1977 Lascala. Reinforcement of the side walls.

[OO1]

7 minutes ago, KT88 said:

 

What means routed tweeter /midrange openings ala LSI?

 

And do you think that the slight shortening of the bass will have an effect? I would say, it has not, I hope, by reducing the length by 0.25 mm.

if you look at the corners of the cabinet+ the tweeter+ K-400 openings , they were rounded with a router bit ,  

[KT88]

does it make an effect soundwise?

[OO1]

   it's more  aesthetic  versus an actual  sound improvement ,  

[OO1]

15 minutes ago, KT88 said:

left and right speaker, this should be ok regarding the horn length?

looks perfect to me 

[KT88]

18 minutes ago, OO1 said:

looks perfect to me 

My conclusion is that I reinforce the sides with about 4mm birch multiplex/veneer. This compensates for the fact that my LS already have 1mm thinner sidewalls in original condition than the usual 19mm to reach reasonably the LSI standard of the 80s  The top I reinforce with about 3mm. 
Do you have any objections to my plan, Randy? Then say it with pleasure.
Thank you very much for sharing your exceptional and historically accurate knowledge of Klipsch products. I am very happy with the info you have shared. I owe you a good tasty German beer or an American quality bourbon, whichever you prefer.

[OO1]

1 minute ago, KT88 said:

My conclusion is that I reinforce the sides with about 4mm birch multiplex/veneer. This compensates for the fact that my LS already have 1mm thinner sidewalls in original condition than the usual 19mm to reach reasonably the LSI standard of the 80s  
 

Heinz  , the LSI had a much denser and  stiffer  plywood versus the softer plywood  used on the LS ,  if I were you , I would not go under 6mm  BB to rigidify  the side walls  and  tame the flex which causes the  resonance   , the other panels can do away with  4 mm  .

[KT88]

6 minutes ago, OO1 said:

Heinz  , the LSI had a much denser and  stiffer  plywood versus the softer plywood  used on the LS ,  if I were you , I would not go under 6mm  BB to rigidify  the side walls  and  tame the flex which causes the  resonance   , the other panels can do away with  4 mm  .

Thanks for the advice, Randy. I will take it into account and choose 6 mm for the sidewall reinforcement accordingly.

[Marvel]

On 6/6/2023 at 3:22 PM, OO1 said:

Heinz     ,   1976 - 1983  plywood  was ...19mm ,  5 ply with a birch veneer on each side , so  7  plys 

Heinz,

To me, your photo looks like 7 plys with the additional 2 veneer plys.

 

Bruce

[Chief bonehead]

On 6/6/2023 at 2:22 PM, OO1 said:

Heinz     ,   1976 - 1983  plywood  was ...19mm ,  5 ply with a birch veneer on each side , so  7  plys 

Klipsch never did “mm” in the day. It was 3/4” +/- 1/32” 

[Chief bonehead]

On 6/6/2023 at 4:50 PM, KT88 said:

Randy, If it is true that the sidewalls were 19 mm on the standard LS in 1977 then the stupid carpenter has planed off almost 2mm. see photo of the sidewall. 
how thick is the motor board of the squaker. Can it be that the carpenter has also planed off? see photo.

 

 

 

 

 

 

 

Back in today Klipsch used 9 ply (7 plus 2 veneer). And for the la scala in particular, the 2 plys under the veneer were made so that it would not telegraph to the veneer. 

[billybob]

So, veneer not telegraph to me means no resonance factor attenuation. If so meaning, the aforementioned plan of sidewall application should be ply,if going ply, say should be the right amount of thick to retain the planed off amount to resonate the amount liked before the planing done. The plan as it exists now, is minimal, if any resonance per sidewall.

[billybob]

Back in the day, of the 77s or, back in today 2 ply veneer.

To me if desired, can veneer without concern of attenuation of resonance.

[OO1]

I own 2 sets  of LSI  ,  regular square corners + 9 ply  plywood   does resonate  -2nd set with  - 7 ply is thicker plywood  ,  no resonance at all

[JohnA]

Inside braces, offset a little, make the most sense from the engineer's point of view. 

 

Second is to add 6mm or so to the outside of the sides of the bass horn.  The addition must be fully glued and should be anchored with a few screws or nails so it fully bonds to the horn walls.  That's a lot of weight for the improvement.  The rest of the bass horn is well braced and needs nothing added. 

 

Had I realized, I'd have added the inside braces before finishing.  Since they don't misbehave until I recreate a rock concert, I don't worry about the resonance.  I did have a 19mm x 19mm strip of solid cherry added to the front edge to cover the edge plys, maybe that helps.