13 replies to this topic

[hosay]

Hi guys,

My current sub box is broken and I need to build a new one. The two subs I have are clarion SW1251 (350rms, 700max).

http://www.clarion.c...5294998621.html

The current box I was using was about 1.9 Cubic Feet total and It was a sealed design.

For my new box I was thinking of ported but I've been told that my subs arn't designed for ported. The thiele small paramaters are -

Revc (Ohm) 3.66
Fo (Hz) 29.891
Sd (sqM) 0.053913
Vas (Ltr) 67.924
Cms (M/N) 164.568
Mmd (g) 157.877
Mms (g) 172.273
BL™ 13.150
Qms 6.573
Qes 0.685
Qts 0.620
Levc 1.845
No (%)0.256
SPLo (dB) 86.103
Xmax (mm) 12
Vd (ft3) 0.06

The manufacturer recomends a 0.8 sealed box but I think a bigger size is appropriate. I was thinking about 1.5 cuf for each sub (a 3cuf box for both). I have also tried using WinISD.

Edited by hosay, 13 March 2012 - 03:07 PM.

[~Spyne~]

If going sealed, changing the box volume won't have a HUGE effect on response - as you make the box smaller, you will start to get a small peak around 70-80Hz.
Going purely by the specs posted, the sub isn't IDEAL for ported, though it could work. WinISD doesn't predict the smoothest response, but it is just theoretical, and a less than exact estimation at that.
It seems to be suited to a LARGE ported box at best, with a tuning frequency around 35Hz (the larger the box, the lower you can go with the modelled tuning frequency).
Probably looking at 2cu PER sub at a minimum with a tuning frequency around 36-40Hz.
If you want SPL, go larger (3.0cu per sub) with a higher tuning freq (40-45Hz), if you want SQ stay sealed. If you want ported SQ, try a different sub.


My 2c.

[hosay]

Yeh guy at my local car audio shop said you could hurt the subs going ported cause they will "overdrive themselves". I have no idea how when the manufacturer recomendation allows for ported designes. Also what would sound better ?

[VR028]

i just built a ported box for my 2 kenwood subs when they arent really suited for it. however a well, self built ported box will sound better than a cheap store bought sealed box.
despite common misconceptions my subs in their new ported box sound much more precise and tight as well as hitting lows they never could and being louder overall.

keep the port tuning low for sq and use a subsonic filter if possible and i think you'll be very happy

[hosay]

Yeh I'll tune it to about 32-36Hz, about 50L per sub.

[VR028]

thats exactly what i used, 50l per sub. thats after driver and port displacement though. i went with a 3" slot port tuned to 33hz. i modelled your subs in my enclosure on bass box and they will sound very good. relatively flat response and nice and deep. they also stayed within thier mechanical limits on 1000w rms right down to around 22hz. what amp do you have? if it has a subsonic filter use it

[hosay]

I have a 1600Wrms (1100Wrms at 2 ohm) with a subsonic filter. It is currently screwed and is under warranty. For the time being ill use a 540Wrms at 4ohm amp, both amps have subsonic filters. Whats the difference between slot ports and round port tubes. I was thinking of using 3" pvc pipe. Could you post the design of your sub as Ive never build a ported box before.

[VR028]

box is 900w 380h 450d with a 75mm port thats 600 long. overall i think its around 115l from memory and tuning is somewhere between 33-35hz depending on the volume of the port and subs.
make sure you use at least 19mm mdf and brace it internally where you can





i havent decided whether to paint or carpet it yet

[hosay]

yeh thats awsome. I'll try to build it soon. What program did you use to model it ? WinISD Pro ?

Actually can I use a 3" port tube (pvc pipe) maybe, about 25cm long for each sub ? This way I can build a seperate enclosure for each sub and may remove one sub if I think one is loud enough.

[VR028]

i use bass box 6 pro. a 3" port shows a pretty high vent velocity so you might hear some noise. theres alot of debate on this topic about what is an acceptable figure for vent velocity but in general you want to keep it low as possible.
using 2 3" ports per sub might be a better option, keep in mind they'll all have to double in length to 50cm

[hosay]

yeh il get bass pro 6 and check it out. I just wanted to keep the two subs in seperate chamber in case I wanted to power one only.

[RAD]

i use bass box 6 pro. a 3" port shows a pretty high vent velocity so you might hear some noise. theres alot of debate on this topic about what is an acceptable figure for vent velocity but in general you want to keep it low as possible.
using 2 3" ports per sub might be a better option, keep in mind they'll all have to double in length to 50cm

Lower vent velocity is good, and 3" is definately too small, but increasing port area TOO far to get vent velocity super low will tune the enclosure too high, and create loading issues. An easy rule of thumb for anyone out there, a 4" port will work fine for a street level 12" in 1.8-2cuft enclosure.

Seperate chambers will mean you'll have to have a larger enclosure overall, it's easier to tune a larger enclosure lower to say 35hz, than two smaller enclosures to 35hz.

[VR028]

Lower vent velocity is good, and 3" is definately too small, but increasing port area TOO far to get vent velocity super low will tune the enclosure too high, and create loading issues. An easy rule of thumb for anyone out there, a 4" port will work fine for a street level 12" in 1.8-2cuft enclosure.

Seperate chambers will mean you'll have to have a larger enclosure overall, it's easier to tune a larger enclosure lower to say 35hz, than two smaller enclosures to 35hz.

i dont think he's doing separate chambers, i think he's doing separate enclosures so he can take 1 out if he doesnt like it

[hosay]

Im thinking of a seperate enclosure for each sub, 2cuft each and port of 4" pvc pipe about 28cm long ?