That's correct. It definitely isn't new, research into this began nearly two centuries ago. FEA is a new term to me, I had to look it up - Finite Element Analysis? I'm not an engineer.
We can use negative feedback in amplification and I thought why not for a tranducer. Single Degree of Freedom was the expression that I had heard a siesmologist freind use when discussing damage after the 2011 earthquake in Japan. With Mark Audio using light basket frames from dense polymer I wanted a method to add mass and hence my method evolved. It costs pennies.
I'm not making any calculation - for now I'll secure a strip of lead to the wood brace for mass. The only detractor is nut's head is visable on the front of the baffle which some may find odd or ugly! The nut on the front allows tightening to draw the weighted brace in towards the rear of the baffle. Still experimenting, however.
Regards
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"Sound dampening of lightweight flooring" - Was hanging out at a place that sold Marble countertops, to purchase a few scrap pieces. They also sold flooring. One sample piece was a very nicely damped square, I noticed, in handling it. This was apparently by design. It was a showroom floor sample, so I knew they wouldnt sell it to me. But it's one place to look for such material, as this is a problem for them (as well) and clearly people have tried to solve it and productized their solution.
Imagine simply buying an already damped construction material instead of having to DIY? There may be a way to arrange it to have a nice cabinet finish as well. I bet it'd work damn good for the "foam-core" builds, as an alternative in going from foam-core to wood.
Imagine simply buying an already damped construction material instead of having to DIY? There may be a way to arrange it to have a nice cabinet finish as well. I bet it'd work damn good for the "foam-core" builds, as an alternative in going from foam-core to wood.
An abundance of great info and opinions folks.
Long before thinking of creating this thread, I had days of overthinking episodes of different strategies.
One was crafting the speaker bracing skeleton first, then gluing the inner outside wall to the skeleton. Thin ply or even polycarbonate sheet. Then I'd glue rectangular spacers to maintain distance to the outside thin wall made from the same quoted materials. These spacers would act as pseudo compartments to prevent sand from gravity compressing too.
The second idea was building the same concept with heat resisting materials, such as copper sheet and phenolic spacers. To allow me to cast molten bitumen, mixed with rock and sand.
A third idea would bring the concept to a waterproof level with polycarbonate, acrylic and silicone sealant to fill the compartment with a "kinetic" mixture of oil and fine particles.
Other ideas targeted the speaker basket and magnet systems themselves, such as adding mass to the magnet system or even gluing jars to the magnet, filled with sand.
I understand that mixing materials with different propagation velocities can be of benefit. Sand and steel balls can be of such example, however one needs to ensure a constant homogeneity of the particle mixture.
Long before thinking of creating this thread, I had days of overthinking episodes of different strategies.
One was crafting the speaker bracing skeleton first, then gluing the inner outside wall to the skeleton. Thin ply or even polycarbonate sheet. Then I'd glue rectangular spacers to maintain distance to the outside thin wall made from the same quoted materials. These spacers would act as pseudo compartments to prevent sand from gravity compressing too.
The second idea was building the same concept with heat resisting materials, such as copper sheet and phenolic spacers. To allow me to cast molten bitumen, mixed with rock and sand.
A third idea would bring the concept to a waterproof level with polycarbonate, acrylic and silicone sealant to fill the compartment with a "kinetic" mixture of oil and fine particles.
Other ideas targeted the speaker basket and magnet systems themselves, such as adding mass to the magnet system or even gluing jars to the magnet, filled with sand.
I understand that mixing materials with different propagation velocities can be of benefit. Sand and steel balls can be of such example, however one needs to ensure a constant homogeneity of the particle mixture.
One idea I had and even acted upon perhaps, was to decouple the speaker from the baffle entirely using a pliable material, in my case sheet rubber. Then re-couple the speaker basket / magnet to a suspended / floating mass behind it. All the driver has to "push against" in opposing reaction is the suspended mass arrangement. The baffle / cabinet is decoupled from vibrations caused by the driver being mounted to it. I did this on an open baffle, to keep the baffle from getting excited; then I went to the cork laminate,
In a closed cab, the acoustic energy radiated from the rear of the speaker can still excite cabinet panels.
Kind of the opposite of trying to get the baffle to resonate along with the cone.
try this
If you want a type of "black hole damping" try the following.
Get carpet for floors with rubber. If you put 3 to 5 of them as layers on all sides in the box. Its pretty dead.
Get carpet for floors with rubber. If you put 3 to 5 of them as layers on all sides in the box. Its pretty dead.
A few years ago, I made a "box in a box" speakers; the bass driver and cone tweeter both had individual enclosures inside a larger enclosure, and both mechanically isolated be soft foam gaskets between them and the front baffle - they are held in position by compression springs. I've also bolted 4.5kg lumps of cast iron to the back of speaker magnets.
Having done all that, I've come to the conclusion that an even dispersion throughout the frequency range, and a reasonably flat frequency response is more important, but an inert cabinet is important.
Ive used dry sand with good affect.its cheap and plentifull.gr8t thing about building diy speakers we are not constrained by pc hype to sell speakers using the latest board made by aliens on alpha centuri.
It would be nice if the sand could fit in the bottom of the woofer enclosure, but how to prevent dust and iron from migrating to destroy the motor and voice coil??
Frame it all the way around, then staple a piece of cloth cover over the sand. Unless you expect to ship it like that, without paying for the "No-Tip" service and assurance indicators.
Yeah, as usual the pioneers got it right the first time by building a rigid, massive framework to contain the driver and slipped the box over it using a bicycle tire inner tube to seal it.
Would love to see the mechanical drawing of that!
"We" had a large airflow test setup in a lab at work. Maybe 30" diameter. In the center of this tube was a plate that held the "nozzles" to make the flow measurement; it was sealed using bicycle tire tubes on both sides. You'd clamp the chamber halves together and then inflate the tubes, carried in a circular slot. They'd slip out somehow and blow up all the time...
It makes sense that one could reduce vibrations:
1. Directly at the source (driver). Let me summarize the following ideas and elaborations
-By decoupling the driver from the baffle. But, how effective and how linear vs frequency would these different materials be?
-By adding mass to the driver and reduce movement.
-By adding bracing towards the magnet and potentially make the bracing it lossy, wiith friction
-By using counteracting topologies, like push-push (bipole) with coupled magnet systems.
-By using a counterweight applying gravitational pressure to the magnet. To do this for a horizontally mounted driver, one could use a " Г " shaped, bent at 90deg rod, pivoting at the bend connected to the speaker bracing skeleton. One end of the rod would apply pressure to the magnet system, and the other end would have a weight attached.
-An active cancellation perhaps?
2. Directly at the speaker walls.
-By adding bracing, which decreases the effective panels surface area, increasing their resonant frequencies. Common technique.
-By pressure loading each panels. For example, spring loaded bracing to exert constant pressure. That would reduce the Q of each panel.
-Building a sandwich enclosure with dampening in-between.
-No flat panel enclosure, such as spheres.
1. Directly at the source (driver). Let me summarize the following ideas and elaborations
-By decoupling the driver from the baffle. But, how effective and how linear vs frequency would these different materials be?
-By adding mass to the driver and reduce movement.
-By adding bracing towards the magnet and potentially make the bracing it lossy, wiith friction
-By using counteracting topologies, like push-push (bipole) with coupled magnet systems.
-By using a counterweight applying gravitational pressure to the magnet. To do this for a horizontally mounted driver, one could use a " Г " shaped, bent at 90deg rod, pivoting at the bend connected to the speaker bracing skeleton. One end of the rod would apply pressure to the magnet system, and the other end would have a weight attached.
-An active cancellation perhaps?
2. Directly at the speaker walls.
-By adding bracing, which decreases the effective panels surface area, increasing their resonant frequencies. Common technique.
-By pressure loading each panels. For example, spring loaded bracing to exert constant pressure. That would reduce the Q of each panel.
-Building a sandwich enclosure with dampening in-between.
-No flat panel enclosure, such as spheres.
Cool!
In the net's relatively early days there was a huge amount of the pioneer's photos, drawings, measurements, docs, etc., including this design, but once gone from a virus.............
Speaker cabinet design has fascinated me for decades. There are many ways to go with it. I tend to want a really dead enclosure, hopefully allowing the driver to take its best shot at reproduction without any added interference. Someone tried to sell me on the idea that a cabinet itself could be 'tuned' musically like a musical instrument. I replied that it is a false start by building with particle board to begin with then.
One of the many constraints for manufacturers is the finished weight of their loudspeaker. Another is the volume of the cabinet.
If you are building from scratch and have space to experiment, those limitations don't apply. For example the front panel could be a partition wall , venting to a smaller room! As good as an "infinite baffle".
One of the many disadvantages to the home experimenter is we dont have an acoustic spaceship to hop into to get the response measurements in the anechoic chamber on Brüel & Kjær or Earthworks microphones and test equipment, the nearest we'll get to that is free open space outdoors and off the ground a bit with a pair of trained ears.
Here's a wild suggestion based on acoustic ideals.
The most inert, dead cabinet one could make is by using a large flexible bucket or similar irregular cylinder as a former, typically orientating upside-down, accommodating for drivers nearer the new 'top', ports if inclined, provisioning for cables... The material, rough cast concrete, ideally slow cure, laying some ties/ mesh (after the first or second cast) in areas that would get material handling pressures (corners), finish with another couple of coats of cast. One would fill the resultant void with rubbish to create an internal form to cast over the base, a 'one pour' homogenous whole a couple of inches thick. Then remove the rubbish infill through the bass driver hole when cured. One would probably want to get machined an alloy seating for the drivers that becomes part of the concrete cast that might allow for errors/ or different drivers. One could go to the extent of partitioning the interior dedicating a tapered infinite baffle for a midrange driver.
If you are building from scratch and have space to experiment, those limitations don't apply. For example the front panel could be a partition wall , venting to a smaller room! As good as an "infinite baffle".
One of the many disadvantages to the home experimenter is we dont have an acoustic spaceship to hop into to get the response measurements in the anechoic chamber on Brüel & Kjær or Earthworks microphones and test equipment, the nearest we'll get to that is free open space outdoors and off the ground a bit with a pair of trained ears.
Here's a wild suggestion based on acoustic ideals.
The most inert, dead cabinet one could make is by using a large flexible bucket or similar irregular cylinder as a former, typically orientating upside-down, accommodating for drivers nearer the new 'top', ports if inclined, provisioning for cables... The material, rough cast concrete, ideally slow cure, laying some ties/ mesh (after the first or second cast) in areas that would get material handling pressures (corners), finish with another couple of coats of cast. One would fill the resultant void with rubbish to create an internal form to cast over the base, a 'one pour' homogenous whole a couple of inches thick. Then remove the rubbish infill through the bass driver hole when cured. One would probably want to get machined an alloy seating for the drivers that becomes part of the concrete cast that might allow for errors/ or different drivers. One could go to the extent of partitioning the interior dedicating a tapered infinite baffle for a midrange driver.