Finished subwoofer idea.... what do you think?

[Audiophilenoob]

After Tom Danley's suggestion in the other thread this is what I've come up with for the final DC motor driven design

that's a 24x30" cone... each opening is 25x30" and is 60degrees from the center line of the curve

it allows for 30" of one way movement in each direction and is dipole... designed to be optimal in such an exclosure

2HP servo motor... with 300vdc and 5A.... (already bought this)

cone will be carbon fiber over foam (needs internal dampening) shooting for 1/8" thick carbon fiber epoxy resined

BB6 says 4800cm2 of cone area moving 5" one way (the suspension will allow for 22" one way) yields 133db at 10hz.... at least with a 1500 gram cone weight

if I can get a stable 10+ inches you're looking at around 137db at 12hz or so in dipole...

I'm only looking for this to play to about 35hz or less...

any suggestions?

[Audiophilenoob]

another view

[Audiophilenoob]

back view

[mike.e]

So its the same sort of drive system as contrabass but DIY?

http://wanderkolonie.org/servo2.htm

[Audiophilenoob]

Originally posted by mike.e
So its the same sort of drive system as contrabass but DIY?

http://wanderkolonie.org/servo2.htm

kind of... it's a different method driving the cone though

there's no rotation to linear converter and it's not a normal subwoofer.

it literally swings that piece of kevlar/carbon fiber and foam to produce very very low bass at very very high SPL's

[johninCR]

Am I looking at it correctly, the green thing is your cone which will sweep back and forth?

[Audiophilenoob]

Originally posted by johninCR
Am I looking at it correctly, the green thing is your cone which will sweep back and forth?

yes

[johninCR]

In that case,

1. Dipole will have a whopping SPL of 0db . + & - waves of the same magnitude travelling the same distance net to zero. The front of your speaker would be your dipole null. One side of your contraption needs to be in a box or separated in some fashion, and not just a divider with them both still facing the front.

2. Your cone will be traveling very different speeds depending how far the point on the cone is from the axis. I think this will cause significant doppler distortion.

3. If your motor will work like you think, wouldn't it be less problematic to drive your cone in a pistonic motion?

[Construct]

Originally posted by johninCR
2. Your cone will be traveling very different speeds depending how far the point on the cone is from the axis. I think this will cause significant doppler distortion.

Additionally, it sounds to me (although I may have misunderstood) that your SPL calculations were done with pistonic travel in mind. In your case, however, one edge of your 'cone' is stationary. As such, the swept volume of a given displacement of one edge of your 'cone' will be half that of a 'cone' that is not stationary at one edge.

[Audiophilenoob]

Originally posted by johninCR
In that case,

1. Dipole will have a whopping SPL of 0db . + & - waves of the same magnitude travelling the same distance net to zero. The front of your speaker would be your dipole null. One side of your contraption needs to be in a box or separated in some fashion, and not just a divider with them both still facing the front.

2. Your cone will be traveling very different speeds depending how far the point on the cone is from the axis. I think this will cause significant doppler distortion.

3. If your motor will work like you think, wouldn't it be less problematic to drive your cone in a pistonic motion?

this is the problem with the CAD ... it wasn't exactly clear... there will be a type of compression panel aiming the backwave 180 degrees from the front wave... I just included the musical element itself

2. this is the same method the PG cyclone uses for servo's... so I'm not sure if this was an issue for them...

3. I can and may in fact do a simple down firing element... problem is coming up with a workable rotation to linear converter with only one "pumping" action vs. the dual action Tom's design for the contrabass... there's the very distinct problem getting the moving mass low enough this way