Hi All,
Although cylinders are known to have standing wave issues, I am contemplating such an enclosure for a sealed sub. The cylinder's length (on axis with the drive unit) calculates to less than 1/10th of a wavelength at crossover. Any problems here?
Cheers, Carl.
Although cylinders are known to have standing wave issues, I am contemplating such an enclosure for a sealed sub. The cylinder's length (on axis with the drive unit) calculates to less than 1/10th of a wavelength at crossover. Any problems here?
Cheers, Carl.
Hi,
I'm pretty sure that's not nearly enough info to know if there would be a problem. That's only as far as my knowledge stretches, however.
I have contemplated building a 'sonosub' before. A sonosub is built with a cylindrical piece of damn-strong cardboard.
I'm pretty sure that's not nearly enough info to know if there would be a problem. That's only as far as my knowledge stretches, however.
I have contemplated building a 'sonosub' before. A sonosub is built with a cylindrical piece of damn-strong cardboard.
Rule of thumb - if the length is less than 1/6 wave, it acts like a compliance. Longer and it starts looking like a pipe.
I tried modeling several speakers to various size tubes, none of them looked good.
Guess that is why we never see them
Guess that is why we never see them
What are the problems, and at what frequency and diameter-to-length ratio do problems occur?
Cheers, Carl.
Interesting !
So, for a 22 inch length, and a diameter of 24 inches, It would be just fine
for a 100Hz and down sub woofer 5.75 cubic feet.
I'm also thing a rule of thumb is to keep the length and diameter dimensions similar in size, but I can not say where/if I read that somewhere, or, if it is simply my own conclusion.
You can model this in horn response.
Here is a closed speaker in a 10 foot long pipe. the lighter spiky response is with the wave equation (tube impedance) factored in. Both sims have no damping material.
First resonance is ~56Hz
That is 1132/(2*10)=56.6Hz - so F=1132/(2*L)
You can see the two curves are not different below roughly half that frequency. F=1132/(4*L)
If you go by the rule of thumb I gave previously: your crossover frequency should be less than F=1132/(6*L) - so if your pipe is 18" long F should be less than 1132/9=125Hz
Make sense?
Attachments
Thanks for the replies fellows.
Currently the plan is for a 430mm diameter tube 420mm long - about 60l. I am planning to crossover at 80Hz, so it looks quite safe by calculation and agrees with my intuition. A cylinder is simply so stiff compared with a plane-sided box, not so difficult to make, and requires little or no bracing. I am surprised they are so uncommon. Anybody out there tried it? Successful? Indifferent? A failure?
Cheers, Carl.
Currently the plan is for a 430mm diameter tube 420mm long - about 60l. I am planning to crossover at 80Hz, so it looks quite safe by calculation and agrees with my intuition. A cylinder is simply so stiff compared with a plane-sided box, not so difficult to make, and requires little or no bracing. I am surprised they are so uncommon. Anybody out there tried it? Successful? Indifferent? A failure?
Cheers, Carl.
Hi Borg Audio,
I have used a number of sonotube subwoofers, and like the ease of construction. Reinforce the endplate w/ crossbracing, otherwise no bracing needed. Ron E's rule of thumb sounds fine (maybe a bit conservative), some will say anything below 1/4 wavelength is OK.
I worked through a project comparing sealed, ported and bandpass home subs in 1999 (time flies). Sonically, I found no difference between a well build cube sub or a sonotube sub of the same construction principle. So, it comes down to the home decorator...
As to uncommon: google "sonotube sub images". They are out there. 🙂
Regards,
I have used a number of sonotube subwoofers, and like the ease of construction. Reinforce the endplate w/ crossbracing, otherwise no bracing needed. Ron E's rule of thumb sounds fine (maybe a bit conservative), some will say anything below 1/4 wavelength is OK.
I worked through a project comparing sealed, ported and bandpass home subs in 1999 (time flies). Sonically, I found no difference between a well build cube sub or a sonotube sub of the same construction principle. So, it comes down to the home decorator...
As to uncommon: google "sonotube sub images". They are out there. 🙂
Regards,
Attachments
Hi Oliver,
Thanks for the reply; sadly, sonotubes are like hen's teeth over here so I'll have to roll my own, so to speak!
Cheers, Carl.
Thanks for the reply; sadly, sonotubes are like hen's teeth over here so I'll have to roll my own, so to speak!
Cheers, Carl.
Hi Borg Audio,
How about "Cores and Tubes" industrial tubes? Came up in a quick google search, might be worth a try?
https://www.coresandtubes.co.uk/industrial-tubes.html
Regards,
How about "Cores and Tubes" industrial tubes? Came up in a quick google search, might be worth a try?
https://www.coresandtubes.co.uk/industrial-tubes.html
Regards,
Hi Nrik,
This thread is called "cylindrical sub enclosure". The famous graph you are showing in Post #12 has little to nothing to do with subwoofer enclosures.
Regards,
This thread is called "cylindrical sub enclosure". The famous graph you are showing in Post #12 has little to nothing to do with subwoofer enclosures.
Regards,
Nrik, all these graphs show responses above my cutoff frequency of 80Hz; these responses at higher frequencies are well-known, I believe. I do like the idea of a spherical subwoofer, however!
Cheers, Carl.
Cheers, Carl.
Ron E, thanks for the link, but I feel that 3mm wall thickness might not hack it...
Cheers, Carl.
Cheers, Carl.
tb46; Oliver,
Thanks for the link - I have had a quote from these folks at £186.00 per sub tube... I'll roll my own!
Cheers, Carl.
Thanks for the link - I have had a quote from these folks at £186.00 per sub tube... I'll roll my own!
Cheers, Carl.
Hi Borg Audio,
Post #17: "...I'll roll my own!"
Interesting. Let us know how it goes, pictures of the process would be great.
Regards,
Post #17: "...I'll roll my own!"
Interesting. Let us know how it goes, pictures of the process would be great.
Regards,
Will do, once I work out how to post photos! I've been experimenting with kerf bending in both single and compound curvature using both plywood and MDF bonded with expanding polyurethane adhesive. MDF I find to be easier to work with and cheaper too; I doubt very much if it will be particularly different, acoustically, to plywood in this application.
I have laminated HDF with PVA for scoop bins in the past with fair success, but was never 100% confident that it was free of voids. Expanding PU adhesive is a boon, however the forces it can exert whilst curing are not inconsiderable! I may source some expanding epoxy as used in aerospace sandwich panel bonding and see how that goes.
For little reason other than it seems correct in engineering terms, I am treating the enclosure as a pressure vessel since I have seen no evidence to suggest otherwise that enclosure stiffness is extremely significant in a sub. Resonant panel modes in a cylinder with a domed end will be significantly higher than the driving frequencies involved, and I am reassured by others' comments that pipe modes will be insignificant.
Cheers, Carl.
Borg, wall stiffness dominates when it comes to frequencies =<~150Hz.
Have used tubes for sub builds for >30 years now. When I hear "wall thickness must be >2"" I laugh and promptly correct them. Now if you are using the sub like a woofer eg >150Hz then wall mass must be considered to dampen the panel, but then it's not a "sub".
This is one of the issues faced when using my test MLTL sub as a woofer that is part of a 3 way system. It's wall thickness is only 1/8" cardboard and very light weight.
There must be somewhere to get your hands on an affordable tube, keep looking. One thought that passed my mind are the inner core tubes used on spools of power cables. Think high tension wire used by the electric utilities. Don't know what they do with the spools when done, recycled? Kinda doubt it. Another source of PVC tube is used for water / sewer pipe. In my younger days oogled at these just laying on the side of the roadway. I just can't steal 🙂
We have a PVC fence company just down the road here that got their hands on scrap PVC, piles of it in their yard to be recycled. Friend of mine moved to a new development. I was checking his location on google earth/maps and discovered that their "park" had tons buried between the ponds.
Polyurethane foam can be a real pain if you have no experience with it. The expansion can and will cause some headaches. Which reminds me of some friends building an experimental plane (EAA). The belly shell of the cockpit was attached to the inner shell using polyurethane. This assembly performed out in the driveway.... Oh it expanded alright, when the outer shell started lifting away, weights were added. This seemed to work for the first few minutes, but then the pressure started to build so they added more weight. In their OMG moment both of my friends climbed onto the shell. Again was ok for a couple of minutes. Still not enough... then came the idea of drilling small holes to relieve the pressure. That was all they could muster. It was squirting out everywhere, dog, cat, kids, bushes, yard, house and car all got it good. What a sticky mess! Needless to say my buddy's wife Jeani didn't think too kindly of it all. Asked if she got it on video, umm no, but the end result was quite evident after their "cleanup". Their pets had to be shaved, funny looking things they were!
Yes I LMAO
Bendy ply may work ok, never used it myself. The tension on that outer single layer might be too much, wood must be cut across the grain for maximum strength. My best suggestion would be to use low expansion PU foam or the latex type if you want to go down this road. Allow for expansion and trim off the excess. Personally would use a construction type adhesive in the gaps to eliminate all air gaps, be prepared for alot of excess squeezed out.
Could be made CLD also, Use fiberglass on the interior and or exterior for added strength.
Have used tubes for sub builds for >30 years now. When I hear "wall thickness must be >2"" I laugh and promptly correct them. Now if you are using the sub like a woofer eg >150Hz then wall mass must be considered to dampen the panel, but then it's not a "sub".
This is one of the issues faced when using my test MLTL sub as a woofer that is part of a 3 way system. It's wall thickness is only 1/8" cardboard and very light weight.
There must be somewhere to get your hands on an affordable tube, keep looking. One thought that passed my mind are the inner core tubes used on spools of power cables. Think high tension wire used by the electric utilities. Don't know what they do with the spools when done, recycled? Kinda doubt it. Another source of PVC tube is used for water / sewer pipe. In my younger days oogled at these just laying on the side of the roadway. I just can't steal 🙂
We have a PVC fence company just down the road here that got their hands on scrap PVC, piles of it in their yard to be recycled. Friend of mine moved to a new development. I was checking his location on google earth/maps and discovered that their "park" had tons buried between the ponds.
Polyurethane foam can be a real pain if you have no experience with it. The expansion can and will cause some headaches. Which reminds me of some friends building an experimental plane (EAA). The belly shell of the cockpit was attached to the inner shell using polyurethane. This assembly performed out in the driveway.... Oh it expanded alright, when the outer shell started lifting away, weights were added. This seemed to work for the first few minutes, but then the pressure started to build so they added more weight. In their OMG moment both of my friends climbed onto the shell. Again was ok for a couple of minutes. Still not enough... then came the idea of drilling small holes to relieve the pressure. That was all they could muster. It was squirting out everywhere, dog, cat, kids, bushes, yard, house and car all got it good. What a sticky mess! Needless to say my buddy's wife Jeani didn't think too kindly of it all. Asked if she got it on video, umm no, but the end result was quite evident after their "cleanup". Their pets had to be shaved, funny looking things they were!
Yes I LMAO
Bendy ply may work ok, never used it myself. The tension on that outer single layer might be too much, wood must be cut across the grain for maximum strength. My best suggestion would be to use low expansion PU foam or the latex type if you want to go down this road. Allow for expansion and trim off the excess. Personally would use a construction type adhesive in the gaps to eliminate all air gaps, be prepared for alot of excess squeezed out.
Could be made CLD also, Use fiberglass on the interior and or exterior for added strength.
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