Absolutely I have. I am carefully digesting your sims just-a-guy - and also the sims that Bob4 posted. You guys make a very convincing case (computer aided) for running a single bass horn. Believe me – I REALLY like the thought of building just one 60 ton concrete horn – but I just want to make sure that I’m doing so for the right reasons - which is fidelity, and not necessarily cost & labor savings. You guys have convinced me that a single bass horn is the way to go for my project..
What I have also inferred from your postings, is that depending on where I crossover my bass horn, the mid-bass (aka kick) horns might have some serious lobing issues also. This is why I’ve spaced them directly adjacent to the “single” bass horn (about 30 feet apart on the mid-bass horns, center-to-center). As far as the crossover, I intend to purchase the latest & greatest digital processing gear for my crossover, and delay circuit (within monetary reason) - I'm assuming the available roll-off rates will be more than adequate.
Can you please elaborate (provide your two cents) on post 588, 592, and 593? The half-space plane is parallel to my horn (aka the ground), and specifically not perpendicular to it. If hornresp assumes my bass horn is shooting directly into the sky, then this will not work for me. The only part of my horn that is perpendicular with a half-space plane, is the relatively small wall that the horn’s built into. Should I be building a full-space horn?
Last edited:
More food for thought.
Hi Entropy455,
Post #588: "...Is there a rule-thumb for the aspect ratio?...I must transition to round in the throat..."
I don't think there is (a rule of thumb for anything this size), also keep in mind the mirror image formed by the ground reflection: a 2 wide by 1 high horn would appear as a 2 wide by 2 high image; or, 4:1 equivalent to 4:2 (2:1). Your sound wall design would probably give you additional SPL at higher frequencies, i.e.: it would change from 2pi to 1pi. Again, this is best determined by experiment. I like the reduced spread you show in #592; the elevated L/R speakers sitting above wall extensions (or, barn doors) would be my first choice, at least it would keep people from wandering right into the L/R horn openings, and get their ears blown out. Maybe then the wall structure should be extended to the tops of the L/R speakers. How big a stage do the Chili Peppers need, anyway? 🙂
If you use construction method 2 you should still have a vertical horn mouth. Just model accordingly, Hornresp takes care of the "horn bubble" and the radiation angle consideration for you.
How many drivers enter at a common throat will determine the throat geometry. If each driver couples to, e.g.: an 8ft long conical initial section (wood?), there is no reason to make the subwoofer horn throat anything but square. The overall horn shape should be hypex, it can be composed of individual conical (straight sided pyramids) segments. Obviously, you need to design for optimum throat chamber volume, and take cancellations into consideration. Things change a bit when you are talking about the mid-bass horn, here a phase plug will be necessary.
Neat picture with the Boot. Very cool!
Regards,
Hi Entropy455,
Post #588: "...Is there a rule-thumb for the aspect ratio?...I must transition to round in the throat..."
I don't think there is (a rule of thumb for anything this size), also keep in mind the mirror image formed by the ground reflection: a 2 wide by 1 high horn would appear as a 2 wide by 2 high image; or, 4:1 equivalent to 4:2 (2:1). Your sound wall design would probably give you additional SPL at higher frequencies, i.e.: it would change from 2pi to 1pi. Again, this is best determined by experiment. I like the reduced spread you show in #592; the elevated L/R speakers sitting above wall extensions (or, barn doors) would be my first choice, at least it would keep people from wandering right into the L/R horn openings, and get their ears blown out. Maybe then the wall structure should be extended to the tops of the L/R speakers. How big a stage do the Chili Peppers need, anyway? 🙂
If you use construction method 2 you should still have a vertical horn mouth. Just model accordingly, Hornresp takes care of the "horn bubble" and the radiation angle consideration for you.
How many drivers enter at a common throat will determine the throat geometry. If each driver couples to, e.g.: an 8ft long conical initial section (wood?), there is no reason to make the subwoofer horn throat anything but square. The overall horn shape should be hypex, it can be composed of individual conical (straight sided pyramids) segments. Obviously, you need to design for optimum throat chamber volume, and take cancellations into consideration. Things change a bit when you are talking about the mid-bass horn, here a phase plug will be necessary.
Neat picture with the Boot. Very cool!
Regards,
Last edited:
If you are comfortable with the idea of the single center position sub horn we can look into the mains positioning. There is naturally going to be comb filtering going on between the mains L + R, that's natural. With a bit of help from the simulator we can investigate how bad it's going to be with different placements.
Hornresp assumes the sound source(s) are flush mounted with the Ang boundaries. The Ang boundaries in Hornresp are also assumed to be infinitely sized, so it's a perfect reflection at all frequencies.
So for full space there's no reflective boundaries anywhere near the speaker. In 2 pi the sound source (horn mouth) is flush mount with the single boundary (buried in the ground pointing up). In 1 pi the horn mouth would be directly at the junction of the floor and wall boundary (which isn't actually even possible, as the horn mouth surface area is flat and that wall/floor junction is a 90 degree angle). With 0.5 pi the sound source is located at the junction of the two walls and the floor (which also isn't possible for the same reason).
This doesn't mean the sim is useless, it's usually more than enough information to work with. But it doesn't accurately reflect cases where the sound source is placed a significant distance away from the boundary. If you want to get a good handle on the particular situation where the sound source is NOT flushed mounted in the boundary, or if the boundary is less than infinitely large, you need to use different software to get a picture of that, like I showed.
As the boundary sim shows, if the wavelength is long compared to the boundary then the boundary doesn't provide a reflection, the wave wraps around the boundary and a good portion of it goes backwards. When the boundary is sufficiently large compared to the wavelength, the wave can't wrap around it and all of it gets reflected forward, so you get +6db in the forward axis and nothing wraps around and goes backward. That's the boundary size issue summed up.
Then there's Allison effect. This is effect you get when you put a sound source in front of a boundary instead of flush mounting it on the boundary. When the wavelength is long compared to the distance from the center of the sound source to the boundary the reflection is pure and you get +6db. Remember, sound sources that are within a 1/4 wavelength of each other sum perfectly for +6db, and a reflection is a sound source. But when the distance from center of the sound source to the boundary is shorter you get a notch in response, notches are usually a 1/2 wave phenomenon. This is because of wavelengths and distances. (It's always wavelengths and distances.) With the shorter wavelengths in relation to reflection distance (higher frequencies) the sound that comes direct from the sound source arrives before the reflection because the reflection has to travel farther than the direct wave. When the direct and reflected sound sources meet at the listening position they are out of phase so you get a notch at certain frequencies.
So Hornresp is assuming that the Ang boundaries are infinitely large and Hornresp doesn't bother with Allison effect because it always assumes the sound source(s) are flush mounted, in which case there is no Allison effect. That doesn't make the Hornresp sims useless, just not complete when these two conditions are different than what Hornresp assumes.
In the case of the big sub horn, the ground is infinitely large, so no problem there, a 2 pi sim is good to go, at least at the lower frequencies. But the sim won't show Allison effect notches because Hornresp assumes the horn mouth is flush mounted into the ground and it won't show the effect of barn doors unless you simulate them as baffle diffraction. If the barn doors were infinitely large you could just change the sim to 1 pi, but they are not that big (and you still wouldn't see the Allison effect notches due to the center of the horn mouth to floor distance).
To answer your question specifically, no you should not be building a full space sub horn (unless you want to, it won't hurt, it will actually be a bit better because bigger is almost always better but way past the point of diminishing returns).
If you design a 2 pi horn and use it in a 2 pi environment the sim will be accurate as far as the simulator's assumptions go. But the sim won't include Allison effect notches and it won't include the effect of shifting from 2 pi to full space as frequency increases because the sim assumes it's flush mounted and your physical horn is not.
As for the mid horns, I forgot about the barn door. This is a boundary for the midbass horn (in addition to the ground boundary), and size of the barn door and whether the midbass horn is flush mounted into the barn door or not will affect the Allison effect notches and the transition from 1 pi to 2 pi.
As for the drawing in post 588, I can't see it in 3d and since it's not to scale I can't tell if you have parallel walls of if all 4 (or all 3 in the second case) walls are expanding. Assuming there are no parallel walls, I don't see any practical difference, the slight bend in the second example isn't going to do anything at all at subwoofer frequencies and these two examples should be pretty much functionally identical. I would think the second one (the one with the flat bottom) would be a whole lot easier to build though.
Last edited:
As I've stated a few times before, I'm not convinced separate kick horns are necessary.
The DBH218 I've used for the sims is specced up to 300 Hz.
Or the 12pi horn:
http://www.pispeakers.com/12Pi_flyer.pdf
According to the datasheet it has a recommended operating range up to 150 Hz, and the graph shows that it has good output up to 200 Hz. Note that this is a folded horn. The folds are restricting the response on the upper end of the horns bandwidth, and might cause resonances ("honking") that dictate a low crossover frequency. This is a common design compromise to make FLHs viable and transportable.
You are planning a straight FLH without folds. I have a hunch that this should have no problem doing the same or going even higher, while sounding good.
It would be nice to see
A) if the horn CAN be designed to go that high (& what kind of compromises this entails ), and if built this way, how it behaves and sounds playing that high
B) how the system sounds if the horn is coupled in the kick bass / low midrange region, and if this causes audible problems (lobing? stereo image distortion?)
Actually this approach is compatible with your idea as well. If you feel that you are not happy with the kick, you can still lower the crossover point and add your stereo kick horns. But as a benefit, you could iterate your system first with smaller tops (faster to build, less complex)
By the way, I can't resist recommending the Peter Morris DIY top once more. I would love to build it myself, or at least hear it...... supposedly it has ultra high fidelity when run with Dolby Lake FIR processing.... 
it goes down to 80 Hz too........
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
it goes down to 80 Hz too........
In a half-space calculation, Hornresp does not appear to return a full-space horn, with the expectation that the user slices the horn in half and setting it on the ground (in direct contact & parallel with the half-space plane). Hornresp directs the construction of a half-space horn.
A more specific example - in a half-space calculation, when I select a petal horn with six sides, hornresp tells me to build a half-space six sided petal horn - and specifically does not direct that I cut a full-space six petal horn in half (i.e. to build only three of the six petals, and join the horn with the half-space plane).
I thought I had figured out this half-space loading thing - and now I am VERY confused again. As I understand it, both of these horns below are "half-space" horns, where one is joined (more directly) with the ground - they are specifically not full-space horns sliced in half and joined directly with the half-space plane.
Last edited:
Question - does a half-space horn have to be physically coupled to the half-space plane, to achieve ideal performance? My bass horn's mouth will specifically NOT be flush with the ground (i.e. earth joined around the whole circumference of the mouth - with the horn perpendicular & pointing into the sky)
Here's a problem: only one rectangular mouth edge will be flush with the half-space plane, and my horn is going to be parallel with the plane (90 degrees from optimum). Will this negatively impact the impedance coupling with the ground?
What if my horn had a round mouth, and were only touching the half-space plane via tangent point? Would the impedance coupling with the half-space plane be further degraded. One would think the coupling would be less than ideal, right? Or are bass horns in half-space a bit like horseshoes, hand grenades, and nuclear weapons - - - where close counts?
The entire first half of this thread consisted of people (including David McBean) talking me out of the need to build full-space bass horns. Some of the recent comments however are challenging my understanding of half-space loading (and that's assuming I actually had an understanding to begin with. . . .)
Here's a problem: only one rectangular mouth edge will be flush with the half-space plane, and my horn is going to be parallel with the plane (90 degrees from optimum). Will this negatively impact the impedance coupling with the ground?
What if my horn had a round mouth, and were only touching the half-space plane via tangent point? Would the impedance coupling with the half-space plane be further degraded. One would think the coupling would be less than ideal, right? Or are bass horns in half-space a bit like horseshoes, hand grenades, and nuclear weapons - - - where close counts?
The entire first half of this thread consisted of people (including David McBean) talking me out of the need to build full-space bass horns. Some of the recent comments however are challenging my understanding of half-space loading (and that's assuming I actually had an understanding to begin with. . . .)
Last edited:
Hi Entropy455,
Post #606:"...Hornresp does not appear to return a full-space horn, with the expectation that the user slices the horn in half..."
That is correct, as I see it Hornresp simulates the behaviour of the horn as specified. It applies the horn output to a user specified environment; thus, the same horn will produce different output levels according to the radiation angle choosen. Some people will design all their enclosures in 4pi (free space), and adjust the results for the application environment.
Your L/R enclosures standing on the ground (no wall) would be radiating into a 2pi environment (half space), if you were to hoist them up 20ft 4pi would be more appropriate; or, if you mount them into a wall with 10ft wall all around them, and the enclosures sitting on the ground, then it's 1pi (or so). Additionally, the summation of different sound sources is not an even +6dB independent of frequency, and you'll have higher high frequency losses at long distances than low frequency losses.
The software solutions mentioned are very helpful to get a system into the ballpark, but then you have to make adjustments based on measurements and listening.
Regards,
P.S.: Post #608: "...Question - does a half-space horn have to be physically coupled to the half-space plane, to achieve ideal performance? My bass horn's mouth will specifically NOT be flush with the ground (i.e. earth joined around the whole circumference of the mouth - with the horn perpendicular & pointing into the sky)..."
Consider it in terms of wavelength, at 10Hz it will couple to the ground @ 200Hz it will probably not couple that well (it will be much more directional). Still and all, a full-size horn will have directional qualities, and the final answer will be in the measurements.
Post #606:"...Hornresp does not appear to return a full-space horn, with the expectation that the user slices the horn in half..."
That is correct, as I see it Hornresp simulates the behaviour of the horn as specified. It applies the horn output to a user specified environment; thus, the same horn will produce different output levels according to the radiation angle choosen. Some people will design all their enclosures in 4pi (free space), and adjust the results for the application environment.
Your L/R enclosures standing on the ground (no wall) would be radiating into a 2pi environment (half space), if you were to hoist them up 20ft 4pi would be more appropriate; or, if you mount them into a wall with 10ft wall all around them, and the enclosures sitting on the ground, then it's 1pi (or so). Additionally, the summation of different sound sources is not an even +6dB independent of frequency, and you'll have higher high frequency losses at long distances than low frequency losses.
The software solutions mentioned are very helpful to get a system into the ballpark, but then you have to make adjustments based on measurements and listening.
Regards,
P.S.: Post #608: "...Question - does a half-space horn have to be physically coupled to the half-space plane, to achieve ideal performance? My bass horn's mouth will specifically NOT be flush with the ground (i.e. earth joined around the whole circumference of the mouth - with the horn perpendicular & pointing into the sky)..."
Consider it in terms of wavelength, at 10Hz it will couple to the ground @ 200Hz it will probably not couple that well (it will be much more directional). Still and all, a full-size horn will have directional qualities, and the final answer will be in the measurements.
Last edited:
My bass horn could do surprisingly well up to 300 Hz (I don't know - I've never heard one before.) The reason I want kick horns, is because I will lose all stereo separation in the business end of my music (80 to 300 Hz), if I cross my bass horn at 300 Hz. Even if I cross at 160 Hz, I'll still lose an entire octave of "kick" stereo separation. Is this really a problem? I don't know. I am a little disappointed that my "no-compromise" horn system will ultimately be loaded with compromise.
My thought was that I'd build my mono bass horn out of concrete, then I'd build some 80 Hz stereo mid-bass horns out of wood, and simply listen to it. Adjusting the crossover frequency is a simple electronic adjustment. Believe me - if a crossover point of 300 Hz sounds best, that is absolutely where I will set the system.
I fully anticipate having to construct several iterations of mid-bass horns before I find the sound I'm happy with. If I only need 160 Hz mid-bass horns, that's all the larger I'm going to build them. . .
Last edited:
Hi Entropy455,
Post #610: "My bass horn could do surprisingly well up to 300 Hz...If I only need 160 Hz mid-bass horns, that's all the larger I'm going to build them..."
That's the current problem, until you have the finished bass horn you'll just not quite know, will you?
Regards,
Post #610: "My bass horn could do surprisingly well up to 300 Hz...If I only need 160 Hz mid-bass horns, that's all the larger I'm going to build them..."
That's the current problem, until you have the finished bass horn you'll just not quite know, will you?
Regards,
DISTANCES AND WAVELENGTHS. I just got done giving a very in depth answer. TB46 essentially said exactly the same thing.
When the wavelength is long compared to the distance to the boundary they will couple fully (+6db). This is because sound sources within 1/4 wavelength of each other act as a single sound source.
When the wavelength is shorter problems happen. This is because of the triangulated distance between the sound source, the reflection and the listener. If the listener is equidistant to both sound sources all is fine. When the listener is not equidistant to both sound sources one source arrives before the other and they will be somewhat or completely out of phase. Completely out of phase usually happens at 1/2 wavelength and provides a deep notch.
Maybe you've heard of floor bounce and maybe you've heard people talking about placing absorbtion in their rooms at the primary reflection points. This is because of the Allison effect and it's what the Bagby spreadsheet shows very clearly.
Because your horn mouth is so large, it can't be within a 1/4 wavelength of the primary boundary (the ground) at frequencies at the top of it's passband. So you can pretty much count on a little floor bounce. There's not a whole lot you can do about that.
This is not a deal breaker, if it was horns like this would not exist.
https://mniec.files.wordpress.com/2012/11/320x.jpg?w=320&h=239[/quote]
Forget the horn mouth shape. Ideally you would make it as close to a perfect hemisphere as possible and the ground would mirror image the other half (as well as it can, you still have Allison effect) but the difference between half round, round, square or rectangular comes down to distances and wavelengths. (There's also differences in other things too, like directivity and frequency response if you aspect ratio gets really high but let's ignore that for now.)
As theoretical concepts this is all pretty simple. Distances and wavelengths.
In your setting, no need to worry about horn upper limit. But stereo considerations in using a mixed-bass sub require a steep slope crossover around maybe 100-130.
Alternatively, you could consider some non-stereo creative solutions.
Your design challenge is that your horn is too good. You now have to think about what will match the horn's capability the next bands up. Kind of problem everybody wishes they had.
B.
Alternatively, you could consider some non-stereo creative solutions.
Your design challenge is that your horn is too good. You now have to think about what will match the horn's capability the next bands up. Kind of problem everybody wishes they had.
B.
Yeah, don't count on that. I told you probably 3 or 4 weeks ago not to count on getting the upper bandwidth that the sim is showing.
I'm guessing you are still doing all your sims as Nd horns. It's going to be very difficult to actually build an Nd horn with a 4:1 compression ratio. In order to do so your throat chamber would have to match the size of the driver baffle holding eight 18 inch drivers to the size of the horn throat - in other words the throat chamber would have to be have a pretty severe reverse taper or a huge area step where the throat chamber meets the throat.
To sim what you are most likely going to build, with drivers on the sides of the horn as per all the previous discussions in this thread, you need to do an Od sim. With an 18 inch driver on the side of a horn, the closest you can possibly push it towards the closed end of the flare is about 23 cm (center of driver to closed end of flare).
Remember wavelengths and distances and boundaries? 1/2 wavelengths and notches? When the center of the driver is 23 cm from the closed end of the flare you get a huge notch in response.
This is just an example - a 32 hz full size horn with eight 18 inch drivers. In the top row you see the schematic and frequency response when it's simulated as Nd. In the schematic it actually looks workable but it's only because the 8 drivers are shown as one large round composite driver - the baffle board holding those 8 drivers in reality would need to be MUCH larger than the throat.
In the second row you see the exact same horn but with the 8 drivers clustered around the horn as close as possible to the closed end. See what that boundary reflection off the closed end of the horn does to the frequency response?
An externally hosted image should be here but it was not working when we last tested it.
And if you decided to do two rows of drivers (so the first driver was centered 23 cm from the closed end of the flare and the second was 69 cm from the driver center to the closed end) the average distance from drivers to closed end would be 46 cm from the closed end and the huge notch would move down to 200 hz (from the pictured 400 hz).
Also, I'm not sure which 18s you are using to sim, but the ones I use don't usually do that well up to 300 hz even in an Nd sim.
All in all (and this is just a couple of factors, there are others) I think the chances that your big horn is going to be playing well up to 300 hz are between slim and none. Some of these other factors include directivity (your big horn is going to beam like crazy at 300 hz, it will only be about 40 degrees wide according to Hornresp) and the fact that if you cross anywhere near as high as 300 hz I think it will be easily localizable with the mains at 16 feet to either side of the center of the horn.
An externally hosted image should be here but it was not working when we last tested it.
Last edited:
Just for comparison (since that probably doesn't mean much on it's own) here's the beamwidth of the same horn at 20 hz. Pretty big difference, it narrows significantly at 300 hz compared to 20 hz.
And to put this into perspective, your horn has higher directivity at 20 hz than a "regular" sized horn has at the top of it's passband. Here's a 500 liter flh DI at 128 hz, it's DI is slightly lower than your horn at 20 hz. Because of the sheer size of your horn it's got very significant directivity and this can't be ignored.
An externally hosted image should be here but it was not working when we last tested it.
And to put this into perspective, your horn has higher directivity at 20 hz than a "regular" sized horn has at the top of it's passband. Here's a 500 liter flh DI at 128 hz, it's DI is slightly lower than your horn at 20 hz. Because of the sheer size of your horn it's got very significant directivity and this can't be ignored.
An externally hosted image should be here but it was not working when we last tested it.
Last edited:
I found this by accident while looking for something else, it speaks to Djim's comments about transients. At the time I wasn't considering how VERY short transients would affect things, and indeed they would have to be very short. Even with a 30 foot spacing the transient would have to be less than 30 ms long to change anything. Anyway, this speaks to transient behavior and what happens. From here - Loudspeakers, Mutual Coupling and
(The paper is about mutual coupling in general, so if you want to learn about these things through math instead of pictures and sims give that link a shot. I don't like math so I just skimmed it.)
(The paper is about mutual coupling in general, so if you want to learn about these things through math instead of pictures and sims give that link a shot. I don't like math so I just skimmed it.)
Last edited:
Let's not get too carried away here. OP hasn't updated us with his new design for eight 18s yet, but if you compare his original design (the 32000 liter horn with 5x 12 inch drivers) with a stack of 8 Labhorns, the Labs blow it out of the water. OP's 20 hz horn will obviously go a bit lower in frequency but the Labs are much louder.
Shown here is OP's original design at xmax compared to a stack of 8 Labhorns at 6400 watts (full rated driver power).
An externally hosted image should be here but it was not working when we last tested it.
The Labs might have a bit of power compression at this power level, OP's horn won't, so subtract a couple db from the Labs if you like. The Labs still slaughter OP's original horn design in most performance metrics (except low frequency extension).
If OP's new design uses eight 18s that will give almost 4x more displacement potential which would make OP's horn slightly louder than the Lab stack, but not much.
So let's keep things in perspective. A stack of 8 Labs is loud and the extra 10 hz extension that OP's horn will have is also nice. But let's be serious here, this might not be the best performing system in OP's county, it certainly won't be the best in his state, and on a national level it's not even noteworthy from a performance perspective. Some of those South American street system with a couple hundred subs that can visibly move your hair from a couple hundred feet would eat this horn alive. Sure, it's going to be a lot better than what most of us have but if it's not a lot louder than a stack of Labs it's pretty passe by big system standards.
Eric,
This "tread" continues to amuse me.
1)Yes it could. Do you want to hear the low end of vocals and instruments "walk" with their pitch (frequency/note) around your bass horn and upper reproducers located in different L/R directions? I certainly would not, but just one opinion, just like a-holes, we all have one.
2) Christ on a Stick, you are just not listening, and have not listened to the problems associated with large scale audio reproduction.
3) Welcome to the real world 🙂 .
4) "Sounds Best" for what genre? See response #2, for the real sh#t.
5) Good for you, if you construct several iterations of mid-bass horns before you find the sound you are happy with, and do it at the rate of folks that actually get paid for what they do, you could achieve your goals in another decade or so, if you are able to separate the wheat from the chaff 🙂.
Have fun,
Good luck!
Art
I don't think I am. A straight full size 20 Hz horn, or half of one on the ground, is one of the holy grails of audio possession. Fortunately this system will not have to deal with indoor boundaries or substantial reflected energy.
For rock the LF energy level / hump will have to extend to about 250Hz and that will require substantial attention to properly ballance and sound right as well.
I get that this is DIY but, a single DSL TH812 box will best an eight stack of Labs (which are a pain in the balls to build anyway so you can have em!) and a single TH221 or pair of BC218's would likely be all that is needed to fully satisfy the 20Hz desires but, again I get that anyone can just go buy it.
I am interested in this project because this is something I would like to do as well just 'cause. Unfortunatley I have neighbors within rifle range. Grrrr.
A pair of BC218's and a pair of J3-96's is all I would need, for the patio. 🙂
Barry.