Subwoofer Box Bracing is NONSENSE! 

Crushing subs with a Humvee: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-3lZIXzDsigw.htmlsi=f9Je6ROXQuax3dhR Massive Subwoofers: bit.ly/4cxXhXi Unicorn Spit: amzn.to/4f7gYY1

I've built a LOT of boxes over the years, and the only time I've ever used a corner 45 was to alter airflow characteristics in a port, and it was in conjunction with a lot of other supporting tweaks. Now, as for panel resonances and bracing and whatnot... You are absolutely technically correct in the application you're demonstrating! A subwoofer enclosure needs different treatment than a full range box. Subs typically don't care about shelf braces, but in a full range enclosure, placement of a shelf brace has the ability to impact midbass and midrange performance by altering internal reflections and affecing standing wave characteristics. I've built a few tower speakers over the years that used "shelf tuning" to tweak peaks and valleys. Along the same lines, bracing and mass loading can become the same thing, just depending on how you approach it. I like using 2" dowel rods to tie front to back, top to bottom, offset within an enclosure. In this situation, you're not "dividing" the panel into individual constructive resonances, you're effectively mass-loading two panels. Install that same 2" dowel rod at a 45 degree angle between the front and bottom (or top) panel, and things start getting really crazy. Now you can introduce hardwood/solid wood enclosure materials and play with their natural resonance characteristics... Can you tell I have too much free time on my hands? LOL But again, this is all full-range application. Subs really don't care. They want somewhere nice and solid to sit and make their wub-wubs, and you're not going to drastically change the timbre and presence of a sub by fine-tuning panel resonance. Just build the box with meat where it counts, and put your time and effort into designing a box that matches your sub(s), space and desired output. :D

I was always told was the 45s were for the air flow to have less resistance…I’ve never have have heard it as a brace

U should build this enclosure with no braces do a port score across the bandwidth from 25-75hz then add the braces and see how it affects the enclosure

The one exception I can think of for the corner 45 is when using large radius roundovers on the outside of the cabinet, Ive done that myself on a few builds... But for car-style sub boxes, yeah, the joints -- as long as they are solid -- should be strong enough for normal stuff. Like you said on bracing, were really trying to get panel resonance down... even just gluing a 5x5 inch piece of particle board or MDF slightly offset on a panel will help out with that. Love your videos sir! Youve got a great delivery!

Love this video and topic and here's my take. I have two 15inch boxes built by my local box builder. The first one was built about a year ago and he used corner 45s plus bracing. The second one I told him I wanted it to be the same in specs however I told him not to worry about bracing or 45s and by eliminating those two he gave me a discount. I have the same subs on both boxes and they sound exactly the same to my ears. Yeah the one with bracing is obviously stronger but at the end of the day it didn't make a difference in the sound. BTW, I'm not using huge beefy subs, I'm running 4 skar 15s svr

From my experience I found the best bracing is by using strips that are cut at 45 degrees at the ends. I don't brace across. I brace one side to the side perpendicular to it in more than one spot . If the speaker box is already built I tap on the wood and brace where the pitch of the tap is lowest. That's where the wood is going to vibrate the most. I do this around the whole speaker and place these 45 degrees braces on the spots I find. Of course the area where the speaker cut out is weak and will colour the sound . So I brace next to the hole and brace that to the opposite side. Tapping on the box will show where bracing is needed .

The only time I ever used corner 45s was in a transmission line speaker. I've seen window bracing in high end speakers and they definitely made the box "dead": they sounded and felt like you were hitting a concrete block. Shelf bracing in the most effective way, in terms of time and materials. Gluing tip I learned from a professional woodworker: don't starve the joint of glue (it should drip out when you fasten them together) and sprinkle a little sand along the glue line - just a couple of grains per inch is all you need. When your joint is pressed together, the sand digs into the wood and keeps the joint from slipping as you nail or screw the joint closed.

Battens are useful for prefab boxes. No need for the 45 though. 2x2 lumber will suffice. Way easier and you do absolutely want to do every corner in that case. All bracing can be done with the method you showed. Simple strips of plywood.

I've never thought about offsetting braces 🤔

I'm glad I found this video because now I feel better. Pre drill mdf with pva and timber coarse screws. Caulk in sikaflex after assembly! Sit for 24 hours to get rid of fumes! Half fill with Dacron ( tontine) as specified by electronics engineer who always taught and gave me solutions to a problem. Always had a great sound for a good budget biuld. Only my 15 inch old Targa subwoofer I used 34 mm mdf.

Yes, I would like to see a test of the various different brace styles to test how it affects resonance. I suspect a combination of double thick walls and staggered braces would be the best. But I also suspect the difference between both together and either by themselves will not be that noticeable unless you are using huge subs and a lot of power.

I honestly thought bracing was to reduce panel flex in the box... the baffle mostly. And a few dowels always seemed like the best go to. Didn't consider resonance, good stuff.

I never do 45's I just glass the inside with resin to make smooth as possible and the resin helps with resonance.

I dont always 45 brace my corners, but when I do.......nothing, nothing happens. It makes me feel good tho and I can feel better about myself when im using thay box as a jackstand.

It is true that the bracing changes the resonance to a higher frequency which is good, because they are the ones that matter the least in a box for low frequencies, that is why in HI-FI speakers they are used to eliminate the resonance that can affect the low mids and mids🔈🔈🔈🔉🔉🔉🔉🔊🔊🔊🔊🔊🔊

i've only ever thought of a corner 45° as useful for airflow in a folded or taperd (tl) ports, where maintaining the cross sectional area of the port is important for acurate tuning. as far as corner 45° for strength or resonance 🤷🏻‍♂️, for added corner rigidity, i cut numerous 3/4 x 3/4" sections, about 6" long and afix them along the inner corners on all sides, and some 2-3" wide braces from front to back or top to bottom. sometimes i make a 'stonehenge' looking arrangement of braces in a circle around the woofer hole.

If you are considering comparing boxes with adding 45s, you would be able to do a 1/4 scale of any box design. You're testing airflow efficiency in a plenum. So you can save a ton of time and money in just keeping each comparable box a lot smaller.

Nailed it. Does it make a difference yes, can you hear the difference driving down the road at 60? No. Look into high end audiophile speaker cabinets. 45's in the corners are used for better response and bracing is used in big boxes to decrease resonance. However, the bracing used are many short pieces of wood placed from one panel to the next. Sometimes foam is added, and also dynamat could be used, but again you will never hear it in a car.

The 45’s are mostly an esthetic with the exception of the 45 in the port that I often use to maintain my port width. Often once these are built the point to point at the corner of a slot port will be a good amount larger than the desired port. I don’t think it makes a huge difference output wise, but I have noticed some inconsistency in sound when I have not done this.

Years ago I started using a few cuts of 2x4 as braces (none in corners or seems) to "brace" my boxes. I've wondered about applying vibration (aka. "sound") deadening material to the outside of boxes. I've been a SQ guy for @30 years and a properly designed & built enclosure for the given driver is really what matters ('enclosures' can affect mid-bass also of course). This was another great video, I've never done 'window braces' or sub 'support braces'. Too much work for no proven returns.

Im glad to you made this video, im not new to car audio but i am still learning about DIY custom enclosures, placing them in the port made since for air flow, but the inside i thought was for box flex, ( yes I learned that from the endless videos and articles at some point) figuring only practical in competition settings, not my daily. Thanks for clearing it up. There really is so many mixed opinions in this rabit hole but i love it😂

I've been building speaker and sub boxes since 1988. Back then, no internet, so I checked out books from the local and school library. One thing that people often forget is that the boxes should not provide additional panel or standing wave resonances in the box because no box should really be a one note wonder. So, you aim to try to end up with differing dimensions in the height, width and length of all you panels and try to avoid simple ratios because panels will resonate at their harmonics also. So, one reason for bracing one panel but not another would be the original panel resonates at the original frequencies, but the second panel resonates 8/5 higher (or whatever the ratio) the idea being you want the box to not have any overlapping resonances - just as you mentioned. In the speaker books, any time you had a narrowing of the space, they recommended chamfering or adding a corner brace to reduce turbulence - chuffing in bass. This is why aeroports are also better than straight pipe ports if the port velocity is high. you can design a speaker with no internal bracing that has no overlapping resonances but it takes time and it might not fit in the back of a car or SUV well. Anyway you are spot on with the resonance discussion. Kudos to you sir.

From what ive heard the 45's are for breaking up eventual standing waves inside the box, not for panel resonance or airflow. But if that's the case you're better off making a wedged box anyways.

I'm sure what you say is all true. I've always used a 2x4 as internal bracing. Then I used silicone on all the seams to make sure I had no air leaks.

I have a box that is made out of 10 ga. plate steel that has 2 15's, a divider, and has welded seems inside and out, no port, 1.6 cubic feet per sub, everyone told me it wouldn't work well it does work, it's the tightest hitting 15's, want to talk resonance ever had your heart want to change or skip a beat, this box can actually make your heart want to resonate with the beat, and when it does it is scary. I have always wanted an audiophile to measure all those Q's and Fs things I know nothing about and tell me it is wrong then have them sit and vibrate their opinion in the other direction, to prove it works and it sounds cleaner than any wood.

we put a brace following the shape of the plywood. like we place it along the length of the plywood or length wise. it is a 1 inch or 2 inch long cut depending on the length of the plywood. we dont want the box vibrating like a wood passive radiator

I was just looking for a video on bracing like a month ago. I was building a battery powered bluetooth speaker with two 10" Eminence pro neo drivers, compression driver+horn and a KABD-4100, and wanted it as light as possible, so I used 1/2 ply and braced the heck out of it with battons and triangle braces. This strategy seemed to pay off and panel resonance is fairly minimal, and the box is super light.

Unicorn Spit pre-stain at 50% water dilution, 2 times and sand between... then apply a final coat. This gets depth into the grain and reduces streaking. Cover with lacquer/clear epoxy to make it POP, necessary otherwise it looks like chalk paint.

The double panel resonance is only a factor if the panel still resonates once you've added the bracing. Yes panels will always resonate I understand but by stiffening the box by adding the bracing in the middle (or offset) You have done a great job of minimizing resonance overall. One other option is to install two or three dowels attaching the front and back and possibly even the top and bottoms. This does a fantastic job of minimizing panel resonances

I had an old set of Kenwood floor speakers that have 4 each 12 inch woofers, not subs. They had 2 4 inch mids and a HORN tweeter. 120 pounds each. They had NO bracing inside and just a 2 inch thick fiberglass batting stapled to the rear. The only bracing was the 4 cutouts were glued to the back baffle and Yes 3 inch wide corner braced. I cut the rear panel out and built cross braces with cut outs, used six 1 1/2 dowels front to rear and 2 left to right and added a 1/2 inch front baffle too glued to the original. The only 45 degree bracing I added was to the rear perimeter so i could glue a new back panel in. MASSIVE change for the good.

i have have two big panels left and right side connected with with supports if you knock on the box you can find them, a friend has smaler panels but my are more ridgid. my panels want to move both to the in/outside at the same time so. if you connect them togehter they cant, the travel is limited by the support, i think this will NOT work in the direction from the subwoofer movment but for 2 from 3 direction it will work

Adding the bracing shifts the panel resonance to a higher frequency by effectively making the panels smaller. This can often times raise the resonance completely out of the range of the subwoofer or speaker or bringing it to a level where the resonance is very small because the mass of the panel doesn’t allow it to resonate much because there isn’t enough energy at that higher frequency to move it substantially.

6:45 great bracing but they will change your box tuning and also potentially change resonance of the subwoofers depending on the size and position and amount you install. I personally like the dowel method one top to bottom one front to back and one right to left. Also just caulk all joints instead of 45°

I've never used window bracing or corner 45's... I mean, I've filleted corners using caulking just in case vibration cracked the adhesive or something, and if I needed to brace a long panel, I just use round dowels and glue / screw them in from both sides. Zero router work, perfectly smooth lol

I generally agree with you. Offsetting braces has a long history. In your design, however, does not the port introduce asymmetry into the front and back panels as well as the top and bottom? Thanks!

i personally use dowels to tie the panels together, works well and take s up very little displacement in the enclosure.

i guess 45s can help to brake up some standing waves in a qube enclosure, it can help to act like a diffiusion corner, but i think its a midwoofer problem not a subwoofer problem but they help change Resonat frequenzcy and this will help, so it is box dependend

I never understood the need for corner “bracing” either. Nice video

Well, then i',ve been doin every Thing right in the last years. 45's only in the port and when i use only one brave i go with a Window bracing or every Single wall gets its own brave. Also a brace inside the port can be worth it, all depends on the size and Power of the enclosure. I also prefer mdf with better bracing over plywood

I love your logic bro!! Ppl preach to me that 45s are necessary BUT never 45 the entire box. 👨🏾‍🔬🔊

Great video! There is so many illogical misconceptions out there

With larger enclosure I always use braces. Not only to help with flex but done properly it can also help with tuning. I've even used a brace for port area in a Sq build for a jl audio subs. Added some poly fill to help with port dampening and speed. Actually turned out better than I expected as far as Sq. Probably lost a little on the higher end. But this guy didn't build for spl.

I kinda wish I'd done a full brace as you showed first. I find myself tightening screws on the back every few months because the back wall has 0 bracing. The back wall has two inch thick wool cotton attached to it to soak up the higher frequencies. My box is a two 12 box dual layer MDF inner layer pinewood outer layer. And dual tone dual ported

I would like to see a test done to see if two separate boxes have more box rise than one single box with two woofers

Bass waves like to collect in the corners and travel UP (this is why horizontal 45's aren't used). Corner 45's are good for stopping standing wave formation in the corners of your enclosure. If you look up "bass traps" you will find the audio science behind bass and corners. Bass traps are used in full scale rooms inside of your house for example, but the logic still applies to a speaker box or your car.

The corner 45 isn't for strength. It's a bass trap. The same thing is used in studios. All of those extra 90* angles you're adding with shelf bracing create standing waves that reverberate and start to create cancellation issues.

Great tip about summing resonating panels, and making them slightly different sizes! Never thought about this but makes total sense.

Thoughts on peel and stick deadening materials in lieu of bracing to prevent resonance?

One must determine how loud or audible these resonances are to determine the value of removing them.

When i first used unicorn spit i didnt like it...but i painted my entire enclosure with wood glue to seal since i had no shellac and tried the spit again and it looks badass after you clear enamel it once or twice. Lol i used 3-4 colors diluted 50-50 with water to get more out of em and just slapped the box with both hands doing my best jerry lee lewis impression for a surprisingly neat colorful glittery camouflage looking result that changes depending on lighting and angle

The best way I've found to use shelf braces is diagonally. I only use them on larger spans and don't even attach the brace to the adjacent walls. I attached them with pocket screws on 12" centers just to apply pressure while the glue cures(keeping pressure on your glue joints while they cure is vital, plenty of videos on youtube showing that). Twenty years ago I used to overdue the internal bracing. These days I only brace on spans over 3sqft. I took the 3sqft rule from designing sheet metal equipment, which is much more prone to resonance. To the people gluing and caulking.....just use a polyurethane construction adhesive instead of wood glue. Lay down a large bead so that it squeezes out the edges. You glue and seal in one step. Not only that, but wood glue needs the two surfaces to contact each other to adhere, the construction adhesive can fill gaps and still have a strong joint.

Great topic, I agree with most of your theories. I think building a few different identical enclosures with different types and levels of bracing to prove them isn't really necessary, I'd wager they're all going to perform within a margin of error in real world scenarios with "daily driver" subs. Now if you were going to do this for some 2k+ watt SPL subs and send them to bigD so he can push them with some huge JP93 or other crazy high wattage then yes you might see varying results 😆

Isn't window bracing also used to prevent flexing? That's why or when I use them? Also isn't corner 45 done to smooth air flow? Honestly I don't do any bracing for my normal boxes. Only when I have multiple 75-100 pound subwoofers. Prefab boxes are the only ones ive blown apart or destroyed just from playing music.

So you only have to brace enough to get the resonant of the box outside the bandwidth of the subs? As in above 120hz for most subwoofer applications?

I've never personally had to deal with resonances. I've always focused on reducing box flex. When you dump a lot of power into a piston you can definitely flex the enclosure in and out. It's basically pressurizing and rarifying the air inside the enclosure. The largest panels tend to have the highest flex. Any flex is basically robbing you of output. A simple cross brace, like a 2 inch dowel rod, seems to be the most effective as well as taking up the least air volume. A panel 12" by 12" I'd leave alone. A panel 18" x 18" I would consider adding a cross brace. A panel 24" x 24" I would definitely add a cross brace. This is based on a panel 3/4" thick. When I wrap my knuckles on the enclosure I want to hear a high frequency, like if it were a rock. 👍

I just use 1" dowel screwed to the top and bottom down the center in underseat truck boxes and square i put a cross in the middle each end in the center of the panel

I like the last series of videos posted a lot! The woofer cone displacement comparison video is really good. In the "Advanced Speaker Systems" book by Ray Alden, he discusses the golden ratio as it relates to cabinet dimensions panel resonance, but bracing is not heavily discussed. The comment section here is great, too. I like this video and just recently braced my last enclosure that has a Kicker 50th Anniversary Gold 10". I figured 400w RMS warranted its bracing even though it's a cube. lol

The 45s are more for no hard corners to be there to create turbulance in the air flow. The panels perpendicular to the sub mount holes would be parallel to the air flow so the force works on them less than the walls that the air flow slams into. Think of how bass tubes perform. Some bracing is added just to support the weight of the sub since it is cantilevered by the screws on the front plate.

This is y we use mdf...if you need less resonance.. even tho mdf already fights this pretty good...switch to hdf

I remember in the 90's Kicker recommended 1x1 bracing on all inside corners

I've done my previous box using a shelf brace for some reason at the time I figured if i cut it into a C shape it could maximize the air value but still act as a brace.

This is something i was always curious about. Here's why, over the years I've had tons of both home an car audio speakers. In 90% of the home audio stuff ive owned never had any kind of bracing but i did notice that some of them actually used the cutouts from the main driver's an glued them directly on the back of the box behind the driver. I assumed it was for controlling resonance and strengthening the are behind the driver. If that is the case why isn't that done with car audio boxes? Why go through the extreme of all that extra bracing?

yeah, rattled enought of pre-made boxes apart that didnt have braces and no screws to use them in my builds anyway. Also when doing 45's, i just feel that they make more sence for noise of airflow and less flow reducing for the port(s)..

i wouldn't put a corner 45 in for strength, but in some cases, i might for breaking up or directing sound reflections. its probably going to be a limited use case thing where i'm actually seeing an issue that would require it. most boxes are fine without them.

I use vertical 45's if the port is vertical

Im with you but more surface aera is more surface area for glue so i add all i can for for less box movement but you are right there is no need for doing any of this unless your and audiophile!

i have just made a small 27 liter, bookshelf subwoofer box for an Epique E150HE-44 with passive radiators. but in my rush to get it done i had forgotten to add any bracing at all. but now after watching this i can relax a little

Thank you for this video Justin! I'm getting ready to build 4 boxes starting tomorrow and learning this about braces will save me a lot of time!

You should get a strain gauge and really prove the point.

I have never doubled any wood or braced a box and have never destroyed a bok if that box is built in a way that interlocks all sides meaning one side butted one side over lapping the other on all sides / top bottom it will never com apart I have even pulled all the screws and the old original liquid nail I still use today held it together now if I have to add a battery bank inside my car it is too much anyway so never tested my boxes with more than 4 12 in 1000 watt rms subs with max watts so it could be needed but I have not needed any doubling or braces yet but some just over think everything

😂 this makes me feel so much better about never measuring where the braces go

I’m new to building sub boxes but I have never used any braces. So far I have only built sealed boxes because I’m not willing to give up my trunk. Dual 10s or 12s so far no issues

Thanks for putting this out there 👍

Built my box with doubled 5/8ths (1.25" total) and a tripled baffle I didn't bother with any bracing as the Sundown Zv6 12" on 3kw (two SAZ anniversaries strapped) i'm running isn't gonna stress things that much IMO

You might want to hit the books a little more… the 45* are so air flows smoother out to the port direction… and bracing is to make the box stronger doesn’t change frequency

This makes so much damn sense. Hope lots of ppl see this

I will let you know that when it comes to SPL, the last thing you want is random pieces of wood restricting air flow differently for each woofer causing them to unload. And as for the 45's they always help smooth a corner for better air flow and reducing standing waves. However, if you're going to make a video I would hope that you use an RTA as well as a decibel meter that can monitor the input power.

I offset my braces and use the golden ratio where practical. Cheers for another great video.

HUH!? A corner 45 will definitely help the strength of the corner by adding more glue surface. My experience with MDF butt joints is they can use the extra glue surface. As far as the point of bracing not being to make the box stronger... We can't wan't bracing to achieve two purposes strength AND panel resonance issues? In your example the best idea is to use p2p bracing to further push the resonance up and out of the passband of the subwoofer design. I don't know maybe I'm getting to the point of actual audiophilia, but the 100s of hours I spent behind the measurment rig at Barefoot Sound checking each speaker before it left the shop has shown that it doesn't matter, until it does.

All my years in car audio the corner 45s are for air flow not brace. I actually never heard of a corner 45 as a brace. But even still I never heard a difference in sound from corner 45 with or with out

Tell that to EAW. I have 16 LA400's EACH producing 140 DB at 1 kw. 12 inch drivers in each cab.

Harmonics my friend, harmonics. Small forces can take down big structures if they are in harmony with eachother at a destructive frequence.

Since the panels are going to resonate regardless it's better to have them resonate at the subwoofer's frequency, if you add a brace, you break the panel in smaller partitions, they will most likely resonate at a much higher frequency than the subwoofer, i don't know how that will affect the sound.

Do you have a step by step on how to build a ported subwoofer enclosure? Specifically I need a dual 8” ported enclosure. I want to build it myself but do not know where to start? Thanks!

I've been building speaker cabs for 30 years now. Part of that time I work for JBL, I assure you the corner brace 45° effectiveness is negligible to any frequency below 500Hz. The turbulence that people speak of is only applicable inside ports but if someone does something good and something bad and the copycats don't understand what the bad part is then it just gets propagated as gospel by the sheeple. Sound isn't about what looks good it's about what sounds good. Ok now let's get technical It's not enough to put a brace in just anywhere, even if you brace it well you may have just raised the panels resistant frequency to the next octave which still provides only a 50% reduction in cancellation. The intention is to raise the resonance frequency by several orders like 1/16 or 1/32. The waters start getting muddy from here of splitting hairs of audio file SQ or just rock hard for SPL. Hoffman will tell you ya can't have it all.

I build a crap ton of boxes and always put as much bracing as i can, and 45s. my goal is build it like a tank so it never comes back to me to get fixed. i have had ZERO returns for box failure after 10 plus years.

A braced vs braceless box video would be a great idea! Theres also stuff called "No Rez" I see offered by kit speaker company GR Research thats also apparently helpful.

What do you recommend i do. I had a custom box built for 2 12in p3 rockford fosgate and the guys standard tuning is 36 htz, but i like the low notes. Can i do anything to drop the hertz?

the corner 45s, in my experience are more to add glue surfaces, but you are correct, they should be used on all corners, and from manufacturers they are. though they are usually short chunks that dont go the whole way. as for the rest of your video i agree 100%.

This guy out here spitn. But hard to refute logic, good video!

Is there a book you’d recommend for coming up with custom box dimensions. I’m trying to figure out how I can make my own box enclosure and am having issues finding a good guide on this. I don’t want to be limited to the normal square box enclosures I want the freedom to build a box to any way I see fit so long as it meets my requirements.

could you do a video on the differences of sound between 2 subs that share a ported box, vs 2 subs that share a box that is divided, and having its own port each. I have never built boxes that the woofers share as i believed the sound waves from behind the cone would interfere with each other, coming out of the port.

Offsetting braces what a great move So all this time it’s about resonance not bracing Unless it’s a very large sub or subs

If resonance is modified by mass, why not use the center brace and then attach different sized pieces of scrap wood in the center of each panel? That would make each panel a different weight and therefore, resonate differently.

Tube FTW! No bracing needed.. No resonance issues. 1/3rd the weight! woohoo! I'm sorry I keep bugging about that. I just have to bring it up. lol

Aren’t the 45s for sound? As the sharp Corner cuts down on efficiency of the box (traps the bass)

Box flex lowers output, Big Marty has lots of bracing never seen nothing like it on a Car enclosure

I've been experimenting with cylindrical enclosures. No bracing needed and they're MUCH lighter.

I like your thinking 🤔. 👍😎