2012年2月20日星期一

The Questions and Answers on Car Audio

The Questions and Answers on Car Audio

Have you ever come across any problems about the oem car stereos? As we all know, the basis of the knowledge on auto audio is the both audio engineering and physics. Here you will get the answers of the most frequently asked questions on the car audio. Some may seem very familiar to you. Getting yourself equipped with the knowledge on the most of the car audio problems can get you on the right way and maybe you will gradually become an expert in the field of car audio.

What means an ohm?

An ohm is a unit of measurement that quantifies the amount of impedance in a speaker. Impedance can measure a speaker's resistance to the flow of current.

What do you know from linear excursion?

When given two subs with equivalent surface area, the sub with larger excursion capacity is able to produce louder sound volume if adequately powered.

What is the meaning of a subwoofer preamp RCA output?

A subwoofer preamp RCA output comes with a built-in low-pass crossover for specific connection to a subwoofer amplifier.

What can the sensitivity rating tell you about the speaker?

An efficiency or sensitivity rating gives you information about how effectively a speaker converts power into sound. The higher the number is, the more efficient the speaker and the louder it will play when given the same input power. The more efficient sub can get more power from the amplifier.

An efficient speaker assists you in maximizing your available power. Most sensitivity ratings measure the speaker’s output with 1 watt of input, 1 meter from the speaker, while some speakers’ sensitivity is measured with 2.83 volts of input.

Efficiency can not indicate a subwoofer’s output capability precisely and we should not use it as comparison to other subwoofers to see which one is “louder.” However, physics tells us that a 3 decibel drop (3 dB) in sensitivity doubles the amount of wattage required by a speaker to produce sound at the same volume. That is to say, a 90 dB speaker will need double the amount of wattage as a 93 dB speaker when both speakers have to produce the same volumes.

Do you know the difference between peak power and RMS power?

Peak power handling is referred to as the amount of power which a speaker can handle during a brief musical burst. The RMS power range figure is a very reliable rating in the aspect of determining the speaker’s power requirements.  Speaker power is measured in watts. One watt is equal to one volt times one amp, or one joule of energy per second.

What is really CD signal-to-noise ratio?

The signal to noise ratio can measure how well the CD player silences background noise. Higher ratings in DBs is an indication of less noise and crisper sound.

What do preamp RCA outputs mean?

Preamp RCA outputs give you the allowance to connect 1 or more external amplifiers. The subwoofer output is an important feature as it offers you cleaner low frequencies for your subs in comparison with a standard front or rear set of outputs.

What does sound pressure level mean?

SPL is short for sound pressure level. The SPL is measured relative to 0 dB, a constant number. 0 dB means the smallest amount of sound pressure that can be recognized by the human being. The speaker’s listed sound pressure level is in usual case a prediction based on the speaker’s weight, voice coil, magnet strength etc, which is made by the manufacturers. Since it is just a prediction, we should not pay much attention to it or even make no notice of it.

What can Xmax tell about a speaker or subwoofer?

Typically is measured in millimeters. Xmax value is the measure of a speaker cone’s maximum excursion in one direction, which still maintains a linear behavior. This is an indication of a subwoofers' flex capacity and correlates with bass reproduction.

What can you know from the speaker’s frequency response rating?

The range of frequencies the speaker will reproduce, from lowest to highest. When the range is wider, then you can get better effect. The optimal range is 20- 20,000 Hz. It is also the range of human hearing.

What are voice coils?


Voice coils can receive an amplifier’s power signal and move the subwoofer cone in and out, producing sound. Dual voice coil subs come with more wiring flexibility than single voice coil subs. But you have to pay attention to that single voice coil subwoofers are easier options for wiring multiple subwoofers in parallel or series. You may also run a dual voice coil (DVC) sub in parallel, series, or combination. A quad voice coil features four voice coils and equals two dual voice coil subwoofers as far as wiring goes.

What means impedance?

The load value in ohms stated per voice coil. It is the amount of resistance to the current flow. This is a key specification as subs wired in parallel or low impedances can create problems with your amplifier and potentially void all warranties.

What does it mean that an amplifier is clipping?

Clipping refers to distortion which is produced by an amplifier because of a lack of sufficient power. When pushed beyond its maximum powering capability, the amplifier produces square waves, causing distortion or results in a fried amplifier.

What does CEA-2006 compliant mean?

An amplifier is CEA-2006 certified when tested by the Consumer Electronics Association. This certification represents the accuracy of the amplifier ratings. The amp is compliant with the CEA 2006 standard. The RMS rating and the signal-to-noise ratio are the two main ratings that are verified by the CEA 2006 test.

Can you tell the difference between wiring speakers "in series" and "in parallel?"

In series, each speaker you add will increase the resistance, or Ohm load, in the channel. Add up each speaker’s impedance to get the total impedance. So the sum of two 4 ohm speakers in series is equal to 8 ohms of total impedance. The higher the impedance an amplifier runs at, the smaller the amount of power flow. Many amplifiers can run at either 2 ohm or 4 ohm loads, while some are stable at 1 ohm loads for optimal RMS performance. To connect speakers in series, link the positive lead from speaker 1 to the amplifier’s positive terminal, and link the negative lead from speaker 1 to the positive lead of speaker 2. Link the negative lead from speaker 2 to the amplifier’s negative terminal.

 In parallel, each speaker you add will decrease the resistance in the channel. The sum of the inverse of each speaker’s impedance is equal to the total impedance. So two four ohm speakers in parallel is equal to ¼ + ¼ = ½ ohm. Knowledge of your amplifier’s capability and ohm rating is needed in order to decide on the wiring configuration. Knowledge of your speakers ohm rating (usually 4 ohms) and the number of voice coils is needed as well. You should generally limit your amplifier usage to two speakers per channel. To connect speakers in parallel, connect each speaker’s positive lead to the amplifier’s positive terminal, and connect each speaker’s negative lead to the amplifier’s negative terminal.

Hopefully, you have already a better understanding of the car audio and are able to solve the problems on your own after going through the Q&A on car audio. More information can be found on Oem Car Gps.
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