Wood Species Concerning Woofer Boxes...

So I work with this kid, and he and his brother make woofer boxes for cars. I've had a chance to see the work theyve done in one of their cars, an early 90's Mustang 4 banger. The box is very nice looking, and holds 3 low-end MTX, powered by an Audiobahn amp. However the system he has isn't in question, instead I'm asking you guys a question about speaker box wood species.

The kid says they use MDF on some boxes, but are more akin to particle board. The kid says he likes the softer woods, as it gives the bass more or a mellow low end. I don't know squat about woofer boxes, and I'm not sure I believe him. What do you guys think???

-ryan-

[zegoldfish]

Seems to make sense, in a very minute way. When you're dealing with sound everything in its environment has the potential to make a difference. It stands to reason that different species of wood a speaker box is made of will have some small affect on sound.

[kingsofcrunk]

A true car audio nut (like myself) will tell you that particle board is the WORST decision you can make on making a subwoofer enclosure. Why? Simple, imagine all of the sound pressure thats built up on the inside of a woofer enclosre, regardless if its ported or sealed. It's a lot, more than you can think of. Using particle board can and has collapsed due to high sound pressure levels. I first heard of this on the Rockford Fosgate forum. Apparently some n00b built his box out of particle board instead of 3/4" mdf (going against advice given by the gurus) and within a week he was jammin out to a song when he heard a loud boom and his subs cut out. He opened the trunk and found the box in pieces and the woofers damaged. Not only did he screw the subs up because of the hard fall, but debris from the particle board got inside the vented voice coil and made a mess. So he ruined the subs. At first I was kinda leery about this story, but had a friend that went to high school with me make a bandpass box out of particle board. I told him the story, and he didn't belive me. He was running two flame series Audiobahn 12's for around a month with the seats down. He was riding around when he heard the loud boom, and looked in the rear view mirror to see the enclosure in pieces and the subs laying in the trunk. Despite scaring the heck out of him, he ruined those subs. So, please, when it comes to building enclosures use at least 3/4" MDF. We can all relate to the phrase "you get what you pay for."

[Mendoza]

Hey I got a question fellas thats somewhat on topic. How would a plexi glass box sound with 6 12's? We are currently building one up at the shop and no one has ever heard a 3/4 plexi ported box with 6 12's. I am kinda concerned about the sound but hopefully everything turns out fine.

P.S.
Your buddys wrong.

[kingsofcrunk]

Originally Posted by Mendoza

Hey I got a question fellas thats somewhat on topic. How would a plexi glass box sound with 6 12's? We are currently building one up at the shop and no one has ever heard a 3/4 plexi ported box with 6 12's. I am kinda concerned about the sound but hopefully everything turns out fine.

P.S.
Your buddys wrong.

Who you referring to?

[Mendoza]

The kid says they use MDF on some boxes, but are more akin to particle board.

The kid about using particle board

[MIAaron]

Use marine grade plywood or baltic birch plywood if you're worried about weight, otherwise use MDF. You need density or strength for a good enclosure. MDF and particle board are very simliar in cost, so just go with MDF unless your worried about weight.

You can also get weaker output from your enclosure flexing. So it very well could be that they aren't very good at making enclosures. If they use something that is quite weak, like particle board, and don't brace accordingly the panels will flex. It takes a very small amount of flex to have a large effect on your output.

Well the kid's actually pretty smart, like that Jesse kid from F&F, however no matte rhow much bracing they do on the PB boxes, after hearing those two chilling tales, I'm just going to have him use MDF, he said it wouldn't be a problem and wouldn't bump the price up much more.

But then again, I might just go buy a box from a reputable Car Audio store in the area, I've rooted around one of his boxes, and it was very very nice.

-ryan-

[caraudiodave]

mendoza...i have worked with lexan before and ive gotta say that youd need at least 1" in order to eliminate flex, 3/4 is too think IMO. also, for 6 subs, id bump it up to 2" plexi, which is costly.

hallows-eve, i hope you dont get reemed too much for the FnF comment, thats kinda lame. hes a retarded ass kid, id write him off as a lop just for offering to build a box out of particle board. ive heard people using oak or hardwood which costs much more $ and weighs much more, but thats kind of an old school thing to do. id just go to a reputable shop since youve got someone to hold accountable if they do a shoddy job. i personally dont trust any shop to build me a box. they usually dont build it exactly to specs, or fi they do, they might use 1/2" MDF. if they build it how it should be built then theyll charge you an arm and a leg. its always good to ahve a friend who knows that they are doing.

Who are you talking about, because the kid in the movie wrote a computer prompt, and the kid I'm talking about is like a freakin' math genious. Both add up to 'pretty smart' in my book.

-ryan-

[kingsofcrunk]

Originally Posted by hallows-eve

Who are you talking about, because the kid in the movie wrote a computer prompt, and the kid I'm talking about is like a freakin' math genious. Both add up to 'pretty smart' in my book.

-ryan-

If he's so damn smart why the hell are you wasting your time asking for our opinions? Don't ask for advice then get all offended when we offer it.

[MIAaron]

Being a math genius doesn't mean he knows what he's doing. And some of us don't know the characters of FnF...????

[GrandAmGT1996]

I have heard of coating the inside of the box with Rhino Lining, they say it adds a lot of strength to the box. So would using 3/4" particle board coated in rhino lining be possible?? Just wondering, I wouldnt use anything besides MDF

Dude, who the hell p!ssed in your cheerios??? If you're offended, then don't even bother clicking on the thread dude, seriously, take it somewhere else.

snippet... And some of us don't know the characters of FnF...????

He was a highschool dropout, who had adhd, and wrote a bitchin' computer prompt which allowed them to view simulations of what the car they were building would look like upon completion.

-ryan-

[kingsofcrunk]

Originally Posted by GrandAmGT1996

I have heard of coating the inside of the box with Rhino Lining, they say it adds a lot of strength to the box. So would using 3/4" particle board coated in rhino lining be possible?? Just wondering, I wouldnt use anything besides MDF

It would cost more than just going MDF IMO. There is also a company who specializes in enclosures coated in bed coating material like rhino lining, but I can't remember the name of the company...

[IanGT99]

If your friend is going to charge you more to use MDF rather than particle board, you're getting screwed. 3/4" PB is about $16 for a 4x8 sheet while you can get MDF for around $19. If he's going to charge you the $3 difference, I can see that, but anything more is ridiculous.

Anyways, I used to use particle board back in the day when I first started making my own boxes (I was 15). It does ok when you're using very low end subs that don't get very loud, but once you turn it up, you're just asking for trouble. The molecules of air can escape through particle board because it's very soft and porous. I used to coat the inside of the box with latex paint to stop this from happening, but that still didn't make the thing stronger. Even bracing doesn't do much. PB is too weak of a material for the amount of punishing vibration good subs can create. MDF is a hell of a lot more compact and strong material. It doesn't bend, shift, or flex like PB. With very little or no bracing at all (for very small boxes) MDF is sturdy and the best bet for sub boxes. I wouldn't use anything else to make my own.

And like was said, you can be the world's greatest math genious, but calculators and computer code don't mean a thing when it comes to carpentry. You can be dumb as a rock and still build a good box. Just some simple adding, subtracting, division, multiplication, and maybe even some basic trigonometry is all that is needed in the smarts department. Other than that, enclosure design takes thoughtful planning, precision cutting, and a good assembly with the right materials. Particle board is not a right material.

Originally Posted by IanGT99

If your friend is going to charge you more to use MDF rather than particle board, you're getting screwed. 3/4" PB is about $16 for a 4x8 sheet while you can get MDF for around $19. If he's going to charge you the $3 difference, I can see that, but anything more is ridiculous.

Anyways, I used to use particle board back in the day when I first started making my own boxes (I was 15). It does ok when you're using very low end subs that don't get very loud, but once you turn it up, you're just asking for trouble. The molecules of air can escape through particle board because it's very soft and porous. I used to coat the inside of the box with latex paint to stop this from happening, but that still didn't make the thing stronger. Even bracing doesn't do much. PB is too weak of a material for the amount of punishing vibration good subs can create. MDF is a hell of a lot more compact and strong material. It doesn't bend, shift, or flex like PB. With very little or no bracing at all (for very small boxes) MDF is sturdy and the best bet for sub boxes. I wouldn't use anything else to make my own.

And like was said, you can be the world's greatest math genious, but calculators and computer code don't mean a thing when it comes to carpentry. You can be dumb as a rock and still build a good box. Just some simple adding, subtracting, division, multiplication, and maybe even some basic trigonometry is all that is needed in the smarts department. Other than that, enclosure design takes thoughtful planning, precision cutting, and a good assembly with the right materials. Particle board is not a right material.

I agree with you whole-heartedly when it comes to the smarts man, I completely suck at math and most of the other **** in school, but put me in a garage with some wrenches, that's where you'll see what I can do well.

He wouldn't charge me much more for the use of MDF over PB, he only charges for cost of supplies and then like $10 for making a 2-3 sub box, and around 8 for a single sub box. Pretty reasonable prices in my book.

I'm pretty familiar with wood species in general (Bass player, and the technical aspects of building guitars has a lot to do with wood species.) so I understand alot of characrteristics, and I know all about plywood and PB, I just wasn't sure how it held up in in this particular application.

I appreciate pretty much all the responses thus far, thanks again guys.

-ryan-

[MIAaron]

Here is what Dan Wiggins of Adire Audio has to say about it.

In 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).

Dan Wiggins
Adire Audio

[kingsofcrunk]

Here is some information directly from the JL Audio website that argues my side of the story:

A True Story

We once heard of a fellow using a triplet of our 10W6's in a sealed box powered with a 1200 watt amplifier. The box was not braced at all, was one big chamber and was made of particle board. While demonstrating the system for a crowd of people, the box literally exploded in his trunk, coating his trunk with sawdust and enclosure shrapnel, leaving the subs to play in free-air (not cool). Not only is it frustrating (or really cool, depending upon your personality) to have a box explode in your car, but it can also be very dangerous....after all, you could poke an eye out!

This is also on the site:

A flexing enclosure is a lossy enclosure. If the panels on your subwoofer enclosure vibrate, you lose output (SPL) and clarity. The solution is two-fold: use only 3/4" or 5/8" thick medium density fiberboard (MDF) and brace (reinforce) the life out of the box. If MDF is not available in your area, the only other real solution (barring exotic materials like sheet PVC) is to use a super high-quality plywood like birch or some other marine-grade plyboard. Avoid using particle board at all costs as it is too flaky (literally), doesn't hold screws well and swells like a sponge when water hits it. In short, particle board comes from the Pit of Hell. Avoid it at all costs.

I get what you coming from with the "high grade" ply wood (marine, baltic, and apple ply) but what his friend is referring to is plain old regular particle board

All this information can be found on JL's website at:

http://mobile.jlaudio.com/support_pages.php?page_id=164

[caraudiodave]

i disagree with that guy from adire. plywood is used in subfloors because its not as effected by percipitation as MDF is. MDF absorbs water and will rott very quickly.

I think everyone will agree, if youre not a top expert in the field then you need to use conventional materials. MDF is universally accepted as the standard wood for box building.

oh, and this kid from FnF is a DAMN CHARACTER!!!! its not a real kid who created this program (not a prompt) that will build a custom car with a few mouse clicks. hell, ive written lots of programs, none of which demonstrate or required my install skills. funny how people get all caught up in the life of characters.