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Need Advise on Box i want to build.
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SirrCharles View Drop Down
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    Posted: 08 August 2021 at 8:55pm
I want to build 2 vented bass/sub boxes for my top drivers:

Drivers
I have 2 drivers: fane sovereign 15-600lf 
http://https://www.fane-international.com/view-product/SOVEREIGN-15-600LF - http://https://www.fane-international.com/view-product/SOVEREIGN-15-600LF

WinISD Simulation




Design



Application:
Mainly to play techno.

https://www.youtube.com/watch?v=cElcBi8LZxA - https://www.youtube.com/watch?v=cElcBi8LZxA
http://https://youtu.be/F3tCz_7FT2w - https://youtu.be/F3tCz_7FT2w
http://https://www.youtube.com/watch?v=WzfR2bY6SB8 - http://https://www.youtube.com/watch?v=WzfR2bY6SB8
http://https://www.youtube.com/watch?v=2BK7g-4hPvk - http://https://www.youtube.com/watch?v=2BK7g-4hPvk
https://www.youtube.com/watch?v=BD6npymJ7Mw - https://www.youtube.com/watch?v=BD6npymJ7Mw

I analyzed a bunch of Techno tracks i like with a spectrum analyzer,
and they are all highpassed at 50 Hz. 

So i don't necessarily see a reason to build a sub for below 50hz. 

CrossOver
I want to cross the bass with the top at 220-250 Hz. 

Box Size
I would like to keep the box relatively the same size, small 10-30% max increase could be acceptable.

Questions:

1) Should i worry about the bracing impeding the airflow (creating internal pseudo ports)?
2) Any remarks on bracing strategy?
3)     Did i calculate the air volume properly so: box volume untill port entrance. 
4) Can i expect good similar frequency response as WinISD? Or will reality be completely different?
5) If you have any remarks on my design, please let me know!

Best,
-Charles





Edited by SirrCharles - 08 August 2021 at 8:56pm
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JonB67 View Drop Down
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Originally posted by SirrCharles SirrCharles wrote:


Questions:

1) Should i worry about the bracing impeding the airflow (creating internal pseudo ports)?
2) Any remarks on bracing strategy?
3)     Did i calculate the air volume properly so: box volume untill port entrance. 
4) Can i expect good similar frequency response as WinISD? Or will reality be completely different?
5) If you have any remarks on my design, please let me know!


1) no, i think this will be fine but you'll get a more in depth response from someone with more knowledge of this i suspect. 
2) your left hand panel is totally unbraced. How about putting a shelf or two through it breaking it up into two or three ports equaling the same volume but would brace the end up well. 
3) yes, but subtract any handles if the protrude into that space and the volume displaced by the driver.
4) it will be similar in my experience.  usually close enough to build a prototype and tune from there. Port length normally needs adjusting to get the tuning perfect if you're aiming for something specific.
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SirrCharles View Drop Down
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Points: 8 		Post Options Post Options   Thanks (0) Thanks(0)   Quote SirrCharles Quote  Post ReplyReply Direct Link To This Post Posted: 09 August 2021 at 1:44pm
Originally posted by JonB67 JonB67 wrote:

Originally posted by SirrCharles SirrCharles wrote:


Questions:

1) Should i worry about the bracing impeding the airflow (creating internal pseudo ports)?
2) Any remarks on bracing strategy?
3)     Did i calculate the air volume properly so: box volume untill port entrance. 
4) Can i expect good similar frequency response as WinISD? Or will reality be completely different?
5) If you have any remarks on my design, please let me know!


1) no, i think this will be fine but you'll get a more in depth response from someone with more knowledge of this i suspect. 
2) your left hand panel is totally unbraced. How about putting a shelf or two through it breaking it up into two or three ports equaling the same volume but would brace the end up well. 
3) yes, but subtract any handles if the protrude into that space and the volume displaced by the driver.
4) it will be similar in my experience.  usually close enough to build a prototype and tune from there. Port length normally needs adjusting to get the tuning perfect if you're aiming for something specific.


Something Like this?




Edited by SirrCharles - 09 August 2021 at 1:45pm
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Jo bg View Drop Down
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Internal air volume will be less and port longer than you expect I think. The air volume modelling suggests that you calculated that the port will end straight. In fact as the bracing structr makes a Bend, the port will make a bend and continue along the larger frame of the bracing. You could reduce this by making the bracin frame thinner, but looks like port will at least go till the end of the box. Hope this is clear.... Writing in a hurry on a work pause.


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studio45 View Drop Down
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Points: 3854 		Post Options Post Options   Thanks (0) Thanks(0)   Quote studio45 Quote  Post ReplyReply Direct Link To This Post Posted: 09 August 2021 at 5:30pm
If you brace a shelf port like that, I think it's important to put large holes in the bracing to allow the air to resonate as one mass - otherwise the box starts to behave somewhat like it has 3 smaller ports rather than 1 large one - the tuning and port velocity will be different.
Studio45 - Box Builder Commotion Soundsystem -Mobile PA
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SirrCharles View Drop Down
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Originally posted by Jo bg Jo bg wrote:

Internal air volume will be less and port longer than you expect I think. The air volume modelling suggests that you calculated that the port will end straight. In fact as the bracing structr makes a Bend, the port will make a bend and continue along the larger frame of the bracing. You could reduce this by making the bracin frame thinner, but looks like port will at least go till the end of the box. Hope this is clear.... Writing in a hurry on a work pause.




1) So you mean, there will be a pseudo port/pseudo volume in the current design?
2) You mean bringing the port all the way to the back?
3) This creating a very defined port entrance & length?

Any one else have comments? Thanx!
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Jo bg View Drop Down
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The perspective could be misleading and I could be wrong but looks like the distance from back to end of the port is not much bigger than the port height.
So yes without the bracing allready the port would be like your marked "port length" in third picture. 
Once you add that bracing you can see it extends even more.
Sorry I don't get what you mean with bringing port all the way to the back.

Anyway I would not build a sub that only makes 50. Believe me there is a lot of joy under there. At least 45 pleaseWink
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Points: 1009 		Post Options Post Options   Thanks (0) Thanks(0)   Quote smitske96 Quote  Post ReplyReply Direct Link To This Post Posted: 09 August 2021 at 7:59pm
What kind of portlength did winisd give you? For a shelved port like that, I found that a factor of 0,6/0,7 should be applied to get the real desired length for the wanted tuning. Winisd's given portlength has the expectation that it's not close to boundaries which could virtually extend the effective port. 
Besides the above, I would also aim lower (40Hz for example). My current 6th order BP (with 15DS115) is tued at 38Hz.
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SirrCharles View Drop Down
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Points: 8 		Post Options Post Options   Thanks (0) Thanks(0)   Quote SirrCharles Quote  Post ReplyReply Direct Link To This Post Posted: 10 August 2021 at 3:20pm
Originally posted by Jo bg Jo bg wrote:


So yes without the bracing allready the port would be like your marked "port length" in third picture.



You mean Port bracing or Box bracing?


Originally posted by Jo bg Jo bg wrote:


Once you add that bracing you can see it extends even more.
Sorry I don't get what you mean with bringing port all the way to the back.
In the previous images you could see there was a weird area, marked as a green volume, i called the Pseudo Port, since it looked sort of like a port before a port.

Now i have to port straight, clean connected to the main air volume of the box.


Originally posted by Jo bg Jo bg wrote:


Anyway I would not build a sub that only makes 50. Believe me there is a lot of joy under there. At least 45 pleaseWink


Based on your feedback i tuned the volume and port frequency.
Port frequency is now 37,59 Hz 

Now @ 50 Hz i have -0,4 dB
Now @ 45 Hz i have -0,8 dB
Now @ 40 Hz i have -1,9 dB

I think this should be acceptable.
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SirrCharles View Drop Down
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Originally posted by smitske96 smitske96 wrote:

What kind of portlength did winisd give you? For a shelved port like that, I found that a factor of 0,6/0,7 should be applied to get the real desired length for the wanted tuning. Winisd's given portlength has the expectation that it's not close to boundaries which could virtually extend the effective port. 
Besides the above, I would also aim lower (40Hz for example). My current 6th order BP (with 15DS115) is tued at 38Hz.


I can play with the Port length by changing the width of the port.

Assuming constant Port height:
Seems smaller slot port width -> Shorter port
Seems larger slot port width -> Longer port

I've now re-arranged some numbers in WinISD and it now reaches lower up to 40 Hz   with -1,8 dB

Port Length
So you are saying that whatever port length WinISD comes up with should be reduced with factor 0,6/0,7?




Edited by SirrCharles - 10 August 2021 at 3:40pm
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SirrCharles View Drop Down
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1) Now i got rid of the Pseudo Port, and just connect it directly to the air volume.
2) So Port entrance area in main air volume is identical to exit.

One Port or Three Ports?

1) Does adding the bracing result in creating 3 Ports or is it 1 port?
    Very unclear to me.
2) I've seen a lot Ported enclosures that go around the corner with an L shape.
    I assume this is for tuning during construction?

Bracing Ports
3) Should i get rid of the full port length bracing?
4) Should i reduce to 1 brace instead of 2?
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