Ported Q's port length

[DUAL10S 10+ year member]

Been talking off and on about ported and sealed boxes. Been kicking around all sorts of sub configs and looking at two Q 18's.

Again, never messed with ported and want to do two 18's in a 2 chamber ported box.

Total box measurments: 60w x 24h x 21d

Each box or chamber will measure 30w x 24h x 21d (sharing the top, bottom and back of the total box). Will put the slots in the center of the box or center the subs and put a ports on the outside of each sub. Not sure if it will make a diffrence so I guess whatever looks best.

So I came up with ~7.0 cubes after displacement for each sub tuned to 28hz (as per FI specs). Each port shows to be 22.5 x 4 x 35.

Does this look ok?

Click to read more...

 

[DUAL10S 10+ year member]

Other thing I am not sure about, does it matter where the sub is centered?

The port will be 4" wide, so do I just center the sub in the remaining front face of the box?

or

Do I need to put the sub somewhere specific in relation to the port?

Thanks

 

[SpeedEuphoria 10+ year member]

You will get better output in a shared chamber for both subs

same goes for ports, normally a single large one will be louder, the more square you can get it is better also(which would happen automatically by using a single for a shared box)

normally you put the sub close to the port and away from the beginning of the port within the box(referring to "L ports")

otherwise your box seems fine, 90" square of port for 7cubes which is sufficient. I'm not totally sure how the 12-16" square per cube applies to large boxes like the one(s) your building.

 

[RAM_Designs 5,000+ posts]

You will get better output in a shared chamber for both subs
same goes for ports, normally a single large one will be louder, the more square you can get it is better also(which would happen automatically by using a single for a shared box)

Agreed, I'd definitely do a single chamber and single large port.

 

[DUAL10S 10+ year member]

Thanks

So if I build the box with both subs sharing the same chamber, I come up with this:

14.85 cuft tuned to 28hz

Port (slot)would be 22.5" tall and 8" wide with a length of 30.5"

Using .75 mdf, I should set the first sub ~1" to the side of the port (slot) and the second sub 1" from the first sub? That should keep the second sub as far away from the beginning of the port (slot) within the box as possible. Not sure what side of the box the port (slot) will be on. Will it make any diffrence?

Thanks again

 

[DUAL10S 10+ year member]

Just did a quick sketch and with the Q's 10" mounting depth, that will only give me ~3" from the magnet to the port wall. This ok?

 

[SpeedEuphoria 10+ year member]

does the sub have a pole vent?

I dont think the subs being as close to the port is the biggest deal. Meaning I dont think you'll have to get 1" close, just instead of centering them , skew them more "towards" the port then centered or the other side. Even since you want them to have space around the back of the sub so its not right against the side wall(especially since its 3" to the back)

For your application it may work best to have the single large port in the middle??. You would loose a touch of internal volume due to little extra wood having to make more of a "T" shaped port

Just remember with a box that big and subs that big, your going to want a double baffle, and plenty of bracing which will eat into internal volume also

 

[DUAL10S 10+ year member]

ok, I'll go back to the drawing board with the "T" shaped port. This is basically what I have in mind from the first post, just need to adjust it to be one port instead of two.

When you say double baffle are you talking about double thickness (1.5") on the front?

I see what ya mean by loosing internal volume quickly - I did not figure in any bracing //content.invisioncic.com/y282845/emoticons/frown.gif.a3531fa0534503350665a1e957861287.gif............... I really want to stay under the rear window but I may have to give an inch or two.

anyway, I will refigure and check back in

Thanks again

 

[DUAL10S 10+ year member]

I gave the box a little height and came up with 16.17 cubes

Quick observation - I notice when making the port width narrower the overall length shortens.

If I take the port width to 4" that gives me a length of ~12.75" (eliminate the "T" port)

Port width of 8" gives me a length of ~30" (will have to make the "T" port)

Any suggestions on this?

Also, when making the "T" port (8") - I get 13.25" on "l" part of the "T" / How would I figure the length on the top part of the "T"? Do I just split the 16.25" off of center?

I know I am being a pain but I do appreciate all the help.

 

[DUAL10S 10+ year member]

Also, when making the "T" port (8") - I get 13.25" on "l" part of the "T" / How would I figure the length on the top part of the "T"? Do I just split the 16.25" off of center?

nevermind on that part. Its the same either way.