Brandon I thought you might like this "vent" portion of the video:
1st part is a normal vent with typical phase shift higher in freq., but the newer triangle shape shown about 45 seconds later definitely shows improvement.
Looking at the inside of it though it appears there is more going on than the shape itself - with something that looks like resistive-flow damping.
1st part is a normal vent with typical phase shift higher in freq., but the newer triangle shape shown about 45 seconds later definitely shows improvement.
Looking at the inside of it though it appears there is more going on than the shape itself - with something that looks like resistive-flow damping.
Probably modeling in Comsol with their acoustics module.
Many have tried different shapes for bass-reflex venting, but getting that much of a specific result seems modeled to me. (..you never know though, it could have been a lot of trial and error selective evolution.)
NEXO also has a "squeezed" vent design to attempt to achieve more of a laminar flow for their sub.s. This looks a lot more similar (with other designs) to me their MF triangular vent (with presumably some sort of resistive flow).
https://www.nexo-sa.com/systems/stm/technology/
I guess there is no reason not to Comsol in year two thousand, age of computing and emerging AI. Lets see when these tools become cheap and (relatively easy), available for DIY community 
Then we need to be able to manufacture the big and complex shapes.. perhaps industry stays always a bit ahead.
Then we need to be able to manufacture the big and complex shapes.. perhaps industry stays always a bit ahead.I guess there is no reason not to Comsol in year two thousand, age of computing and emerging AI. Lets see when these tools become cheap and (relatively easy), available for DIY community
As I have mentioned before, they have been freely available in research software form rather than expensive commercial software form since well before the web started. It is strange how few speaker DIY folk have used such software over the decades given how learning to do something cheaply to reproduce what commercial companies do at significant expense tends to be part of most DIY hobbies.
The research software available has changed over the decades and depends on the area. Now and again I will go looking for software I used in the 80s or 90s only to find it has vanished or become commercial. There are hundreds of FE packages with perhaps 3 or 4 useful ones like elmer, code_aster, calculix, ten or so acoustics package like acousto, bem++, tens of CFD packages like openfoam, su2, hundreds of display packages like visit, paraview, hundreds of grid generators like gmsh, tens of preprocessors like salome, elmer, hundreds of CAD packages like salome, freecad, etc... There is vast amounts of software although only a modest proportion is useful for practical engineering in the sense of requiring a reasonable amount of time and effort to get repeatable reliable simulations. It requires a degree of both computer software literacy and mathematical modelling literacy to use which the majority of speaker DIY folk likely don't possess but some will.
Perhaps what you are seeing is that the DIY folks are focusing their attention on areas which have a significant impact on loudspeaker system performance. Learning to use ARTA or REW to make good measurements, learning to use VituixCad, learning to use ATH4... These are skills that really make a difference.
Cabinet signature is a secondary effect at best. The difference between an average cabinet and a low-signature cabinet becomes meaningful only if the speaker designer has done everything else right.
j.
No question that good software like VituixCAD and REW is where speaker DIY starts but when a desire to increase the quality of a design grows it becomes necessary to use tools that can address the details. It is no different in industry where the high tech end invests substantial resources in refining the details whereas the low tech end a lot less. The absence of adopting appropriate tools to take that next step among the keener DIYers seems odd to me but then I am an engineer that has been familiar with such tools all my working life.
Although it seems to have an odd way of going about things, ATH4 is giving DIYers the opportunity to look at the 3D acoustic details of a loudspeaker design. Not sure how widely it is being used for this purpose but it has started. BEM isn't that appropriate for room acoustics so there is still another step to take with acoustic software to address what we would really like to know in terms of loudspeaker acoustics. Details about structural vibration and more general fluid mechanics of loudspeakers has yet to be adopted.
Indeed it is a detail but how enjoyable is a hobby where the basics are OK and the details aren't? Perhaps not knowing the details are wonky can help particularly if you can find articles stating that, for example, bracing the hell out of everything is what you need to do? Unlike the drivers and other components that are bought complete, the cabinet design is usually wholly owned by the DIYer and likely to be one of the aspects they derive most pride and satisfaction from getting right.
In about a month or so I hope to put up something on the engineering of a woofer cabinet. Not a full project and only covering a few aspects but assessing things in a quantitative manner like engineers in industry (e.g. the recent KEF white papers but without the marketing slant and with more details included). Will leave plenty of things open. It won't be everyone's cup of tea but if there is sufficient interest in the approach I will add to it and perhaps it can grow. It will be out in the open on github and so collaboration would be straightforward should others have an interest in the medium term.
If you look at how complex it is to design a decent sounding BR enclosure and how important the port geometry, size, placement, etc is, there is little reason to shy away from a horn loaded LF system (aside from physical size limitations). The main reason I have stayed away from ported designs is the distinct sound signature they typically have, which not only affects SQ but also makes ir harder to integrate with other drivers due to phase anomalies. The port resonance itself can be bad enough and most cylindrical ports have severe resonances which are hard to tame after the speakee is designed and built. This is one reason why I like sealed enclosures. I've also had more luck building successful horn loaded designs than ported.
The stiffening and dampening strategy needed to build a decent sounding ported box that allows for a high LF HP frequency involves alot of engineering and planning. The stiffening usually gets in the way of aerodynamics. Unless you have extensive experience building ported boxes that employ wide band drivers, its better to stick with sealed enclosures. Its relatively easy to build something that makes a ton of low frequency noise, but building a low distortion, high output large ported sub that can be crossed well into the 3 digit frequencies isn't easy. Ive been to many concert venues and 9 times out of 10 I'm disappointed in the low end intelligibility. As a bassist thats very depressing. Thats probably more a product of the sound engineer than it is the equipment, but still very disappointing considering the price of admission nowadays.
The stiffening and dampening strategy needed to build a decent sounding ported box that allows for a high LF HP frequency involves alot of engineering and planning. The stiffening usually gets in the way of aerodynamics. Unless you have extensive experience building ported boxes that employ wide band drivers, its better to stick with sealed enclosures. Its relatively easy to build something that makes a ton of low frequency noise, but building a low distortion, high output large ported sub that can be crossed well into the 3 digit frequencies isn't easy. Ive been to many concert venues and 9 times out of 10 I'm disappointed in the low end intelligibility. As a bassist thats very depressing. Thats probably more a product of the sound engineer than it is the equipment, but still very disappointing considering the price of admission nowadays.
I just went to a Bonnie Raitt concert where the sound was excellent except for the bass. It was muddy, indistinct and boomy. A couple of years ago I went to the same outdoor venue to see Peter Frampton on his farewell tour. And the bass was excellent. Same PA system as far as I could tell. Yes, I blame the sound engineer (although calling him/her an engineer is far too gracious in my book).
What a brilliant video.
Devin Sheets from Alpha Sound is just so good at explaining and showing some rather complex subjects.
I learned something
And also showing how to easily and very fast, measuring the effects of the vent etc.
Brilliant. High 5 from me