Originally Posted by Mark_Likes_Games
Nice guide - I think it applies to me! I'm shopping to upgrade from a Dayton Sub-1200 (which I think was very good for it's cost...).
HOW does one determine if a sub has "good low-frequency extension but modest output"? Is it the +/-3dB frequency spec? How do we tell if it is "moderate output"? I thought the frequency plots were typically normalized to something like 80dB, but I'm not even sure I understand that exactly... So, how do we compare?
The best and most comprehensive sub comparison can be found at Data-Bass. It takes a little effort to understand what you are looking at, but if you click on the specific sub you are interested in, you will go to a more detailed review of that particular sub. http://www.data-bass.com/systems
Some manufacturer's, such as SVS, do post data on their websites that does not reflect maximum output. That data is most helpful for comparing one SVS sub to another. The max output comparisons that Data-Bass does are the best ones I am familiar with for apples-to-apples comparisons across different makes and models of subs.
As for what constitutes modest output, that is such a general term that different individuals will use it in completely different ways. The amount of output you need in a particular room is, in my opinion, most directly linked to your distance from the sub, your listening level, and the amount of bass boost you like to employ. (Most people like to run their subs a little louder than the other channels in a system, as we don't hear bass frequencies as well as other frequencies.)
So if, for instance, your typical movie watching volume is -20, and you are only boosting your sub about 3db above the volume which your AVR set it during calibration, then you don't particularly need a sub which can play 20Hz at 110db, or anywhere near that level. In that case, you would try to define your extension requirements, based on that "moderate listening level" rather than on some relationship to Reference volumes of 0.0 MV.
I think it helps if you already have a sub that you can use as a baseline, saying for instance, "I know that I want to try to get several Hz lower extension, but I don't know that I will need a lot more output than what I have now." It also helps to audition something in your home that won't cost you an arm and a leg to ship back, if you decide you want to upgrade to an even larger sub. Since you are accustomed to having a ported sub, I would probably stay ported, and look for options you can compare on Data-Bass, within whatever price range you establish.
I hope this helps.