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Author Topic: the sub project  (Read 3393 times)
Philphine
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« on: May 12, 2012, 12:01:01 pm »

 yeah, like most things i post, who knows when there'll be a progress pic, but i'm pretty happy right now. found some tubes that'll let me work on an idea i've had in my head almost since i started this theater idea



cleaning out my garage and taking some metal over to the part of town where the garbage and recycling places are. i left there and went the opposite way from home for a second errand and saw another recycle place, that recycles plastic. they had a pile of huge pvc tubes out front.

so i stopped to ask about them, and found out they'd sell them, i wanted two, but wasn't sure if i could afford it. he said he'd be willing to weight one and give me the price (i didn't want to take up his time and not buy them but he said he didn't mind).

305lbs! it turned out to be about $100 each, way more than i had, but he dropped the price on the spot to something much more managable. luckily i had the money from the recycling on me which was off his price by a few bucks, but he accepted it and i have my tubes.
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Philphine
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« Reply #1 on: May 12, 2012, 12:25:06 pm »

guess i'm too long winded. i couldn't add any more to the first post



the tubes are 4'10" high, and 32" outer dia. with inch thick walls. i may cut them down to an even 4', but i need to do some calculating and get further into the project first.

the plan is, from the bottom up, the first 1-1.5' will have 6" or so holes all around the bottom. the sub will fire at the ground and these will be the output for the sound. i hope to open it enough that they don't really work like ports or part of how the sub works or shapes the sound.

the next 1-1.5' will be the sub enclosure it's self. been a long time since i've played with car stereo and building boxes so i'm rusty with the calculations, but if i figured them right, 1' of tubing will give me nearly 5cf, 1.5' will give me about 7.3cf. i need to start hunting for subs that can take weather and work with the amount of air i end up with, and make some ported or sealed decisions.

the last foot or so, depending on weather i cut them, will be a planter. i want them to look more or less like big flowerpots. i think i can work out drainage that doesn't affect the enclosure under them, and will make them that much more heavier. part to keep the sub that much more set in place, and as a side bennie it will take more effort to steal. so far it hasn't been a problem with speakers and other things in the yard, but i still have to think in terms of securing things as best i can.

so give me a year or two, maybe i'll have a progress pic by then.
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Tazman101
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« Reply #2 on: May 12, 2012, 02:21:20 pm »

Interesting idea!  Look forward to the updates.  Smiley

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Chaz
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« Reply #3 on: May 12, 2012, 03:09:41 pm »

I would just use marine grade speakers, sub, mids and tweets.
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cdepaola
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« Reply #4 on: May 12, 2012, 06:35:25 pm »

Lots of good info over at AVS and ProSoundWeb on sub construction and specifically tube subs like this.

Great project, have fun and save lots of money for the amps to drive these...
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rich72
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« Reply #5 on: May 12, 2012, 07:29:58 pm »

Very cool, I'm interested to see how this comes out.
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Philphine
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« Reply #6 on: May 15, 2012, 05:17:11 pm »

well,not really progress. just thinking out the idea now that i have the tubes. the idea's been rumbling around in my head all this time, but now i'm seeing what actually needs to be worked out and how to get there.

a minor decision, i don't think i'll cut the tubes down



at first i just had one tube in place for some measuring, but i really don't have a place to keep them so i put both in their planned spots. i don't have room in my garage for them, but i've been reading it's good to paint pvc if it's exposed to the sun permanently. i may paint them even though the building up will scratch up the paint, them just repaint again later.

at 4'10" they're just a few inches shy of the bottom of the screen braces so i thought they'd block the bottom depending on where someone sat, but after moving a chair around it seems like you'd have to want to have your view blocked for it to be a problem, so i'm making my plans with them as is. if i get to the flower pot stage i'll just need low growing plants.


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Philphine
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« Reply #7 on: May 15, 2012, 05:39:47 pm »

and a small bit of construction planning



some 1.5" square tubing. right now it's just a hair larger than the diameter of the tube. i hope to grind them down to a fairly close fit inside, then make legs at the four ends like a table with no top. this will be frame work for the sub inside. the legs will bolt to the sides of the tube. i'll need to actually have the subs and know how much airspace i'll need before i can come up with a lenth for the legs.

whatever material i find to make the top and bottom of the sub enclosure will sit on top of the "x" and bolt to the legs on the bottom. i'm hoping that will be strong enough for the flowerpot section over it.

but that bit of planning is all i can do 'til i can come up with subs, and also the material for the top and bottom of the sub, which looks to be costly in it's own right. looking at a kind of nylon material right now that's pretty spendy, but reading up to see what else i might use that will work for me more affordably.

so except for a bit more minor work and planning (i may go ahead and cut the holes in the bottom), it probaly will be  good while before there's more progress. they're built in my head though, and i think i've got it thought out enough to work (sealing the top and bottom has me thinking, but i have to get to that bridge i guess). unless i get lucky on finding stuff i need the next post could be a while.
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Philphine
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« Reply #8 on: May 29, 2012, 03:59:38 pm »

now i have subs. polk dxi12 dvc, 12".

right off i knew i wanted something big to take advantage of the big tubes i had found. i started looking at 15 and 18" subs, which led me to finding out there are now a number of 21" subs too (like i said, haven't messed with this stuff for a while). didn't take long to give up on it though. i didn't really want a 15", and the 18 and 21" subs didn't come cheap at all, let alone finding some that might take being outside.

*for someone whos able (and maybe a little crazy) i also came across 36" subs, and the place i found my tubes had some bigger tubes one would fit in. just sayin'...*

there was also the fact that subs need so little air space now. if i compromised and went with a 15", not only would i be using only a very short lenth of the tube, i'd need to make walls within the walls of the tube to get down to the airspace i'd need.

so i had to go the other way. i didn't want to put more than one sub in each tube. it just seemed like to much complication for something outdoors, plus having one go bad and trying to figure out which it was, but the best deals and finding the marine grade came with going smaller, so i did some figuring and found i could put three 12" subs on a 30" diameter circle. so i started my hunt again and came across a deal on the polks. they're used returns with a 15day garuantee. gonna try to hook them up just to make sure they make some kind of sound, even if i can't add any real power since no enclosure is ready for them. to get a better deal i got all they had, 7. i figure that gives me a spare also.

4 ohm dvc, so i can hook up three and end up with about 6ohms impedance. i'm hoping that will be ok. i also contacted polk to see how big an enclosure i could get away with putting them in (i guess for advertising purposes they always tout how small a box they can work in, when the opposite was what i need to know for this). so now i can also figure the lenth of the tube i'll need also, about 8.5". so i can make the table with no top metal shape i mentioned earlier.

so now i need the material to make the top and bottom of the enclosure. that may be a stumbling block that holds this up for a pretty good while.
« Last Edit: May 29, 2012, 04:53:41 pm by Philphine » Logged
rich72
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« Reply #9 on: May 29, 2012, 04:36:34 pm »

Very cool, thank you for the update.  It's been a long time since I've built any speakers or even done the calculations, so this is a fun project to see in the works. 

I have 2 old ElectroVoice studio monitors that I need to rebuild someday.  Luckily I still have the original box for one so I can model 2 new boxes off of it, but it's so far down the list of things to do....
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Philphine
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« Reply #10 on: May 29, 2012, 05:00:17 pm »

just realised i should have added this at the beginning. in case someone else is interested in trying the tubes. this is in louisville, ky. i don't know the name of the recycling place or if they always have tubes, but it's over on grade lane, bettween fern valley rd. and the outer loop. i have a pickup and they loaded them on for me.
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Philphine
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« Reply #11 on: July 04, 2012, 12:08:43 pm »

an inch or two further along. the metal framework for the sub enclosure section



8.5" top to botoom, about 3.4cf in a 30" tube. a liitle bigger than whats needed, but i'm hoping speaker displacement and the frame work will pull it back down to just about good.

the fit is pretty good in the tubes. i found out the tubes aren't perfectly round, which will probally make getting the tops just right a little harder, since they need to seal as well as possible to the sides. i'll just have to do some really careful cutting when i get to that point.

i'll need to be careful anyway, since whenever i find some kind of top and bottom material it'll be too costly to waste. haven't been looking too seriously since i'm kinda broke at the second (actually most any second), but i guess that gives me time to look into other materials and plan what i can without it, like i'm pretty sure i'm going to go ahead and cut them down to 4" like i was originaly thinking.

still building...
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Philphine
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« Reply #12 on: November 29, 2012, 09:37:56 am »

has anyone heard of, or know anything about hdpe sheeting?

i've been browsing on ebay off and on for the nylon sheeting and found a dealer who advertised pretty big sheets, but not as big or thick as i think i'll need, so i asked if he had the size i thought i could get away with using (at least 3/4" thick, 31"x31"). the best price he could give me was just over $300 a piece. there's no way i can come up with that, so i thanked him for his time, but he messaged back what i wanted it for. i tried to explain and post a link to here (turns out you can't add a link to an ebay message).

so i don' know how well he understands what i'm trying beyond it's outdoor speakers, but he suggested hdpe sheeting. it's some kind of hard plastic that would be about half the price. still pretty high, but i think i could come up with that eventually. i'm just trying to come up with more info on it, like how well it would cut and drill, how well i could seal it to the pvc tubes, and how it would take being bettween the dirt on top and enclosure under it. so far all i've found is it's a fairly hard palstic like what bottle caps are made of.

so that's where i am on this. i'm thinking i might be able to get away with just getting two sheets of whatever i find. one in each tube to go bettween the planter and the sub, and maybe i can get away with marine grade plywood on the bottom (where the subs would be mounted), since it wouldn't be as exposed to weather.

still trying to work this out...
« Last Edit: November 29, 2012, 09:41:26 am by Philphine » Logged



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