Question before I cut sub legs

[jacket_fan]

I am building the cabinets for 15 inch drivers. These are downfiring and will sit on carpet. They are sealed.

Before I cut the legs, is there a definitive minimum distance above carpet the driver should be?

I had previously had 3 inch legs made out of left over MDF and it seemed OK. The finished cabinets will have cherry legs and before I cut I would like to make sure I am not too short.

Thanks,

[Gir]

I believe the normal range is between 4 and 5 inches, but I couldn't tell you a "set" value you should use.

[jacket_fan]

Is there any difference between carpet and hardwoods. Or for that matter, on a concrete slab versus a trussed floor?

[gmed]

As a general rule, the distence from the ground should be the same as from the lip of the sub to the depth of the dust cap. usually 3".

[ThomasW]

The floor construction isn't important.

With carpet the legs sink in so they should be a bit longer than those for wood or tile floor.

The absolute minimum for no resistive loading would be enough height to create a space equal to the drivers Vd.

Most people simply use ~3"-4".

Designs like those from SVS use a shorter length and a floor plate. This is intended to resistively load the driver, that increases output slightly

[jacket_fan]

I am no expert on T/S parameters, but Vd is a cubic measurement. If the height is one parameter, what would the other two be?

In winISD I get the Vd to be 148.2 cubic inches for a Tumult.

I really am not sure where to go with this...

The plan is to have 2 1/2 in wide legs and if they get longer than 3 inches below the bottom of the box, I think they will look to "dainty".

[Inu_Yasha]

3" won't look too dainty, if I have time today I'll take a pic of my downfiring sub that has 3" and it looks great IMO with 3".

[jacket_fan]

Thanks...

[ThomasW]

but Vd is a cubic measurement. If the height is one parameter, what would the other two be?

If it's a tubesub it's the area created by the circumference of the tube, otherwise it's the dimensions that comprise the cross-section of the box, depth*width.

[jacket_fan]

The cross section is 22*22. That equals 484 sq in. But that is greater than the Vd from unibox. Perhaps I input the wrong data into unibox and got the wrong Vd.

I attached a pic to show the status of the two boxes.

[collo]

The shaded area should be equal or greater than Vd.

In your case 22 * 4 * clearance >= Vd

[Brian Bunge]

I had a Tumult in an 18" cube with 22" long legs, which raised the bottom of the box 4" off the floor. It worked very well.

[jacket_fan]

148.2/22*4=1.68

Looks like anything over 3 inches is acceptable.

Just trying to follow the rule of thumb of measure twice, cut once.

Thanks for the input guys.

Brian, these will have a cherry veneer, with cherry trim. The veneer went on fairly well using contact cement and a j-roller. I am having a devil of a time with the finish. I had used a method right out of Fine Woodworking using sanding sealer/dye/washcoat/stain on some stands I made for aome Maggies, but this veneer is not taking the same process as well. Is there anything you do different for veneer as you do for 3/4 in hardwood? I was actually pleased with a wood working project for a change. The grain really had depth and is attractive.