everything you need to know about speakers
The human ear is not a perfect audio receiver, but it is the best we have to work with. lnfants can hear sounds approaching 20 kHz As we age, our hearing, like other body parts, loses some of its ability to function. A 20-year-old can be expected to hear sounds near 15 kHz, but it's all downhill from there. There are a few important considerations when deciding on a speaker system that will greatly affect your ability to hear all of the sounds your new stereo can produce. Fortunately, an automobile usually makes an excellent acoustic chamber in which to reproduce sounds (convertibles excepted). Here are the basics:
1. How speakers work. A speaker is comprised of a cone made of paper, mylar, or similar material, which is suspended from a rigid framein a way that will allow it to move in and out of the frame. At the center of the cone, a coil of magnet wire is attached to it and connectedto the radio amplifier. This is the voice coil. A stationary
permanent magnet is mounted in very close proximity to the voice coil in such a
way that a current flowing in the voice coil will cause the speaker cone to be attracted to or repelled from the permanent magnet. The cone will act like an air pump of sorts. It will move in and out at the same frequency as the signal applied to the voice coil, and with an intensity that is determined by the amount of power in the voice coil and the strength of the magnet. Speakers are rated in Ohms (the impedance of the voice coil), Watts (the power handling capabilities of the coil), Frequency response (the range of audio frequencies where the coil is most efficient) and SPL or Sound Pressure Level (a relative measure of overall efficiency). SPL ratings are an indication of how much electrical energy a speaker can transform into air movement. The higher the number, the more efficient the speaker.
2. Power Handling. Until high power stereos became commonplace, most car radios only produced 1 to 10 watts of audio power. If your original car radio used vacuum tubes, it probably had a 4 ohm speaker. If it was an early transistor radio (late ‘50s thru the '60s), it may have had an 8, 10, 20 or even 40 ohm speaker. In any event, it was never intended to handle more than about 10 watts. Your new stereo will eat these speakers and probably won't even burp! You must use speakers capable of handling at least 50 watts RMS. The output of this radio is rated at 44 watts RMS (22 watts per channel) when connected to a 4 ohm load.
3. Magnet size. Prior to WWII, permanent magnets could not be mass-produced cheaply and reliably, so early speakers used an electomagnet which required a great deal of space and power for a little action. After the war, permanent magnets became commonplace and have steadily improved. Still, the size of the magnet determines how far the voice coil can pull or push the cone. Bigger is better for low frequencies where depth of throw is important. To move a large volume of air at low frequencies a long stroke is necessary. At higher frequencies, a shorter stroke is required. less
movement means less return time.
4. Range. Your original speaker had just one cone. It was designed for AM radio. AM radio operates at the low end of the radio spectrum. There is very little space between stations on the dial. In order to prevent one station from interfering with another, the
range of audio signal a station can broadcast is limited to 5 kHz. For this reason radio speakers were never intended to reproduce audio signal higher than 5kHz. Response drops off dramatically after about 8 kltz. Adjacent channel spacing of FM stations is wide wide enough to allow at least 15kHz audio signals, which is the primary reason FM has replaced AM in the high fidelity entertainment market. Today, speakers generally fall into 3 classes: Bass, Midrange, and Tweeter. Bass speakers are the big ones. They have the longest cone travel and the biggest magnets. Cone size is usually 8-15 inches in diameter. Midrange speakers have smaller cones and magnets, but can
reproduce all but the lowest lows and highest highs. Cone size is usually 4-8 inches. Tweeters can't reproduce bass notes at all, but will reproduce high frequency ssignals up to 20 kHz. Modern speakers often have 2 or more cones built into the same speaker housing, often with several magnets to reproduce the full range of sounds. For
instance, our LS4693 is a 6x9 3 way speaker capable of handling 40 watts RMS. It has a 6x9 Woofer with a 15 oz magnet, a 2" Mylar midrange, and a 1" Dome tweeter. It has a frequency range of 40 Hz to 18 kHz with a SPL of 88 dB @ 1W/1M.
5. Location. Most ofus have our ears permanently attached to the sides of our heads and pointed forward. For this reason, the ideal location for stereo speakers would be above the dashboard and at an equal distance from the driver's head, pointed directly at him. This is not generally a practical location. The challenge that arises when installing a stereo radio in an otherwise original car is how to accomplish this without altering the original appearance We have dual speakers that will fit the original opening of many original cars which makes a quick and easy solution - with trade-offs. The 2 speakers must be much smaller than the original in order to fit. The first trade-off then is a loss of low frequency responce due to the small cone size. The 2nd trade-off is the loss ofthe stereo effect since there is not much physical separation between the speakers. A better solution would be to install one speaker in the original front opening, and the other in the rear deck. This would allow larger cones and good separation even if it is front to rear instead of left to right. Another good possibilily would be to place both speakers on the rear package shelf as far apart as possible. This provides good separation, and the trunk makes an execellent compression chamber. If you're not too concerned with originality, speakers in the kick panels or door panels work well.
6. Phasing. The little red dots on your speaker terminals are not smashed mosquitoes! They show which way the current must flow in order to push or pull the cone It is important that both speakers are connected to the proper terminals to insure that both cones push or pull together instead of trying to cancel each other.
1. How speakers work. A speaker is comprised of a cone made of paper, mylar, or similar material, which is suspended from a rigid framein a way that will allow it to move in and out of the frame. At the center of the cone, a coil of magnet wire is attached to it and connectedto the radio amplifier. This is the voice coil. A stationary
permanent magnet is mounted in very close proximity to the voice coil in such a
way that a current flowing in the voice coil will cause the speaker cone to be attracted to or repelled from the permanent magnet. The cone will act like an air pump of sorts. It will move in and out at the same frequency as the signal applied to the voice coil, and with an intensity that is determined by the amount of power in the voice coil and the strength of the magnet. Speakers are rated in Ohms (the impedance of the voice coil), Watts (the power handling capabilities of the coil), Frequency response (the range of audio frequencies where the coil is most efficient) and SPL or Sound Pressure Level (a relative measure of overall efficiency). SPL ratings are an indication of how much electrical energy a speaker can transform into air movement. The higher the number, the more efficient the speaker.
2. Power Handling. Until high power stereos became commonplace, most car radios only produced 1 to 10 watts of audio power. If your original car radio used vacuum tubes, it probably had a 4 ohm speaker. If it was an early transistor radio (late ‘50s thru the '60s), it may have had an 8, 10, 20 or even 40 ohm speaker. In any event, it was never intended to handle more than about 10 watts. Your new stereo will eat these speakers and probably won't even burp! You must use speakers capable of handling at least 50 watts RMS. The output of this radio is rated at 44 watts RMS (22 watts per channel) when connected to a 4 ohm load.
3. Magnet size. Prior to WWII, permanent magnets could not be mass-produced cheaply and reliably, so early speakers used an electomagnet which required a great deal of space and power for a little action. After the war, permanent magnets became commonplace and have steadily improved. Still, the size of the magnet determines how far the voice coil can pull or push the cone. Bigger is better for low frequencies where depth of throw is important. To move a large volume of air at low frequencies a long stroke is necessary. At higher frequencies, a shorter stroke is required. less
movement means less return time.
4. Range. Your original speaker had just one cone. It was designed for AM radio. AM radio operates at the low end of the radio spectrum. There is very little space between stations on the dial. In order to prevent one station from interfering with another, the
range of audio signal a station can broadcast is limited to 5 kHz. For this reason radio speakers were never intended to reproduce audio signal higher than 5kHz. Response drops off dramatically after about 8 kltz. Adjacent channel spacing of FM stations is wide wide enough to allow at least 15kHz audio signals, which is the primary reason FM has replaced AM in the high fidelity entertainment market. Today, speakers generally fall into 3 classes: Bass, Midrange, and Tweeter. Bass speakers are the big ones. They have the longest cone travel and the biggest magnets. Cone size is usually 8-15 inches in diameter. Midrange speakers have smaller cones and magnets, but can
reproduce all but the lowest lows and highest highs. Cone size is usually 4-8 inches. Tweeters can't reproduce bass notes at all, but will reproduce high frequency ssignals up to 20 kHz. Modern speakers often have 2 or more cones built into the same speaker housing, often with several magnets to reproduce the full range of sounds. For
instance, our LS4693 is a 6x9 3 way speaker capable of handling 40 watts RMS. It has a 6x9 Woofer with a 15 oz magnet, a 2" Mylar midrange, and a 1" Dome tweeter. It has a frequency range of 40 Hz to 18 kHz with a SPL of 88 dB @ 1W/1M.
5. Location. Most ofus have our ears permanently attached to the sides of our heads and pointed forward. For this reason, the ideal location for stereo speakers would be above the dashboard and at an equal distance from the driver's head, pointed directly at him. This is not generally a practical location. The challenge that arises when installing a stereo radio in an otherwise original car is how to accomplish this without altering the original appearance We have dual speakers that will fit the original opening of many original cars which makes a quick and easy solution - with trade-offs. The 2 speakers must be much smaller than the original in order to fit. The first trade-off then is a loss of low frequency responce due to the small cone size. The 2nd trade-off is the loss ofthe stereo effect since there is not much physical separation between the speakers. A better solution would be to install one speaker in the original front opening, and the other in the rear deck. This would allow larger cones and good separation even if it is front to rear instead of left to right. Another good possibilily would be to place both speakers on the rear package shelf as far apart as possible. This provides good separation, and the trunk makes an execellent compression chamber. If you're not too concerned with originality, speakers in the kick panels or door panels work well.
6. Phasing. The little red dots on your speaker terminals are not smashed mosquitoes! They show which way the current must flow in order to push or pull the cone It is important that both speakers are connected to the proper terminals to insure that both cones push or pull together instead of trying to cancel each other.
