Rotary Subwoofer inside Handheld Bluetooth Speaker (Will it work?)
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- Опубліковано 8 вер 2024
- Join me as I dive into the adventure of miniaturizing a rotary subwoofer! Discover if a three inch miniature rotary subwoofer will work inside of a handheld Bluetooth speaker as this has never been done before!
Songs used:
Sharp - ISOxo
Run Free - Spirit Stallion
Check out the awesome background music by DJ Double X at:
@djdoublex1559
Nice idea in theory, unfortunately smaller volumes require higher static pressure from the "fan" to be effective, this is because the rotary subwoofer has to do a lot more compression. Awesome stuff nonetheless though!
I indeed know nothing about this. But I was wondering about forced induction or some sort of sound reflective material to help maximize the lack of space 🙃 also was wondering about fan design. Maybe take a que from more static pressure pc fans (radiator fans for pc water cooling) fans can be optimized for straight up airflow or air pressure.
@@copelandtaylor8851 There are quite a few things to consider. The first I'd consider is getting as close of a fit between the housing and the blade tips as possible.
Then there are also the following:
More blades (also offers smoother modulation (better fidelity if you want to try and move above 20Hz)
Minimise obstructions in the immediate path of the air since these introduce turbulence. (E.g. minimise surface area of movement mechanism and motor/voice coil/suspension).
Maybe design the blades to have a symmetrical airfoil, where the leading edge (part of the blade cutting into the air) is nicely rounded over) and the trailing edge (the opposite end of leading edge) is nice and sharp.
You still need enough air volume to not stall the air flow through the fan.
I'm not so sure typical methods of trying to absorb the rear wave would be appropriate due to how long the wavelengths are, you'd need some VERY deep in thickness absorbing material for it to be anywhere near effective. Feel free to try it out anyways though. Hope this helped
All things being equal, the rotary sub outperforms the conventional cone sub as he clearly showed in the video. So it definitely CAN work. This needs to be mass produced. Rotary subs just need a separate chamber to hide the mechanical noise produced y the fan.
Wider blades?
@@blknightsixtyfo greater arc length. Not sure quite how else to explain it. Sorry
Smaller blades at a higher RPM might resist vibration distortions. Also the port is very restrictive. Been thinking of building rotary subs for years and trying to figure out a better way to interface the voice coil to the blades but have never got around to it. Subscribed!
Thanks for subscribing! I'm making a new video on building a very simple and efficient rotary sub where I'll supply the stl files for the 3d print parts so this should help you build one
Making higher speed propellers would require a much more powerful amp to change the pitch of the blades as well ,BTW the fan noise itself would introduce more problems , I'll be looking forward to see more experiments though .
i feel like diy/building the driver might provide more opportunity for modification and have you though about using rc helicopter parts? they have stuff thats meant to deliver power and take high stress with minimal vibration transfer
@@avragegamer8864 I used rc car linkages on my 16" version
@@nathanbulle5782 nice! i was also wondering about spacial tolerance...is there any shot the rattle is from the blades rubbing anywhere?
I've been building loudspeakers since the 80's, but never considered a spinning sub before and I think it's a great idea. A couple of thoughts (hopefully helpful ones!) Instead of a closed box. What about using the air behind the rotor by redirecting it to the front of the cabinet. Kind of a horn/ bass reflex hybrid that allows free air movement in front and behind the rotor. You might have to play with tuning a bit. I like the idea of a 3d printed cabinet. Adding dampening material, such as the asphalt material used to damp the noise in a car would help in vibration. Lastly, make the rotor as absolutely light and stiff as you possibly can. Of the two, stiffness is the more important. Everything that supports the rotor and motor should be as sound dead as possible. Be sure that no two parts meet that have the same natural frequency. Running the rotor with a belt rather than direct drive would be interesting, but probably a nightmare to package. I hope that I'm not just being Admiral Obvious here. I honestly love this idea. It may never be practical, but hey, I built a set of plasma tweeters with vents to the outside and ran them for months. So who cares about practical.
You can actually find a lot of info about it on the internet under "Rotatory Subwoofer", if I'm not wrong, this concept held the most powerful subwoofer in the Guinness World Records
You absolute beast! When I was 12 I went to a HiFi convention in a hotel, and one manufacturer was demoing their plasma tweeters. They were asking $25,000 for the pair, and this was 1980. Came with a tank of Argon? I can’t remember what gas was being used. I just remember freaking tf out at it.
@@mikabreto Thanks. The problem with plasma tweeters is that they produce a lot of ozone, if you use the atmosphere to produce the arc. Which is extremely unhealthy, to deadly in enclosed spaces. I circumvented this with a dryer exhaust hose and a fan and having the system suck air across the tweeters and vent it outside. Using another noble gas, such as argon or helium would prevent that, but presents its own costs and challenges to use.
If you could watch your sub in action with a high speed camera it might help answer some of your rattling issues. I agree with the person above that rigidity is your primary concern to get rid of the rattling.
Please try it again. Try to use flexture joints to reduce ratteling and to simplify assembling.
Make blades fill surface of the speaker completely.
To increase pressure you can use two cotrary rotating motors. Control signals should be synchronised, but phase should be tweaked, so they work in resonance..
It can be really interesting.
If the fan is spinning clockwise like I think it is, then any little shove to the blade angle off center will result in the blades being slapped to their excursion limit. Basically, the pushing motor needs to RESIST the airflow effecting the blade angle. (Try running the motor CCW)
Agreed
To fix the rattle you might look at RC car suspension parts. I believe they make tiny ball joints and linkages.
Very cool project!
Good point
They do
That’s actually a fantastic idea. Brushless motor and variable pitch prop devices for RC aircraft could be a great starting point too. Modified blades would probably work. Blade Balance is key though.
For a small size like this I think putting bearings on each blade to allow the pitch variation is a mistake. I think you'd get a much cleaner actuation and sound by using a compliant structure, a blade that just flexes back and forth instead of tilting.
Actually that may be a good idea even for a large blade fan.
I think ideas like this (if perfected) could definitely make rotary subwoofers more popular
You should put the other drivers in two enclosed chambers to eliminate phase issues.
Really interesting. I was watching videos on rotary subs several years ago and there were only a few on UA-cam. Recently there seems to be a lot more people like yourself researching, building and experimenting. Eliminating rattle is important, it will be fascinating to see new techniques and different materials used in future.
5:27 You have effectively simulated the sound of every jackass that drives by with a subwoofer in his car good job!
Nathan, that was certainly worth a shot! Getting real bass out of a really small package has always been a challenge!
Thanks for the video!
you really did great job making and testing rotary sub in actual use case scenario
I appreciate your hardwork
super cool to see someone make a tiny rotary sub for a bluetooth speaker :D
You did a great job making everything and explaining everything
it will reduce distortion if you can make it a rubber busing instead of a bearing. Also, the paper clip rod must be tight. then check the xmax of the sub to make sure it wasn't bottoming out. iknow it would be difficult for the motor to work if is tight but it will sound good.
This NEEDS to be made and produced
Excellent lesson. shows how rotary subwoofers' best application might certainly be in large scale low frequency reproduction of such displacement that with piston style drivers would not otherwise be practical.
This was sick, some further experimentation would definitely bring something more effective
What if you made the enclosure tube shaped, similar in design as the JBL Bluetooth speakers? Might have a different low frequency response. If you do design one like that I’d be interested in the outcome.
Loved that you played the music from Spirit: Stallion of the Cimarron! Great movie and great soundtrack.
"And a couple of other parts."
* Shows way more than the 2. Haha, nice exaggeration!
Might have to tune the port a bit for best accoustics. You want some restriction to generate a pressure differential, but you need it open enough that it doesn't overwhelm the fan and cause it to stall.
Sure, the fan thing shook the box more, but the sound quality wasn't nearly as clean. So there's that to consider too. It would definitely have to be tightened and/or otherwise cleaned up before it could be actually viable. Interesting idea, though!
Sounds like the blades hitting the frame but this will never work in a small enclosure anyway because the fan noise is louder than the bass the cab can push and the way the fans vibrate so loosely, with the different back and front pressures cancels most of it out.
It's like cutting the foam around the speaker and expecting it not to fart.
@@alfsmith4936: Yep, sounds about right, heheheh!
Creative idea! It sounds like the fan blades are hitting the shroud.
I love that you took the time and tried it out. Was really curious my self if this in practice could work.
Thanks for the test ! much liked to see what it gives.
What I really wanna know is would it be possible to make something like this using a turbine design instead of fans to have more pressure. Or maybe replace the blades entirely with an ionic thruster. I know Integza has been working on and made some neat designs for one, but if it were optimized to put out a lot of air, it might be a good idea to get rid of the fan noise and still be able to move air. Then again with all that being said, perhaps the sound of electricity zapping air would still defeat the purpose, but maybe it would help remove some mechanical components so less chance of mechanical failure. But I also am not sure if it would even move enough air to be worth the idea.
I hope you try this again as well.
I'm slowly gathering parts to try to turn a desktop computer fan into a small rotary sub and a couple of small speakers to my electric wheelchair for some rolling music.
The way that I planned to mount it was similar to your box, but I was going to have a short pipe going through the middle of the box to leave the rotary open while providing backpressure for the cone speakers on either side.
Getting to see this and a couple of your other builds has really helped me to work out what I need. Thank you.
I'm really glad I could help. My ultimate goal is for anyone who is interested to be able to own a rotary sub (whether they build it or buy it cheaply from me)
I need a rotary subwoofer in my life. You've been my introduction to this idea. Thank you.
Room for improvements. I see it has potential.
I'm excited to see someone working on rotary subwoofers.
Incredible idea, i wonder if there exist a box configuration that would mimic an infinite baffle enough to be viable for this project? You are doing pioneering work sir. Thank you for all of your great videos.
Very cool idea for miniaturizing this and getting the blades to pitch. Have you thought about implementing a small 100-size collective pitch rc helicopter swashplate and blade setup? Might be a little more accurate and easy to move.
And less rattely lol
@@nathanbulle5782 😆
I love the idea!
I'm guessing more mass in the box itself and maybe a different motor might help reduce the rattling and other noise. Oh, and maybe some kind of flywheel ring around the rotary sub for stabilization
I like the fact that you did this it was a great experiment and I learned more about rotary subs in you doing so. Seems that they require a much larger area of air movement...thank you foe the video! 👍👍
Use a HHD motor and smaller blades or a larger casing don't forget silicone is your friend 😁
Wider blades will control the air better. Narrow blades will allow air slippage. Have them nearly touch.
New to the subject and you guys are blowing my mind🤯
U turned me on to something new ,thanks dude
That was honestly realy dope
Hey man great work! Would love to see a version 2 with all the things you learned on the way :)
That was a dope idea to try. Keep it up and don’t give up
Cool idea. I think you would need machined parts and better airflow for this little one. I saw the double rotary you put in your laundry room window. You’re a badass man!
Nice work, but it needs a larger air vent and stiffer construction.
The thin walls will flex too much.
Give it another shot.
Nice 👍 you got some real creative engineering talent
This is worth experimenting. Their has to be a efficiency range to doscover.
The rattling can be fixed, this concept idea should not be given up on. If there is a way, someone will make it possible.
Rotary Subwoofer might have another good purpose as well, I wonder if it could keep open air flow in a open warehouse were there is no air conditioning?
Very cool project. Great work.
Think maybe the fan is turning too many RPM's ? Might take care of some of the rattle.
The noise from the fan itself is worst than the rattling. Try adding a pot to control speed and mix and match with different sized fan blades (as recommended as well)
this is so genius bruh
Awesome video, regardless of whether or not the rotary sub sounded better this project was a total success!
Interesting! This is a great experiment. I wonder how you might be able to simulate an infinite baffle in a portable configuration.
Might need a small, wood or metal fan, brilliant idea
Bigger box
all you need is a good crossover to get rid of anything over 50hz. most people use them for 0hz-20hz and let other real woofers do the work as the fan blades are better for infra-sonics. these do not handle anything above 300hz at high gain/volume, and that is with the official ones that are like 12". you can barely turn them up if you have no crossover, as it makes the blades distort too much. also they require a sealed compression chamber, not a port. One last thing is that rotary subs are super efficient and if you have them hooked up to the same wattage as the other sub there is a good chance it was getting too much power.
I just started the vid, havent seen if you addressed this yet. good luck!
It might be worth putting some sort of frequency splitter in there so the rotary sub is only handling frequencies below 20hz? It would probably sound dope with the native subwoofer and the addition of the rotary subwoofer!
The rotary sub is capable of 1 to 50 hz so I would use a splitter for 50 and down. Running the sub with straight audio generates more heat but doesn't destort
@@nathanbulle5782 okay here's my grand idea, what's about a similar pillar style you got there, but use 1 tweeter, 1 midrange driver, a woofer, (not subwoofer) and the rotary sub?
Idk what kind of amp you would need to run that, but with a bandpass filter on the woofer+midrange driver accompanied with a LPF for the rotary sub and a HPF for the tweeters?
I've only dabbled with car audio, but I've always dreamt of making my own all in one box like that.
Transmission line is the way to go.
This makes me wanna diy my own rotary
Yeah same, and I'm on the edge between to buy or not to buy
THATS SICK!!! It doesn't sound as good but my friend Trenton and I think it's a really cool thing you did. Even thoug the sound is that good. keep going dude this is awesome
I was thinking that . When I saw you video. Keep up the great work 👍
Awesome idea. Keep it up.
I would try a fan with 3 larger + deeper blades, rather than 5 small shallow blades, in addition to having a pass through pipe design, where you just put some metal screen material on the opened ends. I once bought these used Industrial fans, that were like 1" deep, with 3 blades. I believe their original use, was for the giant, original, HP Laserjet printers. They were VERY powerful, and very loud.. and created near hurricane level winds. I had put two of them in front of a cut up PC case... and it was pretty much overkill. I probably didnt even need my CPU cooling fans... because the amount of air those 2 industrial fans created... was astounding. But as said.. it came with a cost. The things were incredibly loud.. and being that they were AC... I couldnt control the speed (I never tried an in-line adjuster.. just wired them direct to the power cord) I believe those fans were 4" x 4" with a total of 1.5" depth. I have no idea what the RPM was.. but if memory serves correct... I think I was able to chop carrots with them.
As for the blades themselves... take account for plastic stretching out, from rotational forces. You might have to increase the gap between the blades and the surround.. as well as add a bit more thickness and rigidity to the blades. Of course, certain plastics are less effected by rotational forces.. which is why those brown colored PC fans are able to preform much better than others (noctooah?). Because their plastic does not deform.. then can use less clearance between the blades and the housing.
I will add... that sometimes with too many blades.. you end up creating turbulence, that causes some backwards moving air. As such, sometime less blades, can actually more more air.. more efficiently.
The problem for this mini sub is the tiny back enclosure, because if the little fan is successful at even generating 1 psi of pressure in the cabinet… Where is that pressure going to go but through the gaps in the blades of the fan, thereby neutralizing any pressure the blades pushed out or in.
that’s why this works when it’s in a window because of very little blow-by or spillover pressure from either inside or outside.
The smaller cabinet has to be pressure dissipative on the back side-down to the frequencies desired to be played, and timed to the enormously long wavelengths below 50hz. (100ft plus)
It’s as though this design concept needs an indoor and outdoor separation just as hvac needs to discharge the heat to cool inside, and the two can’t share the same space…
But people will still try to air condition their garage with a window a/c and no separator panel or wall.
(Have seen it myself)
But this is also this concepts limitation as to how loud it can create any sineuaoidal bass tones with any purity and intensity based on the action the pressure on the front or back of the fan blades it creates…makes a huge motivating force on the air to want to pass right back through the fan instead of out into the room with the listeners.
A small idea to get tid of fan noise is to put the entire assembly into a box and install a passive radiator in front of the fan. Idk whether it will work.
It would work but the passive radiator would need to be very large (15 inches at least)
It would be interesting, how the fan speed affects the sound, less fan noise would be ideal.
That rattle from loose fittings... well, you kinda can hear the bass. 🤭
It's still a neat consept, just keep working on it.
Great idea. Keep refining it. I've only seen one rotary sub on the market (Eminent Technology TRW 17) for home hifi/theater use and I heard it costs about 25 grand installed. ...Ouch!
Interesting, I just learned rotary subs exist. Thank you for the info
Could lubing the moving parts with a grease stop some of that rattling. It's not ideal considering it would grab the dust though
This is becoming an incredible channel mate. Keep it up 🙏
Keep it up! Your engineering skills are impressive. How many job offers have your had since your original post two weeks ago?
To add to my other comment, I think it’s a,axing you are doing this. I hope you keep it up because experimentation is the path to innovation. Also, if you can turn down gain and control the deflections of the blades better it could help reduce noise and allow small enclosures (relatively speaking)
Very cool experiment. Rotary subs are so neat.
General rule of thumb. If you scale down a design you need tighter tolerances to an equal scale.
Hey man GREAT JOB. Keep up the good work
Haha test about subwoofer and suddenly hearing Run Free from Hans Zimmer. What a plot twist😂
This is awesome but i had an idea could you just have the back open for an outdoor speaker?
Flip the rotary sub 180°. Basically inside out. Fan on the inside of the box and cd rom motor outside the box.
Of course you're having rattling issues. That thing is creating lots of pressure. Every action has an equal and opposite reaction. That pressure is bending the thin blades. You're gonna need something a lot stiffer than PLA. Preferably you'd be supporting those blades on the outer edge as well as the inner edge.
alls i can think is like a engine or something with an imbalance could try some bushings and rubber spacers should deaden the vibrations in theory and maybe try a different blade design also maybe more air passages
Isobaric loading could help with space. And maybe play with blade shapes. How rattly are you largest ones?
Your box sound verry good with conventional speaker ,,.
Some thoughts - similar to other comments already but some things that might have helped (maybe): Stiffer material for the rotors, soft padding inside the enclosure, larger port and larger enclosure (yeah, I know, starts defeating the idea a bit). I don't know if doing those things would help or not really. Actually, reading the other comments, I think they might have a point about spinning the blades faster and maybe having more of them.
A bigger enclosure is the key to rotary subs. The closer one can get to an infinite baffle the better.
@@nathanbulle5782 Cheers
I appreciate the hard work you put in this project but in my own opinion rotary is not the way to go for a smaller speaker system because rotary needs a big space to make the back and forth alternating air pressure, for example a closed room or a car boot etc. In order to make big bass from a small speaker, what you need to work on is some system in which a small speaker is made in such a way that when it is placed/stuck on a surface, it utilises that surface to make bass by sending vibrations down to it. In fact, I've seen this kind of a small portable speaker in a video that is bass-less when hand held but makes a massive bass as soon as it is placed on a hollow and hard surface. Probe into this theory and maybe you get better results.
@@Gr8Passion4Music this is what I did before rotary subs
i really liked this video, thnak you
That rattle noise would drive me nuts. It sounds like a blown speaker. Have you tried a combination of both subs?
fan speed has a direct impact on output. Faster blades will push more air at the same blade angle. Try doing this with a more powerful motor and stiffer blades. Maybe try using a carbon fiber PLA or PETG to print the blades (stiffest filament without getting super pricey). Finally, drop the box. Make the enclosure a pill form like the beats, center the sub to pull air in one end and out the other. Rotary subs in a ported box are a no go.
Good idea
cool idea
I would love to see a rotary inside a vehicle. Doesn't have to be big, something like a 4-6 inch. Get or borrow a SPL meter to see how many db's it makes
great job on the video.
Keep up the great work!
Wonder what would happen if you added a length of tube in front of / around the rotary sub, sort of turning it into a ducted fan
Maybr try an extenal rotory sub using a blutooth sub as a base if its possible
That way it can use the open baffle air
i think u have to change the concept, u use a fan to pump in a modulate airflow, try to use 2 membrane valve and use a standard speaker or a pump with magnetic piston i think u have a low noise and the piston vibration help u in propagation of bass tone, remember to fix the speakers to the surface (the bass tone was propagated well on surface not in air)
have you thought of trying to make a centrifugal style rotary sub?
Looks interesting
Was that song from that horse movie Spirit? I’m feeling 90% sure it was and boy that takes me back… I’m old!
i certainly enjoyed this video! a portable speaker with a rotary sub is indeed a good concept but it doesnt work that well in reality as you mentioned due to it not having an infinite baffle. my next suggestion is a rotary sub with a small footprint that can be put basically anywhere, with the form factor of a conventional sub, around 8 inches of cone area (more like blade area haha)
That was what I did in my first video. The dual rotary subs are 9 inches in diameter and one of them can be put anywhere
oh, i wasnt aware, i though they were 12" in diameter @@nathanbulle5782
Does these dual rotaries work well at outdoor applications?Have you tried any of them at outside and if not what is your predictions about outdoor usage?@@nathanbulle5782
I was just wondering if there aren't any pitch varying mechanisms in the RC plane world that you could use.. Anyways, nice video, I've seen a whole bunch of your rotary sub videos now.
Cool! I suggest to test real low frequency response try pipe organ music fur some subsonic pedal notes.
Now your speaking my language!
Or cellos as well
Hey, you could make it a portable window insert for demos.