| Author | FAQ-Mounting Locations |
| Mr. Brownstone
Head Honcho Joined:
Nov 16, 2001
|
 Posted:
2001-11-19 21:03
The location of speakers determines whether you will hear directly what is being produced, or a reflection or off-axis emission. For the most part, we try to emulate a recording studio or home sound system when trying to accurately reproduce music in the car. The major downside is that cars don't have good acoustics like the home. In the home, you can place speakers an equal distance from your head, the bass is always coming from in front of you, and since there are no walls close to the speaker, there is little acoustic disadvantage to speaker placement. In the home, we also have benefit of having a power station and large enclosures at our fingertips. We have 110 Volts @ 30 amps (3300W/6600W RMS/PEAK) and the benefit of being able to make the subwoofer enclosure as large as we need to harness the maximum potential of the woofer. In the car, we have dashes, doors, trunks, driver's side, passenger side, windshields, cabin gain, road noise--in fact, Why the Heck would anyone want to bother with a car? It takes 1 hour to hook up a theater quality home stereo, and 100 hours to do it in the car! Therefore, we need to utilize some general installation methods to make a car optimized. Or, at least as optimized as possible. MUSIC IN FRONT The front component or coaxial speakers should be in front of you as possible. In most cases, the dashes aren't shaped so that you can just drop in a tweeter & midrange so that they are facing directly back at the listeners. Therefore, we need to place the speakers in another place--like the kick panels or the doors. The kick panels are preferred because they allow the maximum distance from the ears. The farther you can get the closest speaker away from you, the less stereo bias there will be. Aiming both left & right speakers upward toward the domelight area seems to yield the best imaging, staging, and least cancellation. This is no easy task, however. Kick panel replacements (or custom made fiberglass ones) are usually necessary to assure the proper aiming of speakers. Whether you go with 2 way components/coaxials or 3 ways, the placement is the same. When using a 3-way system, you can aim the smaller midrange & tweeter towards the domelight/roof, and the larger midbass driver can be in the door with limited detriment. Of course if you want to put it in a kickpanel or the floor, be my guest. SUBWOOFER PLACEMENT This is usually where we get the most debate and hostility between audiosnobs and those of us that live in the real world. A lot goes on in our mind when processing sound. Since our directional hearing and most sensitive detection occur between 400Hz to about 5kHz, the speakers that produce those frequencies are most important with placement. In fact, most high-end components have only one driver producing those frequencies--one speaker = seamless sound. Keep in mind that at lower volumes we are less sensitive to frequencies above & below that range--making it increasingly hard to satisfy our listener. This is why a lot of head units have a LOUDNESS feature. Using the lowest setting of loudness is perfectly acceptable since it's effect rolls off at higher volumes Bass, is not that picky. We can place the speakers in front of us, behind us, on top or below. I'd shy away from above & below because in a car, cancellation would be high. (Danged acoustics!) Since 99.9% of all subwoofers are placed behind the vehicle operator & his/her passengers, let's assume we're all going to put woofers in the trunk or extended cab section of a truck. SIDE NOTE: If you have a pick-up and no extended cab, trade it in or sell it at the first opportunity. This will make it easier on the both of us. Thank you. SUBWOOFER PERFORMANCE Let's assume that you have decided to design your woofer enclosure to be sealed. This simple design will allow for optimum control of the woofer, while also offering a baseline for performance. Placing your subwoofer enclosure in the trunk of your vehicle facing the rear of the vehicle minimizes on cancellation. When 2 independent waves meet, they cancel or sum their amplitude depending upon what phase they are in. In most cases, placing the woofer box to face the rear of the vehicle will improve frequency response below 60Hz compared to facing it frontward. As long as you have signal processing (EQ or head unit with bass controls) you can compensate for acoustic loss/gain. In most cases, cutting the strongest frequencies (usually 45Hz-55Hz) will balance out the freq resp and at the same time avoid additional distortion caused by over-boosting signal. Finally..... REAR FILL I'm only going to briefly cover this topic since so many people are unaware of benefit of speaker placement until they've actually tried it. Back in the olden days (circa 1988-90) the availability of Real Time Analyzers (RTAs) were the power capacitor of their time. Everybody who owned a store had one, or should have one, right? What these devices would do is tell you the car's frequency response based on a reference signal. To perform the test, pink noise (the sound of that static when dialed between radio stations) which is usually recorded from 20Hz-20kHz in equal amplitudes. When playing pink noise through your stereo system, you'd be able to detect, with the help of the RTA and a microphone, what type of response you should have. Ideally, a flat response from 20Hz-20kHz would be desirable, but would be unlikely. Due to the acoustics of a vehicle, there would be lumps (cabin gain) and dips (cancellation, and poor speaker placement). Another problem is that an RTA can't tell you if the sound is entering the mic in phase or not--only it's intensity. Car audio stores jumped on the bandwagon and immediately sold you a speaker for every dip in your system, and a signal processor (eq) for every lump. An RTA was the best moneymaker in car audio since the 1F digital capacitor. We'll go there later. An artifact of this is that in the car, there's a dip from 150Hz to 400Hz when placing speakers in the doors and not aiming them properly. Therefore, the most profitable solution is to sell another set of speakers, rather than convince customers to properly place speakers and soundproof their doors. In fact, that's what happened. Pretty soon, everybody had REAR FILL speakers to compensate for this anomaly. One person copied another (just like capacitors) and soon, every audiosnob had them--even if they didn't know why. In today's (2001) car audio scene, enter the DVD and DTS5.1 surround sound processing. Even though I say, "WATCH THE DAMNED ROAD, KID!!", you folks insist in putting monitors & DVD or VHS players in your vehicles. Since movies usually have surround sound encoded on the tape/dvd, having rear speakers in your car is actually beneficial to your sound system when viewing movies. And with DTS5.1 about to hit the shelves, it'll be advantageous to have rear speakers for regular music--just as soon as everybody is recording in the DTS format. Don't expect that to happen any time soon, but when it does, it should be grand. Personally, I'll be the second to last person to make the 'upgrade' at that time. (PS this article was written 3 years ago, and Im still waiting for Limp Bizkit to record a DTS5.1 CD.) |