Joe X

start with these: Set your bass boost to the zero position Set your high pass filter to the tuning of the box Go through a gain setting procedure make sure the box has no leaks and that the sub is well seated. Even at 4 ohm that amp can put out almost 5K, the sub is only 2000W so plenty of chances of over powering. Lastly post your box design with dimensions of all parts internal and external, i will check the design for you to see if something is wrong.

Really you don't want a ratio higher than 6:1 (say 6 inches wide and 1 inch tall or 6 inches tall and 1 wide for example) going from 20:1 to a 10:1 is not going to help a thing and also using two (or more) ports by itself is less efficient than using one so that divider idea would just make things worse. I am probably a bit annoying now but it's better to know this things, rebuilding a failed enclosure is very frustrating not to mention the ruined wood and effort.

Look I have no crystal ball, I just did an analysis that show chances are quite low, if you can find a video showing two 15s 14 mm Xmax 1000-1500W each doing a decent hair trick in a setup similar to what you intend to do then it might be possible in your case but if you don't have any evidence that you will succeed better not waste time and money, Just go by the numbers, those systems that do good hair tricks are always high cone area, high Xmax and high power 8-10K and up, you know just do your homework, for each successful project there are dozens of failed systems and it's kind of sad to see people putting a lot time and effort to end up not getting the results they wanted.

That calculator usually fails on the safe side giving you a load of port area (some of which you probably don't need) so I am sure it will be fine. The sub is peaky and the bigger than suggested box will help with that so if you are leaning on SPL side you will probably like it .

Thin port don't work at all check out the following thread:

This is what I consider a legit video of 2 15" on 9K: https://www.youtube.com/watch?v=kWVJfTvwftY If you found that hair trick "decent" lets see how much volume is displaced: Zv5 15: Sd = 726.7 Xmax = 35 Vd = 2.543 So about 5 liters of air being displaced through the window were enough for that hair trick to happen, lets see those subs of yours driven as best as possible: Sq HDS3.1 15: Sd = 776 Xmax = 14 Vd = 1.087 So at most you could displace about 2 liters of air through your window. That is 60% less than in the video, So those 15s of yours in my estimation would get some hair movement but nothing more, at least on conditions similar to the video.

Your vehicle is good for the application due to having a small cabin, A wall having 4 15" high Xmax subs and power of 8-10 K likely should give you decent hair tricks rather easy, But you are far from having such a system. As for amps to buy I am sure that Taramps would be a good fit and they are very inexpensive BUT you need an electrical system to match which will be very expensive, really expensive. Honestly they are less expensive ways to move hair, if you don't have the financial support and the time to make it happen better do something else, Your two 15s you are installing will sound fine and be loud but it will be rather hard for such equipment to do hair tricks

Yes, exactly as you say the lower impedance one will get twice the power, Not worth knowing why, better just consider that as a fact and find a solution around it, anyways I leave you a link if you just have to know: https://www.electronics-tutorials.ws/accircuits/power-in-ac-circuits.html

There is no way you can wire together two subs of different impedance that each will receive the same power, you can only exchange one of the subs so that both have the same impedance. In your case that the amp is stereo you could just balance to power match but it would not be optimal.

Don't get me wrong, not saying it will not meet your expectations is just that they list the parameters incomplete and lie about Xmax so that it gives better impression that what is worth,, don't like companies doing that, awesome products never lie or hide stuff from the customer. Anyways let us know how you liked it when you have it running, the suggested box is 2 cubic feet new tuned to 32 and a port area of 31 square inches (low imo).

That 38 mm Xmax it says it has must be peak to peak I believe the real Xmax will be 19 mm, Just look at a sub that has real high Xmax, large surround and tall motor, Never judge any tech by specs alone, price is more indicative of what it is, I am pretty sure you are getting what you pay for with that one, no more. Sorry to insist but if you really want an edge on getting louder, do a 15, box is only a little over a cube more than a 12 and you can get 3-4 dB louder on the same power.

If you wanted to run that amp two 10s was the thing to do, likely the same cone area. But if you now have 3 8s use them all they have pretty low cone area, you can upgrade to a SIA 3500 if the 2500 is lacking. 8s to me are only worth using in under seat boxes for extcab trucks.

Your other option is subs / port up close to the rear gate and use the trunk space between the box and the rear seats.

Two things, not clear on how much clearance you have for the port but is about as much as it's width what it needs also the leftmost sub is in an potentially unloading position. Also nothing prevents you from putting your stuff over the box in the other design, is not like you lost your trunk like you say unless you were aiming the subs up but that's not the case. The slanted box would need grilles for the subs to avoid damage when you put stuff in the trunk. Lastly those subs are 1000W RMS each a 2500W amp is almost as underpowering them. Still congrats on you testing and planning nice effort.

You would probably need an alternator upgrade and a battery upgrade, other than that I don't see a problem. As far as the parts go I think both kicker and rockford fosgate are extremely expensive, also if you are looking for sound quality you have many options other than kicker which are really aimed at SPL, at least you should try to audition the sub and see if it's the kind of sound you are looking for, many people like kicker sound .Also you can build your own enclosure and save a whole lot, No problem to get a quality prefab as long as the specs of the box are right for what you are trying to achieve. So if you don't mind spending a lot more than necessary and don't mind to be on the SPL side of things then you are good to go.

Nice sketches, in my opinion: 1) use the last box style as it will be louder due to the subs being closer to the rear end of the vehicle, use double layer baffle and a lot of bracing as these are higher end 8s. 2) use a constant power amp of the power you intend to run including the Sundown SIA series or just get a more powerful amp so that you can still get your desired power at 1.3 ohm, power is cheap these days so that shouldn't be a problem. 3) call Sundown for box specs or wait for them to come out before building anything so that you don't have to rebuild a box. Great work, hopefully you will build log and review those subs, should be interesting.

Without sub specs you should call sundown and get the optimal box specs and go from there. My only comment is that you might have space for 2 12s in that vehicle which would be far louder, also 3 subs lead to impedance mismatch for most amps, you will need a constant power amp to get the most power form a non standard final impedance, some examples are the Taramps smart series and the rockford fosgate CP series.

They are slow to publish parameters, recently they do on facebook first from what I have seen. You can also break in the subs and then measure the params yourself, there are tools for doing that or you can measure manually.

No parameters for that sub so I can't give you further feedback unless you have them.

8 net @32Hz , 4x6" ports 33 long each seems ok. Turning the ports is OK as long as you use fittings. The question of needing more or not port area depends on power, I imagine Fi gives those numbers for rated power, if you are keeping at or under rates power you should be ok. if you will be running 10-20% over rated power then you may need more port area.

A given port area for example 37 square inches will guarantee that you won't get port compression (output loss) or port noise in the 0-2500W RMS power range for a tuning of say 33Hz and a net vol of 2,2 cubic feet. So running less power to a box that is designed to 2500W can't be considered as having excess port area when playing at a given power or have any consequence on how it plays. Some people use port compression as a part of the design but that is a whole different topic,

Yes, I am using bassbox pro which you can buy if you want here: https://www.ht-audio.com/pages/BassBoxPro.html The results are custom to your sub electromechanical parameters that the manufacturer of the sub provides and the stated power and a tuning of 32Hz. That calculator you are using is ok to use if you have an unknown subwoofer that you don't have any data on and you want an estimated port area to go by rather than picking a random number. But as you can see it can lead to ridiculous results, if you did 59 square inches of port area the port would need to be extremely long and that would lead to poor performance and you could also get port resonances which absolutely you don't want, I absolutely recommend going with the 2500W port area, about 35-38 square inches not the 1500W set.

Ok the proper port area based on the T/S parameters of that sub to get less than 25 m/s of port airspeed is as follows: At 2500W RMS power : 2.0 cubic feet = 35 square inches of port area. 2.5 cubic feet = 37 square inches of port area. At 1500 W RMS power: 2.0 cubic feet = 28 square inches of port area. 2.5 cubic feet = 30 square inches of port area. I recommend to use the full power port area spec because at some point you may want or be able to run that power and you don't want the box to lose dBs due to low port area. Also you should consider no less than 3/4 wood, double layer for the baffle and strong cross bracing for your box.

What sub model are you going to use and how many subs?

Proper box spec for a subwoofer is not only is defined by net internal airspace and tuning but also PORT AREA, that information you can find from the sub manufacturer or if not you need to calculate it. SO... Those under seat enclosures usually have LOW port area and LOW mounting depth for the sub or subs and generally are poor performers, made mainly for lower power low mounting depth subs. Probably would do a couple of 500W 10" subs, is what would expect to work there and no need for more than a 1500W amp to run them. That is mainly due to the low port area those boxes usually have (and never specify to the customer). Finally there are many subs not just sundown and SSA, SSA like the big boxes, there are many SQ subs working in smaller enclosures.