Speakerplans.com Homepage
Forum Home Forum Home > General > Advanced Discussion
  New Posts New Posts RSS Feed - PA 21" laminar port sub bracking
  FAQ FAQ  Forum Search   Events   Register Register  Login Login

PA 21" laminar port sub bracking

 Post Reply Post Reply
Author
Message
Augusts View Drop Down
Registered User
Registered User
Avatar

Joined: 07 January 2017
Status: Offline
Points: 112
Post Options Post Options   Thanks (0) Thanks(0)   Quote Augusts Quote  Post ReplyReply Direct Link To This Post Topic: PA 21" laminar port sub bracking
    Posted: 27 October 2021 at 11:58am
I have finally redesigned everything, done test measurements with impedance sweep in a test box, tuned to 34Hz

The last thing on the list is bracing? I understand this is a compromise, because using psychopatic bracing on a PA sub would be very heavy, but still some bracing is needed. I am thinking of using a 15mm ply, I hope you can understand the bracing pattern from the cut sheet. the braces are going to be 65mm plus here and there I would join the opposite corners. As this has a laminar port, the bracing does not go that simmetrically as for a straight ported sub. I am thinking maybe add a central brace horizontally that would join the opposite walls of  the sub. Any thoughts welcome! I have never built such a big box.
Thanks
August



This is the first prototype made from 18mm ply, tuned to 29Hz, too low.
Here I used only corner bracing plus a large wall to wall in the center





Back to Top
smitske96 View Drop Down
Young Croc
Young Croc


Joined: 16 February 2016
Location: The Netherlands
Status: Offline
Points: 937
Post Options Post Options   Thanks (0) Thanks(0)   Quote smitske96 Quote  Post ReplyReply Direct Link To This Post Posted: 29 October 2021 at 3:49pm
Looking really cool! Any measurements you would like to share?
Back to Top
Sypa View Drop Down
Young Croc
Young Croc
Avatar

Joined: 21 February 2013
Location: Croatia
Status: Offline
Points: 871
Post Options Post Options   Thanks (0) Thanks(0)   Quote Sypa Quote  Post ReplyReply Direct Link To This Post Posted: 29 October 2021 at 6:56pm
Can't help with the. bracing but also interested in some measurements. 
Why was the 29 tuning too low?

Back to Top
Augusts View Drop Down
Registered User
Registered User
Avatar

Joined: 07 January 2017
Status: Offline
Points: 112
Post Options Post Options   Thanks (0) Thanks(0)   Quote Augusts Quote  Post ReplyReply Direct Link To This Post Posted: 29 October 2021 at 7:05pm
Because 34Fb got us 3,5 db more and a -3db of 30Hz
Back to Top
Augusts View Drop Down
Registered User
Registered User
Avatar

Joined: 07 January 2017
Status: Offline
Points: 112
Post Options Post Options   Thanks (0) Thanks(0)   Quote Augusts Quote  Post ReplyReply Direct Link To This Post Posted: 29 October 2021 at 7:07pm
Because of that being an allround PA sub that seemed like a lot of wasted energy.  I have only a few unweighted freq measurements indoors that wont give you much satisfaction
Back to Top
AndyWave View Drop Down
Registered User
Registered User
Avatar

Joined: 30 March 2008
Location: Finland
Status: Offline
Points: 377
Post Options Post Options   Thanks (0) Thanks(0)   Quote AndyWave Quote  Post ReplyReply Direct Link To This Post Posted: 22 February 2022 at 9:03am
Hello Augusts

I have drawn something similar to be used with 18sound 18LW2600.
(210L net, fb=31Hz, Ap 600...1200cm2)

Did You measure the port output ie. mic inside port, and were there any resonances because of the port length?

Asks Andy

edit:spelling


Edited by AndyWave - 22 February 2022 at 9:04am
torturing electrons since ......
Back to Top
smitske96 View Drop Down
Young Croc
Young Croc


Joined: 16 February 2016
Location: The Netherlands
Status: Offline
Points: 937
Post Options Post Options   Thanks (0) Thanks(0)   Quote smitske96 Quote  Post ReplyReply Direct Link To This Post Posted: 22 February 2022 at 10:32am
@AndyWave

There will always be resonances due to the port, only question is where Wink
Back to Top
AndyWave View Drop Down
Registered User
Registered User
Avatar

Joined: 30 March 2008
Location: Finland
Status: Offline
Points: 377
Post Options Post Options   Thanks (0) Thanks(0)   Quote AndyWave Quote  Post ReplyReply Direct Link To This Post Posted: 24 February 2022 at 6:54pm
Yes, preferably outside the intended frecuency range...But I have not measured any modern reflex enclosure with venturi port in practise, only on paper and in computer LOL

In my intended design there will be possibility to suck out reflex port resonances in small chamber. Maybe You remember apaxial horns with side chamber opening near horn mouth, I'm going to use same principle to tame lenghtwise port resonance if needed.
torturing electrons since ......
Back to Top
 Post Reply Post Reply

Forum Jump Forum Permissions View Drop Down

Forum Software by Web Wiz Forums® version 12.05
Copyright ©2001-2022 Web Wiz Ltd.

This page was generated in 0.109 seconds.