PORTS!!!! rectangle square, how long? angles, corners, stuffing?? everything else - diyAudio
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Old 7th August 2003, 01:22 PM   #1
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Default PORTS!!!! rectangle square, how long? angles, corners, stuffing?? everything else

Okay... I have designed a 60litre for for a Peerless 12inch XLS sub (830500) The total internal volume is 100litres, due to the volume taken up by the port....

Below is a picture..
I have a few questions, is it okay to have a 90 degree angle in the port??

BTW. It took me about an hour to work out how to do this... the final total internal volume is 63litres... then you have to account for the speaker.. the box is tuned to about 29 - 31 Hz.... the final thing will be a 52cm X 52cm X 52cm cube with a slot port the full width of the internal dimension, which btw is 47 cm as I designed the box to use 25mm MDF walls... is there any problem with the design? I thought it was pretty good.. got the volume spot on, and I believe I got the tuning right....

THE OTHER QUESTION!!
How do I measure the length of the port? I personally worked it out by the volume... I knew it had a constant cross section of 47cm X 5cm so I worked out the same volume for straight as bent.. ALSO!! is the gap between the internal end of the port and the speaker baffel big enough? is it a bad idea to have the port sortof facing the rear of the woofer???

THANX!
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File Type: gif peerlesssub1.gif (36.5 KB, 592 views)
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Old 7th August 2003, 01:23 PM   #2
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Also, I have another question... which port configuration would be better?? this one...
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Old 7th August 2003, 01:26 PM   #3
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Or this one..???

THANX,... feel free to use my design.. lol

DOn't worry... they are BMP's but they are small..
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Old 7th August 2003, 01:28 PM   #4
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What the front would probably look like..
hehe

WINISD calculated the air velocity through the port to be 13m/s tops at 400watts.. hehe and thats at 30Hz btw.. any comments? should I begin construction? lol
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Old 7th August 2003, 01:54 PM   #5
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Umm... no one? lol yeah yeah.. lol I should wait.. lol just someone post to say they have read this.. lol
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Old 7th August 2003, 02:42 PM   #6
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Sometimes its fun to talk to yourself.. but not always... I'm going to bed.. SEEYA!! lol
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Old 7th August 2003, 02:57 PM   #7
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personaly i hesitate using a driver that wants such a tiny box with mid tuning and a LONG port.It wastes the 18hz Fs and low efficiency which accompanies the low resonance.

adrian mack <www.geocities.com/adrian_mack >
mentioned this to me,about his PR'd XLS12,how its nearly impossible to build it with a port to optimum specs.

i attempted a ported design,but i always ended up compromising it.


if your using winisd,you could save the project,and add as attachment so i can look over it to ensure im using same inputs.

Quote:
WINISD calculated the air velocity through the port to be 13m/s tops at 400watts
thats fine

Quote:
I have a few questions, is it okay to have a 90 degree angle in the port??
yes

i expect Group delay to be abit high...

personaly id go for the lower quality shiva in a more comfortable sized box tuned to 22hz without 4metre long ports

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Old 7th August 2003, 02:59 PM   #8
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also i think for shelf ports you minus 0.5x port height from the total length because it has different loading to usual.
if im wrong,my jbl2226h is still tuned exactly right with a shelf port anyway:P

www.jlaudio.com ;tutorials;
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Old 7th August 2003, 03:02 PM   #9
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Hmmm.... lol
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Old 7th August 2003, 04:18 PM   #10
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i made a spreedsheet that worked out all my volumes for me,saved alot of time.

also,your group delay is alittle high. 27ms.


i would think about using a smaller sized port for only 75cm length approximately.<trade off port speed,but makes it more managable>

it will never be the best, why not save for a PR and tune 19hz?

i had to wait ages to get my jbl2226..

or u cud just get a shiva in 120Litres...
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