My Findings...

[ParDeus]

WARNING: The following post contains actual scientific test results. No anecdotes allowed.

So first a little background. I'm employed as a professional fuck-off. I race for a living, and design/develop and build racing engines. What does this have to do with subwoofers/enclosures?

Airflow. I'm an airflow guru. I've been porting cylinder heads for years. You learn that air does NOT act as you would intuitively think it would.

For the last few months, I have been applying my knowledge and testing procedures from cylinder head airflow to subwoofer enclosures.

I will share some findings, but please understand that I can't share everything I've found, all at once. There is some findings that need to be further tested.

1. 45's in boxes.

Seems pretty straightforward, right? WRONG. I know that air never likes to turn more than +/- 14deg in any direction.

So I made a port with 1 90deg turn. I used a flow bench capable of pulling 60" of vacuum, but pulled 28" WC for all testing.

I tested ports with the same CSA (cross-sectional area), 4 in total on the first round of testing. The numbers were recorded.

I then put 45's in the port, both inside and outside corner, while keeping the CSA the same throughout the port.

Well, on average, ports with 45's flowed, on average, 14% WORSE than ports with 90deg corners. And yes, all variables were held constant.

I then used a pitot tube to do a velocity profile. The flow was it's fastest just after the first 45, which indicates choking and turbulence near the boundary layer. These findings were confirmed by doing a smoke trace as well as a wet flow analysis.

So, in this rudimentary test, it appears 45's to be a hindrance rather than helpful.

Yed, I did test an idea that improved flow significantly over both 90 and 45s. That will be my next post, as it is 4am and time for coffee and a pastry.

I have conducted many other tests, and I will post them in the following days as I find the time. Also, please forgive me if I don't share everything in public, as I feel I've learned some groundbreaking things.

Btw, I am not a box designer. I pay other for that. People who are smart enough not to say "oh yeah, dd's love big ports, brah"

For people who would like other tests performed or would like to speak in private, you can pm me and I will give you my cell number.

More in a bit...

[Triticum Agricolam]

I'm curious to see your other results. Thanks for what you have posted so far!

[Karkov]

Thanks for the tests but I'm curious as to why some big companies have not done these already, why do we see so many 45's in boxes?

Also, I'm wondering how your tests work, does it send air flow at a constant state? With a sub enclosure the amount of air is ever changing, does that play a role?

Ambient temp, humidity, and the like, are all irrelevant considering people use sub enclosures all over the world so I'm assuming results are some what *cookie cutter*

[n8ball2013]

why do we see so many 45s in the boxes same reason we still see people using garbage amps. People are stupid and the internet has its rages. Ive been saying this for years.

[Skullz]

I like where people make tests like these from different backgrounds applying their knowledge for others to see and compare in this hobby.

Fluid dynamics is an awesome field of study and applies to so many things in life we take granted of that were are completely unaware of.

[Fuzz]

Is air flow the same as the sound waves that produce the movement of air? In a ported enclosure, the air has only one way in/out. So the air that is sucked in is then sent out of the same portal. That is not truely air flow but wave action. In other words, air does not perputually enter or exit the chamber. The air is only moving the distance of the excursion. The air you feel at the port exit is generated via sound waves. It is not really moving outward as it seems.

Not to argue, but is it the same as air flow?

[ParDeus]

Air flow is a comprehensive term.

Designing an intake manifold/induction system for a race car is pretty damn close. You have your compression and rarefaction waves. In racing we design the system to utilize mainly the 3rd or 4th harmonic. It is partly based on sound waves, and while that might be an oversimplification, the two are intertwined.

In racing, you can have your induction length tuned to a certain resonance, however that is more often then not a guarantee that you will achieve it. You have to study how the pressures at each end, the shapes, localized velocities etc. effect the wave.

Same as a driver on one end of a tuned port.

Think on this...

Every time air converges or diverges, is sheared, turned, and goes through velocity changes, there is a LOCALIZED wave generated. That localized wave has an impact on the overall wave tuning. Then you must look at interactions of how one wave cycle and it's intricacies effect the next wave cycle, while taking into account the conditions outside the waveguide/port.

So you can have an enclosure with a port tuned to 33hz, but that doesn't mean it is a "clean" or efficient transfer of energy.

And btw, an aeroport is NOT nearly as efficient as anyone thinks, far from it.

[ParDeus]

Conservation of energy is what I'm getting at. I've yet to see and #'s for ports with a given cross sectional area.

Some might say I'm taking all this a little too far. Well, that's my nature, and while I believe the results are worthwhile, I've not promised such.

I have built pro-stock engines that are 500ci, naturally aspirated, and make nearly 1460hp. That's OVER 125% volumteric efficiency, thanks to wave tuning.

Fun fact- A pro stock engine developes the highest bmep (brake mean effective pressure) of any naturally aspirated engine on Earth, including F1. That's just a shitty ol' American V8 for ya!

[TeamHT]

I hate that people keep talking about the airflow in an enclosure, more specifically through corners. If it was going in a single direction the subjective term air flow could be used, but that's not the case at all. Air is going back and forth continually at high rates. 45s might help...if instead of subwoofers in the cutouts they were fans.

[n8ball2013]

im waiting for some retard to come in and talk about how he 45d every corner in his box and how awesome it is. That way I can laugh at him.