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Question on design decisions on La Scalas


Dave A

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 I had to pull the bottom off a pair of Industrial La Scala this week. While doing so I see for the first time the guts of a La Scala. Now one thing leads to another  and I find a PDF file on the forums for building instructions. I decide to go ahead and build a 3D model from the PDF with my CAD program.

 

  While doing so I wonder if the angular and boxy  construction of the La Scala was more a reflection of then current construction capabilities or whether it was an actual decision based upon sound wave propagation. For example if the cabinet was made a bit bigger so the internal  corners could have  been rounded would not the sound waves find an easier exit?  Or how about the back was one machined piece as shown below? I figure I could easily do this as one piece on my Haas VF4 but it would have been a lot of work for Klipsch to try this. This deflector back piece would be a direct replacement for the standard La Scala cabinet.

 

  Or does the boxy angular surfaces help contain sound waves a bit and utilize the cabinet to make deeper bass? See the back inside view picture. This one piece would be a lot more solid and could also be glued fastened to the motor board for a much more ridgid construction.

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Edited by Dave A
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Dave,

 

A  number of people have experimented with adding corner reflectors, with varying results, they have to be the right size, the right angle and placed properly.

 

As a long time Product Manager, my observation is that Klipsch went with keeping it simple as much as possible and keeping the cost under control.

 

This is my updating of my LaScalas, I also posted links to lots of other threads that I thought were interesting.

 

https://community.klipsch.com/index.php?/topic/159419-lascala-update-upgrade/page-4

 

Thanks for posting the nice CAD drawings.

 

Forgot, there is some software that is free that many use called Horn Response that will aid you in your calculations for reflectors.

Edited by Bubo
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One of these days, I'm gonna have a big 3D printer and print me a pair of LaScalas.  :)

 

I like the idea of the smooth back. It would probably be a nice upgrade to the LSII. Those blocks could be extruded plastic and replace the wooden ones now. It would cost a few bucks more, but might be noticeably better. It might actually sound worse too.  Who knows?

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I was told about how Paul penny pinched to a ridiculous degree on simple pennies per item at times recently. Considering the cost of La Scalas and what was saved it was silly at times. I have no design software for audio but my thought was to build upon sizes from the existing La Scala and for the corners to not become a choke point where the volume of the opening would be lesser than the narrowest existing in the current design.

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That "corrected back" piece is  :emotion-45:.  It's a vibrating mass inside there, not flowing water.

 

What the OP speaks of has already been done, here: http://www.billfitzmaurice.com/DR280.html  and also here: http://www.danleysoundlabs.com/danley/wp-content/uploads/2012/04/SH-46-spec-sheet11.pdf

 

I wouldn't mistaken the simplicity of the La Scala's construction for simplicity in it's design.

Edited by Quiet_Hollow
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While doing so I wonder if the angular and boxy construction of the La Scala was more a reflection of then current construction capabilities or whether it was an actual decision based upon sound wave propagation.

 

I was asking the same question today, but about the Belle.  Of course the lascala would fall under the same category.  I could see why, you think of a couple of guys in a small work shop with out the tools and technology we have, how could they do some of this.  Anyways, I guess this is why we have seen the curved Lascala.  Have you seen the work that goes into one of those, there is no way they could keep the cost down.  Then there is the question, does it sound that much better? Does it make that much of a difference for the need to spend so much? Only time will tell.  I would like to build a curved Lascala or Belle, but only if there is some sort of evidence that it would be an improvement.  My thought was "if it was curved on the back side would it be more efficient?"  Quite hollow is probably correct with the fact its not flowing water, but rather the way it bounces around back there.

 

I like the drawings along with the thought process.

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Went to the two sites you reference and I see nothing there like what I posted.  Now are you suggesting that klipsch made analytical decisions here based upon various configurations to get the very best or was a certain level satisfactory and he went with that?

 

  In so far as vibration goes this is a one piece milled from solid thing and if glued and fastened to the back of the motor board is far more ridging than existing and far less prone to vibration is my opinion. What do you base your vibration comment on?

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While doing so I wonder if the angular and boxy construction of the La Scala was more a reflection of then current construction capabilities or whether it was an actual decision based upon sound wave propagation.

 

I was asking the same question today, but about the Belle.  Of course the lascala would fall under the same category.  I could see why, you think of a couple of guys in a small work shop with out the tools and technology we have, how could they do some of this.  Anyways, I guess this is why we have seen the curved Lascala.  Have you seen the work that goes into one of those, there is no way they could keep the cost down.  Then there is the question, does it sound that much better? Does it make that much of a difference for the need to spend so much? Only time will tell.  I would like to build a curved Lascala or Belle, but only if there is some sort of evidence that it would be an improvement.  My thought was "if it was curved on the back side would it be more efficient?"  Quite hollow is probably correct with the fact its not flowing water, but rather the way it bounces around back there.

 

I like the drawings along with the thought process.

 

  Now you are talking. I can accept that the angular surfaces could improve things. All I am asking is for definitive information based upon research done and not just opinions. With all the talk here about reinforcing making a noticeable difference in sound quality it seems as though the general consensus is things could be improved.  Reading things here is a bit tedious at times because it's like there is a contest between money spent equating to bragging rights over solid real definable improvements and best bang for the buck real life analysis. I want the real answers because cost is not a problem since I can do this myself on machinery I already own. I don't however want to just waste time.

 

  Like the hole size in the dog house for the woofer. Rectangular and pretty small to me all things considered so does restricting the sound create a deeper bass utilizing the vibration of deliberately restricted and angular square cornered refinements made of plywood?  Now throw in 1" plywood is supposed to sound better and there goes in part the vibration thing. See my problem here is that you can go round and round in circles trying to find the best answer.

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What had me guessing is after the corner bend there is no more expansion until the horn mouth.

 

Maybe this area could be more constructive somehow ?

 Me to. This is one of the things that had me thinking about why things were done and leaning towards good enough was good enough. An inside corner round of pretty generous size can be put in there like I have and not reduce the narrowest point at all. If sound does to some degree behave like the flow of most everything else  I would think getting the sound out with the least amount of feeding back upon itself through induced swirls and eddies would have to help improve the definition of the sound and make it less muddy so to speak.

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Went to the two sites you reference and I see nothing there like what I posted.

It's all in the wavelengths. All three designs have similar low frequency cutoffs, packaging, and sensitivity.  

Now are you suggesting that klipsch made analytical decisions here based upon various configurations to get the very best or was a certain level satisfactory and he went with that?

Acoustic problems take into account a lot of variables. There is no such thing as "the very best," even among products that would claim so.

 

See the Glossary of Symbols on pages 1 & 2 here: http://users.ece.gatech.edu/mleach/papers/HornPaper/HornPaper.pdf

What do you base your vibration comment on?

Applied acoustics. All the features of the bass bin are no finer than required for the intended pass band for instance.

I want the real answers because cost is not a problem since I can do this myself on machinery I already own. I don't however want to just waste time.

I'd recommend getting in touch with Greg Roberts at Volti and bounce some questions off him. The solution to a better performing La Scala is not a modified La Scala....it's entirely different design.

Edited by Quiet_Hollow
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Don't forget the La Scala's bass horn is a folded exponential horn that traps a column of air and couples it to the woofer diaphragm.  That column vibrates, but it doesn't flow air.  At such long wavelengths, the corners and edges are insignificant aberrations.  Adding corner reflectors in the back corners (like a Peavey FH-1) improves the high frequencies from 500 to 1000 Hz, shorter wavelengths. 

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I'd recommend getting in touch with Greg Roberts at Volti and bounce some questions off him. The solution to a better performing La Scala is not a modified La Scala....it's entirely different design.

 

 

Applied acoustics. All the features of the bass bin are no finer than required for the intended pass band for instance.

 

    OK that makes some sense but considering the huge variables in the various construction methods you referred me to this is not a finished science and what I proposed could make a difference. I will get in touch with Greg and thanks for the lead.

 

  What really started me wondering about all this were the kind of crude angular mods people have done where there was not much if any thought given to, once again thinking here that flow of sound can be in some ways similar to flow of gas, the aerodynamics of things. For instance a flat faced triangular corner piece would I figure bounce sound back at a 45 degree angle which would throw it right into the side of the doghouse where as a radiused corner would tend to direct to the front of the cabinet.

 

  Does anyone know how the size of the cutout for the motor board was arrived at?

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Don't forget the La Scala's bass horn is a folded exponential horn that traps a column of air and couples it to the woofer diaphragm. That column vibrates, but it doesn't flow air. At such long wavelengths, the corners and edges are insignificant aberrations. Adding corner reflectors in the back corners (like a Peavey FH-1) improves the high frequencies from 500 to 1000 Hz, shorter wavelengths.

 

  I do understand this but have not yet had a answer as to whether sound waves can be directed just like an air flow could be. Direction of sound waves is what I am considering and air is just an analogy. Now if this never increased bass levels but improved sound quality over all this would still be worthwhile to me to try.

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The only time (~1975) I spoke with PWK I asked about the reason the Khorn, La Scala, Cornwall, et al tweeter and squawker horns were attached to the rear of 3/4 plywood rather than surface mounted (as they are today). His reply, "Doesn't make a dime's worth of difference."

Spoken like a good engineer. His comment implied that surface mounting was better, but not enough better to justify the expense. At least, that is what I inferred.

DIY affords one the opportunity to make those subtle changes that would be prohibitively expensive from a production standpoint. I'm amused at the attitude some here take when "improvements" are suggested for Klipsch products. Some feel that if it could have been done better, PWK would have done it that way. DIY improvements to Heritage are not hard. Whether they are worth the time and expense is a personal decision, but it's not heresy to build a better Heresy. It's not the same as suggesting that you could improve upon the Mona Lisa or Beethoven's 5th.

Edited by DizRotus
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Diz hit some good points.  I guess my final thought for this (today anyways) is. Why fix what isn't broken? I have to think back as I a typing this, of a fellow who has been around the audio industry for some time.  We discus back and forth if things could be better, he always seems to state that things are fine you feel they need to be better.   If the original design isn't good enough, maybe try to design a completely different bass bin that fits your needs.  Seems like alot of work to redesign something simple to make it more complex.  Let it be and start from scratch. 

 

For the record those last statements I maid are not directed towards the O.P. but more my thoughts to myself spoken out loud. 

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The only time (~1975) I spoke with PWK I asked about the reason the Khorn, La Scala, Cornwall, et al tweeter and squawker horns were attached to the rear of 3/4 plywood rather than surface mounted (as they are today). His reply, "Doesn't make a dime's worth of difference." Spoken like a good engineer.
K400 is truncated by design and the K77 operates under 60° in the vertical. That's why I don't fuss over surface mounting either.
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I have understood that higher frequencies don't very well follow the curved geometry you are proposing, whereas the angles actually reflect. It is hard to get higher freq. out of folded horns. The fewer folds the better.

Bruce

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