Port Length Verification Help

[Freudie1]

Just wanted to run these calculations by some of the more seasoned enclosure builders.

 

Scenario:

 

2 Fi Audio "Halcyon" 15"s.  These are massive.  I consulted with Fi and they recommended tuning to 32 Hz with 60 sq in of port area and 4 cu ft of enclosure  (each).

 

Running the #s I come up with:

 

8 cu ft box ( overall, I realize I have to account for displacement of the ports and the subs).

 

4 6" aero ports ( pi r 2 = 3.14 x 9 = 28.26 sq in per 6" port.....so 4 x 28.26 = 113 sq in of port area).  While I realize this is LESS than the recommended 120 sq in of port by Fi, running the scenario through Triticum's spreadsheet it results in a minimum of 109 sq in of port required.  Running the #s through the PSP aero port length calculator I come up with a length 33.81 inches per aero port.

 

Since all car audio systems are an exercise in tradeoffs and compromise here are my questions:

 

Am I correct in my math/calculations?  In other words, I come up with need 4 6" aero ports at 33.81 inchs per port.

 

Should I fret over the missing 7 sq inches (if I go with this plan of 4 6" ports) or should I consider adding a 5th 6" port?  <--I'm running out of real estate which is why I'm hung up on 4 6" ports.

 

Reading the forum, it looks like I can introduce a bend of 90 degrees or less in each port with no ill effects.  True?  Ideally I'd need close to a 90 bend in each port so I can make this fit (the box is going to be about 16" wide, subs will be "elevated" via the use of fiberglass to make this all fit firing up).

 

Seems like my port lengths are VERY long, but then again this is a lot of cone area with a fairly low tuning frequency.  Thoughts?

 

 

Edited October 29, 2023 by Freudie1

[Joe X]

8 net @32Hz , 4x6" ports 33 long each seems ok.

 

Turning the ports is OK as long as you use fittings.

 

The question of needing more or not port area depends on power, I imagine Fi gives those numbers for rated power, if you are keeping at or under rates power you should be ok. if you will be running 10-20% over rated power then you may need more port area.

[Freudie1]

11 minutes ago, Joe X said:

8 net @32Hz , 4x6" ports 33 long each seems ok.

 

Turning the ports is OK as long as you use fittings.

 

The question of needing more or not port area depends on power, I imagine Fi gives those numbers for rated power, if you are keeping at or under rates power you should be ok. if you will be running 10-20% over rated power then you may need more port area.

Appreciate the cross check.  Was questioning using ports of such long length, but with a bend (yes using a pvc coupler/fitting) I believe I can make 4 fit if I design it with 2 ports per side and then angle them internally with the bends.

 

"Rated power" is a mystery with these as they are one-offs from Fi and when I asked for specs they wrote "I’m sorry, but we never broke one in to pull good specs.".  Best I can find is they are based on their older "Omega" line which MIGHT have been 4500 as they wrote "The power rating of 4500W is a base rating that in testing were simply could not hurt it in any way. This is not to say that this is its “rating”. "  Joys of "limited edition/never going to make these again" subs I suppose....

 

At any rate...I am powering these two with a single Orion HCCA 3000.1 DSPLX (latest version) which going by the Williston video of that amp presenting a 1 ohm load (yes I know about impedance rise, but let's go with known #s here), he tested 4825 watts certified/1%thd and 7673 burst/dynamic....point being I think I am well under the "rated" combined 9000 watts (which once again is probably conservative at best based on Fi's cryptic commentary).  Not chasing SPL #s here, just want a very fun daily enclosure (and I can't physically fit any larger sub amp at this point without ruining the cosmetics of the install in this truck).

 

 

 

[Joe X]

No parameters for that sub so I can't give you further feedback unless you have them.