Can someone explain to me what is vacuum in a subbox.

[Memme]

Hello as it says at the title what is vacuum and can anyone give me some advice how to avoid vacuum and maybe some examples. Answer would be really appreciated.

What i know is that its not good but it also depends

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[RobGMN Premium Member]

Hello as it says at the title what is vacuum and can anyone give me some advice how to avoid vacuum and maybe some examples. Answer would be really appreciated.

What i know is that its not good but it also depends

Can you give us a little more info about where you heard this in reference to subs?

The only thing I can think of is a sealed box that is not fully sealed, and something is acting like a check valve at the "hole" that lets air out but not in.
Cone moves in, pushing air out, then the hole gets "sealed" and there is now a slight vacuum.

 

[Memme]

Can you give us a little more info about where you heard this in reference to subs?

The only thing I can think of is a sealed box that is not fully sealed, and something is acting like a check valve at the "hole" that lets air out but not in.
Cone moves in, pushing air out, then the hole gets "sealed" and there is now a slight vacuum.

because i have a L port and i cant have the subs behind the port because i would suffocate the subwoofer.
Wait here the subwoofer box. The problem is if i do like this i would trap the air behind the port wall

Subwoofer box DD Audio Redline 612e D4

12 inch subwoofer box design DD Audio Redline 612e D4, ported box plan, 3D model. Net internal volume 3.35 cubic feet, port area 50.00 square inches, tuning frequency 33 Hz. Subwoofer box calculator online

subbox.pro

 

[SlugButter]

because i have a L port and i cant have the subs behind the port because i would suffocate the subwoofer.
Wait here the subwoofer box. The problem is if i do like this i would trap the air behind the port wall

Subwoofer box DD Audio Redline 612e D4

12 inch subwoofer box design DD Audio Redline 612e D4, ported box plan, 3D model. Net internal volume 3.35 cubic feet, port area 50.00 square inches, tuning frequency 33 Hz. Subwoofer box calculator online

subbox.pro

That looks fine. You want to keep away from the port opening as much as possible, but I don’t see a problem with your design.

 

[RobGMN Premium Member]

That looks fine. You want to keep away from the port opening as much as possible, but I don’t see a problem with your design.

Seconded.

 

[Buck 5,000+ posts]

because i have a L port and i cant have the subs behind the port because i would suffocate the subwoofer.
Wait here the subwoofer box. The problem is if i do like this i would trap the air behind the port wall

Subwoofer box DD Audio Redline 612e D4

12 inch subwoofer box design DD Audio Redline 612e D4, ported box plan, 3D model. Net internal volume 3.35 cubic feet, port area 50.00 square inches, tuning frequency 33 Hz. Subwoofer box calculator online

subbox.pro

You can make a U or an S port. Here's an example:

I like to do this type of port when the box isn't very deep, sometimes, when it's advantageous. There's also some specific sound reasons to do a port like this, but that's an entirely different discussion.

 

[Memme]

You can make a U or an S port. Here's an example:

View attachment 33713

I like to do this type of port when the box isn't very deep, sometimes, when it's advantageous. There's also some specific sound reasons to do a port like this, but that's an entirely different discussion.

What sound reasons?

 

[Buck 5,000+ posts]

What sound reasons?

Bending the port multiple times can add resistance to the air movement in and out of the port, basically. So, you can sometimes use that kind of port to help in situations where you might suspect woofer or port loading in the environment would be poor, but you still need a decent amount of port area to avoid port noise.

Also, squeezing the port to one side of the box in a box without much depth helps give the main subwoofer loading chamber a good shape. This helps leave plenty of room around and behind the subs for cooling and subwoofer cone movement, and somewhat helps make sure the air inside of the chamber pressurizes evenly.

I'm not sure how strong each effect I explained is, but that's just how I look at it. I do know that the box I showed you an example of was built, and it did work well (according to the owner). I did exact type of layout due to where this box was going in a trunk, and how I thought it would be loading (pressurizing inside of the box chamber) in the trunk.

I think the link to the box that you gave here would work fine, but if I could do a multi-bend port here, I would.

 

[Buck 5,000+ posts]

There's a bunch of different layouts you could do here. You just have to make sure the enclosure is designed to be well balanced from every angle.

 

[hispls 5,000+ posts]

What sound reasons?

Way beyond the scope of what you are trying to do and more into the realm of creating "transmission line" alignments. For your purposes the less bends you have in the port, the better, and you should keep things at least the width of the port away from the port mouth inside and out if possible.

Assuming you are using DD subwoofers they are specifically designed to perform well in the boxes DD recommends on their website. If you put a DD sub into a properly build DD specifications box it will perform very well. I would suggest you use the largest recommended box size for your sub(s) that is practical for highest output.

You should be very happy if you build the DD box plans so long as the box is built out of good thickness material and all seems are airtight and solid.

 

[metalheadjoe 10+ year member]

Assuming you are using DD subwoofers they are specifically designed to perform well in the boxes DD recommends on their website. If you put a DD sub into a properly build DD specifications box it will perform very well. I would suggest you use the largest recommended box size for your sub(s) that is practical for highest output.

Doesn't this apply to all subwoofers? Brain-picking, not nitpicking.

 

[hispls 5,000+ posts]

Doesn't this apply to all subwoofers? Brain-picking, not nitpicking.

According to DD's published design philosophy they start with the box then build the sub around that so I'd imagine they probably test prototypes by throwing them into cookie cutter DD spec boxes to see what works best. Not sure who else has a cookie cutter box design that does well with every line of woofer they produce, or who else starts with sounding the way they want in a specific box as a primary goal when designing their product.

As far as the larger box being louder that's true all around though, but the DD in particular will really get busy once you get into the high end of their recommended volumes. I think every company needs to have some small box sizes published just to cater to the retail market that is largely going to be just dead set on cramming too much cone area into too small space and won't really know any better when they get poor performance.

 

[Slo_Ride 5,000+ posts]

How do you not know what vacuum is bro?

 

[Memme]

Way beyond the scope of what you are trying to do and more into the realm of creating "transmission line" alignments. For your purposes the less bends you have in the port, the better, and you should keep things at least the width of the port away from the port mouth inside and out if possible.

Assuming you are using DD subwoofers they are specifically designed to perform well in the boxes DD recommends on their website. If you put a DD sub into a properly build DD specifications box it will perform very well. I would suggest you use the largest recommended box size for your sub(s) that is practical for highest output.

You should be very happy if you build the DD box plans so long as the box is built out of good thickness material and all seems are airtight and solid.

okay but i dont get why you shouldnt have the subwoofer to close to the port. my car doesnt have much space but i know i can fit them

 

[hispls 5,000+ posts]

okay but i dont get why you shouldnt have the subwoofer to close to the port. my car doesnt have much space but i know i can fit them

The thing we are trying to avoid here is "turbulence" (my guess is you mistranslated this).

For the port to function properly you will want it to not be too close to other things that will effect the way the air column in the port vibrates and projects its sound.

You may be able to have port right next to a woofer or close to a hard surface in the vehicle and it will sound fine but performance becomes unpredictable once you add these new variables.

The way a port works is that it is a column of air being vibrated (similar principle of blowing across the top of a bottle). Try blowing across the top of a bottle and move your finger around the opening as you go, you can hear the sound change. With a port we have an opening on each side and anything too close to either opening will change the volume of air that is vibrated and also the efficiency.

I hope you can translate this enough to help.