Help & Ideas on Summer Subwoofer Project

[AmericanMade717]

Hello Everyone! I'm thinking about putting an amp and sub in my van this summer and started doing a little measuring today. I'm a little picky when it comes to sub locations and do not want limit my cargo space by putting a standard box behind the rear seat. An option I am thinking of is putting the box with a low profile sub and amp under the third seat with a removable plug so i can take it out when the seats need to be removed.

However the main option I am thinking of now is building a box for a low profile sub to fit in the back corner where the spare tire jack is located and then covering it with the stock jack cover with a hole cut for the sub and port for a factory look if the vans would have come with subs, similar to some SUV's. I took some pictures and measurements today and it looks like a 12" low profile sub will fit tightly in the area, a 10" should fit with ease. Another problems with this location is the amp will have a very tight fit in this location and I am worried about heat generation.

If you guys can share some of your sub and amp locations and what low profile subs and amps you guys are using. Would a 10" sub offer similar power to a 12"? I am currently thinking about buying Alpine SWR-T12 with MRX-M110 but my friend said the Rockford Fosgate Punch P35D2-12 and P400x1 would be a good buy. Thanks guys.

[Jasen]

you need to pick your sub so you know what the optimal volume is so you can figure out the exact dimension's of your box. if you not building an SPL van, you don't need to go nut's because in a sense, your sitting inside a sub box.

i went with a standard 12" in a sealed 1.35 cu. ft. down fire box 1/2 filled with polyester fill.


this it it mounted in the cabinet but not trimmed/hidden. i placed expanded metal at the bottom so nothing could get under it. it pounds pretty nicely when i want.

[AmericanMade717]

How does the sealed setup sound? I was planning on going with a ported setup for more thump. There seems to be a lot of math involved with the volume and port so putting it in the corner may have some drawbacks since size is an issue. I may put it under the seat so there's more room to work with the box design. Do you recommend using polyester? I heard it will clear up the bass a little bit.

[Jasen]

i wanted tight bass which i get with the sealed box, but crystal method will make my nose itch like i'm going to sneeze. the math is easy, but there are a bunch of sites online you can design a box for free.

[Jasen]

here's the prog. i used http://www.bcae1.com/spboxnew2.htm

as you can see in my pic, i mount my sub off center so you don't get a sound canceling effect. something i read about on the internet

[Coaster]

i have a JL 12wd4 sub and i have done a lot of experimenting with placement. i have a cargo van and use it for cargo so space is premium. i need to be able to haul full sheets of plywood as well as fill the entire van full of gear on different occasions.

the best place i have found is right at the rear doors firing "up", "at the doors" or "at the side". NOT firing into the van. in my situation this has to do with point of origin and wavelength

cancellation in these vehicles is incredibly complex and frequency dependent (what works for 100hz will not necessarily work for 90hz etc). basically at 100hz (the typical top freqs for subs, can be higher or lower but not much) the wavelength is roughly 11 feet long. below that the wavelengths get really long, i.e. 50hz is approx 22 feet long.

so say we have a 22 foot wavelength and we start at the rear door. how long is it to the front of the astro? lets say 11 feet for example (its different than that) the 22 foot wavelength travels the distance of the astro, bounces off the front (some energy is reflected, some absorbed, some refracted) and goes in reverse direction. at any point in the astro you are getting "more than one point in time" of this wavelength as it bounces around and either constructively or destructively combines.

obviously the width of the vehicle is highly relevant as well in terms of wavelength.

my advice is play with positioning heavily and see what works with what you have. also remember the amp does not need to be in the same location as your speaker.

my single 12" sub will vibrate the side mirrors to unusable levels. it will also vibrate the sides of the van something fierce. if i put the sub behind the drivers seat it still vibrates the mirrors and van sides but i get NO BASS. same energy but the waveforms combine destructively in that location with what i have.

i do pro audio for a living. but car audio is just something i have in my car. same principles but on a smaller scale

[AmericanMade717]

I'm really appreciating the help guys and these post are very helpful. I'm already starting to design a box for the alpine sub volume and thinking about placement. You guys have any ideas on where a good spot to mount the amp where it would possibly be hidden but at the least out of the way. I've seen people put them under the drivers seat however I have a power seat with a motor under there and it might not fit. I was thinking under the storage boxes on the driver side (same area as the jack except on the other side). I currently have my crossovers for my rear component speakers (pic below) mounted under there but there might be enough room for the amp to fit above them. If it's in a tight area where heat might build up I can wire a few cooling fans in to help keep the heat out.

[Jasen]

coaster expanded greatly on the sound cancellation all the way to the van itself

my amp/x-over location was a bit easier to do, but maybe it will spark any idea in your head.

this amp board slides into my cabinet behind the drivers seat. the built in fan's are supletented by a hi flow computer fan powered thru a relay triggered by the amp trigger off my HU.




my temp set up was basically the same, but it was a box.

[AmericanMade717]

After toying around with the volume calculator, there is no way that I am going to be able to fit a 12" ported sub in the location I had in mind. I am also starting to look at the Kicker CompRT as I have heard good things about them. According to the volume specs on Kickers website, I can def fit a sealed 12" in the location I was looking at or... the box may stick out 3 inches but I may also be able to fit a ported 10" in the back location. Decisions, decisions....

[Jasen]

when i built my system money was a little tight so i just tossed a 300 watt kicker comp in it for now. the 1k kenwood amp has been pounding on it for a couple years now. i'm happy with that little kicker

[AmericanMade717]

In terms of the sub and amp combo I think I am going to match sub and amp brands and of course get an amp that can match my subs RMS rating. Since I'm installing one sub I'm thinking about going with a mono amp.

[Jasen]

a mono D amp is designed to run a sub, that's what i run mine with.

[detailer4u]

I heave heard of some who have converted the rear doors into enclosures but it must be done properly of course because the enclosure makes or breaks the quality or lack of it that results when you're sending signal to it. If I were to do that, I'd gut the door and build the enclosure of MDF coated in fiberglass resin to help resist moisture - inside the door - then it would all be stealthy and you're not sacrificing any space inside the vehicle.
Being a detailer, I service some cool cars and I have seen some vehicles for a local NFL team who I service all the time several of their vehicles have enclosures with downfiring subs and they don't sound too bad....now keep in mind, I hear it while moving their cars around so I dont' know the effects of cranking it and if it will impede output but I've seen some amazing output and deep response from some surprisingly small downfiring enclosures under truck seats.
Heat is an enemy of electronics so mount that amp wherever(except upside down) but make sure it will be cooled properly.