Podcast #608: Subwoofer Basics aka Subwoofer 101

Subwoofer Basics aka Subwoofer 101

Its been a while since we talked about subwoofers and since the subwoofer has the single biggest impact in your home theater experience. We thought it would be good to go over some basics in what to look for and how to setup your subwoofer.

How much subwoofer do I need?

This is a hard question to answer because everyone has a different take. We’ll give you the HT Guys take. Get the biggest one you can afford!! If you think about it, having a larger subwoofer being used at lower levels is actually better for the unit adding to the reliability. Plus the larger subs have an easier time with producing lower frequencies. So if budget and wife acceptance are not issues go big, bigger than you need for your room. Otherwise here are some loose guidelines:

• Small room - 1200 - 1500 cubic feet (34 - 42.4 cubic meters) 10 inch sub

• Medium room 1500 - 5000 cubic feet (42.4 - 141.6 cubic meters) 12 - 14 inch sub

• Large room greater than 5000 cubic feet (141.6 cubic meters) 16 inch sub (possibly two)

Where is the best place to put subwoofer in the room?

Wherever the wife allows! In all seriousness this can be a form over function process. Typically we say in the front of the room in a corner. By placing it in a corner you can accentuate the deep bass that shakes you to the core! But if you like punchy bass, put the subwoofer close to you. Keep in mind that the room may cause unwanted reflections that can muddy the bass so finding the optimal placing may require you to do the subwoofer crawl. For this you need to place the subwoofer at the listening position and then crawl on the floor while listening to a familiar bass track. The spot where it sounds the best is where you should place the subwoofer. Now this may not be practical so your only other option is to use sound dampening techniques to stop the unwanted reflections. We talked about a few in Podcast #432 Home Theater Acoustic Treatments.

How do I connect my subwoofer?

There is a lot of talk on this subject. Some people claim that you need a special subwoofer cable that can cost in the hundreds of dollars. For this we turn to the experts at HSU Research. They state that all you need to connect their subwoofers to your receiver is a mono RCA cable. Less than $5! If your subwoofer has an LFE input plug the RCA cable into it. If it has L/R inputs use a y-adapter to plug the same signal into both the left and right inputs.

What crossover frequency should I use?

Before we talk about crossover we want to discuss setting your speaker size in your receiver and for this we turn to Ray Coronado of SoCalHT.com. He says make sure your speakers are set up as small. Ray says large speakers can reproduce sounds from 20Hz up to 20KHz and the vast majority of speakers can not do this. Now that you have your receiver configured properly for your speakers lets turn to crossover.

If you have small (in size) speakers they typically can’t do much on the lower end so set your crossover at 100hz. You may want to go as high as 120Hz. Play some test material with a lot of bass and change the crossover. Settle on the one that sounds the best. If you have floor standing speakers you should set your crossover at 70Hz and work your way up. The typical setting is 80Hz.

What is this Phase Knob all about?

From the SVS Manual:

Think of long bass waves as conflicting or enhancing each other, depending on the timing of their arrival at your listening location (either together, or not). Set phase to zero if your AVR offers settings for the distance from your seat to your subwoofer. Adjust in small steps for smooth sound with music playing if your AVR lacks a subwoofer distance setting.

In other words your AVR’s EQ/Calibration process will adjust for phase issues.

Speaking of EQ? Is it a good idea to use the Auto Calibration with my subwoofer?

Yes, but make sure your subwoofer is is setup to output the flattest response it can from the factory. Like in the above section set the phase to zero and close the appropriate ports on VTF subwoofers.

What is a Variable Tuning Frequency Subwoofer?

Unlike a Single Tuning Frequency subwoofer where the bass characteristics are fixed. The Variable Tuning Frequency Subwoofer can vary is bass characteristics by using ports that can be opened and closed. You can set up the subwoofer for lower bass extension or more headroom. The main benefit is that you can get the exact subwoofer sound that you want!

Course Summary

Like we said at the top, these are just the basics. There is so much science that we didn’t even get into. Perhaps another day. In reality the science doesn’t matter for most of us as long as we can get the best sound out of our home theaters. We hope that this basic introduction will help you along the way!