add an aeroport... or increase the lengths?

[Thewes 10+ year member]

I am working on an enclosure for an 18 lms ultra, and I have a couple simple question for you guys...

Enclosure will be 8^3 after displacement @ 27hz- but the thing is, I can either use 3 four inch ports at 15.5 inches, or I can use 2 four inch ports at 9.7 inches, both bring me to 27hz tuning. Am I completely missing something here? Or would both sound relatively the same, just adding one would just cost me 20 more bucks? This is all through psp inc calculator. I have built about three other enclosures with aeroports and assumed they figured in port displacement, maybe I'm wrong...

Appreciate the help.

Click to read more...

 

[CRXBMPN 5,000+ posts]

id use the three ports, you need at least that for an 18. my RE MT 18 had four 4" aero's in the box.

 

[Thewes 10+ year member]

See I thought about that but they would end up being around 21'' long, and to do that I would have to buy more thin walled couplings/pipe from psp - more $$$

 

[mazdakid 5,000+ posts]

even 2 6" aero ports would kinda be small for that box

id use 5 or 6 4" if you have to stay with 4"

 

[Thewes 10+ year member]

Are you sure you know what your talking about here? 5 4'' ports would be 27 inches long flared length... thats a bit too much. But you are right to an extent, I do need the correct port area.

 

[mazdakid 5,000+ posts]

Well i wouldnt go with 5 4" ports, i said if you had to stay with 4".

Id go with 3 6" aero ports if i was going with aeros

So because theyre long means i dont know what im talking about?

lol are you sure you know what youre talking about trying to use 2 or 3 4" ports for a sub like that?

 

[CRXBMPN 5,000+ posts]

you'll need extra port pieces if you want anything over the standard 16" unless you go out and buy some white pvc and cut it to length...

 

[Thewes 10+ year member]

I usually just kept everything within the 18'' that the kits came with and never really ran into any problems doing that. I don't know what effects come from having lower port area, but can't be too serious speaking almost all my old enclosures must of been drastically short on port area and sounded great.

I am aiming for around 80 inches of port area with the lms at 8 cubes

 

[Buck 5,000+ posts]

That's the minimum I would do, 3 4" aeros.

 

[mazdakid 5,000+ posts]

3 4" aeros isnt even half of the area youre aiming for.

 

[Buck 5,000+ posts]

3 4" aeros isnt even half of the area youre aiming for.

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I don't think you're doing it right...

 

[mazdakid 5,000+ posts]

12.5x3=37.5

what do you get?

 

[CRXBMPN 5,000+ posts]

mazda is right, if he wants 80sq in of port area he needs like 6-7 of those things... a big old slot port would probably work better here.

 

[Buck 5,000+ posts]

mazda is right, if he wants 80sq in of port area he needs like 6-7 of those things... a big old slot port would probably work better here.

Ah, didn't see that part.

 

---------- Post added at 04:13 PM ---------- Previous post was at 04:12 PM ----------

 

He doesn't need 80 square inches of port for that box, not even close to that.

 

[mazdakid 5,000+ posts]

2 6" would work but i wouldnt use 3 4" for that sub in 8 cubes