Compliant tube based headphone pad idea I had while riding a bicycle two days ago. I got the thickness and dimensions dialed for printing and bending, but I either need to setup my old KP3 kingroon with a longer 2040 Z extrusion or print this in 2 pieces. Either way, the joint connection needs more than just the overlap and glue. TPE would probably be better too, although I have no idea what shore hardness this $10 clearance spool of TPU has. The sound quality seems a little tinny and I have no way to tell how loud it is externally, but it is just my first iteration that I can put around my ear and test. TPU is so slow to print and the moisture levels impact the qualities drastically. I actually like the texture and properties of wet TPU more than dry, but it is hard to get it just right. With the design's compliant bend, consistency is kinda important. Anyways, just another boring project. On the bright side, this seems cooler temperature wise when the TPU pad is against my ear.
I spent all day chasing custom logarithmic infill patterns that might incorporate a compliant bend but only learned about how not to do a thing like that in CAD.
I was thinking about doing this purely with a slicer and infill density. If it needs a solid layer or two for some reason you could leave top/bottom layers as non-zero.
The problem is that the infill layers are not well fused and the lack of alignment means they will only cross at angles. This post design can be made solid and turned into cubic with no anchor. That might work with a softer material, but there are still overhangs and the infill pattern is likely to create non linear twist to the bending. At least on my headphones, the tightest part of the bend needs to obfuscate around 60% of the vertical distance on the other side. In other (poor) words, for ever 10mm of vertical height, 6mm is folded out of the way. That is a lot of bulk to push out of the way. Even in this instance I posted, the back side has sections with thinner walls in some areas to make the flex work in such a tight bend without buckling.
Oh, I see where you're coming from - you want to print a straight line than you can bend. I was thinking to completely 3D print the pad and remove/replace the stock units. This would let me print them as an oval.
I thought about doing it like this for a long time but never tried it because I think it has several issues. The horizontal layer deposition lines are aesthetically ugly IMO.
Then there is the issue of how you are going to create compliance. If you are going to rely on some super soft filament, I think it kinda defeats the point. Replacement pads are much cheaper than buying some specialty filament.
By printing and bending a tube, it becomes possible to design for both bending into a loop and for the properties of a soft pad.
Lastly, the majority of pads require a sleeve like retention ring that barely slips into a groove around the plastic enclosure body of each side of the headphones. There is a open pocket sewn into the back side of each headphone pad that is a stretchy layer of vinyl used to slip into the groove. It is possible to replace the plate that is used to form this slip ring retainer groove, but then you'll have exposed screws.
I'm not looking to replace any parts of the headphones, so I need a way to retain the pad using this existing groove. In the pic for the post, one of the test prints is oriented to show the way I incorporated the retaining groove into the design.
Of course, not all headphones are designed like this with the same pads. However, these style pads are used on most low and mid tier headphones because they are all contract manufactured in the same place with only minor variations and where these semi universal type pads are a major cost cutting factor. So designing for this type of pad is designing for the most common style of headphones. One might argue that these are the cheapest pads to replace, and they are. But, knowledge about how modern contract manufacturing works is rather rare, and no one is advertising that their products are the same as everyone else with just a different sticker and color applied or a single variation of molding dies added to create a slight variation in appearance. These pads can be found for $10-$15, but you have to know they are universal and be willing to gamble a bit by buying from whatever middleman has too much stock of these or dies not see them as a profitable thing to market at a markup.
I appreciate the detailed reply! You've certainly spent more time thinking about this than me.
My train of thought so far has been, "I wonder if I could partially notch my ear pads to fit my glasses better" -> "I could probably print something out of TPU" -> "I've seen gyroid only prints with no walls, varying the infill density could be a halfway decent method for messing with how squishy the print will be and without walls air shouldn't be trapped"
On my headphones, the pads snap into the headphones:
My stock pads are starting to fall apart and I have a pair of replacements on the way, so I am considering disassembling them for their rings and clips and gluing the print to that.
And you're right! While I was looking for replacements, I discovered that the stock units are functionally compatible with a bunch of other units although the finish materials are different.
Cool! I love that you are engaged on my level. Today I had a new idea. I thought of the pop-tube kid's toys randomly.
I was combining that with an idea I had yesterday. Yesterday, I properly measured my ear after I glued up a print and actually tested it by listening to music for a few hours.
So first off, my empirical hypothesis is that the sealing properties and the air volume are the primary factors that determine the perception of frequency response. The design pictured in this post adds a little bit of volume overall compared to the original. It doesn't have quite the same bass response but it adds a lot of crisp clarity in the ~200Hz+ range. I think this is just due to the spacial volume.
After measuring my ear and looking at the CAD and print, my first prototype adds enough fore to aft clearance around my ear. It added around 3mm of extra depth. This clears my ear depth by about 1.7mm too far and is primarily from designing in a stiffer material than the original pad. The original pad touches my ear in several places which gets hot and annoying, especially in the summer.
So I started thinking about how I can alter the print to shape it and completely clear all of my ear. The printed pad is already cooler, but adding full clearance could make it even more comfortable. I was perplexed about how to accomplish this though because it would likely require me to replace the base plate if I am going to shape the print further. My present design is just a 9mm single instance of the tube shape with the pattern repeated and a little underlap sleeve added at the end. What I really need is to vary the spacing of each conforming section to control where and how each bend happens. This would likely make the unsolved clasping connector issue worse.
The pop-tube idea might solve my problem though. I don't need to think about the bend joint like a spring. I need to think of it like a bistable switch and design the bends to snap into shape. I'm still mentally sorting out the idea before trying to design it. I'm essentially decoupling the bending from the shape itself. The challenge is how to do this in a continuous print without gaps in a vase-mode like mindset. I'm adamant on the vase-mode approach because I think I can better tune the pad conforming behavior based solely on single wall extrusion properties. Also, TPU is always more ugly for me if I allow z-hops and travel.
Anyways, if I introduce this disconnected level of complexity to my next iteration, I can likely also add something like a recess for glasses too. I have the same issue with my reading glasses and just use ear buds instead when I need them.
I also want to thin all of the walls of the tube and use a mathematical spreadsheet based pattern to stiffen some sections, but that is a secondary objective. My next step is to make a bistable bending action. I'll see if I can make it tunable for a 4 corner topology so that it can work for oval and rectangular designs – not that you should wait or anything like that. I'm fundamentally unstable and unreliable due to my physical disability. Like yesterday was my big cooking day for 2 weeks of food and I'm mostly recovering so far today. I don't know if my back will settle down enough for me to spend competent time designing today, but maybe after lunch and Adderall I'll get an hour or two to mess around if I lay on a heating pad.
I share your curiosity, but I don't have a ton of time to dig into this right now beyond the thought experiment. That's the reason for my slower responses :( Work is busy and the kids eat up most of free time.
You're right - the seal will directly impact bass. This is why the sound on some headphones will change fairly dramatically as you move your head around - you're breaking the seal. For me, the head position most likely to break the seal is turning my neck fully in one direction and looking up, but it can also happen with less extreme head motions depending on the cans. I could see volume also playing a role, since the air volume inside the pad is effectively a resonator and changes in air volume will impact how it resonates. I suspect the material of the cup itself will also play a role. Something dense/reflective, like leather, will likely sound somewhat different than say a suede or a microfiber. That was one reason why I was considering gyroid - it would be reasonably non-reflective.
Sounds like a similar motivator to my "I wish these didn't press on my glasses frames so hard" ;)
A pop-tube seems like it would be hard to print vertically oriented. I suspect it would move around some as you're printing thanks to not being very rigid. It wouldn't hurt to try it. Printing it sliced down the center and laying across the bed horizontally seems like it would be easier. I certainly hear you on the joys of TPU stringing, but if it's limited to the far ends of the print it shouldn't be too horrible to clean up. You could even design it a touch too long and cut the ends off.
Depending on the spacing of the tube crinkles, you might be able to line them up so your frames fit between them. You could also probably make one crinkle stick out a little less and line that up with your frames.
At this point, I have nothing but time. I'm also trying out a pair of 'real' ANC headphones, vs my office drone headset that happens to have defeatable ANC. They have ridiculously sized pads and they're actually pretty comfortable with glasses. I am somewhat tempted to type out a mini-review somewhere here, but have no idea where I would post it.