Bob, I have to admit that I haven't done the calculations on any of the suggestions John and others have posted.  I have full faith that if John says the box is tuned at 19 hz, then it is.  If you chose the right length of port, it should perform as described.

But just if you want to be sure, plug the driver's specs into WINISD (it even allows isobaric loading as an option) and model the suggested box.  Then go to the next tabs and change the box size and port length to your box size and port length.  What you see in WINISD is what you should hear in your room, but with a bit of room enforcement on the low end, and even more for corner placement.

Keep fiddling with WINISD until the curve looks like what you want to hear, it's fun and free.

Try playing with flared ports too, it's good for you.

The bottom 2 chambers of Bob's box nets to about 155L (net of driver and port).  With the 13.5" long 4" port the tuning is just above 19hz, but with that corner placement he's getting an effective length of over 15".  With the isobarik loading, the drivers are acting the same as a single driver in a 310L box.  It's closer to an EBS type alignment but with a small box.  Even though he could lower the tuning, the port would turn into a problem because it would get so long.

So no Bob's box isn't flat to 19hz, but the few db sacrifice for the added shelf of extension is offset by some room gain.  In room, Bob should be pretty flat down into the upper teens even though his layout doesn't give him maximum room boost.


Bassboy,
I'm pretty sure that 95db on 1 watt at 20hz is a pipe dream (excuse the pun).  I think only a giant bass horn or multi-driver rig will do that.

The Tower of Power does 95 db.  My traditional design models at 93 in open space.  With Transflex loading, corner loading and room gain I am hoping for 95 db at 1 watt at least way down low.

I would be thrilled with that level, and I am hoping for that much volume but we'll see.

Bob, overlooking the DVC issue, the end results are not irrelevant.

The important thing when designing EBS ported is the box and port tuning.  As long as the box and port are tuned to work together, the driver is the only responsible for putting out whatever it can at the requested frequency.

The box will output whatever sound the driver presents it with at the box's tuning frequency.

The problem comes into play when you tune the box and port WAY out of the driver's range, which you haven't.  The cost in that case is sensitivity, because the driver is struggling to make sound way below it's resonance and we've all seen the FR graphs that show heavy rolloff around fs.

I strongly urge you to play with WINISD, you'll learn more there much more quickly than anyone can explain anything.  It's an excellent visual tool that you can experiment with.

Bob,

It would be nice to know once and for all which drivers you have.  Back on page one you gave us a link to these, which have 15mm of Xmax (that's almost a 6db difference at the bottom end):  http://www.partsexpress.com/pe/showdetl.cfm?&DID=7&Partnumber=295-190

Let's get on the same page before proceeding.

Bob, WINISD cannot model the HWK or 6th order bandpass but it does very well with isobaric vented, which is what you have.

I'd go through the motions but I don't post pics so it's meaningless for me to do it.

John, I don't know where we're at now in the hz department, but I think I'd take the 15hz/rumble filter idea over the +6db gain since I'd have to build two boxes twice the size of my existing one to get there.
I'll take bassboy and your suggestion first. Remove some wires, listen to the mains then slowly add wires/equipment and gentle tweek along the way.

After I do that, I think I'll play with room treatments.
This is cheap/easy, don't laugh if it's a dumbass idea.
Take all of the cushions from the sofa's / loveseat's from upstairs furniture and line my walls with the cushions.

I've got to think that the room is playing into this. Despite how much time/effort I put into the room (with acustics in mind) that it turned out good enough not to need SOME form of absortion/diffusion.

mattresses on the celing? man alive, i laugh at myself sometimes trying to move my hwk and other subs, im sure they weigh in excess of 100lbs and awkward as a dead elephant . but im sure i would collapse into a ball of hyseria trying to fix a mattrress to my celing, bet the wife would love it 2