Is it possible to cover the whole spectrum, high SPL, low distortion with a 2-way?

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#12,941
Heres the response with 2pi I messed up delivered 0.5Pi sims earlier.

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#12,942
Hello Camplo

Never used Horn Response so I am not familiar with it. Why do you have a saw tooth displacement?? Just seems odd compared to other sims I have used.

Is that a property of using slot loading which again I have never used??

With bass reflex you get a null at port tuning it seems you are getting multiple nulls over a couple of octaves??

Rob 🙂
 
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#12,943
AIU

So, a sheet that is 4 feet by 8 feet and 1/4 inch thick has a volume of 288 cubic inches.
The amount is approximately $0.3277 per cubic inch at 3/4"

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The total volume of the sheet is 1296 cubic inches.
The amount is approximately $0.7731 per cubic inch.
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one gallon is equal to 231 cubic inches.
The amount is approximately $0.2019 per cubic inch.

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A quantity of 50 lbs of thin-set mortar would equate to approximately 864 cubic inches when spread out at a quarter-inch thickness.
The amount is approximately $0.0115 per cubic inch.
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A quantity of 60 lbs of sand would equate to approximately 1036.8 cubic inches when spread out at a quarter-inch thickness.
The amount is approximately $0.00461 per cubic inch.
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Baltic Birch Plywood (Generalized Data)​

  • Tensile Strength:
    • Parallel to Grain: 30 - 50 MPa
    • Perpendicular to Grain: Lower than parallel, specific value varies
  • Compressive Strength: Typically similar to tensile strength due to the cross-laminated structure
  • Shear Strength: Varies but generally high due to layered construction; shear strength is also affected by grain direction
  • Impact Strength (Toughness): Good resistance to sudden impacts; more resilient than many other wood products
  • Fatigue Strength: Good fatigue resistance, especially in applications with cyclic loading where the grain orientation can be advantageous
  • Elastic Modulus (Young's Modulus):
    • Parallel to Grain: Approximately 10 - 17 GPa
    • Perpendicular to Grain: Significantly lower than parallel, specific value varies

Epoxy Resin (Generalized Data)​

  • Tensile Strength: 40 - 80 MPa
  • Compressive Strength: 70 - 140 MPa
  • Shear Strength: ~55 MPa
  • Impact Strength (Toughness): Varies; some epoxies are more flexible or toughened.
  • Fatigue Strength: Good fatigue resistance but dependent on formulation.
  • Elastic Modulus (Young's Modulus): Typically around 3 - 4 GPa

Soda-Lime Glass (Generalized Data)​

  • Tensile Strength: 33 - 55 MPa
  • Compressive Strength: ~1000 MPa
  • Shear Strength: Not typically specified due to brittle nature.
  • Impact Strength (Toughness): Brittle fracture behavior under impact loading; tempered versions have higher resistance.
  • Fatigue Strength: Sensitive to flaws, can fail suddenly when subjected to stress over time.
  • Elastic Modulus (Young's Modulus): Approximately 50 - 90 GPa

Cement Mortar (Generalized Data)​

  • Tensile Strength: ~2 - 5 MPa
  • Compressive Strength: ~30 - 50 MPa
  • Shear Strength: Not typically specified; generally lower than tensile or compressive strengths due to the brittle nature of cementitious materials.
  • Impact Strength (Toughness): Generally low, as mortar is brittle and prone to cracking under impact loads.
  • Fatigue Strength: Limited data available; not usually a major design criterion for mortar due to its brittleness and more common concerns with long-term durability rather than cyclic loading.
  • Elastic Modulus (Young's Modulus): Approximately 15 - 35 GPa

ABS Plastic (Acrylonitrile Butadiene Styrene) - Generalized Data​

  • Tensile Strength: 27 - 52 MPa
  • Compressive Strength: ~80 MPa
  • Shear Strength: Not typically specified, but generally lower than tensile strength.
  • Impact Strength (Toughness): High; ABS is known for its toughness and resilience to impact.
  • Fatigue Strength: Good fatigue resistance; suitable for applications with cyclic loading.
  • Elastic Modulus (Young's Modulus): Approximately 2.0 - 3.1 GPa

PETG Plastic (Polyethylene Terephthalate Glycol-modified) - Generalized Data​

  • Tensile Strength: 50 - 75 MPa
  • Compressive Strength: Similar to tensile strength or slightly higher due to the amorphous nature of the material.
  • Shear Strength: Not commonly specified as it is not typically a design-limiting factor for this material.
  • Impact Strength (Toughness): Very high; PETG is recognized for excellent toughness and durability against impacts.
  • Fatigue Strength: Reasonable fatigue resistance but can be sensitive to stress concentrations over time under cyclic loads.
  • Elastic Modulus (Young's Modulus): Approximately 2.0 – 2.7 GPa

Aluminum (Generalized Data for Common Alloys)​

  • Tensile Strength:
    • Pure Aluminum (1xxx series): 90 - 140 MPa
    • Alloyed (e.g., 6061, a common structural alloy): 240 - 310 MPa
  • Compressive Strength: Similar to tensile strength in most aluminum alloys.
  • Shear Strength:
    • Pure Aluminum: ~55 MPa
    • Alloyed (e.g., 6061): ~150 MPa
  • Impact Strength (Toughness): Generally good, but varies with temper and specific alloy. Heat-treated alloys can be more brittle.
  • Fatigue Strength: Varies widely based on the alloy and heat treatment; some alloys are specifically designed for improved fatigue resistance.
  • Elastic Modulus (Young's Modulus):
    • Approximately between (68.9) and (71) GPa across various aluminum alloys.


This information is estimates from AI, so take with a grain a salt, or investigate further to be sure. Basically what I see is that I can beat Baltic Birch, Usd/Cubic Inch. 1Part Resin Epoxy to 5PartsSand is a common recipe. I assume that sand has the strength character similar to glass. Sand Mortar should be stronger than wood, matching thickness and cost much less per square foot.

Build a frame out of....not sure yet... and place fabric on frame...paint with Resin, let cure, then apply Sand Mortar.
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The actual woofer baffle would appreciate a solid beginning maybe this?
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With enough bracing a proper enclosure could be made and I don't think it would be that hard.
 
#12,945
Robh3606 said:
With bass reflex you get a null at port tuning it seems you are getting multiple nulls over a couple of octaves??
Click to expand...

I messed up yesterday but I found my mistakes.
This is not an exact simulation, I made the mouth larger in my simulation by ~1000 cm2
I used my 18h+ in the sims
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What I wanted to be sure of, is that a large woofer could play in such a horn. Bill Fitz claims that large diaphragm woofers don't survive in these things... If Driven hard enough, any woofer will have issue, it seems the PA Paraflex guys definitely have platform to destroy drivers, and it is spoken that certain drivers are tougher than others. Any way, thinking of Bills words I thought to seek out some details. This same volume BR with a large port does not reach as high pressure as the FLH. SPl is Port only since pressure exist mostly at tuning for our interest.
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because I simulated in the wrong setting my ideas of efficiency were way off. Its easy to see now that pressure does get high for the FLH. Reducing CSA about 400cm2 didn't change too much. Guess a smaller sized port would eventually get small enough to start bringing up pressure. But Who knows how much pressure tis too much anyway.

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A
 
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#12,946
Flaesh said:
Where is this cute picture from?
Click to expand...
https://mapoulin.wixsite.com/audiobymartin/montreal-house-2021
daqvin_carter said:
Some may be tempted to use cotton or foam as room treatment or cabinet treatment.
Consider your exits carefully. Fiberglass wins as long as you keep it out of your lungs.
https://en.wikipedia.org/wiki/The_Station_nightclub_fire
Click to expand...
I watched a video of someone inside the nightclub and escaped... Point made... In the process searching, somehow I found the above website
 
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#12,949
AI says
  • The approximate mass of 100 cubic inches of Baltic birch plywood is about 2. 46 pounds.
  • The approximate mass of 100 cubic inches of sand is about 5. 81 pounds.
It seems that one could use the sand/epoxy mortar at half the thickness you would use wood. Combine that with a bracing plan, and you have a recipe for success.
Using fabric as a mold is one thing... One could go down to the rubber store and get some sheets to silicon to create molds to create panels of Sand Mortar. Epoxy and Cement wont stick to it.

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#12,952
I have been using epoxy as a substitute for glass in some projects. It can be poured into a mold to make sheets of any color and thickness. It can be cut the same as wood. Rather than use sand, I would use 3M glass beads. Just as strong but much much lighter. When cured the epoxy sheets are virtually unbreakable.
 
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#12,954
PVA Glue (Generalized Data)
  • Tensile Strength: 15 - 30 MPa (for wood-to-wood bonds)
  • Compressive Strength: Not typically characterized due to application nature.
  • Shear Strength: ~10 - 20 MPa (depending on substrates and conditions)
  • Impact Strength (Toughness): Moderate; PVA is somewhat flexible when cured, which can absorb impacts.
  • Fatigue Strength: Good for cyclic loading in typical household applications but not suitable for high-stress engineering applications.
  • Elastic Modulus (Young's Modulus): Typically around 0.5 - 1.5 GPa
 
#12,956

Soda-Lime Glass​

  • Sound Absorption Coefficient: Very low; glass is not effective at absorbing sound and is mostly reflective.
  • STC Rating: Typically ranges from 30 to 35 for single-pane soda-lime glass. Thicker or laminated glass can have higher STC ratings due to increased mass and damping layers.
  • Acoustic Impedance: High, reflecting most incident sound waves due to its density and stiffness.

Epoxy Resin​

  • Sound Absorption Coefficient: Low; epoxy resin does not absorb sound effectively.
  • STC Rating: Not typically measured, but generally considered to have a moderate STC rating due to its solid nature.
  • Acoustic Impedance: Relatively high because of its rigidity.

Baltic Birch Plywood​

  • Sound Absorption Coefficient: Moderate; better than many hardwoods due to its layered construction.
  • STC Rating: Varies with thickness, approximately 20 to 25 for common panel thicknesses used in construction.
  • Acoustic Impedance: Not typically specified for this material.

Cement Mortar​

  • Sound Absorption Coefficient: Very low; reflects rather than absorbs sound.
  • STC Rating: Not typically specified, but contributes to the overall STC rating of masonry walls which is generally high.
  • Acoustic Impedance: High, similar to concrete due to its density and rigidity.

ABS Plastic (Acrylonitrile Butadiene Styrene)​

  • Sound Absorption Coefficient: Low; limited sound absorption capabilities.
  • STC Rating: Varies with thickness and construction; generally moderate due to its plastic nature.
  • Acoustic Impedance: High, reflecting most incident sound waves.

PETG (Polyethylene Terephthalate Glycol-modified)​

  • Sound Absorption Coefficient: Low; similar to other rigid plastics, it does not absorb much sound.
  • STC Rating: Dependent on thickness but typically lower than denser materials like metals or concrete.
  • Acoustic Impedance: Relatively high due to its density and stiffness.

Aluminum​

  • Sound Absorption Coefficient: Very low; aluminum is a reflective material for sound waves.
  • STC Rating: Generally high when used in sufficient thicknesses but can vary based on the form of the aluminum (e.g., sheet vs. foam).
  • Acoustic Impedance: Very high because of its metallic nature and density.


STC (Sound Transmission Class)​

STC is a rating system used to measure the effectiveness of a material or construction assembly at reducing the transmission of airborne sound. It provides an estimate of how well a wall, floor, ceiling, door, window, or other barrier can attenuate sound. The higher the STC rating, the better the structure is at blocking sound. The rating is widely used in building construction to indicate acoustic performance with regard to speech privacy and noise reduction between spaces.
 
#12,957

Baltic Birch Plywood​

  • Density: ~0.021 lb/in³ - 0.022 lb/in³ (approximately 600 - 650 kg/m³)

Epoxy Resin​

  • Density: ~0.034 lb/in³ - 0.037 lb/in³ (approximately 1.1 - 1.2 g/cm³)

Soda-Lime Glass​

  • Density: ~0.092 lb/in³ - 0.093 lb/in³ (approximately 2.5 g/cm³)

Cement Mortar​

  • Density: ~0.140 lb/in³ - 0.150 lb/in³ (approximately 2,300 kg/m^3 to roughly match concrete density as specific data for mortar varies)

ABS Plastic​

  • Density: ~0.0374 lb/in^3 (~1,040 kg/m^3).

PETG Plastic​

  • Density: ~0 .0435 lbs / in ^3 (~1205kg / m ^3 ).

Aluminum (Generalized Data for Common Alloys)​

  • Density: ~0.0975 lb/in³ - 0.101 lb/in³ (approximately 2.7 - 2.8 g/cm³)
 
#12,958
camplo said:
I might as well also ask, how are you making your molds?
Click to expand...
I have not used glass beads in epoxy, since I want it clear, but with polyurethane I used 1:1. I think that same ratio would work with epoxy.

My molds for poly were aluminum and silicone. The aluminum required a mold release. For my recent epoxy test I simply fold up some parchment paper into a shallow pan. Epoxy won't stick to parchment paper, but you have to be careful of holes because the epoxy will leak out even a very small hole.

Silicone molds are not too hard to make, but silicone can get expensive. They also have a finite lifespan if that's and issue.

You could make the molds out of wood - a closed grain like maple - and seal it and wax it and it should work fine.
 
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#12,960
gedlee said:
Epoxy won't stick to parchment
Click to expand...
Omg, of course! I read this in my studies but, it didn't stick, I guess.... Earl you are an artist, I see 😊
gedlee said:
Silicone molds are not too hard to make, but silicone can get expensive.
Click to expand...
Thats an understatement, I just got quoted 200usd per linear foot at 36" wide, and 60usd starting charge for cut work.
gedlee said:
This is rather a dumb statement since whatever is not absorbed is reflected of course. (It's not your statement I realize!)
Click to expand...

lol You kinda have to tread lightly when dealing with the AI. My son put me on to BetterChatGpt which is much better than the normal interface but, where it is now, ain't where its gonna be.
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gedlee said:
I have not used glass beads in epoxy, since I want it clear, but with polyurethane I used 1:1. I think that same ratio would work with epoxy.
Click to expand...
Thank you for the suggestion I knew nothing of them... I know that sand is great... I haven't figured what type of weight to expect from each solution exactly but the space the microspheres take up is pretty desirable. I found 5 gallons for approximately 50-60usd and thats cool because I need somewhere around 14 gallons to do 2 36" cubes worth of panels at 1/4". Sand really stretches the epoxy and is as strong as glass. 1:1:1 Epoxy/Sand/Microspheres my thought.. I have no idea the size of a microsphere is my first thought

I am also interested in epoxied fabric. Cotton Sheet or Faux Suede sound interesting. With very thin ply's of material I wonder can I compensate with more bracing. Getting the epoxy onto the fabric in a controlled precise manner might be challenging. I am probably better off creating slabs of the epoxy mortar and then cutting it as needed just like it was wood.
 
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