I keep posting this when this common misconception rears it’s head:
https://www.acculution.com/single-post/037-misconceptions-in-acoustics
https://www.acculution.com/single-post/037-misconceptions-in-acoustics
Hmm, we know there will be standing waves... the idea is to change the shape and size of the dimensions so that the nodes are spread around the volume... IMHO, that article misses that point.
But how important is it, to distribute modes, compared to eliminate secondary sound source on the outside? Damping material inside takes care most of standing waves anyway, leaving few lowest modes a possible problem that could audibly hear through, lowest being the worst. That would be sound coming half wavelength late at exact same location as direct sound, through cone, so should be seen in frequency response plot and be heard as anomaly in frequency response I think. If its there, notch it out with EQ. Spherical enclosure ought to be stiffer than rectangular one, so the "box" itself is not too hard to make quiet I think.
Anyone building such things, sounds better or worse than a box with the amount of work and money invested?
Anyone building such things, sounds better or worse than a box with the amount of work and money invested?
Perhaps, but nothing would be better than damping them out. Spreading them is good too, but it could add a non-minimum phase component. That may be OK for bass in a room, but at higher frequencies we might feel differently.
Anyone who can ask this question is not going to say oh, what shape can I use which is good for both. They will make each one different somehow.
(Maybe this is what you meant by saying this?)
Yes, basically I just meant that some things might be more important than others, and I'm not sure what the order is as everything is interrelated and systems are a compromise between various things for various reasons. Certainly, if some problem was solved by introducing some other issue, did the sound get better or just different?
Like you say, optimal solution to any audible issue requires that one doesn't introduce new issues. For very least any new issue needs to be less audible, or solvable with some other compromise.
For example, taking "box noise" as lumped issue and edge diffraction as another. Geddes found out in a study that linear distortion like these are more audible with higher SPL, so perhaps either is an issue for most systems at home, regardless of the construct, since listening level is usually quite low?
Then, people who can say that box noise is more important than edge diffraction, or vice versa, are rare. Not sure if anyone has claimed on this forum for example, how edge diffraction exactly sounds like. Surely I don't know yet. It might be just a spatial effect, for example, inaudible on some circumstances and so on. Perhaps I do hear it but I just cannot make the connection.
Box sounds, as an example, can be quite audible at least in some context. I know my big bass boxes played party loud had quite distinct sound to them, box sound that was distracting, for what ever reason. Big bass box is ~100 litre or more. It was no issue at leisure listening, but crank it and it's quite obvious that something was not sounding right. Had to build new boxes, halved the volume, better bracing and damping and it seems better now. Trading off some bass capability for better midrange was fine, there is still plenty enough bass for home since there is DSP and enough power.
There is no need to have either, significant issues with diffraction or distracting "box sound", they can be separated and optimized: boxes are really needed only for bass, roughly room sized wavelengths, and diffraction shows around midrange, wavelengths that are roughly size of the construct. Diffraction is something we cannot avoid as its property of sound and how it interacts with physical objects, but addressing it with some suitable way is not too difficult. It could be a sphere a box, or more generalized just a good waveguide.
Last edited:
When it comes to room acoustics, bass is all we care about.... Higher frequencies do not have standing waves... they may have echoes, but that's another issue.
Speakers are a different matter, since they are much smaller, the ratio of the wavelength of the midrange to the the cabinet dimensions is still significant. But as you note, damping the midrange is possible, bass I'm not too sure. At this point I'd have to yield that discussion to actual speaker builders.
All this talk about standing waves in spheres seems to come from people who have not built and tested one. Several factors are always ignored by people making these standing wave warnings. 1. To maximize the standing wave you would mount a speaker on a flat plate with a half sphere enclosure behind it. This as it turns out works very well. The frequency of that lowest order mode is very high and all the other modes are even higher in frequency. It is likely that any high quality, high density damping material will very effectively damp that first mode and therefore easily damp all the higher modes as well. There is of course the option to simply use a low pass crossover to avoid using the speaker at and above that first mode frequency effectively avoiding all internal box modes. 2. Just because the external shape of the enclosure or waveguide is a sphere, you don't have to have an internal volume for the driver shaped as a sphere. An internal enclosure can be created behind each driver of any shape that will fit in there. I have used long highly damped tube enclosures behind drivers mounting on a sphere. The sphere can also be filled with various hard reflective items to act as diffusers and breakup the modes.
In formal logic, what you just did is "moving the goal posts".
The discussion is on making a spherical speaker. What you described is NOT a spherical speaker, rather something that LOOKS like a spherical speaker.
Of course, I did that too earlier. I presented the idea of mounting the speaker on a semi spherical baffle ( no step ) and loading the rear in other ways.
The discussion is on making a spherical speaker. What you described is NOT a spherical speaker, rather something that LOOKS like a spherical speaker.
Of course, I did that too earlier. I presented the idea of mounting the speaker on a semi spherical baffle ( no step ) and loading the rear in other ways.
I didn't move the goal posts, I cut the entire stadium in half. As I said, "to maximize the standing waves" you can to build something that isn't a spherical speaker. As it had already been mentioned before many times in the thread, mounting drivers on the sides of an actual sphere does not maximize the standing waves in a spherical enclosure. You need to pump the mode in a spherically symmetric way, an example of that would be from the center. My example was to illustrate how to approximate that. Even if there is a very high Q standing wave mode, that might be just fine if the system design works around it. Metal dome tweeters ring like crazy. If it's above the audible range and the system doesn't drive energy into that mode, it works. The number of successful speakers on the market with metal domes seems to indicate that.
Last edited:
Unfortunately "How to build a spherical speaker?" somehow became a few pages on how to build and 18 pages of arm chair discussion of "what's wrong with spherical speakers". So to spice things up, here's an example of how to build a spherical speaker. I believe that Dave of Planet10 mentioned long ago the icosahedron. How about icosahedron segments of a spherical shell with a driver in each segment. These are nice as the segments are identical equilateral triangles. That makes for twenty drivers to fully populate the sphere. I made a drawing and printed two segments designed to squeeze twenty Aurasound 1" drivers into a small sphere. Please find attached my poorly written openScad code for the drawing. I want to make the sphere as small as possible to raise the high frequency roll off corner frequency associated with mounting a bunch of drivers all over a sphere that depends on it's diameter. There are several unsolved problem with this, like, how do you assemble such a thing or how do you take it apart to change a driver that got poked by a finger. Feel free to modify and share the code again here. Maybe the folks that are not actively designing and building spheres can go start their own thread: "All the things wrong with spherical speakers". 😉
That's 3D printed? Nice.
Well.... the Physics are there, so we don't need to build a speaker to know how it will sound ( 3... 2... 1... ) (*)
We can model it nicely and based on the current designs we can likely do so quite well.
I suppose that so long as you apply a high pass filter to get rid of most of the bass you'll get away with a nice ominidirectional speakers.
Now here's a though. If you run the speaker say from 160 Hz and on up... can you get away without a closed cabinet? How about creating vestigial baffles... say a 2 inch ring, around the driver. cover the backside of the drivers and then assemble them WITHOUT a cabinet in a spherical arrangement? Use small drivers, something like 3".
(*) Mind you, the only speaker I've ever built was a Chili Can Speaker when I worked as a night order cook while in high school. I took two of them gallon sized chili cans... cut out both ends. Put a wooden cap ( baffle ) on one side with a Pioneer coax 6" driver. Then stuffed the inside with.. stuff, you know.
I tuned it by adjusting the stuff. It came out sounding quite good in my old Vega GT.
Oh, I did build a couple of Speakerlab kits once...
PS: Free Ballard!
Well.... the Physics are there, so we don't need to build a speaker to know how it will sound ( 3... 2... 1... ) (*)
We can model it nicely and based on the current designs we can likely do so quite well.
I suppose that so long as you apply a high pass filter to get rid of most of the bass you'll get away with a nice ominidirectional speakers.
Now here's a though. If you run the speaker say from 160 Hz and on up... can you get away without a closed cabinet? How about creating vestigial baffles... say a 2 inch ring, around the driver. cover the backside of the drivers and then assemble them WITHOUT a cabinet in a spherical arrangement? Use small drivers, something like 3".
(*) Mind you, the only speaker I've ever built was a Chili Can Speaker when I worked as a night order cook while in high school. I took two of them gallon sized chili cans... cut out both ends. Put a wooden cap ( baffle ) on one side with a Pioneer coax 6" driver. Then stuffed the inside with.. stuff, you know.
I tuned it by adjusting the stuff. It came out sounding quite good in my old Vega GT.
Oh, I did build a couple of Speakerlab kits once...
PS: Free Ballard!
Last edited:
There is no need to damp out the bass in an enclosure, that would be throwing the baby out with the bathwater.
Yes, 3D printed. Print 20 of those triangles and you have the entire sphere. I will attach the .stl file for those that don't want to run OpenSCAD. The sphere might look good with a 3 mm gap between the pieces filled with black silicon holding it together.
Yes, Physics are there, so we don't NEED to build any speakers ever really to know how they will sound.
How these will sound will largely depend on what signals are sent to each of the 20 drivers. I could go with between four and eight channels of amplification and a DSP to do the filtering and delays, so I can independently drive rings of drivers, and vary the radiation pattern depending on the delays. I should be able to make a cardioid pattern, omni pattern or a dipole at a minimum. It will be fun to swap between them using a remote control for the miniDSP.
Yes there is still the range below 500 Hz or so, below where the Aurasound Cougars can play, that must be dealt with. Maybe some woofers on the faces of a cube. Maybe a single large long throw woofer on the top surface of a half cube enclosure on the floor facing upwards.
I have also gone many miles in a Vega, I've got a pair of Speakerlab Super 7s behind me in this room, and the only thing I could afford to buy from Ballard Computer was that mouse pad! Ha. Fortunately I don't live in Ballard. Save the Lutefisk!
This is incorrect. By placing the excitation source (monopole) in the middle of the sphere, you suppress many of the modes whose nodes are located in the center of the sphere . For effective excitation of spherical modes, it is necessary to place the source on the wall (in antinodes).
I made a comparison of source in the middle vs sources spaced around the edge. The results are the same.
https://www.diyaudio.com/community/threads/how-to-build-a-spherical-speaker.374278/post-7048127
https://www.diyaudio.com/community/threads/how-to-build-a-spherical-speaker.374278/post-7048127
AllenB: That is a great observation. It would seem pretty simple to avoid exciting modes like that with any internal reflective baffles or even simple stuffing with fiberglass batting to just absorb the back wave from the drivers. Really exactly the same as in any box speaker design. It would be great if you could share what kind of spherical speaker you are designing or building on this thread titled "How to build a spherical speakers". Unfortunately "How to build a spherical speaker?" somehow became a few pages on how to build and 18 pages of arm chair quarterback discussion of "what's wrong with spherical speakers". Maybe the folks that are not actively designing and building spheres can go start their own thread: "All the things wrong with spherical speakers".
I don't know whether that was a polite disinvitation, you see I have built spherical speakers, and these are the same questions I asked myself, calculations I went through and observations I made at the time.
There are two interesting sides to a spherical enclosure, the inside and the outside.
There are two interesting sides to a spherical enclosure, the inside and the outside.
I'm not sure what you want to hear 🙂. I think that you will figure out how to build a spherical box without my help, especialy if you understand some theoretical basics. Nevertheless, I don't build spherical boxes because the spherical shape is not very pleasing to the eye (at least for me).
I was not too lazy to spend half an hour yesterday to simulate a spherical box SPL in a fixed microphone point, excited by a point source in different places (in the center and on the wall). As the theory predicts, certain modes are supressed when the point source is placed in the node (this statement is true in general for all boxes, not only for spherical).
For those who want to play with placement of the microphone and the point source in 1m sphere, i prepared Akabak3 project file, you can run the project in Akabak3, which is free to download. Akabak3 automatically draws SPL graphs, you just need to download and install VACS viewer.