Slot Ports vs. Aeroports

[THATpurpleKUSH 5,000+ posts]

ahhh. ok. hm....maybe I should look into some aeros or what about kerfed ports? I mean, is thats still better than just a regular slot port right? in terms of least resistance to air flow?

Kerfs are definitely a step in the right direction, but it all goes back to my pipe theory and that is pipes are round for a reason. Round ports work well up to a certain amount of square inches of opening per cubic feet, after that the necessary length becomes unfeasible for the build. Someone earlier touched on this, but it was worded sort of differently.

 

[Kangaroux 5,000+ posts]

I prefer slots...some people think they are bad to use when you wanna do tuning and cut down on the port, but it's not hard at all if you just make it removable (which is very easy to do). I tried out an aero port on my box because I had never used one before but I wish I would have done a slot port instead. Plus, with a slot port it's very easy to adjust port area. With aero ports if you wanna fine tune it you are pretty much stuck with adding a lot of smaller ports to achieve your desired sound (i.e. to get somewhere between 6" and 8" you need 3x 4" ports which is costly).

 

[knotdrummer88 10+ year member]

Kerfs are definitely a step in the right direction, but it all goes back to my pipe theory and that is pipes are round for a reason. Round ports work well up to a certain amount of square inches of opening per cubic feet, after that the necessary length becomes unfeasible for the build. Someone earlier touched on this, but it was worded sort of differently.

ok, well if i did a kerfed port how do you calculate the curved part when trying to figure out dimensions and tuning and stuff? like, where with a slot port its just straight forward, but how would you figure the tuning with a kerfed port?

 

[Falcons 5,000+ posts]

You aren't using an aero, you are using a plain round port. True aero ports have flared mouths.

Yeah I know but it's the same concept.

 

[RAM_Designs 5,000+ posts]

ok, well if i did a kerfed port how do you calculate the curved part when trying to figure out dimensions and tuning and stuff? like, where with a slot port its just straight forward, but how would you figure the tuning with a kerfed port?

Stop measuring length half-way down the curved section, and you're good to go.

 

[THATpurpleKUSH 5,000+ posts]

ok, well if i did a kerfed port how do you calculate the curved part when trying to figure out dimensions and tuning and stuff? like, where with a slot port its just straight forward, but how would you figure the tuning with a kerfed port?

Honestly I have no clue, never done a kerf port

 

[knotdrummer88 10+ year member]

Stop measuring length half-way down the curved section, and you're good to go.

so you wouldn't measure the length all the way to end of the opening?

 

[Moble Enclosurs 10+ year member]

To me, the main limitation of the aeroport is that it allows for less control of the output. When I mean control, I mean the group delay, excursion, etc. Aeroports are great for SPL designs where compression is the key, but for musical output, slot ports can be manipulated much more easily to obtain a certain response curve. Aeros are great, and if the output matches that of a slot, the audible differences can be tough to point out at times, and for those who do not care to notice those differences, it then becomes more of a personal preference and involving physical limitations that need to be accounted for more so than the acoustical control. I prefer slot ports for that reason mainly. I might write up a blog about this in detail with all of the advantages/disadvantages of each including some that people do not notice to the ear.

 

[Moble Enclosurs 10+ year member]

ok, well if i did a kerfed port how do you calculate the curved part when trying to figure out dimensions and tuning and stuff? like, where with a slot port its just straight forward, but how would you figure the tuning with a kerfed port?

As far as tuning goes, normally it depends on the expansion rate and cutoff frequency. The cutoff can be determined by adding the lengths on all sides together and using the distance-frequency formula to get cutoff. You can effectively use the quarter wave cutoff for subwoofer use.

Length is determined by the entire length of the kerf with the port because every inch of it makes a difference. By stoping halfway down, you eliminate the accuracy of the cutoff at full flare and regard the effects it causes on the response. You have to use the entire length and account for the opening at the end of the port. If you stop halfway, you increase the cutoff frequency and cause inaccurate response curves to be calculated.

Tuning can be a figured mean of the constant length into the cutoff frequency. So, a port that is tuned to say 30Hz may be tuned to 27-28Hz with an added flare with a cutoff of about 70Hz quarter wave. The calculations involved in this are too complex to write down and explain here.

 

[Moble Enclosurs 10+ year member]

As far as tuning goes, normally it depends on the expansion rate and cutoff frequency. The cutoff can be determined by adding the lengths on all sides together and using the distance-frequency formula to get cutoff. You can effectively use the quarter wave cutoff for subwoofer use.
Length is determined by the entire length of the kerf with the port because every inch of it makes a difference. By stoping halfway down, you eliminate the accuracy of the cutoff at full flare and regard the effects it causes on the response. You have to use the entire length and account for the opening at the end of the port. If you stop halfway, you increase the cutoff frequency and cause inaccurate response curves to be calculated.

Tuning can be a figured mean of the constant length into the cutoff frequency. So, a port that is tuned to say 30Hz may be tuned to 27-28Hz with an added flare with a cutoff of about 70Hz quarter wave. The calculations involved in this are too complex to write down and explain here.

And the differences with the size kerfs we use may not be as important as you may think when the box is then loaded into a vehicle where gain takes control of those changes and changes everything again lol

 

[Boomsday 10+ year member]

If you ballin you have aeros

 

[wenn_du_weinst 10+ year member]

As far as efficiency goes, I like to think of it like this...how many round drains do you see vs how many not round drains do you see? Its all about fluid dynamics. I have only built 1 slot ported box so I am heavily biased towards round ports. The only time they create a problem is when you try to adapt a large amount of port area to a small volume, this usually happens when dealing with the high output small cone diameter drivers like the sa8 that are increasing in popularity.

have you never looked at a gutter?

 

[THATpurpleKUSH 5,000+ posts]

have you never looked at a gutter?

gutters arent pressurized

 

[knotdrummer88 10+ year member]

And the differences with the size kerfs we use may not be as important as you may think when the box is then loaded into a vehicle where gain takes control of those changes and changes everything again lol

I WANT to understand this! ahhhh

 

---------- Post added at 09:23 PM ---------- Previous post was at 09:23 PM ----------

 

I WANT to understand this! ahhhh

well the whole thing, I meant to quote the entire post

 

[2RZ-FE 10+ year member]

I have to disagree completely on the ease of use with smaller volume boxes. With a .5ft^3 box tuned to 35hz, a 3" aero is going to need to be 30" long. Have fun buying elbows and more PVC to fit that inside a box or you can have an ugly external aero hanging out of the box, taking up a lot of space. With a slot, you can easily follow the outside of the box and get the port length needed. Also, using a 3" aero that has a ~4.5" diameter flare is going to require a decent sized box just to make sure you have enough clearance with the port/sub being so close. With that 30" custom aero, it's doubtful you can even fit it inside a box(depending on the sub/port orientation that you needed to do) and still keep your .5ft^3 net volume that you'd be after.
Basically, with a smaller box you're going to need a longer port. And using a smaller volume while trying to tune any lower than 35hz with aeros is going to require you to make them a custom length, which adds to the cost as well. It would be much easier to use an aeroport on a lower power, more efficient setup that utilizes a larger than normal box volume. That way you could rely on a shorter port length and not have to worry as much about internal clearances.

I'm building a box like this. Can you help me understand why i can't do like a 2" x 12.35" port instead of the 3" x 30"?