Codrive

I've taken a look at those before...
They have been out for a long time.
Interesting stuff, doesn't seem to be going anywhere.

As far as the motor goes, you can accomplish the same thing with a single motor.
They are trying (I believe) to accomplish the dual-gap thing... like JBL's GTi, dual motors, opposing flux phases...
Like XBL2 does with the same top plate and flux flow.
No biggie there.

The dual asymmetrical sized cones, with the hole in the front one is the more interesting aspect.
What they are trying to do, is to get more displacement - the sum total of the 10" and the 12" cone (or whatever they are)'s surface area.
I'm not sure I picture that exactly working, because all the displacement of that 10" driver in the back must be forced out that small hole where the dustcap would normally be. Some gain? Possibly.

Interesting though, for sure.
But not for those prices. $3,000 for one of those subs in a prefab enclosure with a 1000 watt RMS class D amp?

I'll just take in the pictures, and ponder the mounting depth.
What is that, a 12" diameter, 18" depth?

 

Look close at the cutaway pic...
Like I said, the 2 motors are effectively doing the same thing as a single motor.. they're trying to do the JBL-thing I believe...

So the motor moves that shaft up and down.

Notice the basket for the smaller cone portion of this sub is sealed. That's key to making this work...

The two cones are butted up together, glued together, back to back, at the joint where you'd normally expect a voice coil former to be. Instead of the former, there's that plastic ring, with arms that hold the shaft at the center of it.

So, when the shaft moves in and out, it moves both cones in and out.

Obviously, the cone on front is going to behave like a standard subwoofer, displacing air as it moves.
The rear cone is the unique part...
Now, the rear basket is sealed... so, when the cone moves forward, the only place that the air dissipated by the rear cone can go is out the hole where the two cones are joined together.

So the theory is, you end up with the displacement of both the front cone, and the rear cone.
For $3000 of course.

Seems like it might be more cost effective (and even still louder) to get two 15" subwoofers that worked in smaller enclosures, you'd still have more than enough budget for the larger amplifier that might require.

I'm not really sure of the goal, the site is pretty sparse.

 

Well, all the air displaced by the rear cone has to go somewhere... out the hole! The cone can't move without displacing air.
So, if you look at it that way, all the air displaced by the rear cone should come into play... it HAS to all come out the hole.
So, you end up with all the displacement of the outer cone (minus the area normally displacing air where the hole is ), and all the displacement of the inner cone...

So, higher SPL than the single outer cone would have been on it's own, but not twice as much...
Despite the what... 10x-20x higher price tag? :lol:

 

There is no air "between the two cones"... look at the pic

There's a little half-roll surround right at the cone-to-cone joint, so no air that is in front of the inverted rear cone can bleed around behind the back of the front cone.

If that half-roll wasn't there, then what you are saying would be true...
But because of that half roll, and because the back basket is sealed, the air displaced by the rear cone HAS to go somewhere (or the whole complex cone assembly wouldn't move at all... it would be held in one place as if by vacuum).

All the air displaced by that rear cone has to go out the hole. B)

Take a close look at the picture, and see if you can find anywhere else that the air could go.

 

Is the magnet the blue part? If so, it looks like the voice coil is completely surrounded by it, with very little venting. This means that it will get VERY hot near the magnets, which isn't good with neodymium magnets. At least I'm guessing they are neodymium magnets due to their "with Neo Symmetrical motor" comment.

Does it look like a single voice coil driver to you guys as well? All I see is one positive and one negative terminal.

Now whether it works really well or not, the cone design is interesting. You could decrease the mounting depth a little by using a flat cone in the back, but it may also increase weight too much. But for the cost already, they could have done either a very stiff progressive spider, or dual progressive spiders.

 

...Or, they could have just used a 15" cone, rather than this series-mounted 12" and 10" cone arrangement...
And as I said, I think an XBL^2 motor would have been more effective...

There are a few design anomolies that really seem contradictory...
The use of neodymium magnets... why? Trying to cut down on mounting depth? Trying to make it a lightweight driver? :lol:

The size of the hole.. as per their own descriptions, it's not large enough to flow the air displaced by the rear cone, claiming some advantage due to the resistance...
The advantage wouldn't equate to more than a slightly smaller enclosure would gain.

It's an interesting design...
Unfortunately, I think in the same way the game Mousetrap is an amusing Rube-Goldberg setup to catch a mouse
The $1M mousetrap...
This is exactly what our government would have commissioned to be built... :lol:

 

Oh good, maybe it's half price.

Are you familiar with how the JBL GTi drivers work?

I'm actually only assuming that's how it works.. it's really the only reason you could justify two motors, IMO...
I'll have to look at that diagram a bit closer, they don't mention anything about assymmetrically suspended coils or anything...

 

The diagram on the GTI is somewhat poor. But it is very similar. The difference is JBL doesn't use neodymium, and IIRC, they use only one stack of magnets. The flux flows opposite ways in the gaps, so two coils are used, each wound opposite eachother.

 

Exactly...

But it's the concept of the two separate windings, travelling through two separate gaps... that are in essence working like two independent motors... sharing to drive a common former, with the windings staggered asymmetrically so that while one winding is exiting it's gap, the other winding is entering it's, complimentary to each other.

It literally is two independent motors in the case of the CoDrive.

If it's not asymmetrical like that, I can't see the advantage of doing the dual-motor, for the codrive, given all the depth and size.

 

Maybe to increase BL?

I just noticed something. The slit that the voice coils move in (inside the blue stuff) looks to have holes drilled so air can move all the way through them. But I still don't think they will help much. I agree that it is a somewhat poor design. At least as far as I can see. I see some poor design choices, with no benifits to balance it out. I think Geo was right when he said it was contradictory.

 

Yeah, that "slit" is there so the voice coil can move!

I don't know...
I just looked at the motor again...

And it looks to ME like the voice coils are each centered in the magnetic gap (the purple is the neodymium, btw... the blue would be a highly ferrous metal, like what a typical top plate or T-yoke would be made out of).

So, if they aren't asymmetrically staggered... what is the benefit?

I just noticed... they even named the motor "symmetrical neo" motor.