DIY JBL 4645 Sub project

So Where I work we have 4 of these used in a large theater, I fell in love with them, so I spent the better part of the day dissecting one and getting all of the measurements from it.



Built mine based on the JBL 4645 THX certified Movie theater sub.

" 800 Watts Continuous Pink Noise, 1600 Watts Continuous Program Power Handling
Usable response to 22 Hz (-10 dB, no EQ), flat to 22 Hz (-3 dB) with External EQ
2242H SVGTM Super Vented Gap Cooled Driver- High Sensitivity- Minimal Power Compression- Highest Maximum-SPL Capability- Extremely Low 2nd and 3rd- Harmonic Distortion- Symmetrical Field Geometry SFGTM- Magnet Structure- Extended Excursion Capability
Approved by Lucasfilm, Ltd. for THX installations

Specifications:

TRANSDUCER: JBL Model 2242H 460 mm (18 in) Low Frequency Transducer
SYSTEM:
Rated Impedance: 8 ohms
Minimum Impedance: 7.2 ohms
POWER HANDLING CAPABILITY:Continuous Pink Noise: 800 wattsContinuous Program: 1600 wattsPeak Power: 3200 watts
OUTPUT CAPABILITY:
Axial Sensitivity:50 Hz to 500 Hz; 99 dB, 1W @ 1m40 Hz to 100 Hz; 97 dB, 1W @ 1m
Power Compression:At -10 dB power (80 W): 0.6 dBAt -3 dB power (400 W): 2.0 dBAt rated power (800 W): 3.3 dB
"


So one entire sheet of MDF later and a few days I have this,



~10 Cu ft. box tuned to 30Hz single 18" JBL pro sub weighs in at 131lbs.

At 1,200 Watts program thing rocks the house!

Hard to capture scale in the pic, but it is the size of my fridge minis a few feet in height.

Here is an older pic of my sound rack ( Yes I still rock the tape player )



The lower JBL UREI Amps are the ES600 model, I have one bridged running the single 18'

I used a slightly different driver, I went with the 2241h JBL Driver.



Long story short, I corner loaded it and I am in love! feeling the room shake was a surprise for the low end response of that driver rolls off around 25Hz with a EQ i was able to boost it slightly. but I feel the low end is more than enough.


Just thought I would share, I will be painting mine soon and may even put the JBL logo's on the side... and may even build another in the future...

I have it on its own EQ and active crossover, I also have (2) 15" Mid-bass cabinets mounted behind the screen

I like movies as well

I did make some changes to the cabinet while building it, I flared both ends of each port, with a nice round edge, as well as shifted the ports up away from the driver some more, I also rounded the edges of all internal bracing.
Did it help? Honestly can not tell.

"Usable response to 22 Hz (-10 dB, no EQ), flat to 22 Hz (-3 dB) with External EQ"

22Hz is low enough for what I need it for

with a slight EQ boost I was able to get a bit more low end. I will get the spectrum analyzer on the room soon to see.

Update,

Took some time and EQ'd all 10 channels today in the theater,



I used a DBx RTA-M Mic

I have some strange harmonics in the room and odd shaped hard surfaces. But I feel this is pretty good for my use.

Was able to get the Sub about as flat as I can given the EQ I have and the restraints on the driver.

What are everyone's thoughts? Ways I can improve the above room response?

So my next goal is the 'tilt' the response like below,



To give it a more 'warm' sound with a slight bass 'bump'

But I needed a flat clean slate to build from first.