new box false floor db gain?

[tesladude]

So in my jeep grand cheroke i have a 4cubic ft 32hz vented box for a sundown zv.4 15" running on a t1500. System sounds great as it is but my ****ty box i got off ebay is starting to creak and i am an experienced box builder so id like to plan somthing new.*

I plan to build a ~7 cubic foot box tuned to 27hz. Yes this will take up most of my trunk lol but i have a question. Originally i planned to wall off the zv.4 so it would be right about head height behind the rear center seat. My purpose is that i know for a fact a smaller internal car volume greatens db response by a ton but i am not going to wall it off after all, my other option is to create a false floor in the trunk reaching about the same height as the rear seats and having the subwoofer facing strait up and in the center of the floor (port by the window). My theory is that this will eliminate bass reverberating in the empty space around the box i have now along with stopping the rear seats from disapaiting sound. Not to mension the sub will not be raddling into my trunk but more pushing air in the only direction possible with little to disipate the sound.

I may have not described my plan very accurately, but i am prepaired to draw a picture in necessary. Would this potencially give me a sufficient db gain?

(Increasing box volume by 3 cubic feet and dropping my car's internal volume by about 10)

Click to read more...

 

[adulbrich 5,000+ posts]

It's hard to say without doing it.

I walled my truck the rest of the way and braced the roof recently. To the ear, it was louder with the windows down but quieter sealed afterwards.

 

[tesladude]

Do you have any idea about the change if box volume is increased? It puts less resistance on the sub so it should pe more efficient but i just dont know if it will be alot.

Also i THINK i read somwhere that more port area will increase efficiency but i don't see how it would do anything but decrease chuffing

 

[adulbrich 5,000+ posts]

Increased box size and port area usually do increase efficiency up to a certain point. That is true in most applications.

Will all this work be noticeable to you? I can't tell you for sure. It could make a big difference, or it could be minor and mostly in your head. I don't know how drastic you expect it to be

 

[hispls 5,000+ posts]

Do you have any idea about the change if box volume is increased? It puts less resistance on the sub so it should pe more efficient but i just dont know if it will be alot.Also i THINK i read somwhere that more port area will increase efficiency but i don't see how it would do anything but decrease chuffing

What year Jeep?

On paper that Sundown Z doesn't gain much going bigger than 4 cube and tuning lower certainly won't help. Generally speaking bolting the box down securely helps, and positioning the port to fire into a wall or corner is superior to port forward until you start walling at the B-pillar. In fact firing sub or port towards a hard surface or corner can provide big gains because the sound wave reflected properly will actually reinforce the wave coming from the source! Do a web search for the old Klipsh corner loaded horn home speakers, those were famous for applying that principal.

I have done extensive testing in late 90s Jeep Grand Cherokee and can offer suggestions if you have one of them, for later or earlier models my experience may or may not work out.

 

[tesladude]

I do know about those Klipsh horns actualy! darn things sound incredible.

I expect that moving the sub and port away from the corner will not help but I am hoping that cutting away the room around the box and bass potentially hitting the trunk will help take out areas in which bass will not be heard.

With the box in the trunk and sub/port facing the trunk, if you lean your head over the back seats it is incredibly louder of course than in the back or front seat. So my idea pretty much eliminates those areas of the car and this the bass intensity is moved.

Example of current box placement with tons of air volume in trunk

https://www.google.com/search?q=jeep+subs&source=lnms&tbm=isch&sa=X&ved=0CAgQ_AUoAmoVChMIi5Tmlez3yAIVCV0eCh1SRwxS&biw=1280&bih=703#tbm=isch&q=suv+subs&imgrc=1DSb8qEG2sA1AM%3A

Example of taking out all trunk volume and facing subs besides their port placement

https://www.google.com/search?q=tahoe+subs&source=lnms&tbm=isch&sa=X&ved=0CAcQ_AUoAWoVChMIu77Otuz3yAIVyKoeCh0x0Qd8&biw=1280&bih=703#imgrc=YJG5P--mVgphAM%3A

 

[hispls 5,000+ posts]

I do know about those Klipsh horns actualy! darn things sound incredible.I expect that moving the sub and port away from the corner will not help but I am hoping that cutting away the room around the box and bass potentially hitting the trunk will help take out areas in which bass will not be heard.

With the box in the trunk and sub/port facing the trunk, if you lean your head over the back seats it is incredibly louder of course than in the back or front seat. So my idea pretty much eliminates those areas of the car and this the bass intensity is moved.

Example of current box placement with tons of air volume in trunk

https://www.google.com/search?q=jeep+subs&source=lnms&tbm=isch&sa=X&ved=0CAgQ_AUoAmoVChMIi5Tmlez3yAIVCV0eCh1SRwxS&biw=1280&bih=703#tbm=isch&q=suv+subs&imgrc=1DSb8qEG2sA1AM%3A

Example of taking out all trunk volume and facing subs besides their port placement

https://www.google.com/search?q=tahoe+subs&source=lnms&tbm=isch&sa=X&ved=0CAcQ_AUoAWoVChMIu77Otuz3yAIVyKoeCh0x0Qd8&biw=1280&bih=703#imgrc=YJG5P--mVgphAM%3A

This was the loudest non--wall box I've ever had in a Jeep. Similar arrangements of sub up and port into that passenger side corner seemed optimum.

This here was my favorite sounding to date, subs and port up. Similar arrangements with subs up and port up (on the driver's side) all worked quite well.

Something like this with port to the side is about as good as anything. If you're metering experiment with pointing the port into the corner, otherwise sub up port to the side/corner has always worked out well in Jeeps for me.

 

[tesladude]

what about port and sub up both centered in the car? because the way I planned this, that is the only way

 

[hispls 5,000+ posts]

what about port and sub up both centered in the car? because the way I planned this, that is the only way

Neither of these performed terribly well for me.

 

[tesladude]

by terribly well you mean badly?