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vasubandu

Vasubandu's Tower of Subwoofer Build

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I hope this is the right place.  Did not see a separate DIY place.

 

I am going to get started on my subwoofer.  By started, I don't mean putting things together, but I will start locating and parts and getting them so that I can be sure that the next parts will work. 

 

The final product should look something like this

 

image.png.1f391ca5b303960679486401de3262c3.png

 

 

A lot of people said to use a sonotube, and I guess that is what most people do with round subs, but it seemed inadequate for a six foot subwoofer with a 115 pound subwoofer at the top.  And after searching to the ends of the earth, I found that that a simple, readily affordable alternative exists and is widely available.  Bent plywood.  It is strong and will not resonate because it not a sold product. It could be made with a full circle or two half rounds that were joined later. I am leaning towards the half rounds  because it would make installation easy and the joint would be covered by veneer anyway. If made with 4 pieces (36 diameter by 36 long), it would cost $400.  That is a lot more than Sonotube, but it is 5/8 inch plywood.

 

After a conversation with Nick at Stereo Integrity, I decided to to use his 24 inch driver.  It seems like a quality product, and if nothing else he expressed more interest in my project than just about anyone else.

 

Now I need to deal with the amplifiers.  They are rated at 2000 watts apiece, and I have no idea how to make that happen. I have not found a plate with that size amp.  And so it goes.  Hoping to finish this by end of April.

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The sonosub idea is a good one. However, you have not mentioned what your needs are. Is this for music or home theater and what sort of low frequency extension are you looking for?

 

In my case, I used 18inch diam sonotube about 6 ft  in length. This gave me a 10 cu ft volume with a hefty port (also sonotube). The half power point on mine is 17 Hz and a 100 watt amp will give a considerable SPL for my room.

 

 The 15 inch driver was less than $175 at Parts Express. It sounds like you have a more generous budget. If I might suggest, consider using those two drivers in separate cabinets. This lets you use room idiosyncrasies to your advantage by distributing them.  Also, if I may, 24 inch drivers are a bit over the top in my opinion. Depending on what your design goals are, 15 inch drivers can do fine and save you a ton of money. Again, multiple subs are always a better idea.

 

In either case, good luck with your project.

-Tom

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Thanks @PrestonTom I really appreciate the comments.  

 

For background, I would call this a proof of concept, which kind of funny because as little as I know, one could say that I should get a clue before I start having concepts. But that whole walk before you run never made sense to me.  

 

Thanks for the thoughts on 24 being too much.  This could be scaled down to 18 or 15, but then I wonder about space.  As I said in my post, Nick at SI was so generous with his time and thoughts, and expressed enough interest in the outcome that I would get whatever it is from him.  Their HST-15 MK II has a 108 Vas, which is 3.8 cubic feet.  For reasons I am too embarrassed to admit, I am doubling Vas for my considerations, so that is 7.6 cubic feet per driver or 15.2 for the system.  An 22 inch interior tube six feet long  would have a volume of 15.8 cubic feet. With components, it would be a bit short,  but  that ought to work.  It also might improve the WAF.  

 

My questions in this are twofold.  First, I want to see if subwoofers can effectively be made bigger by going vertical.  I think that vertical expansion would  be more acceptable to people than horizontal.  Second, I am curious to see if we are choking  our subwoofers.  To give you an idea, the SI HS-24 site says 16-20 cubic feet for a ported enclosure.  16 cubic feet is a box 2.5 feet per side.  Stick two in there and it is 3.1 feet per side.  Nick told me that he did not of any instance where people actually provided it.  I have some idea what the modeling says, but I am not entirely convinced that modeling equals perceived sound quality.  

 

And if this works, I wanted it to be something completely different.  I am not sure that two 15 inch drivers could do that.  But 2 24-inch drivers might if they worked better.  I know that separate boxes would be better, but that would just get me two good subwoofers, not answer my question.

 

It is hard to explain, but I really don't even care that much if this works or not.  I just want to find out.  So design choices are made to answer that question more clearly or decisively rather than by what makes the most sense for my home theater.  Your experience with the sonotube would really interest me if you cared to share it sometime. You are the second 6-footer I have encountered, although I am sure there are more.  It sounds like you had only one driver and it sounds like it worked out.  

 

Any, way really do appreciate your thoughts. You have me reconsidering many things, and that is always helpful.

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One decision you need to make is whether you are okay with a ported design (rather then sealed). The other is how low does it need to go (realistically)?

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This was the driver I used in my sonotube project. It was a popular one and used by many folks.

Dayton Audio RSS390HF-4 15" Reference HF Subwoofer 4 Ohm
Part # 295-468 

As I recall, in a sealed box it needs about 5 cu ft and in a ported box it needs about 10 cu ft.

There is freeware that is invaluable: Sonosub (or something like that) and WinISD.

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Thanks so much @PrestonTom  I am using the Sonotube software along with  WinISD, but having problems with the latter.  I am looking for any other software worth using as well . Trying to figure out Unibox and looking at others but hard to which are worth the cost or worth using.

 

I have always planned it as ported, but am not quite sure why.  The drivers I have looked at seem to need a lot less space enclosed than ported, but I am basically trying to what happens if a lot more volume can be efficiently used.

 

As for how lot it needs to go, I tried listening to tons on YouTube at everything from 15 Hz to 30 Hz.  We have FireTV, so I did that on the home theater system.  Even at 30 Hz, I really don't hear anything, At 20 and below, I heard nothing, but felt vibrations and things i the room shook. This is not about going really low, so maybe 18 Hz or so. If it goes lower great, but that is not the point of the project.

 

I did have a goal of seeing is these super subwoofers that some people are making now can actually be used for home theater.  It seems that in theory a 24 inch driver should be a lot of fun if made well, but I don't see how they get into a traditional box.  And if it were truly possible to use 2 24-inch drivers in the space of a 36-inch circle, I suspect a lot of people would find the room. Maybe I am dead wrong.  Happens all the time.

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What size port or ports will you be using? And are you going to wire the drivers out of phase?
Also remember to make your base of the tube at lest Half the weight of your drivers so that it will stand up without any problems, As for your amp or amps, I would look at some pro line mid term high end amps like qsc, Yamaha , crown and so on
I used a Yamaha p5000s for a 15” tuba sub system that I ran for two years and it was a great amp. I hear all these people talking about those cheap Barringer amps with dps in them . I can’t see a amp that’s only 9lbs lasting very long with driving high watts
If you have a high end preamp for HT it should be able to do all the dsp stuff for you. If you going to be using a amp or amps that will be away from the tube , email me. I have a great single speaker cable that’s 49 feet long and it’s made just for subs. I’ve mad a few tube subs in my days so if you need some help hit me up and I’ll be more then happy to help. My email is carlthess@icloud.com
I can’t wait to see some pics of it
Or even some blueprints. Oops , showing my age with that word. Lol. Good luck

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3 hours ago, carlthess40 said:

What size port or ports will you be using? And are you going to wire the drivers out of phase?
Also remember to make your base of the tube at lest Half the weight of your drivers so that it will stand up without any problems, As for your amp or amps, I would look at some pro line mid term high end amps like qsc, Yamaha , crown and so on
I used a Yamaha p5000s for a 15” tuba sub system that I ran for two years and it was a great amp. I hear all these people talking about those cheap Barringer amps with dps in them . I can’t see a amp that’s only 9lbs lasting very long with driving high watts
If you have a high end preamp for HT it should be able to do all the dsp stuff for you. If you going to be using a amp or amps that will be away from the tube , email me. I have a great single speaker cable that’s 49 feet long and it’s made just for subs. I’ve mad a few tube subs in my days so if you need some help hit me up and I’ll be more then happy to help. My email is carlthess@icloud.com
I can’t wait to see some pics of it
Or even some blueprints. Oops , showing my age with that word. Lol. Good luck

 

Thanks, all of that was helpful.

 

I figured that the port size would dictated by the rest of the the design in the end.  I have even thought about looking into leaving both ends open in an open baffle kind of way, but that was just an idle thought.

 

For stability, I have considered high density concrete at the base, and I have also wondered if it would be feasible to suspend it from the ceiling. If the connection were some kind of textile,, it might not transmit vibrations.  I have no idea what that would do, but it would achieve close to complete isolation.

 

As I understand it, opposing drivers are usually wired in phase.  I know there are wave cancellation issues, but have not gotten that far yet.

 

Will reach out to you directly.

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In case anyone is following, I have resolved the questions about the enclosure and will order pieces for a 5/8 inch curved plywood tube 36 inches in diameter and six feet long this coming week.  They offer full circle, half circle and quarter.  The pieces normally are 36 inches long so I will need to join them. My plan is to get 2 half circles and 4 quarters and then permanently join one of the quarters, leaving a quarter opening.  I will use the remaining pieces to make a removable door that is sealed when in place.  That way I can get into it to work on it. The wood will cost $400. The door equipment will cost a few hundred more I am guessing. I am assuming that I want it air tight, but not sure on that.

 

I am getting the HS-24 Mk II drivers from SI and Nick there has been really helpful.  He actually seems to want to see what will happen. SO I contacted him about amplifiers, and he just said to use speakerpower.net.  If it works for him, it works for me, and they have a 4000W plate amp with 2 channels for $999.  That should power both drivers perfectly and is cheaper than I had feared.

 

So it seems that parts have all been decided and I should have them by end of April. And that leaves getting serious about learning design. So if you don't see me much for a while, I am in the library.

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8 hours ago, vasubandu said:

And that leaves getting serious about learning design.

The design should be finalized before you purchase anything.

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8 hours ago, vasubandu said:

My plan is to get 2 half circles and 4 quarters and then permanently join one of the quarters, leaving a quarter opening.  I will use the remaining pieces to make a removable door that is sealed when in place. 

A sonotube would probably be stronger and seal better that a bunch of pieces glued together.  What is the removable door for?  What will you need to access through the side of the tube that you can't get to through the driver openings?  Do you think you'll be creating more pressure than a sonotube is rated for?  From their site:

 

This pressure at the bottom of a Sonotube is approximately equal to 150 lbs/square foot (psf) for every foot of concrete height. Sonotube Round forms are designed for 12 feet of full liquid head, ie: 12 feet x 150 psf/ft = 1,800 psf. Sonotube Commercial and Finish Free are designed for 20 feet of full liquid head, ie: 20 ft x 150 psf/ft = 3,000 psf.

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Keep in mind that your ports should end up being significantly larger than this.  This is actually a pretty small enclosure for two 24's and I imagine it's tuned relatively high like in the low 30's or at least close. 

 

 

 

 

 

 

 

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On 2/10/2018 at 4:38 PM, vasubandu said:

But that whole walk before you run never made sense to me.  

There's a reason that the saying rings true.  Basically you don't know what you don't know.

 

It would be best to build a small sub, make some mistakes and learn from those mistakes.  It's infinitely cheaper in the long run.  

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2 hours ago, CECAA850 said:

It would be best to build a small sub, make some mistakes and learn from those mistakes.  It's infinitely cheaper in the long run.  

 

It would.  I think it was Jesus who said “Watch and pray, that ye enter not into temptation: the spirit indeed is willing, but the flesh is weak.”

 

On the positive side, I have been considering making a 24 inch tube at the same time or even first.  That would be smaller if not technically small.  You cannot imagine how frustrated my wife gets, but she says she loves me anyway.  

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5 hours ago, CECAA850 said:

The design should be finalized before you purchase anything.

 

That was my original thought, but since I have to join the parts of the tube and since they are not precise sizes, I thought that getting them made since so that I could make physical measurements instead of using hypothetical dimensions.,  I certainly would not buy any other parts until it was all planned and designed. With the tube I am going ot get what I get, and I won't be able to change it.

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5 hours ago, CECAA850 said:

A sonotube would probably be stronger and seal better that a bunch of pieces glued together.  What is the removable door for?  What will you need to access through the side of the tube that you can't get to through the driver openings?  Do you think you'll be creating more pressure than a sonotube is rated for?  From their site:

 

I can easily join the plywood with a seal of equivalent strength. The idea that a cardboard tube would be stronger than a tube made of 5/8 inch plywood seems dubious to me.  Sheer walls are made of plywood, not cardboard.  I want easy access because I want to be able to change the location of the drivers.  The idea of moving a 115 pound driver through a 36 inch access point does not sound like fun. I am being helped by a contractor friend who is a magician with wood, and he says this will be a few hours on a Saturday afternoon.

 

Part of this is just that I have always envisioned it as a substantial wooden structure.

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4 hours ago, MetropolisLakeOutfitters said:

Keep in mind that your ports should end up being significantly larger than this.  This is actually a pretty small enclosure for two 24's and I imagine it's tuned relatively high like in the low 30's or at least close. 

 

Thanks, That is a good point.  I am going to guess that box is 4x2x2, or 16 cubic feet before driver space.  In a ported sub the  SI HS-24 is rated for 16 to 20 cubic feet, so with 2 of them 32 to 40. Even with large ports, I don't see how it works.  Of course, they know a lot more about it than I do, so I am not saying that I am right. I am just thinking and wondering if they would work better with twice the volume.

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50 minutes ago, vasubandu said:

 

I can easily join the plywood with a seal of equivalent strength. The idea that a cardboard tube would be stronger than a tube made of 5/8 inch plywood seems dubious to me.  Sheer walls are made of plywood, not cardboard.  I want easy access because I want to be able to change the location of the drivers.  The idea of moving a 115 pound driver through a 36 inch access point does not sound like fun. I am being helped by a contractor friend who is a magician with wood, and he says this will be a few hours on a Saturday afternoon.

 

Part of this is just that I have always envisioned it as a substantial wooden structure.

It's not what's stronger, it's what's needed.  Two drivers won't blow a sonotube apart.  Anything more than that is extra money spent.

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1 hour ago, vasubandu said:

With the tube I am going ot get what I get, and I won't be able to change it.

That's not how subwoofer design works.  You take the driver(s) load the TS parameters into a modeling program, figure out what tune you want, check port velocities and driver excursion THEN see what type enclosure is recommended by the program.  At that point you'll have some sort of educated guess as to the enclosure size.

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48 minutes ago, CECAA850 said:

It's not what's stronger, it's what's needed.  Two drivers won't blow a sonotube apart.  Anything more than that is extra money spent.

 

OK now that I get.  Makes a lot of sense. In this case, my sense is the extra money would not necessarily be wasted, although it depends on how things go.

 

I am very focused on appearances because in my world, appearances are more real than reality. If I want to present this as something genuinely different, which in many respects it isn't, then any distinction I can create helps. I just think that the reaction to a huge tube of curved plywood will be different than the reaction to a giant sonotube.

 

It occurs to me that none of this will make much sense to most people here.  If they were going to spend the money for 2 HS-24 drivers and an amplifier to driver them, their only concern would be to make the best subwoofer they could using established methods.  And they would be right. 

 

Unless I blow the drivers, I can always go that route after my experiment. But for now, I am having my own kind of fun testing a few ideas, and I am sure that more will come to me. I mean, what would happen if I had 200 one-inch ports all over the sides (equivalent to 8" round port)? What would happen if I pulled the drivers a foot or two into the tube? Or changed their direction? With any luck,I will have a setup so I can try those things and hear what it does, not just look at some chart. Of course the 200 holes would require a shall replacement. In the end, maybe I will find nothing, but I will have not finding it. 

 

In the meantime, your comments are all appreciated.  I take them seriously and give them serious thought.  You have saved me a lot of time going down pointless paths.

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