If you've missed out and want to learn about subwoofers, how to build one and how to dial one in using DSP, catch up on previous columns at coloradodaily.com/columnist/duncan-taylor.
If you've ever pressed a bass boost button, this column is for you. If you've ever fiddled with the tone controls in the car or bravely attempted the sliders on a 15-band equalizer, this one's for you, too.
Audio EQ or equalization exists for a couple of reasons. Music playback systems are mostly imperfect, and most listening environments are far from ideal.
In a car like mine, for example, the subwoofer is set too loud by default, so I use the tone controls to cut the bass slightly.
In a concert venue like the Fox Theatre, tweaking the system to sound better based on the dimensions of the room and the environment is a serious task, one which may involve up to 100 bands (points along the spectrum of what we can hear) of control. The intense professional EQ analysis and adjustment for a room like that can take a day or more to complete.
In our ongoing and nearly completed DIY subwoofer project, we're looking at equalization that is more like what you see in a modern car than at a performance venue like the Fox. We're just focused on the bass, so it should go a lot quicker for us.
Last week, I left you with a glimpse at the PEQ section of the Dayton Audio software and the task of trying to mirror what you saw on the RTA app readout — what the bass was doing in your room given your subwoofer's location — in reverse. Seeing a boost at a certain note in the bass on the RTA means you'd make a cut at the same place in the PEQ.
Every time you apply equalization or a tone control using an analog device (think receivers, outboard equalizers, most car stereos and most bass boost buttons) there is a slight shift that happens to the timing of the different parts of the music. This is called a change in "phase," and it's inherent in any analog filter that filters out highs or the lows in order to accentuate the other.
Newer DSP equalizers, software plugin equalizers and other digital implementations can manage to change the sound without changing the timing. That said, there are other places for the digital EQs to mess things up, like in the noise department when you're adding gain (boosting), for one.
There's never exactly a free lunch when it comes to good sound — you're usually compromising one thing to get something else. That rule applied to this means that with EQ, across the board, less is more. A light touch pulls off what you want to achieve without causing too many new headaches.
To go along with that, and as a nod to the gain issue with digital EQs, it is always best to try to do everything you can by cutting before you resort to boosting. We don't want to obscure the rest of the sound just to get a little more bass. Tune in next week to learn more.