Rep Power: 337

I want to expand on whats been said here a little bit, round out some of the discussion with explanation.

Music is recorded in stereo. That is to say: left. right. its a different signal. (or can be). Thus, we can hear in some recordings a bass guitar coming from the right while a voice comes from the left, or a cymbal placed far right with a drum dead center. That plays into part of the "quality" of our "sound quality."

The problem is cancellation. you can do real neat cancellation tests at home. One of my favorites is playing a 1000Hz (or any high frequency) tone through a pair of speakers placed several feet apart, then with you between them several feet away, turn your head back and forth.

What you end up hearing is alternating bands of loud and quiet. We call this "interferrance". Where the tone is loud, its called "constructive interferrance". where the tone is quiet, we call that "destructive interferrance." To make things easier for the car audio croud, we interchange the term "cancellation" with "destructive interferrance". For GREAT diagrams illustrating this phenomenon, google "double slit experiment". itll usually involve light, but the results are the same. alternating bands of light and dark.

Now, your radio (90% of cases) will feed a stereo signal into your two channel bass amp. that means left and right channels absolutely DO play different sources. when ALL the bass is mono, or centered, we arent too concerned. left and right play identically, and all is well.

but when the signal differs (which is 100% of cases, I promise), then the subwoofers will absolutely play at different rates. not only will they be at different volumes, but they will play different frequencies as well!

These two seperate and unique waves interact with each other as they travel from the trunk to your ear. always exibiting cancellation. However, we can AVOID this cancellation by assuring each subwoofer is playing the SAME thing. this eliminates all chance of cancellation within the car, and ultimately increases your output! (compared to a stereo signal!)

How do we assure the subwoofers play the same information? bridge the amp mono. Left and Right signals will be summed, and the subwoofers will be wired together, eliminating any chance of playing different.

Thus, I recommend the first wiring option, for this case and for ALL cases. always.

next thread, I wanna talk about the amplifier power.

 
Rep Power: 337

as for amplifier power, rated power is not a guarantee to take the power.

for example, Resonant engineering makes several subwoofers rated for less than a 1000 watts power handling per. Yet can take several THOUSAND watts of power in competition lanes!

but just as easily a speaker can be overrated. Anyone who thinks their sony 6.5" coaxial actually takes 75 watts rms much less 200 peak is simply bent. anyone who acomplishes that feat simply turns down their amplifier, giving a false impression of true powerhandling. (dont get me wrong, I fully support doing that, but thats another thread!)

Finally, we should consider efficiency. some subwoofers simply NEED their rated power to get loud. others..... dont. perfect example is the differences between XBL enabled subwoofers such as the RE XXX and Adire Brahma versus superefficient supersubwoofers like the IDMax and Audiomobile MASS. You can get very comparable volume levels from the latter with FAR less power than the former need, in comparable installs. every time.

so dont neccesarily think you NEED the bigger amp. Have you already bought it? the money is spent? things are done? install it! see if its as much bass as you want! nice to know you can always get a bigger amp....
However, if I havent bought the amp yet, I'd be leaning toward your current decision, which was to save up for the larger amp. no loss of convenience, and you'd be starting with larger gear. every bit helps.

last, I want to talk about one versus two subwoofers.

 
Rep Power: 337

this is a purely comparative discussion, I need to say this disclaimer right now. I make no claims about how loud you will get, but merely predict, under 100% efficiency and theoretical physics precisely how much louder one wiring configuration will be over another. real world in-situ testing wont yield perfect numbers, but give you very close results. close enough for an ear, anyways!

the thing to keep in mind is that it takes FOUR times as much power to DOUBLE the excursion (stroke) of a subwoofer. Meaning, to displace twice as much air, you need four times the power.

thus, a given subwoofer with 600 rms versus the same subwoofer with 150 rms will only be twice as loud. (measuring loudness via displacement.)

but if you compare one subwoofer at 150 versus two subwoofers at 300 rms, (thats 150 rms watts PER subwoofer), you have again doubled your displacement, and thus doubled your loudness.

compare: 150 rms to a single sub, and two ways to double your volume: increase your power to 600 rms, or add a second subwoofer and feed them 300 rms total.

neat! but how does that affect you?

you can wire up your subwoofers stereo or mono. either way, they see about the same amount of power, each. so you gain NOTHING by wiring in stereo. but you have the potential to lose SO much.

what about running a single sub? an 8 ohm load mono will draw about 140 watts from that amplifier. so 140 to a single subwoofer. If you keep them both, even running the small amplifier, thats 280 rms to a pair. remember the math? twice as loud, right off the bat . You want to be loud? keep them both. even if the amp is small!

I forget to talk about dvc versus svc. that be last.

 
Rep Power: 337

I'll be quick though. All I can say about DVC versus SVC is that it changes your potential wiring configurations. It tells you NOTHING about subwoofer performance --- at all!

it simply tells you what kind of impedance and power ratings you should be looking for in an amplifier.

kind of like saying your TV remote runs on AA batteries. that doesnt make your TV remote better than the one that runs on AAA's! Just tells you what size batteries to buy

 
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thanks whiterabbit you have actually made sence out of a few things for me

+1 to rep