EVA foam for performance speaker enclosures

[jeshi]

I find this very very interesting and wonder about a few things (with future builds in mind):

- does this mean that most speaker enclosures (Sealed, BR, MLTL, BLH) will sound better in EVA as opposed to plywood or MDF?
- if one would to make an enclosure from plywood or MDF and only clad or cover the inside walls with EVA (or even foam core), would that give the same results? Obviously one would need to increase the inside dimensions to compensate for the thickness of the EVA or foam core.

From my experience I don't think EVA foam will work in a subwoofer. I think a subwoofer will resonant the foam too much. I've tried it in a sealed box with a 6.5" driver and EQed to give an F3 of around 55hz, and chebum is rolling off at 70hz to his subwoofer. But for a midwoofer/tweeter EVA works great.


Also I think it might be doing more good on the outside rather than the inside. I think it might be working to absorb edge/surface reflections/diffractions. I say this because when I painted an EVA box, I was certain it sounded worse than the unpainted one. So now I leave all my EVA foam speaker unpainted. But I am also certain it is doing absorption on the inside too, absorbing resonances in the box panels. So it might be best to put it on the inside and outside with maybe a more rigid layer sandwiched in the middle between the EVA layers

So it will be interesting if chebum covers/paints his speakers and then notices a drop in sound quality. I think it is working similar to the foam diffraction absorbing surrounds around tweeters like on the old LS3/5a or on some of the current Wilson speakers like the Sophia where they cover almost the entire front of the speaker in diffraction absorbing foam. But with the EVA box, the entire front acts as a diffraction absorption material and there is no transition from foam to wood.

cheers jess

 

[chebum]

The woofer on top of tweeter is how I made my 10F/RS225 FAST for time alignment. Did you do it for same reason and can you give more details on your crossover? Active or passive etc.

I wanted to make a clone of Grimm LS1 speaker – thus the woofer is on top of the tweeter. No other reasons except this one. The crossover is an active one. However, it seems to be an off-topic here. There is a post where we're discussing its crossover:

Understanding Grimm Audio XO

 

[chebum]

So it will be interesting if chebum covers/paints his speakers and then notices a drop in sound quality. I think it is working similar to the foam diffraction absorbing surrounds around tweeters like on the old LS3/5a or on some of the current Wilson speakers like the Sophia where they cover almost the entire front of the speaker in diffraction absorbing foam. But with the EVA box, the entire front acts as a diffraction absorption material and there is no transition from foam to wood.

I left plywood for the front wall. Probably it will sound even better if I would make the whole speaker of the foam. However, the mats has a small texture you said will be difficult to remove. Hence I used plywood. A part of the older enclosure actually.

- does this mean that most speaker enclosures (Sealed, BR, MLTL, BLH) will sound better in EVA as opposed to plywood or MDF?
- if one would to make an enclosure from plywood or MDF and only clad or cover the inside walls with EVA (or even foam core), would that give the same results?.

I believe it's still anecdotal experience and I'm not sure every speaker will be better in a EVA enclosure. There a lot of great sounding speakers made of MDF. I wanted to say that my particular speaker made of plywood and later from plywood/rubber sandwich sounded worse than in EVA enclosure.

I suppose the first place to break in a EVA subwoofer enclosure is the speaker mounting. I believe subwoofer enclosure is manageable if we mount the driver to a sheet of MDF or plywood and then glue the MDF to the foam. IMO, if the surface of glueing is large enough, thick EVA enclosure will withstand force of the subwoofer driver.

 

[chebum]

I inserted some sparse metal cores into the foam. Unfortunately, i didn't think about assembling a mic and making a before/after measurements from the same position. So only personal impressions 🙁
It sounds differently, less smooth. I believe it's either these metal cores resonate or they reduced amount of even order distortion and thus made the sound less mellow. Unfortunately, no measurements to assure one of the hypothesis. Stupid me.

 

[bwaslo]

Interesting measurement chebum. You don't happen to make a way to make any accelerometer measurements on the cabinet do you?

 

[chebum]

Interesting measurement chebum. You don't happen to make a way to make any accelerometer measurements on the cabinet do you?

Unfortunately, I don't have an accelerometer.

 

[sumotan]

Guys how about sandwiching a thin layer of balsa wood with pva glue ?
This would add stiffness to the enclosure to handle bass work. I would imaging thickness of balsa sandwich would depend on enclosure size to get the best effect.

 

[perceval]

I love balsa... light and strong. Also perfect for wood surfboards!

But, depending where you are in the world, it can get quite expensive.

 

[sumotan]

Hi Perceval which part of Taiwan are you in ? Im Taiwanese too but have been working & leaving in Indonesia for like 12 yrs. Yes balsa when sandwich with foam has tremendous
strength.

 

[perceval]

Hello Sumotan (in Sumatra?)

I'm on the east coast, in Hualien.

But... in the spirit of expats, I'm not Taiwanese. I'm from Canada. Been living here for 15 years. Love it here. Almost feels like I'm a local! 🙂

 

[sumotan]

Im in Batam which is about a hrs ferry ride to Singapore. lol
Great that you enjoy living in Taiwan. Hualien lovely place.

Cheers

 

[chebum]

Adding a layer of balsa wood seems to be a good idea - we need to make the foam more stiff. I inserted 12 200x6mm screws into every speaker. With screws in it, the sound became more dynamic. Unfortunately, at the expense of some "magic" of women voices.

Only foam: YouTube
With screws: YouTube
Same song.

 

[Mattes]

Hi Jeshi, hi all,

many thanks for a very interesting read, which, amongst many others (have been a reader-only for years...) has inspired me to try EVA foam for my OB speakers.
After several prototype builds, I´m currently building an open baffle speaker, fullrange/wideband with woofer assist, out of EVA 125kg/m³, baffles are 16 cm depth for the woofer and 7 cm for the fullrange.
The fullrange baffle is already finished, bass baffle and ceiling base (this will be a free-swinging speaker, suspended by Dyneema strings, following Michael´s theory) yet to come. Teaser photo is attached, and if there´s any interest, I could open a thread describing the built in more detail.

All the best

Mattes

 

[perceval]

That is funky and way out there!

I love it!

Please do open your thread.
I would love to know more about this... if you don't mind sharing.

That is a strange looking full range setup.

If you also have measurements to see what the petal looking baffle brings, and the reasoning behind the whole thing.

Looking forward to some reading... again, if you don't mind sharing.

Cheers!

 

[xrk971]

5 petal asymmetry with rounded edges should have very low baffle diffraction. Nice design!
I see the suspended HF diffraction spreader element too.

 

[wesayso]

@Mattes is it a Fertin model 8? Nice! Love what you did with it with the petals.
I hope you'll start a thread about it.

 

[rex_johnston]

if there´s any interest, I could open a thread describing the built in more detail.

please

 

[ewollowe]

I'd be interested too Mattes.

 

[Mattes]

Dear all,

sorry again to Jeshi for hijacking her thread, but her EVA suggestion was of high value for the whole story.
I will thus make my last OT contribution here, please look out for the thread:

The making of: The black flowers

and I hope that wesayso doesn´t mind any similarities in the title...
Please allow a little bit of time, as I´m currently at work and have only limited satellite internet access during the next weeks.

Perceval: I´ll be happy to share, as I have learnt a lot in this forum over the years, it´s maybe the best source of knowledge for several things on this planet. Thanks for your kind words.

XRK971, exactly that was one of the rationals for the design. It´s a form follows function design without gimmicks. The suspension you see is the front suspension of the driver. The HF whizzer cone is mounted to the coil former in a traditional way, but more details later. The petals you see at the whizzer have of course a very similar reason, breaking off the bell mode.

Wesayso, yes, it´s a Fertin model 8 with fieldcoil motor, the only pair in Germany, and I´m proud of it, as I had to work long and hard before purchase...

All the best

Mattes

 

[ewollowe]

I was always fascinated by these fellows,

One of the more unusual loudspeakers to... - E J Jordan Designs | Facebook