A 2 speaker passive system or 2 speakers with one sub?

Hey Mike,

First off, you make it sound like 2×15″ would be the same as 2×12″ with a 15″ sub.

They are different things. If you have 2x 15″, the 15″ don’t do just the low frequencies, but everything up to where the tweeters take over (high midrange or so). So if you put say 300W into a 15″ speaker, it has to spread that energy rather thinly from 75Hz up (maybe a little lower depending on brand/speaker). Bass takes by far the most energy to reproduce. So there is no way you are gonna get sub-level bass out of a fullrange 15″ speaker.

Subs are powered much higher (not uncommon to have more than twice the power, which by the way is the equivalent of only 6dB more sound level) and, more importantly, only have to power the say 35/45 to 125 Hz range. So twice the power and only a very small portion of the audiospectrum to worry about.

Another thing is the way speakers work, when the 15″ has to bring too much frequencies, all kinds of interferences take place, mostly affecting the bass performance. No such trouble in a sub, it can do the long throw, high volume, low frequency movement without any hinder of the higher frequencies also needing to be played.

The questions you should ask yourself are therefor:

1. Do I really need a sub. Buy a sub only if you are lacking in the really low freqs.
2. How much overall sound level do I want. This determines if you need 12 or 15″ full range speakers and is something you can judge independently of the sub question.

The subs will add depth and more umph to your sound, making it more full and people will feel more than hear the effect.
Subs are unwieldy and heavy things. And if you don’t do many mobile gigs, get a small sub to go with your 12″ and keep everything portable.
Greetinx,
C.

It’s highly personal and, as always, you get what you pay for. I would definitely keep it to 1 sub, 12″ is probably not gonna give you enough umphh really. But there are some rather compact 15″ subs about you might wanna try. Best option is your favorite music/sound gear store and just listen to your own favorite music on a few subs. Make sure they only swap out the subs, not let you listen to entire sub/fullrange systems or to TWO subs.

I have the Mackie HD series (digital amps) 2x 12″ and 1×18″ sub (purely because it was so much better sounding at high volume) and a total of 2000+ RMS … I have no problem doing 200-250 people with it … although around the number I’ll add two Mackie SRM450v2s for side/back fill. This is by no means an affordable setup, so … and the 18″ is small for an 18″ but too heavy and big to lift/fit into the back of a hatchback.

Greetinx,
C.