Atlas 12 sub project

[Airplay355]

I'm going to build a sub with an atlas 12 sub driver and a 300 watt BASH amp. The only thing is, I have no idea how to build a sub box. I don't know what would sound good, what would sound bad, or how to get the most out of my driver. I downloaded unibox and put in the small parameters. I don't really know what I'm doing but I think it says with a 1 port box I'd have an -3db point of 28 hz? Is that kind of high? Do I want it to be lower? Can I make it lower? Someone help me out or atleast shoot me some links I can use lol.

[gatemplin]

Email Chad at Ascendant, tell him how about the amp, your desired output and extension, and the approxiamate desired dimensions. He'll know better than anyone.

[gatemplin]

If you dont know what you what to achieve with the sub, I might be able to help. This should end up being a very nice subwoofer.

[tryrrthg]

Check out this thread.

http://www.polkaudio.com/forums/showthread.php?t=34042

[Early B.]

I used this link to build my Atlas 15 driver:

http://www.frontiernet.net/~trtinkerer/overview.html

This is one of Chad's designs, I believe. It should also work with the 12" driver, but gatemplin can correct me on that one.

Question -- what are your design goals? Is it primarily for HT or music? How low do you want it to go? Any WAF considerations or space constraints for box size? Sealed or ported?

The box is not difficult to make as long as you follow the directions carefully and plan everything correctly. If making straight and accurate cuts is not your thing, get a wood shop to do it. Might cost you around $60 if you supply the MDF, but at least you'll know it's done right.

[tryrrthg]

That box would be too big for the Atlas 12. he should probably follow one of the Shiva plans I posted in the other thread.

[Airplay355]

It would be primarily for music but would also be used for movies. I don't have a wife or anything because im 18 so size isn't an issue. It just has to fit in my room and not be outrageously big. No couch sized subs lol. Maybe 60% music 40% HT or 70% music 30% HT.

I want the low extension and high output for movies but I don't want the bass to be sloppy when it comes to music. I was thinking a ported box was what I want? Because it has deeper extension and a flatter fq curve?

I'll atleast try to make the cuts myself. I have access to a table saw so that would make things easier I think. I just don't know how to design a box. As soon as I start thinking it's as simple as putting a driver in a box I learn about all this stuff to make the sub sound better. So I want to have the best sub I can with the driver and amp I picked.

I'm gonna check out the links you guys provided.

[gatemplin]

I used this link to build my Atlas 15 driver:

http://www.frontiernet.net/~trtinkerer/overview.html

This is one of Chad's designs, I believe. It should also work with the 12" driver, but gatemplin can correct me on that one.


:) Enclosures are based on the T/S parameters of the driver, and since the specs are different for both drivers, the box probably is not optimal.

[gatemplin]

he should probably follow one of the Shiva plans I posted in the other thread.

Yeah, Airplay, copying those designs will work well. Adire does a very good job of designing sub boxes.

[Airplay355]

In the thread it says the sub will reach it's excursion limits at 30 hz? I want my sub to go lower then that. The fs of the atlas is 23.2, doesn't that mean I can go lower then 30 hz?

[gatemplin]

In the thread it says the sub will reach it's excursion limits at 30 hz? I want my sub to go lower then that. The fs of the atlas is 23.2, doesn't that mean I can go lower then 30 hz?

That is because it is an EBS design. Below 30 Hz, excusion begins to decrease. My sub is an EBS too. I still get good output above 17 Hz, but excusion is max around 30 Hz. You have to factor in the ouput of the vents too.

The EBS design will dig the deepest, and be the loudest in the low 20s, but around 30 Hz, and above the smaller designs will be louder.

[Airplay355]

How much of a difference will there be? Will 30 hz be 10 db down from 20 hz? Will I be able to hear things get quieter as the bass gets deeper? I listen to alot of trance so bass is very important. From what you are saying it seems the EBS design will be the best for me. Is it hard to build?

[tryrrthg]

Here is a quick plot of what the Atlas 12 looks like in the Shiva EBS plans. Factor in room gain and you'll be going STRONG to below 20hz.

[gatemplin]

How much of a difference will there be? Will 30 hz be 10 db down from 20 hz? Will I be able to hear things get quieter as the bass gets deeper? I listen to alot of trance so bass is very important. From what you are saying it seems the EBS design will be the best for me. Is it hard to build?

I meant loudest relative to the other designs. The output at 30 and 20 Hz should be about the same, within a few dBs. That is the point of an EBS.

The Adire plans are easy to build, as far as speaker boxes go. It depends how experienced you are with the tools. It is do-able. There are no angles, it's pretty straight forward if you follow the Adire plans carefully.

I dont really know what trance is, so I cant help there.

[anonymouse]

Airplay - I am also just starting on an Atlas 12 based sub. The other thread referred to above was started by me. We should share notes as we do this. I was initially hoping to build stereo subs, but I could only get one Atlas 12 driver, so I will build one for now, and hopefully do another one later.

I will be building a sonosub, because it looks easier and the finished product can look like a nice piece of furniture without too much effort. I got some 24" sonotube and according to the calculator at http://www.quux.net/roo/diy/sonosub/sonocalc.html (thanks tryrrthg) my tube length will be 21.242" for the same EBS alignment proposed in the 142.5 litre shiva plans. Same port length as the shiva plans. I plan on getting the port and speaker connector from partsexpress. The best link I found for step by step sonosub construction is http://www.io.com/~patman/sunosub3.html He has great pictures. I will deviate from his plans a bit - I intend on using a simple jigsaw for the cuts. I have one of these: http://www.sears.com/sr/javasr/product.do?BV_UseBVCookie=Yes&vertical=TOOL&pid=00917242000 and will use a saw guide such as this http://www.sears.com/sr/javasr/product.do?BV_UseBVCookie=Yes&vertical=TOOL&pid=00926320000 for the circular cuts.
Patman uses a router rather than a saw. I have never used a router, so I think I will go the saw route. I will use a detail sander to round out the edges. The sonotube itself I plan on cutting with a regular manual flat blade saw.

My main concerns at the moment are:
1) Will the 24" sonotube be too wide? I noticed that SVS uses 16". I chose 24" because I did not want a very tall sub. This one will be coffee table height, and if I build 2 subs, I could use them as end tables.
2) I plan to add 3-4 reinforcing beams connecting the top and bottom plates. None of the sonosub designs call for this, but I figure it cannot harm and will make be feel better about the rigidity. I will adjust the tube height to compensate for the beams. Is this a good idea?
3) For finish, I am thinking black felt or velvet for the sonotube and high gloss silver for the ends. I do plan on a baseplate, similar to the SVS look. This black/silver finish should match the RTi10's well. Somewhat concerned as to how well I can get the ends painted.
4) Plan on getting the port and speaker connector from Parts express. Do not quite know how to add a correction factor for the flares on the port to that calculator link I mentioned above
5) I do not intend on adding any polyfill, even though all the sonosub designs I have seen online use polyfill. Should I be thinking about adding some, or at least coating the inside of the tube with undercarriage spray?

Let me know what you learn and what design you are going with.

[tryrrthg]

anonymouse,

everything I've read says you don't need to use braces between the top and bottom plates. Glue and maybe some brad nails are all you really need. I did, however, use threaded rod on mine. My sonosub pics below

http://www.angelfire.com/alt/tryrrthg/DIYsub/sono2.html

You should line the walls of your sub with some polyfill. You don't need a lot in a ported sub but lining the walls is a good idea.

I wouldn't worry too much about the flared ends, they won't take up enough volume to make a noticable difference.

the only thing you might have to worry about with your 24" sonotube is the sub being too short. the end of your port should be one port diameter away from any boundaries in your enclosure.

oh, and if you have access to a router, it would be MUCH easier cutting circles than using a jigsaw...

[Vr3MxStyler2k3]

"The cherry vinyl looks much lighter in the picture than it really is."

All better...

[gatemplin]

Anonymouse,

I'll just add a few things to what Tryrrthg said.

1.Yes 24" sonotube is fine.

2. As try said, threaded rod will be the easiest and work best in this applicaiton

3. Another finish I have heard for sonosubs is automotive headliner material.

4. I would just make the center length of the tube slightly shorter than the calculator says, or use a program like UniBOX which can account for any flares.

5. You should at least line the walls with polyfil, not under carriage liner. I've tried it and it's messy and it smells REALLY bad.

[anonymouse]

From what I have read, polyfill makes the driver think it is working with a bigger enclosure. Will this not mess up all the careful math for the 142.5 litre box? i.e. the driver now thinks it is in a bigger box?

[gatemplin]

Not unless there is a lot of polyfil. Most enclosures for any speakers should be at least lined with polyfil or another material that can absorb high frequencies. That's according to a subwoofer expert friend of mine.

[tryrrthg]

"The cherry vinyl looks much lighter in the picture than it really is."

All better...
Thanks, but the cherry vinyl is actually pretty dark. It's more like a deep red, than an orange'ish color.

http://www.partsexpress.com/images/260-014u.jpg

[Airplay355]

I'd rather make a box sub, even though the sonosub looks easier. I would like to be able to have the BASH amp in the sub and not in a seperate box. I think building a tube sub would complicate this. Plus, I think the tube subs are alittle ugly. I'll look into the Shiva EBS design and see if it's something I feel I can build without making a mess of things :)

[Airplay355]

If I use the EBS plans, do I have to make it a downfiring subwoofer? Those plans say the Shiva has the most excursion with a downfiring sub but I think I like the look of a front firing sub much better, and I'm not using a Shiva so I'm not sure that applies. Any Suggestions?

[gatemplin]

That's fine. Orientation doesn't matter.

[Airplay355]

Can i put the port in the back? Is it better if the port is in the front?

[gatemplin]

As long as the port isnt close to a wall, and has room to breathe, it makes no difference where the port goes, as far as performance is concerned.

Where is the sub going to be in the room relative to the listening positions?

[Airplay355]

In the right corner, behind the right main. However, I could put it in the left corner but that would make it boomy because I have a huge wall unit type thing close to the corner. http://www.polkaudio.com/forums/showthread.php?t=28070&page=2&highlight=lab on the second page of this thread you can see the corners of my room. I will have smaller Lsi7's there instead of the larger JM Labs so there is more room. I shouldn't have problems putting a sub in either corner. You can probably see why I want it in the right and not the left corner lol. The room is only about 15'x12'x8' so this sub should really thump :)

[gatemplin]

Yeah that seems like a good place for the sub.