i kno alot of ya use mdf but i already have 3/4 in 5 ply plywood so i was wondering if that would be good for a box? sq wise and so on....again im running 2 DD2512a's and a ed nine.1...thanks
Its hard to compare prices, since there is so many different types/grades of "plywood." Just go with MDF, it will be about the average price of any other ply, and yield a much better product.
You're not going to build a "bad" box with the 3/4" plywood. MDF is optimal, not mandatory. A properly braced and dampened box using sufficient materials will hold up fine, as long as you're not pumping 1000's of watts into in or subjecting it to extreme temps or humidity. Sadly, this is the enviornment these boxes are used in, so, disregard this entire post.
If you're talking solid-core baltic birch plywood, that stuff is pretty damn stiff, but it's also very costly and why bother. Some of the better pro sound speaker companies are using bb ply and those cabs pound. Eastern Acoustics is one. But like BJ said, there are a hundred types of ply, and most of them won't work in this app. The only thing about MDF is the dust it creates when cut is seriously bad news for your health.
Ummm sorry, but ANY solid known to man resonates, FACT! BTW my TCAB box is made from 3/4" OSB which is indeed more rigid than the equivalent in MDF. Polo.
But some reasonate more than others. And no, OSB is not the most ideal material to use. Not nearly as dense as MDF, but then again I dont use MDF either.....
As Brad mentioned, Baltic Birch is a great choice of material. However, you dont want to use 5 ply birch. The good baltic birch is either 13 or 15 ply, I forget. Lot more expensive than regular MDF (approx double the price).
Ha Ha Ecoustics geniuses come out of the woodwork to discuss MDF or Plywood. Ha HA Ha...
Trevor,
Its simple. Take a sheet of your plywood and a sheet of MDF and test it for yourself. Knock on it with your knuckles. The one with the higher pitched sound is better. This means that it is denser.
BTW, they also make HDF.
Personally I like to use 3/4" MDF, but wouldnt mind dishing out the dough for 1 1/4" MDF for a high end setup. 1 1/4" MDF is very good, and will make a world of difference, especially for subwoofer applications.
HDF is very hard to find unless it is in very thin veneer-style sheets, and it is also extremely heavy and expensive. The increased density in most cases doesn't warrant the extra cost and weight, hence the current popularity of MDF. I agree with the 1 1/4" MDF totally. I have a sealed box right at my feet (part of my computer audio system) as I type that holds a ID 10" and the box is 1 1/4" on all sides, not just the front. Overkill, I know, but I love this kind of sh*t. I would add to your "higher pitched sound is better" that very little if any sound of wood resonance at all is better as well. The only sound you can hear when you rap your knuckles on a well-made 1 1/4" box is the sound of your knuckles being crushed lol.
OSB isn't as dense but its tensile strength is higher allowing for larger gaps between bracing or it can allow no bracing at all. MDF flexes considerable that is why it is a poor idea to mount your amplifier to your MDF enclosure. The reason why people use MDF is to help prevent coloration of the sound not for its strength. JMHO...Polo. ;)
PS- I am not promoting the use of other materials just stating facts about them. MDF is in no way an ideal material, in all actuality concrete would be but that is imparactical but how about a MDF box lined with ceramic tile?
Concrete sucks in many different ways. I would not even dare to build a speaker box made out of concrete. Concrete is not good for sound, because it resonates uncontrollably. It transfers temparature too well, thus meaning it is not dense at all.
Sure, concrete can be made (speacialy mixed) to withstand great amounts of PSI (pounds per square inch), but that doesnt make it dense. Oh, and tile? Ha Ha Ha, tile just amplifies it for the worse.
My best guess would be that play dough would actually make the best non-resonant material, if you can keep it moist for extended periods of time. Too bad you cant make a box out of that stuff, but perhaps someone out there just might try and use it inside their box as a dampening factor
Lead is also a great dampening material and is quite dense. Some high end home audio speakers actually use it inside their boxes as well as sand. Dont ask, its an 80's thing, lol.
another decent plywood to use is marine grade, Void free. Any void free plywood will work well. Hey Mix, how about silly puddy, that stuff doesnt ever dry out especially inside a enclosed box. But you know how they have their distinct smells, I dont think it would be a very good car air freshner. lolol
Can you imagine drivin to dinner when she asks, "what is that smell?" and you tryin to explain that it is the stuff inside your box that supposed to sound-deaden the box, lol. I have a feeling she aint gonna buy it, Ha Ha. Better luck next time Rico Suave, Ha Ha.
I just threw it out there to allow people to understand what it takes to deaden the sound.
Ok, for one concrete resonates at higher frequencies, midrange level not the frequencies we use for subs. They use concrete in sound proofing and deadening material for the walls of recording studios. For two just because a material is dense has nothing to do with weather or not it will sound good. Ask your self how dense is fiberglass? fiberglass isn't even close to being as dense as anything other material we may use and it tends to resonate at lower frequencies. Now just because an enclosure resonates means it is bad, some enclosures sound better when resonatting especially home systems made out of birch, has a warm soft tone to it. Adding a deadener in my opinion is wastefull. What it does is absorb energy that could have been released with a more efficient port. The key here is to provide an enclosure that has little to no flex, the flexing is the real enemy because it is out of phase witht he movement of the sub causing cancellation. Bracing works well but is an internal restriction causing turbulance and reduced spl. Now if you can use a material that is rigid enough and doesn't resonate at lower frequencies the cancellation of material flex is no longer there. Resonation isn't the enemy, cancellation is....JMHO Polo.
1. Build only for the internal volume size recommended by the woofer manufacturer.
2. Make the construction (sealed or ported) air-tight.
3. It is invariably more advantageous to buy, rather than build, both economically and to assure quality of construction. If you are an experienced cabinet maker with the proper tools, it will make a good project, otherwise....
Note, that enclosures exist solely for the purpose of accommodating the woofer. Tweeters and midranges do not have to be enclosed at all, though for the sake of convenience they are often mounted in enclosures along with the woofer. To help you decide which type is best for your purposes, we offer below some detailed explanations and illustrations of each type, along with information on the types of materials used in their construction and a few suggestions.
SEALED BOX
The simplest direct-radiator system. The rear of the driver is in a sealed enclosure, and none of the rear output of the driver contributes to the sound output. Depending upon how stiff the mechanical suspension is Vs how stiff the enclosed air in the enclosure is (and that's a function of the size of the box), you can have one of two enclosure types: either an Infinite Baffle enclosure, in which the mechanical suspension is the dominant source of system stiffness and the box is large; or an Acoustic Suspension enclosure, where the air in the box is the dominating stiffness and the box is small. Sealed boxes tend to be among the lowest efficiency systems for a given box size and bass cutoff frequency. They are however quite good at reproducing a fairly broad range with little deviation or distortion.
VENTED ENCLOSURES
Also the same as Bass Reflex, Ported, or Passive Radiator. Here, an aperture or port in the box provides a means for the rear output of the cone to contribute to the total output of the system. However, it only contributes over a very narrow range of frequencies. In fact, in a properly designed system, the front output of the cone is reduced at the same time the output of the port increases. Consequently the port does not re-enforce the output of the woofer; it REPLACES the output of the woofer at these frequencies. If done properly, this can significantly reduce distortion and increase power handling at very low frequencies, a region that can be difficult for drivers. A vented system can be up to 3 dB more efficient at certain frequencies than a sealed box system that has the same bass cutoff frequency and size.
BANDPASS
These are compound systems in that they have at least two enclosures: one on the front and one on the rear of the driver. The enclosure on the front, which looks remarkably like a vented box (because it is), acts as a low pass filter and can couple the output of the woofer more efficiently to the outside. They have several useful advantages. For example, the front enclosure can be used as a very effective acoustic crossover, filtering out mechanical noises generated by the woofer, something no electronic crossover can do. For very low frequencies, such an acoustic crossover can be far less expensive and more easily designed than an equivalent electronic crossover. They are called "Bandpass" because the combination of the rear enclosure and the driver form the high pass portion while the front enclosure forms the low pass section. Making the bandwidth of the system narrower raises the efficiency of the system.
COUPLED CAVITY
A variation of Bandpass and vented systems, the coupled cavity enclosure is the result of attempts by designers to solve specific problems. These enclosures consist of two or more rear enclosures, each coupled to the next by a vent. Each enclosure/vent combination is another resonant system, and the combination is, essentially, a high order, multi-tuned resonant system. Generally, these systems have quite complex response and are difficult to design. No comprehensive theory on their operation exists like that for sealed, vented and Bandpass systems.
IMPEDANCE MATCHING IS IMPORTANT
Many builders and users like to take advantage of the power advantages of operating the amplifier in bridged or mono mode. To do so however, means that the impedance requirement of the drivers be taken into account when designing a proper circuit. For this purpose, we have provided an impedance calculator
(Back To The Top)
MATERIALS What is the best material to make speaker boxes? An ideal speaker cabinet material would be very stiff, so that it would tend to be stable with variations in box air pressure. It would also be very well damped, so that if it ever does deflect from air pressure, it will come back to the original position without resonating. In addition, it would have a very high resonant frequency (supersonic), so that low frequency box air pressure would not cause it to resonate. An attractive material is preferred, and additional credit is given for a material that is easy to cut, glue, and finish. A great material would be cheap, too. Finally, it would be nice if the material were light, because we all have to move our speakers sometimes, and it's hard to appreciate good speakers with a sore back.
With all of those attributes, it would seem that no material is perfect. However, there are many materials that have enough of the above good attributes to make excellent speaker cabinets. Each, however, has advantages and disadvantages. In the list of good speaker box materials below, the following code letters are used to indicate which attributes the material possesses:
S = Stiff - D = Damped - H = High Resonance A = Attractive - M = Malleable C = Cheap - L = Light.
MEDIUM DENSITY FIBERBOARD (MDF) Code: SDMC This is the most practical material for quality speaker enclosures. It's extremely rigid and resistant to sympathetic vibrations in thicknesses over half an inch. It cuts very nicely and has a smooth surface. It takes veneer very well. However, bring a helper when you pick the stuff up; one sheet is very heavy. MDF is harder on tools than common wood, but easier than particle board. This is the material that many great speaker makers use. Approximately $45 for a 4'x8'x1" sheet. Density: 50-lbs./Cu. ft.
POLYCARBONATE (LEXAN) Code: DMA A clear or solid-color polycarbonate box can look strikingly good. However, this is not a cheap material. To locate it, look in the classified directory under PLASTICS. Approximately $400 for a 4'x8'x0.5" sheet. Density: 75-lbs./Cu. ft. Acrylic (Plexiglas) is cheaper than Polycarbonate, but weaker and not as well damped (not recommended as a main construction material, but used for "windows" in Bandpass enclosures).
PLYWOOD SPACED AND FILLED WITH SAND OR LEAD SHOT Code: SDAMC Not a good choice for Car stereo because of weight issues. If you have time on your hands and want a great impractical box, try this. Make a simple box out of common plywood. Then glue cleats on the outside of the box to space the outside plywood from the common plywood. Glue hardwood-veneered plywood to the cleats and pour sand or lead shot into the spaces between the cleats. It won't be light, but with the filler, it will be extremely well damped. In addition, if you use strong cleats and glue well, the box will be extremely stiff. One designer was known to use different size Sonotubes as an alternative to plywood, and filled the space between them with sand. Be sure to sterilize the sand in your oven before putting it in the box.
ALUMINUM SHEETS FILLED WITH ALUMINUM HONEYCOMB (Aerolam) Code: SDHL Airplanes use this material for flooring. Next time a plane crashes in your neighborhood, see if you can get the wreckage for your next speaker project. You can't get a better, lightweight material. If you're really ambitious, you can make your own sandwich out of high-quality plywood faces and a thick honeycomb core. You will probably need an epoxy to glue the honeycomb to the plywood. A home-brew sandwich is easier to cut and glue than Aerolam.
FORMED CONCRETE Code: SDHC Not a good choice for car speakers due to weight. There are tricks to working concrete, such as to cast braces, rebar, and steel-wire right into the mix. Also, some types of concrete are better damped than others. Remember to oil your concrete forms so that they can be removed. Most concrete speakers use an MDF front panel, but you can pour one if you use cardboard tubes or plywood rings to mold the concrete into the shape of a speaker cutout.
Alternately, you can make a common veneered plywood speaker box and cast concrete inside it for stiffening. Any box can be improved by making the walls thicker, by bracing the walls, and by stiffening the walls. The stiffness of a material goes up as the cube of the thickness, so a slightly thicker material is much stiffer. A thicker panel will also have a higher resonant frequency because the stiffness goes up faster than the mass. Consider lining the inside of your speaker with ceramic tile, attached with thinset mortar. You can get tile remnants cheaply. They are easy to apply and can be added as an afterthought to an imperfect box. However, be sure to attach all braces before tiling, because it is hard to attach anything to tile. Also consider bracing any weak parts of the box. For example, all joints will benefit from a wooden cleat. The back of the box will benefit from stiffeners where the speaker terminals are attached. Most importantly, brace the front panel, or make it out of a double thickness of material.
