Anything worth doing is worth doing to excess

After poking about and stumbling on the Cult of the Infinitely Baffled, messing about with modelling programs like Unibox I have discovered a nice little feature in my home.

I have a natural large subwoofer box which was created when the room over the garage was constructed. Basically a 7500 liter subwoofer cabinet.

Now the IB folks steered me towards the right kind of stuff to generate serious bassness. And here is what I have discovered. Two Ficaraudio Q18 woofers and a Behringer EP2500 amp will provide prodigious amounts of bass. In doing some modelling of both that 7500 liter space and another potential space of 32000 liters, I decided why not put a port into the easily sealed space just to see what might happen. Well, two Q18s in a 7500 liter box tuned to 11.1 hz (the lowest that Unibox will let me tune it, even though I can see a tune just below10 would completely smooth out the curve. Gives me well over 120 dB all the way up and down pumping 400 to 500 watts into each speaker. The same 120 dB when the space is treated as sealed above 25 hz with the standard sealed box rolloff below that. Of course that can easily be picked up with some EQ and room gain. Changing the volume to 32000 liters makes no difference at all for the sealed case. The 32000 could not be sealed off sufficiently to make an even larger tuned box.

So my plan is to build the subwoofer with a port(s) which can be sealed or opened at will. I will have my IB and EBS just like that. This sub will be used up to 40 or 60 hz max depending on matching with the main speakers or most likely by the use of midwoofers.

Two DSP units one for IB and one for EBS would make the job of switching over extremely easy.

How crazy does this sound?

Thomas,

Adding the port is a bonus and won't add more than an hour or two to the project. IB is just a matter of clamping the lid is on the port, and switching in the IB tuned DSP. I believe that using a midi cable the DSP can be reset with any EQ "curve" I save on my 'puter. So the one DSP would serve for comparison and a second might be added if I really find I wish to switch back and forth.

I think I have attached the Unibox Plots. Both with 7500 liters, the vented tuned to 11 hz

Power is 400 watts per driver

http://www.digphoto.net/Subwoofer/CBResponseQ18.gif

http://www.digphoto.net/Subwoofer/VBResponseQ18.gif

Try again fixed 'em. Not used to posting pics or links here.

I know the XMax is reached before 11hz with that model. Sealed runs into XMax problems at 11 hz too.

Unibox has some sort of runtime error below 11 hz tuning. I believe a lower tune would move that maximum excursion lower. It does knock a few dB off too. But nothing like the rolloff with sealed.

Thomas has made some very good suggestions to me steering me toward bass producing components and the wherewithal to utilize those components to good advantage. And an IB is about a simple as it gets with regards to slapping a couple of drivers in a wall or a box. No need to seal the cavity, no messing about with tuning the port. All good things.

Steve is chiming in on the possibilities available when you have a lot of volume for a "box". And I am familiar with the attendant need for more fiddling about.

The shape of the space has even gotten me to thinking about a 10 hz transmission line. The space is a bit over 26 feet behind the mounting wall.

I come from an era when a 30 inch woofer was available in the Patrician line, and I heard a set at a friends home. He had to sell those wonderful speakers when he broke some of his wife's precious china.

Discount??? Oh boy I am in real trouble now. I guess I better get busy.

If I build something that puts significant strain on the structure of the room, there will be an even larger strain on the structure of domestic tranquility.

I am not trying to get to any specific hz or SPL number. I just want to have clean solid bass below 20 hz. And I think that two SSD or Q 18 inch woofers will serve me fine in my home. I would build in an ability to add two additional drivers later. Like after the divorce.

Oh yeah, I can just see that big ole box sitting in the driveway when UPS delivers, with HEMP Acoustics on the side. What them boys been smokin'? Hempmatrix cones, stems and seeds?

I think I have this down pat now.

I have some ceiling work to do from a little AC air handler water damage. And I have to run some HDMI cables to the spare bedroom since cablelabs is holding up MRV on TiVo Series 3 units. Along with rerouting some speaker wiring.

Attic job part of that includes strategic hole poking maneuver after some ruler work..

Lovely wife already complaining about too many boxy looking speakers for HT.

Do a sales job on removing two big ugly black boxes.

Make a mockup woofer holder for the open doorway and try existing woofers in it as a psuedo IB. Just for grins. A couple screws and some duct tape should suffice for a brief test. If it works out, temporarily install present drivers in accidentally prepunched ceiling holes, which are just waiting to be filled with some 18's. (Excuse to keep heat trapped in family room.)

Keep checking email for quotes from Ficaraudio

Find an amp with serious wattage at low impedance and low cost. Probably a futile quest.

Figure out a nice way to camoflage the IB with white. I have a great 12" by 24" grille, but it is way too small for venting four 18 inch woofers.

Go to Home Depot and gather up some flat stuff with which to make structures.

However, I will not succumb to any HEMP.