[bmw325i]

Originally Posted by Montecristo

The box calculator site only gave a wedge as an option for two boxes, how do I calculate just a rectange? 335i is pretty square in the back

Also, is it exactly 14 inches in the back? Because the box recommendation for a sealed 12 is 14". Think it would fit snugly or just barely not fit?

Just do 14Hx36Wx14D using 3/4" wood with a divider in the middle that will be 1.53 cubic feet per sub. If you are doing a double baffle in the front add 3/4" to the depth for the second layer of wood. My box is 14" tall and 36" wide and it is a tight fit.

[Montecristo]

Originally Posted by bmw325i

Just do 14Hx36Wx14D using 3/4" wood with a divider in the middle that will be 1.53 cubic feet per sub. If you are doing a double baffle in the front add 3/4" to the depth for the second layer of wood. My box is 14" tall and 36" wide and it is a tight fit.

That makes telling the installer simple . What is a double baffle?

[bmw325i]

Originally Posted by Montecristo

That makes telling the installer simple . What is a double baffle?

Sometimes people use 2 layers of wood in the front so you have more wood to screw the sub into. My setup has 2 front baffles but I used the second layer of wood to flush mount the subs and seal the trunk.

[Montecristo]

Originally Posted by bmw325i

Sometimes people use 2 layers of wood in the front so you have more wood to screw the sub into. My setup has 2 front baffles but I used the second layer of wood to flush mount the subs and seal the trunk.

What so you mean by using the second layer to seal the trunk?

[bmw325i]

Originally Posted by Montecristo

What so you mean by using the second layer to seal the trunk?

Look at my pictures in the second post. The front baffle is cutout to the shape of the trunk opening and I also flush mounted the subs. The box is actually a prefabbed box that was the exact dimensions I wanted. I used 1/2" neodynium magnets to hold it in place.

[Montecristo]

Okay got it. So to recap these are all the parts and materials I'll need and/or have:


- 2 Fi Q 12's fully loaded without internal lead
- 1 sundown 3500D amp
- 2 xs power d4800 batteries
- Sealed box using above dimensions
- Technic harness
- RF amp power kit
- Extra terminal rings
- Short RCA cable
- Extra ground cable
- However much 1/0 gauge I need if I want to replace any stock

Sound good?

[bmw325i]

Originally Posted by Montecristo

Okay got it. So to recap these are all the parts and materials I'll need and/or have:


- 2 Fi Q 12's fully loaded without internal lead
- 1 sundown 3500D amp
- 2 xs power d4800 batteries
- Sealed box using above dimensions
- Technic harness
- RF amp power kit
- Extra terminal rings
- Short RCA cable
- Extra ground cable
- However much 1/0 gauge I need if I want to replace any stock

Sound good?

Yep that should be all you need.

[Montecristo]

Hello...again, unfortunately I have not been able to complete this setup because I was emergency deployed and I am just now coming back . I have also come back with another question!

I believe I can do it myself, using this guide: http://www.e90post.com/forums/showthread.php?t=87130

My question is, at what point do I use the technic harness for the install listed in Dr.phuOnger's post and what am I not doing because I am utilizing it? I see he is using a different method. I think after I know this I can figure out the rest (running 1/0 gauge to the alternator). Thanks again for all your help !

[bmw325i]

Originally Posted by Montecristo

Hello...again, unfortunately I have not been able to complete this setup because I was emergency deployed and I am just now coming back . I have also come back with another question!

I believe I can do it myself, using this guide: http://www.e90post.com/forums/showthread.php?t=87130

My question is, at what point do I use the technic harness for the install listed in Dr.phuOnger's post and what am I not doing because I am utilizing it? I see he is using a different method. I think after I know this I can figure out the rest (running 1/0 gauge to the alternator). Thanks again for all your help !

Unplug the amp and plug technics harness in between the stock amp and stock harness. It will add a line output converter and it also has the remote turn on wire. Your RCA cables plug into the line output converter.

I wish someone would make a high output alternator for the e90

[mathematics]

i would imagine that a higher output alternator would have some negative effects on the computerized charging system, correct? that would be nice, though.

[Montecristo]

Originally Posted by bmw325i

Unplug the amp and plug technics harness in between the stock amp and stock harness. It will add a line output converter and it also has the remote turn on wire. Your RCA cables plug into the line output converter.

I wish someone would make a high output alternator for the e90

For my e92, would a xs d4800 still fit as a replacement for my stock battery? I noticed you are using an e90, not sure if there is a size difference. Same question for the sizes of the trunk.

Also, how do I hook up a second battery??

[bmw325i]

Originally Posted by mathematics

i would imagine that a higher output alternator would have some negative effects on the computerized charging system, correct? that would be nice, though.

That's what I've been wondering. On any other car I'd have one custom made but I don't know if the computer will like it.

[bmw325i]

Originally Posted by Montecristo

For my e92, would a xs d4800 still fit as a replacement for my stock battery? I noticed you are using an e90, not sure if there is a size difference. Same question for the sizes of the trunk.

Also, how do I hook up a second battery??

Group 48 is stock size. Wire a second battery in parallel. Positive to positive negative to negative.

[mathematics]

i would add an isolator

Originally Posted by bmw325i

Group 48 is stock size. Wire a second battery in parallel. Positive to positive negative to negative.

[Montecristo]

Originally Posted by bmw325i

Group 48 is stock size. Wire a second battery in parallel. Positive to positive negative to negative.

Okay that sounds easy, thanks!

[Montecristo]

Originally Posted by mathematics

i would add an isolator

What does that mean?

[bmw325i]

Originally Posted by mathematics

i would add an isolator

That might not be a bad idea actually. I would even wire in a battery tender to top off the batteries every now and then.

[bmw325i]

Originally Posted by Montecristo

What does that mean?

[Montecristo]

Originally Posted by bmw325i

Very informative video, thanks for linking it! And that does make sense. I will look into it!

Concerning the enclosure....

1. What were the reasons you gave me the specific dimensions you did?
2. Should I get a custom box to those dimensions?
3. Or should I get something prefabbed that is close, such as
http://www.sonicelectronix.com/item_...va-MDFD12.html
4. How does the volume in a sealed enclosure affect the output of the woofers?
5. What should I be looking for in an enclosure to make sure it is high quality?


I have done some research to all of this, but would like your opinion on those questions...thanks !

[bmw325i]

Originally Posted by Montecristo

Very informative video, thanks for linking it! And that does make sense. I will look into it!

Concerning the enclosure....

1. What were the reasons you gave me the specific dimensions you did?
2. Should I get a custom box to those dimensions?
3. Or should I get something prefabbed that is close, such as
http://www.sonicelectronix.com/item_...va-MDFD12.html
4. How does the volume in a sealed enclosure affect the output of the woofers?
5. What should I be looking for in an enclosure to make sure it is high quality?


I have done some research to all of this, but would like your opinion on those questions...thanks !

1.5 cubic feet per sub is the larger size reccomended by fi for a 12" q sealed. You have 36" width and 14" height to work with so I adjusted the depth to get close to 1.5 cu ft. per sub. My box was prefabbed but I spent a good amount of time finding one exactly the size I wanted, tuned fairly low. Just make sure it's made out of 3/4" wood. You could also build your own box I was going to but got lazy this time around.

[Montecristo]

Originally Posted by bmw325i

1.5 cubic feet per sub is the larger size reccomended by fi for a 12" q sealed. You have 36" width and 14" height to work with so I adjusted the depth to get close to 1.5 cu ft. per sub. My box was prefabbed but I spent a good amount of time finding one exactly the size I wanted, tuned fairly low. Just make sure it's made out of 3/4" wood. You could also build your own box I was going to but got lazy this time around.

So why try to get the highest volume you could out of it? Is that better? And tuned fairly low you say, I thought that was only for ported?

What is polyfil and should I put it inside my box?

[bmw325i]

Originally Posted by Montecristo

So why try to get the highest volume you could out of it? Is that better? And tuned fairly low you say, I thought that was only for ported?

What is polyfil and should I put it inside my box?

A larger sealed box will have more output and play lower than a smaller sealed box. My box is ported which is why I mentioned the tuning alot of the boxes I was looking at had very short ports. Poly fill is supposed to make your box sound larger I've used it and didn't notice much of a difference try it for yourself.