I have always subscribed to the notion that 15″ is the perfect sub size for smaller PA’s. 18″ have a habit of becoming a bit “blubbery” at higher volumes. 12″ are a bit small to pack that real punch. 30-75Hz sounds require a lot of air displacement/movement. I think the surface of a 12″ just isn’t quite up to the task (especially the lower bits).
The Mackie HD1801 I got is a favorable exception to “my” 15″ rule. I did an A/B comparison in a showroom setting between the HD1501 (15″ obviously) and it’s bigger brother. I listened to the 15″ first and noticed it straining at the end of it’s power. Not wobbly, but definitely not totally tight and some distortion starting to appear. Mind you, this is at a sound level most other subs would have tossed in the towel completely already, these suckers are LOUD!
Then the sales guy said would I like to hear the 18″. Told him I didn’t like 18″. He said to just listen, I was there anyway. So I did and was blown away. Awesome punch, tight as a drum (pun intended) and no wobble all the way to the stops. And, good news, I realised there and then that my “buy one 15″ now and the next one when I can afford it” could be replaced with “Get the 18″ now and never worry about a second one”.
And that turned out to be true. I never ever feel the need for more (sub)low end in conjunction with me two HD1221 12″ tops (and occasionally I’ll bring my two SRM450v2s as well).
The point I’d like to make is that a) not all “rules” apply all of the time and b) it pays to go to a place where you can hear several of the speakers you are looking at the levels the are intended to play at (like 80% or higher) and preferably with the music you intend to play through it.
You might just be surprised!
Greetinx.
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