Joe X

Here are the modeling results, as it turns out it's pretty nice driver for the lows working nice in the 5-6 cubic feet net, here are the plots for your intended power on 5 net per diver, 33hz and about 108 square inches of port area per driver: At 5 net the projected response is well within the 28 -45 you wanted Vent airspeed acceptable at 108 square inches per driver. Cone excursion shows where to set your subsonic filter: You can layout at this point BUT i was wondering if those are real max dimensions, specially height, you can go a little above the seat line without issues.

Got your params, glad they were nice enough.

I imagine you are talking about these: https://www.americanbassusa.com/vfl-comp-signature-18d2.html If so there are no published t/s parameters for those unless they are listed in the sub manual. If yes you should picture and post the params otherwise it's impossible to know what the subs need for a box.

The box specs you post result in the following estimated frequency response. In reality that big peak will be softer than shown but the point is that it will not be the flat response you may be looking for.

What's the vehicle?

Connect your amp and when it's working, disconnect the sub and see if the protect light goes away, also read the sub DCR with a multimeter.

If your motherboard box says ready for ryzen second generation processors then that's your problem, you need to update BIOS which you can't without an older processor to boot and perform the update, easy way is asking a shop to do the update for you.

You will need about 100-110 square inches of port area for those 4 drivers on rated power and a tuning in the mid to lower 30s and a net volume of 2-2.5 net per driver. As for your box dimensions you should measure the trunk space yourself, besides your box height can be increased a little without breaking anything.

In your case port area is height x width of the port, if you are not familiar with box design concepts and you don't have tools like the SPL meter and others, probably you should have someone to do the job for you.

Those boxes look solidly built but you are going to want VARIABLE tuning port, not fixed frequency. If you don't have a term lab you can get the SSA APM-2 SPL meter which is good to 174 dB it's considerably less expensive than the termlab. Your subs are good for the application but I can't tell you if your boxes are any good without some basic measurements, port area though seem too low in both boxes, just for that you may be having significant dB losses.

First you should own a termlab and then close the port of your box to run sealed and then play a tone sweep and see where the whole thing peaks. You can take it from there with that basic info. Some pics of your boxes would be nice. Also there were a lot of competitors posting here a while back but very few remain these days, so if you are hoping to talk to some of them, slim chances to do so on here at this time.

That is a parallel 6th you just design it as such, you layout the front chamber unmodified and divide the volume of the rear chamber in two and divide port area as well, the rear chamber ports port length need to be adjusted the same way as you adjust every time you use multiple ports in a box design. Honestly no compelling reason to go with that design, if by any chance the rear chambers are not exactly the same size, that can be the source of a lot of trouble. Simple is better every time.

The punch 400×4 is 50Wx4 @4ohm sure maybe a little more, your mids are 75W. Comes down to how do you plan to wire these. The larger question if a powerful sub stage is going to outgun your little front stage or not. It's pretty common to see these systems where you can almost only listen to bass.

For a 30Hz tuning on the above conditions it will be 30" each of two for a port displacement of 1.6 cubic feet total, port airspeed is still 36 m/s @9K pretty insane but you can barely get away with that because it's not just some PVC pipe but proper commercial designs you are going to be using. It's kind of not even funny to see a company issuing ridiculous recommendations only to be showing themselves pictures of correct designs to contradict their statements.

Why not, if you can come up with a plan B to cut your wood the box will assemble much easier and avoid possible leaks overtime.