If you're new to house curves, start with Wayne's excellent dissertation here. I’ll refer to those ideas in this thread. I would like to share some of my recent experiences and ideas about house curves. Each of you will have your own preferences, but you might think of something new you'd like to try.Wayne A. Pflughaupt said:Dialing in a house curve is not a "one size fits all" endeavor.
My last sub was a sealed box with one 10” woofer. The house curve that I settled on was probably influenced by the low end limitations of that sub, and not really by my true listening preferences. My recently completed IB subwoofer can dish whatever I ask for, and that’s why I’m tooling around with house curves again. I want to find a curve that sounds great with music and movies, giving both a natural sound and a powerful foundation, and earth shaking impact or rumble when called upon to do so. I call my goal lean and mean. Bass should not sound bloated or overblown, but should have plenty of low end power.
First, I'll look at house curve .txt files. The simplest house curve files use two coordinates to establish a frequency interval and a gain. For example, here’s an 8 dB rise from 80 Hz down to 31.5 Hz.
This line is not straight on the logarithmic scale. A flatter house “curve” can be written by specifying equal steps every 1/6 octave like this:
Here are the previous two house curves superimposed.
You can see that the target level of the curved line is a couple of dB higher in the middle of the slope. That 2 dB hump doesn’t look like much, right? But a low, very broad hill in your frequency response is more audible than a narrower, higher peak. You might listen to the flat and the rounded house curves above, and you may prefer the rounded, or the flat, or not care at all. (OK, maybe my wife is right and I am obsessive.)
I started developing new house curves for my IB based on my preconceived “rules”.
1. Start the rise at the crossover frequency.
2. Stop the rise at 30 Hz.
3. Use a flat slope on the logarithmic scale.
After I settled on a crossover setting of 80 Hz, I started dialing in and listening to these house curves. They begin ramping up at 80 Hz and level off around 30 Hz. They slope up +6, +8 and +10 dB:
I wasn’t entirely satisfied with the results. I wanted more low end power, but the more aggressive curves were getting too bassy in the musical range.
So I broke my “rule” number 2. I decided to keep the rise constant, and push the shelving frequencies down a little more. These all slope up from 80 Hz at 6 dB per octave and shelve off at 32, 25 and 20 Hz:
Much to my surprise, I listened and discovered that I liked the changes. I prefer not to shelve off at 30 Hz. Gently rising all the way down to 20 Hz does not sound unnatural to me, and the power I was looking for was there. Still, I felt that the sound was a bit bass heavy in the upper half of the subwoofer range.
So I broke my “rule” number 1. I decided to start the rise below the crossover frequency. I moved the beginning of the rise down to 63 Hz and sloped up from there. At 20 Hz it is up +10 dB.
I have overlayed my new curve over the old to illustrate the difference.
Success! Finally, a house curve that I love. Its lean and mean, natural and powerful. I’d recommend it to anyone with a similar set-up.
As Wayne has long since pointed out, all of this is based on preference, interaction with my room, interaction with my mains, and the behavior of my subwoofer. The “rules” that I broke were self imposed. Wayne's write up has always encouraged experimentation with all of these parameters. I've proven to myself that such experimentation pays off.
To match a target response I:
1. Measure the unfiltered response at four seats and use the average response.
2. Increase the subwoofer gain to get the desired level at 20 Hz.
3. Set a deep, wide filter at 1.00 kHz to adjust the response level around the crossover.
4. Add filters to eliminate the peaks.
Here's the subwoofer target response with an 80 Hz crossover. (This graph is not smoothed.)
I have not exhausted all of the possibilities by a long shot. For example, I have only explored straight lines. But I’m homing in on what works best for me.
Please share your ideas and experiences. Play with it. You have lots of options!
Thanks to Wayne, Sonnie, John and Bruce.