separate the chambers or not?

separate or not to separate when making an dual enclosure? I have heard always separate them, but also a few times that it really doesn't matter? which one and why?

Separate if you're running the woofers in stereo (not mono). Usually you'll be running the woofers in mono though. In that case it technically doesn't matter as long as the woofers are identical models. On the other hand the divider does act as a brace which may be needed on larger spans. Also, if one of the woofers blows you can tell which one. Otherwise the working woofers will continue to push the blown woofer like a passive radiator, giving it the appearance that it is still working.

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plus after one of the woofers blow, you will be playing one woofer in a much larger box because it is only for one working woofer and it could very easily damage the other woofer too if your playing it at high volumes.  If you put in a seperator, you wont have to worry about that happening

im doing an enclosure for 3 10's. im running it in mono, but heres my question. 2 of the subs are 4ohm and one is 8ohm( i did that so i could wire it to 4ohms for my amp) is it going to be bad if its one chamber?

You shouldn't mix subs of different resistances.

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What auex said. That 8 ohm is gonna get 1/2 the power the 4 ohms do. Bad design.

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By the end of the 3rd lap I saw Jesus so many times I started using Him as a brake marker.

definite no-no mixing subs of different resistances especially on one amp

I would also say seperate them for all of the reasons already mentioned (bracing, blowing woofers, different impediences).  3 woofers in 1 huge box sounds like a problem waiting to happen, especially using 1 8 ohm sub in the mix.

No disagreement here but a correction on a previous statement. That 8 ohm is gonna get 1/2 the power the 4 ohms do. Bad design. This is most likely incorrect. If rknj01 is going for a 4 ohm load then the 2 4 ohm speakers would be wired in series and then that pair would be wired in paralel for a 4 ohm load. Thus if you assume 100 watts to a 4 ohm load then 50 watts would go to the 8 ohm speaker and 25 watts would go to each of the 4 ohm speakers. Thus, the 8 ohm would actually be getting twice the power of either of the 4s.

Only if you wire the 4 ohms in series. Can't imagine why anyone would wire an amp like that. Wire the 4 and 8 in parallel and the other 4 in series and you get a healthy 6.66 ohm (3.33 bridged) load for your amp. But for a 4 ohm load in mono you are right, you'd have to wire it like you say. No wiring arrangement is ever going to fix the mixed impedence problem, though. The 8 will always be the odd driver out. 

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By the end of the 3rd lap I saw Jesus so many times I started using Him as a brake marker.

Now take all that and add it up..and it equals....DONT DO IT :P

but really...you should really never mix subs..especially on a single amp..it would be better to get 3 8ohm subs and wire them to a 2.6ish ohm load and get a 2 ohm stable amp.

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With a torch and a big enough hammer...it WILL friggin fit!!

First time posting here and Im sure this has been covered at one point or another so I appoligize for the repost, but if you run a single chamber design as compaired to a divided, what do you do about footage?  Say youve got a speaker that needs 1ft.  Do you make the undivided box 2ft or are there allowances you have to follow?

When you wire a 4 and an 8 in parralell,technically(not taking into account the impedence curves,meaning the woofers DO NOT have the same impedence onver the freq spectrum..) the 8 ohm would see very little actual power..it would get something,but not what you would expect.. electricity takes the path of least resistance..
the impedence curves are what allows some power to get to the 8..as far as the seperation,that would be better more for the bracing qualities,rather than the seperation,just remember if you put two woofs in a box,do not port it based on the total volume,port it based on the volume each woofer has..like 2-1 ft3 boxes(but only single chamber) use double the port for a 1,rather than the port for a 2..Make sense? but with 10's,you should run any less than 1.25 ft3 per woof.any less seal it,or do an aperiodic,for real spl,with real lows,do @ least 1.5,pref. 2 ft3. like going with a jl 10" w7,2 cubes,you can port those babies down to less than 30! and still feed them with 500+ watts.I know they say new woofs can go into smaller boxes,but if you tune that low,say in a 1.25,then the woof will not handle even 1/2 as much power.. thats why the overbuilt the crap out of that woof..dont waste it! if you only have 2 ft3 to work with,dont buy a 12,a 10 properly done in 2 ft3,will be LOUDER,and sound BETTER than a 12 in the same situation!
as a guide: 8" 1 ft3(i cant tell you how many hundreds of pairs of 8's i have out there that people guess are 12's all day long,i cant put more than 100 watts(SUPER CLEAN) to them,each,but the wattage guesses range from 400 watts,to 600..)these are based on people that hear underboxed woofs all the time..

anyway..
8's 1 ft3
10's 2 ft3
12's 3.5 ft3
15's 6 ft3 (min) 10-12 optimally)
i know most of you think thats outrageous, but i am sure most of you havent heard these sizes,properly tuned.
I ONLY do sealed/small for a very few people.
my 10's look like 8's because of the size of the box,but sound like the better than average 15,with a fraction of the power..
and dont waste you money on super woofs,unless you get a super amp..untilyou max out a particular woof with power,it is highly unlikely you could hear the diff between a 200 dollar woof,and a 500 dollar woof.most people cant hear a 30 hz wave in the average car anyway! most of the stuff peole think is bass is around 50! 30 just destroys the car! try a subsonic @ the res freq,and tune the box @ that as well,but if the box is smaller,tune it higher,like if you have a 10 in 1.25,for a decent woof,tune it to like 35-40,susonic it @ that freq,and you wouldnt believe what it will do.
that is long enough i think,sorry..i am long winded,but i am passionate about this stuff,ocd passionate,and have 16 years of experience to relay..


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'Stereo' Mike
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