I'm planning on adding an amp & sub to my 2012 Ford Focus and am probably over-thinking it. I'm primarily looking at a single SA-12 D4 but I'm open to suggestions.

• Yellow & white lines are sealed enclosures based on Sundown's specs and a 0.707 Qtc enclosure.
  
• Bluish & pinkish lines are based on my calculations and Sundown's specs for a ported enclosure.
  

I was originally leaning towards a sealed box since I was pretty happy with my previous sealed Pioneer 10s at 1cu ft ea & ~250W rms total. Now that I plotted out some graphs, I'm leaning towards the 1.8 cu ft box since it seems to have the best low end response.

FWIW, I plan on pushing it with ~500W rms and will set the subsonic filter to 15hz and the low-pass to 100Hz. I listen to a huge variety in music: electronic, rap, metal, classical. I'm not planning on entering any contests, I just want some better bass.

If you want "more" bass go with the ported. The SA line was designed for ported use but will work in sealed applications also; as you can see from the graph. What amplifier do you have? What is your budget so more suggestions can be added?

If you want "more" bass go with the ported. The SA line was designed for ported use but will work in sealed applications also; as you can see from the graph. What amplifier do you have? What is your budget so more suggestions can be added?

The amp I was looking at was the Alpine MRX-M50. As far as budget goes, I'd prefer to spend less than $300 or so on the sub (excluding box-building costs). Another constraint is that I'd really like to keep the box volume under 2 cu-ft so that I still have some usable trunk room.

Do you have the amplifier yet? If not what is your total budget. There are some SSA Dcon/Sundown Amplifier deals in the Store for great prices. Incriminator Audio also has a huge sale right now!

I was originally leaning towards a sealed box since I was pretty happy with my previous sealed Pioneer 10s at 1cu ft ea & ~250W rms total. Now that I plotted out some graphs, I'm leaning towards the 1.8 cu ft box since it seems to have the best low end response.

Dangerous to plot things without understanding what will happen in car. 24Hz is WAY too low to tune and seriously self defeating in car. For what you describe for music even 30Hz will cost you output.

Do you have the amplifier yet? If not what is your total budget. There are some SSA Dcon/Sundown Amplifier deals in the Store for great prices.

No I don't have it yet. I'll check those deals out, thanks. I'm trying to stay under $600 for sub & amp.

Dangerous to plot things without understanding what will happen in car. 24Hz is WAY too low to tune and seriously self defeating in car. For what you describe for music even 30Hz will cost you output.

I'm not sure what you mean, are you talking about the car's cabin gain transfer function?

Dangerous to plot things without understanding what will happen in car. 24Hz is WAY too low to tune and seriously self defeating in car. For what you describe for music even 30Hz will cost you output.

I'm not sure what you mean, are you talking about the car's cabin gain transfer function?

I was saying don't make a choice based on what you are seeing as you indeed left out the cars transfer function.

I was saying don't make a choice based on what you are seeing as you indeed left out the cars transfer function.

Right, that's why I'm asking here. :-)

Unfortunately I have no idea what the transfer function would be, other than it would probably be similar to other smaller sized sedans. Are you saying that I should stick with a ported box and just tune it higher, or that I should go with a sealed box? The SA12's EBP is 55ish, so it could really go either way.

You should definitely tune it higher. I did not notice the 24hz when looking at your graphs. I would start with 30hz and go higher. I believe Sundown recommends 30-35hz.

You should definitely tune it higher. I did not notice the 24hz when looking at your graphs. I would start with 30hz and go higher. I believe Sundown recommends 30-35hz.

The pinkish line is the 30Hz that they recommend, although that should've been for 1.75 cu ft. For the other one I just plugged the T/S params into the Butterworth D4 ported formula to get the bluish line. Here's the fixed version:

Really no need to tune as low as 30Hz for what you've described you'll be listening to.

Really no need to tune as low as 30Hz for what you've described you'll be listening to.

Hmm, I can think of at least 3 songs in my current playlist with bass that low:

• Method Man: Biscuits
  
• LL Cool J: The Ripper Strikes Back
  
• Nas: If I Ruled the World
  

Also, some of the electronic tracks I have definitely go down that low as well:

• Fatboy Slim: Acid 8000
  
• Goldie: Inner City Life
  
• Ju-Jajuba (probably the entire album)
  

And the FLACs I have of Metallica concerts and LPs do as well.

Or do you mean that it's overkill SPL-wise?

even music like you've listed does not have a much, if any, material below 40 hz. tuning higher give you more output for the frequencies you are actually listening to most of the time.

I'm pretty sure 35hz is the recommended tuning for the SA series.

I'm pretty sure 35hz is the recommended tuning for the SA series.

Well according to the Sundown site:

Enclosure Suggestions:

1.75 ft^3 ported tuned to 30 Hz -- F3 of 26 Hz

* Tune higher and use a smaller box for more SPL oriented setup (Use 1 - 1.5 cubes)

* Enclosure can be as big as 2.25 ft^3 with lower power levels

I think I do get the gist of what you guys are saying though. Even though there might be a few notes that low, I don't want to focus a huge boost to those frequencies. I just want to hear (or feel) those frequencies rather than have them be overwhelming. I'm not really looking forward to the work required to hone the port down a frequency at a time to determine the correct one....

Thinking back to the last ported enclosure I made, it didn't really sound well with faster double kicks and faster electronic music. I forget what that's called, transient response, or something. To be fair, that was like 15 years ago, and I didn't put nearly as much effort into it. I'm still not that confident of my skills. Looking at how relatively easy a sealed box would be to build, I think I'll just go that route. Thanks for all your feedback guys!

Building an enclosure for three songs each with a very few number of notes that low isn't so logical. If ALL your music had some ultra low content then perhaps. The compromise you are attempting to make is to limit output where the rest of your albums are recorded for those three songs. What happens when you get sick of them? Now you've built a system for something you don't even listen to.