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Dave A

La Scala Bass Bin Mid Brace

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2 hours ago, DizRotus said:

 

Now you’ve really piqued my curiosity.

Bet it was a JDM comment. Maybe he wants us to invite him over here.

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3 hours ago, codewritinfool said:

They wouldn't have to be offset so much you could detect it by eye.  Just a tiny bit would serve to avoid making a 2nd harmonic resonance point.

 

Of course, this assumes a few things....

 

1. That I know what I'm talking about.  I don't, necessarily, but it's just physics and seems logical to me.

2. That the resonating point is the side wall.

 

You'll have to wait for someone that knows what they're doing to chime in.

 

BTW, I think I need some of those beautiful braces for my splits!

You know how to find me, we could bang those out in no time. We could use Dave's drawing for starters and tweak. Maybe cut out of cardboard first.

Throw your splits and THTLP into your hybrid and head over.

Maybe make a couple sets for mine too.

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a centrally mounted brace (or there abouts) should easily push the panel resonant mode above the pass band of the driver. the panel can only resonate if the driver can set it (the panel) into resonance so once the first resonance mode is braced to above above the driver pass band it no longer matters the panel can no longer be driven into any resonance. So folks are making something out of nothing. The problem has been solved yet they are still looking for a new non existent problem to solve.

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55 minutes ago, MookieStl said:

You know how to find me, we could bang those out in no time. We could use Dave's drawing for starters and tweak. Maybe cut out of cardboard first.

Throw your splits and THTLP into your hybrid and head over.

Maybe make a couple sets for mine too.

You drive a hard bargain.  Maybe J and I could load up everything in his truck - my hybrid is a sedan!  No way anything but the tops would fit into that thing.

Let's plan something - maybe some music and some beer too.  

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35 minutes ago, codewritinfool said:

You drive a hard bargain.  Maybe J and I could load up everything in his truck - my hybrid is a sedan!  No way anything but the tops would fit into that thing.

Let's plan something - maybe some music and some beer too.  

Now this is why I posted the drawing so it could become DIY. I can't advise anyone on gluing to lacquer or varnish or paint though. The ones I had were painted and since I am going to duratex them sanding to bare wood was not a problem.

 

  Now I have a question for you woodworking wizards. If I had a nice set I wanted to add these to but not sand the sides or doghouse where the brace will go what surface treatment and glue would work here? I figure I can coat the braces to suit except for the edges that will be glued to save

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Precisely at what point... db... do you think this becomes even remotely audible and more importantly beneficial and an improvement to the original design?

 

It's somewhat a case of Irony that the example of a guitar was used... the best guitars are designed and braced in a fashion where there is as LITTLE material and BRACING used in order to facilitate flex and volume.

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The difference between sound production and sound reproduction, maybe?

 

I'm thinking if there's a frequency a panel will sing along with, that at half that frequency there'll be at least a little humming.  I'm sure smack dab in the middle is fine.  I'd offset a smidgen.

 

Dave, I think I'd probably draw some lines a bit narrower together than the thickness of the brace and remove the finish within that area.

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11 hours ago, Schu said:

Precisely at what point... db... do you think this becomes even remotely audible and more importantly beneficial and an improvement to the original design?

 

It's somewhat a case of Irony that the example of a guitar was used... the best guitars are designed and braced in a fashion where there is as LITTLE material and BRACING used in order to facilitate flex and volume.

removing structural cabinet resonance(s) is always going to be audible and beneficial and in horns bracing the mouth is especially important the lower and louder you want the horn to play the more you need to do this. This does not mean owners have to do any of this. If the owner is happy with things as they are then leave well enough alone. Depending upon the application of a design or the physical/monetary constraints of the design a designer may or may not include brace work especially in domestic situations where brace work is not seen and makes the cabinet larger weigh more and cost more and the end user will probably never push the cabinet hard enough to expose the problems that bracing would address in the first place.

Instruments and instrument loudspeakers are designed and intended to have structural resonances which enhance and compliment the instrument played through them monitors and PA loudspeakers are intended to reproduce as exactly as possible the sound of the instrument and are not intended to add any sound quality of their own. The difference in the two applications should be obvious to any interested in audio but very often we see home audio designers fudge a loudspeaker to cater to market taste and often this approach works for them.

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12 hours ago, Schu said:

Precisely at what point... db... do you think this becomes even remotely audible and more importantly beneficial and an improvement to the original design?

 

It's somewhat a case of Irony that the example of a guitar was used... the best guitars are designed and braced in a fashion where there is as LITTLE material and BRACING used in order to facilitate flex and volume.

For me as measured around 80db on certain songs. At louder volumes the perception of deeper bass is pretty amazing when you realize you can now hear what was always there but hidden by cabinet resonance.

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10 hours ago, glens said:

Dave, I think I'd probably draw some lines a bit narrower together than the thickness of the brace and remove the finish within that area.

That would work. I will be trying that one out soon.

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12 hours ago, Dave A said:

Now this is why I posted the drawing so it could become DIY. I can't advise anyone on gluing to lacquer or varnish or paint though. The ones I had were painted and since I am going to duratex them sanding to bare wood was not a problem.

 

  Now I have a question for you woodworking wizards. If I had a nice set I wanted to add these to but not sand the sides or doghouse where the brace will go what surface treatment and glue would work here? I figure I can coat the braces to suit except for the edges that will be glued to save

If you get a glue to adhere to the current finish the bond will be as strong as the current finish to cabinet is.  I would hold the brace in place, trace both sides then scrape the area inside the silhuoette and use the appropriate glue.  I've given this some thought as I'm going to brace my LSI's when I rebuild them.  I'll probably use pocket screws as well.

 

EDIT, glen beat me to it.

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1 minute ago, CECAA850 said:

If you get a glue to adhere to the current finish the bond will be as strong as the current finish to cabinet is.  I would hold the brace in place, trace both sides then scrape the area inside the silhuoette and use the appropriate glue.  I've given this some thought as I'm going to brace my LSI's when I rebuild them.  I'll probably use pocket screws as well.

Considering how dry and flaky varnish, or lacquer or whatever that older clear finish is that is not a good thing. I can often take a razor blade and easily remove small areas. Sometimes I think that might be from poor storage environments like to much humidity or storage units that go from 0 to 140 degrees temp over the year.

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1 minute ago, Dave A said:

Considering how dry and flaky varnish, or lacquer or whatever that older clear finish is that is not a good thing. I can often take a razor blade and easily remove small areas. Sometimes I think that might be from poor storage environments like to much humidity or storage units that go from 0 to 140 degrees temp over the year.

Paint, varnish or whatever.  I'd find bare wood to adhere to.  I think we're all in agreement.

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Same concept with replacement glue-down floor covering.  The new glue will only be as "stuck" as is whatever it's stuck to underneath it..  What's more, sometimes the new glue and (remnants of the) old are chemically incompatible, in cases making a gooey mess that neither sticks nor cures.  Fun times...

 

And sometimes brand new construction isn't really ready when told it is.  Preparation is the key to success.

 

I just now had an idea for this task.  One could fashion guideways for a small router to make (even shallow) dados.  They needn't run the full length of the brace, and the guideway could be fastened to the panel with a couple of screws which holes-for lie in the area which will be covered later by un-dado'd brace (just a bit, on the ends).  I could "sketch up" (crudely) what I'm talking about if the notion isn't clear-enoughly described.  Dados of any length and depth would do wonders for structural purposes, and can aid in final appearance, too.  Any sin that can be hidden is good sin. 

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13 minutes ago, glens said:

Any sin that can be hidden is good sin. 

I love quoting out of context.....It reminded me of a song

 

Captain Beefheart, Electricity.

 

Singin through you to me
Thunderbolts caught easily
Shouts the truth peacefully
Electricity
High  voltage man kisses night to bring the light to those who need to hide their shadow deed
Go into bright find the light and know that friends don't mind just how you grow 
Midnight cowboy stained in black reads dark roads without a map
To free selectricity (repeat) (Repeat both lines) 
Lighthouse beacon straight ahead straight ahead across black seas to bring
Seeking electricity
High voltage man kisses night to bring the light to those who need to hide their shadow-deed hide their shadow-deed (repeat) 
Seek electricity
Electricity

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Here is the LSI set with braces and all that lovely Duratex.

DSC_0014.JPG

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Here is the LSI set with braces and all that lovely Duratex.
DSC_0014.thumb.JPG.f1721a18613e7dd793f6e3b9bb6623b3.JPG


That is cool. I plan to do that too. I’ll post pics when I do.

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Really killed the sidewall resonance. I still have some weird things going on but when I run a DBX driverack eq with pink noise it goes away. I don't like the sound as it gets a little muddy but it tells me that I should be able to solve this with a DBX EQ thingy which can then be sold on with the LSI's. I guess these La Scalas are famous for a hump somewhere and I will have to look around for that info. This set has given me fits from self induce stupidity to frequency problems I am not used to having. At least I can see the way to solve it now.

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7 hours ago, Dave A said:

I guess these La Scalas are famous for a hump somewhere and I will have to look around for that info.

 

170 Hz?

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EDIT 9/7/19 @ 08:47 EDT

 

I see this photo was posted earlier.  It’s comforting to see hat PWK’s lab was no neater than my workspace.

 

 

@pzannucci noticed the braces in the attached photo @HDBRbuilder posted in the thread about the new H4.  Clearly PWK was aware of the sidewall resonance issue and braces as a possible solution.  Notice they are not vertically centered.

 

49BD074E-51C6-429D-BD4E-4862C0C78971.jpeg

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