Quake bracing for CLXs?

[jshowalter]

We live in the Santa Cruz mountains, a few miles from the epicenter of the 1989, magnitude 6.9, Loma Prieta earthquake.

I noticed that a CLX can be tipped forward by just a few pounds of tension on the top.

A quake would likely cause our CLXs to topple. If we're lucky, it would just smash the panels, which could hopefully be replaced. If we're less lucky, the aluminum frames could be scratched (or bent).

So I'd like to find a way to brace the CLXs to prevent damage in a quake. But everything I've thought of has drawbacks. For example, a tight "lasso" of stainless-steel cable running around the frame near the top, then tied to a cable attached to the wall. This would probably work, but unless it's really tight it could slip off, and if it's that tight it could scratch the frame. Plus it would add a horizontal line in the front, detracting from the appearance. Drilling through the frame front to back at the top is a non-starter. Drilling and tapping into the frame at the top is less awful, but still causes permanent changes to the frame. Attaching the base (via the threads used for the spikes) to forward-projecting metal bars on the ground could work, but it would be ugly, people could trip on the bars, and it would prevent adjusting the angle of the speakers. Standing the speaker on the center of a net, and pulling the net upwards and over the speaker, attached to ceiling, would work (probably very well, because a net is great at dissipating energy), but would look really ugly. And so forth.

Does anyone else with CLXs live in earthquake country? If so, have you done something to quake-proof them? If so, what?

 

[tsv_1]

Some folks place heavy stone tiles on the lower cabinet of the CLX - the intent being to deaden the unit and add mass, thus improving bass response. This would also help "pin" the CLX to your floor by significantly lowering it's center of gravity, thus potentially improving it's chances of remaing vertical when terra firma ain't so firm-a. Or go the extra step and look at ways to physically attach the speaker to the floor.

 

[jshowalter]

I think I have a solution.

On the tops of the CLXs, there are a couple of foam blocks. Under those are some allen-head screws. Some high-tensile stainless-steel cabling could be custom-made to be swaged into eyelets, the eyelets held down by the allen-head screws (perhaps replacing the washers), and the other ends of the cables attached to studs in the walls behind the speakers.

That will prevent, or at least greatly reduce, the chance of the speakers falling forward. It would still be possible for the speakers to lurch backwards into the wall, but that will just damage the ecowood vertical baffle, which presumably can be replaced because it's the the same for all CLXs.

 

[Hocky]

I have a solution: home owner's insurance. :-\

 

[RUR]

I have a solution: home owner's insurance. :-\

Hocky, in California, that's really not a viable solution. For me and the majority of others, separate earthquake coverage is required and, since one of the "recent" big quakes (Loma Prieta or Northridge - can't recall which), coverage limitations are absurd. Personal property coverage, for example, maxes out @ $100K. To save us from high(er) premiums, so-called "costly non-essential" items like detached structures - my garage and audio room, for example - swimming pools and yard walls aren't covered at all.

 

[Hocky]

Hocky, in California, that's really not a viable solution. For me and the majority of others, separate earthquake coverage is required and, since one of the "recent" big quakes (Loma Prieta or Northridge - can't recall which), coverage limitations are absurd. Personal property coverage, for example, maxes out @ $100K. To save us from high(er) premiums, so-called "costly non-essential" items like detached structures - my garage and audio room, for example - swimming pools and yard walls aren't covered at all.

hrm... bummer.

 

[User211]

jsowalter - do you see your last suggestion as better tham placing mass on the base? If so, why? Just curious.

This inspired my memory of this thread, which I am sure you will find interesting WRT earthquakes - and loudspeakers.

http://www.audioworld.com/sw/Forum1/HTML/005636.html

BTW: earthquake stuff starts page 2.

 

[jshowalter]

It's just leverage. If I grab it at the top, I have 70.3" of leverage. If I weight it, I have only 14.69" of leverage, and because the weights would probably press down evenly on the whole 14.69", I have to divide that by half (on average), so it's 70.3 : (14.69 / 2), which is about 9.5 : 1. So 10 pounds at the bottom is the same as 95 pounds at the top.

 

[jshowalter]

I'm using 304 stainless steel aircraft cable, 1/8". That has a breaking strength of 2100 pounds, which should be enough!

If I can rig it correctly, I should be able to attach the cable to the wall with a friction sleeve and extra length, so it will "soft" catch the speaker if it tips forward (instead of yanking it).

There are two recesses for bolts in the top of the frame. The one on the outside (away from the center of the soundstage) has two bolts. I'm going to run a flat piece of stainless steel between the bolts (they're spaced 3/4" apart), with dimensions 1+1/4" x 1/2" by 1/8" (thick), with a few stainless steel washers underneath, which will create a gap between the bolts large enough to run the cable. With some Tygon sleeve over the cables, it shouldn't scuff anything, and it can be removed later with zero changes to the speaker.

 

[Krazikiwi]

Movers and Shakers

Based on the experiences of New Zealand's recent earthquakes, securing taller items to wall studs and hence the house itself, means they oscilate at a lower frequency when excited by earthquake energy. Any inertia absorbed gets "drained" back into the house structure which moves at a slower frequency during the 'event'.

My recommendation is to use at least 2 securing screws into the stud so the area of energy dispersion is doubled as well providing a backup restraining point.

Hope this helps.

Fjeff

PS: do you have the ability to secure from underneath the speaker to the floor joists? If so, strips of galvanized strapping (usually used to secure hot water cylinders) between the speaker underside and floor will also serve to "drain" energy out of the speaker into the house. A bit of movement should be allowed as you are trying to roll with the tremors not resist them and cause things to snap, the likelihood of the straps distorting and being replaced (like a fuse) is high but no biggie if the speaker is saved.

 

[jshowalter]

Thanks! I thought about securing them to the floor, but it's a nice hardwood floor and drilling holes in it is bad. It's already got spike dimples in it!

I'm going to secure them to the studs with massive lag bolts and a strong loop for the cable.

 

[zaphod]

keeping with the wire approach, have you considered running the wire straight up and attaching it to the ceiling instead of the wall? if you attach to the wall, you really need more than 1 point of attachment (3 actually) to really be certain of keeping it up, but attaching to the ceiling requires only one wire.

 

[MPS]

How about building a platform under the speaker? Made from wood, metal, acrylic or stone with dimensions greater than the speaker itself and the fixing the speaker to the platform it would make flipping the speaker over almost impossible. Place slippery material under the platform not to scratch the floor while still being able to push it around for optimal location.

 

[jshowalter]

I thought of attaching the cables to the ceiling, and may still do that. It has the advantage of absorbing lateral energy without putting much strain on the speaker or the cable, plus it can prevent tipping backwards as well as forwards. It has the disadvantage of being visible.

 

[Gordon]

All joking aside, I thought I had it bad with a too small a room for the CLX! Although here in MD we did have a quake a couple months back and never thought about my gear. I was more concerned about my 1940's house!! An interesting thread to say the least.Perhaps a Carbon Fiber filament to the ceiling? Very thin and almost invisible if purchased in a thin diameter?

Gordon

 

[tsv_1]

I still say mass-load the bottom cab... lower the center of gravity (and potentially improve bass response at the same time)... no holes, wires, or marrionetteism of any kind.

And/or, a variation on MPS's suggestion above... shop around for outrigger legs.

 

[slowGEEZR]

tsv_1 is right, mass load. Here's an elegant solution. Buy two Clearaudio Statement turntables. Position and connect to each CLX by method of your choice. The Statement is supposed to keep steady in earthquakes and on board ships at sea, so your CLX's should be good to go!

 

[jshowalter]

I looked into using carbon-fiber cable, and found some that would work and for a reasonable price, but the problem is how to form loops in it.

The vendor says: "Bare fiber is very sensitive to abrasion and will have much lower strength than coated fiber. If you clamp the fiber with much force the filaments will be pulverized."

I'll stick with 304 stainless.

 

[jshowalter]

Solution to CLX quake-bracing problem



Materials from Loos & Company, via Amazon (in the Industrial and Scientific section):

- 1, 4386, Stainless Steel 304 Rectangular Bar, ASTM A276, 1/8" Thick, 1/2" Width, 12" Length

- 1, SC06319L, Stainless Steel 304 Wire Rope, 1 x 19 Strands, 1/16" OD, 50' Length, 500 lbs Breaking Strength

Materials from Duckworks Boat Builders Supply (http://www.duckworksbbs.com):

- 1, SIT-3161, Cable Cutter

- 1, SIT-2001, Small Swaging Tool

- 4, 1/16" Swaging Sleeves (plus a few spares for mistakes)

Materials from Backcountry (http://www.backcountry.com):

- 2, PTZ0200-SCR-ONSI, Petzl OK Manual Screw-lock Carabiners, polished

Materials from Fastenal (http://www.fastenal.com):

- 12, RW4360016SS1G00, 1/4" hole, 0.5" OD, 18-8 Stainless Steel Flat Washers

- 6, 0172491, 1/4"-20 x 3-1/4" 18-8 Stainless Steel Button Socket Cap Screw

Materials from Web Rigging Supply (http://www.webriggingsupply.com):

- 2, 3192S-10, Lag Ring Bolt

Tools I already had:

- Variable speed drill

- Cobalt drill bits, set

- Set punch

- Vise

- Soft jaws for vise

- Hacksaw

- File

- Wire wheel that fits drill

- Thread-cutting oil

- Machinist's ruler

- Paint thinner

- Rags

Procedure:

File one end of flat bar smooth, then carefully measure and mark from that end so that, after accounting for width of hacksaw plus filing, the result will be two 1+3/8" lengths of bar, with two 9/32" holes on exactly 3/4" centers.

Drill the holes before cutting the bar, so the vise has something to grip. To drill the holes without a drill press, use slow speed, and start with small bits and work up to final size. And be sure to wear safety goggles--304 stainless doesn't like being drilled, and it flings sharp flakes at your eyes in protest.

Countersink, polish, cut, and file the two sections while the remainder of the bar is in the vise.

Use a lot of cutting oil throughout this process.

Use paint thinner to clean off oil when done.

That was the hard part.

Install a ring lag bolt behind the speaker wherever there is a stud and hopefully behind the speaker (when viewed from the front), and try to match the location on the other speaker. It's not clear if the cable should be horizontal from the speaker to the wall, or if the cable should rise above the speaker. Horizontal looks better (it's not visible from the front), but above the speaker might yank less on the cable (but without dynamic modeling it's not obvious how the speaker will try to move in the event of a quake).

Remove the two cap bolts and washers from the rectangular recess on top of the aluminum frame upright.

Cut a length of cable long enough to reach from the rectangular recess to the ring lag bolt, with a couple feet of extra length.

Run one of the new cap bolts through each hole in the length of metal, put two washers on the cap bolts under the length of metal (between the length of metal and the speaker frame), set the assembly gently in the rectangular recess, run the length of cable under the length of metal, bend the length of cable in a U with about a foot of cable on one leg of the U and the rest of the cable for the other leg of the U, squish the U so the length of metal can be pressed down into the rectangular recess, finger tighten the bolts, then tighten the bolts with an allen wrench. Make sure the length of cable sits between the two stacks of washers.

Swage the one-foot length of cable onto the rest of the length, while bending the cable to go in the desired direction when attached to the wall (so the swaged loop doesn't wind up fighting the cable being pulled in the desired direction).

Attach carabiner to ring lag bolt.

Swage loop on the cable behind the speaker, setting the desired distance to the carabiner. Run carabiner through loop, and lock it.

Repeat for other speaker.

If the speakers are never ever going to be moved, the carabiner can be dispensed with.

If a slightly-less-visible installation is desired, the ring lag bolts can be replaced with 2, 42141, 1/4" x 2" Forged Lag Eye Screw No Shoulder HDG from Fastenal, but they are unfortunately only available in galvanized, which I don't like.

This was kind of a pain. It would be great if Martin Logan offered an off-the-shelf solution to this problem.

By the way, originally I just wanted to get two stirrup fasteners to avoid having to make the lengths of steel, but they weren't available with a 3/4" spacing.

 

[jshowalter]

Here's what I mean by stirrup fastener.