Dodge Challenger Forum banner

1 - 9 of 9 Posts

·
Registered
Joined
·
252 Posts
Discussion Starter #1
Doesnt seem like there are to many bass heads around here so I will welcome myself. LOL Not a SQ guy so the factory mids/highs will be left in place for now, however after a couple weeks of ownership and pretty much done with the performance part of my build I want to glass a box into the floor around the battery and add a subwoofer. I am thinking of sticking to the kicker theme and going with a L7 12" sub. I recently came from the Corvette community and left behind a Z06 with a full build and a L7 15". It was more for looks at shows then performance as the sub clearly lacked the air space required to perform properly but dont get it twisted the thing still made your nose tickle. LOL I had played around with both a kicker 12" and 15". While the 15" got the WOWS i was looking for, the 12" just sounded great. I was only working with about 1.8 cubic feet so it makes sense. Not sure what I am going to do quite yet but should be interesting so stay tuned. LOL

On a side note is the factory sub/encloser and amp worth a shit, and where is the amp physically located. Thanks guys
Teddy
 

·
Registered
Joined
·
402 Posts
Here's mine!

 

·
Registered
Joined
·
955 Posts
On a side note is the factory sub/encloser and amp worth a shit, and where is the amp physically located. Thanks guys
Teddy
No. The amp is probably located under the steering wheel to the left side. Remove the lowest part of the dash/footwell to see it. It's all one big (small) amp for the whole system.

If you're interested in maximizing your bass output (as opposed to a more showy install) let me know. I don't do SPL personally, but I know how to do it in these cars. There are some rules of thumb about how to use the trunk space to achieve the best output levels, and as you probably know the installation is more important than the equipment.

EDIT: Hey I found a pic of the amp from my build:

 

·
Registered
Joined
·
252 Posts
Discussion Starter #4
Sactown- I seen you posts and install. Very impressive to the ears but not my style. I want cool points for my install which is why I am building up the floor. I have a box that I can just "toss" in there with 2 P3 Power Rockford subs but thats to easy. LOL

Ceri- I was under the assumption there were 2 amps. One that ran the mids/highs and another dedicated to the 10". Is that not the case? Well if I have to leave the amp in there I am fine with that but the box is coming out. I already gave my installer a call. LOL I am VERY interested in maximizing my bass. Please do tell. :)
 

·
Registered
Joined
·
955 Posts
Ceri- I was under the assumption there were 2 amps. One that ran the mids/highs and another dedicated to the 10". Is that not the case? Well if I have to leave the amp in there I am fine with that but the box is coming out. I already gave my installer a call. LOL I am VERY interested in maximizing my bass. Please do tell. :)
Could be. They changed the audio options on a yearly basis. There's three different Boston Acoustic systems, at least 2 kicker systems, some unlabeled OEM options, etc. Most of them run off one main amp under the wheel. I'm not sure what you've got, or where the amp(s) might be.



As far as the bass tricks go, I might have jumped the gun. If you're already set on your mounting location (wheel well fiberglass box) then there's not too much to add to that. It's an efficient use of space, but not the best for an SPL build. Some things you can still benefit from though.

Sound deaden the trunk lid. Take the interior fiberboard/carpet stuff off the lid's interior and lay down a nice thick layer of mat. Then go over that with some mass loading vinyl (MLV). The truck lid's fit from the factory is notoriously crap, but fixable. Here's the process to fix it. Get an idea of how much you need to correct it (looking at the tail light from behind). It may need to go up or down. Usually down.

Here is a picture of the trunk. Nevermind the crappy amp rack I had there. I'm already not happy about it's replacement.



Take the carpet off that left side (in the picture). That's the side you're standing over when you're looking down on the trunk from the back. It's secured by 5 plastic pop-rivets. Take it off. This exposes the latch. Loosen the 2 torx head bolts so that the latch is loose, but still attached. Slide it up/down according to your best judgement from the tail light level earlier. Tighten it down properly with pretty good torque so it doesn't come loose in 6 months from super-bass-out. Deaden the rear wall (the one the latch is attached to), add MLV (optional), and reinstall the carpet. If you add MLV you might need new longer pop rivets, but it's worth it for an SPL install.

Now adjust the hex head plastic caps (seen in the bottom left of that picture above) all the way up. Carefully attempt to close the trunk. It's going to be much heavier now with the deadener and MLV, so don't let it slam down on the plastic hex caps or you could break them. Adjust the hex heads down a bit, and reattempt to close it. You want to make it so it just barely clicks closed, and may require a bit of force to fully engage the latch. Otherwise it will vibrate with the bass, especially with a sub pointed straight up at it. Vibrating panels = wasted acoustic energy = less SPL.

Then go ahead and strip the rest of the carpet out, deaden it all with at least 50% coverage, and add as much MLV as you're comfortable with. MVL is heavy and expensive, so it's understandable if you don't want to weigh the car down too much. On the other hand, the more you add, the more focused the bass will be into the cabin of the car and the higher the SPL you'll be able to achieve.

Ditch the layer of fiberboard underneath the rear deck speakers. It will make noise when the bass is getting moderately loud. Deaden the rear deck. MLV optional. Finish it with something else (automotive carpet, etc.). The stock material is just rigid enough to make a whole bunch of noise when the bass starts getting up to reasonably loud levels. It sounds a little like a blown voice coil when it starts flapping. I'm not setup for SPL and my pair of 12W6s on 500 wRMS make this thing go nuts well before clipping my Minotaur. I've been meaning to remove it, but haven't gotten around to it since I don't crank the bass very often.

Make sure the box, wherever it ends up, is very well secured to the car. Any tiny little movement from the box (usually weighing something like 30-60 lbs) is a whole lot of acoustic energy wasted. If you can feel the box vibrating when you're done, you're not done.



I don't know if a wheel well box in this car is horrible or just bad. It's not good from an SPL perspective. It's merely convenient. If that's what you're after, then it's a perfect solution, game over, party on. If you're not set on a mounting location yet, then here's a little diagram of some other mounting options I worked up recently for another member:



(a) is forward facing, toward the cabin
(b) is rear facing, toward the rear
(c) is side facing, toward the interior

Good (a) shows two separate isolation walls to seal the trunk off from the cabin. These would need to be awesome walls. Very few gaps and with deadener surrounding the edges. The dead space in between works sort of like those double pane argon windows you see in newer houses. It helps isolate "outside" (trunk) from "inside" (cabin), except with sound energy instead of thermal energy. The closer to perfect you could make it, the better the end results. Best case scenario this is the 10/10 setup.

Bad (a) is forward facing without isolation walls. The sound wave that heads backward into the trunk will bounce back and cause phase interference with the forward sound wave. This leads to nodes/nulls/deadspots that are frequency dependant. It gets unpredictable with the end result and if you're unlucky enough to hit a null right around the listener position you'll hear a noticeable drop in output. This setup gets a 3/10.

Bad (b) suffers from the same problem, but with the subs facing backward, the frequencies for the null points are higher. How much higher depends on how far from the back of the trunk the box is. The quarter wavelength of 80 Hz is about 3.5 feet (here's a chart showing full wavelengths: Frequency - Wavelength - Period Chart). If you line up quarter wavelengths just right you can tune for a one-note SPL machine and use the car as a sort of "port" for the whole system. It can create a constructive interference pattern that causes a positive node at the microphone position. That's a bit on the advanced side though, and not too relevant here unless you want me to get into it. It's unpredictable in a car, especially if it's not very well sound deadened. In short, this setup gets something like a 5/10.

Good (b) on the other hand puts the sub faces as far toward the back of the car as possible. Some people used to mistakenly say this was extra time for "the bass wave to develop". That's bogus pseudo-science crap. What it does do is not allow for bad interference patterns to ruin your flat bass response. Here's some further reading on most of what I've been talking about to now: RealTraps - Bass Waves in the Control Room. Good (b) gets 8/10.

Good (c) is split fiberglass boxes in the corner pockets, with an angle to them. This can be unpredictable too, and cause nodes, but the angle attempts to compensate for that. The principle here is the same principle behind detonating atomic bombs hundreds of feet above the ground, instead of at ground level. The shockwave's reflection off the ground combines with the shockwave still coming from the bomb blast causing a linear explosion that has more force than either individually. Sort of like how supernovas are portrayed in film (with the explosion going outward in a ring instead of a bubble). This is also an example of "corner loading", which is a popular term in home audio. It's peaky, which can be good for SPL if you design the port correctly to take advantage of these peaks, but it's not a musical install. That's what good (c) has going for it. Good (c) only gets about a 7/10 though because the exact opposite can happen too depending on the frequency, and because of it's unpredictability.

Bad (c) is with the subs facing each other. The corner loading is reduced, and the phase cancellation becomes a bigger problem. Unpredictable at best. 5/10 and risky when you're talking about the time investment in fiberglass.

Where did I lose you? :)
 

·
Registered
Joined
·
38 Posts
Great info Ceri. My sub is the "Bad B" position. How would some one use their trunk in the "Good B" postion? And how would just 1 sub due in one of the corner pockets?
 

·
Registered
Joined
·
955 Posts
Great info Ceri. My sub is the "Bad B" position. How would some one use their trunk in the "Good B" postion? And how would just 1 sub due in one of the corner pockets?
If by "use their trunk" you mean for groceries, golf clubs, etc. then the answer is you don't. Or you make the box removable for when you need the trunk. It's definitely a trade off. All those X/10 ratings are for maximum effect for no compromises SPL with a trunk mounted box. They're not always going to be practical. How far you're willing to go is up to you. I will say though that having a box that's very well secured will be far more important than the position. Don't go pushing it back to the back of the trunk without firmly securing it somehow. Any box movement caused by the movement of the subs is a HUGE waste of acoustic power. They aren't even in the same ballpark. Besides it's dangerous.

I would guess that one sub in a corner pocket will still benefit from angling toward the front some, but the cancellation issue isn't a problem. So overall, probably about the same output as if you did 2 subs in a "bad (c)" setup keeping power constant, but less frequency dependant nodes to deal with. More predictable behavior. It's really tough to generalize when you get into the finer details. I was just trying to offer some big picture thoughts/comments. Where SQ is concerned (flat response being the goal), the fewer the cones you can get away with, the better. For SPL you just deal with the peaks and valleys and target your best peak for your burp note. If you want to really maximize it, you might build a basic flat modeling test box first and then come back and do a triple braced ported box for the peak frequency from that mounting position.
 

·
Registered
Joined
·
252 Posts
Discussion Starter #9
So went and seen my installer last night and went over the build. Pretty simple and to the point. Yanking out the compressor and styrofoam piece, fiberglass in a box, and build it up about 3-4". Wrap the box in suade like the interior and make the beautyboards with black vinyl with some red stitching of sorts. The subs I decided to go with are the new Rockford Fosgate shallow P3 4 ohm subs. Going to run 3 10" subs and get 2.67 ohms out of a Rockford Fosgate Punch BD1000.1 I ordered it all today. Sound look great and sound good as well. Stay tuned.
 
1 - 9 of 9 Posts
Top