check these measurements for port?

[05_ZX636 10+ year member]

tryin to work with box calculator on 12volt.com for 2 powerbass 3xl 15's walled in blazer. He said they recommend 40 hz tuning, but trying it at 38hz. He wants port goin across top of box. Box 35 W, 31H, 23D says 12.29 cubes before subs and port. Port 33.5 W x 6 H, 38 hz tuning, says to make port 18.75" long. any idea if this is right. I used re calculator and it comes up totally different. thanks

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[cobretti 10+ year member]

I couldn't be happier with the RE Calculator. I just built a 3 cube box tuned to 33Hz for one twelve TC1000. It absolutely pounds! Sounds Perfect!

 

[RAM_Designs 5,000+ posts]

You have to take into account port and sub displacement, as well as bracing.

12.29ft^3 gross

-2.36ft^3 for port(33.5x6.75x18)

-.3ft^3 for subs

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9.63ft^3 net, not including bracing

9.63ft^3 with a 33.5"x6" port, 18" long, makes for 42hz tuning...maybe 1hz higher after bracing, depending on how much bracing you use.

 

[05_ZX636 10+ year member]

how long to make port to make it 38 hz.

 

[RAM_Designs 5,000+ posts]

how long to make port to make it 38 hz.

You kinda have to mess with the box size and port opening size to get it down to 38hz, because as you add length in the port of the original design, you're taking away air space, which makes for the need for more port length...it's like a slow cycle that takes a lot of added port and decreased box size to really make a dent in the tuning frequency. 9.63ft^3 is too big anyways, as well as that port that gives you 20in^2 of port per ft^3 of box volume. Go with something like 7.5-8ft^3 with 120-125in^2 of port.