Box by Belunt

[PV Audio 5,000+ posts]

//content.invisioncic.com/y282845/emoticons/rolleyes.gif.c1fef805e9d1464d377451cd5bc18bfb.gif If you don't understand why you would use plywood, then you have no reason to use it. Am I an *******? Maybe. Do I know how to make enclosures and not waste money on things that give me no practical benefits? 100% yes.

 

[T3mpest 10+ year member]

Yep, none of you have any idea as to what you're talking about. Just because this forum has taken to using birch ply for some reason does not mean that the industry has changed in the least. Both have been around forever, and MDF still has the practicality benefits on its side.

General marine grade plywood (or Baltic birch, apple ply, or any other void-free plywood) is superior for subwoofer use. The reason: stiffness.

Subwoofer cabinets WILL talk - they will vibrate. The key is to keep the cabinet from vibrating in the frequency range of the subwoofer. There's two ways to do it: push the resonance of the cabinet above the pass band of the driver, or push the resonance of the cabinet below the pass band of the driver.

To push the resonance above the pass band, we need to make the cabinet stiff. Stiffen something, and it resonates at a higher frequency. In this case, plywood is MUCH better than MDF. Plywood is simply stiffer than MDF, and that's why it is used for sub-flooring, cabinetry bases, and other strength-critical uses. It is the lamination of cross-oriented layers of wood that gives you the strength. No matter how you try to bend it, some of the wood fibers are in tension, which is where they are strongest.

To push the resonance below the pass band, we need to make the cabinet heavy. Add mass to something, and it resonates at a lower frequency. This is where MDF is better - it is much denser than plywood, and as such will take less thickness to lower the resonant frequency of the box. Of course, making a wall thicker also increases the stiffness, which runs slightly counter to the addition of the mass; the resonance still lowers, but not as fast as one would expect.

Overall, it's easier to make a box sufficiently stiff to not resonate below 300 Hz, than it is to make a box heavy enough to not resonate above 15 Hz. Bracing and stiff wall materials raise the resonance - bracing ADDS stiffness (as well as physical strength to hold up a driver, for instance).

Additionally, we need to consider the internal loss. As sound passes through material boundaries, it loses energy. The more layers, and the greater the changes in density, the more energy is lost. MDF is a VERY homogeneous material - it has little internal loss. Plywood, on the other hand, has multiple layers and has considerably higher internal loss. So acoustic waves will be better attenuated by plywood than by MDF.

And in the automotive world it is, IMHO, superior to MDF in two other significant ways: weight and water resistance. Less weight is always good - better gas mileage, easier to build/move, etc. And plywood doesn't swell and turn to mush, like MDF. In fact, marine grade plywood is VERY water resistant. No problems living in damp conditions in car trunks, or getting rained on occasionally.

Overall, if you don't mind paying an extra $25 a sheet for the material, I'd go with a quality void-free plywood (marine grade, Baltic birch, apple ply) over MDF, especially for subwoofers in cars. Lots of benefits, and only one real drawback (the slightly higher cost).

(tell that to Dan Wiggins)

 

[tommyk90 5,000+ posts]

I still cannot understand in the least why people use plywoods over MDF in car audio. Seriously, it is a colossal waste of money. unless you have a huge enclosure, there is no point. You are only going to see advantages if it's true 13 ply anyway, which costs 3-4x more than MDF for only weight savings (you will never see the other benefits in car audio subwoofer enclosures). MDF has been used for years, and is still the #1 material used in home audio speakers made for production. Again, save your money, because unless you understand the reasons to use plys instead of MDF (which there are none in this case), you're throwing money away and costing the customer more.

Why is it that every time a thread pops up about birch you have to go and post the same old bullshit?

Please just shut the f*ck up and keep your OPINION to yourself, because nobody else wants to hear it.

The box looks very nice, THAT'S WHAT THE CUSTOMER WANTED, and guess what, it didn't cost you a dime. So STFU.

 

[mlstrass 5,000+ posts]

Personally I'm SICK of MDF dust, so BB it is for me. Luckily I can swing the extra $$$ for it. LOL

And IMO it looks nice stained. PV have you ever built a box with BB? After finishing my first one I knew I'd never use MDF again...

 

[Eugenics 5,000+ posts]

I think carpeted boxes are ugly. and i would never run an MDF box ugly. birch is where its at. And the cost argument? bunk. Is a 300 dollar SPL driver 100 or even 25% better than a 200 dollar SPL driver for the same purpose? probably not.

 

[tez4life Premium Member]

Nice, as usually beautiful work by Mr Belunt:thumbsup:

 

[ballstothewall 10+ year member]

Have you ever considered trying mitered edges so you don't see any endgrain??

Nice looking craftsmanship on the box, although my personal preference is making the box so you can't see endgrain on the front baffle.

 

[skitzafit 10+ year member]

I have no problem with the look of it. I wanted it bare.

 

[lookitsjim23 10+ year member]

box does look very nice

 

[momuzykent 10+ year member]

nice job...

 

[Belunt 10+ year member]

To Belnut, not hating at all cause that's a beautiful enclosure. So what kind of plywood was this enclosure made out of (baltic birch, etc), how many ply, and where did you buy it? If you don't mind me asking, how much did a sheet cost (you can PM me if you don't want to post it here)? Just curious as to why you chose to do the labrynth port shape with the 180 degree bends rather than an L (an L has less resistance to airflow, correct?)?
Does anyone have a pic of a car audio enclosure that someone made out of plywood and stained? I'm really considering the idea.

BTW, this is interesting. I've of course heard of using plywood, its benefits as well as its drawbacks, but never have I seen so much MDF hating. Then again I don't usually post here (I'm a CAFer, but I'm around here more often now because CAF is a little too full of the repetitive questions), so mabye this forum is just extemely biased to the plywood, so much as to degrade MDF. IDK

You got da PMs, and there is a reason behind just about everything on the box. HERE is a link to an enclosure I just did with a stained baffle, haven't had an order for a full stain yet but keep your eyes peeled in the future. This one in particular was setup to be possibly carpeted at a later time reason behind visible screws/joints like this. I'm biased to Birch for a number or reasons particularly over MDF.

And do either of you have closer up pics of the screw speaker terminals? Are there special bolts that conduct better than others that need to be used?

Just binding posts, these:

Personally I'm SICK of MDF dust, so BB it is for me. Luckily I can swing the extra $$$ for it. LOL
And IMO it looks nice stained. PV have you ever built a box with BB? After finishing my first one I knew I'd never use MDF again...

X2

Nice, as usually beautiful work by Mr Belunt:thumbsup:

Thanks man

Have you ever considered trying mitered edges so you don't see any endgrain??
Nice looking craftsmanship on the box, although my personal preference is making the box so you can't see endgrain on the front baffle.

This enclosure was setup for possible carpet at a later point and to be built *****, not a full stain so the build was different as opposed to a full stain in which screw heads wouldn't be visible.

box does look very nice

Thanks Jim

nice job...

Thank ya

 

[jibberjive 10+ year member]

You got da PMs

No, can't say that I do have PM's As far as the reasoning behind the labrynth rather than the L, I can't imagine that'd be top secret (like the prices) so why don't you go ahead and post that here. To be honest I can't think of any advantages to it over the L shape, unless the mounting depth is an issue. BTW that stained baffel box is one of the best looking boxes I've seen. Did you have the same issues bending the birch as the previous poster? Did you buy those binding posts locally, or online? another BTW, I'd never heard of that other forum you linked until right now.//content.invisioncic.com/y282845/emoticons/suave.gif.858fc102f7646e678ee8af7e1fbc41d1.gif

 

[Belunt 10+ year member]

No, can't say that I do have PM's As far as the reasoning behind the labrynth rather than the L, I can't imagine that'd be top secret (like the prices) so why don't you go ahead and post that here. To be honest I can't think of any advantages to it over the L shape, unless the mounting depth is an issue. BTW that stained baffel box is one of the best looking boxes I've seen. Did you have the same issues bending the birch as the previous poster? Did you buy those binding posts locally, or online? another BTW, I'd never heard of that other forum you linked until right now.//content.invisioncic.com/y282845/emoticons/suave.gif.858fc102f7646e678ee8af7e1fbc41d1.gif

You do now, sorry CA was acting up there for a minute? I'm not sure if anyone asked about the box price but my prices are no secret, ask those in the past who have bought off me and they'll tell you my prices were extremely reasonable. Not sure what issues you're talking about but no, other than not wanting to sell it after looking at the finished product //content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif. Partsexpress.com - sells those binding posts. And CAJ FTW!

 

[jibberjive 10+ year member]

I wasn't referring to you box prices as top secret. I made that comment because I told you to PM with the price you paid for the birch if you didn't want to post it here (IDK some people might have a problem with saying how much materials were cause then someone could know how much their labor/profit was. I thought I'd just be sensitive in case that's how you are.) So was the labrynth because of the mounting depth or other advantages/concerns?

 

[Belunt 10+ year member]

And as far as the wood debate that poked its head into the thread, next time I'm going to ask that you make another thread and leave it off my build threads. Thanks //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

Jibber check you PMs