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Strengthening La Scala cabinet?


Dave MacKay

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I'm in the process of refurbishing my new-to-me 1986 La Scalas. I've removed, cleaned and refreshed the tweeters, squawkers, and woofers and have replaced the old AL networks with new Crites AA networks. The cabinets had some damage which I have now (mostly) repaired. My next steps are to strip the existing polyurethane finish and then veneer and finish the cabinets.

 

It has been suggested to me (by @Islander and others, and from searching the forum) that I should consider reinforcing the bass bins on the La Scalas because the cabinet side walls can flex (or vibrate). I'm not sure how big an issue that is, but I figure that, if I'm going to reinforce the cabinets, now is the time to do it.

 

I'm trying to choose between 3 options:

  1. Laminate 1/4" Baltic Birch panels to the top, bottom, and sides (but not the front or back) of the cabinet exterior. I'd apply the Baltic Birch panels with TiteBond glue and brads or pins. This has the attraction of providing a clean, new surface for the veneer. However, I'm concerned that such a major alteration might destroy the value of the speakers.
  2. Install braces (see photos) between the the doghouse and the sides of the cabinets. For the sake of appearance, I'd likely mount them symmetrically at the mid-point of the bass bin. I would make the braces out of 3/4" Baltic Birch and fasten them with glue and maybe brads (if I can get my air nailer in the tight spaces). This would provide reinforcement without changing the dimensions of the cabinets.
  3. Leave things alone. Don't add any reinforcement and leave the cabinets as they are (apart from veneering and refinishing them)

 

I haven't found a shop to re-veneer the cabinets so that I'll likely have to do that myself. I plan to work from large sheets of paper-backed veneer that I'll apply to the cabinets with contact cement. 

 

I'd appreciate getting advice, cautions, and opinions from forum members. Hearing from those who've been there/seen that would be particularly helpful.

 

Thank-you.

 

vs7.jpg

lsbrace5.jpg

Edited by Dave MacKay
Correct a spelling mistake
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Unless I'm mistaken, putting them at the midpoint raises the resonant frequency by two.   I think you might be better off by offsetting them by a tiny amount (1/8", 1/4"?) from center.  Then you present two different resonant frequencies, one higher than fundamental / 2 and one lower than fundamental / 2.

 

Am I right on this?  The amount you'd have to move them off-center would mean that you couldn't visibly tell they weren't centered.

 

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Using the LaScala II as my reference (I've never heard a 'stock' LaScala with the braces inside)

 

None the less, I'd put the braces in or add something to the exterior (like a 1/4" sheet of something to strengthen it up)

 

According to Mr. Hunter, if you fix the sides from resonating, they will sound more like the LaScala II's which don't resonate.  I think it's one of those you'll notice it once you hear the difference.

 

If you compare the original LaScala to the II's, there is a noticable difference in bass output.  Sounded (to me) like a whole octave was added in.  Mr. Hunter told me that the same output is in the earlier versions, it's just masked by the sides resonating.

 

Roy also has a PEQ that will take that out if you were to actively biamp this with something like the K402 or 510 on top.

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My 2 cents. 
1) What I had identified as resonances in the side walls of my 1977 Lascalas was, crazy enough, a completely different sound after I replaced the sonicaps of my Crites AA crossover with polyester caps. Because somehow the timing of the mid and bass was better coordinated and a voice now sounds like one piece. Nothing will have changed in the resonances of the side walls but the timing is psychoacoustically different and more pleasant.

2) If I were you, I would urgently work with a temporary solution that is reversible before gluing and nailing. Listen to the result in peace and quiet, maybe even for a week or two.
For one thing...each additional brace takes away a part of the calculated exit area of the horn, and thus in principle also reduces the deeper bass reproduction.
On the other hand...for me a Lascala is like a well-tuned musical instrument. It is (anyway) far from being a neutral loudspeaker, a fact which I personally welcome. So again, I'd go with braces as long as it's reversible. I could also imagine strengthening the entire walls from the outside, but it would not be reversible, or only at great expense. 
I remember a story I heard about this. Klipsch supposedly experimented with the woods when developing the Lascala 2. The result was that thicker MDF sounded better than thicker Birchply. But that doesn't mean that the Birchply thickness of the old Lascala doesn't have strengths compared to thicker MDF. Maybe a thicker enclosure is better for Nirvana but maybe the old Lascala1 cabinet is better for Pablo Casals?

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Add Dynamat or KilMat to the interior of the dog house. I've heard other users do this, and it makes sense. I added KilMat to my Heresy I mid horn, and the result was very pleasing. Better highs and lows, more detail in the mids. 

 

Additionally, Klipsch now includes foam for the AL5 doghouse. Try it. You'll like it.

 

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40 minutes ago, pcbiz said:

Add Dynamat or KilMat to the interior of the dog house. I've heard other users do this, and it makes sense. I added KilMat to my Heresy I mid horn, and the result was very pleasing. Better highs and lows, more detail in the mids. 

 

Additionally, Klipsch now includes foam for the AL5 doghouse. Try it. You'll like it.

 

How much foam padding would be appropriate? Does the foam need to be placed anyplace specific, or fastened somehow? Or can it just be left loose?

 

I've heard of people wrapping their squawkers in Dynamat, but hadn't heard of using it on the bass bin. I'd be interested in any experiences people have had.

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2 hours ago, KT88 said:

 

2) If I were you, I would urgently work with a temporary solution that is reversible before gluing and nailing. Listen to the result in peace and quiet, maybe even for a week or two.
For one thing...each additional brace takes away a part of the calculated exit area of the horn, and thus in principle also reduces the deeper bass reproduction.
On the other hand...for me a Lascala is like a well-tuned musical instrument. It is (anyway) far from being a neutral loudspeaker, a fact which I personally welcome. So again, I'd go with braces as long as it's reversible. I could also imagine strengthening the entire walls from the outside, but it would not be reversible, or only at great expense. 
 

I wondered what affect the volume and mass of the braces would have on the sound, but figured that, since it seems to be a frequent modification, it mustn't be too significant. Also, after I finish refurbishing the La Scalas, I plan to build a THTLP subwoofer (see https://billfitzmaurice.info/THT.html) which should provide plenty of low-end bass.

 

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I'm not an engineer nor did I stay at a Holiday Inn last night....so take my comments with some grains of salt.

 

That said, as per Roy's comments, if a speaker needs foam inside the doghouse, they put it in.....if it doesn't.....they don't.

 

The inside of the LaScala doesn't have it therefore I conclude (based on Roy's comments) it doesn't need it.

 

It's not the doghouse that's resonating anyway.  It's the huge outer panels that you are trying to tame, not the inner panels.  The inners are much smaller (duh) and are mounted on the top and bottom.  It's the huge soccer field sized side panels that are large and unsecured on the front edge that needs tamed.  Foam or dynamat or a box of chocolates won't help the outer panels if it's on the inside.

 

 

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3 hours ago, Coytee said:

I'm not an engineer nor did I stay at a Holiday Inn last night....so take my comments with some grains of salt.

 

That said, as per Roy's comments, if a speaker needs foam inside the doghouse, they put it in.....if it doesn't.....they don't.

 

The inside of the LaScala doesn't have it therefore I conclude (based on Roy's comments) it doesn't need it.

 

It's not the doghouse that's resonating anyway.  It's the huge outer panels that you are trying to tame, not the inner panels.  The inners are much smaller (duh) and are mounted on the top and bottom.  It's the huge soccer field sized side panels that are large and unsecured on the front edge that needs tamed.  Foam or dynamat or a box of chocolates won't help the outer panels if it's on the inside.

 

 

 

An A/B test is in order here. In my A/B, I saw improvement. Not a maybe. A real improvement. My ears don't lie, and neither do yours. Life is an A/B test.

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3 hours ago, Dave MacKay said:

How much foam padding would be appropriate? Does the foam need to be placed anyplace specific, or fastened somehow? Or can it just be left loose?

 

I've heard of people wrapping their squawkers in Dynamat, but hadn't heard of using it on the bass bin. I'd be interested in any experiences people have had.

Look at the AL5 video on the Klipsch website. It looks like they slide foam into the doghouse without fastening. Others have placed Dynamat or foam in the doghouse and had similar good results, taking the tip from the AL5 construction video.

 

Another thing the new La Scalas have is heavier wire, which will improve old speakers as well.

 

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14 minutes ago, Peter P. said:

This was going to be my suggestion. But my first thought was, if the cabinet need reinforcement, the PWK would have put some in there!

PWK wouldn't, but the current Klipsch engineers definitely have.

 

Just look at the AL5 construction video. You will see a factory worker putting foam in the AL5 doghouse.  The factory also uses heavier wire than PWK recommended.

 

Advancement continues with the greatest respect to PWK. That's the nature of engineering.

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For a few years all the La Scalas I bought had a few things done to them. Recap the crossovers makes a difference. I never got fancy and Dayton 1% or Audyn red caps worked just fine and the AA type crossover was the one I used. Replace that K-77 with a new tweeter. Most importantly I either beat the old sides off and replaced with 25mm Baltic Birch or put mid braces in there. This makes a huge difference and kills all the side wall resonance which is far worse than you think. I never had trouble with resale value either as those hunting for La Scalas and familiar with them could tell immediately they were superior sounding. You have no idea how bad that resonance can be. What started me doing this was one day I was sanding with an orbital sander and when I got close to the front edge in the center the sound was quite loud but towards the sides not nearly as loud. One thing leads to another and I decided to try a mid brace and never reconsidered. On placement. I could not tell any sound quality difference with the center off a bit or on dead center but appearance wise dead center looks MUCH better.

29 minutes ago, pcbiz said:

PWK wouldn't, but the current Klipsch engineers definitely have.

Yes he did consider mid braces. On the forum there is a picture of him in his speaker tinkering room and behind and to the left of him is a La Scala with mid braces. Why simple fixes for problems were not implemented I don't know.

 

  For anyone who doubts the efficacy  of these braces try this. Take a bar clamp and two pieces of plywood. Span the front center of the cabinet and clamp those pieces of wood down on the side and see for yourself. Easy test to prove concept before altering what is there.

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10 hours ago, Dave A said:

  For anyone who doubts the efficacy  of these braces try this. Take a bar clamp and two pieces of plywood. Span the front center of the cabinet and clamp those pieces of wood down on the side and see for yourself. Easy test to prove concept before altering what is there.

 That sounds like a great experiment. The other day I installed 2 inch solid pine risers on my Chorus IIs. The original risers were tattered and ripped, and I figured 2 inch risers were the best option. Besides, they look more like the current Klipsch lineup. To my surprise, the 2 inch risers took away some of the resonance from the cabinets. The bass was tighter, and the highs were clearer. I'm pretty sure that's one of the reasons the new Klipsch speakers have 2 inch risers vs the older plywood risers.

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52 minutes ago, pcbiz said:

 That sounds like a great experiment. The other day I installed 2 inch solid pine risers on my Chorus IIs. The original risers were tattered and ripped, and I figured 2 inch risers was the best option. Besides, they look more like the current Klipsch lineup. To my surprise, the 2 inch risers took away some of the resonance from the cabinets. The bass was tighter, and the highs were clearer. I'm pretty sure that's one of the reasons the new Klipsch speakers have 2 inch risers vs the older plywood risers.

OK you mention 2" risers vs plywood. What exactly is the new riser construction in material and thickness and how is it put together? All the risers I have had for Chorus speakers were in great shape and I never noticed any resonance.

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1 minute ago, Dave A said:

OK you mention 2" risers vs plywood. What exactly is the new riser construction in material and thickness and how is it put together? All the risers I have had for Chorus speakers were in great shape and I never noticed any resonance.

 

I didn't notice the resonance until it suddenly disappeared. Solid pine, 3/4 inch thick, 2 inches high, solid corner braces.

Chorus II risers.jfif

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