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help with box for 2 Sundown SA12 V2


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this is my second time building my own box, the first one was super simple i used jbl specs with an areo port and done. this slot port is a little more difficult for me, the box is for 2 sundown SA12 V2s subs up port back thats going in the back of my jeep grand cherokee. the dimensions are height 15" x length 44" x depth 16" .  port is 13.5"x3" - 20" long tuned to ~32hz. im not sure if my port needs to be bigger or not?    thanks for any help

 

 

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Do you ever plan on upgrading that amp to not be underpowering them subwoofers? If so, then that design is good. But if not, then you need to go bigger, like 4.75 cubic foot net and 4.25” of port width. Jacob (ceo and founder of sundown) says SA subwoofers love around 12sq” of port per cube.

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:stupid:“How can we help you?”
:guido:
“And don’t forget to tell them that 
the customer isn’t always right.”

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what size amp should i be looking at? the subs are 1000rms each i saw big d  dyno the jp23 around 2400w @ 1ohm i thought that would be enough. i really want to get this right the first time. buy one amp, build one box.  and thanks for helping i really appreciate it.

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Just because that amp does 2400 rms at 1 ohm and then subwoofers are wired parallel to 1 ohm nominal means NOTHING. You have to factor in impedance rise, which with a bigger enclosure with a smaller port on that subwoofer, I’m guesstimating about a 2.5x rise. So what does that amp do at 2.5ohms? Ac voltage is gonna cause Impedance on the dc resistance differently on each frequency. You could get up to around 5x rise. When the enclosures are smaller, the impedance rise increases. Bigger ports on smaller enclosures cause more impedance rise. Combinations of what subwoofer, what size enclosure and what size port have a impact on a subwoofers NATURAL impedance rise and is now deemed box rise. I’ve seen a wall of 2 18” nsv4s dual 2 ohm subwoofers in a small truck in a way too small enclosure with a way too big driver side port on 2 md12000.1s and barely do a 155 on a 9x rise and when he rolls his driver side window down, the enclosure gets quite. And big ports cause the subwoofers to unload, which what is happening in this case, even when the window is up. Idc what the rms is. Even though rms is factored in to determine enclosure sizing and port sizing. Doing 20sq” or more of port on a regular bass reflex enclosure causes it to minimize pressure build up and unload. Idc the enclosure size or the subwoofers or the rms. That’s what happens. And when a subwoofer is unloading in a small enclosure, it causes the enclosure to have a crazy rise and not get that loud. He thought looking at the winisd info and graph looked good, but when he used the same laptop to termlab that build, wonk wonk wah. But to answer your question. You need a Korean built 4000 watt amp or a Brazilian built 5000 watt amp.

:stupid:“How can we help you?”
:guido:
“And don’t forget to tell them that 
the customer isn’t always right.”

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