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Silver Member Username: Boston_splHighland, CA United States Post Number: 149 Registered: Nov-08 | Alright, here it is. I have a Kicker CompVX 15" (dual 2ohm) sub, (I know, Kicker sux balls, I agree, but I bought this sub like 3yrs ago, B4 I knew better. Plus, I got it for $149, new, from an authorized dealer). Anyway, it's still brand new in the box & I'm finally ready to build an enclosure for it to replace my Orion P2 12" that I'm currently using. (BTW, it'll be going in a '97 Cadillac DeVille & it's being powered by a Crossfire VR1000D (if it matters). According to the owner's manual, ideally, the proper ported enclosure is; 5cu.ft. with a slotted port tuned to 29Hz. My question is, does this sound right? I mean, I know Kicker says it is, but they also say that I can put it in a 1.8cu.ft. sealed box & it'll perform just fine. Now I'm no expert, but I don't know if a small sealed enclosure is a good recommendation for a 1,000w (supposedly) 15" sub. I'm thinking that the volume seems a bit large and the tuning frequency seems a bit low (though I could be wrong). So, any advice on enclosure size and tuning frequency would be greatly appreciated. Also, space isn't much of an issue, as I have a large trunk. Oh, and I'm going for SPL (Obviously. Especially with Kicker & a large ported box, I don't expect great SQ, lol). Thanks again guys. |
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Silver Member Username: Simple_smithLapeer, Michigan United States Post Number: 370 Registered: Dec-08 | 15" subs generally are about 3-5cu.ft. and most people turn kicker subs to ~35hz |
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Platinum Member Username: GlasswolfColumbia, SC USA Post Number: 12716 Registered: Dec-03 | I responded to this in the Speakers forum. |
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Silver Member Username: Boston_splHighland, CA United States Post Number: 150 Registered: Nov-08 | Thanks Glass, I read your response in "speakers". Very helpful. Now I'm thinking of maybe going like, 4cu.ft. @ 34Hz but I'm curious as to whether or not going larger, like closer to 5cu.ft. would yield any noticeable SPL increase. Also, if I do go that route, should I then tune to like around 32Hz? (BTW, despite what Kicker claims, I've never heard of "gaining" more dB's from a low tuning (i.e. 29Hz)). But anyway, since my goal is pretty much straight SPL (to the ear, not necessarily metered. I don't want to tune up into the 50-60Hz range, like I'm burping, lol), again, I wonder if the 1cu.ft. increase would result in a noticeably louder setup. Also, I'm not a fan of the slim & skinny port look so any recommendations (i.e. dimensions & tuning + box vol.) on a larger "fatter" port (preferably in the low 30Hz range) would be great? (Kicker recommends 3" wide x 15.5" tall, 29Hz. A bit slim for my taste) I'm not set on any one design right now (except on going ported) so I'm totally open to suggestions. Thanks again! |
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Platinum Member Username: GlasswolfColumbia, SC USA Post Number: 12725 Registered: Dec-03 | well a larger box will yield more SPL, but it's a trade off as always. a smaller (within spec) enclosure will be tighter and more controlled. better detail. Smaller is snappier. bigger is boomier. the idea behind more SPL at a lower tunign frequency is based on the speaker's impedance curve as you get gloser to the Fs of the driver. At the driver's Fs, the impedance drops, causing the speaker to get more power/be more efficient. That said however, you also have to accound for cabin gain, and the transfer function of most vehicle cabins is in the 55-65Hz range, if SPL is your only goal anyway. Personally I'm happy with boxes in the 32-35Hz range for tuning, if you're after nice, deep bass with a lot of punch, and chest squeezing low end. Here's my suggestion, if your musical tastes run in the rap/hiphop catagory, and not so much on highly accurate response for stuff like jazz or classical. I'd go with a large box. 4 to 5 cu ft if you have the room. account for driver displacement when you calculate the box volume for port tuning (the displacement is given in TS specs for the driver) then go with a 6" ID aero-port, and tune it to 32 to 34Hz. See how that hits you. If you don't like it, you can always re-tune it. |
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Platinum Member Username: GlasswolfColumbia, SC USA Post Number: 12726 Registered: Dec-03 | PS, use double thickness for the driver side panel on the box, and reinforce the inside of the box to keep the enclosure as rigid as possible. Being that large, it's going to want to flex, and that loses efficiency. |
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Silver Member Username: Boston_splHighland, CA United States Post Number: 152 Registered: Nov-08 | Thanks again man. Seriously helpful! I learned something. I like your idea. Is this the type of port that you're talking about?: http://www.parts-express.com/pe/showdetl.cfm?Partnumber=268-354 I'll make sure to check the Thiele-Small Parameters on the sub's displacement before I calculate tuning. It would be kind of nice not to have to "build" a port. (I've done it before with a Kicker 12" L7 enclosure I built (back in '04), kind of a pain in the butt, especially w/o the right tools, lol. But man, did I love having a properly ported enclosure! I didn't realize the difference it would have on SPL over a sealed one! (I was use to associating "ported boxes" with those Best Buy/ Wal-Mart type boxes that my friends used that always seemed to sound like sh*t). Unfortunately, it eventually blew do to my failure to set the subsonic filter, as I didn't know what that was at the time.) Also, could you elaborate on "transfer function in the 55-65Hz range". I have no idea what that is but I'd like to know (assuming it's not a pain in the azz to explain, lol). And is the point of a double-thick baffle pretty much for rigidity due to the weight/ power of the sub? And is the principal behind enclosure bracing, similar to that of SPL competitors leaning & pushing on their vehicles when in the lanes? Like energy escaping in an undesired way or something? Lastly, what would you recommend I use for internal bracing/ reinforcement in a large enclosure? As I've seen things like; threaded metal rods, strips of MDF, etc. used. Thanks yet again man. This is seriously helping me out. And it's nice to hear from someone who actually knows their sh*t. (Unlike the douchebagz at my local car audio shops (San Bernardino, CA). |
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Platinum Member Username: GlasswolfColumbia, SC USA Post Number: 12735 Registered: Dec-03 | http://www.caraudiohelp.com/newsletter/cabin_gain.htm Id brace internally using MDF since you'll have it on hand already anyway when building the box unless you choose to go with a solid wood like ash or something instead. walmart sub boxes come with a port tube that has to be trimmed to tune it for the sub you buy. nobody ever does this and they just throw in a sub and keep the stock port length so they end up with a box that's way out of tune, and thus is sounds liek crap. yes the double face is to support the weight of the sub, and to add rigidity both. yes reinforcing is to keep the box from flexing. two reasons for this. 1 is that flexing alters the box volume, and thus colors the sound, and adds harmonics. 2 is because energy used to flex the box is energy that isn't transmitted as sound and music, so it's wasted power. same with sound deadening a car cabin. |
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Silver Member Username: Boston_splHighland, CA United States Post Number: 157 Registered: Nov-08 | OK, so one last question (I hope, LoL). Concerning the 6" aero port... Which way (ideally) should the port be facing? (btw, the sub will be rear firing) Should I mount it on the front baffle along side the sub? On the top of the box (firing up, toward the top of the trunk)? On the side? Thanks as always for your input Glass! (and anyone else for that matter) |
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Platinum Member Username: GlasswolfColumbia, SC USA Post Number: 12854 Registered: Dec-03 | sub side, or top generally speaking. just remember the port's internal end has to unobstructed for half the diameter of the driver, so for a 12" sub, 6" same thing on the external end of the port, too. |
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Silver Member Username: Boston_splHighland, CA United States Post Number: 160 Registered: Nov-08 | Gotcha! So, since my enclosure dimensions are going to be; 32"L x 16.5"H x 21"L (a.k.a. deep) with a 12" deep port (30Hz tuning), I should be fine right? As I'll have approx. 9" of space (after the end of the port) 'till I hit the back wall of the box. |
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Platinum Member Username: GlasswolfColumbia, SC USA Post Number: 12870 Registered: Dec-03 | yeah you're good. you'll want 6 to 7 inches between teh end of the port and the opposing enclosure wall. That allows the air to move freely and the sound wave to generate without obstruction, so work with that figure to determine where you want your port(s) placed. You want the port unobstructed for the same space outside the box, too.. so think about that if you have a package shelf in the way. obstructing the port will affect the tuning. |
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Silver Member Username: Boston_splHighland, CA United States Post Number: 161 Registered: Nov-08 | Sounds good. It's going in a '98 Cadillac DeVille, so if I put the port on the front baffle I think I'll be fine. LoL BTW... does the gauge of the speaker wire that I'll be using inside the box (less than 2ft. long) make any real difference? (assuming I don't use like 24ga. or something ridiculous like that) I'm planning on using 10awg wire, both, inside the box, and from the binding posts (banana plug) to the amp. (Crossfire vr1000d) |
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Platinum Member Username: GlasswolfColumbia, SC USA Post Number: 12872 Registered: Dec-03 | http://www.roger-russell.com/wire/wire.htm#wiretable |
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Silver Member Username: Boston_splHighland, CA United States Post Number: 162 Registered: Nov-08 | OK, I checked out that chart, but it doesn't list 1ohm loads. I also didn't see any mention of amperage draw on that chart. However, using that chart strictly as a loose guide, it appears that I'll be more than fine with my selection of wire size. Thanks for the link either way. |
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Platinum Member Username: GlasswolfColumbia, SC USA Post Number: 12877 Registered: Dec-03 | actually with speaker wire it's high voltage AC, so current isn't really the factor. Current is more important when you're talking DC, like power wire, where you build heat so you need heavier wire to handle the heat. That chart was meant for home stereo, so yeah, you won't see 1 ohm loads, but seeing the curve from the data given, it's not difficult to discern the same graph for a 1 ohm load based on the information available. |
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Silver Member Username: Boston_splHighland, CA United States Post Number: 163 Registered: Nov-08 | Agreed. Thanks for the help. |