Hartley "boffle" improvement with CLD material

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#22
Maybe my question shouldn't focus too much on the "boffle" but more on the CLD element.

If the back wave has to travel through some kind of maze (later the shape and nature of this maze could be discussed....it could be chambers, straight, tapered, open, closed....) made up of CLD material walls (uniform or varied thickness/compliance) what would that do?

How much sound energy can it absorb? And in what frequencies? What would determine the absorption frequency range?

Instead of a boffle I could imagine a long tapered channel (b&w nautilus style) with CLD walls that is folded into a rigid box. The narrower the channel gets the thinner and more compliant the CLD wall gets.
 
#24
ErikNils said:
If the back wave has to travel through some kind of maze (later the shape and nature of this maze could be discussed....it could be chambers, straight, tapered, open, closed....) made up of CLD material walls (uniform or varied thickness/compliance) what would that do?
Click to expand...

The CLD is for building the box and to keep inside noises inside. The maze you describe was first implention i saw was in the Hegman One, the idea seen in a gestation in the Eico-Hegeman zz9more a quarter-wave variant) from the diagram.

eico-HFS90.jpg


Hegeman 1, i’d ever seen insides like it when i pulled the driver and stuck my head in …

666hegeman.promo_.jpg


https://www.stereophile.com/content/hegeman-model-1-omnidirectional-loudspeaker

dave
 
#26
Translation issues then ;^)

It is great to have so many members from all over the world, many who are members where Englsih is a mystery, but the translators have gotten good euff that they make it possible for them to converse. They are still somewhat primitive, but partcularily nuaces in the techncal field, They will get better, particularily when “AI” (=Idiot Savant) is woven in, they will get really good, but not before some bizarre translations (aka teething problems).

What is probably a worthwhile pursuit would be to explore the properties of layers of dampimg sandwiched together, combined with exploring where the air space resonances are you want to kill, and maximizxing LF affects in the host box.

dave
 
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#27
Also need to metion there was a Seaker Builder with an article on a simple LF “meta” structure with the basic math.

To apply to the maze of varying length & cross-section quartre-wave pipes out the back, and damping is an intriging idea. A side effectwould be a really ridgid "box”.

Have fun.

dave
 
#29
ErikNils said:
If the back wave has to travel through some kind of maze (later the shape and nature of this maze could be discussed....it could be chambers, straight, tapered, open, closed....) made up of CLD material walls (uniform or varied thickness/compliance) what would that do?
Click to expand...
Largely the same kind of thing as a stuffed box.. if you can manage the line.

Unless you are trying to lower the reasonance Q, there is no need to remove the driver back wave if it isn't modal. The boost in resonance Q is harmless as long as it's the response you need.
 
#30
ErikNils said:
My question is this, wouldn't it be better to use CLD material (constrained layer damping) in stead of felt curtains......or CLD material covered in felt?
Click to expand...
No it has to be "transparent", in original they used that brownish felt ro packaging vacuum tubes.
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Please take a look to another same design by Philips.
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I made one box long time ago in that concept, working fine, a much better than empty U-frame.
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Cheers
 
#35
ErikNils said:
Does it just reduce unwanted resonances or does it also support bass output compared to a uframe?
Click to expand...
If it is made as frames with felt on the sides, which are in contact to the walls - Yes. Like it is on the plan from hartley. Frames has double role, to made felt contact suface and damp walls slightly, and first role is to make same distance for rounded felt holes...
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It is not primarly connected with bass since that is small distances and areas, but more to the lowmid and central BW - somehow make it more clear. Without felts it is somehow "muddy"...
 
#36
The key point for hartley patent is that material has to be semi transparent. And rigid in the same time to mantaint straight areas withut bendind as much as can be.
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So my tip for best experimental construction is:
Make frames but smaller than inside frame dimensions. Count in the space from brace to wall to be fit 2-3 thin felt material usualy 2mm when pressured. AND alu thin mesh to carry on the felts and to form straight surface.
Frames widh calculate for same distance between the felts...
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Then cut out the different diameters in felts and attach it to the frames with aluminium mesh.
You can put one or more synthetic felt sheets. It ias easy to find that in the stores.
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Philips noted about the name for matherial they used in PHI plans, I dont know it by hearth now, but I am sure that is noted. On the other hand I think that is obsolete, because I tried to find when I made mine... 🙁
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Anyway it is almost a must for open bafle U or H frames. And I am pretty sure that can be used in expanded form
of Mesh Potato sound disperser for OB. In front and behind the central speaker. 🙂
 
#37
On the contrary, muddiness is what we need, just before annihilation, but that's not actually doable because 20Hz/17 m wave length has the prerogative to be omni directional so any hole will be an 'escape room'!

Quoted from post #35
"Frames has double role, to made felt contact surface and damp walls slightly, and first role is to make same distance for rounded felt holes...
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It is not primarily connected with bass since that is small distances and areas, but more to the lowmid and central BW - somehow make it more clear. Without felts it is somehow "muddy"
 
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