Aesthetics vs practical.

[LosIsATool 5,000+ posts]

This guy? He has the port loaded off the rear close to the back.

No Terry Brock. Box to the rear of the trunk. Port and subs firing into the cabin. Not sealed off. Not closer to the cabin. The exact opposite of what physics tells us works. And btw those phase issues are broken down by frequencies. 60hz my be in phase, rest may not.

 

[Jeffdachef 5,000+ posts]

No Terry Brock. Box to the rear of the trunk. Port and subs firing into the cabin. Not sealed off. Not closer to the cabin. The exact opposite of what physics tells us works. And btw those phase issues are broken down by frequencies. 60hz my be in phase, rest may not.

Firing into the cabin/walling off is completely different from a trunk setup with the seats blocking the way.

 

[LosIsATool 5,000+ posts]

Firing into the cabin/walling off is completely different from a trunk setup with the seats blocking the way.

It's just a box in the back of a trunk. Talking about seats.. That changes everything, some are thicker, ski passes, rear deck cut outs. Physics don't work here.

 

[keep_hope_alive Premium Member]

You are hearing more than out put. You are getting odd reflections. But like everything else every install will be different. I think KHA was referring to a corner loaded sealed application.

corner loading or rear loading have a similar effect: they minimize cancellation. when you pull subs toward the front of the car the reflection off the rear of the trunk has a later arrival time and it just happens to fall in the audible range of the sub.

the pictures posted by the OP suffer loss in bass in the cabin because the bass is effectively sealed off from the cabin.

ideally, we want to pressurize the cabin and we want to minimize cancellation in the frequencies of interest.

-- for SPL cars the frequencies of interest are a narrower band and the install can be adjusted to take advantage of constructive interference and not care about the adjacent destructive interference.

-- for SQ cars the frequencies of interest are the entire range of the sub stage and thus any phase interference (constructive or destructive) is bad.

even my ported designs take the vehicle into consideration, when possible. some have been successes and some have been failures but each has taught me a few more things. what most neglect to consider is how the environment will affect the enclosure. the orientation in the vehicle can mimic longer port lengths or bandpass enclosures. my sub fires forward, but the airspace between the sub and rear seat and the opening in the rear armrest creates a bandpass enclosure. i didn't design my ported box for that application and so it's not an ideal setup.

 

---------- Post added at 10:04 PM ---------- Previous post was at 10:03 PM ----------

 

It's just a box in the back of a trunk. Talking about seats.. That changes everything, some are thicker, ski passes, rear deck cut outs. Physics don't work here.

physics work everywhere.

 

[keep_hope_alive Premium Member]

over the past 20 years i've put subs in every orientation i can think of in a trunk, in a variety of sizes and quantities (though most of them have been 12's).

my #1 preference is rear deck (IB, sealed, or ported) but it's an assload of work and requires a ridiculous rebuild of the entire rear deck and elimination of torsion bars. this is rarely done.

my #2 preference is behind the rear seat but the rear seat is an obstacle (construction type) and the rear deck needs a lot of help. IB is my goal for SQ.

my #3 preference is corner-loaded (sealed or ported).

a lot of SPL competitors have gained by switching to sealed-off behind the seats vs box in trunk. they focus all energy into the cabin and none is wasted in the trunk.

 

[LosIsATool 5,000+ posts]

over the past 20 years i've put subs in every orientation i can think of in a trunk, in a variety of sizes and quantities (though most of them have been 12's).
my #1 preference is rear deck (IB, sealed, or ported) but it's an assload of work and requires a ridiculous rebuild of the entire rear deck and elimination of torsion bars. this is rarely done.

my #2 preference is behind the rear seat but the rear seat is an obstacle (construction type) and the rear deck needs a lot of help. IB is my goal for SQ.

my #3 preference is corner-loaded (sealed or ported).

a lot of SPL competitors have gained by switching to sealed-off behind the seats vs box in trunk. they focus all energy into the cabin and none is wasted in the trunk.

I'm on my first trunk build since the late 90s. My seats are solid with no pass though. Rear deck is covered with a sheet of MDF for the amp rack. Single ported 8 moved all over the trunk and results didn't change enough to notice except more rattle closer to the back. Also sounds the same in the cabin before and after the deck was pretty much covered. I'm not chasing numbers but I've got a pretty good ear. The MS-8 does not TA the sub

Btw that trunk build with just a box is the record holder. Wasted energy I guess

 

[NASTY08IMPALA 5,000+ posts]

Just mess with it every car is different ..my car ***** firing forward ..sealed off or not..i have played with every inch of my trunk for countless hours...i messed with a setup one night and ended up firing the box at a angle and did a 145 with 2 sa 12s on 2k ...mine get minimally louder with the box closer to hatch but not enough to care .its loud

 

[keep_hope_alive Premium Member]

Btw that trunk build with just a box is the record holder. Wasted energy I guess

-- for SPL cars the frequencies of interest are a narrower band and the install can be adjusted to take advantage of constructive interference and not care about the adjacent destructive interference.

my point was that a trunk box can exploit constructive interference and thus be loud in a narrow band of frequencies.

 

[LosIsATool 5,000+ posts]

my point was that a trunk box can exploit constructive interference and thus be loud in a narrow band of frequencies.

Or it could be that's what works for that car, that meter location, at that given frequency.

Physics only works if there are no variables. If it did work every person that had a ounce of knowledge would be using the exact same thing with the exact same results.

 

[keep_hope_alive Premium Member]

i think you mean to say that you cannot predict the output given the chaotic nature of a car.

not understanding physics doesn't change it's existence. //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

a box in a trunk behaves like a bandpass enclosure. get the right combination of variables and it's going to be successful.

 

[keep_hope_alive Premium Member]

i went through the effort of cutting a pass-through in my rear seat, removed the hard plastic backing, cut out metal, and what's left is just some fabric.

 

[mlstrass 5,000+ posts]

No Terry Brock. Box to the rear of the trunk. Port and subs firing into the cabin. Not sealed off. Not closer to the cabin. The exact opposite of what physics tells us works. And btw those phase issues are broken down by frequencies. 60hz my be in phase, rest may not.

His design is much like a 6th order; using the volume of the trunk and opening size into the cabin as the front chamber/loading wall.....so I'd imagine some physics play into it.

x2 on KHA saying the biggest issue with the vehicles pictured is the beauty panel pretty much sealing off the sound waves from getting into the cabin.

 

[LosIsATool 5,000+ posts]

The only way your physics would apply to a trunk is if you take into account every angle, space, tire well, material, ect. Since you don't even know how the variables effect it than you can't apply anything. If it works it works. If it don't it don't. Unless you are building a numbers chaser you can get plenty of bass in the cabin with a beauty panel for most applications. I'm use to louder daily drivers and I still get plenty in the cabin. I don't have a beauty panel but my trunk is pretty sealed up. Only a small almost immeasurable gain when I fold the seat down. Your physics would say that's impossible. Why? Because physics don't account for variables. Physics also say doubling cone area is a 3db gain. How often does that happen

 

[keep_hope_alive Premium Member]

The only way your physics would apply to a trunk is if you take into account every angle, space, tire well, material, ect. Since you don't even know how the variables effect it than you can't apply anything. If it works it works. If it don't it don't. Unless you are building a numbers chaser you can get plenty of bass in the cabin with a beauty panel for most applications. I'm use to louder daily drivers and I still get plenty in the cabin. I don't have a beauty panel but my trunk is pretty sealed up. Only a small almost immeasurable gain when I fold the seat down. Your physics would say that's impossible. Why? Because physics don't account for variables. Physics also say doubling cone area is a 3db gain. How often does that happen

you are using the term "physics" incorrectly.

you should drop it and use "calculations", which is what i think you mean in most instances.

doubling of cone area is a 3dB gain when pathlength is equal, speakers are in separate enclosures, power to each is maintained, and phase interference doesn't play a role. it's simply logarithmic math adding two equal sources.

50dB plus 50dB is 53dB.

in equation form:

10*Log(10^(50/10)+10(50/10)) = 53.0103

 

[C1500martin 10+ year member]

Whatever happened to buying an amp a subwoofer and puting it in a normal square box and bumping...//content.invisioncic.com/y282845/emoticons/confused.gif.e820e0216602db4765798ac39d28caa9.gif