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post #151 of 230 Old 09-12-2017, 10:56 PM
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Originally Posted by MeltManBob View Post
Just went through the room gain link, looking through the TL word doc, realized I've looked through this several times but haven't read it word for word. Anyway I'll skim through it a bit now that I have more context, it's been a couple months since I last looked at it. Anything besides driver placement and it's effect I should look for in particular?
In the main body of the article it shows how size and shape of the tl are related. This is important and it relates to all things, not just tl. Ports, horns, etc, these relationships apply to size and shape. And you should read all the attachments, there's only 4 of them and they are all mostly pictures that show what happens when you do certain things like change driver t/s, add stuffing, etc.

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It's funny you gave the example about wiring a panel cause I had written something along those lines ...
I got you. I'm just saying that if I asked you to tell me everything there is to know about electrical panels in one forum post it would be hard, you would have to start with the basics since I'm not an electrician and build your way up to all the types of panels, what they do best, and how more than one panel can be a good choice for a specific goal set. It's just easier to answer one very specific question at a time.

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Anyway so far I have modeled a sealed, ported, ABC, ...
Now that I know what you've been doing it helps to know how to answer your questions, thanks.

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You keep saying I don't have a solid grasp of ported and sealed, why is that?
Have you fully figured out flares yet? Have you tried mltl (long ported)? Have you applied the appropriate high pass filters on your designs? (The high pass filter will have massive effects on frequency response, velocity, group delay and everything else, if you haven't applied the required filters you don't really know how the design will act in real life.) Have you done a bunch of different tunings, tried trading box size for port length, stuff like that?

[quote[I still feel like I'm hopping on one foot with this metric stuff and all the extra clicks it takes to view different things then compare.[/quote]

There's not much you can do about that unless you want to switch to a different simulator or learn metric. Just so you know, TL.app will operate in full imperial mode if you like, but it doesn't have any "compare" feature at all. All simulators have different strengths and weaknesses. Unfortunately for you, WinISD is the only simulator I know of that will allow you to compare 10+ things all at once. I've never needed any more than Hornresp offers (with the addition of saving a few screenshots and pasting them in MS Paint).

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I already have half a dozen instances running and I'm about to double that; this capture one graph thing such a handicap. All I can derive is a direction in 1 variable while having to mentally track previous results to see patterns and consider multiple variables. Just like in math; 2 points will only ever get you a line, 3 points a quadratic function, 4 points etc. but hardly anything in this is linearly related.
If you make small quick changes in the wizard you can look at a whole continuum of designs in just a few seconds. I love the way Hornresp allows you to make such quick changes and view the results in real time. It would appear that either your learning style is not appropriate for the way Hornresp does things or that using WinISD first was a significant handicap since you have come to rely on how that program operates.

I can tell you that it gets a lot easier with practice. For example you can give me any driver t/s you like and request a design using any box type you want (other than bandpass) with a specific net volume and tuning and I'll have a design for you in 10 minutes or less. That includes the time it takes to input the t/s and everything. And if you give me a couple extra minutes I can compile images, host the images and post them. This is why I say you learn more by doing.

Take it easy, take a break. This is only your second day and you are doing extraordinarily well. Don't try to push it too fast. You'll get severely overloaded and frustrated.

Just keep asking specific questions. If you have a design and you don't know where to go with it post a screenshot and ask for advice.
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post #152 of 230 Old 09-12-2017, 11:00 PM - Thread Starter
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Here's one for you, I have 2 instances both with the same values and the schematic looks the same but I can't get them to change to the appropriate design type so they graph differently. One says horn and the other says path at the top on the power graph. I've gone into the driver config menu in tools and selected Nd for both hitting ok but no change. Is it possible to change design types without changing records?
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post #153 of 230 Old 09-12-2017, 11:01 PM - Thread Starter
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Nevermind, I had one stuck on horn for the velocity. Makes sense now, especially why I couldn't get that response graph to look right for the life of me.
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post #154 of 230 Old 09-12-2017, 11:02 PM
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Just remembered, that 'crazy' home theater speaker design I posted one picture of that had a curved horn above a box, that horn was modeled off of the tables in that TL doc. I thought it weird to be tapering from like 8" to 1". If I'm understanding it correctly not that I read much but just looked at the diagram and tables, having the open end taper to be smaller than the driver end (closed end) makes it so you can get a lower tuning frequency with less length. I read it to be that you find the frequency tune you want and whatever length you pick from that column you go to the ratio for that row and that's what you use. Ex: 40hz tune at 60" requires the closed end to be 5 times the area of the open end (the .2 SL/SO row).
I've already talked about a great deal of this. Yes, the taper allows a much shorter length AND much less volume for a given tuning. It's the closest tl type to a ported box, similar size, similar behavior. You just have to sim it and make sure the open end terminus velocity is acceptable.

And you don't need to use the chart, as I already mentioned there's a spreadsheet available for download on the same site that will automate the chart for you - you just have to fill in a few input boxes and it will spit out the tl design for you.

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I didn't take it any further than that because I know TL are not that simple and also building an actual tapered, curved, circular horn is going to require so build skills and probably a little modification to the calculations since it's not a uniform taper.
TLs are that simple if you know what you are doing, but yeah, the picture you drew would require some fancy woodworking. And unfortunately you've drawn it as end loaded (what you call inline), you could get a lot better frequency response by using an offset driver position (Od). Although if you stuff it full of dense stuffing the resonances won't matter much because it will behave mostly like a somewhat large sealed box, if that's what you want.
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post #155 of 230 Old 09-12-2017, 11:04 PM
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Here's one for you, I have 2 instances both with the same values and the schematic looks the same but I can't get them to change to the appropriate design type so they graph differently. One says horn and the other says path at the top on the power graph. I've gone into the driver config menu in tools and selected Nd for both hitting ok but no change. Is it possible to change design types without changing records?
I have no idea what you are talking about but if you double click the red Nd label (and keep double clicking it) you can go through the entire roster of available options. There are a few.
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post #156 of 230 Old 09-12-2017, 11:10 PM - Thread Starter
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Honestly the desire for that TL is being rather unique compared to a sealed or ported box. I could make it sealed but I'd like to do something more complicated if the output makes it justified. I'm not sure if I'll go that route for the mains though unless I figure a way to move the screen out of the way. Only way I can think of at the moment is to put it on something like a garage door track. Having it just swing up to the ceiling means I have to keep the first 6' or so clear on the walls or else I have to make the screen more narrow which I don't want to do. It's down to around 135" and I was originally aiming for about 145-150".

For now the subs. Since I know what kind of build envelope and power I'm working with it's just a matter of deciding on using the infinities or buying something like the SI18's and what box design is going to give me the response I want.
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post #157 of 230 Old 09-12-2017, 11:17 PM - Thread Starter
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Generally speaking on a ported box when I switch from the horn output to combined and it asks for distance between the driver and port, is that negligible? I'm noticing about a .01db difference but I'm not sure how consistent that is.
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post #158 of 230 Old 09-12-2017, 11:46 PM
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Generally speaking on a ported box when I switch from the horn output to combined and it asks for distance between the driver and port, is that negligible? I'm noticing about a .01db difference but I'm not sure how consistent that is.
This isn't something you want a general answer for. When you have two sound sources playing the same frequency at two different locations they will interfere with each other. There will be constructive and deconstructive interference. The worst possible thing you can do is make a long tl with the driver on one end and the port on the other end. If you were to take something like that outside and lay it on the ground and walk around it measuring the frequency response you would get a different frequency response at every step you take. It's a disaster.

The triangulated locations of the driver, port and mic (listener) determine what the situation will be. Normally it's good to get the driver and port on the same plane, the same distance from the listener. Play around with a long enclosure and use the combined output tool to set different triangulated offsets and see what kind of horror show frequency responses you can come up with.

In a small(ish) room a lot of this is evened out since everything is bouncing around everywhere but in general terms it's best to keep the driver and port the same distance from the listener and if there's more than one listening spot the only way to do that is to put the driver and the port as close as possible as on the same face of the enclosure.
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post #159 of 230 Old 09-12-2017, 11:50 PM - Thread Starter
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Makes sense, I wasn't using a huge offset, something like 10-20cm. Is the program assuming the listening position is axially inline with the driver or is it assuming the LP is midway between the driver and port/horn output?
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post #160 of 230 Old 09-13-2017, 12:01 AM
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The program assumes that if the distance difference is 0, the port and driver are the same distance from the listener. This can occur if both the driver and the port are on the same box face and vertically aligned OR if the box is oriented sideways and the driver and port are on opposite sides of the box but still the same distance from the listener. The combined output tool has had significant changes recently and I haven't used it since so it's best to check the instructions.

For more info on this phenomenon you can look up lobing and comb filtering. This is the reason that in 2 way speakers the woofer and tweeter are as close as physically possible. Through the crossover region the drivers are playing the same frequencies, obviously from two different locations. If the two sound sources are less than 1/4 wave apart then they will sum and act as one. If they are further than 1/4 wavelength apart they will cause all kinds of interference. This will be incredibly important when you get into mains design. You don't want lobing (or at least as little as possible and you want to point the lobes where they cause least damage). If you downloaded PCD already you can grab a sample .frd and load it into the program, You can use the same .frd for both the woofer and the tweeter, it doesn't matter, this is just for research. Set your driver offset distances (relative to mic or listener) and rotate around the axis and see what happens to the frequency response. It will be a roller coaster as you move around at frequencies that are smaller than 1/4 wavelength of the driver to driver distance.

Anyway, I'm out for tonight. Have fun.
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post #161 of 230 Old 09-13-2017, 02:57 AM - Thread Starter
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Yea I'm somewhat familiar with lobing and comb filtering from looking into those fancy line driver arrays that are supposed to have good off axis response.

Edit - the rest of this is pretty much a tangent and starts to go off the deep end but w/e I'll post it anyway even though I had to re-read it a couple times to follow myself after I wrote it...

Regarding flared ports should I be double checking the end of the flared port against flare it? So far what I've noticed is that the flare length doesn't really matter so it seems best to get as much length from the 'narrow' portion and then just flare the last say 5-10cm. I'm sure it's usually pointless because the flare is probably large enough that the limit is the self imposed 10m/s but for arguments sake lets say the end of the flare was 50mm diameter which is where flare it says 10m/s will cause core problems. I'm guessing there is no practical situation where you could ever run into this problem but I haven't sat down to really think of every possibility.

The other part of this is it looks like in flare it the chuffing is based on the radius which might be a problem when transitioning from the narrow section to the flare. Granted I expect most people will round the angle with sand paper which will probably mitigate the problem. From a technical view though wouldn't this be a correct way of thinking that you would need to apply an appropriate radius to the hard angle between the narrow/flare joint?

For example I have a narrow port diameter of 177mm giving me a core limit of 29m/s and in HR I'm pushing 28.5m/s. In FI the chuffing limit is 9m/s @ 20hz with a decreasing limit at lower frequency. My peak narrow port velocity (S2) is at ~11.5hz so technically don't I need to increase the FI radius until I'm a bit past my peak velocity for that segment? Since FI doesn't show below 20hz I'd have to estimate based on the slope from 20-25hz which at 75mm radius is a 4m/s difference between 20-25hz; chuffing is at 30m/s at 20hz for 75mm. I could get more technical with estimating the slope based on what is shown but lets say the drop from 25 to 20hz is the same amount from 20 to 15 and 15 to 10 so I would need to be around 37m/s to hit 29m/s @ 10hz. 95mm radius gives me 38m/s chuffing at 20hz with a 1:1 velocity change wrt frequency (43m/s @ 25hz) so 95mm radius actually gives me a little headroom.

Name:  FlaredPorts.jpg
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Clearly the longer flare really just needs a quick once over with some sand paper but the shorter flare which is how I have the exit port modeled has an issue. The angle it creates represents a much smaller radius which will cause chuffing. So instead of using multiple segments why not just radius the ends? The savings in port length seem to be from being able to use a smaller than expected port limited by core issues and then just slowing the end points for chuffing but ideally we would want the flare to be as short as possible. If I take FI and change the diameter to include the radius on both sides from 177mm to 367mm with no radius, ironically chuffing is pretty close at 36m/s which gives me the idea that the expansion to that cross sectional area is what is needed to mitigate the air problems. What I'm getting at is technically with no flare you're dumping the port into an infinite flare within an infinitely short distance which doesn't work probably because of the air de-laminating from the surface suddenly. FI I'm guessing is assuming a perfectly circular radius following a sinusoidal path which I'm guessing is pretty efficient compared to other profiles like an exponential profile.

Reading what's on there at first they say above 10m/s air becomes turbulent at the egress points of the port then they turn around and say usable velocity increases with area which is contradictory. Anyway if you trust the program and what they say about increasing area gives more usable velocity then in theory we should be able to find a port size without radius that gives us a chuffing value slightly higher than our peak velocity at the required frequency, take the difference between that diameter and the diameter of the core and divide by 2 to get the radius we need to achieve the shortest flare. This won't really be practical because even using my 95mm radius that's about 3.75" so unless you have a 4" round over bit for a router or CNC you'll come up short. Also if I had to guess as to why adding the radii to the core diameter resulted in a slightly lower chuffing value of 36m/s compared to the core being radius-ed at 38m/s meaning we need a larger diameter with no radius to reach the 38m/s is probably due to the radius profile. The linear approximation of a radius would be a straight line at a 45 degree angle and I bet the diameter required to get the correct chuffing value is equal to the short side value of a 45,45,90 triangle with the same area as a quarter circle having a radius of 95. Annnd nope, it came out to 43m/s, needs about 385mm diameter for 38m/s chuffing limit with no radius.

Ok so that's a huge tangent! What I am curious about though is why are we holding the end of the flare to 10m/s instead of determining the 'diameter' of the flare end area and plugging that in to FI to make sure the chuffing value is acceptable for the velocity? Is that because it's not a sinusoidal profile? Also in FI is the radius part, part of the port length or is that in addition to?

Another random thought is what if the port exit top and bottom were parallel with the floor and the left and right sides were contoured to a radius, would that create a more horizontally radiating pressure wave? I imagine what comes off of the cone is spherical because the cone is conical (ignore the effects of the dust cap for this) but a horizontally flattened, flared port might reduce ground bounce effectively radiating that energy closer to the ground plane. I'm also thinking that a down firing sub and ports would have a better effect if the floor was a good transmitter since a lot of bass effects are things like the ground rumbling. Either way horizontally flattened, flared ports seem like they would make sense to keep those higher energy waves from interfering with the mains. After all is this similar to fluid dynamics? What about 2 ports with slightly different exit angles, angled at the side walls to control reflections and dispersion? What about tapering the port for useful beam shaping?

Sometimes I like to see where my mind takes me instead of following where other peoples minds have been... It's also late and this cricket won't shut up and I can't get rid of him.
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post #162 of 230 Old 09-13-2017, 04:20 AM - Thread Starter
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Ok I have one for you to critique. Same infinity driver ported using S1-S3 and throat chamber for the box.

S1: 180
S2: 92
S3: 92
S4: 180

L12 con: 5
L23 con: 70
L34 con: 5

Eg: 28
2pi
Rg: 0

Vtc: 180,000
Atc: 4,000

Filter: 2nd order butterworth HPF @ 18hz

I think I screwed up using conical but w/e it's tweaked enough for you to look at it.

Sealed box is 400L with 20cm to back and 1st order HPF at 28hz and Eg: 36.64. 400L is probably the most I'll get out of a 2'x4'x2' box, 20cm is to scoot the resonance anomalies further up the FR and squish them even though they are still visible a tiny bit in the upper band of what might be used.

The thought process behind the ported box was to go as big as I could within my envelope but also to focus that lower peak at 12hz even though the filter took most of that peak out.I also tried to keep port velocities close to their limits. Had to lower the power from excursion. If you want to have me do a ported design with different goals in mind just to see what I come up with let me know and if you have questions regarding what I was trying to accomplish with this design just ask. Otherwise I'm looking for a technical and practical analysis so I can understand technically both design intention vs execution and also goals vs reality.

I really thing the port opening should be able to be modeled after the chuffing value for that given area with no radius value but correct me if I'm wrong, I know that last post was something else. I'm going to bed, this keeps sucking more and more of my time. Just a heads up some time in the next day or 2 I'll be afk most of the time. I really do have to get back outside and finish the shed I was building and get started on the room remodel. I am not about to try and do a room remodel after I make my last trip for the rest of my belongings where I'll have stuff in the room and my 2 crazy cats to contend with!

Last edited by MeltManBob; 09-13-2017 at 04:36 AM.
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post #163 of 230 Old 09-13-2017, 05:10 AM - Thread Starter
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I really don't know why I'm still messing with this... Here's a larger ported version where instead of chasing port velocity so soon I maxed out what I think might be appropriate for my build envelope without getting super crazy on metric conversions.

Eg: 34.64
S1: 204
S2: 99
S3: 99
S4: 204
L12: 5
L23: 41
L34: 5
again conical, didn't remember to change them

Vtc: 350,000
Atc: 3,000

2nd order butterworth @ 26hz HPF

There's not much difference; top end is a bit smoother, resonances are closer, higher spl up top by 1-2db, little steeper roll off from 40 to 15, small peak at 12, group delay +~80ms
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post #164 of 230 Old 09-13-2017, 09:32 AM
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Edit - the rest of this is pretty much a tangent and starts to go off the deep end but w/e I'll post it anyway even though I had to re-read it a couple times to follow myself after I wrote it...
And as such I can't comment on all of it - there's just so many questions. I'm not a physicist and I'm not into fluid dynamics so I really don't know the answers to a lot of these questions. What I do know is that you can't flare out too abruptly. How much is too much? I'm not sure.

I'll just leave this link here - http://jahonen.kapsi.fi/Audio/Papers/AES_PortPaper.pdf

That's a good paper that should answer some of your questions. It also gets into Reynolds number and stuff that I've previously mentioned.

I'll comment on a few other things in your post but I'm pretty busy right now so I'll check your models in the subsequent posts later on.

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Regarding flared ports should I be double checking the end of the flared port against flare it? So far what I've noticed is that the flare length doesn't really matter so it seems best to get as much length from the 'narrow' portion and then just flare the last say 5-10cm.
You can check the port ends against Flare It if you want, but 10 m/s should always be pretty safe. In Hornresp, even if you flare out abruptly it will report that the velocity reduces - this isn't the case in real life - you can't flare out too abruptly or the air will just jet out the narrow part without expanding to fill out the whole flare. You need a slow(ish) transition so the air can fill out the flare and slow down.

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The other part of this is it looks like in flare it the chuffing is based on the radius which might be a problem when transitioning from the narrow section to the flare. Granted I expect most people will round the angle with sand paper which will probably mitigate the problem. From a technical view though wouldn't this be a correct way of thinking that you would need to apply an appropriate radius to the hard angle between the narrow/flare joint?
Sanding down the transition area certainly won't hurt, again, it's all about a soft transition, nothing too abrupt.

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Reading what's on there at first they say above 10m/s air becomes turbulent at the egress points of the port then they turn around and say usable velocity increases with area which is contradictory.
It's not contradictory if you know about Reynolds number, the boundary layer and how air does not move right at the physical sides of the port. The faster the air moves the thicker the boundary layer will get, which means the port actually gets narrower because the air at the edges isn't moving. So a larger port will choke less simply because it's larger.

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Ok so that's a huge tangent! What I am curious about though is why are we holding the end of the flare to 10m/s instead of determining the 'diameter' of the flare end area and plugging that in to FI to make sure the chuffing value is acceptable for the velocity? Is that because it's not a sinusoidal profile? Also in FI is the radius part, part of the port length or is that in addition to?
10 m/s is supposed to be safe in pretty much all scenarios. If you want to try to be more scientific about choosing a better value than 10 m/s using the tools you have at hand there's no problem with that.

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Another random thought is what if the port exit top and bottom were parallel with the floor and the left and right sides were contoured to a radius, would that create a more horizontally radiating pressure wave? I imagine what comes off of the cone is spherical because the cone is conical (ignore the effects of the dust cap for this) but a horizontally flattened, flared port might reduce ground bounce effectively radiating that energy closer to the ground plane. I'm also thinking that a down firing sub and ports would have a better effect if the floor was a good transmitter since a lot of bass effects are things like the ground rumbling. Either way horizontally flattened, flared ports seem like they would make sense to keep those higher energy waves from interfering with the mains. After all is this similar to fluid dynamics? What about 2 ports with slightly different exit angles, angled at the side walls to control reflections and dispersion? What about tapering the port for useful beam shaping?
A lot of this is beyond me, I'm not a fluid dynamics professor. What I do know is that at the bottom of the sub's passband the response is pretty much omnidirectional. At the top of the passband there is some narrowing of the beam but I'm not sure it needs to be controlled or that a port would be effective at controlling it much.

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Sometimes I like to see where my mind takes me instead of following where other peoples minds have been... It's also late and this cricket won't shut up and I can't get rid of him.
Read the port paper, that will put you to sleep and you can learn a bit from the pros in the process. Sorry I can't answer all your questions but you are getting really deep into the fluid dynamics and that's just not my area of expertise. Make the ports large enough (flared or not) to avoid compression, that's all I can really tell you.

I'll look at your sims later today when I get a chance.
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post #165 of 230 Old 09-13-2017, 02:06 PM - Thread Starter
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I finally get to sleep although I don't feel like I slept, good news though grandma is more or less back to normal at least with the secondary effects from removing the main clot. She's up and about a bit and able to speak! Can't really complain, I'll just sleep like a bear tonight.

Ok I'll just summarize all of those ramblings, some of it I won't get into too much because I realize I was just trying to connect dots that my 'spidey sense' was flipping out over. That happens a lot because of the huge variety of things I've looked into where things are familiar but in a different context and I'm trying to connect and translate.

Basically 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. For example the worst case is probably a triangularly expanding cone, then a quadrilateral expanding cone etc. but the point is linear expansion. Next would be flaring 2 parallel sides with a contour which was the thing I was talking about for the bass. In a perfect world horns would look like an instrument horn, uniformly contoured in 2D as it expands in 3D. The special case of 2 parallel sides with a contour I feel has the potential to guide and control the waves with high efficiency given the flare is sized appropriately. I'm not sure what that would be but with an appropriately sized flare assuming square-ish ports, you could control and support the waves enough to minimize energy directivity in the 2 parallel, non flared directions so that at the exit of the flare the only energy not being angled out by the other 2 parallel, flared walls is projecting forwards without much change in direction. Then turbulence would just be due to smaller areas of less energetic particles. I'm sure things could get more technical with the contour shaping of the flare if designing for a specific frequency such that instead of using a circular contour it might be beneficial to use a parabolic or hyperbolic etc. This is when talking about a true horn shape like an instrument. As you already pointed out 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.

What I do feel comfortable stating is that the shortest flare length can be determined from using the radius feature but then that added length will need to be factored back in to the port length, negligible or not, technically it should be true. Part of my thinking was to radius a curve to a point that transitioned to a straight piece to continue the length out to the desired exit area since anything more than about 1" radius requires special bits or beyond about 3-4" you need different techniques. Say instead of making the radius the full quarter circle you only did an 8th which would put you at a 45 degree angle and that's easy enough with wood to cut a piece to match and then you could make that piece as long as you needed to get to the full area. I'm just saying where the thought started, it's not practical unless you're already using a radius close to the full radius. Instead it's easier as I think you were explaining to use several segments to approximate.

Anyway I'm getting a feel for how some of this can be manipulated.

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. I'll have a look at that paper but my patience for reading thesis papers for relatively short answers is not very good! If I cared to test things in depth I imagine there are specific angles to use when transitioning into a flare wrt a desired limit of turbulence whether that be 1 segment for the flare or infinte. For a single segment, ideally you would want the transition angle infinitely small but the flare length would become infinitely long. I'm not sure and actually pretty curious to know if the relationships would be uniform or inversely related. For example if using a single segment you might think since as with a flare you're directing the air out at a 90 degree angle from the port that you would split that in half but intuitively that shouldn't sound right. For a 2 segment flare as a better example would you go with 2 30 degree angles or would you go with a 15 then a 30? I tend to think the latter makes more sense but whether it should be a relationship of nx or something else would be interesting. NX, n = segment piece, x = set angle, so segment 1 at 15 degrees, segment 2 at 30 degrees gives a cumulative 45 degrees and the remaining angle after the 30 to complete the full 90 leaves 45 giving you an angle sequence of 15,30,45.

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.

I look forward to going over the designs. I've been messing with the ABC boxes but other than getting a different slope I don't see much point unless that slope is more desirable. 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. Even better is there a program that can simply consider room gain from a basic rectangular/square cube? 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.
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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.

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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.

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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.

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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?

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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.

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I look forward to going over the designs.
Yeah, maybe later tonight.

Quote:
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).

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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.

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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.
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post #167 of 230 Old 09-13-2017, 07:57 PM
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I really don't know why I'm still messing with this... Here's a larger ported version where instead of chasing port velocity so soon I maxed out what I think might be appropriate for my build envelope without getting super crazy on metric conversions.

Eg: 34.64
S1: 204
S2: 99
S3: 99
S4: 204
L12: 5
L23: 41
L34: 5
again conical, didn't remember to change them

Vtc: 350,000
Atc: 3,000

2nd order butterworth @ 26hz HPF

There's not much difference; top end is a bit smoother, resonances are closer, higher spl up top by 1-2db, little steeper roll off from 40 to 15, small peak at 12, group delay +~80ms
Ok, sorry for the delay, I've been busy all day. I finally got a few minutes to play with this. First let's look at your sim.
Inputs, schematic, frequency response and excursion.



Continuing on, velocity at port mouth, velocity at narrow point of port and group delay.



What do I like about this? It seems you have the concepts down pretty well. I like the roll off on the low end, that should blend in nicely with room gain. It starts a nice roll off at around 40 hz. Nice. I also like how the resonances are way up outside the passband and very well controlled, the narrow spikes won't even show up in real life and you will have a nice frequency response without needing any stuffing.

What could be improved? The high pass filter is quite shallow and way too aggressive. See the excursion graph? Those two peaks can both be at the same height but your filter is choking off your port output. The box is bigger than it needs to be, which is not necessarily a bad thing, but it's unnecessary. The port flares out pretty quickly, probably a bit too quickly. If it was constructed as a round flare it would probably be just fine, but if constructed as a high aspect ratio rectangular flare with only one side expanding it might be a flared a bit too abruptly.

Overall this is a very fine first pass, very good work. As long as you checked Flare It to verify the narrow part of the port's velocity is fine then this is fine work.

Now for a bit of constructive criticism in the form of how I would likely design. I kept the same approximate tuning frequency, approximately same velocity at port middle and port end but I changed a few things.

I made the box a lot smaller, like 1/3 smaller. I made the port ends larger and with a slower flare rate. These two things required a much longer port, which is fine, it didn't cause any problems. I changed the filter to 4th order and put it at a frequency where it made both the excursion humps the same height. I also reduced power input from 334 watts in your design to 134 watts in my design.

Overall the performance of our designs is quite similar, we both have around 98 or so db at tuning, roughly same velocity at all parts of the port and roughly same group delay. Your design has more output above 25 hz but mine can be eq'ed up above 30 hz to have the same output, it can handle the power and excursion. So the designs are quite similar with the exception that mine is a lot smaller, it requires about 2/3 less power input and has less output above 25 hz (unless you eq it to be the same, which you can).

Here's my design. (Note - this is a quick 5 minute design, it's possible to optimize it in different ways for different goals sets if desired.)




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Hey I tried responding earlier but got that stupid expired token thing again. I sat down and really put some effort into addressing the frustration part of things but the site ate that post. Tried to rewrite it cliff notes style before I had to head out for an errand and it did it again. Anyway I'll get to it hopefully later but I just got home and need to eat. Long and the short of it is I'm not trying to frustrate you but we should sort out how best to go through this exchange of information so we're not getting frustrated.
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On a quick note, plug in the first set of parameters I put up, much closer to what you came up with.

The one you plugged in I left with the filter weird like that because I noticed it let me effect the pre-tune excursion with max power. That's one of the major differences between the 1st and 2nd design besides volume is the first design I adjusted power down and equalized the filter peaks where as the second design I went max volume on the box and power.

Anyway I'm calling it a night, slept like crap earlier.
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A pretty good rule of thumb is that you need about three times the capacity of sealed to reach the output of ported. If you want to have useful output at 10Hz you need a lot of cone area. At the very least I'd go 4 x 18" subs or the equivalent in smaller size drivers. Personally I'd probably go for something like 8 x Acoustic Elegance TD15H subs as a starting point. It's also a lot easier to make a good sounding sealed than ported imo.

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post #171 of 230 Old 09-14-2017, 10:54 AM
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Long and the short of it is I'm not trying to frustrate you but we should sort out how best to go through this exchange of information so we're not getting frustrated.
One thing that would help is if you would let me know what resources you have read, if you don't mention them at all I will assume you have not read them. For example, have you downloaded PCD, TL.app, Diffraction and Boundary Simulator and the Alignment Tables spreadsheet? Have you read the port paper and the Alignment Tables paper in their entirety? If not did you read specific parts of those papers? Which parts?

You might notice that I respond to almost every single thing you say, this lets you know that I'm paying attention and that I understand what you are doing. Even if I respond to say that I'm not going to talk about certain things in depth (like fluid dynamics) I'm letting you know where I stand on these things. When you ask questions I've already answered I'm not sure if you didn't read what I wrote, didn't read the links, didn't play with the software, or simply didn't understand some detail of something.

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On a quick note, plug in the first set of parameters I put up, much closer to what you came up with.
Yes, ok, that's much better. The filter is set properly (although I'd still probably use a 4th order) and your first design is almost exactly the same as my example. I'm still a bit worried that the port might be flaring out too fast but it depends on how you actually construct it in real life. Overall very good work.

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The thought process behind the ported box was to go as big as I could within my envelope but also to focus that lower peak at 12hz even though the filter took most of that peak out ...
Yeah, the high pass filter is almost always going to take most of the peak out, that's life. And in real life it doesn't matter if you actually use a high pass filter or not, that's the most you are ever going to get out of the peak at tuning since this the strength of this peak is limited by xmax. So what you show with the high pass in place is the most you can get out of the design at tuning whether you use the high pass or not. Both Steve and myself have indicated that you don't necessarily NEED to use a high pass filter, especially if you are very careful, but it's good to sim with it in place so you get a realistic idea of the max potential output you can get at the low knee.



Now where are we going to go from here? Assuming you are going to stick to your 2x2x4 ft box size, sealed and ported are really the only realistic options. Do you want to make a more finalized plan or do you want to continue learning other things?

I can strongly suggest that you consider IB - if you can just cut a hole in the wall and vent into an adjacent room, an IB manifold is the smallest possible box you can possible get away with, you can fit five 18s on a 18x18x18 inch box. IB will also give fantastic performance, much better than a smaller sealed box. (Even 2x2x4 ft is small compared to IB.)

Or we can get into the larger stuff like tapped horns and horns. These will kick the crap out of a ported box but they will have to be MUCH larger than your size goal. It's nice to learn about them even if they won't fit.

There's also the ported/slot loaded option popularized recently by Ricci, it combines the benefits of ported for the lows and tl/horn for the highs (similar to bandpass but doesn't use small ports like most bandpass boxes and it can have a nice wide bandwith, unlike most bandpass).

I would suggest that you get a firm grasp of all the options before finalizing any plan. You should sim IB, tapped horn, front loaded horn, ported/slot loaded, maybe a few examples of tl. Find out how everything works. Then you are in a much better position to determine how to realize your goals.

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Subs response at LP with no EQ


But look at all the 3hz output you're missing
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But look at all the 3hz output you're missing

That low stuff creates the pressure in my room and my dual XXX ported creates just as much and more tactile as well. The UMIK I have does not have any cal files below 10hz so it drops off a cliff and I bet I would gain at least 10-15 dB at 5hz, This is using the Inuke 6000 as well, no dsp needed.

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post #174 of 230 Old 09-14-2017, 12:06 PM
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That low stuff creates the pressure in my room and my dual XXX ported creates just as much and more tactile as well. The UMIK I have does not have any cal files below 10hz so it drops off a cliff and I bet I would gain at least 10-15 dB at 5hz, This is using the Inuke 6000 as well, no dsp needed.
I was just kidding, but most umiks are down 5-6db at 5hz compared to 10hz
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I have my cross spectrum labs report in hand and it shows on this mic it was down -2.20db at 5hz........starting at a 10hz of -.56db


Where the Umik really dives is up top....-54.66 db at 25k, but it is only -2.47 at 20k.


I am sure all mics vary some.......


The biggest variances are at 8k thru 12.5k where it is + 3.17 db.



So from 5hz to 20k it is +/- less than 3db uncalibrated.

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post #176 of 230 Old 09-14-2017, 01:42 PM
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Subs response at LP with no EQ


It's probably also pretty important to mention that your results are nowhere near typical due to your basement bunker-like room. I certainly wouldn't get results like yours in my house - I have no basement and not even any brick walls.
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Mine graph is in a non soundproofed room with paper thin walls and a single 18.........


Ported or sealed....running with no HPF gets down low.


Attached Images
File Type: jpg sealed.jpg (59.9 KB, 592 views)
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post #178 of 230 Old 09-14-2017, 01:50 PM
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I have my cross spectrum labs report in hand and it shows on this mic it was down -2.20db at 5hz........starting at a 10hz of -.56db


Where the Umik really dives is up top....-54.66 db at 25k, but it is only -2.47 at 20k.


I am sure all mics vary some.......


The biggest variances are at 8k thru 12.5k where it is + 3.17 db.



So from 5hz to 20k it is +/- less than 3db uncalibrated.
My UMIK CSL cal file is quite similar to yours, although just a touch less accurate (without the cal).

10 hz is -0.87.
5 hz is -4.51 db.

I've got the same weirdness at high frequencies but my hump is pretty broad (5000 hz - 12000 hz or so) and peaking at 3.17 db at 10 khz.

So out of the box your capsule is a bit more accurate than mine, although with the cal of course they should all be dead flat across the entire bandwidth (obviously since that's the point of the cal).
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post #179 of 230 Old 09-14-2017, 01:53 PM
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Mine graph is in a non soundproofed room with paper thin walls and a single 18.........


Ported or sealed....running with no HPF gets down low.
What can I say? That's not a typical result.
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post #180 of 230 Old 09-14-2017, 02:52 PM
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I was just kidding, but most umiks are down 5-6db at 5hz compared to 10hz

I know you were. My Umik is from minidsp and not cross spectrum. I received it bundled when I had the NanoavrHD a while ago and its cal file was -7dB at 10hz so it will be more at 5hz.
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