Joe X

The subsonic (high pass) is generally 4th order not 2nd order filter in most amps so it will need to be set higher to better control excursion, also, WinISD doesn't account for cabin gain so your frequency response just show how the box will play outdoors. But you can still compare your plot with a 4.75 net box tuned to 29Hz (the prefab) to see how much are you expected to gain, that actually is useful information you might be interested in.

There is a 6+ dB gain from doubling power and cone area, There is a 3 dB gain from using professional round ports (around tuning). Those can be dramatic gains as long as you can make it all work as it should.

With that sub the DC resistance is given per coil and BL is given for coils wired in parallel so Re = 1.6 ohm. What is more serious is that they don't provide Xmax which limits your ability to predict maximum power for your situation and where to set your subsonic filter. The parameters you are going to use are the only ones you need to have, the others are not necessary, manufacturers usually will give parameters measured with coils wired in series, if you need to wire in parallel you need to divide Re/4 and recalculate BL through the program, you will get a lower BL value. If you need to measure parameters bear in mind that new subs need to be broken in before any measurements take place or the parameters you get are no good for box designing.

here are the two basic types of 6th order bandpass enclosures: Parallel tuned: Series tuned: As you can see with bandpass enclosures you can never see the drivers from the outside.

Sure you can do that for some moderate improvement, larger improvements involve greater cone area like for example doing 2 15s, if doing a larger than recommended box and tuning higher requires you setting up your subsonic filter higher to prevent sub bottoming out.

Depens on what you mean by "together" but if I imagine right you would have a parallel tuned 6th order bandpass, still that would be useless because in such enclosures the chamber sizes are of different sizes, port area and port tuning of each port are vastly different, in other words that wouldn't work at all.

That looks all wrong, check out this thread to learn to use it: Those enclosures are top slanted, look for a commercial design made for your vehicle and try to see how it is done, generally subs forward / port sideways, these boxes are hard to build try to find a prefab for your vehicle that has the right specs but not as expensive as the one from that guy.

Find the volume level at which your head unit clips and never use at that level, the hard part is going to be finding clipping at the output of the amp since it is inside the box to set your gain properly, you would need to open the box and setup the amp gain that way, very impractical.

i am going to guess you have the ZVX 18v2, the prefab box is almost the size of the suggested box, only the port area is a little low on the prefab but not low enough to be of concern if you are just playing music, here is the difference between prefab (yellow plot) and the suggested spec (red plot) in frequency response: Recommended : use the box sub / port up reverse mounting the sub to see any improvement in performance, Prefab with low port area but performance hit to rated power seems low, only marginal improvements from a rebuild to recommended specs.

You are running 1300W of power in your audio, no need for any other electrical upgrades if just playing music, No need to be checking your voltage unless something in your car is not working properly, the amps will work just fine in the 12-14V range no problem. If you are just curious as to why the voltage is being regulated the way it does, just have your electrical checked and then ask your concerns, to me, if your car works fine and your audio works fine I would just leave it alone.

A D2 sub can only be wired to 4 or 1 ohm so my suggestion is to get an amp that is one ohm stable delivering at least 1200W RMS such as: https://nvx.com/products/xad12-1500w-rms-x-series-full-bridge-class-d-1-ohm-stable-monoblock-amplifier Also when running more than 1kw of power is necessary to check your electrical to be able to support the load and if so check that it is in good condition, more so if you intend to run full bridge amps such as these NVX.

Like this is better: Unhappily too busy these days talk to you later on.

It's a matter of trying if that's even possible, but the ones that come with the kit will be optimized.

Well, good call, that fully solves the issue, hope you didn't pay retail price for that amp though as it seems rather expensive for the power delivered.

I lean on building a 10 x Vas box and boot for optimal sub protection but anyways try that out if you want and see how that goes.

The amp will push 600W to one sub at 4 ohm, you can't really do anything about it. But being such a large vehicle I would run both of them and over time upgrade the amp. Said that the sub loudness at 600W as compared to 850W will be about 2dB or less so not much of a difference, just build a large efficient box for it if not changing the amp or the sub.

Not too big of a deal, just cover the hole with some MDF from the inside BUT if the box is a shared port design add an identical piece of MDF in the other chamber to keep volumes identical.

Your D2 subwoofers can be wired to 2 ohm coils in series subs in parallel so no problem there, is just that the amp is 900W and the subs together can take 1900W easily so not getting all the subs can offer with that amp, you will be getting like 3 dB less than possible (not too much). To compensate build a large,efficient enclosure to get more out of them.

Bear mind that you only need to be loudest at the microphone and not everywhere, you can achieve sound pressure orders of magnitude above of what power can deliver just by promoting constructive interference avoiding destructive interference and by using resonance, also by using extremely efficient custom drivers you can gain a lot, standard "Daily" subs are ridiculously inefficient, like 0.1 percent so that 99.9% of the energy (amp power) is lost to heat and only that 0.1 percent or so is converted to acoustic power. Also when you see extraordinary achievements like 185 dB you know that likely physicists using advanced hardware and software tools are involved to optimize the system not some guys putting together stuff just to see what happens. This is just to give you some idea, and not extend the post too much.

You need to specify what's your vehicle, what is the sub model the box specs and some pictures if possible. Looks like a box issue, installing a DSP could help flatten your response but not the other issues, in some situations inverting the phase of the signal to the subs can help some cancellation issues, other times box location / sub, port firing direction etc can help. try what is suggested and if you still not get results then provide the details I asked about above.

I guess you could install your current box subs / port up in the trunk of your equinox and see how it goes. Now being in a SUV (larger cabin) calls for larger subs just to try to be as loud as before, say 2 15s subs up port back (2 sa15s for example if you don't want to upgrade power) . that would be ideal, I wouldn't bother to build a new box for 2 12s.

I was thinking of condensation of ambient humidity for example, which in the longer term can be harmful to the sub but you make it work man, let us know what you did and how it turned out.

As long as you isolate the front wave from the back wave and the sub is not enclosed in a <10 Vas airspace you have IB for all practical matters, I don't know what issues you will face cutting such a big hole in your truck or if just a boot will weather proof your sub but other than that it should work.

I don't know if I could call that weather safe, an enclosure that is at least 10 times the sub Vas will act very much like IB. Here is a crazy project you can take a look at that shows what to expect from that sub as well as an original way to achieve IB in a medium size vehicle where a very large enclosure is not an option.

So what is your vehicle and budget.