Originally Posted by MeltManBob
IBasically as you were saying about flaring too fast, there is probably an optimal taper and it probably changes based on how it is being controlled.
Yeah maybe but like I said I'm not a physicist or fluid dynamics professor. I really can't help you with this barrage of questions about port shape other than to say just don't flare out too fast.
This is Danley's only ported box. Danley is a legend in loudspeaker design and this is the only ported box that he's ever sold as far as I know. The port is extremely simple, the entire port is a flare, it starts out big at one end, tapers to a narrow point in the middle and then flares back out to a large opening at the other end. You really don't need to get more complicated than this wrt shape. As long as velocity remains in check the port can be pretty simple.
I can help you with Hornresp and other simulators, I can't help with the extremely complex port shape ideas you have.
What I can tell you is that port shape isn't incredibly important as long as the aspect ratio isn't exceedingly high. Ports operate in a frequency region where are hearing is quite insensitive and really all they do is act as a duct/waveguide to allow air to flow through. If the Reynolds number isn't incredibly high the air is going to find it's way through just fine.
flares have to be approximated which ends up with a different contour profile because HR functionally describes uniformity in 3D space like an instrument horn.
Not sure what you mean here - you can tell Hornresp to specify a flare with a PAR expansion, then you can build that and it's exactly the same as what you simulated, not an approximation. When I was talking about approximations I was talking about making a byp/ex flare out of multiple PAR segments. There's no rule saying that a port flare has to be exponential, hyperbolic/exponential, conical, or any other defined expansion. Just look at the Danley box picture I just showed, it's just a flare make of two PAR segments.
What I took away from flare it is that the whole 10m/s or even 17m/s is just a rule of thumb not really based on anything related to ports specifically.
Incorrect. EVERYTHING in Flare It is based on empirical testing. Read around the site, they explain everything, how they came up with these numbers, what the numbers mean.
I'll have a look at that paper but my patience for reading thesis papers for relatively short answers is not very good!
And this strikes right to the heart of the matter, I think this is the problem. I've spent 10 years reading and researching hundreds of papers like this one. I can understand you want to fast track this but if you don't want to read the papers that are written by experts detailing their research and empirical testing you are going to come up with a lot of false conclusions. You NEED to read the resources if you want to understand how this stuff works. Does it really matter if there's a "perfect" flare shape if the simplest flare you can imagine (the picture above) works just fine?
Something I feel this will actually be useful for is the mains and controlling dispersion and comb filtering? I think that's the one where 2 drivers interfere as opposed to lobbing.
You will have issues with dispersion, lobing and comb filtering with a 2 way speaker if if it doesn't have a port. When you have two sound sources separated by a distance playing the same frequencies you will have interference at some frequencies based on offset distance, size of radiating area, wave lengths and mic (listener) location. Putting the tweeter (and maybe the mid) in a waveguide) can help with dispersion, keeping the drivers as close as possible (coaxial being as close as you can get) will help with lobing and comb filtering. There's not much you can do with a port shape to help with any of these phenomenon.
I look forward to going over the designs.
Yeah, maybe later tonight.
In your experience what are your thoughts on room gain wrt specific frequencies generally gaining, decreasing and staying flat? I read about what those people tested in their set up and I know the room is the factor with the shape and size being the largest contributors. I'm just asking if you have concluded that there are generally certain expected responses within a realistic spectrum of room shapes and sizes that the average person might find themselves occupying for audio/HT.
Every room is different, even rooms with the same dimensions can act significantly different based on what's in the room, how airtight the room is, what the room construction consists of, etc.
In general, the max room gain you can get is 12 db/oct gain as frequency decreases starting usually at a frequency somewhere around 30 hz (depending on room dimensions).
Even better is there a program that can simply consider room gain from a basic rectangular/square cube?
Yes, I already told you that Bagby's Diffraction and Boundary simulator will do exactly that. It's an excel spreadsheet that's super simple to use.
I don't mean to offend, but at this point I'm repeating myself an awful lot on some of these subjects, I wonder if maybe you should take a break, reread the entire thread, try to absorb it a bit better, catch up on the resources I've linked to (I know you don't want to read it all but I'm not going to talk about fluid dynamics if you can't be bothered to even read the port paper) and come back at this with a fresh perspective.
Based on that article and reading it a couple of time elsewhere about the flat 12hz response is why I tried to model the ported boxes to have their lower peak centered on 12. Again, I don't want to design for MY room but if there are pretty standard 'issues' then I would consider designing to them if the opportunity is presented like having that lower peak at least I know where best to put that.
In the article he's describing an anomaly at 12 hz in THAT SPECIFIC ROOM. It could be caused by the sub location, the room dimensions, the room construction or any number of other things. Basing your design decisions on someone else's specific room anomaly when it's not even clear why there's a problem would be very foolish.
I really don't mean to be harsh but you clearly are not absorbing everything that I've been saying. And you even admit that you are not too interested in reading the links. This is going to be an issue. You seem to be ignoring some of the basics and on the other hand getting into extremely complex areas at the same time. You can explain this as your specific way of learning if you like but you NEED to get a handle on the basics before you can move on to extremely complex issues like fluid dynamics. This is going to require a lot of reading and research whether you like it or not.