It helps to be completely immune to pink noise if you aspire to fine tune your system with sophisticated equalizers a dubious benefit of installing pro systems for any length of time. My poor wife, I think she ran out of the house screaming and pulling her hair out, but after an hour or so I had dialed in a nice, flat response curve. I popped in a CD and sat back to enjoy the wonders of a perfectly tuned system. But horror of horrors, it sounded awful! It was all thin and shrill-sounding with virtually no bass. Where had I gone wrong? If I had bothered to consult the AudioControl manual before I fired up the pink noise, I would have known I was headed for disaster. When you play music through your system at this point, you might not be completely pleased with the result. Recalling my experiences from a few years earlier, I recommended that these folks try a shelved house curve instead of flat response, and most seemed happy with the results. What exactly is a house curve? Yet their definition is not as clear as it could be. Simply put, a house curve is perceived flat response as opposed to measured flat response. Since no two rooms are alike, the million-dollar question is: How do you determine how much of a slope you need for your room? On various home theater forums you will find people recommending all sorts of methods for acheiving a room curve. Feel free to ignore such advice. The problem is that an ideal house curve varies from one room to the next. The rule of thumb is, the smaller the room, the steeper the slope needs to be. Yes, that point has already been made. Above 50 Hz the meters are reasonably flat, albeit miscalibrated by a decibel or two. The first thing you need to do is use an equalizer, preferably a parametric model, to get your subwoofer's response reasonably flat. By that I mean eliminate as many peaks and low points as possible. The idea is simply to get as smooth a response line as possible. Go for the approach that uses the fewest number of equalizer filters. With response smoothed, the 100 Hz tone will probably sound louder than the 30 Hz tone. Thus it has to be subjective. Your room does it all for you automatically - great news for those of us who are mathematically challenged! Dialing in your house curve If your baseline frequency response i. However, if your base response is such that smooting out the peaks and valleys gets you nearly flat response, the easiest way is probably to apply a shelving filter. However, our esteemed Administrator Emeritus brucek came up with an innovative way to effectively create one. After equalizing his subwoofer he also found a need for a shelving filter to precisely dial in the slope he needed. Take a look down at the subwoofer range and you can see the effect it would have on a flat response curve: A 4-dB drop between 30 and 100 Hz, with response flat shelved below 30 Hz. For instance, if your equalized response already has something of a downward tilt, this filter might be ideal for you, to increase say, a 6 dB slope to 10 or 11 dB. That could be accomplished by cutting the pictured filter even deeper, but you would end up with response that continues to rise below 30 Hz, not shelving at that point more on that shortly. To get a steeper slope and retain the 30 Hz shelving, you would need a tighter bandwidth, with the center frequency moved down to a lower frequency. NOTE: You can effect a by applying a couple of extra filters to the shelving filter. The idea is to get as straight line as possible between them. See if you can find some music where the bass line ranges from very low notes to very high. Ideally they should all sound the same from note to note — no hot notes, no weak notes assuming the recording is good to begin with. Adjust your slope as you feel is needed. You may need to move the point where the curve starts to a higher or lower frequency. You might not need straight-line response between the starting frequency and 30 Hz; you might need a line with a sag or a hump. Whatever it takes to get those bass lines running smooth from top to bottom, that's what you want. If you set it for a higher volume than you normally listen to, it will sound bass-shy when you turn it down. The inverse is true if you house-curve for too low a level. Earlier I mentioned shelving your house curve. I personally prefer to shelve response at about 30 Hz rather than allowing the curve to continue rising. I initially kept the slope rising all the way to the bottom, but I found there was an overabundance of ultra-low energy. Certainly did not sound natural. Shelving response at 30 Hz solved that problem. Who needs bass shakers? We saw in the first section that a house curve will be steeper for small rooms than for large rooms. With touring acts that play in a different venue every night, the ability to tune a system to various auditoriums is a vital necessity. In those places, most of the audience is a considerable distance from the speakers. Due to the loss or attenuation of the upper frequencies over distance, a sound system in a large room, when properly tuned, will compensate for that loss by boosting the upper frequencies. As a result, these large rooms typically require a fairly flat response curve to 12 kHz or so very few sound reinforcement speakers extend all the way out to 20 kHz. At home we have exactly the reverse situation. Therefore we must compensate with a tilted response curve that reduces the highs and emphasizes the lows. In other words, we need a full-range house curve, from the highest to the lowest frequencies. The truth is, any audio system that demonstrates balanced octave-to-octave performance has an ideal full-range house curve, and it would be verified with broadband frequency spectrum readings. It may or may not have been an intentional goal when the system was set up. I ultimately found a full-range curve like this to be a necessity when I dialed in my own system after acquiring my AudioContol EQs and RTA. From an arbitrary 0 dB reference, upper-frequency response dropped 8 dB from 160 Hz to 10 kHz a 6-octave span , while bass response rose 8 dB from 160 to 32 Hz 3 octaves. Also note that between my usual reference points for a subwoofer house curve, 100 and 32 Hz see Part 1 for details , the rise was only 6 dB, a relatively shallow slope. This is because the room was very large — over 6000 cubic ft. How does cabin gain figure in? What happened to these two hapless individuals? They sounded perfectly balanced and he was a happy camper. But in his new, larger place the effect of cabin gain is working against him. To restore the missing low end he will need to increase the bass output of his speakers via the tone controls, or perhaps trade up to some larger speakers. The second person has the opposite problem. If his speakers sounded great there, you can bet the bass will be killing him in the smaller room — and it is. So, you can expect changes like this anytime you move your speakers to a larger or smaller room. You can minimize this phenomenon by being aware of how cabin gain works in small vs. Specifically, when you audition speakers at a dealer, the size of their demo room, relative to the size of your room at home, is a vastly important factor that you should take into account. Is that clear as mud? What you are doing, in effect, is dialing in a full-range house curve by the selection of your speakers. The satellite speakers must to have enough bass output in your room to blend with the subwoofer. Or at least they once did. Polk used to break down their home theater systems for small, medium and large rooms, for on-wall satellites, bookshelf and floor-standing speakers respectively. Unfortunately they have generally discontinued this practice for the more generic recommendations mentioned above. Simply put, the larger your room is, the larger your speakers need to be, with larger or more bass drivers in order to sound balanced. NOTE: Fellow Shack member Spridle tried a somewhat different approach that he was very pleased with, keeping response fairly flat down to the point where the sub takes over. Here's his thread on the subject: Part Three Answering house curve critics Every theory in audio has its proponents and detractors. A house curve built into recordings? One thought critical of house curves is based on a rather idealistic concept of the recording studio environment and exactly how it affects our program material. The mixing engineer is listening to either nearfield monitors or other speakers when he is laying out the final 'sound' of the music that is being mixed down to two or more channels. Neither the booth nor the mixing electronics should add or subtract from the sound on the master tape. If you wish for your home system to be accurate, it needs to be as flat as the one they used in the studio. If not, the engineer is simply going to compensate with equalization of the program material. Good engineers know that their room and speakers of choice will affect their final mix. Another thought critical of house curves acknowledges and indeed embraces the fact that they come into play in the production stage. Therefore — once again - we should set up our systems with response as flat as possible, otherwise nothing will sound right. Furthermore, the question needs to be asked: which house curve are they using in that mixing studio — small room, large room, or something in between? After all, the engineer can reasonably expect that his CD will be played back in cars, dorm rooms and living rooms. What about the DJ spinning tunes in a huge hotel ballroom or at an outdoor event? A Fletcher-Munson house curve? Other room curve skeptics base their doubts on the Fletcher-Munson curves, which show deficiencies in human hearing at the lowest and highest frequencies. They claim that studio engineers, being human themselves with the same auditory deficiencies, compensate for that in the recording process. Do you think he would increase them to compensate? Of course he will. If your playback system has a curve attempting to compensate for a frequency response associated with human hearing, what do you think the results will be when you play back material that was mixed and prepared on a flat system? The Fletcher-Munson curves show how our perception of bass and treble frequencies change with variations in volume levels. That is a wholly separate phenomenon that has virtually nothing do with a house curve, other than the fact that it's best to calibrate your system at the volume level you use most. It may be inadequate at lower volumes, and it may be overly intrusive at higher playback volumes. I have not found this to be the case at all. The movie industry settles the issue We can look to the movie industry to see the inherent problem with these lines of thinking. As industry pro Tomlinson Holman explains , the X curve is used in both theaters and dubbing soundstages. Interchangeability of X curve material with home video can be handled with a simple re-equalization. There is no industry standard for the physical size of a movie theater or a dubbing stage, yet they apply the same house curve to all of them. And indeed we can see the discrepancies it generates in the DVDs we buy. Sound editors are forced to compensate both for a curve that might be inappropriate for their dubbing stage, and the inherit shortcomings of the X curve, such as the roll-out of the low bass frequencies. If it goes for movies, the same is true for music as well. Related articles: Thanks to: brucek for his excellent Excel program, from which we created our charts. Donna Pflughaupt, for creating the Excel charts. Cookie and Data Use Consent We use cookies to improve your experience on this website and so that ads you see online can be tailored to your online browsing interests. We use data about you for a number of purposes explained in the links below. By continuing to browse our site you agree to our use of data and cookies.
