# help with modeling/port length



## mcbaker13 (Mar 22, 2010)

so i have a sdx-15 and will be doing an end table build. i had originally planned on doing a sealed box due to the simplicity, my size requirements, and my living environment, but have since decided to go ported for several reasons. i will be reusing a relatively weak plate amp (dayton 240) until my finances allow for an upgrade (im a poor college kid) so i figured i would get more boom for my buck from 240 watts ported versus 240 watts sealed. also, i originally thought my space limitations of about 5.5 cf were too small for ported, but after seeing several others go ported with similar volumes i have decided to do so also.

i finished my finals last week and am ready to begin my project in my off week before summer classes start, but being a mac user, it is hard for me to model my box for tuning purposes. as this will be used as an end table, my box is designed to be the same height and depth as the couch, but the width is not set in stone, although i would like to keep it around 24 inches. the external measurements will most likely be 20hx24wx30d. i tried adapting the port length/volume from fishtanks build, but i was not confident that this would give me the best results so i decided its better to ask for help. so my main question is: what size slot port is required for my box to achieve a tuning of approx 18-20 hz?

construction is set to begin ASAP, the only thing that might cause things to change would be if i can get my hands on a marble slab left over from the construction of a house which i would like to use as a table top, in which case i might have to change some dimensions. otherwise i will be getting corian cut to fit this box. thanks in advance for your help!


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## Mike P. (Apr 6, 2007)

A slot port 2.5" H x 12" W x 32" L will tune 5.5 cu.ft.to 20 hz and ensure enough port area for a 1000 watt amp in the future.


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## mcbaker13 (Mar 22, 2010)

perfect. exactly what i was looking for. would it not be preferable to make the slot the same width as the box (24 inches)?


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## lsiberian (Mar 24, 2009)

I understand your concerns with the complexity of adding port sides. It's really not super complex though. Sometimes cutting a dado makes it easy to mount the port. 

You usually don't want to make slot ports that are thinner than 2". You could make the port 2" x 24" x 52.82", but I think it would excessive 

This lowers the port resonance, but most folks don't have an issue with it. If you are sensitive to port resonance I suggest you stick with Mike P's design or use a P-R.


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## mcbaker13 (Mar 22, 2010)

mikes design it is then. i dont have the cash to shell out for a PR, even with the specials kevin has had on them


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## lsiberian (Mar 24, 2009)

mcbaker13 said:


> mikes design it is then. i dont have the cash to shell out for a PR, even with the specials kevin has had on them


That's what limits us all. :T 

You will want to create the port first. Then Glue the box around it. This will insure you get a solid joint between the port and box.


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## mdrake (Jan 31, 2008)

lsiberian said:


> That's what limits us all. :T
> 
> You will want to create the port first. Then Glue the box around it. This will insure you get a solid joint between the port and box.


Dito :T and make sure to run some type of sealant along the edge of the port to insure that is is sealed against the box. 

Matt


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## Mike P. (Apr 6, 2007)

Don't forget to add the displacement of the port, sub and bracing to the 5.5 cu.ft. net volume to get the total internal volume that you'll need.


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## mcbaker13 (Mar 22, 2010)

i have conservatively calculated internal volume by multiplying 28x18x22 which gives 6.42 cf working internal volume. i figured driver and bracing would bring it down to the afore mentioned volume of 5.5 cf, however i failed to consider port volume. with the port taking up approx .56 cf and the driver taking up .245 cf (calculated by 7 liters x .0353 cf/L) i .believe that will still leave adequate volume for bracing. i appreciate all the help from you guys!


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## Mike P. (Apr 6, 2007)

You have it all figured out, now all you have to do is post a build thread with lots of pics!


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## mcbaker13 (Mar 22, 2010)

I got my marble slab! And it is big enough for my desired dimensions. Would one of you winisd savvy folks mind provding me with a graph of the output I can expect from 5.5 cf tuned to 20 hz with 240 watts of power? Thanks!
_Posted via Mobile Device_


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## Mike P. (Apr 6, 2007)

Yellow is with 240 watts, orange is with 1000 watts.


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## lsiberian (Mar 24, 2009)

Mike P. said:


> Yellow is with 240 watts, orange is with 1000 watts.
> 
> View attachment 21318


I really like the look of that for a 5.5 cuft sub.


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