# 2 amps on 2 subs.....



## enerlevel

if i was to power two 12" subs with 2 amps then what should i be doing???

i heard a common enclosure would do cancellation ....... so will two different boxes solve the problem? but they would be in the same trunk so would tht give problems as well?


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## azngotskills

same or identical enclosures....match subwoofer output


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## enerlevel

yes identical subs , identical amp , identical enclosure.


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## azngotskills

no i was telling you what you should do


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## TREETOP

Maxxlink FTW.


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## Austin

just build a two chamber box...that should do the trick. are you running the two subs stereo? like left and right or just a sub channel?


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## TJ Mobile Audio

Austin said:


> just build a two chamber box...that should do the trick. are you running the two subs stereo? like left and right or just a sub channel?


Yeah, a two chamber box looks 10x cleaner than two separate boxes and solves the cancellation issue. Which, by the way, is pretty much only an issue if you're running two amps. I wouldn't run "stereo bass", it's a waste of efficiency IMO since bass is nearly impossible for the human ear to localize, and running the subs in sync can create acoustic coupling, basically the two subs act bigger than they are, for a boost in efficiency. Oversimplification I know, but trust me on this one. 

You will have to level-match the amps with a multi-meter, and also set the crossovers to the exact same point. Personally, I would sell the two amps and get one bigger amp, that would save you all the extra work. If you're intent on running two amps for cosmetic purposes, get two mono amps that are bridgeable (they should have a switch that says like "Master/Slave" on the side) then you won't have to level match - the master amp gets control, hence the term "master". This way, the two amps bridge to one channel, and you could run the two subs in one chamber. Even in separate chambers, it's more likely that you'll get a boost from coupling if both subs get the exact same signal, as opposed to slightly different signals from different amps.


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## cubdenno

you can run the subs in a common chambered enclosure. You just have to make absolutely sure the gains are set the same. This is where a Maxx-link will shine or run the amps strapped if you are able. It can work, its just easier if you are building an enclosure to make two separate chambers. The drawback to that is if you are porting the increase in box size due to having to have two separate ports taking up valuable real estate.


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## TJ Mobile Audio

cubdenno said:


> you can run the subs in a common chambered enclosure. You just have to make absolutely sure the gains are set the same. This is where a Maxx-link will shine or run the amps strapped if you are able. It can work, its just easier if you are building an enclosure to make two separate chambers. The drawback to that is if you are porting the increase in box size due to having to have two separate ports taking up valuable real estate.


Two separate ports, each with half the volume = same amount of "real estate". I do see your point though, when you account for the thickness of the wood, but that seems like a minimal sacrifice. Some of the single-chambered multi-woofer ported boxes I've seen will build up a bit of a resonance inside at certain frequencies, causing one sub to move differently and appear "out of sync" with the other at times, and that's even when running on one amplifier. Not a huge issue, but it does happen occasionally, and it probably means some SPL lost to cancellation. Multi-chamber boxes are not as prone to this condition, but when time, money, or space is a constraint, they can be an acceptable compromise. Many times there is no noticeable difference, but it's better to play it safe IMO.

My general rule is no more than 2 woofers per chamber when porting, and if you're looking at any serious excursion I'd go with one per chamber. This is mostly superstition, but I have occasionally seen it make a difference. If you go with a single chamber/single port setup, do your best to ensure that both woofers have equivalent paths to the port and equivalent operating conditions in all other regards. And like cubdenno said, be sure both speakers get the exact same signal, either by level matching or strapping.


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## enerlevel

i have two soundstream 760.2 amp.

i will be bridging the amp mono to each woofer. i have some old stuffs left with me and just wanted to make use of it. 

mostly i have seen setups with two amps running two subs , they trend to sound good only at certain levels , when u start pushing the woofers , there is bass cancellation . which ends up burning the coil of the sub (seen it happen in 3-4 setups.) altho the box were chambered and both ported.

also , with a chambered box , when i push the cone on one sub , the other moves as well.... why is tht? altho the box is chambered


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## 76Trans Am

enerlevel said:


> i have two soundstream 760.2 amp.
> 
> i will be bridging the amp mono to each woofer. i have some old stuffs left with me and just wanted to make use of it.
> 
> mostly i have seen setups with two amps running two subs , they trend to sound good only at certain levels , when u start pushing the woofers , there is bass cancellation . which ends up burning the coil of the sub (seen it happen in 3-4 setups.) altho the box were chambered and both ported.
> 
> also , with a chambered box , when i push the cone on one sub , the other moves as well.... why is tht? altho the box is chambered


The internal chambers are not air tight...


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## Brian10962001

It will make NO difference so long as one of your subs or amps doesn't let go. I ran a pair of Pro box 12's which have the old W6 motor in a vented shared chamber enclosure off of a pair of Rockford Punch 500.2s, this is above their rated power and they held up fine through lots of use.


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## cubdenno

TJ,

The whole port thing taking up more space when running dual or single chamber is valid. Even when you consider material. When you halve the volume by dividing the box into seperate chambers, you have to increase the length substantially to achieve the same tuning frequency. 

I usually settle on a particular area for the port depending on what the woofer is. I try to follow the 12-16 square inches per cubic foot. then I punch in my numbers into WinISD pro alpha and design from there. Ex:
a single 12 in 1.5 cubic feet vs 2 12's in 3 cubic feet shared. Both tuned to 40 hertz. Using a slot port for each type. 2"X12" for the single and a 4"X12" for the double. The single woof needs just over 22 3/4" in length to reach that tuned frequency, the double needs 21.14 for 40 hertz.

Now if you double the volume that you will have to have because you need 2 of the ports for the double chambered box, with material added in, the common chamber single port enclosure takes up 300 cubic inches less space, is easier design the port with very little wrapping of the port and the initial overall volume doesn't take in to account the divider as well as extra material to run the two ported two chambered enclosure.

By going this way I have been able to reduce the overall size of the enclosure for SPL purposes to something that for the intended purpose could be lived with. Though either way, they are always freakin' big!


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