15mm Diameter Port?

I've recently come across Beyma's 6NFMW and just did input it's specs to calculate box and port size.

Fs: 40Hz
Qts: 0.34
Vas: 11L
*Port Length: 18mm (Working with this just to match the standard thickness of MDF/Plywood)

The program came up with a 14.5mm port size.
What I wanted to know is if this will cause any resonance or muddiness as the air travels out. I've yet to see a bass reflex speaker with a port so small so I am questioning whether it's something that shouldn't be done.
 

Attachments

  • Screenshot 2023-08-11 at 7.55.20 AM.png
    Screenshot 2023-08-11 at 7.55.20 AM.png
    25.6 KB · Views: 52
I ran the simulation with this driver & I'm guessing you had entered some data wrong...First "As suggested" simulation. 6.3 liters, fb 47.65, -3.03db@ 50.23 hertz, Second simulation "tweeked", Ten liters, fb, 46 hertz, -3.03db@ 43.2 hertz, A port 70 mm diameter, 484mm long.
Now I noticed the sizing of the ports seemingly shifted from Millimeters in diameter to Meters in diameter...not noticing, I thought the first recommended alignment had me a port that was 1.6 meters long...???


------------------------------------------------------------------------------------------------------------------------------------------------------Rick...
 

GM

Member
Joined 2003
Well, with such a short vent length in a tiny box tuned to < Fs it's going to be tiny in diameter and need to be heavily damped to keep from being a whistle, i.e. basically lossy sealed once dialed in to 'taste'. ;)

As s general rule for modest power requirements, vent area (Av) = driver area (Sd)/4 and higher power at least (Sd)/2, which as RE pointed out is going to be long to the point where it's better to use some form of TL alignment in such applications.
 
The trick is knowing real world power levels.
Then aiming for velocity to be around 18 to 22 m/s

At those power levels.

The driver doesn't need much more than 6 to 8 liters
So it would be difficult to get any port length that works
in such a small box. To obtain 40 to 45 Hz tuning.

Assuming your at 100 watts or at thermal 200 watts.
Would be close to impossible to get a port in 6 liters

Back to reality actual power be 15 to 50 watts.
So your still dealing with a small diameter , long port.

Would say the seemingly high xmax should be considered
good amount of room for adding lots of EQ not power.

Could be used in sealed midbass, or also a mini tower
So a pair could be used in 12 to 15 liters. Bigger box gives you room
for longer ports.

Extended bass shelf also a option since that volume is closer
to 12 liters as well for single driver.