Anyone know what the advantages, if any, of a single sub having it's own airspace chamber? Would it be bad to have 3 subs running in parallel sharing the same chamber?

 

If they are running off of the same amp you will have no problems. The main advantage to having one chamber is it is easier to build the enclosure. But if you put a divider in the box it makes the box stiffer which the yields better results....the stiffer the enclosure the better the bass response, sq, and overall volume.

 

Actually, using a sealed box, each time you divide the box, you reduce the volume of the space for each sub. In doing so, the bass becomes tighter (less booming), but the freq response is reduced, and the ability of the sub to reproduce low bass is reduced or eliminated. Each sub is designed to function optimally within a given space or volume. This information is usually included with the subs.

Subs sharing the same space should be limited to even numbers. That way, if your volume is limited, you can connect the subs out of phase (one sub - to -, + to +, and the other - to +, - to +) so they are not firing against each other. I've wired 3 into a box before, but one of the subs was a DVC, so, in essence, wiring-wise, there were 4 subs.

Remember also that subs still have that pesky optimum volume thing...if the subs share the same volume, then if 1 sub requires 1 cu ft, then two firing in the same space require 2 cu ft. You can fudge this and sacrifice some response, or fill the box with polyfil to soften the bass, but the best solution is to match your volume with a sub designed for it, and an amp to match the power capability of the sub. I believe in quality sound, not shaking the cars next to me. I think you will be extremely happy with one of the boxes from sub-thump or the like. More subs will move more air, but they require more space to do it.

 

Wow. That was confusing.

Yes, you can use multiple speakers in one box as long as the box has the proportionately larger volume for all 2, 3 or 4 components. There will be no performance benefit or loss. If they are not all matched components, it will never be right. It doesn't matter if you have even numbers or not as long as they are all powered equally. NEVER wire subs out of phase with another sub in the same system, much less in the same box.

 

I stand corrected. ROBVUK is correct. You should not wire subs out of phase.

I disagree about there being no performance benefit or loss. All things being equal (sub size, box volumes and power) more subs means more air is being pushed, and therefore more base response. 3 10" subs at 200W each hit harder than one at 200W given all three have the same individual volume as the one and are powered equally.

Even numbers come into play with regard to the amp being used and it's stability when connecting multiple subs. Without getting too technical, ohm loads from odd numbered subs will potentially cause clipping unless the subs are designed to be run in odd numbered groups. Rockford Fosgate made several box systems using 3 subs, but these pre-installed subs were built with special ohm loads so that when the box was installed it was seen by the amp as a 4 ohm load.

Yeah...I know...more "wow...that was confusing"

 

As long as you make the box 3 times bigger than one, sharing 3 subs in a box offers no penalty as opposed to 3 separate smaller boxes. If you have 3, 8ohm speakers wired in parallel, the total load will be 2.666 ohms. Most amplifiers these days are stable as low as 2 ohms, so 2.666 is just fine. If you use 3 4ohm speakers, that would make 1.333 ohms which is not recommended, although you COULD wire 3 of them in SERIES and get 12ohms total but of course that would be at slightly reduced power. If your amp mfr. recommends 4ohm minimum, then you have a problem and you'll have to reconfigure. The amp really doesn't know or care if it has 3 or 13 speakers on it. As long as the total impedance doesn't drop below the recommended minimum.

If the total box impedance on the 3 sub Fosgate was 4ohms, then each individual speaker was wound with 12ohm voice coils. It's really quite simple. No rocket science here. 8ohms/2spkrs=4, 8ohms/3spkrs=2.666, 8ohms/4spkrs=2ohms.

I don't mean to confuse anyone here but in fact, most speakers have a widely varying impedance, depending on what frequency you are measuring at. The NOMINAL impedance is just an average. A typical 8 ohm speaker will probably be well over 20ohms at resonance and dip as low as 5 or 6 at other frequencies.

 

Yea, couple days too late on the info, but it's good stuff. I did some googling and came to the conclusion that basically it's not a problem as long as the airspace is there... which it is. Thought maybe you'd care to see the creation. It's pretty pimp, going in a mini tubed C5 Coupe

 

WOW!!! This is the box I am trying to build. Does the top still fit? Are these 10s or 12s?
Want some pics if the top still fits!!

Nice Work.

 

Don't know if the top still fits, wasn't a concern of his when I made the box. And this is for 3 10" subs.

 

Is the back half (opposite of the drivers) supposed to sit down on the floor and in the center compartment, or what? Got any pix of it installed in the vehicle?

Looks good, BTW.

Mark

 

Yes, it's supposed to fit against the back of the car/cargo compartment while still having the 2 side storage cubbies available. Will be a little while before installed pics are up. I just shipped it.

 

would like to see that installed, i am still debating how to install either my 1 10 or my 1 10 with the 10 inch PR, not sure if i want to do the partition thing yet i dont want to loose too much space, the sub only requires .6 airspace but has a mounting depth of 7.5, any ideas?