Paducah Home Theater Posted November 11, 2015 Author Share Posted November 11, 2015 (edited) I've never seen a warped piece of baltic birch. I have some at home. While researching a method of straightening it, I found something that actually works. Wood warps when one side dries out more than the other. The dry side shrinks slightly in relation to the other creating the typical warped arc. I read that if you place the concave side down in the grass on a sunny day, it will straighten it. The sun dries out the top, shrinking it and the moisture from the grass is pulled into the concave side facing down expanding it. It works surprisingly well. Yes this works nicely for 2x4's and hardwood. It doesn't take as long as you'd think. Maybe I'm spoiled too, my local supplier is very picky about what he gives to customers. If he gets a bad piece he'll send it back. I had to wait an extra week because he sent five pieces back on my subs. When I got it I used it pretty quickly. Edited November 11, 2015 by MetropolisLakeOutfitters Quote Link to comment Share on other sites More sharing options...
derrickdj1 Posted November 11, 2015 Share Posted November 11, 2015 (edited) I have the 4 cu ft MDF boxes and they don't move at all. I don't have feet on them or any of the other subs since they are on 4 in. risers. Two large ported subs should work well with your existing subs for that size room, 2700 ft3. Edited November 11, 2015 by derrickdj1 Quote Link to comment Share on other sites More sharing options...
jason str Posted November 11, 2015 Share Posted November 11, 2015 Baltic Birch plywood warps just like any other type, just straighten it out with your work as you go along. Quote Link to comment Share on other sites More sharing options...
Paducah Home Theater Posted November 12, 2015 Author Share Posted November 12, 2015 Oh my. 3 Quote Link to comment Share on other sites More sharing options...
CECAA850 Posted November 12, 2015 Share Posted November 12, 2015 Beautiful wood work! Quote Link to comment Share on other sites More sharing options...
Wardsweb Posted November 12, 2015 Share Posted November 12, 2015 Beautiful wood work! +1 Oh yea! Quote Link to comment Share on other sites More sharing options...
jason str Posted November 12, 2015 Share Posted November 12, 2015 Awful lot of work for a port. Does look nice though. Quote Link to comment Share on other sites More sharing options...
Quiet_Hollow Posted November 12, 2015 Share Posted November 12, 2015 Value added. Quote Link to comment Share on other sites More sharing options...
Paducah Home Theater Posted November 12, 2015 Author Share Posted November 12, 2015 With the setup I have now, I have lots of room gain around 40 hz for whatever reason. Well I was close. 37.5 hz, big fat boost. Neat little app. http://amroc.andymel.eu/ Quote Link to comment Share on other sites More sharing options...
Paducah Home Theater Posted November 13, 2015 Author Share Posted November 13, 2015 (edited) There's quite a difference between your garden variety MDF and cabinet grade as well. A specialty wood shop locally keeps double refined MDF in stock, I'm assuming this is what you're talking about. He claims it's stronger than the stuff at Lowes and the edges are much easier to finish. I might try that next week. It's $54 a sheet for 4x8x3/4 so hopefully you're gaining something there, normal MDF is more like $33. Forum chatter says it's hard on tools, not sure if that's an issue. Edited November 13, 2015 by MetropolisLakeOutfitters Quote Link to comment Share on other sites More sharing options...
CECAA850 Posted November 13, 2015 Share Posted November 13, 2015 There's a big difference when working the two different types from how well it holds a screw to the way you can machine it with a router. Quote Link to comment Share on other sites More sharing options...
derrickdj1 Posted November 14, 2015 Share Posted November 14, 2015 (edited) It's $54 a sheet for 4x8x3/4 so hopefully you're gaining something there, normal MDF is more like $33. Forum chatter says it's hard on tools, not sure if that's an issue. I used the regular MDF from Homedepot. The strength seems good and no problems finishing the edges. This type of MDF is my only experience so, I wonder if I would find the $54 MDF easier to work with. I only use a couple of screws and the MDF held them without a problem. It sands nicely for edge and corner work. Edited November 15, 2015 by derrickdj1 Quote Link to comment Share on other sites More sharing options...
Paducah Home Theater Posted November 16, 2015 Author Share Posted November 16, 2015 (edited) Wish there was one resource with all the rules for ports: 1. prevent loading issues by not having the back of the port face the driver. 2. keep the port close enough to the driver as to not have issues with the frequency in question, and I forget how to calculate this. 3. keep the port's side and back clearance at least the size of the port away 4. slotted ports need to be at least a 1:8 ratio 5. don't get lazy on the bracing (but there's a hole in the box!) because at the tuning frequency the internal pressures are nearly twice that of a sealed box due to port backpressure. 6. for the cleanest sound, but is likely hard to do on subs, face ports away from the listeners so that artifacts coming from inside the box aren't directed at their ears through the port but are instead dissipated What else is there? Pretty sure there's more. Edited November 16, 2015 by MetropolisLakeOutfitters Quote Link to comment Share on other sites More sharing options...
derrickdj1 Posted November 16, 2015 Share Posted November 16, 2015 (edited) Follow a good design and you won't have to worry about any of those things. There are lots of good designs out there for free! Metro, it is time to get off the fence and get to makin' some subs, lol. Heck, I can sit a glass of water or your favorite adult beverage on my subs and play a movie at reference without spilling a drop or the glass bouncing off the sub. This is with the cheap MDF and not as much bracing compared to most of the builds that I have seen for similar subs. It is were the braces are located that matter. The downside of my system is that for speakers, avr/amp and subs, there are no major gains to be made trading out speakers, amps/avr or subs anymore at this point. Edited November 16, 2015 by derrickdj1 Quote Link to comment Share on other sites More sharing options...
CECAA850 Posted November 16, 2015 Share Posted November 16, 2015 (edited) it is time to get off the fence and get to makin' some subs, lol. THIS ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Edited November 16, 2015 by CECAA850 Quote Link to comment Share on other sites More sharing options...
Paducah Home Theater Posted November 16, 2015 Author Share Posted November 16, 2015 (edited) Follow a good design and you won't have to worry about any of those things. Where's the fun in that? I like learning about the science as much or more than listening to it. That's why I geek out with surge protectors. Metro, it is time to get off the fence and get to makin' some subs, lol. I got all next week off just for this. It's happening then. Got my wood source lined out, picking up a table saw, already got everything else, drew out my cut list, it's all good. Heck, I can sit a glass of water or your favorite adult beverage on my subs and play a movie at reference without spilling a drop or the glass bouncing off the sub. I've been playing with mine and I think a big issue is my carpet, I have really thick carpet and I think it's letting the entire box go back and forth. My top vibrates but in reality I think the entire box reciprocates back and forth due to nothing holding the bottom of it down. It's doing this even at low volumes where there's no way that 13 ply baltic birch is being bent. I don't think it's the weight either, these things weigh 130 pounds each. If it were the box flexing, the top would move up and down, not back and forth. I'll probably have to use some long spikes. Edited November 16, 2015 by MetropolisLakeOutfitters Quote Link to comment Share on other sites More sharing options...
Paducah Home Theater Posted November 16, 2015 Author Share Posted November 16, 2015 (edited) Also been playing around with some scrap granite. That makes me more nervous than anything, I only got one shot to cut this slab. Cut it wrong and boom, $1,200 mistake. Interestingly though, the glare off of a test piece I've got is nearly totally dead compared to the glare coming off my matte sub boxes, even though the granite is polished and glossy. Makes zero sense to me. The glossy granite is actually killing the glare way more than matte paint. Totally opposite of what I've been afraid of. I've been trying to keep the granite shallow trying to minimize the glare off the screen in theory but in reality apparently it makes no difference. Edited November 16, 2015 by MetropolisLakeOutfitters Quote Link to comment Share on other sites More sharing options...
derrickdj1 Posted November 16, 2015 Share Posted November 16, 2015 It should be a fun build Metro. We like watching these projects!!! 1 Quote Link to comment Share on other sites More sharing options...
Paducah Home Theater Posted November 19, 2015 Author Share Posted November 19, 2015 http://aespeakers.com/shop/td/td18h/ Yeah boy. Stupid high efficiency, stupid low inductance, 50 mm cone travel. These have been used for big fat mains but I don't see why they couldn't be used for ht subs. Seems like the best of both worlds, cross between pro audio and ht subs. Quote Link to comment Share on other sites More sharing options...
derrickdj1 Posted November 19, 2015 Share Posted November 19, 2015 Xmax of 14 and Xmech of 25. The UM 18 and SI HT have a higher Xmax and Xmech. You are looking for mid bass slam, consider a couple of mid bass modules. Quote Link to comment Share on other sites More sharing options...
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