question about airspace

[T.O 240sx]

i recently bought 2 10 Infinity 1030W subwoofers in a sealed enclosure. I have an Audiobahn amp that has more than enough power to push the subs... when i plug both RCA cables (L & R) the sound from the subs is VERY VERY flat, like there is no bass at all. when only one is plugged in, either the left or right... it pounds hard!... only one sub sounds "right" at a time. the box is not dual chamber... so both subs are sharing the same airspace and the box isnt that big.. could the problem be that there is not enough airspace in the box for both subwoofers to pound simultaniously?each sub calls for .75 cu/ft. i included a pic.

[Rex]

Are you running the amp bridged?

My first guess is one of the subs is wired out of phase to the other.

[T.O 240sx]

i knew i could count on you for some quick help! thanks man

to answer the question... nope, its a 2 channel amp, one channel to one sub.

that could be the problem... but if that was the case, then shouldnt both subs work when either the left or right RCA cable is in?

i asked the guy who i bought it from, and he said that they were running from seperate power sources. i dont know if that helps

say the right RCA cable is in, if i took the power out from the right sub, theres no sound at all coming from either sub... and vice versa

[Rex]

If it's wired with one out of phase to the other, then when you disconnect one, the other will act as a passive radiator and allow the other to "hit". When both are "powered" they would fight against each other and thus cancel each other out.

Are the subs 4 or 8 ohm? Single or dual voice coil? Ideally, if they're sharing the same air space you should be running them wired either in series or parallel. That eliminates an imbalance in the amp channels and such.

[T.O 240sx]

ahhh... i see i see... you have enlightened mehow can you tell is its wired with one out of phase to the other?... im assuming i have to open the box up and see.

i fogot to mention, that the amp is bridgeable... but i dont suppose that would help.

the subs are 4 ohms with single voice coil. how do i wire them in series or parallel?... i think thats how i have them wired now, but im not sure on the technical terms.

[Rex]

Assuming there are 2 speaker wire cups on the back of the box. Each speaker's + / - terminals should connect to the cups, then the wires go from the "springy" connections go to the amp. If one set of the wires are out of phase, then as one sub pushes out the other is pulling in, thus cancelling out.

If you chose to run in bridged mode (suggested) you have to make sure your ohm load is not killing your amp. Example, you wire the two 4 ohm subs in parrallel (Positive leads of two or more speakers connected together and all negative leads connected together, but the positive and negative wires aren't connected to each other.) they create a 2 ohm load and when the amp is bridged onto them it (effectively) sees a 1 ohm load and thus may fry.

If you wire them into series (Connect the positive speaker output to one amplifier channel to the positive terminal of speaker #1, then connect the negative terminal of #1 to the positive terminal of speaker #2, and the negative terminal of #2 to the negative output of the same amplifier channel is a series connection.) this will create an 8 ohm load and once the amp is bridged it will see a 4 ohm load. This will seem some what under driven, but will not run the risk if killing the amp.

Hope most of that makes sense .

[Rex]

ahhh... i see i see... you have enlightened mehow can you tell is its wired with one out of phase to the other?... im assuming i have to open the box up and see.

Yes you'll have to open it up and see what speaker terminal is connected to which wire.

i fogot to mention, that the amp is bridgeable... but i dont suppose that would help.

Bridging the amp is usually the best way to run a sub amp, I would, but you may not get the must bump for you amp that way, due to ohm load.

the subs are 4 ohms with single voice coil. how do i wire them in series or parallel?... i think thats how i have them wired now, but im not sure on the technical terms.

See the above post.

[T.O 240sx]

Rex, you are the freggin Buddha of car audio!

most of that made senseand seems pretty clear to me...

my amp is capable of 2 ohm stereo, not mono... so i was told not to bridge it or else it will fry my amp. true or false?

i understand the series and parallel better now... so series will ease the load on your amp and therefore decrease output. and parallel is basically the opposite. would it be fine if i just left it the way it is? i think that would be safe and it will give me the bass i want.

i will definitely open up the box and make sure all the connections are right, and check to check if one sub is phasing out the other.

there are 2 speaker wire cups on the back of the box.

just another question... would i have this problem if the subs were not sharing the same air space? i mean if they were in seperate boxes?

thanks man, i really appreciate the help... i will post some pics of my "ghetto" set-up. well its not that ghetto, but i didnt it myself.

[Rex]

Thanks, but as my Dad would say, I know just enough to be dangerous . Okay, maybe a little more than that.

Bridging an amp on a 1 ohm load if it's not rated for that will shorten it's life, depending on the brand it could make it real short, think boom fizz (lights out), others will just blow the battery/amp fuse. You could bridge it on them (series config), but that would most likely seem like it wasn't hitting as hard.

If you're going to stay with "stereo", then you want to leave the speakers wired to the amp in a normal/straightforward mode. Just make sure the wires aren't criss crossed inside, causing the out of phase condition I think you have.

The 2 speaker cups would lead me to think your box is wired in stereo.

Even if the subs were in their own space (seperate/divided boxes), being wired out of phase (with each other) would still cause it to sound "less" than it should.

It also happens with mids and tweets when they're wiured out of phase to one another.

Hope this all helps and you get things going right. I'll check back tomorrow.

[T.O 240sx]

thanks for all info.i will definitely open up the box tomorrow and see whats going on inside. im thinking that what your saying must be the problem, because i see no other potential problems.just the one sub sounds really nice, so im anxious to hear both pound.once again, thanks for the helpi will definitely get back to you about this in a day of two... please check back.

[PoorManQ45]

Are you running the amp bridged?

My first guess is one of the subs is wired out of phase to the other.

Aww... Keith, I'm disappointed in you . You fell right into a large marketed misconception. What you are talking about is polarity, not phase. Reversing the polarity will cause the driver to play "backwards" relative to the other one, but this does not immediately make them out of phase.

Here, try this. Feed a 50hz constant frequency to two drivers. Reverse the polarity of one of the drivers. Now move either one driver ~11 feet forward, or one driver ~11ft backwards. Note that I used ~11ft because that is approximately one half wavelength. You will notice that the two drivers are at 360 degrees phase, or completely In Phase.

[Rex]

It was a "mis-use" of the term, but my point was the 2 subs in 1 box, one having the pos/neg switched would have the subs fighting each other in the box.

I'd say for "arguments sake", most people that are looking for help here don't have any idea about "phase" or "axis".

[T.O 240sx]

hey Rex.. your arguement is very true!i had no clue what phase is until you explained it to me.... but thats what we're all here for, to help eachother

im about to open up the box and check it out, i will let you know the results

[T.O 240sx]

bingo!!!... found the problem... exactly what you were sayingthe right subwoofer was connected backwards. the wires inside the box from the spring terminal to the subwoofer was wired wrong.ill power it back up and let u know what happensthanks!

[T.O 240sx]

i finished hooking it back up, all i can say is that it sounds the way it was supposed to.thanks for all the help!

[PoorManQ45]

You're welcome.

[audtatious]

For future reference, when determining polarity of subs that are already in an enclosure, I simply use my 7.6v Makita battery. Correct polarity will make the cone move out, thus showing me which wire is positive and negative.

[PoorManQ45]

well, not correct polarity, but it will show you if the polarity is the same.

That's a neat "trick".

[audtatious]

Assuming 1 pair of wires are coming out of the box, one has to be positive and the other negative. Using a battery will validate which one is which. If the cone moves out, the wire on the batteries + is positive. If it moves in, the wire on the + is the negative. This will determine proper amp connections to ensure proper polarity.

Maybe I misunderstood what you meant?

[PoorManQ45]

well, that really doesn't matter either. Try turning the battery around once. You will notice that the driver moves the opposite way now

*edit* It all depends on how you connect it to the amplifier

[Rex]

His point was if you're connecting the positive terminal cup for each sub to the positive side of the battery they should both move in the same direction.

[PoorManQ45]

Agreed. I understood that. I just had to be anal

[audtatious]

Agreed. I understood that. I just had to be anal

Does not matter which wire is on pos or neg of the battery. If the sub moves out, the wire on the pos terminal of the battery is the positive of the sub. If it moves in, it's the negative.

Stop being anal!

[PoorManQ45]

Nope, you can switch which terminal you connect each wire to and the polarity would be reverse

[Rex]

Nope, you can switch which terminal you connect each wire to and the polarity would be reverse

I think his point, is that if you connect poistive to (believed) positive, it should tell you if the speaker wires are correctly connected. You're corect in that switching them will have the opposite effect on the speaker, but that's his point.

[audtatious]

I think his point, is that if you connect poistive to (believed) positive, it should tell you if the speaker wires are correctly connected. You're corect in that switching them will have the opposite effect on the speaker, but that's his point.

Thank you.