Furiously vibrating La Scala cabinets

[Ray Garrison]

Okay, this is one of those things that, when you don't know about it, doesn't bother you, but once you become aware of it, it drives you nuts...

I've always known that, at rather loud volume levels, my system begins to sound a bit, uh, conjested. That is, the articulation and clarity that the La Scalas exhibit at lower volume levels starts to suffer. I always thought this was due to room interactions and reflections. Earlier this morning, before I headed out to work, I was playing the Rolling Stones Stripped CD at slightly less than you-are-there concert levels. I happened to place my hand on the side of one of the Scala cabinets while Not Fade Away was playing. The side of the speaker, particularly about 18 inches off the floor near the front of the side panel, was vibrating so hard that it HURT MY FINGERS. I checked both sides of both speakers - yep, vibrations were about the same on both sides of both speakers. Even use a jigsaw, and have the blade bind in the cut and the saw start shaking your hand to pieces? That's how hard the Scalas were vibrating. Now I think I know what was causing the sound to loose clarity at higher levels - the cabinets.

So, anyone have any ideas about how to address this? I've seen some shots of horizontal braces that folks have placed inside the throat mouth about halfway up - anyone out there who's done this who can tell me if it made any difference? I'm afraid I'd simply move the resonant frequency up an octave or so, which might make things worser... by the way, I did the Dynamat thing on the squawker horns, and at the same volume levels where the cabinet sides were vibrating like crazy, the squawker horns felt practically inert. Very little vibration you can feel by placing your hand on the inside of the squawker horn, anywhere. Anyone think Dynamat might have similar effect on the bass horn?

As always, thoughts and comments appreciated...

A side note - the air currents in the bass horn at reasonable volume levels are way cool. While I was poking around this morning, I tried lighting a match and holding it in front of the bass horn, about half way up and just outside the mouth of the speaker, to see whether the flame would dance around. It BLEW OUT THE MATCH.

Ray "Eh? What'd you say? Speak up, I CAN'T HEAR YOU" Garrison

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Music is art

Audio is engineering

[Prana-Bindu]

In addition to whatever solution you find, have you considered loading the speakers in much the same way suspension systems require loading? In other words, place weight on top of speakers; sandbags should load and provide some damping at the top as well.

As far as the primary fix goes, I've seen vibration damping panels made for the backs of subwoofers. I can't recall the specific info, but they're available at Audio Advisor. Otherwise, how about rebuilding your cabinets in granite or some kind of space-age, non-resonant plastic? Treating the cabinets with dynamat itself would take out at least some of those vibrations....

Nevertheless, I suspect you don't want to damp the vibrations as much as you want better coupling of the cabinet rigid structure. Besides bracing, I don't see any other solution that does not involve different cabinet materials/design.

Let us know what you decide to do.

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May the bridges we burn light our way....

[fini]

Ray, fini the carpenter talking here. Just an idea on experimenting around. How about clamping some bracing (such as 2X4's wrapped in a towel to keep them from scratching) to the speakers? I'm thinking a pipe clamp across the back of the speakers (holding the 2X4's), and small Quick Grips holding them to the walls of the speaker in front, then another 2X4 attatched with screws to the side 2X4's across the front. This may stop the vibration, so that you can hear if that's the problem, but it sounds like you've deduced that already. Just 2 cents from fini. By the way, if you try this, make sure you have auxilliary supports for the braces and the clamps for if (when) the vibrate loose.

Cheers! fini

p.s. I hope your finger feels better

[Ray Garrison]

fini,

I think I followed that... where does one get a pipe clamp? Zat something Home Depot would have? Also, how, uh, "deep" is the "throat" of a pipe clamp? Would I be able to put a 2X4 in the middle of the outside of the side wall, or won't the clamp reach that far around from the back of the speaker to the side? Cool idea... Thanks...

Ray

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Music is art

Audio is engineering

[Jim Cornell]

Ray, how are you!!

Listen, if you can get to the insides of your la scalas, there might be factory screws that need to be tightened!!!

Inside of my cornwalls have screws!!

If so, pull out the screws, put elmers on them, then drive them back in!!

I hope thats all youd have to do!!!

Good luck Jim

[fini]

Ray, pipe clamps are available at Home Depot (or any larger hardware store). Jorgensen makes the standard of the industry, but lots of companies make them. They're called pipe clamps because you use a length (any length) of pipe (1/2" or 3/4", depending on which type you get) to connect the clamp parts together. One end screws onto the threads of the pipe. The other part slides up and down the pipe, adjustable to the size of the thing you're clamping. Once it's slid close, you tighten it with the screw-deal (technical term), applying as much pressure as you want. So you get a length of pipe, say, a foot longer than the thickness you're clamping (the width of the speakers plus two 2X4's), give or take.

The throat depth of a pipe clamp is only about 1 1/2". there are other types of clamps with deeper throats, but if you try to clamp the middle of the sides of the cabinets hard enough to eliminate the vibration, you would probably distort (bend in) it, possibly damaging something like the joinery or finish. My idea is for you to stabilize the sides where they are.

Is this clear? I know this stuff is hard to visualize, and describe. Did you get the part about the 2X4 across the front? That's also to keep the box from distorting. Once you have this bracing in place, you can use a type of deep throated Vice Grip clamps with swivel tips to clamp the sides to the 2X4's. Remember, though, to cushion between the clamp and the speaker, so you don't scar the finish. Also, a falling clamp can really do damage. Take care. fini

[Q-Man]

I suggested fini's idea to John Albright some time ago, because he to wanted to address this problem. I never heard back from him, so I don't know if he tried it & if he could hear a differance, if he did.

It's a solid & simple way to brace the cabinets & the best part is that it's reversable. I suggest you try it & let us know what you think.

Q.

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Q-Man

This message has been edited by Q-Man on 08-14-2001 at 06:20 PM

[WMcD]

Ray,

When I've built variations on the LaScala and Belle I put in such a brace. So I can't give you a with and without comparison.

There is the well reasoned theory that if a plate has a vibration in the middle, and then you secure it in the middle, then you wind up with two half sized plates with a higher resonance, which reinforce at that higher frequency. None the less it is probably a very much smaller problem. Higher frequencies are more easily damped. An alternative is to brace the sides at about a 2/5 ths position so the resonance modes don't overlap.

A simple pipe clamp is just going to compress the sides together. Good, but then you have some chance of warping the plywood. Okay for a temporary experiment. You might be able to accomplish much of the same by a tight "belly band" around the circumfrence, 1/2 or 2/5 the way up. The belt might be as simple as a rope tournequet. Whatever mechanism you need to make it snug enough to prevent vibration of the panels.

If I was going to experiment beyond a belly band, I'd buy two pieces of 1 x 2 inch lumber cut to 24 inches in length and six cheap C-clamps . The position the lumber at the outside face of the side uprights of the mouth. Hold them in place with the C-clamps, top, middle and bottom. Some cardboard spacers can be placed between the place where the C-clamps engage the beloved speakers to prevent maring.

If any of this works well for you, I think a simple brace is the best way to go. I leave that to your woodworking ability.

My guess is that even with a brace or the above, you can still blow out matches. =8^o.

Now think about it. When Dr. Paul's birthday comes around again, it would be a panic if the birthday cake candles could be blown out this way. It might take the big theater woofer in view of the number of candles. But it could be done.

Gil

This message has been edited by William F. Gil McDermott on 08-14-2001 at 08:05 PM

[TBrennan]

Ray--Until recently I had Peavey FH-1s, a W basshorn very similar to the LaScalas. These had a brace in each side of the mouth, the brace being a 1" shelf that ran all the way back to the corner. These horns also had a 3/8 layer of MDF added to the outside surfaces and a thick oak veneer over that. They were inert, dead, no movement. You can see the horns on my site.

[John Warren]

"what was that cracking sound?" thought Ray as he turned the screw of the bar clamp just alittle farther than he should have.

This message has been edited by John Warren on 08-15-2001 at 05:58 PM

[John Warren]

Jim,

I did that trick once, and then I had to remove the panel a couple of years later and guess what....

[Klipschguy]

Ray,

How about a "belly band" which is supporting a sizable sandbag on either side of the cabinet - that should give good damping and be reversible. For esthetics, you could use some kind of cool print fabric to make the sandbags.

Just trying to help out.

KG

[JohnA]

I haven't tried the 2x4 brace thing in my La Scalas because I haven't decided it is that severe a problem and I don't want to mar the finish. I plan to add a "shelf-brace" to my rear channel La Scalas when I can afford to refinish them.

It will look like this: http://www.hps4000.com/pages/525_.html

I'll put the brace at the 40% point from the bottom of the basshorn.

John

This message has been edited by John Albright on 08-16-2001 at 11:08 AM

[Randy Bey]

Ray,

have you thought about pouring cement around your LSs?

You could do a "Close Encounters" thing and shape the cement like Devils Tower. Your wife would understand.

Or, hey, you could turn the volume knob about 20 degrees counterclockwise. Just because your speedometer goes to 120 doesn't mean you should drive your car that fast.

[fini]

John, please re-read my post. I'm not suggesting squeezing the speaker sides in, rather, stabilizing them where they are. That's the idea behind the front brace that goes across the front of the speakers and attatches with screws to the side braces, which are held flush to the front edge of the cabinet. This, in effect, would create a 2X4 frame around the speaker (held at whatever height you wanted, play around with it) that doesn't hard-connect (nails, screws) to the cabinet, but is held with various clamps.

Here's another idea, less complicated (darn!) and probably better. For each speaker, cut two 2X4's the height of the speaker. C-clamp them,one on each side to the speaker flush with the front edge, top and bottom, taking care to protect the surfaces with something cushy. Then place more c-clamps along the 2X4/cabinet edge at various heights and see what that does. This is basically Gil's idea, as I understand it. This might simulate what would happen if you did a permanent brace FROM THE OUTSIDE, like adding stiffening panels (matching the finish of the speakers, or even a design that aesthetically ties the speakers to other cabinet or architectural features in your listening area). This could be pretty cool, I think.

A REALLY simple approach to experiment with an internal brace would be to cut a piece of wood (1X2?) to the inside dimension, side-to-side, of the speaker. Hold it in place across the front of the speaker, in-between the sides, flush with the fronts. Grab the ol' pipe clamp (oh no!), and clamp the stick between the speaker sides. You might also want to grab the ol' lady (not THAT way!) to help you with this. Extra hands and all. Experiment: up and down, in and out (with the brace, I'm talking, now), maybe you'll find something that "feels" good (you know, I'm serious about this, but you know where my mind is going... ). Anyway, make sure you use protection (to protect EVERONE'S fine finishes).

I'm spent. fini

P.S. Now, when someone searches the forums for posts that include "furiously vibrating," "squeezing," "stiffening," "stick between," and "in and out" they'll end up here. Isn't English fun?

This message has been edited by fini on 08-16-2001 at 11:01 AM

[Ray Garrison]

Just wanted to thank everyone for their thoughts and ideas. You may not see a post from me about this for a couple weeks, am going to Tampa to visit with parents for vacation, but will try some ideas when I get back and let you know what, if any, worked.

Prana-Bindu, think you were referring to the Tekna plates. AA has money return policy, but I think you have to permanently attach the mounting plates to the speakers. Not sure what would happen if I tried to take them off. Anyone else tried these on anything? http://www.audioadvisor.com/store/mfglisting.asp?hdnMfg=Tekna&MFGID=134

Jim - screws are tight, except possibly for those in my head. Panels are vibrating due to flexing, not looseness. And these are the old, think, solid birch plywood versions...

Fini - thanks for suggestions. Will try this... NO NO NO not THAT, I meant the wooden braces thing..

Tom - uh, being all thumbs as I am, I doubt I'd wind up with anything as cool looking... Did you do the veneer? My La Scalas are a painted black over raw unfinished plywood, with numerous little chips and dings, would love to refinish them.

Randy - reducing volume is not an option. Knob continues to advance ever more clockwise, of its own volition, can't seem to help it, nothing succedes like excess...

John Warren - no, the cracking noise wasn't the La Scala cabinet giving in, it was the tile floor the last time I had some buds over and played the William Tell Overture and their jaws dropped...

Thanks All!!!

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Music is art

Audio is engineering

[sunnysal]

Ray, my two cents...that amount of vibration (more like out and out shaking of the panel) does NOT sound right...that's why Jim's question about screws sounded "right track" to me...my k-horns have larger unsupported panel areas than your la scalas (right?) and no matter the volume including cover your ears, big bass stuff, there is nothing more than a mild vibration...no waggling...no real movement...so assuming that really nothing let loose inside (please check again) then it seems a simple brace wedged, screwed and glued, as decribed by others here on this thread, in the space with the largest unsupported span is your best bet and should do it...hold off on any dampening or mass loading efforts until you support the panel and it is not flopping around, those measures are fine tuning, what you have there if flippy-flopping (that's a technical term)...good luck, let us know how it goes...tony

This message has been edited by sunnysal on 08-16-2001 at 01:06 PM

[fini]

Oh, one more thing, along the lines of something loose. Could be some little varmints runnin' loose in there somewhere. I had opossums under my house once. If anyone is interested in hearing about their successful erradication, I'll give the gory details. Just brace yourselves.

fini

Oops! Meant to post this under "Furry Vibrating La Scalas" topic. Sorry.

This message has been edited by fini on 08-16-2001 at 03:05 PM

[dbflash]

Ray,

I don't know if this will help, but I was just talking to a Klipsch dealer about mods I could do to my KLF20's. He said that what he did was to us the Dynamat on the inside of the cabinets. He said that would keep the cabinet's from vibrating as much.

Good Luck.

Danny

[djk]

"my k-horns have larger unsupported panel areas than your la scalas (right?)" Actually, no.The unsupported sides of a LaScala are 4 sq ft.There are no unsupported panels this large in a Klipschorn.A Klipschorn can sound quite 'woodey' when played loudly.The two biggest problem areas are the exit slot at the back where the sound exhausts into the corner and the top and bottom slopes of the woofer chamber.A pair of 2.5" wide strips of .5" thick Baltic Birch that go from top to bottom are easy to add. http://www.artandaudio.com/krear.jpg The other surfaces are much harder to fix.The Lascala is easy to fix compared to the Klipschorn.