Round port port area, needs-Port Area per Foot a Concern

[mdwerner6942]

I am looking at a 18 dual 2 ohm sub, box net 6 cu or little over, just not sure 6" Aero ports are less flexible and more expensive, vs say 4" PVC port etc. I believe Precision port said it takes 3 x 4" ports to improve over one 6" port, and PVC is very inexpensive and easy to adjust as needed. The 6" aero ports that I have are 17" but told only 16" counts due to aero design. Port area needs do I need a specific amount with round ports been told aero it is not as important. I have been looking at Q 18, BL has less Xmax, then there is the Xcon, not sure if I need as much as the Zcon subs offer but SSA and Q have more Xmax than the Bl not sure what the flat coil does if anything to specs.

I know guess some do not like ported and like a sealed saying it has a better sq, but I had good luck with a good sub in a ported box and get close to 1 18 ported of others with two woofers in sealed box when tuned right. But guess that could be because of the subs I have had limited experienced too, but all my home speakers are ported and have no complaints of too much boom and always can reduce things but not so easy to increase something that is not there. Sorry if this is a dumb question to more experience box builders, but it something I was wondering about and if a issue, how much guess would be needed in port per sq inch in a round port, be hard to get in the 16 area etc.

Guess years of larger subs sort of grew on me, home 12 sub aero port seems to be cool, but ones I had in port through on my truck, was not as good of experience and box sort of lend it's self to work well with a 18 unless this port issue is a issue to help keep piston compression out of the equation.

[Krakin]

Port per cubic foot is not as useful with modern subs with gigantic X-max's.

Port area is determined based off of cone area, X-max, and tuning frequency. It doesn't matter whether the sub is in 4 cubes net, or 8 cubes net, it will still need the same amount of port area.

You can use this as a quick calculator, or you can get the formulas from the same site.

http://www.carstereo.com/help/Articles.cfm?id=31

[coh33dkill3r]

I use 2 6inch aeros that I made from metal for my x18 and it does the job

[mdwerner6942]

Port per cubic foot is not as useful with modern subs with gigantic X-max's.

Port area is determined based off of cone area, X-max, and tuning frequency. It doesn't matter whether the sub is in 4 cubes net, or 8 cubes net, it will still need the same amount of port area.

You can use this as a quick calculator, or you can get the formulas from the same site.

http://www.carstereo.com/help/Articles.cfm?id=31

I will try that again, we had planned on 4 4" round ports or 2 x 6" aero ports, this will help thanks. I was not sure when there before how it worked so will revisit site, been a while since I did this. Now in a small rural town of 6500 there are just no shops like when we lived in Sacramento. 4" would be easier to re tune, 6" aero port come believe 17" long. Not sure if 5 4" which we have pvc, or 2 x 6" aero which I guess you can go a little less with, but if tuned lower 6" harder fit, 17 only 16 is used due to aero from what I read on precision port's site.

[ChevyBoy95]

I would do 2-3 6" PSP aero ports... yes they are expensive, but they look good, and perform even better, plus if you router out the mounting surface about 1/8", they will sit flush and look really clean.

Only thing better on the market in that department is pshycoacoustics aero ports.

edit: i have used them and was more than happy with the results..... plus testing has shown that lesser amount of ports you have the better (on the meter generally) iirc. so 2 6" aeros > 4-5 4in PVC tubes

[Krakin]

When building a ported enclosure keep the length of the port 1/12^th or smaller than the wavelength that you are tuning to. Once you exceed 1/12^th the length the air inside of the port does not act as a single mass and will "lag".

With how important port area is to keep from having port noise I would rather stay below 1/12th the length rather than have the larger port.

An example oh how to find the maximum length, I would recommend, would be as follows. The speed of sound travels at 1116 ft/s. The frequency you are trying to tune to is 30 Hz. To find the length of this wave you simply divide 1116' by 30 Hz to get 37.2' for one wavelength. To get the length of 1/12^th of that you divide 37.2' by 12 to get 3.1' or 37.2".

3.1' is the longest of a port tuned to 30 Hz that I would recommend building.

[mdwerner6942]

When building a ported enclosure keep the length of the port 1/12^th or smaller than the wavelength that you are tuning to. Once you exceed 1/12^th the length the air inside of the port does not act as a single mass and will "lag".

With how important port area is to keep from having port noise I would rather stay below 1/12th the length rather than have the larger port.

An example oh how to find the maximum length, I would recommend, would be as follows. The speed of sound travels at 1116 ft/s. The frequency you are trying to tune to is 30 Hz. To find the length of this wave you simply divide 1116' by 30 Hz to get 37.2' for one wavelength. To get the length of 1/12^th of that you divide 37.2' by 12 to get 3.1' or 37.2".

3.1' is the longest of a port tuned to 30 Hz that I would recommend building.

I will keep that in mind, just heard friend has a box 26.5x25x19 with 3 4” ports believe he said 17” long. Subs around .25 or .26 displacement, going to check it out, but all it needs was some cleaning up, cover or painted but son said he used it and it had no leaks, could be safe just re-seal some area paint it, cost would be $30 and some work. Check specs and port length see if I can work with it, .75 MDF - It is not a pre fab. PVC just called and rounded edges, will see. Not sure what the 3.1 or 37.2" reference too total port area like Torres has a total port area which would guess mean a single 6" aero port might work?

[mdwerner6942]

When building a ported enclosure keep the length of the port 1/12^th or smaller than the wavelength that you are tuning to. Once you exceed 1/12^th the length the air inside of the port does not act as a single mass and will "lag".

With how important port area is to keep from having port noise I would rather stay below 1/12th the length rather than have the larger port.

An example oh how to find the maximum length, I would recommend, would be as follows. The speed of sound travels at 1116 ft/s. The frequency you are trying to tune to is 30 Hz. To find the length of this wave you simply divide 1116' by 30 Hz to get 37.2' for one wavelength. To get the length of 1/12^th of that you divide 37.2' by 12 to get 3.1' or 37.2".

3.1' is the longest of a port tuned to 30 Hz that I would recommend building.

I guess 3 -4" aeros 32 Hz area get lag, was not sure how that works saying to stay under 37.2 port area, guess over my head been a while since college etc.

[mdwerner6942]

Port per cubic foot is not as useful with modern subs with gigantic X-max's.

Port area is determined based off of cone area, X-max, and tuning frequency. It doesn't matter whether the sub is in 4 cubes net, or 8 cubes net, it will still need the same amount of port area.

You can use this as a quick calculator, or you can get the formulas from the same site.

http://www.carstereo.com/help/Articles.cfm?id=31

http://www.psychoport.com/ little expensive

[john253a]

Personal

I like the fiQ

7.5-8 net

With 4off 6" flared aeros

At 28-30hz