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Project Flexington: 160.3db @ 37hz!! Parallel 6th order walk through, DC Neo Elite 18s, 4 DC 5.0ks, JY Lithium, 12 banks of XS Caps

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just curious, any relationship you use on port area on the rear chamber vs port area on the front chamber? i´ve found that double port area on front works better for me, for 2 12s i had a 3 4" aeros on rear chamber and a 10" aero on front chamber, worked awesome for sure

I don't really have a go to ratio, I usually start with my small chamber volume at recommend for single sub per chamber, for shared chamber (2 subs) I go between 2x recommended for one down to 1.5x recommended (better power handling and less box rise, in the mofo blow through it allowed the subs to handle more power through out the pass band without them going past xmax). Then use the rest

just curious, any relationship you use on port area on the rear chamber vs port area on the front chamber? i´ve found that double port area on front works better for me, for 2 12s i had a 3 4" aeros on rear chamber and a 10" aero on front chamber, worked awesome for sure

For my series tuned blowthrough I was really limited in options due to using the existing shell that was in the truck (14.5" high sides and 40.5" wide internal). I've found that in 6th orders, tuning frequencies and small chamber volume are the most important factors. For a single sub I use recommended volume, for 2 subs i go between 2x recommended and 1.5 (i.e. recommended for mofos was 2 cubes per sub, i used 1.5 for that build which was 3 cubes total after displacements). How big i go depends, in the mofo build i went with 1.5x because the big chamber hand no loading wall (not to be confused with the port baffle which is commonly referred to as a loading wall) and the ratio was so huge. This allowed more cone control so the subs could take 2krms throughout the passband without exceeding xmax. Basically with shared chamber setups, going 1.5x the recommended can give you better power handling and less box rise but with the downside of less enclosure gain.

For the mofo build i went with the max amount of Port area into could fit in the rear chamber without significantly modifications and as much port area in the big chamber as I could using baffle thickness as port length to get the tuning frequency I wanted. series tuned 6th you need as much port area as possible in the big chamber, so it's usually best to go with baffle thickness as port length if the port will add to the chamber displacements due to the relationship between enclosure volume, port size and length.

Remember when designing series tuned 6ths that the front chamber tuning frequency is not really a tuning frequency but the upper limit of the passband since it acts as an acoustic filter rather than a standard port. Series tuned 6ths act very similar to 4th orders in this respect so they're actually much easier to design and have more room for error than parallel tuned 6ths, which is probably why they're so much more popular than parallel tuned 6ths.

Ive had more experience with parallels and have a lot more design principles for them than I do with series tuned. I built the one series tuned 6th because I wanted to understand how they worked and after figuring them out and discovering their limitations I got bored real quick. Parallel tuned 6ths are much more complex and have a much higher potential in my opinion assuming you're not comparing them peak spl at a certain frequency with the same size limitation. A series tuned 6th will generally have a higher peak number capability compared to a parallel given the same outer dimension limitations.

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Bit of an update, my buddy brought his nice welder over and beefed up the alternator bracket for me (he's a much better welder than me and my welder is pretty much useless on anything bigger than 1/8"). I'll post a picture tomorrow. Still need to finish the mount for the tensioner though.

Here's the tensioner I decided to use. It's off anow early 2000s ford 7.3l turbo diesel and should work great for what I need. New pulleys for it are from a 2002ish silverado:


Also, the enclosure is finally starting to looking look like an enclosure!

Had to make some compromises due to rushed planning and a few measurement errors, but that's why I'm building this, so that when I ripped it out to move onto level 6 18s that I know exactly what I am working with:




Trying to get it playing for a meet on Sunday so I'm skipping some stuff like much of the bracing, round overs, tensioner and electrical, but I will pull everything apart and finish stuff next week. Pretty excited to see what she does even if it's on low power!

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Some more parts showed up.

10ft of 4/0 ofc I'll be running from the alternators to battery, this way I only need to do 1 run per alternator instead of stacking ring terminals or getting buss bars.


Some grills for the 10" woofers. Pretty impressed with the quality of them.


More double wall adhesive lined heat shrink tubing


About to go do some more work on it, hoping to mount up the subs today!

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Got 2 of the 10s installed, just need to bore out the grill brackets for the other two and I'll be set:


Cut the baffles, going to have the outer piece removable to make installation and removal easier:


Got the bracing complete for the small chamber, need a few more bolts and it will be ready to go:


Almost time to mount the subs!!


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Didn't get a ton done tonight but I got over a big hurdle, since we didn't have time to add the tensioner, I had to man handle the alternators on with the old belt so I can make it to a meet on Sunday.



Ended up using some ratchet straps and managed to get her mounted up


Going to try to get the subs and other 2 10s mounted tomorrow and start hooking shit up!

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Going on 12hrs of working on this thing. I Redid the front portions of the port so that everything is flush and so I can add a second top layer that will overlap.



Pretty much have the cab sealed up now:


Decided to wait to mount the subs till I have the back of the box braced, so that's what I'm going to go do, then screw on the back of the box and start hooking shit up finally. Gonna be a long night lol

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Awsome build. I'm taking notes on your box, I love it. Are those 10s SVC? Where will you cross them over at if you don't mind me asking?

91 C350 Centurion conversion ( Four Door One Ton Bronco)

250A Alternator (Second Alternator Coming Soon)

G65 AGM Up Front  / Two G31 AGM in Back

Pioneer 80PRS

CT Sounds AT125.2 / CT Sounds 6.5 Strato Pro component Front Stage

CT Sounds AT125.2 / Lanzar Pro 8" coax w/compression horn tweeter Rear Fill

FSD 5000D 1/2 ohm (SoundQubed 7k Coming Soon)

Two HDS315 Four Qubes Each 34hz (Two HDC3.118 and New Box Coming Soon)

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The truck is a beast, 149.8 sealed at 28hz, 148 door open at dash at 23hz lmao. Low power, bench seat, cab not sealed off fully, box not sealed, no deadener. Even with all the air leaks this thing moves a metric fuck ton of air, violent below 30hz and still plays hard up to 50hz! Absolutely cannot wait to start finishing things and see what these baby subs can do!!!

Now time for some sleep. With the exception of a few hours of breaks and an hour nap, I worked on the truck from 11am Saturday till 8pm Sunday so I could make it to a local meet. Managed to make it and it was all worth it, everyone wanted a demo. I'll post more pictures tomorrow and reply to posts.

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