mike1127

Hello,
I'm new this to forum. Good to meet you. I'm not an experienced woodworker, but recently I built a freestanding shelving unit. It's a simple design with four 1x3's as vertical members, and five rectangular shelves mounted to them. It's completely "open"--there are no sides or back. Most of the shelf mountings are made more rigid with 90 degree angle brackets.

The purpose is to hold audio equipment. Audio equipment needs to be very still for best functioning. This rack is sturdy enough by ordinary standards, but it still vibrates too much to be good for use with audio.

I thought I could make it more sturdy in a simple way. I could string wire in an X pattern on the sides and back. It will still be basically "open"---the wire won't obstruct clearance for the components, for the most part. My understanding is that I can get some kind of hardware that lets me put the wire under tension. For example, something that holds two screw eyes, and then you twist this thing to draw the screw eyes closer together. Using relatively high tension will be good, under the assumption it will make the shelf more rigid.

I would like some advice about

• What kind of wire to use
• What hardware to use to mount it to the corners. Note: it can be ugly. This whole thing is ugly.
• What the hardware is called that lets you put it under tension and adjust the tension.
• What kinds of cutters for the wire.
• How to securely attach wire to screw eyes, rings, and the like. For example, how do you get the wire secured in a screw eye? Feed it through, then loop it back and clamp it to itself? Or what?

Thanks,
Mike

Wood4Fun

the whole thing vibrates or wobbles/moves? I don't think anything you do will help with vibration except to make a more solid and substantial unit.

The wire support system you are talking about, I have seen used on things such as fence gates and such. A system like this would help with the unit wanting to wobble or topple over, but I don't think it would stop vibration.
Also, just screwing a "screw eye" into the back of the unit, and then applying the tension, you would likely just rip the screw eyes right out of the wood. The kits used to stabilize fences have a bracket that slips/attaches on to the corners of the structure

In any case, based on what you are describing, and perhaps you didnt' use the best words so I'm not understanding, I don't think a bunch of 1x3's with some shelves attached is an appropriate structure to house audio electronic equipment. The answers to your other questions are pretty straight forward, but I'm not going to address them cuz I don't think you are starting out in the right direction anyway (not trying to be a dick, sorry).
In reality, being that the unit is just 1x3's as its structure, my guess is once you start applying tension to wires, you are going to torque the whole thing out of whack.

Maybe you should just screw the whole thing up against the wall behind it with some brackets?

mike1127

It's plenty sturdy as an ordinary shelf. perhaps we are coming from different worlds so you don't realize what I mean by vibration. It vibrates at somewhere 60 Hz (60 times per second). I can tell this because I put my ear against the side and banged on the floor with a hammer, and I recognized the tone that was produced. I could also hear other tones which are higher, which I could reduce greatly using damping material such as bags of sand.

Regarding the 60 Hz vibration, what I need to do is stiffen the shelf so that it increases in frequency. At such a low frequency I can't do much about it with damping. At a higher frequency the amplitude will be greatly decreased and damping material will be more effective.

I believe the X wire system is actually good design. It's a type of "composite" design from compressive and tensile load members.

Then I won't do that. I'm asking for advice what hardware to get that will truly work.

It's actually very sturdy because each shelf is held with angle brackets. I know that saying it's supported by 1x3s makes it sound flimsy, but you have to consider the structure as a whole.

Of course the tension needs to be balanced on each side of the X, and that will be easy to do. Obviously it's important not to overdo it, but I'm sure that I can easily increase this low frequency vibration mode.

-Mike

cabinetman

You might check out an audiofile forum as there may be some experts there that understand your high/low frequency problem. What they might suggest is for you to check out a woodworking forum on constructing a suitable cabinet to house the equipment.

I also agree that the pulling forces may distort the integrity of your set-up.

But, to answer your question, you are referring to "turnbuckles", like these. The wire would be "galvanized aircraft cable". The clamps you could use are "aircraft cable clamps".

JAC

Mike,

I may be wrong, but I don't see how the wires under tension are going to help with resonance.... unless the joints are loose now. Are the shelves actually attached to the 90 degree angle iron with screws, or just sitting on top of them? Making sure everything is "tight" would probably help, but if its already tight I'm not sure the extra tension you'd get from the wires is going to do much.

I think you'd have better luck setting the unit on a different material. Foam rubber type material (like the big box stores sell as shelf liners) or even carpet would probably change (and dampen) the harmonics more than the wires will.

If you do give the wires a try, let us know how it turns out. I'd be interested in knowing if it works!

JC

demax

If you listen only to high tones your idea will work, but for bass forget it. Nothing will stop the resonance vibration, especially if you have a sub on the shelf. A good sub can move your furniture all depending on how many amps your driving thru it.

I suggest placing the speakers on a solid surface. Besides a sub requires to be placed next to a wall within a distance specified in the spec sheet to get your monies worth. My sub will shake a wall, so I cannot imagine what a few wires could achieve.

GeorgeC

Nothing that you do to the existing structure is going to change it's current vibration characteristics.

Unless you have your speakers on this structure it is not going to be any audio problem. The electronics are not susceptible to vibrations like the speakers would be.

G

Gerry KIERNAN

Cabinetman has the terminology correct, but you don't need cable as heavy as aircraft quality. You can probably get light weight cable, turnbuckles, and eyebolts at a hardware store. I think picture hanging cable would be strong enough. The tension would not need to be very high, and you could tune it by tensioning the turnbarrels. If you tightened too much the unit would likely torque on you. This would give the shelves more stability, but I tend to agree with the others that it won't do much to dampen the vibrations. You could consider putting a board, or piece of plywood across the back of the unit, held with screws. this might dampen it somewhat. If you really want to dampen the vibrations down you should probably consider building your shelving unit out of more substantial material.

Gerry

mike1127

The wires don't dampen the resonance, but they increase the resonant frequency and decrease its amplitude. A higher-frequency and lower-amplitude resonance is easier to control with true damping material.

The shelf is not vibrating because anything is loose---it's "ringing" like a bell. Nearly any structure, including wood structures, has vibrational modes that resemble bells. Wood has too much internal damping for the "ring" to last a long time and convey into the air easily (compared to an actual bell), but it does seriously affect the performance of a wood structure in an audio application.

mike1127

Just to address a few ideas here:

Any structure has one or more resonant frequencies---a frequency at which it vibrates strongly, much more strongly than other frequencies, and can amplify any vibrational input.

Anything, of course, will vibrate along if you put a shaking object touching it. The problem is when the shelf amplifies the vibrations because they are close to the resonant frequency of the shelf.

The goal of the wires is to increase this resonant frequency. Not to damp it, just to increase it. Of course, once increased, it will be smaller amplitude and more damped by the wood's internal damping, and also more damped by some additional material I'm adding.

This shelf is for electronics, not speakers, but vibration does matter for electronics too (for high-end electronics).

The use of wires may in fact be a good design and not just a hack, because it combines compressive elements (the wood) and tensile elements (the wire). It's a kind of composite structure. I'm not a mechanical engineer so I don't know if ultimately this is the best way.

Rick C.

Mike,
I got ya on the resonance,too many years ago loud bands in old barns would really get the rafters ringin'.The ringin's permanant now.
Also,stereos were set up in sturdy enclosures so dust,food and beer didn't get into the system.Fans were in the back to keep the tubes cool.Speakers were enough to shake the neighbor's bones.under the turn table you put a rubber pad or replaced the feet with disc foot pads which stopped vibration even to a light tracking turn table.
Wire will stretch eventually and need constant adjustment.Cable is a better option.IMHO,I'd go with a full enclosure,glass front and rubber pads.

mike1127

Hi Rick,

Thanks for the info. I realized that you are right... this system has the potential to be fussy and need constant adjustment. It is much simple to attach two metal strips. So I attached two aluminum strips, 1" wide and 48" long, in an X pattern. Metal strips do not provide very good resistance to compressive force when they are long (because they buckle); however, I attached them to each of the five shelves which makes them much strong in the compressive direction, because they are shorter and by being attached at multiple points it constrains the buckling.

The shelf needs to be open in front and back because I need to access it easily, so I can't put X strips on the front or back. But I added numerous 8" angle brackets to strengthen it from leaning in the side-to-side direction.

The whole thing is now solid as a rock. I also added compartments along the vertical members and in some of the shelves that I can fill with sand and lead shot. This thing is now rigid and completely dead acoustically.

Thanks everyone!
Mike

woodnthings

Would you be willing to post a picture of the finished result, so we all can get an idea of what you meant and how it turned out? bill

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mike1127

Oh my... it's very ugly. However, as long as you all realize that I do not have a wood shop, do not have good tools, and the whole thing is purely functional, I'll post pics.

frankp

Mike,

I'd suggest building the shelf unit with a different wood. The wires may help raise the resonant frequency, but you'd still be better off with more suitable materials to start. As for the 60Hz, are you sure it's not a power hum? 60Hz is the frequency of AC power in the USA (50 Hz in Europe) and is quite noticeable but I wouldn't expect to find too many wooden structures that resonate at that freq.

If you still want to make the cable mods, the turnbuckels should help make it easily adjustable for cable stretch and accommodate most of the ideas you're talking about. Turnbuckles are easy to find in various sizes at most hardware and hobby shops.

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