MBM subs
There's a thing in DIY audio circles called a nearfield Mid-Bass Module that is designed to increase the tactile sensation of certain bass frequencies. And as you know, I'm kind of into getting mid-bass just right
I also happen to have a bit of a null around 60Hz at the main listening position (MLP), and even the dual-sub config could not fix that. Sooo, I figured I'd explore the concept of a nearfield Mid-Bass module that would cover the 45Hz to 140Hz range and be placed just behind the MLP.
Several
threads on MBM's have discussed how to do this with commercial products, but this is me, and I DIY. And because I had a brand new pair of 12" HiVi M12 woofers from the period I thought my Peerless woofers were toast, all I needed was an enclosure and an amp. I found a perfect enclosure on Parts Express, a vented box designed for automotive sub applications, so nice and cheap and wrapped in black carpeting that makes them disappear behind the seats. The vent tune is actually pretty high at around 45Hz, but that's perfect for an MBM.
To power these, I got a QSC GX5, which is a 500wpc class H (similar to the Sunfire) amp. The DriveRack 4800 does the high-pass crossover (4th order at 45Hz) and some EQ.
So now that I had the MBMs built, I played around with one of them for a few weeks. Placed inches from the back of my Ekorness recliner at the MLP, it does indeed fix that null. And the vented nature of the enclosure does indeed generate high particle velocity that flaps the pants and gives a 'chest thump' during movie explosions and in some bass-heavy music, like Deadmau5. At first, I had it running a bit hot, as the effect was novel, but soon, the over-boosted bass got tiresome, and I dropped the level by 3dB, and now the MBM blends very well with the other two subs. Still need to attach and EQ the second MBM behind the spouse's seat, but that will be for the future.
I will say this; if you have a lack of bass or mid-bass due to placement constraints and room issues, an MBM is a pretty simple way to get back some incredible 'slam'.
In my room, I've had amazing low-bass performance thanks to the IB, and with the second Sub, even smoother low-end, but that null at 60Hz and some other dips in the 80's were room induced and hard to fix without yet a third or fourth sub being added along the side walls. But the MBMs cleared that up, and on top, gave a much more tactile feel. I now run the entire rig at a lower overall level, as I get the sensation of strong bass without having to crank the system as much.
I also started a dedicated thread on the MBMs here:
MBM Deployment
Here's a pic of the assembled MBM sitting on the floor before being placed behind the MLP.