6x push pull subwoofers | audiobymartin

October 2021

My Montreal house sound system construction is halted.

I'm currently working on new subwoofer enclosures that would better suit my needs and vastly outperform the one I previously had.

I've destroyed my original sealed enclosures for both my 12'' and my 18''. When I had build them, I had space constraint and wanted music so I had build them on the cheap (single 5/8'' MDF walls). I knew it was mostly temporary and didn't put efforts in proper brace for the boxes. It was kinda of a miracle that I've painted them.

New enclosures will be:

-very big sealed system (to obtain a very low Qtc and the resulting sound I prefer)

-all double wall thickness

-properly braced at relatively close interval (close interval for a subwoofer, for mid bass, spacing would be insufficient)

-made of Plywood (2 layers of 3/4'')

-on caster for practical purpose

I'm building them in push-push configuration (ideal layout as it naturally cancel most of the vibration)

-4x front subwoofers (housing 2x 18inchs) and about 660 liters each.

-2x rear subwoofers (housing 4x 12inchs) and about 370 liters each.

Rear subwoofers will be used for the cancellation of the front wave in the double bass array concept. I've calculated that 6x 12'' would suffice for the job but I've bought 8 anyway to have headroom and lower the distortion even more.

Here you can see the inner shell and the window style bracing I've installed.

Spacing between each brace is ~13" so I can just fit the 12" subwoofer between them.

More fiberglass stuffing is to be added but I wanted to show the inner of the enclosure on this picture.

Rear subwoofers in testing.

At this point, they only have a single 3/4" wall but I wanted to test them and check the room modes.

Vibration behaviour is not too bad for a single 3/4" layer of plywood. This is due to the push push configuration.

As expected, they are easy to tip, the center of gravity is high and one have to be careful when rolling them around.

Above 130Hertz, they vibrates significantly and resonnances of the panels are evident. This is OK, I will only use them below 60Hertz and once the extra layer of plywood will be glued on, it should be much more rigid.

Should this be a enclosure that would have to cover above 100Hz, more bracing and possibly extra layer of wood would have been required.

Front Subwoofer progress.

just the inner shell built and they feel like coffins.

For reference, I'm 6'3" and 220 pounds.

The enclosures are 6'2" long...

Front Subwoofer progress.

2 windows style brace added

3 sets of sticks style brace in between the window ones.

Several more stick brace will be added once the hole will be cut for fitting the dual 18" drivers.

I will add fiberglass stuffing and close those baby as is.