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Discussion Starter · #1 ·
Ok, here is the situation. Like many others that join up here, I started out a while back in search of a nice sub for my HT. My great-uncle has an amazing HT system, including a number of great subs that he built himself about 20 years ago. With that experience in mind, I started looking around to learn how to build my own. After a while, I ended up here. I have lurked here for a number of months now, and I have learned a lot.

The enclosure:

As the thread title says, I'm designing an end table sub. The exact dimensions are not completely set, but the total gross interior volume looks like it should be somewhere around 8-10ft^3. Right now its approximately 21h x 30w x 26d (all interior dimensions). The external dimensions are limited to 27h x 34w x 34d.

I am planning on a bottom firing, slot ported build. The sub enclosure itself will be a simple box, with the end table design pieces being added on after. So the top of the end table will have its own "finish" piece of wood (making it double thick effectively). The legs will also be added onto the sides this way as well.

The components:

I purchased a 300W BASH amp from PE during the 4th of july sale (got it for $109 I think).

I have narrowed the drivers that I'm choosing between to two. The Dayton RSS390-HF, and the Stereo Integrity 15. With either driver, I'm targeting for the tuning frequency to be somewhere in the 15-19Hz range.

I got WinISD mostly figured out, and after lots of modeling I decided on the HF. Then I remembered that the BASH 300 has a very slight 1db bass boost from 25hz - 30hz. It also has a high pass filter that I didn't account for at first.

The Question

I'm having a hard time modeling the filters and bass boost for the BASH 300 in WinISD, and then choosing the correct driver, and enclosure size.

Without any filters, the SI has a bit of a dip in output between 25-40hz or so (using 9 ft^3). Depending on how I add the bass boost, it really helps bring up the slight dip. Meanwhile, the HF is relatively flat without the boost, but then when the boost is added, it becomes peaked in the same range that the SI is usually dipped.

I'm having a hard time determining which driver to choose based on this, as well as the exact enclosure dimensions to work with it.

Making the choice harder is accounting for the High Pass Filter, it appears that either driver could be hitting its xmax right around the tuning frequency without it, and when I add it in, the extension is cut off quite a higher than it otherwise might be.

Sorry for the long post, but I hope I covered most of what I was needing help with.

Thanks in advance :).
 

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Welcome to the forums!

If you have 10 cu.ft. available then the net volume after deductions for porting, bracing and the driver would be about 8.5 cu.ft. Both drivers will produce the same output, the difference will be in the cone excursion. The RSS390-HF will be at its Xmax limit while the Stereo Integrity 15 will be using about half of its capabilities.

As for filters, the HPF on the Bash 300 is 17.7 hz. The 1 db of boost in the 25 - 30 hz range is minimal, that can be shown in the modeling as a Parametric EQ filter with a center frequency of 27.5, a gain of 1 db and a Q of 1.

Here are the Project Files for both drivers, save the files to the Projects folder in WinISD. I'm assuming you are using WinISD Pro.

View attachment ocnlogan 390HF.wpr

View attachment ocnlogan SI 15.wpr
 

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Discussion Starter · #3 ·
Thank you so much for the project files, I'll load them up tonight when I get home from work and play around. Although it sounds like the SI 15 might be the better choice here.

I'm not actually sure if I'm using winISD pro or not, but I'd hope that the project files work fine for both? It sounds like I was doing the bass boost filter correctly, but we'll wait and see on the HPF.

So, is this enclosure too large for the SI 15? I know that on the SI site it recommends 6ft^3, but since I've got more space to use, I figured I might as well use it, and thats just the size that it worked out to be.

Additionally, once I get around to choosing a driver, I have to learn a bit more about how to brace this thing. I do know that going with a slot port should help keep the box a bit more rigid (in comparison to a few PVC ports), and that the double thick top should help with that as well, but other than that, I'm not sure how much bracing a build like this really needs.

I should also add that I'm going to be building this out of 3/4 veneered ply (ebonized walnut and cherry finish), and not MDF. That shouldn't change anything that I'm aware of, but I thought I'd disclose it just in case.

Thanks again for the help :).
 

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A bigger box means more low end output in most cases, model the driver in 6 cu.ft. tuned to 19 hz and 11 cu ft tuned to 19 hz and then compare those to the file I uploaded.

Bracing will be determined by the final internal dimensions you come up with. A rule of thumb is no internal panel is bigger than 12" x 12".
 

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Discussion Starter · #5 ·
So after taking the chance to look at both of the projects, here are my thoughts. It appears that the SI build is superior in the flatness of the response curve.

I played around with changing the HPF and the bass boost of the amp for a while. But after thinking about it, and taking a closer look at the amp, I don't really know if it is worth the effort of changing the resistors (I am ok at soldering, but don't have my own kit). So it looks like I'll be sticking with the standard bash settings. And that means that I should be able to start finalizing the specs and design.

The Specs

So now I'm down to the very last bit of figuring out the size. This is what I have now.

Exterior dimensions of 27in tall, and 34 inches for the width and length.

The top will be "double thick", the legs will be 4 inches tall (that should be enough for a bottom port should it not?). 27 - 4 - 3(.75) = 20.75 in of interior height.

Width and the length are pretty simple. there will be a one inch overhang for the entire box (to make it look like an actual table), that works out to 34 - 2 - (2*.75) or 30.5in.

Gross interior volume then == 11.17 ft^3. Accounting for the driver (.19 ft^3), that leaves me with 10.98 ft^3 to work with.

Now comes the port. I was thinking a slot port would be much easier to build, and should help with the bracing should it not? I know the port velocity should be less than 17m/s. I also understand that slot ports should be no smaller than 2in on their thinest to prevent it from whistling. With the box being square then the slot port would be 2in x 30.5in. The air speed says it should be 9.25m/s with a port length of 44in.

The Questions:

My question about the port is pretty simple. Am I wrong thinking that I need to have the port be the full width of the interior? And if I do in fact need the port to be the full width, can I go narrower than 2in. Or should I use a rear facing slot port, so then its only 20.75in tall (which gives max airspeed of 14m/s).

Now how should I get started with designing the bracing?

Thanks again for all of the help, and sorry this is kind of a long post, but hopefully it was relatively clear.
 

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Discussion Starter · #6 · (Edited)
So, I put some time into the project again, and changed some things. I realized that I would have to slightly change some of my size specs. I made it slightly narrower and longer. This way it fits through front doors without having to take the door off. It should also now fit through hallways a bit easier.

Also, this time I'm attaching the project file, as well as the excel file that I'm using to calculate the volumes that I'm dealing with. I also took a stab at creating what I'm talking about in a sketchup file so that it would be easier for you guys to visualize.

I have decided on a bottom facing slot port, although that is not shown in the model.

Right now I have just have two questions.


1)

The bracing. I read that the rule of thumb is that there shouldn't be a space longer than 12in that doesn't have bracing. So from my specs, I'd need probably two along each side, and one on the inside height axis. Will corner braces from scraps brace a box this size well enough? Or am I going to need cross bracing like some sort of dowel or something like that?

2)

Since I've tweaked the project quite a bit, and I believe I have everything from excursion to port air velocity figured, I'd love to have someone go over it real quick and double check things for me, and make sure I didn't make too many boneheaded mistakes.

Thanks for the help so far :).
 

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Discussion Starter · #8 ·
Glad that the project looks right, and thanks for looking things over for me.

And you're unable to open xls files in general, or did mine get uploaded wrong?

The interior dimensions of the cabinet are:

Height = 20.75in
Length = 27in
Width = 31in

Total gross volume = 10.05
subtracting sub = 9.86
subtracting port = 9.09

And now like I said, I'm stuck on bracing, as I simply don't know how much I'll need. I read the "no space longer than 12in without bracing" rule, but that doesn't specify about if something simple like a triangle shaped corner brace would work, or if I need something that spans the length of the interior.

Thanks again.
 

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I'm unable to open xls files in general.

Corner braces are fine for bracing corners, they do little for the center of the panel where the vibration issues arise. I would suggest 2 vertical window pane braces, one front to back and the other side to side in a X configuration. You'll have to design the panels with a relief for the driver.
 

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Looks like a nice design, you should love the SI driver, they have great sound quality, lots of deep output too.
 

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Kinda looks like my 8 footer.



You'll love the SI driver.
 

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Discussion Starter · #13 ·
I'm sure that not being able to open xls files is by choice, but just in case you didn't know, you can get Open Office or Libre office for free, and they can open and save xls files (its what I used actually).

I was thinking of about 8in on the triangle corner braces if that makes any difference. If I did them like you did yours, then I think I could go larger. But it sounds like instead of doing that, it would be better to use a "window pane brace" as my cabinet is on the largish size. After looking around for a bit that window pane bracing this is actually just a generic term for a style of bracing. Is that right? Like a lattice, with

So a single window pane brace in each direction, is that the same idea as something like this? Of course, if I used dowels, it would be two per side (six total) would it not? Or maybe I'm not visualizing it right.



I think it would be cheaper for me to use dowels if it does the same thing, but if it doesn't then I'll see if I can swing the window pane braces (I'm planning on doing the cut layouts this weekend, so I'll see if I am forced to buy another sheet or not, and that will likely sway my decision).

Thanks again :).
 

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Discussion Starter · #15 ·
To be clear, thats not my design up there, but just an example I found on the internet.

Does it matter what size dowel is used?
 

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Discussion Starter · #17 ·
Sorry for the Necro thread, but today I started talking to a co-worker about my subwoofer, and at that time I remembered that I had never come back here and posted the results of my first build. So I'm trying to correct this problem.

I did write everything up here, even if it is a bit wordy (if its too long, you can look at the pictures :)).
http://loganslearnings.blogspot.com/2013/11/logans-leisure-2-end-table-subwoofer.html

Anyway, many thanks to those that helped me. The Sub has been working flawlessly since day one. It also looks, and sounds outstanding.

Also, since I haven't looked at things in a while (since I built this first and only sub), I was surprised to see that it appears that Stereo Integrity discontinued the driver I used :(. Now I can't reuse my plans if I want to make another sometime down the line.
 
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