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Need advice on IB trunk install

7K views 59 replies 13 participants last post by  ILX Cheeta 
#1 ·
Hello all, I just need some advice on a IB trunk install. Woofers will be 2 AE IBAU 12”s. I’ve asked around a bit but have gotten mixed advice. My car is a 2016 Acura ILX, so not a lot of trunk space. Basically I’m wondering the location and orientation I should install them. One person told me to put them all the way into the trunk, right behind the back seat facing the front of the car, another person told me more towards the center, facing the front, and another person told me it depends lol. Will be getting 700 watts a piece. Front stage consists of HAT L1 ProR2, L4SE’s, and L8SE’s in the kicks. I don’t know if there is a general rule of thumb for small compact sedans, I’m just a bit lost right now
 
#2 ·
The big key for IB is that the cabin be sealed from the trunk so that the bass waves from the front of the woofer don’t interact with the back waves. If the two waves interact, you’ll get some cancellation as this is how noise-canceling headphones work, they play a 180 degree wave that cancels the outside noise. Now whether you fire the front of the driver into the back of the seat or the back of the driver into the back of the seat matters not as long as the front wave and back waves are isolated from each other. Persnally, I like having a flat face on the trunk side so I put the magnets against the back seat and put a steel/aluminum speaker grille over the front of the subs to protect from anything in the trunk damaging the cones.
 
#18 ·
The IB implemented properly will sound better. No question. However the subs won't get as high. A decent midbass will make that a non-issue.

I only have about 5-6 hours in to my most current and its done expect beauty panels on top and bottom. They will likely take 6-7 hours.

I'm not taking account of equipment install but a good box with just carpet will take four or five hours so an IB is about 3 times that.
 
#20 ·
The IB implemented properly will sound better. No question. However the subs won't get as high. A decent midbass will make that a non-issue.

I only have about 5-6 hours in to my most current and its done expect beauty panels on top and bottom. They will likely take 6-7 hours.

I'm not taking account of equipment install but a good box with just carpet will take four or five hours so an IB is about 3 times that.
When you say sound better?
In what way do you mean? I know it sounds like a dumb question, but I only ask because it seems like alot of work. What are the payoffs?
 
#21 ·
Best bass you will ever experience. That’s the payoff. And people who think ib doesn’t get loud are crazy. The subs will play high as well. Not sure about that one.
inwould do a baffle begins the rear seat and just seal up the rear deck. Don’t worry about there trunk being sealed.
Time to do it depends on ability and equipment on hand. 30 hours is stupid crazy long time. I did my first one when I was 16 with 2 pieces of crap plywood and a skill saw and a jig saw. It was 2 kicker 15 free air.

also, the bm is not a sub I would use for ib.
 
#24 ·
#26 ·
  1. Anyone who is interested in a IB build should check out a local competition. Although a sealed box has amazing SQ, it will never match the low end of an IB install. I was told however, it has to be done properly, which I don’t know how to do, and most shops are completely clueless
 
#28 ·
Yes. The smaller enclosure of sealed affects the sound of the driver more. However, sealed is also called acoustic suspension and the sealed air inside the enclosure helps control the driver’s suspension so you can pour more power into a sealed enclosure before over excursion becomes an issue (assumes driver can handle power). With IB, the driver’s suspension is on its own so it won’t handle as much power so if you want the most output you have to go with cone area (Sd). But a pair of 12s, especially 15s, can have all the bass most people could possibly need (not SPL people) while sounding deep, accurate, and clean.
 
#34 · (Edited)
Its time I chime in. I remember this called back in the day "FREE AIR"... the only reason I know about it is because when we were looking for subwoofers back in the day the only cheap ones were the very large Pro Audio woofers so that's what we could get our hands on.

THe best parts about doing I/B? For the ABSOLUTE BEGINNER... Low cost and fast and easy... IF you just want to get going and install some Large woofers that Punch HARD in the chest , this is the way Padawan. If you LOVE metal music or HARD ROCK or JAZZ? Your home.

A simple install can get you 90% there to Nirvana.

Easy to cut one simple baffle made of Plywood or MDF or whatever flat thing you got laying around. Even Metal for the Poor Boy Installs on decks that have the holes as OEM like some caddies.

But THIS is how you do it right. And get that AMAZING Punch and I know is sounds weird having a subwoofer sound CLEAR as its something you don't hear described, but it just sounds so... Open.. Transparent. The bass does not sound like its "Back there".. If done right? You get the right Drivers? OMG....

If you just listen to EDM.. Don't bother. Most of the bass notes are just the same old sample.

However.. IF you listen to anything like the Bang of Timpani drums... YOU are in for a treat like no other.
The way it makes your low end have soul is how I would describe it. Movie scores like that of from the beter composers out there will make your JAW DROP.


So let's get on with it.

Most trunk spaces have a Air vent. So when you close the trunk, it lets out air. This is the important part. This air that is from the back of the woofers needs to go someplace. It almost acts as a 3rd order of sorts on paper.

The best installs are actually ones that fire the woofers outside of the cars airspace. THis comes to mind.


However, you don't have to do this or go that far. Actually, for those with Cheap cars like an Old dodge neon you don't care about... Let me tell you how you do this ON THE CHEAP AND EASY..


SPRAY FOAM! Lots of SPRAY FOAM! Get the stuff that expands to the point you see your Panels bulge. Its best if you never have rain BTW.. That's why I said.. I hope you don't care about the car. But you can use Something like FLuid film to help prevent that before you spray. You don't really tend to use that much depending on the car you have.

This is where a SMoke machine really does come handy. And an Air compressor. But you fill every darn Gap there is on the sides of the rear quarter panels. You can make it look nice later. But fill that sucker up and get every hole you can. Try not to mess with areas like where your rear seat belts are and some wiring you may need to get to like for you gas tank hole cover etc.

The Tricky part is the rear deck. You already have vents there. So if you do? This can be an issue. On some cars they exhaust outside.. Depends. Again, that's the hard part to seal. BUT.. If you got a Car you don't care about... SPRAY FOAM! The nice thing with a CHEAP car like a Neon is that there really is nothing there. Once you apply the foam, put something heavy down on the stock rear deck, and press down. with plastic that has WD-40 or some lube so you can work it down without it sticking to the rear deck. Make note if you have clips etc. But you can get a DARN good seal if done this way. THe trick is to fill in ANY gaps there is.


Don't worry about the stuff dripping down as it is easy to break off and clean up and shave areas. You can reinforce with Fiberglass, but most of the time this is not need if mounting the baffle to the back seat area.

I SURE HOPE you ALREADY ran your wires BEFORE YOU DID THIS. :) Ask me how I know..

If you do it right, the rear deck or shelf will push right back into place. THe plastic was so you could do that. Trim any excess you need too to make it fit.

You can lay down something like Dynamat extreme to strengthen the metal structure or FIberglass. You choice.

If you ARE going to use the Rear deck? Then you got treat the rear deck just as you would if you were building any kind of baffle. And you WILL need to Sound Deaden the Rear seat area metal. If its flimsy? Just use Epoxy style fiberglass style Bondo filler where needed to add strength.

When you are ready to add your baffle? This is the part you will have to do some homework. IT IS BEST to use BOLTS to mount that Baffle to the metal frame. This is where you get your Allthread and some struts you would use in the Red Iron in commercial buildings. Put them on BOTH Sides of the Baffle. This will secure it. USE EPOXY! when going through the Steel of the car for the bolts. THis will stop any Vibration. It will also make the BAFFLE Damn near Bulletproof and stiff. Again, SPRAY FOAM and FIberglass where needed and LOTS of LIQUID NAILS for small gabs.

This is just me, but if you are inclined? You can use Plexiglass. But IMO , Wood with either laminate, or use high grade plywood with a nice texture you can stain. You can also cover it with any material you like. Leather really does look nice.

So the part that most people forget is that you do have Vents in the trunk. There are 2 kinds. One with flaps, and the ones with just a water shedding Gore -Tex style cloth, Some cars have 2 of them. Find them. If they are the kind that have the flaps? remove them. Or set them so they open. THere should still be a layer of Breathable Gore Tex like fabric to keep out water. If not? Add that. You don't want water getting in from car washes etc.

The area of the vents are usually behind a bumper. You want to add Open cell Foam to this area so that it will cut down on noise as this is sort of like being used as Port.. That area of the bumper will then be a part of the "ENCLOSURE" so to speak. SO treat the area for anything that will rattle etc.

The most important part is to make sure the BUMPER is SILENT. So do what you need to make sure the Plastic bumper and whatever wires are there DON'T. You can use open cell foam.. But.. Mold and Mildew await if you don't treat it with something like Bactroban etc.


You can enlarge the Vents if you know what you are doing with metal.. BUT NOT RECOMMEND. Most cars are Unibody, and it is apart of the structural part of the car. So unless you know metal work? Don't.

Some cars have a LARGE area or panel that can be removed to get to the fuel pump in the back. You CAN Use Goretex here. But do whatever you can to keep water from splashing inside the trunk. Some of these areas are over 10" squared in area if I am saying that right as far as the Volume of the permenter inside that is open to the outside if that makes sense.
BRB. Need to charge my battery.


Okay. After you do this? the Trunk has a Rubber lip or seal. This is one way to get more Air out of the trunk for the Ideal I.B. Configuration. But again... This is where you need to make a Tuff decision. You can seal it with open cell foam. Leave a few places of rubber so that the trunk close properly. Unlike rubber, this will let air in and out of the trunk space. And keep most of the water and things like Bees, wasps etc from getting into your trunk space.

You want to keep the old rubber seal for winter time. But during the summer, you can use the open cell foam for the lip seal. And this is ONLY needed if you plan to go ALL OUT.

For the trunk lid? Expanding foam. easy and done.

THe Tail Lights are also a great place to exhaust air as well on some cars. I don't recommend it as the large holes tend to let in a TON of water when driving in the rain. But it can be done if your taillights are the kind that allow for such a thing. Again. ONLY for the hARD CORE guy that maybe lives in a VERY dry area.

Some of you are asking about the spare tire well? Why not just use that area ? Well. Remember what I said about structural integrity of the unibody? Well. THat spare tire is apart of your rear crash protection. See, when you get rear ended, ir often protects the fuel tank and also serves as a crumple zone of sorts to absorb crash energy like on some Toyota Camrys.

Cutting up this area can be fatal if it protects the gas tank and lines. Its just something I want to throw out there.


THe one area that actually works best to make a large hole at is the license plate area. THIS really is the best place to make a LARGE hole and then of course waterproof with the same stuff the factory uses to keep water out. In fact, its the IDEAL place to do so for SOME cars.

Now, there is ONE big issue with the trunk if you don't have enough free air space or the metal on the bottom is a tin can.. You HAVE to make sure the Trunk floor is DEAD. Just like you would if you were just putting a box back there. This will seal the deal.


Now as far as driver choices? IMO? Use 18 inch drivers or the largest ones you can fit on the baffle.

If you DO have the Large space where the licence plate is, the killer option here is to make a removable fiberglass air chamber behind the subs that exists out the rear licence plate area. Why? You no longer have to worry about filling anything. Just sound damp as you would normally. Your License plate may sit out a bit. But most of the time, it will be mostly noticeable. Its a clean and simple way that just about anyone can do.

You will have to cut some metal, but a body shop can do this in less than an hour and make it rust proof as well. It will not affect the look of the car that much either.

The best part is? All you need is a Rubber gasket that fits snugly around the "Tunnel" you build that exits out from the back of the woofers. Its actually best to make it out of something soft and easy to remove from the back of the woofers. You want to make the transition as smooth as possible to where it exits.

That does mean that the Baffle you build will have to have accommodations for this. But you can use it without and deal with resource inside the trunk. You end up with a Sudo Box, with a big hole.. Not ideal. But it does work.
 
#35 ·
Its time I chime in. I remember this called back in the day "FREE AIR"... the only reason I know about it is because when we were looking for subwoofers back in the day the only cheap ones were the very large Pro Audio woofers so that's what we could get our hands on.

THe best parts about doing I/B? For the ABSOLUTE BEGINNER... Low cost and fast and easy... IF you just want to get going and install some Large woofers that Punch HARD in the chest , this is the way Padawan. If you LOVE metal music or HARD ROCK or JAZZ? Your home.

A simple install can get you 90% there to Nirvana.

Easy to cut one simple baffle made of Plywood or MDF or whatever flat thing you got laying around. Even Metal for the Poor Boy Installs on decks that have the holes as OEM like some caddies.

But THIS is how you do it right. And get that AMAZING Punch and I know is sounds weird having a subwoofer sound CLEAR as its something you don't hear described, but it just sounds so... Open.. Transparent. The bass does not sound like its "Back there".. If done right? You get the right Drivers? OMG....

If you just listen to EDM.. Don't bother. Most of the bass notes are just the same old sample.

However.. IF you listen to anything like the Bang of Timpani drums... YOU are in for a treat like no other.
The way it makes your low end have soul is how I would describe it. Movie scores like that of from the beter composers out there will make your JAW DROP.


So let's get on with it.

Most trunk spaces have a Air vent. So when you close the trunk, it lets out air. This is the important part. This air that is from the back of the woofers needs to go someplace. It almost acts as a 3rd order of sorts on paper.

The best installs are actually ones that fire the woofers outside of the cars airspace. THis comes to mind.


However, you don't have to do this or go that far. Actually, for those with Cheap cars like an Old dodge neon you don't care about... Let me tell you how you do this ON THE CHEAP AND EASY..


SPRAY FOAM! Lots of SPRAY FOAM! Get the stuff that expands to the point you see your Panels bulge. Its best if you never have rain BTW.. That's why I said.. I hope you don't care about the car. But you can use Something like FLuid film to help prevent that before you spray. You don't really tend to use that much depending on the car you have.

This is where a SMoke machine really does come handy. And an Air compressor. But you fill every darn Gap there is on the sides of the rear quarter panels. You can make it look nice later. But fill that sucker up and get every hole you can. Try not to mess with areas like where your rear seat belts are and some wiring you may need to get to like for you gas tank hole cover etc.

The Tricky part is the rear deck. You already have vents there. So if you do? This can be an issue. On some cars they exhaust outside.. Depends. Again, that's the hard part to seal. BUT.. If you got a Car you don't care about... SPRAY FOAM! The nice thing with a CHEAP car like a Neon is that there really is nothing there. Once you apply the foam, put something heavy down on the stock rear deck, and press down. with plastic that has WD-40 or some lube so you can work it down without it sticking to the rear deck. Make note if you have clips etc. But you can get a DARN good seal if done this way. THe trick is to fill in ANY gaps there is.


Don't worry about the stuff dripping down as it is easy to break off and clean up and shave areas. You can reinforce with Fiberglass, but most of the time this is not need if mounting the baffle to the back seat area.

I SURE HOPE you ALREADY ran your wires BEFORE YOU DID THIS. :) Ask me how I know..

If you do it right, the rear deck or shelf will push right back into place. THe plastic was so you could do that. Trim any excess you need too to make it fit.

You can lay down something like Dynamat extreme to strengthen the metal structure or FIberglass. You choice.

If you ARE going to use the Rear deck? Then you got treat the rear deck just as you would if you were building any kind of baffle. And you WILL need to Sound Deaden the Rear seat area metal. If its flimsy? Just use Epoxy style fiberglass style Bondo filler where needed to add strength.

When you are ready to add your baffle? This is the part you will have to do some homework. IT IS BEST to use BOLTS to mount that Baffle to the metal frame. This is where you get your Allthread and some struts you would use in the Red Iron in commercial buildings. Put them on BOTH Sides of the Baffle. This will secure it. USE EPOXY! when going through the Steel of the car for the bolts. THis will stop any Vibration. It will also make the BAFFLE Damn near Bulletproof and stiff. Again, SPRAY FOAM and FIberglass where needed and LOTS of LIQUID NAILS for small gabs.

This is just me, but if you are inclined? You can use Plexiglass. But IMO , Wood with either laminate, or use high grade plywood with a nice texture you can stain. You can also cover it with any material you like. Leather really does look nice.

So the part that most people forget is that you do have Vents in the trunk. There are 2 kinds. One with flaps, and the ones with just a water shedding Gore -Tex style cloth, Some cars have 2 of them. Find them. If they are the kind that have the flaps? remove them. Or set them so they open. THere should still be a layer of Breathable Gore Tex like fabric to keep out water. If not? Add that. You don't want water getting in from car washes etc.

The area of the vents are usually behind a bumper. You want to add Open cell Foam to this area so that it will cut down on noise as this is sort of like being used as Port.. That area of the bumper will then be a part of the "ENCLOSURE" so to speak. SO treat the area for anything that will rattle etc.

The most important part is to make sure the BUMPER is SILENT. So do what you need to make sure the Plastic bumper and whatever wires are there DON'T. You can use open cell foam.. But.. Mold and Mildew await if you don't treat it with something like Bactroban etc.


You can enlarge the Vents if you know what you are doing with metal.. BUT NOT RECOMMEND. Most cars are Unibody, and it is apart of the structural part of the car. So unless you know metal work? Don't.

Some cars have a LARGE area or panel that can be removed to get to the fuel pump in the back. You CAN Use Goretex here. But do whatever you can to keep water from splashing inside the trunk. Some of these areas are over 10" squared in area if I am saying that right as far as the Volume of the permenter inside that is open to the outside if that makes sense.
BRB. Need to charnge my battery.
Insanely detailed!!! Thank you!
I will give IB a try. Its coming recommended from the gentleman im going to use to implement it so....
A box isnt an option, and a sealed in the tirewell type of enclosure is not an option either as i dont want to lose my spare or trunk floorspace.
 
#36 · (Edited)
Yes, imickey503, great post!
I can see when using large drivers, or many small ones, that venting the trunk to the outside, especially on a small car, would be beneficial.
I would say for a couple of 12's trunk volume would be a non-issue.
I have read that sealing the trunk too well from the cabin can create difficulties with pressurization when closing doors. Not sure how big a deal it is, but just something to consider.
This summer I installed two 12's IB fashion in my '07 Galant and sealed the trunk from the passenger compartment completely. I however did some fiberglass work to build a sealed passage from the seat belt re-tractor openings in the rear deck to the factory fender vent. Works like a charm, though I can hear the flapper on the vent pop open every time I close a door.
For the speaker baffle behind the rear seat I used two sheets of 3/4" plywood cut to match the contours of the car very closely then glued into place with PL Premium construction adhesive and bolted. The Galant only has a ski pass through and a bunch of wasted space around the backseat bracing, which worked out perfectly for flipping the drivers magnet out. I also bolted a sheet of plywood to the rear deck with sound dampener and closed cell foam to make it more rigid. The install turned out rock solid with no rattles.
The real benefit of the IB install is saving weight and space. I would argue against any magical sound quality bonus vs a properly designed sealed or ported box.

Vehicle Car Auto part Automotive exterior Rim
Vehicle Auto part Car Tire Automotive wheel system
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Subwoofer Audio equipment Auto part Vehicle Loudspeaker


(Just ignore the 4X 4" PVC ports in the baffle. That was a little experiment that gave me an extra 6db where it counts, but doesn't factor into this Infinite Baffle discussion.)
 
#48 ·
2 12a are about the bare minimum I personally would use and did use back in 1989-1991. However, if at all possible put 15s if you can. 12’s are nice but the 15’s are awesome when you want to get a bit crazy. I loved my 12s but those 15s were fun as well and cool thing is they can be made to sound as delicate and precise as you want but the 15s and larger can do things 12s can not. But I am a recovering sql guy trying to preserve my hearing.
 
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