[tremrej65]

but it's also much thicker than the standard flatpack

It look thicker but it is not: the flatpack is 1.5 inches sides, top, bottom, and 3/4 for the middle separator. Mine is also 1.5 inches all around, and 3/4 at the intersection of the 2 tubes.
Right now, I would say the bigger problem is the vibration in the front/back direction of the top of the cabinet. At high volume, when I put my hands on the side of each tubes, there's more vibration on the top one. This is noticeable. I imagine you get the same effect with the standard flatpack and most likely worst on the 3 woofer version. A larger base might mitigate this issue a little bit. The effect is minimized when I add 50 lbs on top of the cabinet. See picture below.
Nevertheless, the bass is super tight, super controlled. I really like it.

[Danny Richie]

Right now, I would say the bigger problem is the vibration in the front/back direction of the top of the cabinet. At high volume, when I put my hands on the side of each tubes, there's more vibration on the top one. This is noticeable. I imagine you get the same effect with the standard flatpack and most likely worst on the 3 woofer version.

The opening on the H frame variation is larger. So the pressure within the H frame is less. Then with the addition of the No Rez on the panels, there is next to zero vibration of any kind.

[robwm]

What an amazing build! Thank you for sharing!

[ketchup]

It look thicker but it is not: the flatpack is 1.5 inches sides, top, bottom, and 3/4 for the middle separator. Mine is also 1.5 inches all around, and 3/4 at the intersection of the 2 tubes.
Right now, I would say the bigger problem is the vibration in the front/back direction of the top of the cabinet. At high volume, when I put my hands on the side of each tubes, there's more vibration on the top one. This is noticeable. I imagine you get the same effect with the standard flatpack and most likely worst on the 3 woofer version. A larger base might mitigate this issue a little bit. The effect is minimized when I add 50 lbs on top of the cabinet. See picture below.
Nevertheless, the bass is super tight, super controlled. I really like it.

Are they on carpet?  If so, do they have spikes that go through the carpet to something solid beneath the carpet?  Without music playing, are you able to rock the subs by pushing forward or backward?  If you can get them coupled to the subfloor, I don't think they'll move much.

Awesome looking build, by the way! 

[dayneger]

This is really fun to see! Thanks for sharing. Great job getting the finish to work out so nicely!

A while back I was exploring a similar notion, thinking about working with concrete. I ended up learning a great deal about different kinds of concrete, which is a surprisingly cool material when you start digging in deeper, but for other reasons I decided to build a dual-opposed sonotube-based sealed servo sub instead.

i don't buy the theory that the 22% reduction in open volume was a significant factor in the vibration, especially given the symmetry of the loading, but the floor coupling and mass of the system certainly would, as @ketchup mentioned.

This is the sub I built for my living room. It's been fun watching people respond to tracks with really deep bass.

https://www.audiocircle.com/index.php?topic=190571.msg1993527#msg1993527

[tremrej65]

Cool looking sub.This is a great design. I like it.

[goggle1824]

Wow, that is REALLY nice looking.

I went over to your more detailed post at DIY Audio and wow again! What a great project and read, REALLY intriguing result. Thank you for documenting so well and sharing with us over here, that’s just really great work, kudos!

What does each one weigh? Sorry if you mentioned somewhere and I missed it, I’m just so curious about them.