Auralex Subdude vs. Sand-filled riser?

Whoa! I didn't know such a product existed! Thanks for asking! I'm now curious to know as well...

Matt, I hope you don't mind me expanding on your question, via your thread:
I have a concrete slab basement floor, with thick carpet and pad. My sub sits on this carpet. Let's say I can't do a sand-filled stage, but I would be willing to build a 2'x2'x8" sand-filled carpeted platform and sit my sub on it (and sit the platform on my carpeted floor). Would that 2'x2'x8" sand-filled platform make any improvement in bass performance? Would it need to be bigger than 2'x2'x8"? Would this Auralex Subdude product perform just as well?

ND

Hmmm... reviewed here by AVS member Kal Rubinson.

And here's a thread dedicated to the subdude:

http://www.avsforum.com/avs-vb/showthread.php?t=644330

Here are the mechanics ...
Remember two things: Every action has an equal but opposite reaction and F=MA.
When the driver moves forward, the cabinet wants to move backward. A sub needs to be well anchored to something of considerably more mass than the sub in order for it to perform properly. Obviously a concrete slab has more mass. On the other hand, the sub is now mechanically coupled to the slab which is mechanically coupled to the house. Somewhere in your house, you'll have a second subwoofer ... a wall, floor, ceiling ... a few houses ago, it was a wall in my son's bedroom.

If you're building a stage, don't let any part of the stage contact a wall (1/4" separation works fine). Ideally, you'd have the stage framing on Acoutik Mat; but, if you don't, that's OK. When you fill the stage with PLAY sand, your stage now has considerably more mass than the subwoofer. The sand is a damping agent, absorbing the kinetic energy in the stage and converting it to heat. You've now eliminated or signifcantly reduced the energy transfer into your home's structure. Since a nice sized stage with sand has soooo much more mass than your sub, most of the energy the sub is producing ends up as acoustic energy in your room.

Not recommended for upper floors ... need a conversation with a structural engineer first.

So Dennis - should our answer to the cheaper than GG questions that continually pop up be fill your walls with sand?

Great post BTW - really explains the benefit of the stage.

What if a full blown stage is not possible in the area the sub is going? Its often recomended that additional subs are placed behind or to the side where a stage is out of the question.

So should these be placed directly on the floor with carper/pad under them?

If a smaller platform is possible is there any recommendations on how much Mass is required for it to be effective (e.g. weight of platform is 2 x weight of sub)?

Cheers,
Mark

I've played my bass (amp) on both setups. Auralex does not come close to a sand filled stage.

That's my next question as well.

But would a sand filled stage (roughly 12' x 4') be too much weight for a dricore subfloor? That's something I'm debating right now. I want to dricore my entire room first and then build the state/riser on top of it. However I'm concerned about the weight of a sand-fill stage on the subfloor.

Something like this Subdude might be a better option in that case. Then again, does the entire stage need to be filled or just where the subwoofer would be place

Note: The sections that are sand-filled are separate than the insulation filled sections. Also, each section doesn't touch the others, or the walls.



Dan

I have seen DE say he isn't sure that would be a good idea. After seeing that comment I went to the dricore website, and saw that the panels can support a tremendous amount of weight. I remember googling the mass of sand, and calculating it shouldn't be a problem. I was going to re-do that math again when it came time to build mine.

I happen to use a subdude on top of my stage, seems to work very very well.

I did pretty much what DKAPS did - but DE said was waste of time as not enough mass



So I'm wondering at what constitutes enough mass.

Cheers,
Mark

If you ever decide to change your subs location, you'd be limited to where the sand is under the stage.

Apples and oranges.

If I had my sub sitting on granite bedrock I wouldn't need a Subdude. But they are sitting on floor-over-joist and as Dennis says bass will be transmitted through the structure. How well it's transmitted depends on the structure and even the proverbial sand-filled riser will transmit energy. The Subdude damps the energy transmitted to the structure so there's less to transmit through it.

The Subdude works a treat! Besides, they're so cheap that doing both the 'dude and the riser is quite practicable.

Thats why I wired and filled both corners.

Not enough mass and not enough damping. There's very little, if any, difference if you place your sub in the right or left corner. You'll find smoother bass response by getting your sub out of the corner.

Matt,

Having those small amounts of fiberglass near the sub won't do anything for any "boominess" at your listening positions. The wavelengths you're dealing with are way too long to be affected at all by 2" or 7" of absorption. It may help reducing any audible port noise or other things like that coming from the sub though. If you must do front corners, you could do one in each front corner, and then using the "virtual sub method", you can adjust their ouput levels so the virtual sub is at another point along the front wall. This won't help you with any length modes, but you'd be in better control of your room's width modes.

Dan

With a single sub in a corner, the low freq. response will most often vary greatly from seat to seat. Sure, you could equalize for your money seat to flatten it out but chances are, you'd make another seat worse than it was before EQing. I found out this cold fact in my own room. When I first added PEQ to smooth the "best seat", it made others absolutely uncomfortable.

Your subwoofer/s should be placed to provide the most similar response to all of your seats - not always the flatest, but the most similar among them. This way, when you add your PEQ, every seat benefits.

The benefit of using more than one sub, other than increasing headroom, is that you can place a "virtual sub" in a location where you wouldn't/couldn't physically place one. When using two subs, they behave very much like a single sub located between the two.

Depending on your seating locations, and the width of your room, there will be a best location for a sub to be in regards to left and right to make more than just one seat in a row for example, the most similar in response.

With a sub in each front corner, using their individual volume levels you can shift the location of the virtual sub left and right to the best spot in relation to your room's width modes. If your design confines them to the front wall though, your still stuck with length mode issues to deal with.

Dan

McCall, Is your stage filled with insulation or with sand?
I have an insulation filled stage and insulation filled riser and there is noticable energy transfer of the sub on the rear riser. So, I will be picking up a Gramma, but I was curious as to your starting point.

Did you notice immediate improvement? Is your sub front firing or downward firing?
Thanks
Mark