Sonic Couch Driver

In the beginning the world of acoustic fidelity was flat and without extended bass extension. The heavenly deities of audio were sad and searched the world for a hero to bring bass to the sonic deprived masses, but they could find none. Then after all hope was exhausted a great disturbance in the universal force was felt. It could mean only one thing...

Martin was back in town and he had stopped in to see me.

This is the journey of two men, eight drivers, several hundred pounds of reclaimed lumber, drywall screws, and a cat.



On the afternoon of July 24rth, 2004 I received a telephone call from my friend Martin. He wonders if he can drop by and pick up a vacuum tube. Although this is the reason for the visit, we both know that its only an excuse to spend several hours discussing turbo chargers, robotics, and of course exotic audio. I was not be disappointed, and much discussion occurred concerning multi-driver line sources. I lamented the fact that I really had no where to actually set up such monoliths of acoustic splendor.

Its no secret that my sound system is lacking in low end response. Which isn't a big deal since I don't listen to a lot of music with a real deep bass beat, but it would be nice to have a fuller sounding cannon fire when I toss the 1812 overture onto the turntable. Now we originally had an insane idea to build a Sonic Bass Bed, out of an array of about a gazillion inexpensive 6x9 surplus auto speakers. Since I never got around to building the bed, the Sonic Bass Bed was never built, but I did have 4 pairs of brand spanking new 6x9's. The outcome was obvious (if only to us). The epic adventure was to begin the next morning. Which in Martin speak means the next afternoon.

ENTER THE SONIC COUCH

Well my couch was designed by people with legs 4" long, so it could stand to be raised up. We scaled back the original design and ended up with a 'sub' approx 7' by a bit less than 4'. Instead of being open on both sides as orginally called for, the back was turned into a giant port. (Or a huge air pump, wind tunnel whatever...) The drivers are arranged in 4 pairs. The operation is described as we go.

In the beginning

Martin finally realizes the scale of this venture...


Mockup

Martin poses for a quick pic, as we do a quick mock up.

Let there be holes

I cut lawn, Martin cuts holes...

Chamber

One complete segment. The drivers are driven out of phase so that when one driver is pushing the other is pulling. Its basically just a real high volume air compressor.

phasing

Direction of air flow with proper phasing.

Folded

All four segments in place. The front of the 'sub' is toward the floor, the top will enclose a giant port which will be located toward the wall.

Martin with childern

Its about 8:30, and Martin is in deep kaka, since he should have headed home about 2hrs ago. We agree to meet up again in two weeks and Martin departs leaving we with a half finished giant, and no room left to sleep.

more segments

After Martin departs, I struggle on and hook up the wiring harness (Twice). The first attempt resulted in nearly zero output. How can you have 8 drivers, and no output?! .Although the phasing was perfect, the impedance was not... Hmm 2 ohms, that ain't right. Seems they are 4 ohm speakers not the 8 I designed for... Yeah... I knew that. Seems I remember telling the class that a 2 ohm load impedance was bad, when the amp thinks its driving 4... Proof of concept.

front

side

All righty then... Phasing? Check. Impedance? 8 ohms, Check. Bleeding ear drums? Check. --sorry what was that?

sitting on side

Top and bottom in place, looking at it from the front. My God Martin... What have we done...

cat in box

Well if all else fails Marbles the cat can use it as a play house.

in positon

On the floor, and in position.

gaping port

Theres that giant port in the back. You could dock your ship in that thing.

couch in place

Well here it is with the couch in place. Its just a bit high now, although its just about the perfect height to use with my laptop now.

Pleminary testing seems to show that the low frequency cutoff is... Huh... It should be here some where... It makes one heck of an air pump at 1-2Hz. We'll be sure to do complete testing when I get back from vacation.

There is significant flex, and vibration in the port, and will require further structural reinforcement. Of course there is significant vibration and flex of the house as well...

The design is such that it can be 'sub-graded' with an additional 16 drivers, bringing the total for the finished project to 24 drivers.

Does it work?
Yes...
Can it reproduce bass...?
Check the seismology reports for the morning of July 26th, and you will have your answer.

Impulse testing, and specifications to follow in 2-3 weeks time.