My Findings...

[oldsoundguy]

That's the part that confuses me. Does more air flow increase bass sound in an enclosure? I am not sure if it has anything to do with it at all. Tuned in for sure though.

[bbeljefe]

That's the part that confuses me. Does more air flow increase bass sound in an enclosure? I am not sure if it has anything to do with it at all. Tuned in for sure though.

That's the goal of this discussion... to find out if perfect air flow would actually help or harm sound pressure. Or at least, that's my goal, lol.

In simple terms, the more air a sub moves the more sound pressure it creates. But when you're using both the front and the back of the driver's piston, there are considerations to be made for the phase of the back wave. If the back wave is 180° out of phase with the front wave, then cancellation occurs but if it's only slightly out of phase sound pressure increases.

I've been thinking about this whole issue and it seems to me that ¼ wave theory could shed some light on the matter. I know there are a lot of people who go to enormous pains to make perfectly rounded corners in transmission lines but I don't know of any studies where those boxes were tested against an identical box with only 45° wave guides and/or no wave guides at all. That would be interesting and very informative.

Also, I think transmission lines would be ideal for testing air flow differences because there is a minimum amount of internal pressure in the cabinet relative to a conventional vented box.

[TeamHT]

1/4 wave. Exactly what I'm rereading up on to form an educated hypothesis, lol

[oldsoundguy]

It would be interesting to see results.

[Krakin]

This relates very closely to the book I have started reading, The Sensations of a Tone as a Physiological Basis for the Theory pf Music, by Hermann Ludwig F. von Helmholtz.

The Helmholtz resonator has applications in combustion engines, subwoofers, acoustics, intake systems, and much other things.

http://en.wikipedia.org/wiki/Helmholtz_resonance

You can read the book, or download it, from here for free

http://books.google.com/books?id=Xy4DAAAAQAAJ&printsec=frontcover&dq=on+the+sensations+of+a+tone+as+a+physiological&hl=en&sa=X&ei=PEPtUryUNMbmyQGnrYGICA&ved=0CCkQ6AEwAA#v=onepage&q=on%20the%20sensations%20of%20a%20tone%20as%20a%20physiological&f=false

[bbeljefe]

1/4 wave. Exactly what I'm rereading up on to form an educated hypothesis, lol

Agreed. I need to do some reading myself.

[ParDeus]

The easy route would be to model it in CFD, but that only is a model to tell us what a certain design should do physically more than acoustically.

I can build a t-line and put pitot tubes in certain areas to measure localized pressures and velocities. I also have a minimally invasive air flow meter that can measure total energy output as a function of either rpm or oscillation. A swirl/tumble meter can also be used to measure what any upsteam changes have on flow linearity at the terminus of the port. And of course a term lab at the port.

Then the challenge becomes graphing all this data to be able to draw conclusions on how any changes affect total output.

And of course all this will have to be done a-b-a. I will start with flow visualization to decide where to put the pitot tubes.

Any input on designing the enclosure and what driver to use? Or should I just do the standard 1/4 wave of the drivers Fs with port area equaling pis5on area?

[CleanSierra]

I like threads like this, I'm watching.

[Smoove]

Damn, time to tear my box apart and start over

[Jessica]

Would a port with no pressure zones, I mean, none that are substantially higher/lower than other places in the port be best?

I say this because the port has to kind of work like a pump. Air flows both ways at a fairly high rate. Think about the air speed and volume of air and how the sub has to force that air to come to a dead stop and change direction over and over 20 to 80 times a second.

If you had a dead zone of low pressure in your port or a very high pressure zone because of whatever reason. Say a 90 or 45 or whatever. I could see how that would kill output or cause other issues.