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Old 9th October 2003, 08:58 AM   #1
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Default slot ports in a small box

could some one tell me how I convert a round pipe port to a slot port I have small box 60ltr with a large port 76mmX 503 mm long Its for a sub thanks
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Old 9th October 2003, 10:09 AM   #2
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or a shelf port which ever is easier thanhs
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Old 9th October 2003, 02:51 PM   #3
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Controlling factor is port area - make the area of your slot the same as area of the round pipe. I think this becomes less valid as ratio between height and width of slot increases, however I have had good results with 10:1 ratio.

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Old 10th October 2003, 03:41 AM   #4
usekgb is offline usekgb  United States
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The tuning frequency of the port is determined by the total volume of air in the port. To convert round port measurements to slot ports, just keep the total area and length of the port the same. This will keep the volume of air in the port the same.

I hope this helps.

Cheers,
Zach
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Old 10th October 2003, 02:12 PM   #5
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Thanks for the answers guys .

but could someone tell me what a shelf port is & how do I change a round port to a shelf port thanks
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Old 10th October 2003, 02:22 PM   #6
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I would think a shelf port is what you commonly see on music instrument speakers - the port is across the full width at the bottom of the cabinet with the timber defining the top of port extending to the front of the cabinet, creating something looking like kitchen cupboard "shelf" - port area below shelf, speaker / grille above shelf.

Same rule applies - area of port same as area of tube, length of port the same (only port length this time starts from extreme front of cabinet and therefore does not extend quite as far into the cabinet).

Cheers
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Old 10th October 2003, 03:41 PM   #7
usekgb is offline usekgb  United States
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Centauri nailed this one one the head. Unfortunately, you can't always keep the total surface area the same with a slot port due to the width of the cablinet. Just make sure that the total volume of air in the ports remains the same, and you'll be OK.

Cheers,
Zach
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Old 10th October 2003, 04:08 PM   #8
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I was going to try a double chamber reflex with slot/shelf porting. I was wondering if there would be a problem with tuning. They were going to be 1/4" high slots the entire width of the cabinet. Let me know if anyone tries it, and how it works out. As soon as I stop being lazy, I might be able to tell you the same, haha.
This is for a P17:
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Old 10th October 2003, 06:44 PM   #9
usekgb is offline usekgb  United States
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I think 1/4" slots might cause air turbulence in your speakers while will sound like ringing coming from the ports. Try to make your ports 1" if you can. This will significantly reduce air turbulence in your ports.

Cheers,
Zach
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Old 10th October 2003, 07:46 PM   #10
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Do you have any idea how LONG they would have to be at 1"!?!?
Seriously, it's not possible in this cabinet.
I was worried about that though. It's definitely a problem with a small opening. That is one reason I put it on the rear of the enclosure. I wonder if the velocity would really be that high, considering there is a lot of area at the port exit (they are fairly long).
what do you think?
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