sub airspace quesion

[traitorhound]

Is it bad to have too small of an air space for a sub?
here's the situation:

I have a friend with a mazda 3 hatch that we want to put 3 12's in there ported:

RE 12's (recommended 4.5 cu ported)

the useable space we have from what i calculated is 3.6cu (almost a foot less than recommended)
can i just make the port longer to tune it lower (as what was calculated in winisd) or is that a bad idea in general. i know its not like a sealed box where a too small or too big of a box can make something sound horrible but when you are tuning with ports i figured it was different

 

[1sty]

Box size has far more of an impact on the sound with a ported box then on a sealed. A sealed will typicl be able to be +/- 10% and no one will ever be able to tell the difference. Changing the port length may keep the tuning fq in check but but everything else will add up to lousey sound. I haven't run the numbers on a RE sub in this situation, so I do know for sure, but I can only imagine what the impact on the curve will be by reducing the total volume by 25%.

COnsidering the likely result and wasted amplifier power, I would use only 2 of the drivers instead.

 

[Poseur]

either that or just go sealed if you need to save the space. But youcould prolyl do the same output-wise with 2 ported.

 

[got wake?]

the volume tends to have a more drastic effect on the sound, as well as the efficiency with a ported system. just run 2 subs if you are that limited.

 

[traitorhound]

yea we are just gonna do 3 sealed after thinking it over. . .damn small hatches

 

[got wake?]

*cough* 2 ported *cough*

call RE, they'll recomend ported also

 

[traitorhound]

they'll take 700 rms without breaking fast? thats' my only concern. and the guy did buy 3 of em. . kinda like me compromising from 6 then to 5 and then eventually settling down to 4 8's

 

[got wake?]

just properly adjust the gains. it's not like you *have* to send 700 watts to the subs

 

[traitorhound]

ill ask the guy about it.. in the end its his car and whatever he wants to do with it.. ..700rms to each sub or 400 each to 3 subs

 

[1sty]

Whats the amp?
I would be sure to use some kind of sub bass filter to keep the fq below the tuning fq off of the subs.

 

[traitorhound]

its a kole/power acoustik 2400d . .it has its built in subsonic filter so that wouldn't be a problem

 

[bonesmp5]

not many like to do this but you can put all three in a open chamberd box thats ported --

right know i have 3 Punch DVC 12s in a sealed box with about 2,4 cubes -- open chamber --- the tech from Fosgate said i could get away with 3.5 cubes ported in an open chamber box -- and it would be a slot port tuned to about 32 or 38 -- sorry i dont remeber , been too long

 

[traitorhound]

not many like to do this but you can put all three in a open chamberd box thats ported --

that was the plan. . have all 3 in a shared chamber (easier to tune multiple subs that way) but the consensus here is htat too small of an enlosure for a ported box is bad. . .so either go sealed or use 2. . .my friend says he wants to use all 3. . im pretty sure it'll be loud enough since i know it already starts to hurt with only 2 sealed. .

 

[got wake?]

its a kole/power acoustik 2400d . .it has its built in subsonic filter so that wouldn't be a problem

i thought the RE series where all dual 4 ohm models? that would give a 1 or 4 ohm load at the amp with 2 of them. 900 rms to the pair would be ok, if you are careful with the gains.

 

[bonesmp5]

well -- you said you have about 3.6 cubes and i was told that 3.5 would be good for a ported open chamber with my DVCs -- even tho mine or the old DVCs i have to think that the REs are close to spec -- if they are,, then you can do a shared open chamber with one slot port for all 3 12s -- i would look into it before deciding on using 3 ow 2 12s ---- just my 2cents --- good luck Bro Billy

that was the plan. . have all 3 in a shared chamber (easier to tune multiple subs that way) but the consensus here is htat too small of an enlosure for a ported box is bad. . .so either go sealed or use 2. . .my friend says he wants to use all 3. . im pretty sure it'll be loud enough since i know it already starts to hurt with only 2 sealed. .

 

[traitorhound]

nah the re 12's want 1.5 cu per sub. . so 4.5 cu for a ported box

 

[bonesmp5]

but what im saying is -- when you use an open chamber ( subs share the air space ) you can get away with a little less cubes --- so you might not need all of the 4.5 ---
here is what my shared chamber sealed box looks like -- and i think its only about 2.4 cubes -- maybe a little less --
just a thought --- good luck

nah the re 12's want 1.5 cu per sub. . so 4.5 cu for a ported box