Seriously thinking about this and wondering why I am wrong

[vasubandu]

29 minutes ago, wvu80 said:

It looks like a cool build, but is it a good subwoofer?  In other words, does it do what it is supposed to do?

 

He claims it is world class.  I sent him an email, and we shall see.

 

30 minutes ago, wvu80 said:

He spent a LOT of time money and effort to make giant sonotube sub that doesn't work as well as a standard sub. 

 

There's a lesson in there somewhere. 

 

That is an excellent point.  And it reminds me of a saying I have been drilling into my poor little kids for much of their lives. "If it is not worth doing wrong, it is not worth doing at all."  Most people resist that and say i have it backwards, that is should be "If it is worth doing, then it is worth doing right." But just about everything is worth doing right. The question is do you care enough to try something that you are willing to accept failure.  I take on all of my crazy projects completely prepared to accept failure.  It isn't really failure so much as negative information.  Oh, that does not work after all.  Now crappy sub would suck,  but if it could be fixed, that would be something. Thomas Edison famously failed over 1,000 times before finding tungsten.  A lot of people would just want to get a good sub out this. I just want to figure out if the idea works.

 

Weird I know, but sometimes I just gotta be me.

[cincymat]

1 hour ago, vasubandu said:

 

I cannot thank you enough for that.  As much as I looked, I never found it, but he used the format I am talking about.  Different river configuration, but at least is is a start and it comes with direction.   @cincymat you just made my day.

You're most welcome. I'm pretty good using "the google"... 

[JohnA]

Fortunately, woofers/subwoofers are the easiest of speaker designs.  To do your own, you need a software simulator:

https://www.parts-express.com/bassbox-lite-software-cd-rom--500-921

https://www.parts-express.com/eminence-designer-speaker-box-design-software--500-945

https://www.parts-express.com/bassbox-6-pro-software-cd-rom--500-923

 

Schedule 40 PVC pipe is a much better choice than Sonotube for both stiffness and strength.

 

All drivers MUST be in phase.  If half are 180 deg out of phase your sub will have zero output. 

 

You need to decide how deep you want it to go and how big you are willing to accept.  I caught a deal on a JBL 15" woofer in college and wanted to build a sub.  After running the calcs, it needed an 18 cu. ft. box (!!!) to hit 20 Hz.  I had the wrong driver. 

 

Parts express has some pre-designed kits that would be an excellent place to start. 

[vasubandu]

@cincymat I have long considered myself to be a Google master.  Legal research is all done online now with Boolean search terms, and I spend at least an hour day on it. Most of my Google searches use Boolean connectors too, and almost never find anyone who even knows they exist. But after hours of searching, I did not find that article, so I have to say that you are an amazing googler.

[vasubandu]

1 minute ago, JohnA said:

Parts express has some pre-designed kits that would be an excellent place to start. 

Thanks.  18 cubic feet would be 31,104 cubic inches.  Very few subwoofer boxes would have anywhere near that.  My imaginary 6 foot by 20 inch tube would have 22,608 cubic inches or 13 square feet.  18 cubic feet would be 3x2x3 feet,  and that inside.  

 

They do not have kits for round subs that I could find, and certainly not 6 foot kits.

 

It really seems like other than guy that @cincymat found, no one has tried this.

[vasubandu]

21 minutes ago, JohnA said:

Schedule 40 PVC pipe is a much better choice than Sonotube for both stiffness and strength.

 

Out of curiosity, why Schedule 40 and not 80? I can break schedule 40 and it gets brittle over time, but schedule 80 is totally different.  If you wanted mass, Schedule 120 would provide it.  Someone on Alibaba has clear 20 inch pipe that looks like 40 or higher. That might be fun.  A see-though subwoofer.

[JohnA]

Because Sch 40 is 19/32" thick. 

[vasubandu]

4 minutes ago, JohnA said:

Because Sch 40 is 19/32" thick. 

 

I know that, but is that too thick? Do we want thinner or thicker walls?

 

And at what length?  Schedule 40 is .365 at 10 feet and .5 inches at 16 feet. 

[wvu80]

7 hours ago, vasubandu said:

I know that, but is that too thick? Do we want thinner or thicker walls?

Thicker.  If you get a thin wall that resonates that is distortion.  Thicker is much more resistant to vibration, along with proper bracing.

 

My DIY sub Reference 15, from PE has 3/4" MDF all around and is 1.5" on the front baffle with massive bracing.  You need mass because those big subs move a lot of air, have a lot of moving mass and a sub will walk across your floor if you don't take steps to anchor it, with carpet spikes for instance.

[vasubandu]

1 minute ago, wvu80 said:

Thicker.

 

That is what I thought but in DIY forum, someone suggested the opposite.  The idea of a cardboard subwoofer kind of bothers me.  A comp[any called Shapes Unlimited has a fascinating product.

 

 

The say

 

We stock a substantial inventory of geometric convolute shapes and spiral cores. From 3" diameter to 48" diameter spirals or any one of our unique geometric convolutes. Shapes Unlimited carries the stock inventory for your quick ship. We can also fabricate and finish to your exact specification. If a special non-stock spec is required, we can also run to your requirement.

 

 

Our fiber tubes are wax-free and made from multiple layers of heavy-weight fiberboard. Their laminated construction makes them strong and allows you to combine sections of tube with plywood, solid stock, or particle board to create attractive components with radius corners. Every geometric shape can be finished with high-pressure laminate, paint, or wood veneers. With the wood veneer option, you could make something beautiful.

[wvu80]

8 hours ago, JohnA said:

Fortunately, woofers/subwoofers are the easiest of speaker designs.  To do your own, you need a software simulator:

@vasubandu JohnA ^^^ gave you links to some essential tools for you to learn if you are interested in building a quality sub from scratch.   These are the tools the really good speaker designers use. 

 

Again, I think you should pick up a kit, it doesn't have to be a big 18" sub, but something you can enjoy putting together.  Then you can use it to try your hand putting on a nice veneer.  There are several people here who have refurbed large speakers like La Scalas with custom veneers and they are so beautiful they would just make your jaw drop.

 

I would love to be able to veneer.  I have a couple of DIY enclosures I have in mind to veneer when I get the knowledge, tools and experience sometime in the future.  Right now it's beyond my skill set.

[vasubandu]

41 minutes ago, wvu80 said:

JohnA ^^^ gave you links to some essential tools for you to learn if you are interested in building a quality sub from scratch.  

 

He did, and they are. I am using them as my basic guide.  I seem to be going outside the lines, but  those are amazingly helpful.

 

OK OK I will get a kit and put it together.  I may not enjoy it, but I will do it and post a picture for proof.

 

Veneer is not all that difficult in that there are not a lot of skills to be learned, but it is unforgiving. I think it is a dive in kind of thing.  But some cheap veneer and practice.  You will get better quickly, but not good enough for a La Scala any time soon. I have tons of resources if you want them.  Remember that saying about measure twice, cut once?  The guy who made it up was a veneer specialist.

 

 

[vasubandu]

Well, I have learned a lot over the last week.  More than I did in months of research before.  

 

The answer is a tube with opposing drivers at each end.  Boring except that these will not be your normal drivers.  They will be SI HS-24 MK II.  Great 24-inch drivers for $1,275 each, or a lot less than 6 18 inch drivers.  And for he tube I will use Shapes unlimited because they are half an inch thick and more substantial than cardboard.  

 

I was confused so I called Nick at SI, and he confirmed that the HS-24 specs call for 16-20 cubic feet of air for a ported HS-24, and that it would be doubled for two of them. But he said that the HS-24 is so flexible it can be used in smaller spaces.  I asked him if anyone had ever set up a pair with 32-40 cubic feet, and he said not to his knowledge, but he would really like to see one.  I told Nick I would have it all measured and send him the data when I am done.

 

And that made it come together for me.  Not as in I am going to start building tonight. I still have so much more to learn and will have so many more parts to get, but at least I know what I need to learn,and I feel like i am on firmer ground heading somewhere real. I suspect that I will have $5,000 into it before I am done, and I know I could get a lot more subwoofer somewhere else with that money, but where would the fun be?  Of course, it if works, I will have to make another.  You can't have just one subwoofer.

 

I took the WinISD program and entered all the data I could find for the HS-24 MII, and this is what it showed.

 

[Paducah Home Theater]

On 2/8/2018 at 1:48 AM, vasubandu said:

I just don't want to try something that has been tried and failed or that violates some basic rule unless I want to test the rule.

 

For whatever little it's worth since you asked... I realize it's a cylinder but I'd still have a hard time bolting 230 pounds worth of drivers with a total of 3.5 pounds of moving mass to something that is only half an inch thick and weighs a fraction of what the drivers do with no way to brace it properly.  You're going to have to have a lot of port area to keep the velocity down as well which means that tube is probably going to be a bigger diameter than you are thinking just to squeeze the ports and driver on the baffle on the end of the tube.  Regardless of that, just looking at the Shapes Unlimited catalog on page 17, you're going to have to get the 43" tube just to get enough air space, the next size down is too small if you calculate the volume of the cylinder.  At that point you're literally at the same size and weight of a Klipsch 1802 while not performing as well, costing more, and having little to no resale value.  If you want to learn about speaker building take the aforementioned advice and just start with a simple kit.  I'm afraid you're going to be in way over your head on this idea.  

[vasubandu]

17 minutes ago, MetropolisLakeOutfitters said:

 

For whatever little it's worth since you asked... I realize it's a cylinder but I'd still have a hard time bolting 230 pounds worth of drivers with a total of 3.5 pounds of moving mass to something that is only half an inch thick and weighs a fraction of what the drivers do with no way to brace it properly.  You're going to have to have a lot of port area to keep the velocity down as well which means that tube is probably going to be a bigger diameter than you are thinking just to squeeze the ports and driver on the baffle on the end of the tube.  Regardless of that, just looking at the Shapes Unlimited catalog on page 17, you're going to have to get the 43" tube just to get enough air space, the next size down is too small if you calculate the volume of the cylinder.  At that point you're literally at the same size and weight of a Klipsch 1802 while not performing as well, costing more, and having little to no resale value.  If you want to learn about speaker building take the aforementioned advice and just start with a kit.  I'm afraid you're going to be in way over your head on this idea.  

 

Those are a lot of my questions. 

 

The volume of a tube with a 35.5 inch inside diameter and six feet of length is 71, 263 cubic inches or 41.24 cubic feet. The HS-24 itself takes up .75 cubic feet each, o 1.5 cubic feet total, leaving me at 39.74 cubic feet.  The HS-24 in ported mode likes 16-20 cubic feet of air, so with two that is 32-40. Even if bracing and everything else takes up 5 cubic feet, which seem improbable, I would still be in the sweet spot.  So it it hard for me to see how I will not have enough air space.  For a box to have the same 41 cubic feet, it would need internal space equivalent to a cube 3.4 feet per side, and I don't see any of those around.

 

Your  bracing/mounting question makes a lot of sense and  it occurred to me.  I hope that I can learn something from the Sonotube people.  Because it is a  tube, the walls are very stable, but still.

 

I just do not understand your statement that I'm going to have to have a lot of port area to keep the velocity down. It sounds like a serious concern,  but I just have not learned enough to understand it yet.  

 

On the tube itself, I had a great conversation with a guy there, and he said that they could do just about whatever I wanted on a custom basis. Making the walls an inch thick would run about $200 he said.  There are some other more intriguing options, but  I have not been able to reach them.  Made with wood, not fibers. But finding the right tube  will be a big part of it.

 

Something like the 1802 would be an attractive alternative, particularly if one could be found cheaply I have plenty of contacts in the business liquidation area, and if a theater closed, I bet one would sell for not that much.  No idea if that is realistic or not.  I have seen some Klipsch professional stuff in that context. But a great subwoofer is my secondary goal here.  My first is to turn this goofy idea into reality and see what happens.  

 

I really appreciate your thoughts here, and your taking the time to look at the catalog.  I have so many things to wrap my mind around, and now even more, but it seems manageable and doable. Thanks.

 

 

[Paducah Home Theater]

25 minutes ago, vasubandu said:

I just do not understand your statement that I'm going to have to have a lot of port area to keep the velocity down. It sounds like a serious concern,  but I just have not learned enough to understand it yet.  

 

 

The smaller of a cylinder that air is pushed through with the same force, the higher velocity it is.  If the velocity is too high, you get distortion in the form of what people call chuffing, you can hear the air huffing in and out of the port.  If you want pure bass the area has to be large, which also means the length has to be long.  Two 24's with high xMax in a single box is about as bad as you can get in terms of needing a lot of area on your ports, depending on the tuning of course.  WinISD can model this.  

[rebuy]

I have some Polk speakers and they use what is called a Power Port

for bass control and extension. It slows down air coming out of the port

and eliminates the chuffing sound of normal ports while at the same time

extending bass output up to 3 db.  It works rather well.

It's a plate with a cone in the middle pointing into the port and it

distributes the air coming out of the port in a even manner.

[vasubandu]

1 hour ago, MetropolisLakeOutfitters said:

WinISD can model this.  

I added the speaker to WinISD to the extent that I could.  

 

In WinISD I had to add the driver.  The online information had most of what was requested, and the other stuff autofilled.  A few are still 0.00 - fLe, KLe, Xlm, PeHc, Hg, Also nothing for AfaVC, R(t), C(t), SPL max, Mcost. On dimensions I do not know magnet and basket, or Vcd or Dvol.  So if the missing information matters, then it is not accurate.  It never asked about shape or obstructions. I left connection at parallel.  Driver is vented.  Tuning is 18 Hz.  Vents are 1, 10.2 cm., round, volume 1,100 liters.  Seems like I am missing another setup that I left as it was.

 

These are the velocities.

 

 

 

 

 

 

 

 

[vasubandu]

So those HS-24 have 2000 watts RMS power handling. Does that mean that actually want a 2000 watt amp for each one or a 4000W amp with 2 channels if such a thing exists?  At that level, am I looking for an amp or a plat with the amp?

[vasubandu]

And I think that I may have stumbled across another part of the puzzle.  Why have cardboard when I could have wood (need to look at issues)? Just 40 miles away is a business that specializes in bending wood.  Maybe two plywood halves and join them.  But for these guys, that would be a walk in the park.  Their stuff is amazing.

 

http://www.puretimber.com/architectural/