A Weird LFE Routing Solution

Getting creative to obtain more bottom end.

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This is another one of those case studies where you get to see how strange my mind is. As such, be aware that it may not be applicable to you at all. I had a bit of a conundrum, and I solved it in a creative way. Some folks might call it “too creative.”

Maybe those people are boring.

Or they’re reasonable and I’m a little nuts.


I’ve previously mentioned that I handle the audio at my church. We’ve recently added some light percussion to complement our bass-guitar situation, and there was a point where our previous worship leader/ music director wanted more thump. That is, low frequency material that was audible AND a bit “tactile.” In any case, the amount of bass we had happening wasn’t really satisfying.

Part of our problem was how I use system limiting. I’ve long nursed a habit of using a very aggressive limiter across the main mix bus as a “stop the volume here” utility. I decide how loud I want to get (which is really not very loud on Sundays), set the dynamics across the output such that we can’t get any louder, and then smack that processor with a good deal of signal. I’ve gotten to a point where I can get it right most of the time, and “put the band in a box” in terms of volume. Drive the vocals hard and they stay on top, while not jumping out and tearing anyone’s face off when the singers push harder.

At the relatively quiet volume levels that we run things, though, this presents a problem for LF content. To get that extended low-frequency effect that can be oh-so-satisfying, you need to be able to run the bass frequencies rather hotter than everything else. The limiter, though, puts a stop to that. If you’re already hitting the threshold with midrange and high-frequency information, you don’t have anywhere to go.

So, what can you do?

For a while, we took the route of patching into the house system’s subwoofer drive “line.” I would run (effectively) unlimited aux-fed subs to that line, while keeping the mains in check as normal, and we got what we wanted.

But it was a bit of a pain, as patching to the house system required unpatching some of their frontend, pulling an amp partially out of a cabinet, doing our thing, and then reversing the process at the end. I’m not opposed to work, but I like “easy” when I can get it. I eventually came to the conclusion that I didn’t really need the house subs.

This was because:

1) We were far, far below the maximum output capacity of our main speakers.

2) Our main speakers were entirely capable of producing content between 50 – 100 Hz at the level I needed for people to feel the low end a little bit. (Not a lot, just a touch.)

If we wouldn’t have had significant headroom, we would have been sunk. Low Frequency Effects (LFE) require significant power, as I said before. If my artificial headroom reduction was close to the actual maximum output of the system, finding a way around it for bass frequencies wouldn’t have done much. Also, I had to be realistic about what we could get. A full-range, pro-audio box with a 15″ or 12″ LF driver can do the “thump” range at low to moderate volumes without too much trouble. Asking for a bunch of building-rattling boom, which is what you get below about 50 Hz, is not really in line with what such an enclosure can deliver.

With those concerns handled, I simply had to solve a routing problem. For all intents and purposes, I had to create a multiband limiter that was bypassed in the low-frequency band. If you look at the diagram above, that’s what I did.

I now have one bus which is filtered to pass content at 100 Hz and above. It gets the same, super-aggressive limiter as it’s always had.

I also have a separate bus for LFE. That bus is filtered to restrict its information to the range between 50 Hz and 100 Hz, with no limiter included in the path.

Those two buses are then combined into the console’s main output bus.

With this configuration, I can “get on the gas” with low end, while retaining my smashing and smooshing of midrange content. I can have a little bit of fun with percussion and bass, while retaining a small, self-contained system that’s easy to patch. I would certainly not recommend this as a general-purpose solution, but hey – it fits my needs for now.