1 18" sub/28mm x-max @ 33.87HZ:

Minimum Area 145.47"

Length of a side
for a square vent 12.06"

UUUUHhhhh??? Fi says 12-16 per cube..... what does this mean?

 

It means fi, like every other manufacturer doesn't want to scare off consumers with the actual port dimensions that a properly designed sub system requires.

 

^^^ exactly, & it can play in a bigger box than they want to let on (9-12 cubes might scare some buyers away, but if you want the lows...) using that port area. Then you have your 12-16in per cube.

This is why some people are louder with smaller subs. They are able to build the proper enclosure.

Is this a BTL?

 

^^possibly...they do recommend 5-10 cubes (assuming a btl 18 or a q), though at 5 cubes it would be off a little. Anyway, that's optimum, and unless you have gobs of space you're going to have to compromise a little.

 

BTL 18. I want one sub & one amp, something cheap & really loud.

For 145.47"^3 port area, how big can the box be? 140"^3 = 8.75cf3 per 16"^3. How much port area is too much?

I have 10.40625 cf3 as a sealed 38 x 20.5 x 29.

18.5" x 7.87" port = 145.595... which gives me 8.81 cubes @ 38.54-56 HZ (17 actual/calculated 20 port length), 16.51 square inches per.

Why do ported boxes suck so much?

 

Does the minimum mean it won't reach full excursion in any airspace without 145.47" port area?

 

The port would need to be 13.61 x 10.7 that just doesn't make sense. How could a 12" need a minimum vent diameter of 7.91"?

 

12"? I thought it was an 18"? Anyway, it all has to do with diplacement over time and how that relates to the air speed within the vent. I haven't bothered to figure out the speed limit they are using but common rules of thumb limits it to 0.9Mach to avoid having a noisy port with a lot of compression.

Contrary to what many people think, you CAN have too much port area, but most people except SPL competitors won't run into this.

 

Yes, it's for an 18, but even for a 12 it seemed too high. Sorry, that was minimum area, not diameter.

"...diplacement over time...", as in motor-force?

Does 145.47 square inches of port mean that around 9 cubes would work best? 9 x 16 = 144.

Would a sub with lower x-max work better? The BL calculates to around 93 minimum vent area.

What's the xmax on the BTL without the high x-max coil?

This box seems like it's going to be a hell of a lot longer.

 

Can someone design me a correct port area for 30-35hz with 38w x 20.5h x 29+1d? Both sub & port on 38w.