PA 21" laminar port sub bracking |
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Augusts
Registered User Joined: 07 January 2017 Status: Offline Points: 180 |
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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 |
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smitske96
Young Croc Joined: 16 February 2016 Location: The Netherlands Status: Offline Points: 1092 |
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Looking really cool! Any measurements you would like to share?
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Sypa
Young Croc Joined: 21 February 2013 Location: Croatia Status: Offline Points: 921 |
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Can't help with the. bracing but also interested in some measurements.
Why was the 29 tuning too low? |
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Augusts
Registered User Joined: 07 January 2017 Status: Offline Points: 180 |
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Because 34Fb got us 3,5 db more and a -3db of 30Hz
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Augusts
Registered User Joined: 07 January 2017 Status: Offline Points: 180 |
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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
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AndyWave
Registered User Joined: 30 March 2008 Location: Finland Status: Offline Points: 380 |
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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 |
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torturing electrons since ......
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smitske96
Young Croc Joined: 16 February 2016 Location: The Netherlands Status: Offline Points: 1092 |
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@AndyWave
There will always be resonances due to the port, only question is where
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AndyWave
Registered User Joined: 30 March 2008 Location: Finland Status: Offline Points: 380 |
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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 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.
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torturing electrons since ......
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