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Discussion Starter · #1 · (Edited)
Ok,I've been throwing up the idea of building my own sub,mainly for HT.I've been thinking of building four single 15" ported boxes,one on each side of my mains and directly across from them,one on each side of my couch.That is what my goal is 4,but I might just end up with the 2 next to my mains.
I thought about all four of them being down firing with three ports going out from the back top of box,would the port locations work,what size should the ports be?I was thinking of going with a 24Hx20Wx28D box.With this size box,how low can I get my sub to go?I've been looking at the eD 16o and the ccs sdx15,or even the sound splintter RL-15p.
Besides the sono tubs,it seems like alot of the DIY folks prefer the front firing sub in their builds,is this a better design?I already know that if I go with four subs I will need to wire up 2 4ohm DVC subs to have a 4ohm load going into each channel of a ep2500 amp.
This brings me to power question,If I have 1000 watts going through one channel to feed 2 subs,is each one of those subs seeing 1000 watts or does the wattage get split into 2(with each sub seeing 500 watts)?
just trying to figure out a game plan for my tax return:R
 

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For optimum HT performance the parameters of the sub determine the box size. Of the 3 subs you mentioned the SDX15 would model the best in the 24Hx20Wx28D box size which is about 5.5 cu.ft. net volume.
Green is the SDX15 in 5.5 cu.ft tuned to 20 hz. Input power is 1000 watts with a hi pass filter at 15 hz. The port would need to be 6" diameter and 30" long.
Orange is the SDX15 in 10 cu.ft tuned to 18 hz with 1000 watts input power with a hi pass filter at 15 hz. The port would need to be 8" diameter and 36" long.
As you can see the bigger box has a 4 - 5 db advantage from 20 hz on down. It all depends how big of a box you're comfortable with. An EP2500 has enough power for 2 subs but not 4.

sdx15 10 cu.ft..JPG
 

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Discussion Starter · #3 ·
Thank you,I tried to use a box calculator on this forum but didn't have all the volume specs for the box,(bracing port,sub dimentions ect.)
Now instead of having one 8in dia port 30" long,is there any other way to calculate into three smaller ports?
 

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Thank you,I tried to use a box calculator on this forum but didn't have all the volume specs for the box,(bracing port,sub dimentions ect.)
Now instead of having one 8in dia port 30" long,is there any other way to calculate into three smaller ports?
Basically you'd do math.

4*4*pi(8in) = (2*2*pi)x ; x is number of ports

divide across and you come up with x = 4

so you need 4 4 inch ports to match the area of 1 8 inch.

for 6 inch you'd need 2 ports.
 

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You would need four 4 inch ports to match one 8 inch for surface area, but you can use less as it's all about port air speed. The SDX15 in 10 cu.ft tuned to 18 hz with 1000 watts input power and a 8" port 36" long would have an air speed of 21 m/s. Using three 4" ports 28.5" long each would have the same tuning frequency and an air speed of 27 m/s which is acceptable for a HT application.





 
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