Port Area Trials...

[iLL Ridge 10+ year member]

So I built a box for 2 xfl 10's.

Subs and ports Up.

Powered by maybe 600 watts per woofer.

Box is double baffle. roughly 4 cubes gross ~ 3.4 net.

Removable port baffle.

Originally used 2 - 3" round ports x 12" long/ no flares.

Tuning calculated@ 27hz.

The 3" ports sounded great in my suv.

It KILLED the lows....

It is low on port area, I had severe port chuffing.

Changed ports out to 4" round. 13" depth. Tuning calculated to be@ 34hz.

No port noise..... but I lost the low, lows.

Strangely, even so, it seems like the smaller ports were louder overall.

That may be just subjective though, not sure.

Click to read more...

 

[iLL Ridge 10+ year member]

I'm going to try and lengthen the 4" ports to 18" .

That should bring the tuning back down to 30hz.

Hopefully that will do it.

My question is, I had a another box for a single 10.

2 -2 x 12 inch aeros in 1.2 cubes. That's still very low on port area, especially with 1k watts+.

.....But It slammed!, Could not detect any port noise, and the lows were Heeeaavy!

In the small box, did the aeros make that much of a difference in port noise/velocity/turbulence???

Also with that little amount of port area, was I having port compression?

Will I have port compression with non-flared 4 inch ports?

 

[BOOMINGRANDPA 5,000+ posts]

good looking box.. flared port certainly has less noise idk that they can change the compression. 2-2" not as good at 1 4" yeah but for 1.2cf it's a tad less port than u want but flared i think they say 8-14 sq per cf., so should be good on that 1

 

[BOOMINGRANDPA 5,000+ posts]

i meant to say the single 10 box was good the dual 10 3.4cf u have only 6sq in port per cf thats not enough,, i'm gonna try old 10 on wins list see what it looks like........... oh man i just modeled some old rf subs and at 3.4ad with 700watts listed (after rise) port air velocity showing 145 fps u want about 1/2 that., it's not good man sorry..

 

[Jeffdachef 5,000+ posts]

i meant to say the single 10 box was good the dual 10 3.4cf u have only 6sq in port per cf thats not enough,, i'm gonna try old 10 on wins list see what it looks like........... oh man i just modeled some old rf subs and at 3.4ad with 700watts listed (after rise) port air velocity showing 145 fps u want about 1/2 that., it's not good man sorry..

gramps just NO... just no... lmao... You dont model rockford subs and tell him his sh*t doesnt work when his results say differently. You arent helping anything here. Leave the getting loud advice to people who know what they are doing please.

 

[Jeffdachef 5,000+ posts]

I'm going to try and lengthen the 4" ports to 18" .That should bring the tuning back down to 30hz.

Hopefully that will do it.

My question is, I had a another box for a single 10.

2 -2 x 12 inch aeros in 1.2 cubes. That's still very low on port area, especially with 1k watts+.

.....But It slammed!, Could not detect any port noise, and the lows were Heeeaavy!

In the small box, did the aeros make that much of a difference in port noise/velocity/turbulence???

Also with that little amount of port area, was I having port compression?

Will I have port compression with non-flared 4 inch ports?

Can you do an octoport? a single 5.5 diameter port would be under the threshold of port noise. If possible have the port fire to the rear or side... If you are firing up, make sure its long enough so the port is very close to the roof if you want lows and proper loading.

To explain your results, this is why we design boxes around the power you will use. Those XFLs with low power will require much less port area to get loud because they arent building enough pressure. However when you put more power onto them, the port you need to use will need to be much bigger to accomadate or else you run into both noise AND compression AKA you wont get any louder when you throw more power onto them.

With it stands now, if you want to get loud with those 4 inch ports, you'll need to throw 1500 rated watts per woofer or about 800 clamped in order to get louder output. OR you make the box bigger if you want lows. More power you have, the more air will be displaced which means you need a bigger hole to breath. However if you dont have much power and too big of a hole, you arent building up any pressure.

This is why you usually dont follow the port per cube rule to the teeth, thats just a general guideline for noobs. The actual numbers can vary greatly depending on driver parameters, power and other factors.

 

[hispls 5,000+ posts]

This discussion is absolutely worthless if you don't own an SPL meter or RTA and graph your output/frequency response.

Or simply state "lower tuning sounds better to me".

 

[iLL Ridge 10+ year member]

Lower tuning DOES always sound better to me.

I seem to like lower than recommended port area in ALL of my boxes.

What am I sacrificing by using small port area?

Also remember.... The 4 inch ports are for the 3.5cu ft net box.

That's still only 7.2 sq in/cube

 

[kr15 5,000+ posts]

Aeros can do 7.2^2 ok on low power. Not ideal for very high xmax drivers like the new sundown platforms, but ok for most subs.

 

[iLL Ridge 10+ year member]

ok, so I switched out the ports.

Went with 2-4 inch x 19 inch no flares.

Tuning calculated @ 29hz

Had to flip box facing rear hatch to fit ports.

Gets down pretty good.

I still drop off at 23-22 hz though.

I'd like to play flat from 19-40.

Pretty loud and stout though, It's probably as good as it's going to get without getting too bottom heavy.