How much port area for an 18?

[Souldrop]

I love technical posts like these. I'm going to have to look up the derivation of small's formula. I wonder if it was a full derivation or partially extrapolated from data.

[Jd1102]

But doesn't higher port velocity yield a higher SPL score on the meter?

I'm pretty sure that it doesn't get you a higher score. Its just creating port noise and excessive turbulence in the port that can effect the performance of the sub negatively, it should be more efficient without port compression. The only benefit from a small port and high vent mach is that normally the exchange of air in and out of the box would be about the same, but if you have too little port then there will actually be a small exchange of air, which could possibly help with cooling the sub(s) by replacing hot air with the ambient air. However this is not a good excuse to intentionally make a small port, the system will be both more efficient and sound cleaner with the proper port size.

Well, Im looking to design a port for our astro van. We already have a wall behind the 3rd row bench seat. the box is ~12.8 cubes gross. The box is setup for 2 18s. They are sundown zv3 18s. My problem is- i dont know the xmax of the subs.

ask In sundown thread?

well, i didnt know if there was a method. I looked on sundowns site to find nothing. I will ask in one though

I don't know if there's a method or not there might be. But I do know someone in the sundown part will know the xmax so u can plug it in the formula

[Rail]

Well, Im looking to design a port for our astro van. We already have a wall behind the 3rd row bench seat. the box is ~12.8 cubes gross. The box is setup for 2 18s. They are sundown zv3 18s. My problem is- i dont know the xmax of the subs.

The Z v.4 have an xmax of ~35mm by 70% Bl, and a total mechanical clearance of 62.5mm in the motor. the Z v.3 had slightly less xmech, closer to about 50mm. The xmax was probably about 33mm but it wouldn't be a bad idea to check on the Sundown section.

I love technical posts like these. I'm going to have to look up the derivation of small's formula. I wonder if it was a full derivation or partially extrapolated from data.

Same here, car audio is practically a science. The calculations allow you to do less experimentation/trial and error. It's interesting to plot different woofers in WinISD to see how they behave in different types of enclosures (even though cabin gain is not taken into account).