EVA foam for performance speaker enclosures

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You do have a point, I guess I am a little touchy, because I went to get new printer cartridges yesterday, and it was cheaper to chunk the printer and buy a new one, than simply by replacement cartridges.
I guess it's where the world is now days, we have to keep throwing away things and buying new to try and keep everyone employed.

The business model is to give away the printer and first set of cartridges at cost and to make money on subsequent $40+ ink cartridges. It's not a realistic cost to keep chucking printers and buying new sets - not to mention that it is bad for landfills and environment. Try the refill station at Costco etc or switch to laser printers.

I have to say that foam can last a long time if well cared for. The EVA and pink XPS foam cabinets are in fact, waterproof compared to a wooden cabinet. The paper faced foam core is not waterproof. So for wet splashy environments, the foam may actually last longer than wood.
 
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Back in early 70's Warfedale Speakers were available as DIY Assemblies.. Sans Cabinets.
But these were shipped, mounted in an Enclosure of Celotex(?) Cellulose Ceiling tile like material. All bolted up, complete with ports.
A Veritable Enclosure. Just not in wood or veneered.
Many used these shipping setups for Months while dealing with 'proper' enclosures.
In truth the shipping contraption wasn't that dissimilar performing than the final enclosures... just not as pretty.
IMO foam is for quicky builds.. No more than that.
 
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IMO foam is for quicky builds.. No more than that.

The first reply I got to my Foam Core thread was this:

actually it is bad if it moves or resonates... could be fun, but not accurate

300k+ views and two dozen builds later with decent measurements of FR and distortion, I think we can safely say, foam is not going to limit the performance simply because it is not hard like wood.
 
Back in early 70's Warfedale Speakers were available as DIY Assemblies.. Sans Cabinets.
But these were shipped, mounted in an Enclosure of Celotex(?) Cellulose Ceiling tile like material. All bolted up, complete with ports.
A Veritable Enclosure. Just not in wood or veneered.
Many used these shipping setups for Months while dealing with 'proper' enclosures.
In truth the shipping contraption wasn't that dissimilar performing than the final enclosures... just not as pretty.
IMO foam is for quicky builds.. No more than that.

Wait in one sentence you are saying that the Celotex cellulose box was similar performance to the final wood boxes, but then in the next you dismiss foam since it is not wood and shouldn't be able to perform as well?!?
People actually said similar things about the Celestion SL600 speakers with their aerolam walls, but then time has proven those to be high performing enclosures too.

I hope that this thread, my tests, and final speakers will show that EVA foam (specifically EVA foam, not just any foam or cardboard or cellulose) can be made to perform at a level similar to or better than wood. And that EVA enclosures can be made pretty due to its ability to be curved, wet sanded and painted.

I think grouping all foams together would be like saying that all wood performs the same in a speaker enclosure (balsa, plywood, chip board, MDF, baltic birch, oak, rubber wood,...). For example neoprene foam is a dramatically different material to EPS packing foam (I wouldn't want to dive in an EPS suit for example). EVA is actually more similar to neoprene than to what most people think of when they say "foam".

All I ask is that people are open minded and critical of the test results, rather than dismissive of the concept.

I will have time this weekend to prepare a proper post with the first round of my tests results (panel resonance testing)
 
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As Frank Zappa said..

"Without Deviation (From The Normal), Progress Is Not Possible"

I appreciate your efforts and thinking "Outside of the Box".. ;)

I don't have a real work shop and any alternative beyond wood and the need for large shop tools is welcomed by me. Thank You jeshi and xrk971 for standing your ground..
 
I think grouping all foams together would be like saying that all wood performs the same in a speaker enclosure (balsa, plywood, chip board, MDF, baltic birch, oak, rubber wood,...).

Has anyone tested balsa? It is much more 'machinable' than normal wood for people like me with no power tools but also more permanent feeling than foam. Seems it might also share some damping properties due to its light weight and ability to flex a little.
 
Balsa should be a good candidate for apartment builders as it is easily cut without power tools. It can always be skinned with fiberglass or cloth and glue if more stiffness is required. Price is much higher than foam core though.

The physical properties (MOE, density, etc) are around if you search for them.
 
Has anyone tested balsa? It is much more 'machinable' than normal wood for people like me with no power tools but also more permanent feeling than foam. Seems it might also share some damping properties due to its light weight and ability to flex a little.

Balsa would work well if it was laminated with say 1/16 - 1/8 (1.5 - 3.4 mm) plywood.
Which is what Aeromodellers do with firewalls.... and bolt nasty vibrating two-stroke engines to them.

I've been using this kind of foam for YEARS to make surfboards from, a company very close to me can make it as a 'mostly' bio-degradable product, bio content is roughly 60%.
http://www.homeblown.co.uk/product-category/high-density-foam/

I recently used some of the 200 weight as basket damping adhered with plumber caulk = one dead basket (it goes 'thunk' when struck).
 
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Balsa would work well if it was laminated with say 1/16 - 1/8 (1.5 - 3.4 mm) plywood.
Which is what Aeromodellers do with firewalls.... and bolt nasty vibrating two-stroke engines too.

The new generation of RC electric model builders now use guess what? Foam Core for their planes! It's strong, light, cheap, easy to repair. They make beautiful compound curved wings.
 
Here are some photos of my 2way satori mw16/rs28f build with EVA foam.

The aim of this particular design is to build a reference level near-field monitor, and I started this design in this thread
http://www.diyaudio.com/forums/mult...oice-8945a-8948a-sb15-sb17-satori-ss8530.html

Since I am designing for near-field use (1-2meter listening distance), it does not need to play as loud as a living-room or mains style speaker.Also the short listening distance means that to get better tweeter/midwoof integration, I wanted to get the center-to-center distance as close as possible but still using a high quality tweeter.

A few things about the design goals
- sealed cabinet with linkwitz dsp transform to give me F3 around 40hz
- rear mount the tweeter to get the tweeter/woofer center-to-center distance at 12cm. With these drivers it means a tiny amount of overlap
- time alignment of the drivers. (physical or DSP time correction)
- small waveguide for treble response shaping and improved off-axis
- LR2 time aligned crossover around 2300hz

I also wanted to do the build with removable front baffle so that I could play around with different baffle arrangements: rear-mount, front-mount, waveguide shapes...

Here are some pictures of the build process. The back and top are a single piece of laminated EVA foam (koyo softboard). I used a jewelers saw to rough shape the sides to the final curve. Then I wet-sanded with 120grit wet/dry paper to smooth the shape.

Here is the current front baffle. 30mm thick built up with 3 laminated layers. RS28f mounted 30mm behind which gives close to the correct time-alignment without needing DSP correction. Waveguide as shaped by hand and adjusted by ear and measurements. Sorry don't have records of this process.

I also tried rear mounting at 20mm which required additional DSP time correction, but I may have preferred the sound of that version. I will probably build another front baffle with the 20mm waveguide shape again.

I will post up measurements later. But I hope these pictures show that an EVA foam build can be made to look good and a high quality of finish.
 

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Jeshi,
The 2-way Satori MW16/RS28F looks great. The waveguide on the tweeter is very nicely done - did you use something for a template on the profile or is that sort of hand-shaped with eyeball estimate? I like your use of sealed and LT to get 40Hz as I do that too with my 10F/RS225 monitors. You might want to try the new Harsch XO using BW4 for the woofer and BSL2 for the tweeter to get time-aligned, near transient perfect response. I am doing that now on my 10F/RS225 and it sounds so much better than the LR2-LR2 XO.

http://www.diyaudio.com/forums/full...-rs225-8-fast-ref-monitor-65.html#post4398911

Anyhow, your speakers look great and I am sure they sound great too. Great choices in components and excellent craftsmanship. I love how you can throw the cabinets against a wall (without drivers installed) and they will survive. Are you using foam bracing inside to reduce the cabinet flex in the main "breathing" mode of vibration? Also, do you have a problem with the cabinets tipping over since the weight of the drivers on the front is so much more than the cabinet weight in the back?

Btw, I found a supplier of thick EVA foam sheets in the US. 1/2in thick x 40in x 80in sheets for $35ea.
https://www.foamorder.com/closed-cell-foam.html
 
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I will definitely try the Harsch XO in the near future.

I am still experimenting with bracing vs no-brace, lined vs no-lined. I have just ordered some 4mm neoprene to experiment with lining the box with that.

I really love working with the EVA foam. It is so resilient to squashing and bending, so easy to work with, and I can not stress enough how awesome wet-sanding is. I have allergies and so I am very sensitive to dust. With the wet sanding I have perfect "dust control" with simple water, and the wet sanding gives a very smooth finish. Wet sanding is how one works with acrylics, plexiglass to get that clear see-through look. Once I get close to finished, I will wet-sand with 400grit and 1000grit.
 
Here are some old measurements of just the RS28f in the waveguide. My notes were not so great, but I think these are from the earlier 2cm deep waveguide version. The current 3cm deep is very similar. I will make some new measurements soon.

And the waveguide is just shaped by hand and "eyeing" it. At some point I want to try a mathematically correct waveguide. But it is fun to hand shape, and the resulting response is pretty good.

As you can see from the response, the waveguide boosts the response and so the crossover must be set high (like around 3500hz) in order to get a final response around the 2300hz cross-over target point
 

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I LOVE the look of those speakers jeshi.
I always feel when I finish a surfboard, that glassing the pure white form is a waste of a sculpture.

thanks! Yeah this raw white foam does look very nice. I was originally planning to paint the speakers, but the the white looks so nice I think I will keep it like this.

For surfboards, do you use EVA or a polystyrene foam?
 
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