Ported and sealed????

[HelloS10]

hopefully someone can answer this question for me. i have no idea what the difference between ported and seal boxes offer, besides the fact that one takes more airspace than the other. can someone tell me benifits/sound differences between the two. i have a ported box with two 10's would it be better if i had a sealed for the 10's? any help is much appreciated.

[xtrememeasures]

it all depends on what type of subs u have...u buy a box depending on what ur sub needs for air..just like u buy ur amp depending on how many watts ur subs can handle

[Tempe]

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SNEEK PEEK OF MY BOX DESIGN TUTORIAL CAN BE FOUND TOWARDS THE END OF THIS POST!!!
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For starters, it depends on what subwoofer you use. Based on the particular driver's design, one might be more suited for one of the two boxes. The sub's electrical and mechanical stregnth dictate this. If the sub is not that strong, the cone may flap sloppily in a ported enclosure, giving terrible sound quality. If the sub is very strong, the user risks loosing all the sub's low-end potential if placed in a small sealed box.

With a sealed enclosure, you usually want to look for an enclosure size that will give the sub/enclosure a qtc of 0.707. That is where the sub rolls off at 12 dB an octave. This is just like a crossover's roll off slope. The woofer will play a flat response line down to a certain frequency. Below that frequency, it will drop at that slope. In a perfect world, placing that sub in a vehicle would give a rather flat frequency response curve with the vehicle's transfer function. This would give you the best sound quality.

Some guys want more bump with a sealed enclosure. This is where the small enclosure comes in. By using a smaller box than the one described above, there will be a loss in low end with a peak in the midbass range. This will give you more pronounced kick drums. However, Late Nite Tip or Woofer Cooker might not hit those low-lows nearly as well. Also, efficiency is lost and power handling goes up a bit.

If you have solid midbass speakers up front, you could use a larger enclosure. This give you more low end while sacraficing midbass. This will make the subwoofer more efficient while dropping the mechanical power handling.

Ported is so much more complicated. For starters, you must change both the net volume and the port tuning. In addition, the size of the port's opening is rather critical in terms of sound quality and output.

The larger the box size, the louder the sub will play. In addition, a larger box will be a bit more peaky than a smaller one. On an extreme case, SPL enclosures are very large with a higher tuning frequency. By making it very peaky around the vehicle's resonant frequency, the enclosure can concentrate all the output down to one frequency in order to squeeze out the last dB out of the sub/enclosure. Like the sealed enclosure, the larger box will reduce power handling.

When the net volume is reduced, the total output of the sub is decreased. In addition, the power handling is raised a bit. Unlike the larger ported enclosure, the larger one will give a smoother response.

Port tuning plays a huge role in the overall sound. The higer it is, the peaker the sub's response will be. On the other hand, a lower tuning will make a smoother response. Sound quality nuts prefer a tuning around 25-30 hz. For daily driving, you can go anywhere between 30-40 hz, based on your preferences and the enclosure's volume. Anything higher than that will result in a very peaky response, like the SPL enclosure mentioned above, that will sound horrible. Additionally, a higher tuning can be bad for a subwoofer. If frequencies below the tuning frequency are played, the restoring force of the enclosure may loose control of the cone, allowing it to flop in the wind violently. This is more probable with subwoofers that are not as strong or with rather high tuning frequencies.

Port area throws a huge curveball to the novice enclosure builder. The port tuning is based on three things:

• port area
• port legnth
• enclosure net volume

If any of those are changed, the port tuning will change. This means that if you add bracing to your enclosure but do not figure it into your design, you will make the net volume smaller. By doing so, the port tuning will be raised. A larger net volume will result in a lower tuning frequency. If you have a small port area, the tuning frequency will be lowered. On the other hand, a larger port area will require a longer port legnth for the given net volume and tuning frequency.

What does all of this mean? Designing a ported enclosure is far more complicated than a sealed one. But this information is very important to anyone designing a ported enclosure. If you decide to use a small port area to get a shorter port, you will loose output and get lots of port noise. If you use a lot of port area, the port will be really long.

You might wonder what port noise is. If you have any home speakers that use ported enclosures, crank up a song with lots of bass. That "popping" noise you hear comming from the port is called port noise. This is not something you want to hear while cruising down the street. Using a larger subwoofer or one that has a high xmax will require a larger port area to prevent port noise. In addition, a larger port area will allow more output of the subwoofer. Think of the port as a second cone, and not a hole in the box.

On to the sound of a ported enclosure. Depending on the net volume and port tuning, the ported enclosure will almost always get louder and go lower than the ported enclosure from 30-100 hz, where most bass in music is found. A sealed enclosure, howerver, will usually give more lowend in the subsonic frequenices. Based on the design, you could make a 8" subwoofer EASILY get louder and lower than a 12" of the same brand/model. This would be done with a larger net volume and lower tuning frequency. Keeping with the larger enclosure, you could get a really peaky response (lack of low frequencies and a ton of midbass) by raising the tuning a lot. By using a smaller enclosure, there is a trade off in low end resopnse. Also, you will get less of a midbass peak. The really bad thing about using a small enclosure is the really long port legnth.

How do I get around using a really long port legnth? You could use a L-shaped slot port. This would involve using the walls of the enclosure to simplify port/enclosure design. By bending the port throughout the enclosure, you could get the legnth longer than the workable depth of the enclosure. Now keep in mind that the more volume the port takes up that the smaller the net volume will be. The resulting smaller net volume would yield a even longer port legnth.

My solution to this is to design the enclosure on a box design program until I get the frequency response graph that I want. Then I will pick the port area based on the subwoofer and number used. Finally I will guestimate the area taken up by the port. Then I add that to the net volume. Then you figure out how big you can make your box for your given area in your vehicle. The wood thickness, net volume, port volume, and bracing volume must fit within that available area. If you don't have enough room, reduce the net volume, reduce the port area, or raise your tuning frequency.

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That's all for now, fellaz.. I hope you enjoy my latest novel!!!



Tempe

[HelloS10]

wow, thats helps alot, i think i better sit down and think a new enclosure out b/c i just picked up a box at the swap meet (eesh). thanks for the info

[Tempe]