box help

[THATpurpleKUSH 5,000+ posts]

This is my first enclosure and I want to make sure that I have done everything right. I had a question about the port length. The enclosure calculator is showing total port length of 17.93" but the enclosure is only 17 deep and there is no bend in the port. It also shows the another length figure of 14.375, which seems more correct. Does my design have any flaws? I will have to shorten the port length, as I need it to 33hz and the calculator won't let you alter that figure on your own. Its for 2 Boston G5 12s.

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[bubbagumper6 5,000+ posts]

Your confused on how port length is calculated. The port length is calculated in the center of the port and in that particular design it has to turn that corner and extends 1/2 the port width from the opening.

I know this probably sounds confusing so I'm going to suggest you do some searching/reading on enclosure design.

 

[MONSONwarrior Premium Member]

If you're tuning to 33hz and your port is only 17 inches long you must have some tiny ass port.

 

[bubbagumper6 5,000+ posts]

haha, hey man just noticed you go to UT...I do as well >_>

I would offer to help you build a box but I live in an apartment and have nowhere to do this at.

The best advice I can give you is either take the time to learn as much as you can on enclosure design, or just pay one of the designers the $5 they charge for a design. Learning how to design has it's perks but be warned you will make mistakes and it will take multiple builds to really learn. I've built 5 or 6 boxes now and I still don't know it all...

 

[THATpurpleKUSH 5,000+ posts]

I have the volume and port area correct, I'm just having trouble with the length. The 2 figures it listed were confusing me and I plan on adding a 2nd baffle so I will have to adjust the length for that as well. The port area seems small, but the manufacturer lists a 4x14in port in the manual. I converted it over to slot and kept the same cross area (within .02sq in) for the opening so I guess its right.

 

[marcotheclepto 10+ year member]

2 things firstly 13.5x1.875 is too small a port. try something in the ballpark of 3.75-4 inches wide. will be more sufficient port area. this should drastically change the required length. secondly that other tab you have open, the 12 volt .com is a wonderful resource. if you have any questions or would like one of those "$5 designs" let me know via PM id be more than gald to help you or do a design.

 

[THATpurpleKUSH 5,000+ posts]

2 things firstly 13.5x1.875 is too small a port. try something in the ballpark of 3.75-4 inches wide. will be more sufficient port area. this should drastically change the required length.

From everything that I have read, it seems very important to keep the same cross sectional area for the port when converting round to slot, which I did.

 

[marcotheclepto 10+ year member]

generally round ports have less port turbulence. and in most cases a round port can get by with about 1/2 the port area, (assuming it is flared.) trust me on this one, go up on the port area some and you'll be glad you did.

 

[THATpurpleKUSH 5,000+ posts]

So it is pretty much a trial and error thing then? Any way to use t/s parameters to come close to the ideal port opening?

 

[marcotheclepto 10+ year member]

xmax and cone size are important to it.... but a rule of thumb is 10-16 sq in per cubic ft. depending on the subs. 10 would be something on the sony xplod area whereas dc fi tc sounds IA et cetera would do better on the larger end. just try using the width i suggested and if you have to adjust your outter dimensions to compensate for lost volume and you should be set.

 

[THATpurpleKUSH 5,000+ posts]

How does this look, its about double the port area now, I'll have to add a tiny bit to the 2nd port wall to compensate for driver displacement.