|Let’s talk subwoofers…
Subwoofers (and all speakers) make sound by moving air. Subwoofers just have to move more air than other speakers due to only playing lower frequencies.
A low frequency sound is created by moving a lot of air slowly, while a high frequency sound is created by moving way less air very fast.
So how do you move a lot of air?
2 main ways:
1. More excursion
2. More cone area
I always recommend going with the biggest sub(s) you can fit (more cone area).
In simple terms, you can get the same output for less effort and less money. And it’s safer. (This is just a generalization. There’s always an exception.)
Let’s break this down using a couple examples:
Ex 1: Let’s compare 2 almost identical subs, just different sizes.
Say you have an 8″ W3 and your buddy has a 12″ W3. Same amp. Let’s assume they’re both pushing 200 watts. And same everything else. Both boxes are built to optimize each sub.
Obviously the 12 will move more air. Which means it’ll play lower and get louder. This is due to having more cone area.
This example assumes both subs have the same xmax (they don’t, the 12″ has more but only when you feed it more power) but even assuming they have the same xmax, the 12 will be louder and play lower due to being able to move more air.
And in a real world situation, the 8 may have more excursion than the 12 when both are getting 200 watts. That’s due to the extra mass of the 12″ cone and internal components.
Even still, the cone area will let the 12 move more air.
Generally, when comparing 2 subs from the same line, the extra mass of the larger sub is pretty negligible. This is not always the case when comparing different brands or product lines though.
Ex. 2: Say for some reason you want an 8″ sub that’ll get as loud and play as low as a 12″ W3.
You can’t do it with an 8W3. Not even with 2 8W3s, even though you’d have similar cone area to one 12W3. (But if you’re getting 2 subs anyway, why not 2 lowered power 12s?)
If you’re running 2 8W3s and the same 200 watts, each 8 will have less excursion than a single 12 due to only receiving 100 watts each. So even though you’ll have similar cone area with 2 8s and a single 12, the 12 is still the way to go if you’re using the same power.
You also get into extra price due to adding another sub and getting a bigger box.
So how could you get the same output of a single 12 with 8s?
You could run a SUPER beefy 8 and super custom box. This seems to be the trend recently.
It’s cool to get a ton of output out of a small sub I guess, but you run into additional costs, additional power, and additional risk of ruining your sub.
Additional costs because an 8 that can provide the same output as a 12 will cost more than that 12. You could try 2 or 3 or 4 8s, but that’s going to cost even more.
Additional power, because remember there’s 2 main ways to move air: cone area and excursion (xmax). Cone area isn’t dependent on power, but excursion is.
So to get that super beefy 8 to move as much air as a lower powered 12, you’ll need a decent bit more power. Which means bigger, more expensive amp and in some cases bigger power wire.
More power eventually leads to upgraded components like bigger alternator and/or additional batteries.
Additionally, the main reason subs blow is heat. Heat due to over excursion from too much power. So if you are trying to run a high powered 8 in replacement of a lower powered 12, you risk damaging that sub by running more power to it.
Like I said, these are generalizations, and there are plenty of 8s that can take some power. But why not just buy a similar 12 and run it at a lower power?
Sure if you get the 12s, you’ll want to max them out too. But there has to be a stopping point or you would have just bought four high powered 24″ subs and called it a day.
TLDR: Get a lower powered 12 over a high powered (or multiple) 8s.
This obviously doesn’t just apply to 8s and 12s. Those are just some common sizes I chose randomly. If you can fit the box (or design an infinite baffle) required for an 18, go that route.
At the end of the day, all that matters is your goals. But generally your goals can be easily accomplished with a slightly bigger sub than what you were thinking while running less power.
I could probably make up some more scenarios, but I’ll stop here. I could also do the math and provide more details of exact power numbers, excursion needed, and take into account cone mass, etc. But I’m going to leave this as a more simple generalization so you understand a bigger sub is usually better.
There’s a reason some SQ builds use 18″ or even 24″ subs.
Also, back in the 90s (before my time in car audio admittedly), people would run 2 or even 4 12s on tiny little amps. Even with the small amount of power, the bigger, multiple subs would move a ton of air.
Let me know your thoughts or experience with running different sized subs on different power levels. I’d love to hear some more real world experiences than my own.
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