Taking the plung with 2 -18" - first time builder

[Mattk11]

I have made the decision to build my own subs for a couple reasons 1) I have heard and read DIY will give me better performance 2) I want a project. My room is 13' wide, 22' deep and 9' tall. It is completely treated with bass traps in the corners and all walls treated as well. The subs sit behind a perforated screen wall on a stage filled with sand.

My current subs are an MX-5000 and Outlaw stacked on top of one another about 1/3 from the right forner of the room. The front two corners have floor to ceiling bass traps. The bass sounds tight but it is just not enough for this room. I really would like to get flat extension down to 15 Hz. I am good to around 20 right now but it falls off steeply below that. I had graphs from when the room was completed but my laptop that I used for testing has since died.

I am really having difficulty deciding what to do. I have narrowed my driver choice to the SS RL-P18 and would like to make two subs. My amp is a Crown CE4000 which can run mono at 4 ohms, 2800w. I also have an SMS-1.

My biggest problem is size, I only have 16" of depth to play with behind my screen wall. I can go as wide as 36" and 48" tall - one on each side of my center channle speaker or I can stack both subs up to 80" tall on one side the the center channel. The SS web site suggest 19 cu ft vented enclosure for 14 Hz tune. I don't know if this is the ideal size since many of the boxes built on this site a HUGE. I have no idea how long to make the port or where to get started. I have seen some of the software available, but I am worried it would take me more time to learn the software than to build the boxes.

I am also worried that if this sub fires forward, it could ripple the screen since it will be 4" from the front of the woofer. I could angle one side of the box or the top of the box so the woofers fire at a 45 degree angle.

Any thought or ideas?

Thanks
Matt

[Mattk11]

Can't believe I mis-spelled plunge. Sorry.

[Darren]

No problem on the mis-spellings we are all human . Do you have attic or crawl space? Have you considered infinite baffle?

[bonehead848]

for port length there is a program called winisd that will help with that. Just enter the t/s parameters found on the soundsplinter site. Download here
http://www.linearteam.dk/default.aspx?pageid=winisdpro

[tjambro]

Matt,

Your room and setup is not all that different from mine. My room is 14x21x8.5 with a screen wall in front. My sand filled stage is only about 6" deep though. I only had about 19" to work with and I built two huge boxes each with a SS RLp-18. In case you haven't seen my thread, here it is: http://www.hometheatershack.com/foru...llt-begun.html

I'm not sure how loud you listen, but one of these monsters would have been enough for my needs but naturally two couldn't hurt. It looks like you have 18.5" below your screen to work with. If so, the 18's should just about fit or maybe the basket frame will spill over into your screen area. I too did not want my subs directly behind my fabric. Having said that, I have GOM directly in front of the subs and it appears not to move. I just finished my project and don't have the GOM stapled back to my screenwall frame so I cannot guarantee it won't move but so far it looks ok. You could check the exact dimensions of the SS RLp-18 on their website to see if it would fit ok.

As far as software, it seems like most people use WinISD or Unibox. Unibox is an Excel spreadsheet with macros and it is what I used. It's actually fairly easy to use and if you aren't comfortable with your parameters, you can run them by the fine folks in this forum and you WILL get responses.

Good luck and I'm sure you will enjoy your subs! I am still in the early days of owning mine but so far I am amazed at how low these things will go and how good they sound. A couple of people who have experienced mine were equally as amazed also. Unfortunately, my projector is off for repair so I haven't been able to actually watch a movie yet with the subs...hopefully soon!

-Tom A.

[Mattk11]

Thanks to all that have responded. I downloaded a couple of these "free" programs but have to admit that I don't understand them very well. I am really a newbie when it comes to sub building. Also, because my box shape will not be a cube, I am not sure how to plug them in to get a good reading.

My home theater is a "room inside a room" so no there is no way to go IB. I should have planned for it but didn't.

Tom, I did see your sub build and am impressed by what you did. We are dealing with almost the same dimensions, I didn't notice that at first. They really work well in your theater. BTW, your theater looks great too.

I thought about doing my subs the same way you did, but I cannot because of the way the screen is held in place. My screen is a curved aluminum frame that I had fabricated. The mounting tabs extend back behind the screen about 6 inches. The tabs rest on the inside edges of the screen wall frame. To attach the screen in place, I have to climb back behind the screen wall to screw them in. My GOM below the screen is held in place by velcro, so I just undo it and slide up under there.

That leaves me with only one option for my subs, they have to be near the two corners but not too wide since I still need room for my center channel speaker and I need room to crawl under the screen wall to attach it.

Here is the idea I am leaning toward right now. They each can have an internal volume of about 598L not including bracing, driver, port etc. Will that be enough? Also, what size and how long should my port be for a 12 or 14Hz tune? I indicate the diagonal measurement in green because I will have to lift the subs into place on their side and then tip them upright. This should give me the clearance I need and by sloping the front baffle back, I can have clearance to attach the screen and the subs will not be too close the the back of the screen.

Thanks
Matt

[bonehead848]

http://www.the12volt.com/installbay/...TID=74558&PN=1
Check out this guide on using winisd, its tough to figure out at first. As far as your boxes not being cubes, it doesnt matter because all you need is a net volume.