new here have a few questions about new box build

[repobud]

Little backround 97 f150 stock alt. Diehard agm battery. 0ga power and ground. Inno 1500d sub amp. I ordered 4 vvme 10s right before they stopped selling them and was only able to get 3. With no time to build a box I bought an atrend bbox (roughly 2 cubes slot ported) I sealed one speaker hole with mdf and mounted one sub inverted in the other hole. It sounded great and impressed everyone that heard it. Now I finally had some time to build a box I chose birch ply (it was free) played with a box calculator app. And came up with a 3.3cuft box for 3 10s tuned to 42hz with 2 3" round ports. I Built the box and installed it tonight. I'm disappointed to say the least it doesn't come close to the boom the single 10 was putting out. I'm moving a lot of air it feels like a wind tunnel In The truck but not a lot of sound output. I was thinking of pulling the subs and inverting them to increase airspace. I'm Interested in your thoughts...thanks

[Triticum Agricolam]

42 Hz is tuned pretty high, though depending on what kind of music you listen to it might be fine.

Two 3" ports is nowhere near enough port area, it's only like 14 sq inches. You should have around three times that much.

[repobud]

I did some research before building and read that 42hz will play down into the 20's and up into the 60s so it was a good all around tune? As far as ports your saying I should have 6 3" ports total? Seems like a lot but it's easily done. Maybe I'll add 2 more and see how it reacts.

[Triticum Agricolam]

I did some research before building and read that 42hz will play down into the 20's and up into the 60s so it was a good all around tune? As far as ports your saying I should have 6 3" ports total? Seems like a lot but it's easily done. Maybe I'll add 2 more and see how it reacts.

Just how far you can play below tuning depends on a lot of different factors, but it's highly unlikely you are going to get output into the 20's, if you are tuned to 42 Hz your output is probably going to be pretty much done around 35 Hz. Also, as you get below tuning you cone excursion increases very quickly so you can get into trouble pretty quick if you are tuned high and don't have your sub sonic filter set appropriately.

Adding port area will help, but if you add more ports you will have to make you existing ports longer to keep your tuning the same. If you are going to go to that trouble you might as well make everything longer to get your tuning down to 35 Hz or lower. Hopefully you can fit the ports in your box.

[Joe X]

You may be needing something like 3 4" round ports and I am guessing your box is miscalculated, post pics and a sketch of the box you made and the prefab.

[repobud]

I finally got some seat time in the truck I added two more ports and it sounds much better but definitely not hitting the lows I downloaded a tone generator and I get the most output at around 53 Hertz it decreases as I go down and anything below 42 is pretty bad all the ports are the same length 4 inches maybe I'll pull the ports out and try extending them the box came out pretty nice so I'd like to try and salvage it rather than start over. I'll post pics tonight thanks for all the info so far.

[Triticum Agricolam]

If you added ports without extending the ones that are in there already you will raise the tuning, which is probably not what you want to do.

If you want to find out where the box is tuned to you can use your tone generator app and look for the frequency where the cone stops moving, or moves the least. It won't necessarily be where the box sounds the loudest.