DIY Speaker Stands PICS and advice needed

bdp24 · « **Reply #20 on:** 17 Jan 2015, 09:30 am »

Quote from: Outofthewoods on 17 Jan 2015, 07:39 am

Or make another box (MDF?) that fits within the columns and leaves 1-2" of gap on all sides. Fill the gap with sand, litter, lead shot etc..

Ruben

+1. That's how Danny's "sandbox" woofer box is constructed (for details on the sandbox see the GR Research 12" woofer listing on the website). Then install braces across the span inside the inner box, wall to wall. Beautiful speaker stands Ron!

HAL · « **Reply #21 on:** 17 Jan 2015, 02:10 pm »

Ruben,
That would be cool as well. Lots of cool ideas to try.

Have a fun time with the stands. They really do look great!

Vedder323 · « **Reply #22 on:** 19 Jan 2015, 03:18 am »

Quote from: HAL on 17 Jan 2015, 02:10 pm

Ruben,
That would be cool as well. Lots of cool ideas to try.

Have a fun time with the stands. They really do look great!

Thanks man!

@everyone,

I like Rubens idea of the mdf box in the middle and curious, would a larger PVC pipe with caps work just as well? That would be a snap to knock out?

Thanks!

Folsom · « **Reply #23 on:** 19 Jan 2015, 03:59 am »

Quote from: Outofthewoods on 17 Jan 2015, 07:39 am

Or make another box (MDF?) that fits within the columns and leaves 1-2" of gap on all sides. Fill the gap with sand, litter, lead shot etc..

Ruben

I'm trying to be an ass here because I think I'm right.

Until a higher power comes along, I'm almost certain that bracing the walls is the most important factor here, then you can do whatever you want inside. I'd dampen the walls too, though. Then weight will matter if they aren't heavy enough.

bdp24 · « **Reply #24 on:** 19 Jan 2015, 04:42 am »

A way to both brace and damp the stand's walls would be:

1- Install plywood strips (or dowels) about 3" apart across the width and depth, and 6" apart vertically. There will therefore be four braces every 6" of the stand's height; two running side-to-side, two front-to-back.
2- Install four braces running top-to-bottom, on the outside of and butted up against the horizontal braces. If you want to get really nutty, glue the braces together at every juncture (there will be four points at every brace level where the braces cross one another). This will create the ultimate form of bracing, a matrix.
3- Install plywood or MDF planks on the inside of the matrix the braces have formed, creating an inner box.
4- Fill the void between the inner box and the outer stand walls with sand.

The stand doesn't need braces 3" apart, but if you put only one in the middle, front-to-back, side-to-side, and top-to-bottom, there is no way to build an inner box to create a void for the sand. Of course, you could skip the inner box and just put in one brace left-to-right and front-to-back every 6" of the stand's height, and one top-to-bottom, and fill the entire stand with sand. Either way, the stand should be deader than a doornail!

srb · « **Reply #25 on:** 19 Jan 2015, 04:52 am »

Just use a PVC pipe with sand around it. It will brace the walls of the column, unless you've figured out a way to compress sand. Don't overthink it or overcomplicate it, it's a stand, not a speaker or a subwoofer.

Steve

bdp24 · « **Reply #26 on:** 19 Jan 2015, 04:56 am »

Quote from: srb on 19 Jan 2015, 04:52 am

Just use a PVC pipe with sand around it. It will brace the walls of the column, unless you've figured out a way to compress sand. Don't overthink it or overcomplicate it, it's a stand, not a speaker or a subwoofer.

Steve

That will damp the walls, but I don't believe it will brace them. If you don't mind the weight, a single brace both left-to-right and front-to-back every 6" in height, and the filling the entire stand with sand, would be pretty easy and cheap, and very effective.

srb · « **Reply #27 on:** 19 Jan 2015, 05:00 am »

Quote from: bdp24 on 19 Jan 2015, 04:56 am

That will damp the walls, but I don't believe it will brace them.

That's the inherent mechanical beauty of a cylinder. Given the strength of PVC drain pipe, it would likely take several thousand pounds of force to flex it.

Steve

Outofthewoods · « **Reply #28 on:** 19 Jan 2015, 05:08 am »

Quote from: Salis Audio on 19 Jan 2015, 03:59 am

I'm trying to be an ass here because I think I'm right.

Until a higher power comes along, I'm almost certain that bracing the walls is the most important factor here, then you can do whatever you want inside. I'd dampen the walls too, though. Then weight will matter if they aren't heavy enough.

The filled chamber would be enough the keep the walls from humming. What more is needed?

Ruben

bdp24 · « **Reply #29 on:** 19 Jan 2015, 05:11 am »

Quote from: srb on 19 Jan 2015, 05:00 am

That's the inherent mechanical beauty of a cylinder. Given the strength of PVC drain pipe, it would likely take several thousand pounds of force to flex it.

Steve

Oh, if the PVC pipe butts right up against the stand walls, yeah, that would brace them all right. And the four voids between the pipe and the stand's corners would hold plenty of sand for damping. Damn good idear!

Captainhemo · « **Reply #30 on:** 19 Jan 2015, 05:17 am »

I don't think the PVC would even have to taouch the sides, the sand is not compressable so it's the same effect as long as ALL the space between the walls and pipe is filled.

bdp24 · « **Reply #31 on:** 19 Jan 2015, 05:29 am »

Quote from: Captainhemo on 19 Jan 2015, 05:17 am

I don't think the PVC would even have to taouch the sides, the sand is not compressable so it's the same effect as long as ALL the space between the walls and pipe is filled.

Sand is not compressable? Au contraire! I use Silica #60 (great stuff---available at building supply yards) in all my woofer cabinets and metal-tubed stands (along with lead shot in some of the tubes), and it's damping capability is dependent upon it's ability to move. Sure, it's on an almost-molecular level, but that's what vibrations are. No, both bracing and damping are necessary to prevent resonance, and sand does not possess the ability to brace.

Captainhemo · « **Reply #32 on:** 19 Jan 2015, 07:29 am »

Quote from: bdp24 on 19 Jan 2015, 05:29 am

Sand is not compressable? Au contraire! I use Silica #60 (great stuff---available at building supply yards) in all my woofer cabinets and metal-tubed stands (along with lead shot in some of the tubes), and it's damping capability is dependent upon it's ability to move. Sure, it's on an almost-molecular level, but that's what vibrations are. No, both bracing and damping are necessary to prevent resonance, and sand does not possess the ability to brace.

Ok, you got me, shouldn't have said "uncompressabel"

Still think an inner coolum to reduce weight, either PVC or MDF, surroned by sand is going to provide plently of dampening and bracing to some degree. I just don't see a relatively small colum like this filled with sand having a resonance issue

-jay

Folsom · « **Reply #33 on:** 19 Jan 2015, 05:51 pm »

Sand should reduce internal waves, but it's not going to reduce vibrations nearly as much as a brace. It might even encourage some as since the wood will relax less by being pressed out, not held in.

Outofthewoods · « **Reply #34 on:** 19 Jan 2015, 06:59 pm »

Quote from: Salis Audio on 19 Jan 2015, 05:51 pm

Sand should reduce internal waves, but it's not going to reduce vibrations nearly as much as a brace. It might even encourage some as since the wood will relax less by being pressed out, not held in.

If you're up for it it wouldn't take much to test it yourself. Build a small rectangular box the width and height of his columns with 2 inches between the front and back walls. Knuckle test it with and without the sand. I suspect you'll find that the sand alone would be enough to keep the stand from singing along.

You could even double purpose the MDF box by putting the MDF box in with the corners touching the center of the wood panels and fill the corner voids with sand. Make the box a little big and rout, or cut the corners off with a 45 degree bevel to give you a nice glue surface. Lots of a ways to go about it.

Best,

Ruben

Folsom · « **Reply #35 on:** 19 Jan 2015, 07:02 pm »

I can't knuckle at high frequency

It's not that I think sand is wrong, I'd just take other steps first.

HAL · « **Reply #36 on:** 19 Jan 2015, 07:06 pm »

Actually using a small hard object to tap the stand is basically an impulse. It is a broadband signal used in vibration measurements all the time.

Digi-Key sells accelerometers for response measurements.

Folsom · « **Reply #37 on:** 19 Jan 2015, 07:22 pm »

But it's not sustained?

I probably should build myself some new speaker stands. I'm using old horn loaded speakers as stands because they're nearly perfectly sized for my speakers.

HAL · « **Reply #38 on:** 19 Jan 2015, 08:08 pm »

It does not need to be sustained. An impulse can be FFT'd to find the total frequency response of any system.

That is how you measure speakers as well.

bdp24 · « **Reply #39 on:** 19 Jan 2015, 11:21 pm »

Putting a brace on an unsupported panel (such as those of the speaker stand being discussed here) breaks the panel into smaller unsupported panels, reducing the amount of flexure in the panel (flexure of a panel is what causes it to "sing") and raising the resonant frequency of each unsupported section above that of the larger panel. The more braces you put on the panel and the closer they are to each other, the less the panel flexes and the higher the resonant frequency. The higher the resonant frequency the more effectively will the sand will damp the panel. So, simple bracing across the middle of the width and depth of the base every 6" or so vertically, and then filling the stand with sand, will be a very cheap and effective way to make the stand silent. But heavy! Braces will work better than a PVC pipe because they won't allow the panels to flex "outward" (a sealed chamber actually expands like a balloon), which a pipe has no way of preventing. There are those who subscribe to the theory that mass stores energy and releases it over time, creating a "time smear" of the signal (the British "Flat Earth" movement of the Linn school). Pick your poison!