# sub box port questions



## scooter99 (Dec 21, 2008)

I don't know if this is where this belongs but if not feel free to move it. 

My question is this. When making a ported sub box, what are the pros and cons of porting towards the trunk or porting towards the cabin, like say the ports through the rear deck? Is there any benefit to porting towards the cabin? 

My install I'm thinking of doing my ports in the ski pass thru is why I ask. But I don't know much about ports and direction and benefits of which etc. This is basically my researching by asking the sub box pros out there for help in explaning it. 

Any help or advise or information is much appreciated ahead of time. Thanks!


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## kyheng (Jan 31, 2007)

Softwares like Bass box Pro is quite good(you have to pay), or WinISD(freeware) for you to test it out. But I will try to make the port in parallel with the sub. You can get the ports from Partexpress or make from PVC pipe(thicker type).
Once you model your sub then only you will know how long the port lenght you need.


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## carlton jones (May 29, 2009)

porting towards the read of the car or to either side of the box gives you less air to pressurize to make sound. this is also called boundary loading so you have less air to move therfore making the bass or sound louder


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## MSimz (Oct 7, 2007)

Scooter,
One thing you will want to be sure of when porting into your cabin is that you have PLENTY of port square area. Any kind of turbulence or chuffing will probably be pretty audible right there behind you. Usually if it is in a trunk or way back in an SUV, port noise is less of an issue.
I would personally make a temporary box to test with to see what actually sounds best in your vehicle. I've done installs that sounds best with everything facing back, some sound best with everything forward, some work best with cone and port on different planes (generally though, I've found this to be the least common).
Alot of this stuff is vehicle specific. A little bit of trial and error will probably go a long way toward getting you the results you are hoping for - and ultimately probably save you some money too.
- Mike


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## Dangerranger (Apr 12, 2006)

It helps a tad but of course the in car frequency response will be more biased toward wherever tuning is. IMO it tends to work better with bandpass than ported just because with bandpass that's where all of your output is anyway


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## Oliver (Jun 25, 2007)

carlton jones said:


> porting towards the read of the car or *to either side of the box gives you less air to pressurize to make sound*. this is also called boundary loading *so you have less air to move* therfore making the bass or sound louder


*Actually , not on this planet*

*
Umm ... WOW !*


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## carlton jones (May 29, 2009)

(um wow) what? would you like to call a shop and test my theory on 1/4, 1/2 boundary loading? and see what response you get.


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## Oliver (Jun 25, 2007)

carlton jones said:


> (um wow) what? would you like to call a shop and test my theory on 1/4, 1/2 boundary loading? and see what response you get.


OK , then where do I put my sub in the car to gain some decibels ?

I want to gain 2 more decibels for the SPL competitons 

I'll take whatever you say I will gain though [ 10 more, 20 more, 30 ....... ]


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## carlton jones (May 29, 2009)

only way that could be properly done is bu having your car and complete system setup.


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## scooter99 (Dec 21, 2008)

Ok so then how do I determin what my vent size would be if I did a sloted vent vs a round one? How do I figure that out. I know, I know search it, but I'm having problems searching the right words I guess.


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## Oliver (Jun 25, 2007)

PORT Size Calculations and Formulas for WOOFER and Subwoofer BOXES
The "Minimum Diameter" box is for round ports, and the "Minimum Area" box is the minimum area required for a square vent. If you need to convert a ...


PORT Size Calculations and Formulas for WOOFER and Subwoofer BOXES

minimum diameter -vs- minimum area


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## Oliver (Jun 25, 2007)

carlton jones said:


> only way that could be properly done is bu having your car and complete system setup.


:laugh::laugh::laugh:



> porting towards the rear of the car or to either side of the box gives you less air to pressurize to make sound. this is also called boundary loading so you have less air to move therefore making the bass or *sound louder*.


Which way do I point it for 2 more decibels - left side, right side, backwards, upwards, downwards ?

*I want to make my sound louder ... Thanx*

Teach me master ... your grasshopper awaits !


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## Dangerranger (Apr 12, 2006)

a$$hole said:


> *Actually , not on this planet*
> 
> *
> Umm ... WOW !*


actually he's right. Boundary loading works the same way that horn loading and baffle step do, almost like a combination of the two. Just like when a baffle causes a speaker to transition from 4pi to 2pi radiation, boundary loading creates a very similar case, this is why home audio subwoofer manufacturers recommend corner loading more often than not. Boundary loading in a tight corner, downfiring, etc works as an acoustic transformer, coupling the air at the surface of the diaphragm with the air in the listening area, thus matching high pressure/low volume to low pressure/high volume, like a horn does.

The typical huge sub box directly behind the back seat, subs firing toward the rear isn't the best solution in most vehicles more often than not. Really if you want a good idea of where to located a subwoofer in a vehicle, look up something like the JL stealthbox model for it and see if you can somewhat replicate it. JL does a good bit of research on each vehicle on optimized locations and you'll notice the solution is very rarely what other people tend to do with the vehicle on their own. JL doesn't just put subs in corners of the vehicle and similar just because of the "stealth" part of the name


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## Oliver (Jun 25, 2007)

Dangerranger said:


> actually he's right. Boundary loading works the same way that horn loading and baffle step do, almost like a combination of the two. Just like when a baffle causes a speaker to transition from 4pi to 2pi radiation, boundary loading creates a very similar case, this is why home audio subwoofer manufacturers recommend corner loading more often than not. Boundary loading in a tight corner, downfiring, etc works as an acoustic transformer, coupling the air at the surface of the diaphragm with the air in the listening area, thus matching high pressure/low volume to low pressure/high volume, like a horn does.
> 
> The typical huge sub box directly behind the back seat, subs firing toward the rear isn't the best solution in most vehicles more often than not. Really if you want a good idea of where to located a subwoofer in a vehicle, look up something like the JL stealthbox model for it and see if you can somewhat replicate it. JL does a good bit of research on each vehicle on optimized locations and you'll notice the solution is very rarely what other people tend to do with the vehicle on their own. JL doesn't just put subs in corners of the vehicle and similar just because of the "stealth" part of the name


you are correct in this assumption Dangerranger >>>>


> this is why home audio subwoofer manufacturers recommend corner loading


*In a car ' U cannot CONERLOAD', period!*

just post up how U haved made your sub louder by the positioing


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## Dangerranger (Apr 12, 2006)

a$$hole said:


> you are correct in this assumption Dangerranger >>>>
> 
> *In a car ' U cannot CONERLOAD', period!*
> 
> just post up how U haved made your sub louder by the positioing


You can effectively cornerload. "Cornerloading" in a vehicle is essentially a location that will limit radiation to 1/4, 1/8, or similar. Think about it this way: you have a subwoofer, in free space, with no baffle. considering the frequencies produced, you've got a 360 degree radiation. Let's say you have a baffle now, that is infinitely long. Radiation is now 180 degrees instead of 360, boosting output. Now lets say you added a side to it, that's also infinitely long. you just cut the radiation down again. and so on and so forth. This is what cornerloading does, having a wall on two sides of the enclosure forces the subwoofer's radiation to be more directional and couples it with a smaller volume of air to move, boosting effective transfer function.

So "cornerloading" would be: say a downfire in the corner of the trunk. It could be an enclosure firing into the side of the trunk and slot loaded. There are a lot of ways to skin a cat. And all help output. Obviously a vehicle has a lot more boundaries and reflections to account for than the home, but it's the principle of it that we're after


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## Oliver (Jun 25, 2007)

Dangerranger said:


> *You can effectively cornerload. *
> So "cornerloading" would be: say a downfire in the corner of the trunk. It could be an enclosure firing into the side of the trunk and slot loaded. There are a lot of ways to skin a cat. And all help output. Obviously a vehicle has a lot more boundaries and reflections to account for than the home, but it's the principle of it that we're after


In a car you can cornerload a tweeter ... I agree !

*You sure as hell cannot cornerload a subwoofer ... period!
*

If U can, then show me how you have made the sub produce *more SPL *:laugh:


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## scooter99 (Dec 21, 2008)

Ok wow! This has turned into a serious thing here seems like. All I was trying to do was get some info not start WWIII.


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## oldturd (Oct 31, 2009)

To answer the original question your driver face and port face should be on the same plane.


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## scooter99 (Dec 21, 2008)

Thanks!


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## kizz (Jun 22, 2009)

Cmon, keep it going guys, this is good entertainment while im at work and i just might learn something. Although, im not sure from who yet, you both have good arguments. Can we get a judging team together for this here boxing match......i mean debate?


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## scooter99 (Dec 21, 2008)

Ok I must just be an idiot! I downloaded WinISD Pro and tried to enter the specs for the Hertz HX300D, the subs I'm getting, and I just simply can't do it. It keeps coming up with an error and a bunch lists of specs that are not correct. So I went into the help section and I'm following all the directions but I'm just not able to get it to work. Getting frustrated now. I just want to see what the optimal box with a slotted port is going to be for these things! DAMN IT!!


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## Oliver (Jun 25, 2007)

Dangerranger said:


> You can effectively cornerload. "Cornerloading" in a vehicle


Please post your improved loudness !

Yes, in theory everything is possible ... in fact you cannot show that you have cornerloaded a sub in a car 

*If someone could in fact do what you say ... we'd all do it.*

If it was just some preposterous imaginings then we will see no known way to move a sub around in a vehicle that will increase the sound pressure levels.
*
It's your turn to show what you have done in fact ... not in your head !*


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## scooter99 (Dec 21, 2008)

Hey, a$$hole, you made another thread about this, take this **** there, stop arguing in my thread. If you're not gonna help just leave please.


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## kizz (Jun 22, 2009)

scooter99 said:


> Hey, a$$hole, you made another thread about this, take this **** there, stop arguing in my thread. If you're not gonna help just leave please.


Word! 

scooter, i have trouble with winisd too. I have only got it to work once. I think i would rather pay for bass box pro if it is more user friendly. 

Maybe AAAAAA will chime in. he modeled a sub for me before, i bet he would do it for you.


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## fuji6 (Feb 4, 2008)

Do a google search for winisd. I can't remember what I searched on, but I found a good walk-through on how to enter values and what to do if you were missing certain measurements etc. Also double check your units of measure when you enter stuff. Sorry I can't give you a link but it was saved on my old pc which is gone.


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## MSimz (Oct 7, 2007)

That's with the specs off of the Hertz website... not sure what issue you're having or what info you are looking for... green is vented, purple is 6th order BP, because as dangerranger said, the vents at the ski-pass plus the trunk sealed off would be a cool (albeit much more complicated) option.


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## Oliver (Jun 25, 2007)

scooter99 said:


> Hey, a$$hole, you made another thread about this, take this **** there, stop arguing in my thread. If you're not gonna help just leave please.


Cool:blush:

My bad ... just find a corner in your vehicle and slide it over there for a much louder sub.

*That is the number one complaint of people who put there sub in the console on their vehicle ... **I CAN'T HEAR IT !!*


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## Oliver (Jun 25, 2007)

scooter99 said:


> My install I'm thinking of doing my *ports in the ski pass thru* is why I ask.Thanks!


1] I'd ask : Hey people who have done this what are your experiences ?

This will tell you something, either that or do a poll.

If it were me doing this for you, *NO - bad idea.*


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## Dangerranger (Apr 12, 2006)

a$$hole said:


> Please post your improved loudness !


I don't have an RTA or db meter as I could give a **** less about SPL....



a$$hole said:


> Yes, in theory everything is possible ... in fact you cannot show that you have cornerloaded a sub in a car


In science and this case, acoustics, we know what is possible. It's up to the person to implement it. Have I cornerloaded in the same sense as a home? of course not, because a car doesn't have the type of surfaces to do it. 



a$$hole said:


> *If someone could in fact do what you say ... we'd all do it.*


Now that's a complete stretch. Even with knowledge of acoustics people still rarely do what would be considered ideal in a vehicle.




a$$hole said:


> If it was just some preposterous imaginings then we will see no known way to move a sub around in a vehicle that will increase the sound pressure levels


What exactly are you trying to prove? that an SPL vehicle doesn't have that sort of setup? Of course it doesn't, an SPL vehicle has an enclosure that takes up as much space as the vehicle will allow. It's about what fits and more and bigger is better in that case. But take one 10" sub and try to optimize it's output and see if the typical box firing toward the trunk works out best...It isn't voodoo, it's acoustics. A sub is going to displace "x" amount of air regardless, that's a given. It's our job to make sure that the work it's doing is as efficient as possible. If you don't think boundary loading works, then look into horn design, or even a simple wide baffle speaker like the Sonus Faber Stradivari compared to a typical 8 or 10" wide home enclosure because of 2pi radiation occuring at a lower frequency. It works.


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## Oliver (Jun 25, 2007)

> . If you don't think boundary loading works, then look into horn design, or even a simple wide baffle speaker like the Sonus Faber Stradivari compared to a typical 8 or 10" wide *home enclosure* because of 2pi radiation occurring at a lower frequency. *It works*.


*Yes !* [ *in a home it works ... **not in a car**... period !*


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## scooter99 (Dec 21, 2008)

Man give it a Fawking rest already! Go somewhere else with this ****! Damn! I don't care about what you're trying to prove, a$$hole. I'm more interested in what information can benefit my build which is why I started this. It's not for you to prove the earth isn't square! If you believe it great, if you don't great, but knock this **** off. Take it to your thread, don't clutter up mine! If you have some valuable information or just something that's going to help, then by all means hang out, otherwise don't let the door hit you in the ass on the w
ay out! 

MSimz: thanks for the info. Not sure why I can't make it work. Can you help me understand please how I would make that port in a slotted style for that frequency? Is it just a matter of area space, or is it particular to a size and depth. For instance, if I'm tuning, just example, to 32hz and it calls for an 8" high by 3" wide slot, but I have to make it 9" high and 2" wide cause of space, does that change the tuning frequency? I have no idea about those measurements, I was just throwing numbers out there. Just trying to understand how it works. Thanks.


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## Oliver (Jun 25, 2007)

a$$hole said:


> PORT Size Calculations and Formulas for WOOFER and Subwoofer BOXES
> The "Minimum Diameter" box is for round ports, and the "Minimum Area" box is the minimum area required for a square vent. If you need to convert a ...
> 
> 
> ...





scooter99 said:


> If you're not gonna help just leave please.





scooter99 said:


> I'm more interested in what information can benefit my build which is why I started this.
> 
> MSimz: thanks for the info. Not sure why I can't make it work. Can you help me understand please how I would make that port in a slotted style for that frequency? Is it just a matter of area space, or is it particular to a size and depth. For instance, if I'm tuning, just example, to 32hz and it calls for an 8" high by 3" wide slot, but I have to make it 9" high and 2" wide cause of space, does that change the tuning frequency? I have no idea about those measurements, I was just throwing numbers out there. Just trying to understand how it works. Thanks.


PORT Size Calculations and Formulas for WOOFER and Subwoofer BOXES <<< This will give you round or slot port.

How else can I help you ?

I'd slide the back of the box up to your rear seat, then play the port and sub towards the rear bumper.

If the calculator above is to hard for you to grasp what they are asking for do a search for T/S parameters [ Theile/Small ]


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## scooter99 (Dec 21, 2008)

Thanks!


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## Dangerranger (Apr 12, 2006)

a$$hole said:


> *Yes !* [ *in a home it works ... **not in a car**... period !*


Cars are no different in the scenario. Cars aren't exempt from physics. But whatever, believe what you want, i'm through arguing, you've already got your mind made up


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## Oliver (Jun 25, 2007)

Dangerranger said:


> Cars are no different in the scenario. Cars aren't exempt from physics. But whatever, believe what you want, i'm through arguing, you've already got your mind made up


It's the same thing she said to you . . . It's *the size that makes the difference*.


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## MSimz (Oct 7, 2007)

scooter99 said:


> MSimz: thanks for the info. Not sure why I can't make it work. Can you help me understand please how I would make that port in a slotted style for that frequency? Is it just a matter of area space, or is it particular to a size and depth. For instance, if I'm tuning, just example, to 32hz and it calls for an 8" high by 3" wide slot, but I have to make it 9" high and 2" wide cause of space, does that change the tuning frequency? I have no idea about those measurements, I was just throwing numbers out there. Just trying to understand how it works. Thanks.


No. 8x3 = 24 in^2. 9x2 = 18 in^2. For a given length, the square area of the port must remain the same. If you change the port square area, the length must also change to keep the same tuning frequency. Read this:
JL Audio - Car Audio Systems
I always use that formula when figuring ports. I prefer doing the math over leaving it to a calculator. It will also help you see the relationship between all of the variables (ports area, port length, box volume, etc...)


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## Dangerranger (Apr 12, 2006)

a$$hole said:


> It's the same thing she said to you . . . It's *the size that makes the difference*.


Well if i ever get a reduction then you're first on the list if I decide to donate what's left.


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## fish (Jun 30, 2007)

People have said many times it's best to fire the port on the same plane as the sub. What are the reasons why it's not a good idea to have the port firing out the side of the box?


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## Oliver (Jun 25, 2007)

fish said:


> People have said many times it's best to fire the port on the same plane as the sub. What are the reasons why it's *not a good idea to have the port firing out the side of the box?*


It sounds sidey


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## TJ Mobile Audio (May 6, 2009)

Pardon the novella. I think I can contribute a bit here, but first there's some ish in the air that need's to be clarified.



Dangerranger and A$$hole both had good points here, but I'm going to have to fall 90% with A$$hole, and 10% with Dangerranger.

I think this was what A$$hole was getting at, I'm only trying to clarify. The reason you can not typically gain an advantage by corner-loading a subwoofer in a car is that the wavelengths of the frequencies involved are large compared to the dimensions of the car. ANY location in a typical car would already be considered corner-loading in a room. You simply can't get far enough under normal circumstances to _avoid_ corner-loading.

Now to give Dangerranger his due credit, moving a box around, aiming it different directions, etc, can have a noticeable difference. I would venture that it can make a measurable difference, but I do not have data to back that up. However, unless your vehicle is the size of a room (RV, anyone?) corner loading should not be a serious consideration.



So if moving the box, aiming the sub and ports, etc, can make a difference, then corner-loading matters, right? No, that's not at all what I'm saying. The differences I have perceived by re-orienting boxes seemed to be frequency specific. Perhaps I move the box a few feet, aim it a different direction, and all of a sudden 60 Hz seems louder. This is explainable in part because a 1/4 wave for 60 Hz is only around 5', which would be enough to move the listening position from a node to an anti-node of a standing wave, or vice versa. If you ever observe this, and if the cab of the vehicle is big enough, try moving around to different seating positions. You may notice that the peaks and nulls are more noticeable in some parts of the vehicle than others.

So yes, box positioning does matter, but not in the sense that was suggested. In fact, I've met SPL guys who swear by it, but that is because they have found a box position and angle that accentuates their peak frequency, and is therefore "louder". In my opinion, box positioning can be a useful tuning tool when you have flexibility of location, and otherwise is simply an explanation for some of the peaks and nulls you have to correct in the bass frequencies.

^ None of that was meant as a jab at anyone, I just wanted to help distill the useful information from the opinions that have been presented.



Now to answer the original questions:



scooter99 said:


> When making a ported sub box, what are the pros and cons of porting towards the trunk or porting towards the cabin, like say the ports through the rear deck? Is there any benefit to porting towards the cabin?
> 
> My install I'm thinking of doing my ports in the ski pass thru is why I ask. But I don't know much about ports and direction and benefits of which etc. This is basically my researching by asking the sub box pros out there for help in explaning it.
> 
> Any help or advise or information is much appreciated ahead of time. Thanks!





fish said:


> People have said many times it's best to fire the port on the same plane as the sub. What are the reasons why it's not a good idea to have the port firing out the side of the box?


The standard advice is to *aim the sub and port in the same plane, and within a reasonable distance of each other*. In my understanding, the whole reason for this "rule" is to avoid unwanted cancellation effects. It is quite possible, when firing the sub into one area and the port into another area to have an undesirable response curve, or even extensive cancellation. Think of it as a giant bandpass enclosure, where you don't know all of the variables. Keeping the port(s) and sub(s) within a reasonable distance of each other removes a few of the variables. I'm not sure if aiming in the same plane is actually significant, but it certainly doesn't hurt.



I would say that 80% of my builds follow the above rule (bold part) and work great. However, I make an exception to the rule based on my understanding: if the port is _close to the speaker_, is unobstructed, and is firing into the same space, direction doesn't really matter. For instance, both of these boxes worked just fine:



















I have not experimented with firing through the ski-hole, because in all of my reading I have encountered far more failures than successes in that regard. I think it is a likely recipe for cancellation or at least a poor response curve. Hope that information helps!

EDIT: One more thing, I endorse the idea of building a test box if there is any uncertainty. I use 3/4" OSB because it's cheap and sturdy enough for temporary use. Usually when I build in my own vehicles, I build at least one prototype before starting the real box. When building for others, unless they pay for the prototypes, I just use tried-and-true methods.


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## scooter99 (Dec 21, 2008)

Wow ok thanks! I appreciate all your help!


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## Oliver (Jun 25, 2007)

TJ Mobile Audio said:


> Pardon the novella. I think I can contribute a bit here, but first there's some ish in the air that need's to be clarified.
> 
> 
> 
> ...


*There it is !*
*
Nodes and anti-nodes are the reason for softer or louder perceptions*


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## TJ Mobile Audio (May 6, 2009)

scooter99 said:


> Wow ok thanks! I appreciate all your help!


No problem. One more thing: if you want to toy with various locations for a box, I suggest building a generic one (maybe more than one if you want to try different port tuning or size) and try placing it in different parts of the trunk, or in the cab if that's even an option. If you find a position that sounds the best to you, then go ahead and build a box that's meant for that spot.

After building hundreds of systems, and trying plenty of unconventional ideas, my default is still "the typical huge sub box directly behind the back seat, subs firing toward the rear". Of course it's not be the best in every vehicle, but it has never disappointed me.

Also, I take back what I said about having never tried firing through the ski hole. I built this one, the guy I built it for claims to have hit 142 or 143 with three 10s and 3kw RMS. However, it was not a standard ported box by any stretch of the imagination:

TJ Mobile Audio, Rexburg: Build Logs
_(or see two posts down for thumbnail pictures)_

If you have the time, and money, and gumption to build something like that, more power to you. Otherwise, I wouldn't bank on the ski hole strategy.


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## scooter99 (Dec 21, 2008)

Pictures didn't come through. I'd love to see it!


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## TJ Mobile Audio (May 6, 2009)

scooter99 said:


> Pictures didn't come through. I'd love to see it!


Here you go, I guess the pictures were too big. This is the box I was referring to, a 4th order bandpass with fairly complicated internal geometery, two out of three woofers inverted, and about $150 worth of 13-ply baltic birch. Design goals were "SQL" in nature:


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## fish (Jun 30, 2007)

That's an awesome enclosure. How many cubes gross did that come to?


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## sqshoestring (Jun 19, 2007)

I thought you often got better results facing subs to the rear due to reflecting the sound off the rear of the car gave the longest path, though it does not always work that way.

The port will supply the output at tuning. If you only have the port into the cabin you will get a partial bandpass sort of, in that you hear the port tuning frequencies clearly and the other frequencies the sub is making are muted. A port might work facing another direction but be difficult to find out if the frequency difference makes a difference in your particular car in that particular configuration....as the sub and port are making different frequencies. Think of it as the port takes over from the sub at tuning, you will see the sub xmax dwindle there and sound come out of the port. Under that it unloads and pumps air, above that it does much of nothing.

I think I had a corner/horn loaded sub at one time. I made a box that just fit a hatch with side firing subs behind the taillights. There was an open spot there between the strut tower and rear panel. I think it horned up and hit the hatch glass. Anyway, it had more output than it should have. I did later port it in the top with a small port, I don't remember well but maybe 2"x3 long for pair of tens was the length that worked best and got low, was better than no port.


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## TJ Mobile Audio (May 6, 2009)

fish said:


> That's an awesome enclosure. How many cubes gross did that come to?


Thanks. That's a bit of an awkward question. Gross volume including outside walls was about 7.2 CF. Gross internal volume not accounting for internal partitions, double baffles, or anything else was about 5.8 CF. Finally, gross internal volume including only the two chambers and the port, as well as adjusting for woofer displacement, came to about 4.4 CF. So my answer, in short, is "how gross?"


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## TJ Mobile Audio (May 6, 2009)

sqshoestring said:


> I think I had a corner/horn loaded sub at one time. I made a box that just fit a hatch with side firing subs behind the taillights. There was an open spot there between the strut tower and rear panel. I think it horned up and hit the hatch glass. *Anyway, it had more output than it should have.*


This often happens in hatchbacks, I think it equates more to cabin gain than corner loading. Horn loading would be another story entirely. Also the lack of absorption and blocking from trunk materials helps considerably to increase output in a hatchback. I've seen it suggested that this is "horn-_like_" but I think that's as far as it goes. I believe what you are describing is just the normal effect of a subwoofer positioned in a very small room.


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## fish (Jun 30, 2007)

TJ Mobile Audio said:


> Thanks. That's a bit of an awkward question. Gross volume including outside walls was about 7.2 CF. Gross internal volume not accounting for internal partitions, double baffles, or anything else was about 5.8 CF. Finally, gross internal volume including only the two chambers and the port, as well as adjusting for woofer displacement, came to about 4.4 CF. So my answer, in short, is "how gross?"


Sorry, I was curious how much total volume something like this takes up. What size/brand subs are used?


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## TJ Mobile Audio (May 6, 2009)

fish said:


> Sorry, I was curious how much total volume something like this takes up. What size/brand subs are used?


It's fairly big. Took up the better part of the trunk of a Mercedes SLK. I think the brand of sub was RD or something like that. You can send a PM to 528Hz here or at CA.com, he'd probably remember better than I do (he's the one I designed & built it for). Anyway, it was three 10" subs taking about 1kw RMS each. And yes, I do still have the design, you can PM me if you have any in-depth questions.


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## scooter99 (Dec 21, 2008)

Ok well let me throw this at you guys then. I was looking into some other sites doing research and came across this, “Pioneer Build-Off” 2008 Honda Element which I fell in love with for a couple reasons. 

Number one I love the look of how the subs are hidden which could go along with the led theme I have through out the rest of the vehicle. They're stealth cause the seats are almost always up, but I could still utilize the pass thru in the seat, I think. I'm working on contacting them to see if they'll help me with this but considering the site i'm sure they're not going to be willing to do so. So i'm trying to do some research on it but not sure how to go about it, what words to use mostly. 

Secondly, the amps that I'm going to use for the subs could be encorporated on the back of the box. I'm building a raised floor amp rack for the trunk so the amps won't go on the sides like they have in this build, but I'm also going to do two kinetik batteries on the sides, which will go something like they have for the amps. 

But since we're talking boxes here, i thought I'd throw this out there as well. What do you guys think about this? What kind of output would it give me with 2 Hertz HX300D's and 2 Audison LRx 1.1K's, one per sub?


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## Oliver (Jun 25, 2007)

Simplicity-n-Sound is in Ca , Bing is excellent at building and employs LED lighting in his designs.

DO A SEARCH for him and save your $$$ 

example: http://www.diymobileaudio.com/forum/diyma-build-logs/17242-my-first-2008-scion-xb-install.html


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## scooter99 (Dec 21, 2008)

i konw bing! He's a great installer. I've met with him before since he lives jsut a couple of cities away. Good guy!


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## Dangerranger (Apr 12, 2006)

a$$hole said:


> *There it is !*
> *
> Nodes and anti-nodes are the reason for softer or louder perceptions*


True. in any sealed space there are locations of high and low pressure due to the nodes and antinodes within that space, and of course if the location of the speaker happens to be in one of the high pressure areas the speaker will see more radiation resistance and exhibit an increase in efficiency and it won't matter which way the speaker is turned if it happens to be in said area.

But what is the advantage of "corner loading" or boundary loading? More often than not, these high pressure areas (antinodes) are close to a surface, which is no different than a home or other acoustic environment. In a room with hard, reflective walls, the pressure will always be maximum at the wall or in a corner when the room is driven at any of its resonance frequencies. This often happens in at least one point in a given vehicle, and it is not possible to turn the box around because the box will space the speaker cone away from the surface. This is where "corner loading", "slot loading" "boundary loading" whatever you want to refer to it as comes into effect and DOES have an advantage. You're not doing it to improve the sub's contribution, you're doing it for the same reason it's done in home audio: to force the ROOM to contribute to the overall output.


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## Oliver (Jun 25, 2007)

> 10-19-2002, 10:07 PM
> The RC posts are by Richard Clark
> 
> 
> ...


Not that an EE with a vehicle that went undefeated for 1 season when the outcome was $$$$ {not trophies,etc..,} would know anything!!


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## Dangerranger (Apr 12, 2006)

"if the effective high pressure area happens to be close to a surface it is not possible to turn the box around because the box will space the speaker cone away from the surface.......RC"

Apparently you missed that part of the post. And it's a very important point as high pressure nodes exist in the hardest, most reflective surfaces of the acoustic environment. And in a LOT of cases, actually the majority of cases, these surfaces ARE the corners. The car is an odd environment, but it's not exempt from physics.

He didn't say there weren't circumstances where it in fact helped, he just stated that the typical reasoning/justification behind doing it were ********. Which I agree with.


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## Oliver (Jun 25, 2007)

> ----*as soon as the sound leaves the confined space the pressure will drop to normal in the actual listening space*------*you cannot get something for nothing* and since the waves of interest are already confined by the dimensions of the car *there is nothing to be gained* ----


You are right Dangerranger ... my boy ... he did say something


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## Dangerranger (Apr 12, 2006)

a$$hole said:


> You are right Dangerranger ... my boy ... he did say something


He's right on that one. The increase in pressure isn't what aids in a home either. I really didn't intend to give a comparison to cornerloading in the home in every single facet as there are marked differences but as I stated in an earlier post, you look at things like JL's stealthboxes, or other applications where research has been put into the car's interior, in many cases, loading in a corner assists because a corner is a high pressure area. Not for the typical snake oil reasonings that installers have pounded into the heads of many, but because it's effective in that very specific location of the vehicle. I really don't think our arguments are THAT different realistically


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## TJ Mobile Audio (May 6, 2009)

I think another diatribe is in order. :blush:

Sorry to pick this apart, because you raise many good points. My real point is that you are presenting ideas which are new to many veterans on the forum, without documentation. If you really do know as much as you claim, I would like to learn from you. But if not, you could easily mislead quite a few people, including the original poster. So I intend the following in the kindest way possible:



Dangerranger said:


> True. in any sealed space there are locations of high and low pressure _due to the nodes and antinodes within that space_


Nodes and antinodes are not inherent within a space; they depend on not only the space but also on the position of the source and the frequency being played. The point I was making earlier is that you may have noticed an increase in intensity at some frequencies when you relocated a subwoofer, because nodes for that frequency have become antinodes. This does not mean you have found the ideal location either, in fact it probably means you have more peaks in your response which will either be fatiguing or need to be smoothed later with EQ.



Dangerranger said:


> and of course if the location of the speaker happens to be in _one of the high pressure areas_ the speaker will see more radiation resistance and exhibit an increase in efficiency and it won't matter which way the speaker is turned if it happens to be in said area.


I wouldn't take this for granted. If it were this simple, you would see SPL competitors measuring the different parts of their cars with barometers, then moving the speaker to a "high pressure area". It just ain't so. 

Moving the speaker moves the nodes, as stated previously. You can't just place the speaker in a high pressure zone, that's a misapplication of the ideas at hand.

However, if you are referring to true horn loading or corner loading (which requires a decent sized room), you would be correct in the assumption that a large volume of air trapped in a corner (or horn) will provide a better impedance match of the cone to the air, which does increase efficiency. However, for the most part this effect has already been harnessed by the fact that the subwoofer is _in the vehicle._ To illustrate this, just try placing a sub anywhere inside the vehicle that is not within 5' of a corner or wall within a typical vehicle. Can't find any such place? Since the frequencies involved tend to have wavelengths of *20 to 60 feet*, and the inside of a typical vehicle is closer to 10', the sub will always be corner-loaded.



Dangerranger said:


> But what is the advantage of "corner loading" or boundary loading? More often than not, these high pressure areas _(antinodes) are close to a surface_


Sort of, but no. In theory at least, antinodes would be equal in intensity whether they occur at a wall or in the middle of the room. Also, antinodes move around dependent on frequency, room size, room shape, and speaker location. What may be an antinode for one frequency will not be for another. There is no universal antinode inside a car, if there were it would be exploited. Bose would be all over that one, they'd probably even give it a patented name. 



Dangerranger said:


> which is no different than a home or other acoustic environment. In a room with hard, reflective walls, the _pressure will always be maximum_


Are you referring to barometric pressure, or acoustic intensity?



Dangerranger said:


> at the wall or in a corner when the room is driven at any of its resonance frequencies. _This often happens in at least one point in a given vehicle_


Unless said vehicle is the size of a whale: this _always_ happens in _several areas_ of a given vehicle, which areas vary in location dependent on frequency and speaker placement. In terms of antinodes occurring at a single point, technically yes. But with a large wave, if you are within a few feet, it's about the same.



Dangerranger said:


> and it is not possible to turn the box around because the box will space the speaker cone away from the surface. This is where "corner loading", "slot loading" "boundary loading" whatever you want to refer to it as comes into effect and DOES have an advantage. You're not doing it to improve the sub's contribution, you're doing it for the same reason it's done in home audio: to force the ROOM to contribute to the overall output.


Refer to above. The width of the box is negligible. Overall output will be roughly the same, just with peaks at different frequencies.



Dangerranger said:


> He's right on that one. The increase in snake oil [pressure] isn't what aids in a home either. I really didn't intend to give a comparison to cornerloading in the home in every single facet as there are marked differences but as I stated in an earlier post, you look at things like JL's stealthboxes, or other applications where research has been put into the car's interior, in many cases, loading in a corner assists because a corner is a snake oil [high pressure] area. Not for the typical snake oil reasonings that installers have pounded into the heads of many, but because it's effective in that very specific location of the vehicle. I really don't think our arguments are THAT different realistically


Sorry, but it does sound like typical snake oil reasoning. You equated antinodes earlier with high pressure areas, and (as antinodes) they will vary based on many factors _besides_ position within a car. Also, I didn't make this comment last time you mentioned JL Stealthboxes, because I didn't think you were serious. Surely JL would document such research, no? Or could it be that they are simply selling the convenience factor of having the sub _in a corner, out of the way?_ Maybe they named it for it's primary attribute, which is stealth? I'm still waiting for the JL Acoustic Perfection box, which I hear may very well be a large ported box directly between the wheel-wells (only 50% j/k on that one).


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## Dangerranger (Apr 12, 2006)

TJ Mobile Audio said:


> I think another diatribe is in order. :blush:
> 
> Sorry to pick this apart, because you raise many good points. My real point is that you are presenting ideas which are new to many veterans on the forum, without documentation. If you really do know as much as you claim, I would like to learn from you. But if not, you could easily mislead quite a few people, including the original poster. So I intend the following in the kindest way possible:
> 
> ...


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## Oliver (Jun 25, 2007)

Dangerranger said:


> *I really don't think our arguments are THAT different realistically*


Polar opposites 



Dangerranger said:


> *I used it as an example but admittedly regret it* as it was taken a bit too literally. Obviously it doesn't work exactly like that in a car.
> 
> *I was just saying* this is not what assists in home applications either for the same reasons, aside from exciting room modes more. Not referring to pressure generated inside the acoustic space which is much different and more complicated to predict.


Let's see if we can agree on something.

*What is your idea of back pedaling *?

Would it include terms like: *I was just saying *? would the word *regret* be used in it ?


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## TJ Mobile Audio (May 6, 2009)

Dangerranger said:


> I guess I should point out one of my beliefs that I haven't mentioned in this thread but have in others: I don't aim for the flattest frequency response with a subwoofer system. Not because I don't think it's important, but rather because regardless of what you do it's going to be far off enough to justify EQ and compensation. So in that event, I fully believe that the intention should be to shoot for the most average overall output, particularly in low frequencies.


I will concede that that makes sense, cutting the lowest of the lows does save on power requirements, even though some box designers (myself at least) find great glee in designing a box that requires little or no EQ when placed in the proper vehicle. Of significant note, your average overall output will _rarely_ increase simply by repositioning a sub. It is usually just the perception of loudness that changes.



TJ Mobile Audio said:


> However, if you are referring to true horn loading or corner loading (which requires a decent sized room), you would be correct in the assumption that a large volume of air trapped in a corner (or horn) will provide a better impedance match of the cone to the air, which does increase efficiency. However, for the most part this effect has already been harnessed by the fact that the subwoofer is _in the vehicle._ To illustrate this, just try placing a sub anywhere inside the vehicle that is not within 5' of a corner or wall within a typical vehicle. Can't find any such place? Since the frequencies involved tend to have wavelengths of *20 to 60 feet*, and the inside of a typical vehicle is closer to 10', the sub will always be corner-loaded.





Dangerranger said:


> I used it as an example but admittedly regret it as it was taken a bit too literally. Obviously it doesn't work exactly like that in a car.


You are correct, in fact it does not work like that in a car at all.



Dangerranger said:


> Acoustic pressure relative to the transducer. The pressure increases, but the velocity decreases.


Velocity of what?



Dangerranger said:


> Primary axial modes cause pressure peaks at the boundaries of the axis.


True, but if you are actually referring to primary axial modes, they only occur between parallel surfaces, and are based on the shortest length between the surfaces, like this:










I fail to see how this relates to corner loading.



Dangerranger said:


> A corner is a junction of two boundaries, so twice the chances. A floor or ceiling corner doubles again.


So if I stand in the middle of a room, spin around until I'm dizzy, then fire my BB gun at random, I should be four times as likely to hit a point in the corner as some other point? Let's say it ricochets off the walls several times, will I really have 4 times as many holes in the corners? Or am I misunderstanding you entirely? If you don't see the relevance, do the thought experiment a few more times. What you are describing is not the reason corner loading works, nor is it entirely accurate.



Dangerranger said:


> I was referring to the pressure generated between the subwoofer and whatever it's loaded into. Example: you take a 15" subwoofer, downfire it with 3" spacing with the exit being only on one side. Obviously there is more pressure between the subwoofer and the floor just due to larger waveforms being compressed into a smaller acoustic space. Once it exits this area it dissipates of course. I was just saying this is not what assists in home applications either for the same reasons, aside from exciting room modes more. Not referring to pressure generated inside the acoustic space which is much different and more complicated to predict.


This was not so clear to me, how exactly do you compress a waveform? I do want to understand, but you lost me here.



Dangerranger said:


> Honestly I doubt they would [release their research] to the general public.


Seems like if there's good science involved, it would be worth publishing to increase their credibility. My guess is that they simply build prototypes until one of them sounds good or meters well.



Dangerranger said:


> But, I must say that if you were to compare and measure JL's stealthbox to a subwoofer of the same type, in the same size enclosure, in the same vehicle with all other variables made equal, just the comparison being placed in a more typical location, the stealthbox 99% of the time will give a better result. It's usually placed in a more more "ideal" location though such a thing doesn't 100% exist. In some cases no, but most of the time they're better than the average hobbyist can accomplish on his own.


Anyone care to test this theory? It's almost worth buying a Stealthbox and moving it around to see if you have a point. I doubt I could actually hear the difference between the corner of a trunk and the center of a trunk, honestly. That said, I do occasionally try boxes in multiple positions before settling on the final spot.


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## sqshoestring (Jun 19, 2007)

Holy crap, sometimes its just car stereo not rocket science. You move the sub around and in 15 minutes you know what it sounds like in many different spots in your car with your sub and the exact box its in.....and no calculating at all.


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## Dangerranger (Apr 12, 2006)

a$$hole said:


> Let's see if we can agree on something.
> 
> *What is your idea of back pedaling *?
> 
> Would it include terms like: *I was just saying *? would the word *regret* be used in it ?


Not particularly. The word "douchebag" comes to mind with response, but in all honesty I'm done with the thread. Go stroke your e-boner.


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## TJ Mobile Audio (May 6, 2009)

sqshoestring said:


> Holy crap, sometimes its just car stereo not rocket science. You move the sub around and in 15 minutes you know what it sounds like in many different spots in your car with your sub and the exact box its in.....and no calculating at all.


:laugh::laugh::laugh:

In all honesty that's *exactly* how I do it 95% of the time. The other 5% means either I have too much time on my hands or my client has too much money...

My only real point was don't worry about corner loading in a car, the effects are minimal. This is because it is already "corner loaded" by virtue of the small room (car). Typically, any difference noticed is merely nodal. The rest of it was smoke and mirrors, as they say...

And Dangerranger, no hard feelings intended, I really just wanted to understand your point. I do appreciate your contribution. At the very least you got me to look up a few things I hadn't considered in years, like primary axial modes. Cheers!


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## sqshoestring (Jun 19, 2007)

TJ Mobile Audio said:


> :laugh::laugh::laugh:
> 
> In all honesty that's *exactly* how I do it 95% of the time. The other 5% means either I have too much time on my hands or my client has too much money...
> 
> My only real point was don't worry about corner loading in a car, the effects are minimal. This is because it is already "corner loaded" by virtue of the small room (car). Typically, any difference noticed is merely nodal. The rest of it was smoke and mirrors, as they say...


Right a car you are into pressure with a sub then not much else matters. I used to wonder about a lot of stuff too and still enjoy Patrick's great threads when I can....but much of the stuff has no real value or effect its just detail....I don't have that time anymore its all about what works for me....once I look it up and can discount it as unimportant in the scope of things that make huge differences like sub cone area/tuning and driver selection/etc/etc. A lot of things you can try in a car and know, or study and calculate for days wasting time and still not know. That is why I like to try drivers in cars its way faster way of finding what works or what type/size you will like in there in case of say tweeters (dome, metal, large/small, etc). Sure you can research, but can you account for the effects of your car and your preferences? Sometimes you can get close, but without measuring equipment most don't have it is difficult and even then people with RTAs are still swapping equipment for some reason.

I had one car the box sure seemed to horn out of the corners, other cars with smaller boxes in the trunk it didn't matter. Nodes yes but not a horn or other loading effect only in that hatch it did that. So, in 99% of the cars I have done it is not important and I don't look forward to filling the entire hatch with box in another car. I used the same subs in different cars and boxes at the time, none of them had that much output for only a pair so I have no doubt something was going on there. Even outside the car it really rumbled.

This place is made to discuss the stuff, but at a point its just not that important or affective to system sound except maybe in some really strange case. I'm not here to trash anyone, just my opinion and experience. I'm not going to hammer someone for researching their system to the fourth decimal point, but I'm not going to do it. Been there and no time for that now.


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## TJ Mobile Audio (May 6, 2009)

sqshoestring said:


> Right a car you are into pressure with a sub then not much else matters. I used to wonder about a lot of stuff too and still enjoy Patrick's great threads when I can....but much of the stuff has no real value or effect its just detail....I don't have that time anymore its all about what works for me....once I look it up and can discount it as unimportant in the scope of things that make huge differences like sub cone area/tuning and driver selection/etc/etc. A lot of things you can try in a car and know, or study and calculate for days wasting time and still not know. That is why I like to try drivers in cars its way faster way of finding what works or what type/size you will like in there in case of say tweeters (dome, metal, large/small, etc). Sure you can research, but can you account for the effects of your car and your preferences? Sometimes you can get close, but without measuring equipment most don't have it is difficult and even then people with RTAs are still swapping equipment for some reason.
> 
> I had one car the box sure seemed to horn out of the corners, other cars with smaller boxes in the trunk it didn't matter. Nodes yes but not a horn or other loading effect only in that hatch it did that. So, in 99% of the cars I have done it is not important and I don't look forward to filling the entire hatch with box in another car. I used the same subs in different cars and boxes at the time, none of them had that much output for only a pair so I have no doubt something was going on there. Even outside the car it really rumbled.
> 
> This place is made to discuss the stuff, but at a point its just not that important or affective to system sound except maybe in some really strange case. I'm not here to trash anyone, just my opinion and experience. I'm not going to hammer someone for researching their system to the fourth decimal point, but I'm not going to do it. Been there and no time for that now.


^ most likely with that hatchback, your entire vehicle *was* a horn, haha. I did a system for a buddy in a Ford Festiva with a single 12, and a 400 watt amp, and when we opened the door of the car it would shake my entire house from 10 yards away. That same sub and amp in my trunk car would have had no such effect.


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## T3mpest (Dec 25, 2005)

TJ Mobile Audio said:


> :laugh::laugh::laugh:
> 
> In all honesty that's *exactly* how I do it 95% of the time. The other 5% means either I have too much time on my hands or my client has too much money...
> 
> ...


I agree with this for the most part. Cars arey very small vs the wavelengths we are dealing with so overall I would imagine moving the sub will make little no difference as it is always corner loaded, if we deal with the car as a whole, ie spatial average between multiple sub and mic points. However, since we are usually only concerned about the headrest position it's usually a good idea to try and optimize for that one spot and avoid acoustic nulls that will sometimes present themselves. I know in my particular car if my sub is not pressed very close to the rear of the trunk I lose ALOT of bass. I havent' RTA'd it to figure out where the null is, but I think it's around 50-60hz by ear. It happens in both seat positions, but not as much if in the back seat. Audibly about 3-5db's, pretty noticeable. Like someone said before it's not rocket science, just move it around a bit until it sounds good lol.


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## sqshoestring (Jun 19, 2007)

I played with my IB 15s and it seems to make no difference in the driver seat with my head on the dash or between the seats, anywhere I could move in the seat. It seems to make a little more deep bass with a window down, not that much difference. It makes less bass if the trunk is open and car windows are up.


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