This article expands on the Team-BHP Guide to Basic car audio.
By now you should have mastered the art of matching a head unit (HU) to an amplifier and selecting speakers to suit your taste and needs. In this section we will discuss systems with multiple amplifiers, additional processors and special bass-enhancing loudspeakers.
- Head Unit: Now that you are considering an advanced system, you should think of buying a head unit that has three sets of preamplifier outlets. These “outs” let your HU control multiple amplifiers and each set of outs includes plugs for the front, rear and subwoofer speakers. This type of HU permits external audio sources like Walkmen, MP3 and DVD players and may even include proprietary cables to control Apple IPods. Most major manufacturers offer HUs with these features at prices starting around Rs.10,000.
- The advent of CDs has almost eliminated the need for external equalizers and processors. In fact, we don’t recommend them for car audio because we find that they are overused and will deteriorate rather than improve sound quality. Remember, every extra audio component in a car is another possible entry point for electrical noise from the alternator. Modern HUs come equipped with sophisticated tone controls that compensate for most in-car anomalies.
- Speakers: You will need at least four speakers to reproduce the typical sound range, as discussed in the Team-BHP Guide to basic car audio. For high-end systems we recommend installing a separate speaker called a subwoofer for the lower bass frequency. A subwoofer is a large speaker with a diameter of 10” or more; you can use two speakers for stereo sound but if space is a concern a single unit will do. A subwoofer will reproduce only the bass frequency and is usually placed in the trunk of a car. Some well-known brands include Pioneer, JBL, Boston, Infinity, Image Dynamics, Polk, MTX, Kicker and Focal with prices starting at Rs.4,000.
Subwoofers produce a lot of energy and this energy can cause door and trunk panels to vibrate. To dampen this vibration you should use foam-based panels from companies like Dynamat. For tighter spots we suggest a spray-on dampening like that offered by Wurth. - Amplifiers: Now that you have a subwoofer, you’ll need enough amplification to drive it. The easiest way is to get a four-channel amplifier: bridge two channels to drive the subwoofer and use the other two channels for your front speakers. Your rear speakers can be powered directly from the HU.
On the other hand, if you prefer to have all your speakers powered by an external amplifier you’ll need five or six amplified channels. You can get this by using a single five- or six-channel amp, a four-channel amp with a two-channel amp, three two-channel amps, six separate mono amps or any other combination. For multiple-amplifier setups you will need not only the wires discussed in the Team-BHP guide to basic car audio, but also a distribution block with fuse holders and power wires of at least four gauge size.
One final note: the choices and scale of car audio equipment at this level is quite varied and the best solution depends entirely on your own personal preferences. You can add CD changers, DVD players, video screens, multi-channel processors for home theater sound and much, much more. Soon we will see the advent of satellite radio – some head units already include tuners for XM, HD radio and Sirius. The sky, as they say, is the limit.
For more information, take a look at the Car Stereo cookbook.
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Speakers:
At the advanced level, the front speakers should be component speakers. The rear speakers can be co-axials in the case of owner-driven cars. If the owner usually sits in the back seat, the components are best put in the back.
Components can be:
- 2-way components - A mid-bass & a tweeter, controlled by a 2-way crossover, or
- 3-way components - A mid-bass, a mid-range and a tweeter controlled by a 3-way crossover.
In the case of some entry-level 2-way components speakers, the crossover is substituted with an in-line filter that gets most of the job done (frequency separation) at lesser cost.
Some 2-way crossovers allow bi-amping, which means that the mid-bass and the tweeter can be powered separately by an amplifier. Here, 2 4-channel amplfier (at least 4 channels are needed for this) is configured so that 2 channels feed the tweeter, and the other 2-channels feed the mid-bass. Biamping allows a lot of flexibility and creativity in tuning the sound.
Similarly, 3-way component speakers can be tri-amped, depending on the capabilities of the Head Unit and the crossovers.
Component speakers sound best when they are powered by an amplifier. The power output from a Head Unit will not bring out the best in components.
Once component speakers are amped, the area where the mid-basses are installed (usually the front doors) will need to be damped to eliminate vibrations.
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Installation of component speakers
2-way components:
Installation of 2-way components is easy (except for the additional wiring hassle).
- Positioning: The mid-bass is installed in the doors, and the tweeters are installed at the point where the A pillars meet the dash (or nearest to this point).
- Aiming: The tweeters are aimed at the head-rest or seatbelt harness of the opposite side (so that the path of the two tweeters will cross a bit forward of the gear lever). Proper aiming of the tweeters help in good staging of the sound -- the sound will appear to be coming from the front of the front-seat passengers (at at least chest level).
- Wiring: The output from the amp is wired into the crossovers. The crossovers then give separate output to the mid-basses and the tweeters. It is generally recommended that the length of wire from the crossovers to the tweeters & the midbasses be as short as possible, for best effect.
- Power: For best results, feed the components the continuous power in RMS that they are rated at. A little more power than the minimum rating will be even better, as long as the gains are set so the speakers are not driven to distortion at 90-100% of the HU's volume. Though this is the best scenario, we may not always be able to feed the components their minimum rated RMS power (budgetary limitations for amps). But aiming to feed at least 80% of the speaker's minimum RMS power will be a good idea.
3-way components
Installation of 3-ways is more complex, simply because of the possibilities that exist.
- Positioning & Aiming: The midbass is usually installed in the front doors. Positioning/installation of the midrange & tweeters is an article unto itself.
The midrange and tweeter must be installed as close to each other as possible. And generally, they should not be installed more than 8-12 inches away from each other, with 12" being the maximum. The output from the midranges and tweeter have to blend well for best results. If they are installed far apart, the output may not sound very coherent.
Both the midrange and tweeter must be aimed at the head-rest of the opposite side (from the side of their installation) for best effect (for two-passengers). If the driver is a real audio nut, and he wants the best soundstage for himself, the passenger-side midrange and tweeter must be aimed at the driver's headrest.
For really good effect, path-length differences (a separate story for another day) should be accounted for as much as possible in installation. That is, the length between the LHS midrange and tweeter and driver's headrest, and the RHS midrange and tweeter and the driver's headrest must be as close as possible. For this, kick-panels are used. The midrange and tweeter are installed in custom enclosures/panels called kick-panels (as they are fitted next to where the driver's/passenger's feet will rest in the footwells). The kick-panels (LHS & RHS) are aimed toward the driver's headrest. Some HUs/Processors have settings to adjust path-length differences.
The midrange and tweeter can also be installed at the base of the A-Pillar and aimed like in the 2-way component installs.
If aimed properly, the Mid-bass, the midrange & the tweeter can be installed one above the other on each doors, for maximum coherence of sound (and a cool look when the door is opened).
[Of all cars in India, the Santro is the car that gives the best install possibilities (in stock locations) for 3-ways. The mid-basses can be in the doors, the midranges in the dash pods, and the tweeters can be in the dash near the A-pillars, or mounted in the dash above the midranges. The midranges and the tweeters actually fire directly into the cabin, and with some install magic in the pods, they can be decently aimed too.] - Wiring & Power: Same as two-ways. Except here, more power (10-20% over and above the minimum continuous RMS rating of the speakers) would be a real blessing.
