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Premium Member
The Bacon Hauler (‘12 Cop Charger)
10,448 Posts
There are way too many variables for anyone to be able to tell you what the best setup for your two 8” subs will be. You will have to do some experimenting and decide for yourself.

However, there are some general things that can be kept in mind to guide which orientations to test first so you don’t waste time on configurations unlikely to yield satisfactory results.

1) the back seat will absorb a lot of the subs’ output before it gets to the front of the car to be heard/felt.

2) sub placement and orientation in the trunk will greatly affect the perceived output at the driver’s seat.

3) unless they are some ultra-high quality, really expensive subs, and enclosed in a well made box built to specs specifically for them, you will struggle to get satisfactory results from two 8” subs in the trunk of a Challenger.

In other words, based on my experiences trying to add some bass to these Dodge cars and on the info you’ve given so far, I think you will need to get everything with respects to the subs’ box, its placement, and its orientation just right if you want to make two 8” subs work in your trunk.

Here are a couple things I would say to keep in mind:

- Placing a sub box against the back seat and facing it backward can yield up to a 3 dB increase in perceived output thanks to the cabin gain of the trunk.

- you should amp the hell out of the subs; the more, the better; if you don’t exceed the subs’ recommended RMS wattage by at least a bit, you’re making it harder to succeed here.

- prefer a ported box over sealed for this application; and if you do go sealed, you better amp the subs @150% their recommended RMS if you hope to succeed here.

- the side panel placement you mention can work, but it means starting out at a disadvantage, so you better come with a LOT of amp to get it done.

- facing two subs at each other can work if you have their phase correct, either on the amp or by switching the speaker wires feeding the subs.

- having plenty of high-quality, correctly crossed-over midbase will help strengthen the bass from the subs. Adding a good sub setup to an otherwise crappy system with little to no midbase picking up where the subs’ bass notes leave off will hurt the bass from the system a great deal.

If your rear seat back is in the 60/40 split bench style, pulling the passenger side (40 from 60/40) down to allow full access from trunk to cabin will significantly increase the bass notes’ intensity originating from inside the trunk.

Premium Member
The Bacon Hauler (‘12 Cop Charger)
10,448 Posts
Well to be honest, I've never put this much planning into my systems. And of course the sound quality reflected that.

I've always done sealed for simplicity and size. Generally what I remember was to go ported it would result in a much larger box.
I, along with many others here, found myself in this exact same situation at some point in the past. Nothing wrong with being in this situation, but realizing its limitations and then working to overcome them is the main thing to work toward.

My wife doesn't care about the stereo ; it's the dollar figure attached to the planned upgrades she objects to.
Much like trying to make the SXT as fast as an R/T, it can get real expensive really quick trying to make a couple of 8" Kicker subs in a sealed box sound as good as a JL Audio 10" in a vented enclosure (for example). And what's worse, there more ways to mess it up than there are to succeed in such ventures.

There are 2 ways to proceed:

1) continue down the current path with the current hardware, spending money wisely and choosing as high quality products as possible, and doing as much of the labor as possible to fabricate anything that it's possible to fabricate.

2) punt from this drive and sell the current hardware for what you can get for it, buy (used) better hardware and start from there making it sound good.

#1 will be more financially agreeable, but it will be difficult to achieve the sound from the resulting system that you likely want to have at the end.

#2 will be less palatable, financially speaking, but you should have a much easier route to getting the quality of sound you are looking to end up with.

I've taken both approaches, relatively recently I might add, and I cannot say one way is demonstrably better than the other. It's all about managing expectations really. Just like with the SXT to R/T quest, you have to keep in mind what the possible results are of any upgrade in hardware, and do not take any long shot gambles or reckless experiments with unknown/unproven hardware.

For #1 to work, you will have to build a vented enclosure, and you'll need to do a very good job of it. That means lots and lots of math beforehand to come up with a cut-sheet that leaves nothing to chance. In fact, and I am serious here, I would suggest buying a couple 2'x4' sheets of OSB and just building some practice boxes to get the hang of it first before attempting the final build.

There are lots of little things about building a good, solid vented enclosure that you won't know, and no one can tell you, but need to be done if the box is going to be a success. Practice makes perfect here, and experience matters. That's why I suggest the practice boxes - that's the only way to learn what to do and what not to do when you have to have a 27" long port but the box is only 23" wide at its longest dimension.

I'm not just whistling Dixie either. I build sub enclosures about as well as I fly airplanes...which is to say, not very well. At least I didn't use to (build boxes), but now that i've got a few under my belt, most of which were ugly failures, I know what i'm doing to some extent.

My last enclosure I built was one which was meant to house my JL Audio 10W3v3-4, and I built it to JL Audio's published specs...kinda. Their specs wouldn't fit in the trunk of my Charger, so I had to modify the dimensions a little. I maintained the spec'd volume and port area though, and while it took me a lot of time and energy, I managed to build a box which has that sub rocking and rolling like i didn't expect. It's ugly as sin, but it works and works very well.

It's the 5th box I have put that sub in by the way, and the 2nd one I've built. I built a sealed one and then tried several pre-fab ported ones, all sounding better than the last, but none compare to this one I built to specs. Not even close.

My amp is a mono Kenwood, rated at 500w rms. They were single voice coil and I wired them to give a 2ohm load to the amp.

I just measured my old box - it's pretty small. Again, trying to save space. Looking like about half cubic foot per sub, the bottom recommended spec. So I'll have to measure up and see how much space I can reasonably use in the trunk.
There is no replacement for displacement, just keep that in mind. It holds true for engines and amplifiers. I'm not saying you should buy a bigger amp. You need to provide enough power to the sub to keep it in its butter range, and the amp should not be maxed out all the time on a 13.8v charging system either (advertised wattages will be for 14.4v usually; that's an important and sneaky discrepancy to keep in mind if shopping amps).

Finally, keep an eye out for used equipment. Folks who are upgrading to bigger and better things are going to sell their older and less grand stuff, hopefully at a steep discount. But their older and less grand stuff may be just what you're looking for, and that goes toward both #1 and #2 above.

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