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Discussion Starter #1
As a Newbie (this is my first post), I have come here for some advice. I have been researching how to build my home theater on this and many other sites for over a month now (Countless hours). It is amazing how much knowledge you must have to build a speaker. Anyways, I purchased a used Adire Tempest Classic 15" sub off a fellow member and a Parts Express 200 watt plate amp to build my sub. I have finally decided to build a TV Stand/Subwoofer, although my TV hangs on the wall. Ive included a design that I would like to build with the maximum size available. I was wondering if one of you professional builders could look at it and tell me a few things. I need to know if the box is too big or too small for the sub. Also what size vent/port I would need for this sub taking into account of the displacement and any structural supports. I know it wont be exact because you dont know how many supports Ill be using, but I think if we can take a rough estimate we will be close. This is my first build in home audio, although I have built many car audio systems. I have downloaded all the software needed to do this, but it is a huge task to try and learn it all so quik. Over time I will be learning all this, but for my first build, I just want to get started.

I am not afraid of hard criticism and actually appreciate it, as this is how I will learn. Thank you in advance all that help me, as Im really excited to start my first home subwoofer.

 

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The rules are the same in HT as in car audio - the target tuning is the only thing that changes. The reason for this is in the small cabin of a car you can get a lot of "room gain" (a boost to the low end) which you don't get nearly as much in a HT. So HT subs need to make a bit more of their own low end.

For tuning I recommend googling "Unibox" and/or "WinISD". These are free programs that are pretty easy to use that will help you find a good tuning and box size for your driver.
 

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Discussion Starter #3
I was no pro at car audio either. I just built a lot of sealed boxes to the manufactures specs and custom fit them into a car. I have never used any programs to figure out anything. I dont even know what all the specs mean. I have dabbed a bit with the programs you mentioned, but they dont seem that easy to me. Lets remember I am very new to this and consider myself a retard when it comes to this, but I am very willing to learn and have a lot of ideas that I want to try. So it looks like I have found a new, expensive hobby. I will tinker the programs again today as I do need to learn this stuff.
 

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The fact that you've built some things in the past and have enough technical knowledge to log onto this site shows you have the potential to learn the basics of sub design. Once you do a bit of background reading and play with the progams a bit it rapidly stops being such a mystery. I'd start by reading the wikipedia entry for Thiele Small parameters. After you have read that try putting the T-S parameters for your driver into one of those aforementioned programs and play around with box size and tuning and pay attention to how both affect the frequency response (FR) and excursion graphs.

By spending a few hours doing this it will be much easier to understand the advice folks on this forum give to you with regards to your project and you'll be more savvy about how to ask the right questions. Also, I'm sure folks here would be happy to answer any questions you might have in your learning process.
 

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Will the shelves on the right hand side go the whole depth of the cabinet, and will the sides have a lip on top and front as shown in the pic? The bottom of the sub cabinet should be 4 inches off the floor instead of the 3 inches shown. If you could figure out the internal volume of the sub cabinet it would help a lot.
 

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Will the shelves on the right hand side go the whole depth of the cabinet, and will the sides have a lip on top and front as shown in the pic? The bottom of the sub cabinet should be 4 inches off the floor instead of the 3 inches shown. If you could figure out the internal volume of the sub cabinet it would help a lot.
If they go the whole length you may want to think about making a seperate matching stand for the electroncs. Subs vibrate and electronics don't like to be vibrated.
 

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Discussion Starter #8
I read the Thiele/Small article and understood about 4 words. No really, I did read it, but will have to read it a few times to understand each parameter and its use. As far as the shelves on the unit, they do go all the way back. I thought about the vibration, but then thought that this unit will weigh a ton. Do you still think it would vibrate weighing as much as it will? I dont know if there will be a lip on the front or not yet. Will this make a difference? I dont know which amp it is yet. It will arrive today. I bought it used. Thanks for the comments, keep em comming.
 

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With a lot of bracing vibrations can be minimized. You also have the option of isolating the electronics with some kind of vibration absorption pads or feet. The lip on the top and front and back all make a difference because it will subtract from the internal size of the sub cabinet. It's up to you. Let us know what you're going to do so we can figure out the internal volume so modeling of the sub can be done.
 

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Discussion Starter #10 (Edited)
Lets just go with the internal space it has now, just a square encloser. You can leave the lip or lose it, whatever works better. If you need to make it smaller you can. Lets figure in the fact that it will be made of 3/4" MDF and a reasonable amount of bracing. I will need some extra 2X4's along the top and bottom to prevent sagging over time. If we make it just a square box and use those measurements, Ill make it look good later by adding some trim pieces and so forth. Do all the dimensions show OK in the picture? Also tune it to what ever you think best for that sub and use in a home theater. My room is approx 15' X 20' with vaulted ceilings and hardwood floors. I sure appreciate all your help.
 

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As drawn with a one inch lip on three sides and 4 inches off the floor instead of 3 inches, the internal volume would be 12.5 cu.ft. with a 1.5 inch bottom baffle. Subtract displacement for the sub ports and bracing would give a net volume of 11 cu.ft. Tuned to 17 hz with two 4 inch flared ports each being 18.25 inches long will give you 107db at 20 hz with 200 watts input power, plus room gain. This is assuming the plate amp has a subsonic filter at 18 hz. With this set up the sub could handle 350 watts without exceeding Xmax and give you another 3 db, if you should decide on a bigger amp in the future.

tempest.JPG

Bracing is going to have to involve a little more then 2x4's, perferably "window pane" type used front to back and side to side to make the cabinet as vibration free as possible.
 

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Discussion Starter #12
Thank you so much. This is exactly what I wanted to hear. As for the window bracing, yes. I was going to do that from front to back, but so it doesnt sag width wise, I was going to use some 2 X 4's across the 68" length. Is this alright to do? I figured something that heavy, being supported only by each side, would sag in the middle after time. Again, thank you so much for the help.
 

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Three braces front to back spaced evenly across the width would be enough. As long as the frame, center and horizontal support are 2 inches you should be fine.

Side view of brace.
brace.JPG

The braces should also be connected together in the opposite direction. Another window pane brace without the vertical or horizontal part would be ideal. (just a square).

Top view of sub looking down at how the bracing connects.
brace1.JPG

There won't be a sag issue with this kind of bracing.
 

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Discussion Starter #14
OK Thanks! Ill do it that way. I will post the project as it goes along, but no laughing. It is my first. I will learn all I need to know within the next few months as this is my new hobby that I have decided to take on. Next is a 6 1/2" sub enclosure that Ill make all by myself for learning purposes. Then Im going to build my mains, which I will probably refer to you guys about. So, back to going thru all the threads and being a sponge. Again....Thank you guys very much. Hopefully, someday, Ill be able to help someone else with their setup. Ill keep you all posted with the build.
 

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Discussion Starter #15
One last thing. Do you know if there is a problem with this speaker sagging over time being downfired. I read that only some speakers should be up/down fired, as gravity seems to always be extruding the sub.
 

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Discussion Starter #17
Well the starting has begun. At least getting the last of the tools needed. I also picked up some carbon fibre to make some accents on the box.

DeWalt Mitre Saw


Makita Table Saw


Skill Router


Some carbon


Im going to start a new thread when the work begins. First I need to prep the garage (Clean). Everything is scattered and it makes a job so much easier when all your tools are in the right place and you have plenty of room to work with. The weather should start to be cooling off here soon ( under triple digits ) so keep your eyes open for the new thread, but remember...Its my first build.
 

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Discussion Starter #19
OK, Im back and have now started the project. Being a newbie at this, things haven't turned out perfect. Anyways before I continue on the encloser, I need someone to tell me the length of port I will need. The original plans are slightly different than what I have built The new internal dimensions are 19 1/4" X 46 1/2" X 24 1/2" This doesn't include the displacement of the sub or the bracing.

If Mike P is out there, can you help me out again with the new dimensions. Ive included some pictures of the box at its current state, but am now at the porting part of the build and cant continue with the previous porting lengths because volume is different.

Also, the original amp I was going to use may be replaced by a different one that I purchased. I don't know what kind it is, but it states that it is 450 watts as opposed to the original one that I was going to use at 200 watts. Ive posted pictures of the two amps in hopes of maybe someone telling me which one is better. I know that just because it says it more watts doesn't mean it is better and I thought I would check with everyone here. Like I said, I don't know the brand of the amp, as it doesn't say on it anywhere.

I am a newbie and this is my first build and so far it is coming along OK. I am taking pictures as I go. I am not going to post a step by step until it is completely done and I can hear it first. Because it might turn out to be a big, heavy turd.

Again....Thanks for all the help (Especially Mike P.) as I couldn't have even thought of building my own sub without your help.

Stage 1 of the box


Stage 2 of the box


This is the 450 watt amp. But I dont know the brand


The back of the 450 watt amp


This is the 200 watt amp (which is the same size and weight of the 450 watt amp)


Thank for your help as I anxiously await your answers for the new port length and which amp to run.:scratch:
 

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Good to see your sub coming along. You'll need two 4 inch flared ports 17.25 inches long each. Go with the 450 watt amp. It won't be working as hard as the 250 watt one, which would be maxed out for your setup. The 450 watt amp also has variable phase adjustment, which is a plus. It would be nice to find out if the bigger amp has a subsonic filter and if so, at what frequency. Where did you get it from?
 
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