my (1) SA-18 forth order build

[Bayuk89]

This is my old box, (2) SA-18's 10.5 net tuned to 32hz 127" of port.. i built this box when i had my 1500 watt rockville amp. Now that i have a twisted sounds 2.8k my old box is too big and port area too small for the 3600 RMS the amp puts out... i wanted to build something new, something ive never done before. With the help of trititcum, we were able to run my SA-18 D4 T/S parameters through a program and design a forth order based on my listening tastes. 3 cubes sealed 5 cubes ported, 100 sq" of port area with a removable port for tuning tastes.

I tuned the port to 48hz for starting off, with a removable port i can play with tuning at any time. Going from (2) 18" to just (1) 18" output isnt as loud (obviously) but the bass sounds much cleaner in gerneral and the box plays very well. Over all im very pleased with this experiment. It only cost me about $75 in material. Still playing with my SSF its currently set at 25hz may go down a few depending on how the sub behaves (less than an hour of play time)

[MrSkippyJ]

Looks good! I didn't think you needed a ssf with a 4th order bandpass though. Don't know much about them so I could easily be wrong!

[Joe X]

Based on the data I have for the SA-18 your ported box has no issues as long as you use your SSF, at least to the power the subs themselves can half safely take (about 2K for the pair.)

[Triticum Agricolam]

Looks good! I didn't think you needed a ssf with a 4th order bandpass though. Don't know much about them so I could easily be wrong!

Yeah, that's what I thought too, since the sealed chamber naturally limits cone excursion at low frequencies. The issue Bayuk ran into was when playing some bass boosted music, there was some REALLY low content in it, like 16 Hz stuff. The output of the box at those frequencies is pretty low, so he wasn't really hearing it, but the sub was trying to produce it none the less and it was pumping a lot of extra heat into the coil and things got a little stinky.

So lesson learned was while you may not need the subsonic filter for excursion reason, for thermal reasons it still may be a good idea.

[Bayuk89]

Based on the data I have for the SA-18 your ported box has no issues as long as you use your SSF, at least to the power the subs themselves can half safely take (about 2K for the pair.)

Thank you joeX I was honestly looking for a reason to build a new box and try something different, i wasnt happy with the build on my box. Bracing was minimal, i didnt double baffle, cuts werent straight. I still have the box and may re-work it and install it back in at some point.

[MADVIBES]

I like 4th order boxes the smaller the airspace on the sealed side the more cone control you are going to have, obviously the low end output will suffer however I think you will be fine due to the power you are running not being extremely high. The only downside I have ever seen with bandpass boxes is the ported chamber is very good at masking audible and mechanical distortion. If you get bored you could put the port on the other side of the box and seal the one side up, see how your output at different frequencies change.

[MrSkippyJ]

Looks good! I didn't think you needed a ssf with a 4th order bandpass though. Don't know much about them so I could easily be wrong!

Yeah, that's what I thought too, since the sealed chamber naturally limits cone excursion at low frequencies. The issue Bayuk ran into was when playing some bass boosted music, there was some REALLY low content in it, like 16 Hz stuff. The output of the box at those frequencies is pretty low, so he wasn't really hearing it, but the sub was trying to produce it none the less and it was pumping a lot of extra heat into the coil and things got a little stinky.

So lesson learned was while you may not need the subsonic filter for excursion reason, for thermal reasons it still may be a good idea.

Yeah that makes lots of sense.