The "Big Bottom Sub" Patio System

[1audiohack]

Well since it's no longer for sale I guess it has to come out of the Market Place.

Here is the patio system as first set up for kicks with Steve Schells old Big Bottom sub with a 2225 in it as the foundation. The Peavy MB1's have 2204's in them, the 2360's have 2446's on them. Man this thing is big, and it sounds that way! Just about the way I like it. I must now build one, or three more subs and set it up for stereo.

[JeffW]

Now that's a horn loaded system.

I'm guessing rain ain't a big worry on your patio, but I'm not going to miss hearing this next time!

[1audiohack]

Hey man!

Thanks for the b'day call. I'm glad you've got the BB up and running. Try running some full range signal through it. You'll find that it sings like a canary- right through the box sides- in the midrange. Thankfully it is crossed below 100Hz. where the panels are nearly still. I learned with this project that it is a good strategy to build a box to have panel resonances above the passband, where they are not excited by the signal. Only place this one gets in motion is near the mouth, where the unbraced sides get to moving. Always intended to put some cross braces there. Let's hear some Yello... Oh Yeah... and crank it!

Hi Steve;

You're welcome!

I know its not corner loaded had you had originally intended it to be and outdoors is an entirely different animal, none the less it sounds pretty damn good. I am going to swap some drivers in it (hopefully this weekend) and try to get a little more familiar with it's sound and at what level it is happy to play at.

If I can figure a somewhat efficient way to do it (I think I have) a 2220, and a 2227 is first in line, then a 2240 and a GTI1800.

Hey there Jeff;

Too bad we couoldn't get it all done, I am glad you at least got to the shop to say hi. When are coming again?

Good luck this week!!! Let me know how you fare.

[JeffW]

I'm 4 minutes from intake prohibition, with still 1/2 beer to go.

I'm shooting for the fall NHRA event...again.

And I leave you all my JBL stuff should this last 1/2 beer be my undoing! :-)

[1audiohack]

Right on all acounts Mike!

I finally have all my car stuff at the big shop and just last weekend got the house garage set up as the audio/wood shop. As of tonight all my audio test gear will also be at the house. It's time to get busy!

[1audiohack]

What a difference a few more inches make! I replaced the 2225 with a 2240, bridged two channels in the Rane for the MB1's and put a Techron on the sub and wow did this rig come alive. I am redrawing the sub in AutoCad to make another, or three. This thing rocks!!!

[louped garouv]

What a difference a few more inches make! I replaced the 2225 with a 2240...

was the rear chamber adjusted for the driver change?

[eso]

Here is the patio system as first set up for kicks with Steve Schells old Big Bottom sub with a 2225 in it as the foundation. The Peavy MB1's have 2204's in them, the 2360's have 2446's on them. Man this thing is big, and it sounds that way! Just about the way I like it. I must now build one, or three more subs and set it up for stereo.

Now that's funny.

I'm guessing this is running mono? or are you closely spaced stereo above the BB?

From my experience listening to that sub, you're missing some of the real loading and tone by not corner loading it.

You know, if you placed the mouth facing that wall 4' away with the mains facing into the yard you'd probably get some lower response. Not quite the same as a room corner with an 8' ceiling, but better than 1/2 space.

Have fun,

eso

[spkrman57]

Now that's a HORN!!!

Ron

[1audiohack]

Not yet. It's still at 16 CFT. I need to measure the impedance and start tweaking it.

[coruphius]

only thing i could come up with is............................ WW!!!!!!!!!!!!!

that rig is amazing!!! love to hear this thing go!!

[jcrobso]

Thanks for picture!!!!!
Did you by any chance measure the lighten of the horn? My guess is 15' for each pathway.

[eso]

Thanks for picture!!!!!
Did you by any chance measure the lighten of the horn? My guess is 15' for each pathway.

I believe it's actually a little over 20' inside the horn... Steve?



eso

[1audiohack]

Yup, right about 20 feet. I measured this thing extensively when I put it together so I could duplicate it if I felt the need.

eso I entertained alternate placements and put it the way you see it as it points the rest of it away from the neighbors. It would be in the house if I wasn't so pleased with the main house system already, still you never know. I'm nowhere near done with it.

[Steve Schell]

I just found this thread; nice to see that li'l ol' Big Bottom is getting so much attention after years of indignity being stored in the garage.

As I recall the path length inside the box is about twenty feet. The flare is exponential, 15 Hz. This was chosen to try and achieve decently smooth response to 20Hz., as response to the flare frequency is never quite achieved with a finite length horn. It will output fearsome and highly efficient low frequencies regardless of loading beyond the mouth; I once measured 20Hz. to 80Hz. with 108dB average sensitivity, measured at the box exit in my living room. Problem is that in a room, standing waves screw up the response to a large degree. Outdoors the way it is oriented currently it is speaking into roughly half space and might measure more smoothly than my indoor measurements.

My intention for the design was to try and achieve true 20Hz. horn loaded response without resorting to techniques like using a low Fs heavy cone woofer. This can work, but I wanted a really clean sound without the boom or hangover of a large moving mass. On recordings like pipe organ with true low frequency content, the BB sounds the closest to real that I have heard.

The design was intended to stand next to a wall, exhausting out the end toward a room corner four feet away. When designing a bass horn I like to draw the design as an equivalent square cross section, to see the shape and the way it will relate to the "shape" of the loading provided by the room boundaries. Usually a bass horn mouth will be located close to a trihedral room corner, which is equivalent to a conical (straight sided) angle of 73 degrees. In this case though, the mouth is eight feet tall, so the best calculation was for a plane wave emerging from a floor to ceiling room corner. This plots out to a parabola shape, strangely enough. The expansion is very rapid at first, slowing down steadily in percentage terms farther from the corner. I have attached my drawing for the BB flare and it's relation to the parabolic "flare" of the room. It can be seen on the graph that the first twenty feet of flare are in the box, then the room takes over. Usually with bass horns the corner loading helps, though the room expands much more rapidly than the horn would have if its flare had been maintained to a greater length. With the BB though, the room actually does a decent job of maintaining the flare expansion out to a total path length of forty feet or so. If one were to move the horn closer or farther from the corner, it can be seen that this would be equivalent to sliding the horn flare along the center axis of the graph, altering its relationship to the parabola.