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**PeaveyBassist** · 12-13-2005, 02:33 PM

When the subwoofer plays, there is a sound wave that comes off the front AND the back of it. When those waves arent fully seperated from eachother, it is called infinite baffle. Basically like a giant box. Free air is when those 2 waves AREN'T fully seperated from eachother. Basically ploppling the speaker on the floor and letting it play. For a driver that isnt designed for that, it will be amazingly quiet because the waves are cancelling eachother out. To do the setup you want to do correctly, the trunk has to be airtight from the cabin and the speaker has to be inbetween the cabin and the trunk. Basically like the rear speakers on the rear deck. Make sense?

Will

**dude8383** · 12-13-2005, 02:41 PM

i see..so what you are kind of implying is that i should go for a box? or it would be easier to do a box because i wouldn't have to do all of the sealing or must i do that regardless? the subwoofer is going to facing the cabin, i have to seal the speaker from the trunk basically, or rather the foward wave? is that what you mean?

lol wow im totally stupid when it comes to this..

i will be dynamatting the the part which the rear seat covers. i dont know if i want to fully dynamat the trunk because thats a lot of fuckin weight..and i've got a 318is, i don't want to really make the car struggle.

**Digitalwave** · 12-13-2005, 02:44 PM

Boxes are superior to any setup similar to what you are doing. There is really no reason not to use a box... you can build them light and small.

Anyways, enough of jacking my thread :D

I've decided I'm going to use 3/4" MDF on my box... why go for a nice setup then sacrifice in any way? I need upgrade to 4ga power also.

**PeaveyBassist** · 12-13-2005, 02:49 PM

Originally posted by dude8383

i see..so what you are kind of implying is that i should go for a box? or it would be easier to do a box because i wouldn't have to do all of the sealing or must i do that regardless? the subwoofer is going to facing the cabin, i have to seal the speaker from the trunk basically, or rather the foward wave? is that what you mean?

lol wow im totally stupid when it comes to this..

i will be dynamatting the the part which the rear seat covers. i dont know if i want to fully dynamat the trunk because thats a lot of fuckin weight..and i've got a 318is, i don't want to really make the car struggle.

Reply to this later, I gotta get back to class ;) TJ, No need for 4 gauge when the battery is in the trunk and you only have 220w. 8 gauge will handle that NO problem what so ever.

Will

**Digitalwave** · 12-13-2005, 02:52 PM

It's a 4 channel amp, 440 watts total. I bought a half farad capacitor from Ken for $30 to help out. Think I can still get away with 8ga? I figured I could but it'd be cheap to go to 4ga and Ken recommended it.

**PeaveyBassist** · 12-13-2005, 04:06 PM

4ga would be "better" but not needed with 440w and that short of a power cable. Think about it, the power cable will need to be less than 5 feet long. Most people have to run it around 12-15 feet. There is much less power loss with the short run with the battery in the trunk.

Will

**dude8383** · 12-13-2005, 04:08 PM

lol i didn't mean to hijack the thread..i figured since we were talkin about boxes i might as well throw in some questions as well.. lol as you can see i am the total noob..

**PeaveyBassist** · 12-13-2005, 06:02 PM

Originally posted by dude8383

i see..so what you are kind of implying is that i should go for a box? or it would be easier to do a box because i wouldn't have to do all of the sealing or must i do that regardless? the subwoofer is going to facing the cabin, i have to seal the speaker from the trunk basically, or rather the foward wave? is that what you mean?

lol wow im totally stupid when it comes to this..

i will be dynamatting the the part which the rear seat covers. i dont know if i want to fully dynamat the trunk because thats a lot of fuckin weight..and i've got a 318is, i don't want to really make the car struggle.

Infinite baffle - in sound quality it is superior to almost all boxes. Everything I have read and/or heard about it is that its frequency response is very natural and keeps any peaks/dips to a minimum. The sacrifice with IB is the spl. Power handling is also drastically reduced. It won't be very loud at all, but its not meant to be. It's suppose to sound good. It is also more of a PITA because you have to make sure all the holes are sealed up (i.e. the rear deck on an e30). I would just do a box. But if you put the sub on the ski hole spot and seal up the rear deck with something it should work well. AFAIK the rear deck is the only thing in the e30 that needs to be sealed up. About dynamat... it is very overpriced. At lowe's they have roof sealer type stuff. I forget the name of it actually... I used it in my last e30. It is a roll that comes in 12" wide and its a shiny aluminum color. Almost all the sound deading in that type of material is the same. The real idea to dynamat is the give the panel more mass and control the resonances that the panels create. The stuff from Lowe's is MUCH cheaper and works all the same. Just tell people you used dynamat to say you did. ;) Sorry to jack the thread TJ, I just wanted to clear that up. dude8383, if you have more questions I would be glad to answer them in a PM.

Will

**Digitalwave** · 12-13-2005, 06:07 PM

That's fine, I got great info from this thread. I've decided to go with 3/4" MDF and I am probably going to fire the sub into the ski hole and mount the amp to the back side of the box. When I screw the amp into the box, should I put some silicone around the screws to make sure that there is no seal loss there?

**PeaveyBassist** · 12-13-2005, 10:50 PM

No need to put silicone around the screws. They will be fine.

Will

**Digitalwave** · 12-13-2005, 10:52 PM

Sweet. I alread have a piece of MDF attached to the floor of the trunk that the amp is mounted to right now. I am going to put metal L brackets on the box, and screw the box into that piece so the box is secure. Then screw the amp to the box, and viola.

**PeaveyBassist** · 12-13-2005, 10:55 PM

Perfect TJ. Good luck and post pics.

Will

**Digitalwave** · 12-13-2005, 10:56 PM

I definately will. I am really excited about this if you can't tell already.

**808BMW** · 12-14-2005, 12:39 AM

Originally posted by Digitalwave

I've decided I'm going to use 3/4" MDF on my box... why go for a nice setup then sacrifice in any way? I need upgrade to 4ga power also.

There we go.

You'd be surprised of the difference wiring can make. I use 4g on my 440 watt 4 channel amp. (although I have 10 going to the 800 watt sub amp... blah)

**Digitalwave** · 12-14-2005, 09:08 AM

If I do 4ga power could I leave the 8ga ground?

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