Curious, as anyone else seen a lot of box builders and designers using aero port areas equivalent to square or slotted port area?

I was under the impression that the agreed upon rule of thumb was that you can use .56% less area while achieving like results.

Within this practice, I find myself believing that if one were to use equal, that in theory, they are increasing their port area by, .56%

I also lean toward this thought, if you correctly designed your enclosure and its port, based around the mathematics and t/s parameters of your driver, and chose to not use the formentioned rule of thumb,when using an aero port, that you have given too much port area to your design.

I see similar folks, choking the box down, saying it seems a tad too big.....yet, they supposedly designed it spot on.

The experiences I am reffering to, and the folks doing the designs, leave me thinking that their sub does not like the port more so than the volume.

Let me say, these folks compete and build a lot more than I do. I am not attempting to take away from their successes. I understand some times adjustments are needed.

I am just wanting to confirm that my understanding is streamline of what is most accurate within port calculating, I mean, for a large part, these fellars seem to be left out in left field when I mention some of my learnings found in these pages on ssa as well as in other reading material I have.

Do a lot of you, find folks who do a lot of designs, yet appear to be clueless on dome of these basic theories?

Is ol chop just way out beyond left field?

Sure have read a lot that would suggest I am close within my approach.

Some recent attempts to help a guy design a box in a undisclosed conversation, these folks came off like a seriously intoxicated game of blind folded darts....

They were sorta just throwing numbers as fast as they could to trump the next guy.

I guess I am wondering if I put too much into my designs, or, perhaps others are not putting near enough into their designs.

Sorry for the wordy question, in rant form....

I truly would like to nail the topic down to, should aero ports use .56% less port area than square/ slotted ports, always?

I am basing this question on the understanding that all previous equations have been observed mathematicly speaking.

Thanks for your input

Chop

Port area is port area.

The reason why people can often use less port area with an aero verse a slot port is because the flaring of the aero ports reduce turbulence, and may reduce port compression.

Also: 0.56% is less than 1%. A 1% decrease in port area isn't going to make a hell of beans. Perhaps the "rule" was 56%. In either event it sounds dumb to me.

Edited October 26, 201212 yr by stefanhinote

No. 99.9999998% of rules of thumb are ignorant

There is math behind everything. Just like there is a formula for calculating BL of a sub there is a formula to calculate port area. It is all derived from physics.

Just like air plane wings are different so are port chamfers and there are formulas based on fluid dynamics to calculate them.

Rules of thumb are usually based off theory, and they are theories for a reason...each design is different and will call for different specs. As for designing, I don't do any graphing or T/S spec testing before hand and I've never had a box that didn't work well. You can test as much as you want but common sense and fundamental knowledge of acoustics and physics will go much further imo...

Bracing for the onslaught of replies about how not graphing the box first is stupid

Rules of thumb are usually based off theory, and they are theories for a reason....

No, rules of thumb are approximations that morons always misapply. There is not a rule of thumb in car audio that is correct. Anyone who states one is someone whose advice you should ignore.

....You can test as much as you want but common sense and fundamental knowledge of acoustics and physics will go much further imo...

I have no idea what you are saying. How do you think that these theorems were proved? By testing. Sure once mathematics are proven you don't need to verify ALL the details but if you don't apply a rudimentary understanding then even applying the physics in the first place is wrong.

And Chop, it's REALLY simple. Your port shouldn't exceed a port velocity that bothers YOU. You can surely measure what YOU don't like and EASILY apply it to either slot, aero, or round ports.

Rules of thumb are usually based off theory, and they are theories for a reason....

No, rules of thumb are approximations that morons always misapply. There is not a rule of thumb in car audio that is correct. Anyone who states one is someone whose advice you should ignore.

....You can test as much as you want but common sense and fundamental knowledge of acoustics and physics will go much further imo...

I have no idea what you are saying. How do you think that these theorems were proved? By testing. Sure once mathematics are proven you don't need to verify ALL the details but if you don't apply a rudimentary understanding then even applying the physics in the first place is wrong.

And Chop, it's REALLY simple. Your port shouldn't exceed a port velocity that bothers YOU. You can surely measure what YOU don't like and EASILY apply it to either slot, aero, or round ports.

I should have been more clear on that last part...I meant testing via graphing things in a program such as winisd. No program can account for every variable which is why I find the graphs can be very misleading. Sure it's a rough idea of what you're getting but between cabin gain and how you actually decide to lay out the sub and port will make a drastic difference in what that graph actually comes out to be. We've had this convo before and it just goes back and forth so let's just leave it at that, cause frankly I'm tired tonight and don't feel like typing anymore lulz

I should have been more clear on that last part...I meant testing via graphing things in a program such as winisd. No program can account for every variable which is why I find the graphs can be very misleading. Sure it's a rough idea of what you're getting but between cabin gain and how you actually decide to lay out the sub and port will make a drastic difference in what that graph actually comes out to be. We've had this convo before and it just goes back and forth so let's just leave it at that, cause frankly I'm tired tonight and don't feel like typing anymore lulz

Analytical work is the opposite of "testing". You do NOT test by making graphs in WinISD, that is modeling. Modeling is NOT test. And another big no, a program can and surely will account for every variable. Of course that requires a user that knows a shit about how to model. Most don't. The problem is the user, not the software. WinISD is a great example. You can load correction curves into it, if you don't you surely shouldn't blame the software. The only thing that changes are the boundary conditions and they can most definitely be compensated for. Of course that doesn't mean you should just use the curve response as is....unless of course you understand fundamentally the difference between free air and a constrained environment.

Well, I indeed enter the wrong number value.

I should of stated 56% less, laugh out loud at my goof there.

Thanks for the input.

Five, thanks, the simplest and easiest way to say it for me

If I have not lost you with the dullness of this...

I would like to know your input on a question I had, still port related.

Not sure how to start in this.

The rear of my port, a center port, rectangle, standing tall, is in front of a concave surface. Thus, the diastance from the top and bottom, between port and wall is shorter than that in the middle.

Again, based on what I read, one should shoot for a distance from the end of the port to the rear wall, that equal or greater than the width of that port.

So my question is, and my reason behind it, is, how close would you dare, cheat, this measurement? To where the tops and bottom of the port is somewhat closer than the measuremen I had described...obviously touching is not a good scenario, but I am curious if anyone has looked into a similar situation.

My reason, if I were to move the port closer, cheat it a bit, I could potentially tune a bit lower.

Did not have the xcons in there long enough to play with very many variations....

The 30hz. Port did come closer to the rear wall.

Unfortunately I have nothing to compare what, if any, effect that had on its performance.

Part of the issue is the actual port length extends beyond the physical port length.

Look up port end correction and it will make more sense and explain it a lot better than I can.

Sort of the chain link scenario, weakest link will break in the chain. If the input volume of the port constricts the air then the area of the port becomes uselessly oversized.

It's my understanding that in fluid dynamics, round pipes are typically 45% more efficient than square...

Most of the port velocity things I've read are based around home audio design. It seems like you need a slightly higher port velocity in vehicles or maybe it's just a trend. When I went from the 12.5" port to the 11.375" port a few things changed. One obviously was box internal volume and tuning.. I went from a 38hz tune to a 33hz tune. I think I need more power to properly judge this smaller port, but I'm quite happy with it. Port velocity on paper is higher, but I haven't really noticed a difference. Box went from 9.5 cubes to 10cubes. It's slightly higher now since I inverted the subs. Guess I'm just rambling on....

Good points fellars..

I am glad I asked, gives me some direction!

Fyi,

4 15" zcons coming soon!

It's my understanding that in fluid dynamics, round pipes are typically 45% more efficient than square...

Most of the port velocity things I've read are based around home audio design. It seems like you need a slightly higher port velocity in vehicles or maybe it's just a trend. When I went from the 12.5" port to the 11.375" port a few things changed. One obviously was box internal volume and tuning.. I went from a 38hz tune to a 33hz tune. I think I need more power to properly judge this smaller port, but I'm quite happy with it. Port velocity on paper is higher, but I haven't really noticed a difference. Box went from 9.5 cubes to 10cubes. It's slightly higher now since I inverted the subs. Guess I'm just rambling on....

Any audible differences you noticed were from the change in tuning and volume, not port area / port speed.

It's my understanding that in fluid dynamics, round pipes are typically 45% more efficient than square...

Most of the port velocity things I've read are based around home audio design. It seems like you need a slightly higher port velocity in vehicles or maybe it's just a trend. When I went from the 12.5" port to the 11.375" port a few things changed. One obviously was box internal volume and tuning.. I went from a 38hz tune to a 33hz tune. I think I need more power to properly judge this smaller port, but I'm quite happy with it. Port velocity on paper is higher, but I haven't really noticed a difference. Box went from 9.5 cubes to 10cubes. It's slightly higher now since I inverted the subs. Guess I'm just rambling on....

no, not 45% lol

And you need lower port velocities in a quiter environment

It's my understanding that in fluid dynamics, round pipes are typically 45% more efficient than square...

Most of the port velocity things I've read are based around home audio design. It seems like you need a slightly higher port velocity in vehicles or maybe it's just a trend. When I went from the 12.5" port to the 11.375" port a few things changed. One obviously was box internal volume and tuning.. I went from a 38hz tune to a 33hz tune. I think I need more power to properly judge this smaller port, but I'm quite happy with it. Port velocity on paper is higher, but I haven't really noticed a difference. Box went from 9.5 cubes to 10cubes. It's slightly higher now since I inverted the subs. Guess I'm just rambling on....

no, not 45% lol

And you need lower port velocities in a quiter environment

that makes sense.