View Full Version : Design Help For w7 box

11-15-2011, 09:50 AM
I have a friend who has a 2006 Dodge Ram Daytona with an extended cab and he is dead set on throwing a massive sub in his center console. He would like to go with a 13w7 if it will fit due to their low frequency response no matter how much i try to convince him otherwise lol he says he wants to try a bunch of different brands top of the line stuff to see how they all sound. I have the specs for what the ideal jl box is but my question is this......... If i built a box for him with the sub up and the port firing down so it was bouncing off the floor how would that sounds? There will be a plexiglass cover on top to protect the sub from any damage. When my frien d kurt guenther had his shop he built me a center console box with 2 1508's in it with the plexi on top except he had the port pointing back because it was a single cab and that is still my favorite setup to this day, People always asked to c behing my seats because they thought i had more subs back there, i was doing right around a 139.3 at 37 hz which was pretty good out a couple 8's and a cheap amp. JUst wanted to get your thoughts on where the port should be pointed and how you think this will sound? Thanks guys

Moble Enclosurs
11-15-2011, 02:44 PM
Well, the plexi will help two ways.....it will help lower audible distortion from the drivers to the listener (but always try to keep that down as much as possible anyhow), and will help in the response smoothness as well. This is because it actually acts to diffuse to sound and send it azimuth into all directions. It acts as part of the design, and not just a protective plate. it's like a 4th order without the access panel, lol. It increases HF response from the driver and if the design is tuned low, it can smooth the response.

Now, regarding port placement, this is not a direct answer, but if the cabin is small enough, it can virtually be placed in any direction with minimal changes in the audible sound. Usually, when the sound reaches the cutoff point of the response, the phasing is quite different, and can cause a helpful filter-like drop-off on either side fo the usable response passband. In this case, and many others, it is wise to verify the phase of the design when constructing it's acoustical output to ensure the phase does not change more than 90 degrees from the tuning frequency of the design. This is usually the end points of the designs passband and verifies its usable response. Anything outside of a 90 phase change, will have timing issues and sound more muddy than directive response frequencies, therefore decreasing quality and causing possible cancellation, though the cancellation is usually in the higher range of frequencies above 80Hz.
Most will say, face it to the rear and you'll be fine. While this is partially true, make sure that if you design it that way, that the phase is smooth from the tuning frequency down to the LF cutoff point and above the tuning as well. Any given driver will have a potential to create a 1.5 octave passband for a response, and the lower the tuning, the smaller the band, making it more narrow-banded, so be careful not to tune it too low as well. A 25Hz cutoff will give you a usable passband of 25-62.5Hz for example, and a 35Hz cutoff will give you a usable passband of 35-87.5Hz. That is a 15Hz band increase from adjusting to a higher cutoff frequency. It can make a difference. Other than that, you should be good.
Hoe that helps!