Subwoofer box construction...help

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I have a general Subwoofer box question.

If I'm building a Vented subwoofer box, putting the standard Cube shape aside. Are there any functional reasons for design choices on the inside of the Subwoofer box? I'm mainly talking about the various L bends and U shapes with-in the box.

If anyone has any knowledge on the subject...please chime in. It's hard to search Google for this answer.

See images for reference.

likepic.jpg


175562.jpg
 
I have a general Subwoofer box question.

If I'm building a Vented subwoofer box, putting the standard Cube shape aside. Are there any functional reasons for design choices on the inside of the Subwoofer box? I'm mainly talking about the various L bends and U shapes with-in the box.

If anyone has any knowledge on the subject...please chime in. It's hard to search Google for this answer.

The twists and bends are simply there to create an acustic space of a certain length in a box that is a lot shorter than the desired length. That length will cause sound waves of that length (and therefore a certain frequency) to resonate, increasing the volume of sounds in and near that frequency.

If you are building your own sub box and don't know about resonant frequencies I'd stay away from a vented or ported design or internal baffles and just go with a simple sealed box. Or get a well reviewed design and set of plans off the interwebs. Old school approach would also dictate filling the sealed box with sound deadening material. A ported design could be boomy at certain frequencies. (Think aftermarket nsx exhaust drone...it happens for the same reason.) That should provide you with decent base throughout the range of the subwoofer speaker and crossover circuit. The trade-off is you will have to drive the subwoofer with more power to achieve the same volume. But on the plus side, your speaker may be able to handle higher volumes without distortion...i.e. the base will sound "tighter".

Of course I know very little about any of this compared to what one should know to design a really good subwoofer...but that's also why there is so much crap on the market.
 
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The twists and bends are simply there to create an acustic space of a certain length in a box that is a lot shorter than the desired length. That length will cause sound waves of that length (and therefore a certain frequency) to resonate, increasing the volume of sounds in and near that frequency.

If you are building your own sub box and don't know about resonant frequencies I'd stay away from a vented or ported design or internal baffles and just go with a simple sealed box. Or get a well reviewed design and set of plans off the interwebs. Old school approach would also dictate filling the sealed box with sound deadening material. A ported design could be boomy at certain frequencies. (Think aftermarket nsx exhaust drone...it happens for the same reason.) That should provide you with decent base throughout the range of the subwoofer speaker and crossover circuit. The trade-off is you will have to drive the subwoofer with more power to achieve the same volume. But on the plus side, your speaker may be able to handle higher volumes without distortion...i.e. the base will sound "tighter".

Of course I know very little about any of this compared to what one should know to design a really good subwoofer...but that's also why there is so much crap on the market.

So, the inner structure essentially creates a better path for the sound to travel instead of bouncing around inside a box.

I'm assuming the batting fluff inside also creates less "echo"? Similar to the sound of an empty living room versus a room with carpet and furniture.

Lets say for instance I'm trying to create a box for very small speakers. Essentially trying to create the best sound/depth in the smallest package.
 
So, the inner structure essentially creates a better path for the sound to travel instead of bouncing around inside a box.

No. If your port needs to be 3" diameter and 12' long and your box is only 6' long than you can achieve a 12" long port by winding around inside.

I'm assuming the batting fluff inside also creates less "echo"? Similar to the sound of an empty living room versus a room with carpet and furniture.

Not really. Echos are high frequency sound waves that bounce off hard surfaces. The main purpose of the batting is to give the box a slightly larger "size" than it is physically as well as reduce resonance.

Lets say for instance I'm trying to create a box for very small speakers. Essentially trying to create the best sound/depth in the smallest package.

The truth of the matter is you can't fool mother nature - ie there have been a lot of attempts, some of them better than others to bend the laws of physics. Big bass needs a big box and drivers. A ported box is going to need a box that is almost 1.5 x larger than a sealed box.

I don't mean to be rude, but building a ported sub that sounds good is not an easy task, and you don't even understand the very basics. A ported box needs to be tuned, size and diameter, etc - it's as if you are making a musical instrument. If you are determined to build your own, go with a sealed box or someone else's design.

There are some kits available at PartsExpress.

http://www.parts-express.com/wizards/searchResults.cfm?srchExt=CAT&srchCat=536


http://www.hometheaterhifi.com/volume_6_3/diy-11-sonotube-subwoofer-september-99.html


But I got to tell you, aren't going to save any money DIY.

My favorite subs btw are http://svsound.com/
 
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I have a similar box to your 2nd picture, it was made at a local mobile audio store called MEGGAMAXX in Marietta, Ga. That said... He sold me on the size of woofer is relatively small compared to the sound it puts out. Below are links to the inventor of "The Wavebox" and the shop here in Atlanta that installs them. They may be able to help you build your own box if coming to Atlnata isn't in your future.

http://www.waveboxes.com/
http://www.meggamaxx.com/

+^1 The Captain is corrrect... A ported box needs to be tuned, size and diameter, etc - it's as if you are making a musical instrument.
 
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I understand your comments, thanks for the input.

I'm just trying to visualize a box for small speakers. If I have 2 small speakers, and I place them in some sort of box design. I'm wondering how to get a richer sound quality from generally mid-high audio range speakers. That's all :smile: An airtight box might be the best bet.
 
I understand your comments, thanks for the input.

I'm just trying to visualize a box for small speakers. If I have 2 small speakers, and I place them in some sort of box design. I'm wondering how to get a richer sound quality from generally mid-high audio range speakers. That's all :smile: An airtight box might be the best bet.

Ahhh...So you are NOT building a subwoofer. You are building an extra midrange speaker box. Then a sealed enclosure probably would be your best bet.

But the keys to clean full musical quality are sufficient power to accurately drive the speakers to desired levels with minimum distortion, accurate amplification components (a good head unit), and quality speakers. There is a problem with a midrange speaker box: it will reduce the sound image that is a product of a stereo (two sound source) music system. This isn't an issue with subwoofers because we cannot detect the source direction of lower frequency sound. It's midrange and higher frequency sounds that give us a sense of direction as to where the sound is coming from. The source material on a cd, mp3, or whatever is engineered in such a way that when it is played through a two-source (stereo) system, the listener's brain actually recreates a three-dimensional "image" that resembles the one the listener would hear if he were listening to the material performed live in its original setting. It is that sound imaging process that contributes a lot of what you call "fullness" to the quality of music, particularly vocals and music played on acoustical instruments...i.e. Jazz, Classical, Folk, etc. Adding a strong central source of mid-range will detract from the sonic imaging process. Your ears may not like the results.

A better solution would be to upgrade your head unit with a more powerful one and/or install better speakers, although the "better speakers" option is tough because sound is such a personal thing. (That goes way beyond the emotional and psychological aspects of sound. Different people hear differently because of physiological differences.)

Of course a project like you are considering doesn't involve nearly as much expense. And it could be fun and educational. But coming up with something that is an improvement over your existing system will be hit or miss. You might get lucky and end up with sound that is more pleasing to your ears. But you may end up with a system that has some striking sonic differences that may seem positive at first but as time goes on, chances are you would be able to revert to your original system and it would sound better to you at that point in time.
 
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Is this a question about autosound or home sound?

The box pic at the top with the elegant curved panels is very likely a transmission line design. These are very difficult to design and their behavior has not been modeled like sealed, vented (ported), or bandpass designs. The length of the line, the cross section, and the damping materials in the line if any contribute to damp the bass energy produced by the driver. The long vent is not designed to produce bass.

Vented systems are designed to take advantage of the resonance of the air inside a box to extend the bass response of the driver. The tuning of the box includes both the air volume and the vent dimensions. It behaves something like the pipe of a pipe organ - so that the air in the cabinet resonates at a specific frequency range. You cannot build a reasonable vented system by guessing. You need software that considers the driver's characteristics and the cabinet dimensions. Properly tuned vented boxes are usually larger than sealed boxes. But this not always true - a passive radiator system is technicall a vented box and can be compact.

Sealed systems do not try to use the air volume to produce bass. They use the air sealed in the box to help control the motion of the driver. The same software used to design vented boxes is usually capable of designing sealed boxes.

For autosound - none of this matters much except for subwoofers. The Bose "acoustic wave" design used in their clock radios and car door speakers a rare exception and probably behaves most like a vented box with the vent external to the box.
 
But I got to tell you, aren't going to save any money DIY.

In the case of subwoofers, I disagree. Home theater subs are massively marked up and someone with reasonable wood working skills can save huge amounts of money.

A brand name sub that costs $1000 has a $100 driver, a $75 cabinet, and a $100 Chinese made amplifier.

Subs from companies like SVS and Hsu Research are far better for the money than the typical sub.
 
Bose seems to be a company that tries to model a higher quality sound from smaller components and unique box /chamber design....whether they actually accomplish this is debatable.

I for one have a set of the original Accoustimass speaker system, (about 15 yrs old)...they work perfectly fine to this day. At the time, the sound was impressive (note I didn't say accurate or powerful) but impressive for small cubed sattelites and a small, hide in the corner mid-bass woofer. (hardly a "sub") Its never been my primary listening set of speakers, but always served us well as our speaker system in our formal living room, neatly and somewhat discretely mounted on each side of a flat panel TV....great for background music, watching TV with a bit more punch, etc. Bass is a bit muddy due to higher X-over freq, and image is a bit directional due to the sattelites having only 2" drivers, but that being said, again, sound overall is decent...and surprisingly punchy coming from the little sub box which has I believe 2 - 5" passive drivers. Overall system lacks a nice high end, and a deep low end, but does ok with the freq's in between.

As I said, I am not advocating these as great speakers, but to the OP, there are companies who have tried to get creative with ports, and bandpass boxes to assist with small drivers.
 
I have a general Subwoofer box question.

If I'm building a Vented subwoofer box, putting the standard Cube shape aside. Are there any functional reasons for design choices on the inside of the Subwoofer box? I'm mainly talking about the various L bends and U shapes with-in the box.

If anyone has any knowledge on the subject...please chime in. It's hard to search Google for this answer.

Looks like you have a fun project in front of you - I started building speaker boxes in my dad's stereo shop at about age 12 - still going!
 
The Bose Acoustimass "woofers" are a special variation of a bandpass system. Bose actually has a patent on it their unique design. DIYer can build similar systems but you cannot make one and sell it.

A bandpass system is unusual - it operates over a very narrow frequency range - it tunes a chamber both in front of the driver and and behind it. Usually the sound reaches the listener only through a port.

They are interesting systems and sacrifice range for bass over a narrow range. Very difficult to design and because of all the chambers they are difficult to build.
 
bose is crap, so are most big box brands.... folded horns is where it's at. I have two folded horns that stand 7 feet tall at home.... I've cracked drywall with them.
 
The picture that you are showing on top is actually a transmission line subwoofer and it can provide some of the smoothest, most natural bass. It is not a tuned port but actually a tuned waveguide with the length of the transmission line usually a fraction of the lowest wavelength. Having designed speakers and constructed them in the past, for a subwoofer, a sealed design is the easiest to construct and can sound excellent with tremendous bass output and response but this may require an extremely large cabinet.
 
Having designed speakers and constructed them in the past, for a subwoofer, a sealed design is the easiest to construct and can sound excellent with tremendous bass output and response but this may require an extremely large cabinet.

Sealed boxes are almost always smaller than other designs (vented, bandpass, or tlines) when tuned to typical "Q" values. Vented boxes with passive radiators or the rare isobarik design can sometimes be smaller than a sealed box.
 
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