What Can I Do to Make the System Sound Better?

Simple tips and techniques to help you get the most out of your system.

Oh, the quest for the holy grail of high-end car audio and contesting: How to build the best sounding, best scoring system possible. Ever been in a discussion on this kind of topic? Yep, I thought so. Got all the answers to the question? Me neither! But I’ve got a few things we can think about, and, in the process, maybe we can learn more about how to accomplish it.

Questions like this one have been circulating around quite a bit in the CAR SOUND & PEFORMANCE 12-Volt Forum lately. There have been several specific topics that have been pretty hot. These are the ones I’d like to spend a little time discussing here. We cannot possibly cover each in great detail, but, hopefully, these brief discussions will spur you to search for more complete information and help you improve your system’s performance.

Gain Structure and Level Setting
This is the one topic that more competitors and high-end installers have been asking about than any other recently, and for good reason. It’s one of the most important parts of critical system tuning. And, if done improperly, it can have as much, if not more, negative effect on the sonic performance of the system than any other part of the tuning process.

How often have we heard systems that sound compressed, have very little dynamic capability, high distortion levels, and the volume reaches levels too high to stand when the volume control is only 1/4 of the way up? It’s a pretty common practice to set a system’s gains at 1/2 to 3/4 up because that seems to be a good spot. Or, maybe we try to use our ears with some dynamic music and attempt to dial it in. While we may get really lucky and get it right by doing it this way, it really is almost impossible to do without using a good technique and some basic test equipment.

Proper gain structure will give the system its highest possible signal-to-noise ratio, best dynamic range, full use of the volume control, and minimum distortion levels. It will ensure that your system’s performance isn’t degraded because one component is over or under driving the following component, and that all the components are working together most effectively.

We don’t have the space in this column to cover all the specifics of performing a complete gain structuring sequence of a system. For that, you can check out the Autosound 2000 Tech Briefs. There are a couple of articles on gain structuring and level setting available through the Web site (www.autosound2000.com). Richard, David, and Patrick developed the technique several years ago, and I haven’t even heard of another technique that’s as simple, complete, and fast. It doesn’t matter how complex the system is, all that’s needed to level match any system is CD #104 from Autosound 2000 (about $15), and a small self-contained amplifier from Radio Shack (around $12). If you want to get really critical, an oscilloscope can be of great help, but it isn’t a requirement.

Essentially, you’ll play the specific tracks on the CD, listen to the output of each component through the little amplifier, and level adjust each component so that maximum level is reached without audible distortion. Even the most complex system can be completely level matched in under an hour. I know of several car audio systems considered to be among the best in the world that have been dramatically improved by using this technique. It’s so simple and effective it’s almost disgusting. Get the articles and give it a try! You’ll like it!

Equalization
While we’ve covered this topic in the past, equalization is still one of the most misunderstood and least practiced parts of system tuning. The ability to dial in correct spectral response is a learned skill. It’s not something that certain persons are just born with the ability to do. Anyone can learn how to do it. It’s really not that difficult. It just takes some time, dedication, self-confidence, and the desire to have some fun.

First, learning to use our ears instead of relying on an RTA or other measurement tools during the final stages of equalization is of paramount importance. Even with the great strides in computer technology, no measurement system in the world can hear the way the human hearing system can. Even though current measurement systems can detect very minute variances in frequency and time response, and they can be of great assistance and provide some excellent insight in the hands of an experienced user, they don’t always tell the whole story as to how we will perceive the sound. While they can help, rarely is anything more than a good pair of trained ears needed to equalize a car audio system.

Of course, we know we must have a solid aural reference, both with live and recorded music, on which to base our equalization decisions. Any questions on establishing a reference can be answered by referring to past articles in CAR SOUND & PERFORMANCE. Suffice it to say that without a solid, accurate reference, everything else simply will do you no good at all. If you don’t know what it’s supposed to sound like, how can you possibly tune the system to sound accurate?

Another critical part of equalization is training your ears to detect, recognize, and help you fix variations in the spectral response. This is a lot easier than you might think. Here’s a very simple technique you can use to train your ears. It’s very simple, but very effective, and a whole lot of fun.

The equipment needed includes a single channel of a home or studio system (amplifier and speaker), two identical equalizers, a CD player, and some music that you’re very familiar with, preferably high-quality recordings of some simple music like a jazz ensemble, symphonic performances, spoken word, piano, etc.

Wire the two equalizers in series with the single channel of the system. Extend the wires on one so that it can be placed in a listeners lap several feet in front of the speaker. Place the other EQ so that the listener cannot see the settings on it. Now, set both EQs to flat, and ensure that the speaker output is the same when the EQs are either bypassed or engaged.

Now, a second person makes a change on the hidden EQ. Start with simple, single frequency band changes. Then, the listener attempts to “correct” the change on the hidden EQ with the one in his/her lap by making an equal but opposite change. You can switch between the normal, unequalized sound and the equalized sound to compare the two by switching the EQs in and out of bypass mode. When they sound the same, you’ve got it. Now try some more complex changes.

I promise you, if you practice for an hour, you’ll be amazed at how quickly you can learn to detect very small variances in frequency response. It’s a lot of fun, and is very practical preparation for blind equalization in a car audio system. Give it a shot!

Reflection, Absorption, Etc.
A number of forum regulars have been exploring these topics lately. That’s great! These topics have not received the attention that they deserve until recently. They can wreak serious havoc on a system’s performance, even when everything else is set up properly.

Try this experiment. While sitting in a large room, have someone walk slowly towards you from the side or behind and bring a board (a reflective surface) or a foam pad (an absorptive surface) closer to your head. You’ll find that you can tell there’s definitely something there that isn’t supposed to be there. Sound familiar? Something like the windows or head rests in a car? Yep! The effect of different surfaces in close proximity to the listener and the speakers cannot be neglected in a serious, high-end system.

There are several key considerations that can be applied in every system. First, glass is the enemy! Actually, any hard, reflective surface in close proximity is bad, unless it’s designed as part of the dispersion pattern control for the speakers. A reflection off the side window can significantly shift the images, the soundstage definition, and the spectral characteristics. Placing the high frequency drivers on top of the dash or even above the dash can generate large amplitude, causing early reflections off the windshield. Hard surfaced headliners also cause significant early reflective energy to arrive at the listeners’ ears.

How can we combat these effects? First, place the speakers so that their dispersion pattern can be more effectively controlled. Kick panels are a great place to start for more reasons than just path length differences. That area can prevent the sound from creating a significant early reflection off the windows and can allow for absorption to be placed around the speakers, helping attenuate unwanted off-axis sound before it even gets to the windows. A little absorption near the speaker goes a long way towards improving overall performance. Also, try adding some absorptive material on the door panels and headliner if you have an all leather or vinyl interior. Simply replacing a leather headliner with a cloth one can make a tremendous difference in how the vehicle sounds.

The basic idea is to eliminate surfaces near the ears, or to, at least, minimize their effect on the sonic performance of the system by either absorbing reflections or directing them to areas other than the listeners’ ears.

And So On...
As stated before, there’s no way to completely cover each of these items in such a short article. However, they all must be addressed in order to maximize the system’s sound quality performance. My best recommendation is to do some research, read up on them, get involved in the CAR SOUND & PERFORMANCE 12-Volt Forum discussions, attend classes if possible, etc. Then, when we talk in the future, we can all exchange information and learn from each other.

One additional thought... If you think we have problems with these things in the two-channel environment, think about these things and how important they will become when we start doing multichannel systems. It’s going to be even that much more fun!