Things are gonna be changing around here.

Except not really. I'm just going to start posting here again after a decade long hiatus. I originally created this blog way back in 2011 for my "Lighting Concepts and Design" class at Full Sail and I've decided to breathe new life into it. That said, I'm going to keep all the original posts and designs from 2011. Because It's still the same blog, right? I think I'm mainly going to be using it to post some art as I try to hone my skills a bit. I'm sure I'll be dumping some other stuff. Lots of nostalgia and memories probably. We'll see what happens. I know I have a huge audience on here of about 1 person, myself included, so I'm pretty comfortable sharing my crappy old art and boring memories. But to the lost souls that happen to wander into this desolate, barren hellscape of a web page, I'm sorry for what you may see.

Friday, September 2, 2011

Aux Fed Subs. Science fiction? I think not!

So in my quest to find an article worthy of writing a blog post on I decided it was a good idea to choose an article that would be not only useful to me, but also something that directly interests me. After skimming a few articles, I actually found the article on aux fed subwoofer systems to be extremely interesting. Partly because it’s something I’ve never thought of before, but also because it’s a pretty simple solution to a common issue.

To those familiar with audio and/or live sound the name does a pretty good job of summing up what happens in the setup. To clarify for those who don’t have a firm grasp on the subject, here’s a little summary…

In a standard live sound speaker setup, all of the microphones that have been set up are run into the Front of House console, mixed, twisted, modified and extruded out of the main stereo bus. At one point in its path to the actual noisemakers, the stereo signal makes its way to a crossover where it is split up into generally three or more bands of frequencies including at least including highs, mids, and lows. There’s a bit more to it than that, but for the purpose of this post that’s all that is really important right now.

What changes in the aux fed subwoofer system is pretty simple really. Instead of feeding the subwoofer from a split signal coming from the stereo bus, an aux master is calibrated to match the crossover that is sending signal to the higher frequency speakers, and that aux channel is fed directly to the sub woofer. So in the end the result is your highs, high mids, low mids, etc are still fed from the stereo bus, and your subwoofer is fed from an entirely different aux path.

The picture at the top taken from the article sums it up fairy simply.

Now, why is this significant? Because when too many low frequencies get together and have a party, things sound messy. With the standard splitter approach, every single microphone and instrument sends its low frequency content to the console, and in turn, to the sub woofer. Everything. Even things that don’t really have any valuable low frequency content. The article used examples such as plosives from speech, as well as undesirable proximity effect from various microphones.

Generally, the common solution to ridding a mix of the low frequency muddiness is to apply a high pass filter to drop off anything below a certain frequency. However, with this approach, low frequencies still get through to the subwoofer due to the nature of how a high pass filter works. Even though this removes a fair amount of the low frequency information from the channels, the summing of all the microphones and instruments across the numerous channels can still lead to a very nasty sound coming from the sub. With the aux fed sub system the mix engineer has the ability to completely remove a track from the subwoofer output. This makes it possible to use the sub to enhance only the channels that focus on low frequency information. And the setup is also very forgiving. If a mix engineer decides during a performance that a channel should be added or removed from the subwoofer, it can be done very simply and easily with most live consoles.

For me, this seems like a great idea. Nothing ruins sound for me quicker than a muddy low end sound. I can deal with other tuning issues from a tinny sound to harsh highs or quiet mids, but crowded bass tracks make me want to stop listening. This approach is extremely simple and can be easily done on most modern gear without the need to buy additional components. The most difficult part of the process is the initial setup, but it’s still not too difficult to learn. Some people insisted that the system has some negative effects, such as affecting frequency response of some of the sources. When you look at the big picture however, you have to look at all of the pros and cons. Most every method of live production has some drawbacks. And as with those other methods, you have to learn when this approach is appropriate. In my opinion, I’d much rather have a clean low end with slightly affected signal response in the highs and mids, rather than an overpowering, boomy, unpleasant low signal.

To wrap this post up, the aux fed sub system is a great, cheap, easy, and especially effective way to do some low level hertz cleanup on your mix, especially if you have an excess of inputs to worry about. Because it’s easy to collect a heaping monstrosity of bass in many live sound applications, I believe that this technique could come in very handy.

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