres.

Note that big ports will reduce the actual Vb.

rgds, sreten.

If its going to end up part of something more complex
standardise on m, m/s, m squared and m cubed for
all calculations and convert the input / output format.

Last edited by sreten; 16th September 2013 at 10:58 AM.
  Reply With Quote
Old 16th September 2013, 10:49 AM   #3
AndrewT is offline AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
I get the impression that everything is in metres.
__________________
regards Andrew T.
Sent from my desktop computer using a keyboard
  Reply With Quote
Old 17th September 2013, 02:11 AM   #4
OscarS is offline OscarS  United States
diyAudio Member
 
Join Date: Jan 2011
As reten said, so long as you're consistent you can use different units.

The main idea is to realize that since c is in units of "distance/time", and frequency is "1/time", you need to cancel out the "distance" unit in the numerator that "c" contributes. That means that the outcome of the square root function has to simplify down to "1/distance". Sure enough, Aeff= distance˛, and the product of Leff*Vb = distance^4. Distance˛/distance^4 reduces to 1/distance˛, the square root of which leads to "1/distance".

So as long as the units for distance are consistent, the formula will churn out the correct numbers.
  Reply With Quote
Old 17th September 2013, 01:50 PM   #5
eqjive is offline eqjive  United States
diyAudio Member
 
Join Date: Jan 2013
Thank you!!! With your help, I figured it out.

- EqJive
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Active high dynamics/SPL & high performance loudspeaker system for my living room…! Robert GS Multi-Way 80 1st December 2016 11:11 PM
Maximizing YouTube download audio quality oltos PC Based 8 26th November 2012 09:41 PM
Class T - maximizing damping factor, any ideas? Disney_SK Class D 51 22nd June 2008 01:56 PM
Loudspeaker formula freedom Multi-Way 17 18th November 2004 09:49 PM
Loudspeaker Filter Formula's Lars Clausen Multi-Way 11 19th November 2003 05:22 AM


New To Site? Need Help?

All times are GMT. The time now is 01:34 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2016 DragonByte Technologies Ltd.
Copyright ©1999-2016 diyAudio

Content Relevant URLs by vBSEO 3.3.2
Wiki