How do you know if you need to add a sub (without auditioning one, I mean)?

Thanks for the responses so far. Is there a consensus as to how much one needs to spend to get a decent sub that really makes a difference? I’m not saying I want to spend the bare minimum, I’m just interested in a basic parameter.

There are plenty of great subs. In smaller systems I've really enjoyed the SubX from Goldenear.

But one thing you'll run into right away in most rooms is standing waves which will make the use of one sub hard to do and likely causing the sub to be inconveniently placed. These are bass notes whose wavelength is significant- under about 80 Hz they are over 14 feet long. Such a wave can bounce off of the wall behind you; at certain frequencies when it comes back to the listening chair will cause a loss of bass energy as it can be out of phase with the incoming waveform.


I know Erik gave advice about using room treatment and room correction for this problem. In a nutshell, it will make little difference if bass is being cancelled by standing waves!. When bass is being cancelled, room correction will ask the amp to make more power at that frequency, and of course that power will be cancelled- you'll have the same problem and the amp will run out of gas. Room treatment won't fix it either, unless you're able to have the bass traps actively move about the room as the bass notes change :)


But there is an elegant solution, and one of the best ones isn't all that pricey. I'm referring to the use of a Distributed Bass Array (and the best example of this is the Swarm from Audiokinesis.com). A DBA uses four subs placed asymmetrically in the room. Because the wavelengths are so long, bass below 80Hz is omnidirectional- you can't tell where its coming from. Its the harmonics of the bass notes from your main speakers that allow you to place the source in front of you. So in a DBA, with the bass coming from a variety of directions, the standing waves are broken up, causing the bass to be evenly distributed around the room.


The Audiokinesis Swarms are designed to be placed directly against the wall so as to take advantage of the room boundary effect, which is +3dB per octave going down from 100Hz or so. In this way the Swarm subs can be fairly compact as they are designed to roll off at 3dB/octave over the same range. The result is flat response to 20Hz. They need a subwoofer amp but Duke at Audiokinesis can guide you on that- its not expensive.

As long as the subs are not making any output above 80Hz they will not attract attention to themselves. So they should be crossed over lower, maybe at 50Hz or so. In most rooms this is insanely easy to set up.


After this is done then Erik's suggestion of room treatment and the like is useful but not before!

Sound meter (you can use an app on a smartphone) and white noise as a source ( available to stream via internet).

If you do not see response down to 20 hz, you are missing the lower octaves that you should be able to hear and a proper sub would be the remedy.

Use the same app and white noise to adjust the sub to proper level and crossover frequency if you get to that point.

Wow, what ton of helpful responses.

Need? Why?  
I do not comprehend.  
I have subs because I enjoy hearing freqs (if present) that are below the capability of my mains.
Maybe you NEED a haircut. There are actual reasons for that.

Depends on what kind of music you listen to and how loud you play it. If you are listening to bass driven music like blues and rock a sub is almost essential, other genres, not so much. The biggest issue with subs is integrating them. Integration is a 2-way process in that you need to integrate them to the room as well as your system. There are tools out there that make the process much easier but most 2 ch. systems are not designed to allow their incorporation.

Multiple subs definitely makes the integration task much easier. I have never heard an actual Audiokinesis "Swarm" bass system, but what I have read about it I believe it is probably the best bang for the buck sub system available and probably one of the easier systems to integrate since I believe the Dayton amp that comes with the system has both low and high pass filter capabilities, which in my opinion is essential for proper integration. Other good value subs I'm familiar with are SVS and Rythmik and HSU is probably worth looking at also. For a little more money the "e" series subs from JL Audio would be worth a look since they also have low and high filter capabilities.