ParDeus Posted February 1, 2014 Author Report Share Posted February 1, 2014 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. Exactly. My thought is to maintain a dynamic equilibrium WRT pressures. I assume that would be beneficial, but I don't know for sure. Link to comment Share on other sites More sharing options...
Jessica Posted February 1, 2014 Report Share Posted February 1, 2014 Well. I'm going to sit back and watch this thread. Maybe I will learn something. Rest in peace, walled 87 accord build log 03' Corolla build with AA Mayhem inside. My super random youtube channel and terrible camera work. Wiring comparison by CaptainzPlanetz Wire and fuse guide by Guest SyKo13 Link to comment Share on other sites More sharing options...
bkolfo4 Posted February 1, 2014 Report Share Posted February 1, 2014 I think it would depend on more than just "with or without 45's". A port is not just constant airflow, and more airflow does not necessarily mean louder every time. I gained almost a 1/2 dB by just adding one 45 in the back corner of my port, but the port did not actually have a port wall along the back of the box. It ended 9" from the back wall, and the port was 9" wide. And that was the ONLY change I made to gain that 1/2 dB. Current system: 1997 Blazer - (4) Customer Fi NEO subs with (8) American Bass Elite 2800.1s Previous systems: 2000 Suburban - (4) BTL 15's and (4) IA 40.1's = 157.7 dB at 37 Hz. 1992 Astro Van - (6) BTL 15's and (6) IA 40.1's = 159.7 dB at 43 Hz. Link to comment Share on other sites More sharing options...
bbeljefe Posted February 2, 2014 Report Share Posted February 2, 2014 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? I don't think tuning makes a lot of difference but obviously, all tests should be done with the same driver & the same tuning. As for line area, I've had luck with reducing it 8-10% below Sd but like tuning, I don't know that it matter so long as there's a control. Facebook: facebook.com/audioanarchyllc Instagram: audioanarchyllc Youtube: youtube.com/bbeljefe Link to comment Share on other sites More sharing options...
Krakin Posted February 2, 2014 Report Share Posted February 2, 2014 I haven't gone through the paper on AES yet, but there was a work done on the flaring and maximizing the performance from ports that suggests that you should make the flare radius of the port equal to the length of the port. Like this, "The ideal port shapes for high-velocity inlet and exit air streams are different, and the best solution is one that balances both." It would be cool to see something like this done, if you are interested in it. The article: http://www.aes.org/e-lib/browse.cfm?elib=11094 Krakin's Home Dipole Project http://www.stevemeadedesigns.com/board/topic/186153-krakins-dipole-project-new-reciever-in-rockford-science/#entry2772370 Krakin, are you some sort of mad scientist? I would have replied earlier, but I was measuring the output of my amp with a yardstick . . . What you hear is not the air pressure variation in itself but what has drawn your attention in the two streams of superimposed air pressure variations at your eardrums An acoustic event has dimensions of Time, Tone, Loudness and Space Everyone learns to render the 3-dimensional localization of sound based on the individual shape of their ears, thus no formula can achieve a definite effect for every listener. Link to comment Share on other sites More sharing options...
ParDeus Posted February 2, 2014 Author Report Share Posted February 2, 2014 THAT is an efficient shape, matter of fact it is hard to get much more efficient. That is exactly what I've been mulling over, but I didn't know how it would act acoustically. The only thing that can be improved there is boundry layer adhesion, and that is relatively simple. And it does increase efficiency. Anybody play golf? (hint hint) Link to comment Share on other sites More sharing options...
subsonicluv Posted February 2, 2014 Report Share Posted February 2, 2014 THAT is an efficient shape, matter of fact it is hard to get much more efficient. That is exactly what I've been mulling over, but I didn't know how it would act acoustically. The only thing that can be improved there is boundry layer adhesion, and that is relatively simple. And it does increase efficiency. Anybody play golf? (hint hint) I'm going to guess you're talking about the divots on the golf ball that increase the areodynamics of the ball. I want to say Polk audio experimented with this on the ports of some of their HT towers. edit: I meant dimples, not divots. And Precision Port makes flares with these dimples. 04 Blazer Xtreme HU: Kenwood KDC-MP235 Front Stage: Lanzar MX6C Components Rear Stage: Lanzar MX693 6X9's Sub Stage: (2) Obsidian 18 D2 V2 Mids / Highs Amp: Boston Acoustics GTA 704 Sub Amp: Boston Acoustics GTA 1000m Optima Yellow Top (up front) Singer 275A Alternator Future Plans: One More GTA 1000m (maybe) More batteries More runs of 1/0 Pioneer DEH-X7500S (on order) Link to comment Share on other sites More sharing options...
Jay L. Posted February 2, 2014 Report Share Posted February 2, 2014 http://www.google.com/url?q=http://www.stevemorrisengines.com/steve-morris-engines-store/pro-volutes-1.html&sa=U&ei=2q_tUrb1KcG9rgHehYGgDw&ved=0CBIQFjAB&sig2=_d7ypc0PUQ4itlCn9Tj7vQ&usg=AFQjCNGU-pA9eECgWKA54b32wIJb7Xd4Bw Link to comment Share on other sites More sharing options...
Jay L. Posted February 2, 2014 Report Share Posted February 2, 2014 Kind of the same but different Link to comment Share on other sites More sharing options...
Neckbeard Posted February 2, 2014 Report Share Posted February 2, 2014 You could have stumbled across something significant here haha Build log, Super slow!!: http://www.stevemeadedesigns.com/board/topic/168096-slow-neckbeards-1970-opel-gt/ Link to comment Share on other sites More sharing options...
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