pwmin Posted June 7, 2011 Author Report Share Posted June 7, 2011 That's confusing to look at, lol. Is that while looking into the trunk? Why did you make it trapezoidal at all? Give me a max height up to the strut tower bar, max width to the ski pass, and max depth. Sent from my HTC Awesome using Tapatalk It's just a 2-D representation of the trunk opening where I want to put the box. The strut towers are angled, so that's why The side view is as if you could see through the side of the car into the trunk from the driver side and the front view is looking in from the trunk opening towards the front of the car at the back of the trunk...what I'm assuming would be the front of the box (having the sub face the back of the trunk/car. Max width at the narrowest is only 12 inches, 13 1/2 at the widest part of the strut tower (at the bottom) and max height is 13 3/8". If the back of the box (towards the front of the car) isn't at an angle, there isn't much room there to work with...4 5/8 to 8 5/8 ideally. More confusing now? in order to get a 12 in there I'd have to block a couple inches of the pass-through. I'm assuming you're planning on 3/4" MDF? Quote Link to comment Share on other sites More sharing options...
xtremerevolution Posted June 8, 2011 Report Share Posted June 8, 2011 (edited) How do you feel about a box toward the very rear of the car against the tail lights? What confuses me is that there are two angled areas. Those boxes are not particularly easy to build. You're going to have to go past the RSTB. You should be happy that you can at least clear it, lol. Edited June 8, 2011 by xtremerevolution Quote Link to comment Share on other sites More sharing options...
pwmin Posted June 8, 2011 Author Report Share Posted June 8, 2011 How do you feel about a box toward the very rear of the car against the tail lights? What confuses me is that there are two angled areas. Those boxes are not particularly easy to build. You're going to have to go past the RSTB. You should be happy that you can at least clear it, lol. I'd rather have it towards the front just because for some reason I think it's better that way, although I'm not particularly sure why, lol. However, the truck box is basically like that anway. Guess I might be ok w/ that, but I'd rather go where i measured out. I just arbitrarily wanted it under and behind the STB, but it doesn't matter. I know, I don't want to make a box that way, just measuring everything. Quote Link to comment Share on other sites More sharing options...
xtremerevolution Posted June 8, 2011 Report Share Posted June 8, 2011 I'd rather have it towards the front just because for some reason I think it's better that way, although I'm not particularly sure why, lol. However, the truck box is basically like that anway. Guess I might be ok w/ that, but I'd rather go where i measured out. I just arbitrarily wanted it under and behind the STB, but it doesn't matter. I know, I don't want to make a box that way, just measuring everything. The ideal spot for a sub is firing backwards right against the tail lights. From there, against the tail lights firing toward the trunklid, and the third best spot is up against the back seats firing toward the trunk or up against the back seat firing toward the side. Its an effect called boundary loading, which is another reason why many people downfire home theater subs and car sub where space permits, such as in SUVs. Down firing a shallow mount 10" or 8" sub in a suburban or tahoe is pretty common as it produces excellent results. For you, I think we may have to side fire with a box that sits under the RSTB but extends beyond it a wee bit. I'll model up some boxes for you, hopefully tonight. Quote Link to comment Share on other sites More sharing options...
pwmin Posted June 8, 2011 Author Report Share Posted June 8, 2011 The ideal spot for a sub is firing backwards right against the tail lights. From there, against the tail lights firing toward the trunklid, and the third best spot is up against the back seats firing toward the trunk or up against the back seat firing toward the side. Its an effect called boundary loading, which is another reason why many people downfire home theater subs and car sub where space permits, such as in SUVs. Down firing a shallow mount 10" or 8" sub in a suburban or tahoe is pretty common as it produces excellent results. For you, I think we may have to side fire with a box that sits under the RSTB but extends beyond it a wee bit. I'll model up some boxes for you, hopefully tonight. cool, man, awesome. No rush. Haven't decided if I'm just going to order the amp or both, but if I do I won't wait too long to order the sub. Quote Link to comment Share on other sites More sharing options...
xtremerevolution Posted June 8, 2011 Report Share Posted June 8, 2011 (edited) cool, man, awesome. No rush. Haven't decided if I'm just going to order the amp or both, but if I do I won't wait too long to order the sub. Sounds good! Let me know what you end up doing and we can start making you a badass system. I don't mean to throw a curveball at you, but alpine's new 8" Type-R subwoofer is getting mad raving reviews over on DIYMA and is apparently one amazing hell of a subwoofer. http://www.amazon.com/Alpine-SWR-823D-quot-Type-Subwoofer/dp/B004X0V2UA If you don't listen to much rap and you don't need a LOT of output, this would also do very nicely. Most people don't run 8" subs, but then again most people haven't the slightest clue about SQ and system integration. The advantage is you can cross these very high, as in, 125hz+ high, in order to complement what your front door speakers and 6x9's can't hit quite as loudly. They would integrate extremely well. Part of the biggest problem with ported boxes is that they will hit low bass notes very loudly, they will suck at higher bass frequencies (90-150hz), and it will leave a large gap for your components and coaxials to fill, which, lets face it, most people don't have the hardware necessary. My 6.5 front components take 125W RMS each and have a gigantic magnet, a woven glass fiber cone, and hit those higher bass notes the way they should be heard. Granted, so would the 10", but if you're extremely tight on space, this is something to consider. Edited June 8, 2011 by xtremerevolution Quote Link to comment Share on other sites More sharing options...
pwmin Posted June 8, 2011 Author Report Share Posted June 8, 2011 too late to consider since I ordered the sub and amp this morning it'll work just fine. If the box needs to take up a little more room than I had hoped, it's fine. Quote Link to comment Share on other sites More sharing options...
xtremerevolution Posted June 8, 2011 Report Share Posted June 8, 2011 too late to consider since I ordered the sub and amp this morning it'll work just fine. If the box needs to take up a little more room than I had hoped, it's fine. Awesome. I'll start modeling up a box then when I get a chance. Quote Link to comment Share on other sites More sharing options...
pwmin Posted June 8, 2011 Author Report Share Posted June 8, 2011 sweet...really appreciate it Quote Link to comment Share on other sites More sharing options...
xtremerevolution Posted June 9, 2011 Report Share Posted June 9, 2011 (edited) Gentlemen, here's how you model a proper subwoofer box. To start, I modeled cabin gain. I modeled a 15db gain at 20hz based on the curve of a typical room pressurization graph, using a 11ft specification and a 30% pressurization loss (vents, trunk seal leaks, etc.). 15db gain at 20hz is a pretty good depiction of what people experience in a car. Your mileage will very a bit but this is a pretty good estimate. Next is your circuit simulator and your T/S parameters. The circuit was added to simulate your high pass and low pass crossovers. Normally we don't add a high pass (subsonic) filter with a sealed box, but in our particular case, setting it at 20hz allowed us to control excursion at lower frequencies and increase the box size to get a more linear frequency response. These are set as 2nd order butterworth circuits, which have a 12db per octave slope. This is because your amplifier's high and low pass are also 12db per octave, so this gives us a very accurate depiction of our final frequency response. The low pass filter is set to 150hz, which is the highest you can set on the amp you're buying. This will complement your midbass and give you a very nice, punchy, sound, such as that of a kick drum, which occurs at around 100hz, without the distortion some subs can have when played too high. This particular sub doesn't sound too great above 250hz, so a low pass filter is necessary. Both circuit simulations are applied. I forgot to change the amp name, but it doesn't affect anything. Next is your power usage at a given frequency. This doesn't do a whole lot but give you some interesting information. Next is the big kicker; cone excursion. I designed this box in such a way so that cone excursion would be controlled at all applicable frequencies. We don't want you bottoming out this sub. You'll notice there's a slight rise at 30hz above xmax. I described xmax in either this thread or the other one in saying that xmax is the maximum point a cone can travel before the coil goes outside the magnetic field. This can usually be exceeded by 10%, so we're ok there. You won't be anywhere close to exceeding xlim, or the maximum limit of excursion before you bottom out. That is of course, assuming you build a well sealed box. I can walk you through that later. One thing to note, you have some leeway with the high pass filter. Playing around with it, you can set it as low as 17hz without too big of an effect on excursion. The following is a raw SPL chart for the driver alone in free air. This is what everyone else models whenever they build a box. Its does nobody any good. Its more representative of what you'd experience in a home environment. Fortunately, the software I use allows me to import the cabin gain graph and apply it to the raw frequency response, in addition to the high and low pass circuits. This is our end result: The black line is your frequency response after all of the values have been applied. You'll notice a linear frequency response from 30hz to 100hz at 110db SPL, with a -2db loss at 20hz. -2db is nearly inaudible. The rest of the lines, well, follow the legend at the bottom. Your box will be 12 liters, or .42 cubic feet. We can work on the exact box dimensions and cuts later. Edited June 9, 2011 by xtremerevolution Quote Link to comment Share on other sites More sharing options...
pwmin Posted June 10, 2011 Author Report Share Posted June 10, 2011 awesome. I'll have to take some more time tomorrow to read it again better. Quote Link to comment Share on other sites More sharing options...
pwmin Posted June 13, 2011 Author Report Share Posted June 13, 2011 got the sub on sunday...just waiting for the amp now. I have no idea what's going on with it. I emailed boston and no reply yet, so I'm going to call them today and see WTF is up. Sub looks great. Quote Link to comment Share on other sites More sharing options...
xtremerevolution Posted June 13, 2011 Report Share Posted June 13, 2011 got the sub on sunday...just waiting for the amp now. I have no idea what's going on with it. I emailed boston and no reply yet, so I'm going to call them today and see WTF is up. Sub looks great. They took a little while to ship out my amps, but eventually they came. Give it another few days. Partsexpress usually ships very quickly anyway. Quote Link to comment Share on other sites More sharing options...
pwmin Posted June 13, 2011 Author Report Share Posted June 13, 2011 They took a little while to ship out my amps, but eventually they came. Give it another few days. Partsexpress usually ships very quickly anyway. yeah, parts express was awesome and they even shipped on a saturday. I paid for the upgraded shipping, but it was only $6 so I figured wth. I called Boston and the guy said it's supposed to arrive via FedEx tomorrow. For some reason, I can't track by reference on FedEx using the order number, which has always worked in the past for me. I at least want to get the amp hooked up to my RT12 so I have something until I get the box built. I was going to pick up a 4x4 3/4 mdf sheet when i was at lowe's earlier, but all they have are the full sheets. I think depot has them, so I'll look there later. I just don't want to deal with moving around a full sheet by myself...once was enough. Don't know if I'll have time to build the box this week, anyway. Quote Link to comment Share on other sites More sharing options...
xtremerevolution Posted June 13, 2011 Report Share Posted June 13, 2011 yeah, parts express was awesome and they even shipped on a saturday. I paid for the upgraded shipping, but it was only $6 so I figured wth. I called Boston and the guy said it's supposed to arrive via FedEx tomorrow. For some reason, I can't track by reference on FedEx using the order number, which has always worked in the past for me. I at least want to get the amp hooked up to my RT12 so I have something until I get the box built. I was going to pick up a 4x4 3/4 mdf sheet when i was at lowe's earlier, but all they have are the full sheets. I think depot has them, so I'll look there later. I just don't want to deal with moving around a full sheet by myself...once was enough. Don't know if I'll have time to build the box this week, anyway. Out where I live, they can make the cuts for you, and at least at my location, the cuts are dead accurate. I still have to figure out what dimensions you'll be using. You have any wood clamps? If not, do you have a harbor freight nearby? Quote Link to comment Share on other sites More sharing options...
pwmin Posted June 13, 2011 Author Report Share Posted June 13, 2011 Ya, I should probably just have them cut it and pay the extra. HD has 2x4 sheets, but IDK if I can use them or not. I just don't have any room to store a bunch of MDF right now. I have two of the IRWIN clamps, but there is a HF nearby if I need to get some more cheap ones. I have a brad nailer, too. I was going to use that instead of screwing it like I usually do. You just use regular Elmer's wood glue? I tried using gorilla glue before and it was a PIA. Quote Link to comment Share on other sites More sharing options...
xtremerevolution Posted June 14, 2011 Report Share Posted June 14, 2011 Ya, I should probably just have them cut it and pay the extra. HD has 2x4 sheets, but IDK if I can use them or not. I just don't have any room to store a bunch of MDF right now. I have two of the IRWIN clamps, but there is a HF nearby if I need to get some more cheap ones. I have a brad nailer, too. I was going to use that instead of screwing it like I usually do. You just use regular Elmer's wood glue? I tried using gorilla glue before and it was a PIA. Titebond II wood glue from home depot. Use that and I guarantee you that the wood bond will never break. In fact, I will pay anyone here $20 if they can glue two MDF boards together at a 90 degree angle with Titebond II, clamp the down and let them dry overnight, and break them apart. You won't be able to. The MDF will fail before the wood glue does. Brad nails are fine. I personally just use clamps and no nails or screws of any kind, but I also build speakers and patching and sanding holes is more of a pain in the ass than using extra clamps. Besides, they're only $5 a clamp. I think I have 20, lol. Quote Link to comment Share on other sites More sharing options...
Addicted2bass Posted June 14, 2011 Report Share Posted June 14, 2011 Video or it didn't happen. 6x9's are very obviously in the range of damage from trunk pressures. AS for rearview mirrors falling off, I REALLY want to see this. I can yank on mine with all my might and it won't come off. A sub in the trunk isn't going to change that. Its higher frequency induced vibrations that cause the most problems. I've had my rearview mirror fall off several times from the bass and im only running around 700w to 2 12s. Quote Link to comment Share on other sites More sharing options...
pwmin Posted June 14, 2011 Author Report Share Posted June 14, 2011 Titebond II wood glue from home depot. Use that and I guarantee you that the wood bond will never break. In fact, I will pay anyone here $20 if they can glue two MDF boards together at a 90 degree angle with Titebond II, clamp the down and let them dry overnight, and break them apart. You won't be able to. The MDF will fail before the wood glue does. Brad nails are fine. I personally just use clamps and no nails or screws of any kind, but I also build speakers and patching and sanding holes is more of a pain in the ass than using extra clamps. Besides, they're only $5 a clamp. I think I have 20, lol. damn FedEx, why do you have to deliver signature-required things @ 1120 am? Some people work, lol. Looks like I'll have to have them hold it and wait until tomorrow to pick it up. Oh, well, I had other things I needed to get done tonight that are more important, I suppose. I'd like to start figuring out the box, but I'm not going to rush you. I'd like to know if I can get away with using 2x4 sheets. I'll get the titebond...don't think I have enough Elmer's to do the whole thing, anyway. I'll just use brads so I don't have to get more clamps. I thought about fiberglassing over the box and painting it, but I think I'm just going to carpet it. I can't wait to hear these bad boys running. Then, of course I'll probably need new highs, lol. Hopefully it'll sound okay until I can afford some 6 1/2" components for the front (and another amp) and I'll just yank the 6x9s out. Do you know how easy it is to modify the fronts to fit bigger than 5 1/4"? Can't be much different than my GP was. I have a sort-of off-topic question. Do you have any experience with the Perfect VQ subs? I had some a while back and they kept blowing on me. Quote Link to comment Share on other sites More sharing options...
xtremerevolution Posted June 14, 2011 Report Share Posted June 14, 2011 damn FedEx, why do you have to deliver signature-required things @ 1120 am? Some people work, lol. Looks like I'll have to have them hold it and wait until tomorrow to pick it up. Oh, well, I had other things I needed to get done tonight that are more important, I suppose. I'd like to start figuring out the box, but I'm not going to rush you. I'd like to know if I can get away with using 2x4 sheets. I'll get the titebond...don't think I have enough Elmer's to do the whole thing, anyway. I'll just use brads so I don't have to get more clamps. I thought about fiberglassing over the box and painting it, but I think I'm just going to carpet it. I can't wait to hear these bad boys running. Then, of course I'll probably need new highs, lol. Hopefully it'll sound okay until I can afford some 6 1/2" components for the front (and another amp) and I'll just yank the 6x9s out. Do you know how easy it is to modify the fronts to fit bigger than 5 1/4"? Can't be much different than my GP was. I have a sort-of off-topic question. Do you have any experience with the Perfect VQ subs? I had some a while back and they kept blowing on me. Haven't had any experience with those subs. Brads will be fine. What you will want to do though is brush on a 60/40 mixture of wood glue and water over the MDF once its done. The MDF will absorb the mixture, and it will harden quickly, creating a very hard eggshell type surface that makes the box a long stronger and makes it virtually waterproof. It will resist molding or absorbing water if your trunk ever develops a leak. You can glue a carpet over that. These should integrate very well with the rest of your system, as the frequency response will be quite linear and not boomy or peaky. As for bigger comps, I'll be installing some massive (pun intended) Massive Audio RK6 components soon. These each take a sustained 125W RMS. The magnet is just a hair smaller than the mounting cutout. If I can get these to fit in the doors of my Regal, you can pretty much get any 6.5 driver to fit. Quote Link to comment Share on other sites More sharing options...
pwmin Posted June 14, 2011 Author Report Share Posted June 14, 2011 I'll have to try that w/ the glue/water. How much those bad boys run? Quote Link to comment Share on other sites More sharing options...
white4d96 Posted June 14, 2011 Report Share Posted June 14, 2011 I've never heard the glue/water trick, but I have heard a similar one using fiberglass resin, laid on thick and then sanded down. Quote Link to comment Share on other sites More sharing options...
xtremerevolution Posted June 14, 2011 Report Share Posted June 14, 2011 I'll have to try that w/ the glue/water. How much those bad boys run? I paid $200 for them in a sale on diyma.com. I've never heard the glue/water trick, but I have heard a similar one using fiberglass resin, laid on thick and then sanded down. I prefer the wood glue and water to fiberglass resin. Wood glue and water is actually what the home theater speaker builders use before they prime the MDF, because the MDF will otherwise keep absorbing the primer and give you a splotchy finish. Here's why I prefer the wood glue and water: safer, no toxic fumes cheaper: you already have the wood glue if you're building a sub box cleaner: its much easier to clean up after wood glue than after fiberglass resin easier: goes on with a brush that you can actually clean afterward. One less thing to shop for All that and its just as effective. Sounds like a no-brainer to me. Quote Link to comment Share on other sites More sharing options...
white4d96 Posted June 14, 2011 Report Share Posted June 14, 2011 I'll have to try this! Quote Link to comment Share on other sites More sharing options...
xtremerevolution Posted June 15, 2011 Report Share Posted June 15, 2011 I'll have to try this! You'll be genuinely surprised. When it all dries up, it will be hard as a rock. Quote Link to comment Share on other sites More sharing options...
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