Have a client with an existing system which contains a sub that has a 12" forward facing woofer and a downward facing passive radiator.

He's considering installing it in a cabinet. I've alway subscribed to the theory that a cabinet mounted sub should be forward facing. Instead of mounting this thing in its traditional fashion, what do you think of putting it on it's side so both woofers are facing out in an inverted V? A flat cloth grill would be built in the cabinetry so it would look normal. It'll be about 2-3ft out of a corner. There will be some reflection in the cabinet but not like with the passive radiator facing down.

I think it would be enough to prevent vibrating the crap out of the cabinet.

Your thoughts?

Thanks.

Craig.

I don't think orientation matters in that scenario. I'd just run it like it's designed.

Odd. If you didn't think orientation would matter, then you wouldn't find a need to recommend running it like it's designed.

Also, a downward-facing passive is built to radiate out every side. If you orient it otherwise, it shouldn't perform as designed.

A passive radiator is a variation of a port with passive speaker cone mass loading rather than air. For the wavelengths of interest, direction doesn't matter much -- as long as the port and driver have air coupling. (In a crude analogy, think of the air between the port and the driver as having a certain "impedance". One would want to maintain an approximation of this impedance in the cabinet environment.)  It would not be a great idea to duct the port into another room. As such I like the "V" orientation because it results in reasonable coupling between the port and the driver. It would not be a great idea to have the chamber be only slightly larger than the speaker enclosure -- preventing the coupling.

I assume that you'll have the aid of auto room tuning to smooth out some of the kinks in this arrangement.

An approach for a too small cabinet might be a bottomless shelf vented to the room with a cutout in the kick panel under the cabinet grill.

Do make sure that this cabinet is solid or you'll have nasty buzzes. A good technique for testing the cabinet is to impulse it (hit it with a mallet) and listen for replies. After the impulse, a solid object will reply with its natural resonate frequency. I'm notorious for "thumping" walls and windows during construction. If there is a significant reply, the contractor and I will have a discussion. I warn the contractors about this drill in advance. In some cases they were not paying attention and we had to drill some holes and insert some foam in order to subdue the reply. (metal studs are the worst)

You mean, standing on its feet???

Thanks guys for joining in the discussion.

I had thought about the bottomless cabinet. Or putting the sub on these to de-couple it.

[Link: svsound.com]

I'll need feet anyway if I'm putting it on it's side

At any rate I will be sure to tell the cabinet maker to make
It rock solid.

Well, yes, but also not in whatever an inverted V would be. I'm guessing that means "with the edge of the cabinet between the woofer side and the passive side vertical and pointing into the room." Craig can clarify that.

My comment about your response is this: If you don't think orientation matters, doesn't your choice of the recommended orientation imply that you think that's better than some other orientation?

Once again, too, we're trying to help but we don't have the benefit of knowing the brand and model number so we can look at the manual ourselves.

Exactly what I was thinking. I've never heard an issue when I've seen it done nicely this way.

Most cabinet makers use a 1/4" back. Tell him to make the whole cabinet....
all of it out of 3/4"

Told an asshole cabinet maker to build it this way and he only did the sub cabinet.

The rest of it rattled like a sumbitch.

Client made him rebuild at his cost after looking at my provided drawing, with warnings in red pen to make the whole back out of 3/4".

The orientation I was suggesting was lying on its side, and turned 45 deg so that when looking at it head on its like looking at the bow of a ship. Sub at a 45 deg angle towards one side of the room. Passive radiator 90 deg to that, facing at a 45 deg angle to the other side of the room.

It this case its the design that's relivent. Not the model number as it's a question about the orientation of this particular design.

The bottomless cabinet is a good idea. As I the 3/4". Thank you.

The model number might matter because the manual might tell you that the sub, if oriented with the passive facing down, would have to be, say, four inches from any adjacent walls. That defines some aspects of how you could position it and still have it placed "per the manual." Of course, it might work in other positions, but all of this eventually comes down to whether it works once you've done it!

Fair enough Ernie. Good point. It's a Sunfire SDS12 and the manual says nothing about placement except that they recommend a corner, and to try at least two to see which sounds better.

I would say this qualifies as corner mounting. It will be in 4 corners at the same time! Hahahaha. Ugh.

Maybe I'll build a 3/4" MDF cubby and see how it sounds stuffed in that.

Thanks again for the input everyone.