Quad driver push-pull question

[Trackzilla]

I'm working up my latest tapped horn sub design, and am planning to use 4 Lab12C drivers. I want them to operate in a push-pull arrangement, as well as having opposing pairs cancel mechanical vibration, so I came up with the configuration I'm showing in this rough paint drawing (not at the real computer currently, so no real drawing I'll post yet)

I find myself wondering if there is a critical distance that I need to remain above for space between the magnets on drivers #3 & #4 (the red line)? I'm envisioning some sort of interaction between their magnetic fields that might be problematic, but real world advice as to whether I'm imagining things or if it's an issue known to those with better brains & more experience would be appreciated.

Advice anyone?

 

[BP1Fanatic]

I'd say at least an inch so the pole pieces can breathe.

 

[tb46]

Hi Trackzilla,

Mirror (turn around 180°) 1/3 or 2/4?

Regards,

 

[ßart West-VL.]

What is the frequency range you want to use this?

Subscribed! 😀

 

[JLH]

I would mount them like this:

An externally hosted image should be here but it was not working when we last tested it.

This way the heat from the pole will not effect the other woofer. Mounting the woofers with their magnets butted together could cause them to over heat before the other two woofers.

 

[tb46]

Hi JLH,

Your picture is so much better than my attempt to verbalize. 🙂

Regards,

 

[weltersys]

This way the heat from the pole will not effect the other woofer. Mounting the woofers with their magnets butted together could cause them to over heat before the other two woofers.

Your and TB46 suggestion is definitely the way to go, in regards to symmetrical loading, the heat issue and the plenum volume can be reduced by half (or more).

A plenum as large as required in the OP would be a big waste of space, it would need to be around 14 inches across to leave some cooling room.

 

[Trackzilla]

thanks guys, I guess the unilateral opinion is cooling is likely to be more of a problem than magnetic field interaction & I should solve both by inverting a pair of drivers. I was looking to place the drivers so that mechanical cabinet vibration would cancel completely, but I may be splitting invisible hairs.

This is for subwoofer applications. Specifically targeting 20-100Hz range. Planning on putting 3 units in, 4 drivers each. 2 imbedded in the walls, one under the stage. We're attempting to wean them off of the need to continue to rent 4 CV T36-750 & 2 QSC PL236 to augment their existing rig once a week when they have big name EDM DJs roll through. They will have 3 channels of an FP10000Q to drive them. We're also planning to outfit each cab with one of those nifty new D-Fend units from eminence as a touch of additional bulletproofing.

I'm still playing with folding on these boxes in an attempt to come up with a way to make them schnook politely into some odd spaces in the wall configuration. If I can shoehorn them in there it'll have the dual bonus of corner loading two horns and opening up floorspace that is currently occupied by the rental units.

 

[ßart West-VL.]

... I was looking to place the drivers so that mechanical cabinet vibration would cancel completely, but I may be splitting invisible hairs. ...

You still get the cancellation when the drivers are configured as in JLH's drawing. I don't think you can ever get rid of it completely, so don't worry about the asymmetric placement, you wouldn't be able to tell the difference.

 

[Trackzilla]

yeah, I realize it still effectively cancels in the other configuration. It's probably a symptom of insanity that makes me drift towards exact symmetry. I cant help but envision the minuscule residual forces caused by the angular differences in complementary motor alignments, although they do also cancel, they exist before they cancel...and even smaller amounts of those forces will actually be transferred into the rest of the cabinet by virtue of it not being symmetrical to that pair of motors. I know it is infinitismal relative to the rest of the energy in question, but there it is anyway. So I have to continually poke myself to ignore the fact that they aren't in perfect physical alignment.

As I said, insanity 😀

 

[Shadydave]

Trackzilla,
You need to wire the drivers so that they "move as a complimentary pair" or as one moves in the other one nested in it moves out.
The nested cones are still in anti-phase.
You still have the same cancellation as the speakers need to move the same way they did before.
It is just that one is "backwards" now compared to the way it was before.
Or,
maybe you understand that and your symptom is wanting complete symmetry in your life.

PPSL

Dave

 

[Zero D]

Kef introduced a range of speakers in the early 80's, with amongst other things, a Force Cancelling Bar. It works 😉

Of course i don't expect anyone to do it like that, but it "could" be done other ways 🙂

 

[Trackzilla]

Trackzilla,
You need to wire the drivers so that they "move as a complimentary pair" or as one moves in the other one nested in it moves out.
The nested cones are still in anti-phase.
You still have the same cancellation as the speakers need to move the same way they did before.
It is just that one is "backwards" now compared to the way it was before.
Or,
maybe you understand that and your symptom is wanting complete symmetry in your life.

PPSL

Dave

Yeah, the latter, a wee little symptom of my OCD surfacing lol

 

[ßart West-VL.]

I like symmetry too, but in this case the drivers themselves will be four different ones, small differences in the T&S parameters.
So don't worry about it.
And if that is the worst symptom of your insanity, no worries, it's not dangerous. 😉