Subwoofer Box as a Spare? Volume Calculations + Build - CarAudioFabrication

There are many great locations in a car for a custom subwoofer box or enclosure. A cubby space, wheel well, and even a spare tire location. Once you know how to build a subwoofer enclosure using a stacked profile technique you can fit a subwoofer anywhere in a vehicle and create a strong box that will perform well and sound great!
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Car Audio Fabrication - Master Car Audio - Design, Build, Install

[@jiakabery3550]

Fantastic! I'm looking forward to using this technique to put subwoofers in my rear deck lid. Love the videos!

[@markwentz8332]

3:03 My math game is pretty strong (when it comes to this level) but thanks for explaining this to folks Mark, because 5 out of 3 people do have problems with math. My guess on the oversized baffle is in conjunction with the beauty panel to protect the subs and also maintain some usability of the trunk for cargo/groceries after the install. Looks awesome Mark!

[@CarAudioFabrication]

Lol, that math... :) and you are close. I'll reveal more specifically why soon, I want to see what other people have to say. Thanks for being a Patreon member!

[@markwentz8332]

i'm also curious to see what others think about your design choice and eventually it's actual purpose. Glad to be a CAF patron, at least you give your folks some early/extra content to enjoy besides their name written on a wall #DDFAFO LOL!

[@jayinmi3706]

5 of 3, huh? I think those mathematically challenged people own a bank.

[@markwentz8332]

? not catching the reference there Jay.

[@SundownCamry]

JayinMI his math so strong he's excluding himself

[@jerrylake]

Great work man

[@williamsamson2177]

Great to see you back on the project train!! Looking forward to seeing how this turns out. I'm actually planning a full install for myself at the moment, so I've been going through all your educational videos to choose the equipment and design the system. I want to hide the amp and LOC in the spare wheel well, but keep the spare wheel - aiming for a hinged flip-up amp mount like you did previously. Exciting times ahead! Keep the great content coming!

After watching you do the maths with the imperial system, I really really love the metric system!

[@mwermink7620]

Tommy Grønvold I was about to say that.

[@That_Handle]

Tommy Grønvold , Was thinking the same thing in the early 1990s because all measurements I had for driver spec.s at the time from my sources here in the US used inches, feet, etc. Wasn't long before programs were written for the ol' Texas Instruments TI-8x graphing calc.s for executing conversions at any given stage of modeling coupled with some capacity for basic Thiele-Small parameter work - early shareware. After that, the early internet had a couple fellas sharing their spreadsheets / (browser-operated? ) programs somehow for doing all the previous as well as additional calc.s for various box shapes along with results for port length(s) , overlaying/comparing response curves for different drivers or a given driver's option within a number of different config.s while affording push-pull, isobaric, 4th order and 6th order bandpass boxes when they were popular not to mention an included sinewave generator will settings for a sweep within a given range. The advancement of calculating and unit conversion tech has been wondrous. But, when at the end of the day the lumber is sold in units of inches and feet... it really is much ado about nothing for indigneous.

WOW!! Doing imperial calculations on a Texas Instruments calculator, that sounds like double the work for double the trouble... ;-D I worked with surveying in the late 90's, some of my colleagues used TI's to do advanced calculations. The method to crunch numbers with those was a nightmare to watch, backwards and special functions all over...

[@Dashcam_istanbul]

I saw your comment after I wrote mine. Gotta love the metric system :)

[@brianborell4469]

Many subs in the US have the specs for Vas in cubic inches. SO...

[@mapaneomapax5760]

That math brought back some memories 😂 but I love your videos man! I'm starting to build a sub box for my Miata.... Wish me luck! 😊

[@fmspec]

Always a great video, i need this for my BMW 750i 2018 model

[@АлександрЛовыгин-с8щ]

Good approach. I'm interested. I will subscribe. But although in English I don't understand :) - Everything is clear without words :)

[@daamdaddy5221]

raw talent

[@CarAudioFabrication]

Doing my best, trying to improve one build at a time. Thank you.

[@moparnutalways]

You made the top baffle larger because if you made it much smaller it would just fall into the enclosure.

[@daysend1341]

I would think u did the large piece for two reasons, one Aesthetics and two direct. hard vibration towards the sound mat you put in and have only the good waves going towards the trunk and cab just to guess not sure.

[@kencohagen4967]

The larger baffle allows you to remove the subwoofer when you want to, and positively locates in the trunk without allowing it to move around and possibly causing a buzzing around where it isn't wanted. Am I close?

[@kristoferbrown8007]

I'm curious what you did with all of those leftover MDF circles. I imagine you can use them to cut our other circle rings in the future. Also, it looks like that flush trim bit routes through that 3/4" MDF pretty easily. Is that true?

[@CarAudioFabrication]

I used the insides of the big circles to cut the smaller circles! I had very little scrap and built this whole thing with only one sheet of MDF. And yes, that bit is awesome, linked in description

[@DaWalkDude]

You're planning a fake floor, aren't you?

[@timothygragg9872]

This is really kool, this guy knows his chit exceptionally nice work guy & this guy without a doubt can build a house no prob, Tim G.

[@jamesorr1200]

Flexing that engineer mind in this one! This was a lot of fun to watch.

[@CarAudioFabrication]

😎😎😎 And this one isn't even that complicated, remember the Jeep box? 🤤🤤🤤 Watch it here: kzbin.info/www/bejne/hZ2QeWN7d6qCa8U

[@matth787]

Your work is amazing. The attention to detail is crazy good. I plan for my builds as well but nothing like you execute. Thanks for taking the time and effort to show others! This is just the sub box....WOW!

[@CarAudioFabrication]

Thanks for watching! It's guys like you that appreciate what I am trying to show that are the reason do this! Thank you!

[@1974UTuber]

Hi Mark. Just wondering what your thoughts are on the use of fiberglass. I have done a similar project to this one using a flat circle base piece, a mid ring and a top ring. Held it all together with MDF upright joiners and then glassed it all in outside the vehicle after covering the rings in a stiff cardboard to get the wheel well shape. I finished it all off both inside and out to be smooth then added my top panel with countersunk speakers. I find that fiberglass gives a lighter enclosure but still really strong.

[@cafe80s]

Just a quick question. I really like your videos and I've been wondering what your day job is.

[@PuRe_XtC]

Can I buy this man a beer for being a god among audiophiles?

[@CarAudioFabrication]

In a way! (very few people do this, maybe one or two a year) www.caraudiofabrication.com/support

[@alexsolis1608]

Thank Great video. Is fiber glassing dead for you. Because I see you stacking more often or is stacking a better option whenever possible. I also saw the video of your earlier build the Green Monster would you stack that as well if you were doing it today

[@ashemoski]

Why build a complex enclosure (and use up precious space) when you can simply install the sound deadener and use a baffle/front panel across the top of the well? This gives you a sealed enclosure in and of itself? This is what I did in my '95 Mustang, and it worked out very well.

[@chrislingle1975]

Love watching this method. I have only used the fiberglass approach for spare tire enclosures. The math part always intimidated me but you made it very easy to understand. As always, thanks. Btw I will be contacting you again soon for another one of those awesome enclosure designs.

[@kimjorgensen24]

You are so right. I always just 'winged' the volume 😄 But last time, I just got one Marks finished box designs 👌🏼

[@brianborell4469]

More people should watch and follow these ideas. He shows how cylinder volumes are easy to calculate. The laminated ring construction method is an easy way to to fit an enclosure of a known volume in any odd shaped space too. Wish I could give C. A. F. 2 thumbs up! 👍👍

[@jsierras81]

Mark, diggin’ the build. Watched all the videos for project stealth and honestly would like to hire you to customize my impala. I have… (3) 10w6v1 Precision Power PCX-2400 Precision Power PCX-480 Precision Power PAR-225 I want my trunk pounding clean n clear of rattling and outside noise just like your Pontiac. Please let me know if you’re available for “Project Impala” Sorry for the public message, I don’t know how to direct message on KZbin.

[@buddean8186]

Thanks for these vids mark u sure got talent man im planing on doin this in our grand cherokee for a steath box its get to learn how to measure circle sub box volume Thank you again

[@RobWhittlestone]

I love your channel. I'm a lifelong HiFi nut, car nut, love DIY and workshops and am a physicist - you have great, quality solutions. I love watching your thought processes and seeing your experience. Wish I lived nearby! :-) All the best, Rob in Switzerland

[@DREYDAYMAN]

This is what I need for my 18' Mazda3 hatchback with one change. I want to keep my spare tire. I went to a local shop and was told they could do make the sub box but it might now sound good.

[@johnnygeorgopoulos4072]

Now I know we're working within the restraints if the spare tire enclosure, so you can only use so much area, but wouldn't either hand blending those MDF rings on the inside be better to gain a few more cc's of enclosure volume be beneficial, or, just making the top baffle out of MDF and actually laying the enclosure out of fiberglass be better to make the absolute most of the area given....or is it not true that a larger enclosure will be able to play deeper?

[@RobWhittlestone]

The baffle is larger because 1) it will help with the sound 2) it's aesthetically more pleasing and looks like it was meant to be that way 3) stops small junk falling into the cavity between enclosure and wheel well. All the best, Rob

[@dustykent5259]

Great vid. Love the channel. I noticed the math doesn’t match the build so I think this is a good opportunity for you to discuss different design considerations/ compromises when doing a build. The math calls for 4 small and 8 large rings; as built you have 4 large, 3 small, and 1 small small. This really undersized the volume. Maybe only one sub would have worked better... or a different sub? I just noticed the discrepancy so I’m wondering what your thoughts on it are.

[@CarAudioFabrication]

The math I showed was just an example using random values, it wasn't what I actually ended up targeting.

[@inthepocket9136]

Are there any disadvantages of the round design compared to the regular box style?

[@stevesisniegas]

i'd like to buy one of this for my project , i have a TW3 12'' JL

[@MrDawnkeeballs]

Awesome job like always man but wouldn’t you have saved more material if you’d cut half circles instead of full circles? It would make for a more efficient cut-out pattern in the mdf sheet and then all you would have to do is stagger each layer so that the half circle joints would be perpendicular to each other and maybe use some staples or finishing nails along with the glue just for reinforcement?

[@НиколайОзнобихин-р8б]

Like from Russia!👍

[@_BangDroid_]

From Russia With Like 😅

[@НиколайОзнобихин-р8б]

BangDroid 🤣👍

[@tatialo37]

From Puerto Rico to Russia 🇷🇺 Saludos amigo!!!

[@davidjohnson5435]

Where are you located and how much you charge to build a custom box for a 2014 kia optima sx?

[@TENNESSEETRACKHAWK]

Dam dude u got some skills.....

[@MayzDayz007]

Dude has some tools

[@EarlCharles]

What is better a stacked sub enclosure or fiberglass, which of the two are more affordable to build and sound Q?

[@voyeuphucbinhyen4437]

I wanna make a box for my JLAUDIO12W7 same style is it okay ?

[@milesbown5037]

I assume that you made the head or top larger as to compensate for the space or drop that exists after placing the ring so in short if I am correct u just table topped the enclosure so there was a space between the bevel of the spare tire drop and the upright of the enclosure

[@eazygfx4815]

What about a hexagon design to save wood? Instead of circles glued on top of eachother

[@vthors2826]

Jeez. Luckily the majority of the world uses metric.

[@shakirshaikh385]

hi friend if u use 1 15 inch kicker wooffer with monoblock d amp believe mi really good bass

[@MayzDayz007]

04 Cadillac DeVille DHS? Want to put a 15" NVX VCW154

[@murphyspell7125]

I've been wanting to build a spare tire well t-line...any insight?

[@nurseklb013175]

Focal for the win. Have a kx33 in my Jeep and love the quality and sound it offers.

[@luketanner7638]

I came here to learn. I learned that my goal isn’t important enough to do it the right way😂

[@bendodds8261]

What size MDF do you use i have a fake floor in the boot at 12mm think

[@WHATEVER956]

Wow! I need this for a 2019 Mustang!!!

[@jessesimmons1910]

The top is bigger to take up the Unlevel space in the trunk that the factory pics had. Gives that its always been there look

[@cooleynumpsey5084]

those focal subs are high. I remember when they came out in crutchfield

[@user-wn3en5gl1u]

I’m doing the same thing,I can’t really make out your handwriting. I’m also making encloser for jl audio 12”TW3 subs (2) . Can’t seem to find the exact specifications on two of those subwoofers the only give it for one of the subwoofers and then they say multiply it by two which I done and it seems very large. I’m trying to go for a ported enclosure so if you could just tell me those formulas you had right there, I’ll probably just be able to plug the numbers in, thank you

[@CarAudioFabrication]

The formulas are for volume of a cylinder, feel free to google them

[@milesbown5037]

WASN'T a space between the bevel of the Spare tire drop.

[@WAKEFIELDRides]

Great video, Mark! Looking forward to seeing the end results on this one. :)

[@Trogdor-mo6tx]

When can I start working for you? It would be a dream!

[@FaceYourFear.]

What’s that dual ground bar called?? 5:16 ... thanks!

[@robbybedow7801]

This but in Grand Caravan stow and go seat compartments

[@miguelbertoni4601]

How much space must there be between the bottom of the subwoofer and the floor

[@austinej2785]

Nice video, but I did get 10.5 on the large circle

[@JR-ii4lq]

Amazing! Your thought process, work ethic and presentation skills are amazing.

[@kennethrussel7009]

Thank you mark for showing us how the spare tire sub woofer enclosure is done.

[@Thomas-ft7oh]

Wow Mark, looks great! Excited to see the end result on this one :)

[@oynamalan]

where is the rest of the video ? Finished product and testing ?

[@reddeerrebelrc6674]

Mdf dont like water...i would have glassed it

[@BBGuitars]

Boot floor is likely flat where the base of the spare may not be, adding an extra large baffle means the enclosure has a flat reference point rather than siting the enclosure on the bottom of the spare wheel well and trying to match the rest of the panels with that after...

[@CarAudioFabrication]

Boom! Finally soneone got it! It also gives me a good way to add spacers for the beauty panels that will sit up above the subwoofer and amps.

[@BBGuitars]

CarAudioFabrication ill be waiting by the front door for the prize money in the mail 😂

[@lampinlance]

Great job! I love your videos Mark! My take on the oversized top plate is to completely cover the wheel well so nothing will fall in between the outside of the sub box and the wheel well walls (say that three times fast).

[@TheJBtron]

I better stick to making pb & j sandwiches

[@Pwnz10]

Guys i will put my question here because I really am a noob when it comes to car audio. I have 6.5" speakers in my front doors and two tweeters above dash. I want to replace them so i can get a better sound than the factory, nothing much. I want to inves about 100 dollars. Can you recommend me some speaker models that fit my specs?

[@CarAudioFabrication]

Save more, $100 isn't enough of a budget for a true benefit. You will be more happy if you save $300. Put $100 towards sound treatment materials and $200 towards slightly better speakers.

[@RedLP5000S]

I was lost at the word "calculate".

[@Dashcam_istanbul]

A suggestion. Why don't you use metric system? Much much easier and sensitive. The spec sheet did have the metric values needed.

[@CarAudioFabrication]

Because I use the imperial system. More sensitive? Lol. Converting values isn't hard, but folks who use metric always seem to have trouble with it.

[@MATISTHERAT]

Been waiting for this video for 3 years 🤗🤗🤗

[@SupraJoel]

Half this video is just math tutorial. Most DIY home builds people dont even bother with box size, they just want to know how to build it.

[@CarAudioFabrication]

How about instead of complaining about the free content, just don't watch it if its so horrible for you? I assure you there are plenty of people that care about the math, and I could care less if I appease people with the mentality of "who cares just throw it in" I don't need your negativity

[@beardedgaming1337]

ok man. you lost me on this one. faster and cheaper to do a single wood top plate - then fiberglass the rest. get more air volume, tighter fit. the cost in wood on this... stack fab is cool but totally impractical.

[@CarAudioFabrication]

If you think doing fiberglass is the cheaper route I would have a hard time believing you've ever done fiberglass. MDF is cheap and I can make this FAR faster as opposed to doing a layup and having to have the car smell like chemicals for a month after.

[@frankbush8368]

So if a spare tire isn't practical for that car, then why did the manufacturer add spare tire space? If they bothered building the round space (as in round= for a tire) then why didn't they just put a darned tire in it? Sheesh.

[@frankbush8368]

Not that you have inside info on that decision of theirs... really I'm just commenting because that seems like a whacky thing to do. My mother's silly little Hyundai has the same round space in the trunk, the same size wheels front and back, yet they still don''t sell the car with a spare tire. She got a flat one time and I had to come help her out... but no tire. That's a major WTF, eh? Also the care comes with low profile tires too, so when you get a flat you can plan on buying a new wheel too.. Great!

[@garrettgiuffre7298]

Osooosshso. Sports car. No spare. Staggered. Yep

[@zacharyturner7913]

When looking in the trunk of that car your building that spare sub box for, why does it look like there’s 2 little bitty subs at the bottom of the spare tire holder???

[@LukeTheJoker]

Rubber drain plugs in case water ever pools in the spare wheel well.

[@tonyceja2466]

Te top piece is oversized to seat on the trunk floor

[@fabriciodefigueiredo3426]

And if you get a flat tyre, call an Uber.

[@The-GreenHornet]

Mark, I really struggle with math; always have. I sure wish I could have you or someone else figure my needed box volume for a P2 Rockford Fosgate 10" sub woofer if I give my dimensions.

[@caineh2379]

Thank you for showing this!! So happy to see this all come together!!

[@dee1380]

😂🤣 that iz somethan else...

[@MayzDayz007]

You want about a 2" - 2½" baffle

[@WilliamvanNunen]

Hey Mark nice vid! Greeting from car audio fan from the Netherlands. Why did you make the sub inclosure not from pvc? I’m curious.

[@kencohagen4967]

Focal rocks! My mains run a pair of Focal 7k415's along with a pair of TD90K tweeters. They give awesome response from 45 to 22kHz. When coupled to my subwoofer I get a system response of 23hz to 22kHz at -3db. The roll off of the sub is pretty flat with a system Q of .81. That gives me 20Hz and below at an audible level. The system is awesome, great imagining with all the data coming through the system. Nothing is lost lie some speakers which have muddy bass response that colors the sound.

[@UnknownGhostK]

If this vehicle doesn't have a spare tire cause it have big wheels, then why there is a spare tire location?

[@CarAudioFabrication]

Because there are lower trim levels that dont have the larger wheels. The auto maker is going to invest millions in having a completely different body retooled just for the highest trim level.

[@user-wn3en5gl1u]

Why did you choose MDF over fiberglass,

[@CarAudioFabrication]

Doesn't stink, less expensive, easier to build a robust thickness, shape control for volume calculations

[@soostorn7611]

Very useful and addictive video. i actually watch this a few times already. Is it a good idea to use just one MDF as a top mount over the spare tyre well (and no need any body / sidewall). If I can find a way to secure it, then I got a much larger air volume box.

[@mopar392ta3]

If I do something like utilizing the spare tire area. How would I add a port? And would it sound good?

[@jesperhannus3806]

Hi I'm doing my first sub install into my car and I calculated that I need a power cable that is at least 16 mm². At my local audio shop they have 20 mm² and 35 mm² wiring kits. Is it good to take the 20 mm² or should I take the 35 mm² just to be safe? Any problems with having too large cable?

[@radioactive77]

An easier way to calculate base size of box for this is to simply get a 12x12x12 cardboard box (equal to 1 cubic foot)and fill it shipping peanuts . Then fill area in car with peanuts . Then you can see how many peanuts it takes to fill area . If it doesn’t take a whole box of peanuts then measure down inside cardboard box to See how many inches are subtracted from leftover box. A lot easier and can do multiple weird shapes

[@thefoxchamber]

Is the box ported?

[@GeNeRatioN4kTa]

Hello, i have a bmw 118d sport 2013, and i buy one Pioneer TS-3002s4 subwoofer preeloaded in pioneer UDSW300D, you can give me some tips for choose amplifier, speakers and cable ? You think is ok to buy another one Pioneer TS-3002s4 to have 2 of this or is too much?

[@GeNeRatioN4kTa]

and what tweeters ?

[@GeNeRatioN4kTa]

#CarAudioFabrication

[@u9Nails]

Why did you make the top panel larger than rest of the enclosure? Some extra room to mount amplifiers or wire terminals perhaps. But, also you don't want to floor / carpet to sag in the void you cause by removing the factory panel you initially copied.

[@seancmadison]

When you did the math your equation was for 1.3 cu ft³ was that the required space for one sub or both. I'm planning a dual sub hidden spare install and was curious if using 2 subs like you did would require twice the area space inside the enclosure?

[@ProDigit80]

Well done. BUt you could have just installed a single twelve inch, higher power, and use rockwool or foam bedsheet insulation. The two tens are about as loud as a single twelve, but with more mid range. The soft foam fabric will allow deeper bass.

[@Vision-MileHigh]

Ha good luck when you get a flat.

[@jamescorfield534]

I support you Homes. Even though I can’t afford to Patreon right now your supporters still help you out as much as we can. You’re a staple of the community more than crutchfield

[@silentbravo]

The oversized panel will be easier to secure to the vehicle, maybe even with the factory mounting points.

[@clippingcoils8215]

I'm guessing its where your going to mount the amps.

[@David32wireman]

Richard Moore that’s a good guess, but in one of his other videos he showed how he designed the amp rack for this particular build

[@TacoViolator872]

I don't use Twitter and all those things, any chance you have a plan for a 14 ram box, one side, passenger, for a 12" shallow sub? Great videos as well!

[@eddieshittie4368]

technically speaking though, a donut spare would be fine if the vehicle is fwd. Those spares are not supposed to be used as drive wheels and or steer wheels. So if its fwd they would only be for the rear....unless you get a flat on the front then you would have to take a wheel from the back and move it to the front but since you have 2 different sizes then nevermind. You know what you are talking about so i'll stfu.....cool build btw.

[@mrjay6142]

🙉 I should have stood at school LOL