Interesting thread. Looks like you're onto something!
How would you finish these foam enclosures?
How would you finish these foam enclosures?
Personally I kind of like them in this white sculpted form.
But I think painting them would also look good. In fact I am working on a new version of my small sealed truncated pyramid with a faceted baffle for my 10f/8424 which I am going to paint with black gesso. Following the kinds of baffles that Troels likes to make. Still trying to decide if do a black baffle with white box, or go all black.
I can imagine also applying wood Laminate if the box was made in a more traditional square edge shape. I know X did that with his 10f rs225 speaker made with XPS foam. http://www.diyaudio.com/forums/full-range/273524-10f-8424-rs225-8-fast-ref-monitor.html
But that is not the kind of aesthetic I like. I prefer speakers that look like these commercial speakers
painted metal
An externally hosted image should be here but it was not working when we last tested it.
and Neuman even makes their painted metal KH120 in white 🙂
Painted MDF
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But there are other forces that we can utilize: in particular the force required to compress air. When we compress air, we are pushing against the electron clouds and vibration energy of the air molecules. Simple classic physics: the ideal gas law.
https://en.wikipedia.org/wiki/Ideal_gas_law
Compressing the gas, in a constant volume, causes the temperature to rise which is energy.
The speaker driver is an energy source (motor like you say) can generate a few watts of energy so as it tries to compress the air in a fixed enclosure (fixed volume) it might convert its 50watts of energy into 0.026 degree C of energy change. So all we need is a fixed volume enclosure.
The enclosure which contains the air does not need any mass as long as it it can push back against the force of the compressing air. We could use a magnetic bottle to enclose a plasma gas (like in a fusion reactor). The plasma gas is not in physical contact with any structure, but is being contained by magnetic forces. The enclosure for the gas in this case is zero mass (granted the device used to create the magnetic enclosure has substantial mass).
Also air has mass. We can feel air pushing back when we wave a hand fan in the air. So even without an enclosure (open baffle) the air is going to push back against the forces of the driver. And open baffles have no enclosures.
I am not saying I want to try to build a zero mass cabinet (magnetic bottle). I am just saying that a light weight material which can contain a volume of air and push back against compressing air will work as well as a heavy material doing the same thing.
regarding absorption of energy on a baffle from a vibrating speaker. Most of us use a foam damping material anyways between our drivers and the wood baffles to absorb these vibrations. If the foam is ridged enough to hold the drivers and damp the vibrations, why would we need the wood?
which is why I go back to my statement that neither the mass nor the stiffness of the enclosure matters if it can contain a volume of air and absorb all the rear energy
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Jeshi: While it may not be a cakewalk to buy Baltic Birch plywood from a brick-and-mortar store (I'm in the west side of Tokyo), it is possible to find companies who sell it over the web, and appear willing to ship.
As an example,
�Finnish birch ply
Russian waterproof birch ply
There are others. Try a web search using either
カバ合板
or
樺合板
as search terms.
Additionally, there are companies offering cutting services. For instance
Town Page
shows that 株式会社もくもく Wood Shop Mokumoku in Shinkiba (（〒136-0082, 東京都江東区新木場1丁目4-7, phone 03-3522-0069, fax 03-3522-0084) sells Finnish birch ply, and will cut it on request (from 40 yen per straight-line cut).
hth, jonathan
PS. Thank you for a fascinating thread!
As an example,
�Finnish birch ply
Russian waterproof birch ply
There are others. Try a web search using either
カバ合板
or
樺合板
as search terms.
Additionally, there are companies offering cutting services. For instance
Town Page
shows that 株式会社もくもく Wood Shop Mokumoku in Shinkiba (（〒136-0082, 東京都江東区新木場1丁目4-7, phone 03-3522-0069, fax 03-3522-0084) sells Finnish birch ply, and will cut it on request (from 40 yen per straight-line cut).
hth, jonathan
PS. Thank you for a fascinating thread!
hi jonathan,
thank you that is great information about baltic birch in Japan. I will definitely check this out!
Sent from my iPhone using Tapatalk
thank you that is great information about baltic birch in Japan. I will definitely check this out!
Sent from my iPhone using Tapatalk
It is one thing to keep the back wave contained. But there's also the matter of the cone with it's own weight, moving back and forth. The enclosure has to deal with that force as well. That's why weight i.m.h.o. does play a role in enclosure design. Part of the reason for me to go wood instead of a reinforced epoxy mix for my tall speakers. Total moving mass in my speakers is 65 gram. Enclosure total weight about ~65 Kg. That's a 1:1000 ratio! I expect it to make a difference. How would a lightweight enclosure deal with that?
wesayso,
you have 25 TC9 per speaker right? Mms of TC9 is 2.6g so 25x2.6gm = 65gm. But each TC9 driver (magnet, basket...) weighs 0.3kg (300gm) so 25x 300gm = 7500gm of counter mass. So even with a zero mass enclosure you will still have a
7500/65 = 115:1 counterweight ratio.
that would be like a 70kg person punching quickly against an 8076kg (8 metric ton) object(approximately 3 ford F150 trucks, or an African male elephant). I really don't think that persons punches would phase a male elephant.
A speaker driver is vibrating back and forth not pushing in one direction so that I why I use the analogy of punching at the trucks/elephant. But even if we would consider "pushing" I don't think a person can push a large male African elephant no matter how strong they are.
I think even a 115:1 weight ratio is enough mass difference to not "move" the drivers. Even if the drivers were suspended in air by strings, they would not be moved significantly by the mass of the diaphragm making music. And I have seen people make suspended dipole speakers like this on these forums. So the mass of the driver is probably enough that we don't need that much more extra mass in the enclosure.
Of course drivers making sound will cause vibrations which can be absorbed by an enclosure, that is why we need the enclosure to damp the vibrations. Adding mass to an enclosure is one method of damping vibration, but there are other ways to damp vibrations.
And I know many people appreciate the aesthetic of "heavy things", so I can't argue against someone preferring a high mass speaker on aesthetic grounds.
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Hmm... Perhaps a layer of foam, then a layer of something heavy like sand, then a layer of foam again.
A sand sandwich if you like 🙄 .
A sand sandwich if you like 🙄 .
I wouldn't call it punching the Elephant, you'd be bumping into it using your full weight at 40 times a second to make some bass 😀.
Imagine the speed of that weight to be able to bump 40 times a second. It isn't only the weight that will move the elephant. The speed is as important.
It will be more like a 70 kg hammer punching the elephant.
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ok you do have a point, the person would be using their full body weight 😉. But I still think there is enough mass in that elephant to not be bothered by a little human vibrating on its leg.😀
But what about these string suspension dipoles I have seen around here? I can't seem to find the thread right now.
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Did a driver designer ever try eva thin surround for the cone ? Better choice than a reticuled sealed foam ! What is the type of foam than some designers like PHL Audio use for their surrounds ?
Could the EVA 2 to 5 mm a good tweaking to veneer as well the front bafle around the drivers ???
Hard to find such materials in France in small quantities !
The questions I ask myself with those mterials is how the long wave length and energy in the low frequencies can stop it to go outside if there is not a dense/thick material for the structure of the cabinet ?
An interressanr material (not easy to work with though) is the sheets made from lead : same damping loss coef than the birch ply wood ! Ok not cuttable with a razor but maybe good for a front bafle ??? with a sandwich of EVA/reticuled open foam ??
Could the EVA 2 to 5 mm a good tweaking to veneer as well the front bafle around the drivers ???
Hard to find such materials in France in small quantities !
The questions I ask myself with those mterials is how the long wave length and energy in the low frequencies can stop it to go outside if there is not a dense/thick material for the structure of the cabinet ?
An interressanr material (not easy to work with though) is the sheets made from lead : same damping loss coef than the birch ply wood ! Ok not cuttable with a razor but maybe good for a front bafle ??? with a sandwich of EVA/reticuled open foam ??
I have never quite fully understood the two camps: the audiophile camp says you need 400kg speakers and floor spikes so that the speaker doesn't budge and you get better bass, the other camp like pro audio and pro mastering mount their subs/speakers on wheels and doesn't seem to cause problems, or they mount reference monitors on soft compliant foam pads so that it is not mechanically locked to floor for better performance. Which is right? The pros say it actually *enhances* bass when you isolate it.
So what gives - do we need massive mass?
https://www.youtube.com/watch?v=JmP3QjdR__s
Maybe that is why the EVA or foam core speakers can sound good - built in isolation.
Audiophiles love spikes, they put them on their preamps and amps even 🙂
So what gives - do we need massive mass?
https://www.youtube.com/watch?v=JmP3QjdR__s
Maybe that is why the EVA or foam core speakers can sound good - built in isolation.
Audiophiles love spikes, they put them on their preamps and amps even 🙂
except the motor for that 70kg hammer is the elephant. Remember in my analogy the driver (magnets, basket) are the 8000kg (ie elephant). So it would be more like an elephant grabbing a person with its trunk and using it to hammer something.
Or maybe a better analogy would be a 70kg person grabbing a (70/115) 600gm hammer and pounding something with it. Would a person hammering with 600gm, feel that 600gm hammer pushing back and "move" them?
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This is exactly my point. The foam that pro-audio people use for isolation is basically EVA (its a flexible closed cell foam so EVA or other polyethylene blends). So by building an enclosure from EVA we get this isolation (and damping) built into the speaker 😀
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I understand that EVA might be difficult to find. The easiest source are those foam interlocking floor tiles, but they usually have some dimples which are difficult to sand off. But you are right they are much more expensive in France than America or Asia.
LOT DE 6 TAPIS DE SOL EN MOUSSE EVA TAPIS DE GYM MAISON OU BUREAU NOIR 24 M ²: Amazon.fr: Cuisine & Maison
But I am not sure I can really recommend these tiles. I bought some and the bumps make them very difficult to work with. Also the floor tiles I have bought are much lower density (more air, more squishy) than the art-supply koyo-softbaord grade I mostly use.
The more I explore these flexible, soft, bendable, closed-cell foams (like EVA) I realize that there is a family of materials that are very similar. polyethylene (PE) foam is also flexible, closed cell and very similar to EVA (polyethylene vinyl acetate). Either type should be ok. But they do appear to come in different formulas and densities. When I eventually do my panel testing I will include several different manufactures and grade of PE and EVA foam.
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Well I once met a bee while driving my motorcycle down the road at 100 km/hour and it kissed me on my upper lip. I did bulge 😀.
I'm sure measuring the back of the enclosure would reveal movement of the cabinet due to cone movement.
There are a lot of reasons for PA to have speakers one can actually lift.
Looking within a control room you'd find a lot of rooms with soffit mounted studio monitors...
I tried spikes with my arrays but used industrial rubber isolating feet in the end.
Not trying to be devils advocate here, just giving some counter views to think about. The best answer will probably somewhere in the middle. I do believe in isolation though. Used that as much as I could mounting the baffle to my enclosure, the enclosure to the stand and the stand to the floor.
I understand and don't take it personally.I just feel that there is so much resistance to changing ideas in audio. Look how long it took classD to get accepted as a high-end amp (and not just a cheap low power for portables amp).
Ok one more comment, and just food for thought (it is midnight here in Japan). People don't worry about the mass of headphones. Even though these headphones or earbuds are pumping out low bass. And some headphones have quite large diameter drivers. Yet we don't feel the headphones moving (or even vibrating) from the driver motors pushing the diaphragm.
I know that MDF speakers are not going to disappear anytime soon. I know many people still love the look of wood. And I know that people going into a store will not accept a lightweight foam speaker (without a heavy wood box surrounding it). And I know that even very well made and excellent measuring fiber-reinforced-polymer (ie advanced plastic) speakers have a difficult time selling (like the Genelec M030 Genelec M030) But this is DIY where we can push the boundaries.
Yet the planar types, the ones with very low moving mass get a lot of praise.
Even in PA you'll notice most of those drivers have big motors and light moving cones.
I'm probably way over the limit you'd need with my enclosures but the fun part is they don't move at all playing music while everything in my room resonates to the music. even my keyboard. Everything that moves, even the tiniest bit will contribute to the noise floor.
With a more flexible enclosure I think your moving that resonance down in frequency where it is less noticeable or obvious.
Even in PA you'll notice most of those drivers have big motors and light moving cones.
I'm probably way over the limit you'd need with my enclosures but the fun part is they don't move at all playing music while everything in my room resonates to the music. even my keyboard. Everything that moves, even the tiniest bit will contribute to the noise floor.
With a more flexible enclosure I think your moving that resonance down in frequency where it is less noticeable or obvious.
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I actually agree with all this. I love my ultra low moving mass Stax headphones, and I think low mass diaphragms/cones are the ideal. And I also think that a flexible enclosure (like EVA) is absorbing the energy, damping most of it, and some that is re-radiated has been shifted down in frequency (maybe to below 30hz). And in counter I often wonder if ultra high mass, ultra stiff enclosure might not be doing the reverse (re-radiating residual sound at a higher frequency).
and you do bring up a point, which is sound pressure level. At a high SPL where the sound is vibrating walls and furniture and keyboards, then the vibration from the speaker could cause them to "walk" if they are too light weight even if they are damping/absorbing the excess sound.
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