Building a box for lows.

[b34tBoX 0]

** Coles notes: 12" BTL (D2, loaded, Daily). Maximum Dimensions: 31" x 16" x 18". Want to hit the lows better. **

What is required to build a box specifically for lows.

Larger box? More/less port area?.........etc.

I had a BL last year, and have "upgraded" to a BTL this year.

I have two boxes that were used with the BL, one built by Thumper and another I did myself.

The PTS box is tuned to 32, I think mine might be tuned lower, not really sure. Used subwoofertools.com back in the day, and it told me it was 32Hz after displacement.

It's 27" x 16" x 18" with port 14.5" x 2.5" x ~33". 3/4 MDF.

When I put those dimension in RE Calculator it comes up with 29.81Hz (before displacement)

Both boxes were used with the BL, I've been using my box for the BTL, and it seems like the sub bottoms out a bit on the lows. <30Hz

Maybe I just had higher expectations when I replaced the BL with the BTL.

Mostly chopped and slowed music + rap with low bass is what I listen to while driving.

I don't know why, I prefer Drum and Bass music, but when I get in my car it's always low bass rap. Weird.

Edited May 30, 2010 by b34tBoX

[mikey5472 16]

Well i have had more success on the lows with more port area. My box now is tuned to 38hz with 16 sqin of [prt per cube and the lows are killer. I'd say tune it around 33 or 34 with 16 or so sqin of port per cube. You're bottoming out issue might be you're subsonic might want to make sure you know what you're box is tuned to and set you're subsonic accordingly.

[mikey5472 16]

I just did the numbers on you're box and it looks like( i might be really really wrong) but i came up with 11.15 sqin of port per cube @ 38.789hz. 3.25 cubes. Again i might be wrong but I am just trying to help.

[b34tBoX 0]

Well i have had more success on the lows with more port area. My box now is tuned to 38hz with 16 sqin of [prt per cube and the lows are killer. I'd say tune it around 33 or 34 with 16 or so sqin of port per cube. You're bottoming out issue might be you're subsonic might want to make sure you know what you're box is tuned to and set you're subsonic accordingly.

Hmm, strange. I always thought that if I want to hit the lows more, and shift the responsive curve to the bottom end. That it's done by tuning lower?

I could always try building a higher tuned box like you say and using more port area.

However, say I build a box like yourself tuned to 38Hz, wouldn't my subsonic need to be set a few frequencies lower, ie. like 35Hz?

[mikey5472 16]

You're subsonic should be set to what you're box is tuned to. From what i understand anyway. I cooked a bl by setting the subsonic to low. ( I think they said excessive clipping) Since then I have always set it to what the box is tuned to.

[b34tBoX 0]

You're subsonic should be set to what you're box is tuned to. From what i understand anyway. I cooked a bl by setting the subsonic to low. ( I think they said excessive clipping) Since then I have always set it to what the box is tuned to.

My subsonic I think was set WAAAAY too low. ~ 22hz.

I increased it to about 30Hz, and it seems like the lows are coming through ALOT more clear. Really had a chance to actually enjoy the music, it sounded really good.

BTW, I edited my post, the port length is around 33", I accidentally just wrote the length of one wall.

Now, I think for the hell of it, I'm going to build this box.

The internal cubic feet after woofer displacement x 16 is about equal to the port area.

[b34tBoX 0]

You're subsonic should be set to what you're box is tuned to. From what i understand anyway. I cooked a bl by setting the subsonic to low. ( I think they said excessive clipping) Since then I have always set it to what the box is tuned to.

My subsonic I think was set WAAAAY too low. ~ 22hz.

I increased it to about 30Hz, and it seems like the lows are coming through ALOT more clear. Really had a chance to actually enjoy the music, it sounded really good.

BTW, I edited my post, the port length is around 33", I accidentally just wrote the length of one wall.

Now, I think for the hell of it, I'm going to build this box.

The internal cubic feet after woofer displacement x 16 is about equal to the port area.

[Impious 1,476]

You're subsonic should be set to what you're box is tuned to. From what i understand anyway. I cooked a bl by setting the subsonic to low. ( I think they said excessive clipping) Since then I have always set it to what the box is tuned to.

Subsonic filters and amplifier clipping are completely unrelated.

It's ok to have the SSF set a little lower than the tuning. About a half octave is usually safe, but dependent on the subwoofer and enclosure.

[sefugi 166]

I you are relying on the RE calculator for all your specs you may want to compare it to some other builder programs. Since I've been on this forum I've heard from numerous posts that the RE calc. is not correct and when I've compared it to others I always find differences. My info may not be correct but you may want to look into it before finalizing your box specs. Good Luck!

[Sir-Lancelot 216]

Biggest problem with the re calculator is it does not take sub displacement into consideration so your box will be tuned higher then it says.

For a beginner, just tune slightly lower and it should be OK. Not perfect, but workable.

[imhungnurnot 9]

Biggest problem with the re calculator is it does not take sub displacement into consideration so your box will be tuned higher then it says.

For a beginner, just tune slightly lower and it should be OK. Not perfect, but workable.

or... you could do it right and say hey.. re says my box is tuned to 35hz with 2.5cuft... so instead of building that exact box.. simply extend one of the dimensions (preferably width so the port area is not compromised) to compensate for your sub displacement.. if you sub displaces .1 cuft or 172.8 cuin.. set up an equation 172.8=W*H*D.. wel you know H and D (use internal dimensions by subtracting 2*thickness of wood from external dimensions) and the W you find will be the length needed to be added to the width of the box..

After it's all said and done you will still have the desired box.. 2.5cuft at 35hz

i may have made this seem more complex than it really is.. but it works

Edited May 31, 2010 by Im Hung N ur Not

[b34tBoX 0]

New enclosure built.

Went with 31x16x18 external. (2.8cuft after displacement)

3.125 x 14.5 port area. @ 30Hz

L-port has two 45* bends instead of one 90* elbow.

It definitely does sound different.

Actually, due to the larger port area, I feel the air velocity has decreased, and overall, lost a few dB on output.

Can't seem to make my center console jump like before.

However,

The lows are coming through much clearer! The sub now seems to be matching up better with the front components at normal listening volume, and SQ has improved.

In conclusion, I feel that I will be much happier in the long run with the improved sound of the new enclosure, but lost some of it's "show-off power." (ie. peak outout)

I will be carpeting the new enclosure in a few days.

Edited June 13, 2010 by b34tBoX