Extending port of Pre-Fab ported box

[a4b7 0]

I know how most people feel about pre-fab boxes (especially ported boxes). I usually like to build my own boxes, but did not have time/tools (just moved). I am lazy and wanted more output from my sub, so I just bought this one. I know 'you get what you paid for', but for the price, I could not complain. I have seen alot of prefabs in the store, and this one does not look like one of those cheesy generic one. When I received it, I was pleased with the build..everything looked solid and well built. The only thing I wanted to change was the tuning. It is much louder!! than the sealed I had the sub in originally (no shock here), but a little boomy and doesn't hit the lows with as much authority. So I am hoping after I add some more wood to the port length, it will cut down the net volume and lower tuning.

1. Can anyone check the tuning of this box for me? I checked with re audio and it looks like 36hz. The sub I have in there is a 12" incriminator LI with a .13 cu ft displacement. The box is a bigger than I would want it, and tuning seems to be higher that I would like. Most of the other prefab boxes were too small so I did even bother looking at it.

2. How many inches do I have to extend the slot port (extend from inside box), so I can have the tuning down to 32-33hz? The lower the better. I was thinking about adding another 6 inches of port length inside the box.

Here is the link to the box

Ported Box Linkl

Same box link 2

[Julian 641]

if i'm reading this correctly.. it will actually raise tuning if you take away from internal space your tuning will raise.

[RAM_Designs 25]

if i'm reading this correctly.. it will actually raise tuning if you take away from internal space your tuning will raise.

Even with the larger ports that we're used to you're able to drop tuning by adding length, even though you're taking away volume...it just happens slowly and ends up shrinking box size quite a bit. With a small port that comes with a pre-fab it'll more easily drop the tuning while not eating up as much volume. The issue is that if it's a pre-fab box, it's more than likely too small to begin with. If I were the OP I'd try to extend the port outside of the box. First off, I'd find out the box specs.

Edited February 2, 2011 by RAM_Designs

[a4b7 0]

thanks for the fast reply...I was using the Re box calculator and it seems like the box is 2.54 cu ft tuned to 36 hz..if I extended the port another 7 inches, then the internal space drops to 2.4 cu ft and tuning down to 33 hz

I was just going off these values..I know it doesn't take into account sub displacement..but is the re calculator accurate?

[Julian 641]

IIRC lowering internal volume will increase the tuning.

[a4b7 0]

The box specs are in the first 2 links..it's a big box (roughly 2.55 cu ft), I avoided all the small ported prefab boxes because I figure it would be too peaky

[a4b7 0]

Lowering internal volume alone will increase tuning. However, I am also adding to port length.

[RAM_Designs 25]

Lowering internal volume alone will increase tuning. However, I am also adding to port length.

Indeed.

Edited February 2, 2011 by RAM_Designs

[RAM_Designs 25]

After .13 displacement for the sub, I came up with 2.42ft^3(this is assuming that the 17" port length provided by the company is internal length). This leaves you with roughly 39-40hz tuning. If you have the space, you can wrap the port around the outside of the box and have it fire the same direction as the sub. Just take off the carpet on that one side, and attach the port extension to that side in order to make the port flush with the sub. This will drop tuning to ~32hz. Then just re-carpet it or paint it black.

This is assuming you have the space to fire the port like that, and don't mind a slightly ghetto box.

Edited February 2, 2011 by RAM_Designs

[a4b7 0]

Thanks for the calculations...man that is high tuning. Do you know how much more do I have to add to the length to get it tuning down to near 32-33?

[RAM_Designs 25]

Thanks for the calculations...man that is high tuning. Do you know how much more do I have to add to the length to get it tuning down to near 32-33?

Inside the box, a bunch; it wouldn't be worth while. If you keep internal volume the same you're looking at 12-13" more port outside of the current box.

[a4b7 0]

thanks...seems like re calc is way off. I probably use it for a lil bit and then get someone on here to build me one.

[ulrisa 26]

Slightly off topic, but I had a 12" LI @ 32 hz in 2.5 cubes and it was great. I'd recommend just getting a new box, it will hammer the lows.

[Deto1992 5]

thanks...seems like re calc is way off. I probably use it for a lil bit and then get someone on here to build me one.

This is probably because the re calculator is for L ported boxes which yours was not.

[a4b7 0]

Instead of buying a new box, I figure I can try to seal it off somehow (building a plug, or building a baffle to cover up the side), and use a aeroport. Anyone ideas on which size diameter? 3 or 4 inch? How long? and should I install it on the the sides, or the front next to sub with a 90 degree bend? Thanks

[///M5 2,833]

It would surely take me no extra time to build a new box instead of dinking with that one.

[swift 501]

I would not be hard at all to do what Ram said. Unless you sell it I would give that a try and recarpet.