DOS subwoofer with 4x 6.5" woofers

[ppataki]

I am posting this on behalf and with the permission of one of my friends who has built this project

Concept:
Dual opposed subwoofer (DOS) using 4 pieces of 6.5" Tang Band W6-1139SIF subwoofers, 2 in the front, 2 in the rear
Closed cabinet with the below properties:

Made with 22mm thick baltic birch plywood using CTK Dominator and CTK Premium vibration damping layers and polyesther wool + some additional bracing
The subs are driven by a Crown CT4150 4-channel amp (each driver has its own channel)

Here are some pictures about the build:

As expected from this concept, the cabinet is rocksteady even when pushed hard, there is virtually zero cabinet vibration

Measurements will follow soon!

 

[digitalfrost]

That is quite a low Qtc, but hey the enclosure is not huge so why not. I see that you have a dedicated speakon plug for each chassis? I'm wondering if you have dedicated amplification anyway, why not build two stereo subs?

How does your amplification look like? I would've put two chassis in series to get to 8ohms and then paralleld the pair if using a standard subwoofer module.

I did a similar thing with the W5-1138SMF, see here https://audiosciencereview.com/forum/index.php?threads/mini-micro-subwoofer-thread.22870/post-762094

The subs are on my desk and nothing rattles.

 

[ppataki]

The subs are driven by a Crown CT4150 4-channel amp (each driver has its own channel)

Each driver has its own channel from the Crown so no need to play with the wiring

That is quite a low Qtc

Indeed, that was the plan

why not build two stereo subs?

there was no room in my friend's home cinema room for two cabinets so I have designed one cabinet for him with 4 drivers so enough air can be moved

 

[Wolf]

Boost/PEQ employed? I would think a bit at 40Hz would help.

 

[ppataki]

Dirac Live 3 is used, will post measurements with/without it hopefully tomorrow

 

[ppataki]

Now the measurements!
(at listening position)

FR

The highlighted curve is with Dirac, the other one is without Dirac
It starts dropping at around 16Hz - I must say this is pretty impressive!
Dirac only needs to compensate 5-7dB below 40Hz
Room gain is around 15dB so that helps tremendously too

All the following measurements correspond to the Dirac-corrected curves

Distortion

Waterfall

The room is not treated

Wavelet

There is about 22ms delay starting from 160Hz

My friend commented subjectively that this subwoofer supercedes all of his previous ones, it is super precise, fast and yet rumbling when needed (his bed is literally moving....)

I think overall these are pretty impressive results especially given the price range of these drivers...

 

[abdo123]

Distortion is suspiciously highly for 75 dB. Edit: it's probably the noise floor.