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Pilgrimage 2019 Chief Bonehead chats: LaScala/Jubes

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34 minutes ago, Edgar said:

 

I wish that I could find the article, but someone summed it up concisely in the past:

 

All panels resonate. Some more than others, but they all resonate. For woofers, you want the enclosure walls to be as stiff as possible, so that their resonant frequencies are above the frequency range of the woofer. For midranges, you want the enclosure walls to be "floppy", so that their resonant frequencies are below the frequency range of the midrange. In all cases, you want them to be well-damped.

Makes perfect sense. 

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16 hours ago, PrestonTom said:

I am sorry this thread  has degenerated into a MDF vs Plywood debate, There are plenty of them over at DIYaudio. 

None of them are interesting,

 

 

Why are you sorry for anything. You didn't get sucked in like I did. But thanks for pointing this out. Seriously.

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27 minutes ago, ClaudeJ1 said:

Why are you sorry for anything. You didn't get sucked in like I did. But thanks for pointing this out. Seriously.

 

In the end both sides become entrenched in these long winded & heated arguments. The information ends up being rather sparse and scattered. 

 

The only nuggets information are: 1) MDF has more mass/density and some internal dampening with  is good for reducing low frequency vibration 2) plywood has stiffness which is good for higher frequency vibration 3) the most critical surface to reduce in its vibration is the baffle (where the woofer is mounted). This is best done using bracing (in fact with adequate bracing the cabinet's material does not matter nearly as much). Bracing is where your time and effort should go. 

 

Okay, in between the nuggets of info are usually at least 20 - 100 pages of back and forth of attacks and silliness. 

 

IN my upcoming build, the baffle will actually be about 1.25 - 1.5 inches thick  and created as a sandwich of materials with some constrained layer dampening in between. The bracing will be like that shown in JBL M2 and S-4700 cabinets. 

 

Claude, how did you snare me into this? 

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1 hour ago, PrestonTom said:

Claude, how did you snare me into this? 

Not sure. But at least you provided some useful technique to think about. My super Cornwall has added bracing.

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On 7/24/2019 at 6:25 AM, Edgar said:

All panels resonate. Some more than others, but they all resonate. For woofers, you want the enclosure walls to be as stiff as possible, so that their resonant frequencies are above the frequency range of the woofer. For midranges, you want the enclosure walls to be "floppy", so that their resonant frequencies are below the frequency range of the midrange. In all cases, you want them to be well-damped.

It is revealing when you are sanding off various cabinets the degree of resonance a simple orbital sander creates. I have wondered if it is worthwhile to try and eliminate as much of this as you can or tune the wood used to the drivers in question. 25mm Baltic Birch is an attempt to do both without using additional bracing and seems to be in general a good solution.

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19 hours ago, PrestonTom said:

IN my upcoming build, the baffle will actually be about 1.25 - 1.5 inches thick  and created as a sandwich of materials with some constrained layer dampening in between. The bracing will be like that shown in JBL M2 and S-4700 cabinets. 

 

Claude, how did you snare me into this? 

Hmmm sounds like the snare was some time ago😀 What exactly are you using in your baffle and why are you choosing it?

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Since everybody got totally off-topic, except the ones who erroneously ASSUMED that the ultra-deluxe Jubilee would be JUST a cosmetic enhancement thing...let me throw this out for perusal:

 

1. The current Jubilee bass bin construction for its "double-S-Horn" design is constructed of numerous relatively narrow strips...with each long edge of each strip cut at different angles to achieve the "curvature" of the "S" horns, beginning at the bifurcation point.  This is the horn interior that is unseen in the final product.

 

2. By having a number of small angles involved, as the horn curves back and forth, the bends are accomplished, but not AS SMOOTHLY accomplished as COULD BE DONE, IF those bends were actually SMOOTH CURVES, INSTEAD of a bunch of multiple angles TRYING to SIMULATE a "smooth curve"...make sense??

 

3.  There are a number of ways to actually build the bass bins with GENUINE smooth curves, but the cost is much more exorbitant!...and the medium can be very expensive...such as actually laying up plies together on a hot press form or set of forms to create plywood which is curved...such as how they laid up the plywood for the Dehavilland Mosquito aircraft fuselage during WWII!....OR something called "liquid wood" could be used...or "stack-building" could be used...or a number of other techniques to attain GENUINE CURVES for those two "S" horns!  The closer to the bifurcation point those "S" horns are, the tighter the curves are at the bends....keep that in mind.

 

4.  Due to the EXCESSIVE COST of making REAL CURVES, the price of the ultra-deluxe version would be much higher, if that were to be one of the goals...make sense??  OF COURSE, it would be much more likely to be more eye-appealing in its exterior accoutrements, also!

 

Once again, let the conjecture ensue!

 

There is/was a speaker company in Australia??….which stack-built modern replicas of the JBL Hartsfield version II bass bin (a complete re-design of the original Hartsfield bass bins, converting the bass bin to a double "S" horn)...and other classic horn speakers...at one time!

 

See the attached JBL Hartsfield Version II plans and note the top view (center top) of the bends in its bifurcated double "S" horn design...and think about it for awhile...LOL!  There are some similarities between this design and the bass bin of the Jubilee.

1750323617_HartsfieldIIplans.jpg.66435408e90f49a2f2c3c865f301e1c4.jpg

 

 

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On 8/11/2019 at 8:22 PM, HDBRbuilder said:

2. By having a number of small angles involved, as the horn curves back and forth, the bends are accomplished, but not AS SMOOTHLY accomplished as COULD BE DONE, IF those bends were actually SMOOTH CURVES, INSTEAD of a bunch of multiple angles TRYING to SIMULATE a "smooth curve"...make sense??

 

For wave phenomena, "smooth" is defined relative to wavelength. In cases where the physical dimensions are smaller than approximately ¼-½ wavelength (like the interior of a Jubilee or Klipschorn at 40 Hz), the angles and bumps and protrusions are of no significance whatsoever because the sound waves don't even notice them. In cases where the dimensions are larger than approximately ¼-½ wavelength (like the interior of a Jubilee or Klipschorn at 400 Hz), use of corner reflectors is entirely appropriate and very effective. In fact, in the latter case, "smooth" curves can actually lead to path length differences and notches in the frequency response due to cancellation.

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6 hours ago, Edgar said:

 

For wave phenomena, "smooth" is defined relative to wavelength. In cases where the physical dimensions are smaller than approximately ¼-½ wavelength (like the interior of a Jubilee or Klipschorn at 40 Hz), the angles and bumps and protrusions are of no significance whatsoever because the sound waves don't even notice them. In cases where the dimensions are larger than approximately ¼-½ wavelength (like the interior of a Jubilee or Klipschorn at 400 Hz), use of corner reflectors is entirely appropriate and very effective. In fact, in the latter case, "smooth" curves can actually lead to path length differences and notches in the frequency response due to cancellation.

We will just have to see what happens, won't we??

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HDBRbuilder,

which of the techniques you described was used to fabricate the Palladium speakers?

It seems likely Klipsch would use the method they have already perfected and have experience with.

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20 hours ago, Bill W. said:

HDBRbuilder,

which of the techniques you described was used to fabricate the Palladium speakers?

It seems likely Klipsch would use the method they have already perfected and have experience with.

I know absolutely NOTHING about the build of the Palladium speakers.  But they DO NOT have an INTERIOR complexity that a double-"S" horn would have...that's for sure!

 

Here is what I DO KNOW about stack-building, though:

 

With CNC equipment doing the cutting, the medium used can be single panels which are glued up and stacked atop each other using an alignment tool, such as steel dowels (rods) thru  snug holes in each layer. With the entire structure being clamped while the glue sets up. For a DIY application, router forms can be used, if no CNC is available. 

 

For changes to the shape within the structure on the vertical axis, CNC cutting would be much more conducive to efficiency of completing the parts, but in the DIY process this could STILL be accomplished using router forms, which are SPECIFICALLY for certain layers within the stack.  For panels within the structure which will be required to have their main plane on the vertical axis (such as motorboards, etc.), the panels which are stacked must allow for a smooth glue surface on the edges to ensure a good airtight bond to each other....with the possible requirement of glue blocks being used for reinforcement.

 

A DIY application of stack building would BEST be accomplished having everything computer-modelled PRIOR TO the making of the router forms....unless a CNC cutting device is available and properly programmed.

 

Equipment best used for stack-building in the DIY mode without CNC available would be to have on hand a good large diameter disc sander, and a good oscillating drum sander, ESPECIALLY for using a medium such as Baltic birch plywood.

 

Basically, the DIY method would require smoothing out the curves from the original plans design, which may require some adjustments, which is akin to POSSIBLY requiring the equivalent of multiple "prototype" constructions to fine-tune everything.  BUT, for PRODUCTION purposes using CNC equipment, the requirement would only involve adjustments to the program used to achieve the same results. IOW, test the prototype, then use the program to make the adjustments needed, which SHOULD NOT require very many re-builds to get what is desired.  ALSO, the additional advantage is that other improvements could be figured into the program, itself!

 

No matter how one looks at stack-building a complex horn design, it takes time to "get things right"...but once they are good to go, it is a done deal if using CNC processes....along with computer-modelling.  The major drawback COULD BE in just insuring consistent thickness properties of the medium being cut to be stacked.  My medium of choice would be Baltic birch panels because they would be "better" at being glued-up for stacking than MDF ever could be...which would put serious thickness consistency into the picture.

 

I am a long ways away from trying this out, though, myself....I still have to move and set-up my wood-working shop for my retirement home construction before I do any more speaker-building.  By the time I get the retirement home done, I should have the computer training I need to model things very close to the desired results for something like a Jube bass bin.  Being over 65 years old is a boon for me because I can take free college courses thru the University of Arkansas Engineering department to aquire the skills I need in computer-modelling.  Until then, I can play around with La Scala-building (incorporating some ideas I have for that) and such!

 

Since I am sure SOMEBODY is curious, so here ya go for ONE of my La Scala ideas:  One of my La Scala ideas is to have a rotating HF section using a "lazy Susan" turn-style which is loaded with nylon bearings and can be locked-in-place.  Nylon roller or ball bearings would eliminate any rattling from the lazy susan when it is tension-locked into position! That way the bass bin can be ideally situated in the room corner, while the HF section can still be better "aimed" towards the ideal "sweet spot" listening location.  This would also allow for inclusion of a limited ability for the HF section to also be rotated slightly upwards or downwards on its vertical axis using an additional locking unit in the construction.  The collar between the HF section and the Bass bin could easily hide the devices used for this.  

 

Keep in mind that I was once a pattern-maker...so I have had to deal with stack-building in the most difficult of situations when making pattern-masters.  I also had to build core-box masters!...some of which were very complex units requiring removable  "locking" inserts so that the core boxes could actually be packed properly with the core sand.  I consider myself very lucky in that I have some weird kind of ability to conceptualize in 3D...LOL!  If you want to call THAT "lucky".  It sure was handy when making pattern-masters and complex core boxes, though!😉

 

 

 

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On 8/16/2019 at 3:25 PM, Khornukopia said:

 

Please tell us more.

Not much more to tell....all I have about it is hints from others...it may never even happen.

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HDBRbuilder just curious to know what you think true radiused corners would bring to the table. I have modeled this with the La Scala from the motorboard to the back side with all radiused corners and wonder what if anything it would do.

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12 hours ago, Dave A said:

HDBRbuilder just curious to know what you think true radiused corners would bring to the table. I have modeled this with the La Scala from the motorboard to the back side with all radiused corners and wonder what if anything it would do.

I dunno...but I have heard (from somebody who SHOULD KNOW!) that there WILL be improvement...but you are also comparing apples to oranges...the K-horn and La Scala have radical 90 degree bends, whereas the Jubilee has much gentler bends...My best analogy for this might equate to the following:  Have you ever seen a tuba, French horn, etc.whose horn body was a number of flat panels joined together to create the horn, itself??

 

A number of people have incorporated panels into the vertical corners of the La Scala bass bins they have built, and have noted an improvement in what they HEAR...but is it MEASURABLE??

 

Also KEEP THIS IN MIND:  PWK was a HORN-PLAYING musician, in case you are unaware of this. 

 

In the bi-furcated double "S" horn design of the Jubilee bass horn, the gentler bends using flat panels much-more approximate a smooth curve to begin with...than the K-horn bass bin lens does...so why not "go all-out" on a TOTALLY smoothly-curved version??

 

Some people have/will point out that it is really unnecessary, and the improvement will/may only relate to the higher frequencies the bass horn produces, but any improvement at all is still an improvement, isn't it??  Isn't that the goal?  IMPROVEMENT?  With ANY improvement, combined with the electronic equalizer/crossover, wouldn't the results be justified?

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Here is a back section that has all rounds I have pondered doing out of stacked Baltic Birch plywood.

La Scala one piece back.JPG

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... o O (is there a bigger drawing available, where this goes? or moreover, what it is)

 

the back section of a LS, being rear firing, back around to the front, nevertheless, creates the confusion seeing the above illustration... although I think my interpretation is relative to the beginnings, and continuing forward, in a round about way... not that it is confusing in such a matter relative to the original replacement area being worked on, but such as it might need more stacked and shaved, routered and a beveled sound wave channel , the figure of 13.038" baffles my observation, because it's close to the size of the woofer port

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... o O (Thursday Morning Pondering)

 

1.5859 vs 1.7065 averaging 1.6462

 

 

golden-section-golden-ratio-divine.jpg

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Good Morning windashine.  This is based on the actual construction and volume of the La Scala so yes it is the exact size of the woofer port measured by me. The rest of it is simply rounding corners making sure that the volume of the passages does not shrink at the corners. I have been told sound is not like water where sharp corners create turbulence, which would equate to muddier sound in those same circumstances in my thinking, but somehow I keep coming back to this idea. Klipsch finally put those K-77's to be flush with the front of the motorboard and those older K-77's all had sharp corners and overlap where the cutout was and it had to hurt sound quality or else why change it? So I am back to pondering this idea of helping sound "flow" through the restricted area at the backside of the La Scalas. Extra depth here will not help if I don't make the space between the dog house and sides where they are parallel since it is supposed to be ever expanding or at the least no reduced area points for sound to go through. At the very least this increase on contact area and dampening mass would have to help fight resonance.

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