One of the latest suggestions for a new project car came from CA&E's senior editor Brook Howell:
If I may add a suggestion on the small car theme: a Smart car! I saw something in the news that DaimlerChrysler wants to start selling them in the U.S.
The Smart fortwo is a tiny 2-seater, 30-cylinder 40hp diesel that we have had up here in Toronto for years. I had not considered the car, even though Brook's comment reminded me that every single American student that comes up here says, "I wish we could get cool cars like that in the states." This purpose-built car is really pretty cool, but the obstacles add up just as fast. One main obstacle is size, requiring a minimal system that could sound great, but would not be as impressive as some of the rolling showrooms prowling around today. Would you rather see a big system or a cute little system? [My vote is for cute, e.g. the Arc Audio Golf Cart we featured in Feb. '05. -B.H.
Next obstacle is the vehicle's charging system that would barely support a small selection of audio gear, and due to vehicle size, adding extra batteries would be noticeable in the 19.8 second 0 to 60 mph time. Options like air conditioning would definitely compete with the audio gear for precious electrical supply. The vehicle's empty weight is about 1,600 pounds and allows a maximum load including the driver of 500 pounds. Subtract the average weight for the driver and passenger, and you have about 200 pounds left for audio gear - one sub in a cabinet, speakers and amplifiers could eat that up pretty fast.
Still, this is a cool little rolling coffin that has available a full line of Brabus appearance parts like wheels, pedals, aerodynamic body kits and exhaust upgrades (why?), and carbon fiber interior trim kits. You can dress up the car into a great-looking $25,000 paperweight!
Brook, after all that, I see a major challenge here that nobody would likely be too anxious to tackle - hmm, that might just be reason enough...
I'd like to congratulate you on the best magazine with the best electronics segment in the world! I have a '93 Nissan 300ZX which I plan to set up a sound quality system in. I am looking into using mostly Alpine equipment, starting with a CDA-9857 head unit, SPX 5 1/4" components in the kick panels, 6 1/2" midbass in each door, a 10" sub and PDX amps. My question is how would I go about wiring a center channel? Is it necessary to use an external amp or can I use the head unit? Would it be best to use a specific center speaker like the one Alpine makes for an extra DIN opening? I am anxious to hear what your opinions are. Are center channels overkill? Will the front setup be good enough to use in competition without the center channel? Any info you can give would be greatly appreciated!
Damon
The center channel can be viewed two ways - either as essential or as corrective. In a surround system such as Dolby Digital or DTS, the center channel is extremely important. The center channel delivers most of the main information, and the other four channels (L, R, LR, RR) are more geared towards effects to support the center channel. Whenever you watch a movie, the main actors are usually heard in the center speaker whenever they are in the center of the video screen. You can survive without a center speaker using an imaging technique called "phantom center channel," which is really just "excellent stereo with effects." However, a true multi-channel system has rules, and the rule calls for a physical center channel speaker.
Another main consideration in true surround sound is that the speakers are all matched. In our Media Dynamics Home Theater class, we go one step further and insist that all five speakers in a core 5.1 system be "identical." As an alternative, they must be "timbre matched" which basically means that they sound the same. This is critical in any reasonable home theater, since you need to correlate visible action on the screen to the sounds that support it. For instance, if you had a great set of stereo speakers for your front left and front right channels, and added a little 6" bookshelf speaker for the center channel, imagine how a helicopter flying from left to right would sound-it would have sounded pretty wimpy as the helo passed through the center of the video screen. Is that right?
The phrase used to describe the proper outcome of a theater is "willing suspension of disbelief," meaning the sound and video combination is so realistic, you are willing to allow yourself to be transported into the action so you emotionally believe what is happening on the screen. Providing you avoid buying one of the popular HTIB (home theater in a box) speaker packages, you have a good chance of getting there.
So let's get back to the car - using a matched set of five identical speakers in a car is either difficult or impossible since there are so many rules that must be followed to make believable surround sound work right. For that, we can accept the second alternative - timbre matching. This is harder to do, unless you are buying a brand that makes a center channel speaker intended for surround to go with their speaker lineup. I would bet the Alpine DIN center channel speaker is timbre matched.
In a 2-channel system, however, a center channel is a problem. Multi-channel surround sound requires five speakers or more, but true stereo is a special recording technique called "stereo" that allows two speakers to paint a landscape of sound in front of you. Using a third speaker as a center channel adds phase and timing errors that result in cancellation of certain sound ranges and blurs the image, while at the same time giving you the sense that content is coming from the center position. For 2-channel, many agree with me that a center speaker is a lame way to fix an imaging problem. In competition, I remember points being awarded for a center channel, yet the competitor would lose points in sound quality! In fairness, there are some cars that are just so badly designed that even the best installers can't achieve good imaging without a center channel unless they rebuild the entire dash. In that case, bite the bullet...
So it depends on which system design you have. For a surround system, even the nature of center channel is crucial. I had heard about Alpine's in-dash center speaker and knew that it would be a great product, but I just looked up the product details and found that it is what is often called a d'Appolito configuration, named after Joe d'Appolito. This configuration, also known as MTM (or mid-tweet-mid), places a midwoofer or midrange driver on either side of a tweeter, producing the beloved "point source" radiation pattern. A single woofer and tweeter would cause a polar tilt, where the focal point of the blending between a woofer and tweeter is not directly in front of the speaker set, but about 30 degrees below the woofer. That means if the in-dash center channel had one mid and one tweeter mounted side by side, either the driver or passenger would be in the optimum listening position, but not both. With the MTM configuration, the two smaller midwoofers appear sonically as a single larger woofer with a tweeter dead center, just like a good coaxial speaker, and both the passenger and driver, as well as rear seat occupants, will benefit.
If you need to use a center speaker to augment a 2-channel system, there are three prime rules: First, it must be mono (both left and right channels together). There are several ways to derive a mono signal, such as using a small mono amplifier or using a center channel processor. An old technique was to simply connect the center channel speaker across the correct terminals of the amplifier driving the front pair, much like the mixed mono connection for a single amplifier subwoofer system.
The second rule is that the speaker must be bandwidth limited to just a few octaves of midrange since the key sonic cues for localizing are in the midrange band. However, you now have three speakers in your stereo pair, which causes phase cancellation between the speakers, so by limiting what the center channel emits, you limit the amount of cancellation that can occur. One how-to website suggests incorrectly that the center channel be crossed over at 80Hz, which achieves basically nothing. The bottom two octaves won't be produced at all in a mid-tweeter center channel combination, and everything between 80Hz and around 500Hz will be in a phase fog of confusion. The starting range for a center channel should cover 500Hz to 2,500Hz to produce localization but minimize cancellation.
The third rule is that the center channel must be attenuated or reduced in output until it is just barely noticeable in order to fool people without revealing its presence in the vehicle. In competition cars I judged, I would sit in the vehicle and immediately point to where the center channel was located even if it was camouflaged or hidden inside an air conditioning vent. That should not happen. In a quality 2-channel system, the speakers should appear to be invisible or "transparent," leaving only the soundscape spread out in front of you. All that is required here is to ensure the center channel amplifier has its gain control turned down enough, or in the case of a mixed configuration, a couple of resistors configured as an L-Pad will reduce the center channel speaker's output without knocking the impedance out of range.
While you can often wire a speaker in mixed mono off an amplifier, I prefer a processor and dedicated mono-summing amplifier for the best results and least damage, although they are almost non-existent these days. The AudioControl ESP-3 was one of the most popular, and I still see used ones for sale on eBay. For 5.1 decoding, a wide array of products that will do the job is available from most of the major car audio companies.