Car speakers


#1

My car speakers on my 1997 Ford Thunderbird are still the original speakers that came with car. I have changed the stereo twice so the current stereo is only four years old. I do not think that it sounds as good as it used to but I am not sure. I am thinking of new car speakers since it seems there are many affordable choices. I am wondering what differences I might notice if I change the four speakers out that are nineteen years old. Also what are some things that I should keep in mind when I look online at speaker sets?


#2

If you really want to improve the sound from the speakers, apply sound insulation to the cavities where they reside. Pull the interior panels, line the sheetmetal with a Dynomat-type insulator, overpay that with a blanket-type insulator, and add a blanket-type insulator between the cavities.

I’ve done this. The difference is dramatic.


#3

Almost any new speakers will be better than what you have now. The ones you have now are most likely at least 30% less effective than new due to heat and cold.


#4

Be aware that any new speakers you get will most likely not directly mount up to the holes the old speakers were screwed into. You will often want to cut a circle out of fiberboard to screw the speaker into, and then screw the fiberboard into the old mounting holes.

If you really want to improve the sound, look into getting a subwoofer. They make ones that tuck under the seat now, so you don’t have to have a big stupid speaker box taking up all of your trunk space. The biggest weakness with most car audio is lack of bass, which makes them sound tinny.

The second biggest weakness is improper speaker installation which causes the speakers to rattle against the door frame, which pretty much wrecks the sound.

Also keep in mind that many modern head units are designed to feed into an amplifier. The internal amplifier will work, but will not sound as good as if you amplify the signal properly. The good news there is that amps aren’t all that big, and if you are not one of those guys who likes to show off all their audio gear, they can be hidden away under the dash.

The final tip to keep in mind if you get an amp and a sub is that you need to wire the power leads properly. You need the power wire to be fused no more than 18 inches away from the battery, and before it goes near anything metal – I have seen people set their cars on fire due to skipping this step.


#5

Good post shadowfax. I might add that if you add a very powerful subwoofer and amplifiers, you may be getting into the realm of insufficient 12 volt power, requiring an upgraded alternator and battery. Or a super capacitor. But that is with a major upgrade. The place you purchase the equipment from can advise you there.


#6

Yep. Fortunately, that’s usually for the kids who want everyone else to hear what they’re listening to as well as to deafen themselves. A normal setup for grownups doesn’t require nearly that much power.


#7

Most aftermarket head units produce more power than most OEM speakers can handle. If the original stereo system was NOT one of the premium upgrades, the speakers may have been rated for 10 watts or less. Most aftermarket head units put out 20 or more watts even without an external amp. So chances are that the original speakers have been over driven, along with being in an environment that ages them quicker that the typical living room.

A car is a lousy listening environment at best, and best is when the engine is off and you are sitting in a quiet driveway. It only gets worse from there. As a car ages, it gets noisier so that may also be contributing as much to the sound deterioration as the aging speakers. This is why sound deadening is so important to good quality sound in a car.

You listen to the speakers, not the head unit, the amps or even the sound source. It is the speakers that produce the energy that you actually hear, so you should invest more in them than anything else. The speakers also are responsible for the most distortion of the original sound source and the most limitations on the frequency range. Better speakers have less impact on those things, but cost more.

But it seems that in the area of automotive speakers, money isn’t everything. You can buy very good speakers in the area of $100/pair, or pretty lousy speakers for $500/pair and up. It does not seem that many popular speakers sold for high prices are made by companies that produce speakers for audiophiles home systems.

If the company that produces the car speakers you are looking at does not produce high end audio speakers for homes and studios, I would not chose them. Infinity and Polk Audio are two brands that make speakers for both. Both also make speakers in the $100/pair range and up.

As for a sub woofer (aka sub). Most systems way overdrive the bass. Some of this extra volume is needed because the sub is located in the trunk where it is muffled before the sound gets into the passenger compartment. Subs in general have a higher efficiency than most speakers, so one watt to the sub produces more volume than one watt to the main speakers. A sub can produce over 100dB of sound per watt where a main speaker generally produces about 90dB. That means the sub is 10 times louder than the mains.

Many audio systems used in cars often have much more power dedicated to the sub than to the main channels. I’ve seen a 500 watt sub amp with a 300 watt main amp. The main amp is dividing the 300 watts to 4 channels so that is about 75 watts per channel. So now you have 500 watts to a bass that is at 100db/watt and only 75 watts to the main channels feeding speakers at 90dB/watt. Most of the music is in the main channel. Even with the sub in the trunk where it is muffled some, all you can hear is the bass.

So if you go with a sub, be careful not to over drive the other channels.


#8

I’d go to Crutchfield.com and see which speakers fit your car. I found dozens, and lots with 5 star ratings. No modifications needed. Looks like 5"x7" fit both front and rear, get a set of 4 matching speakers, I bet it will sound way better.

Speakers are more likely to get damaged by an under-power amp driven into clipping than a high-power amp.


#9

"Speakers are more likely to get damaged by an under-power amp driven into clipping than a high-power amp. "

Huh?


#10

Yep. The problem is usually a low-powered poor quality amp driven hard. That drives it into clipping, where the peaks of the wave forms are clipped off, creating more of a square wave. Square waves have huge high-frequency content, causing the speaker coil to blow. I’ve driven cheap, low-power-rated speakers with high power quality amps, with no problem. It’s the reverse that causes problems.

This applies to speakers with 2 or more drivers. The square wave’s high-frequency content can overload/burn out the tweeter, which usually isn’t designed to handle a lot of power.


#11

Speakers are pretty simple, comprised of a permanent magnet, and some magnet wire embedded in a paper membrane. The magnet usually remains magnetized ok. That’s not likely to be the problem. The problem is usually with the membrane, or the speaker mountings. Take a look at the existing speaker membranes. That’s the part usually made with a sort of pressed paper product that does the actual vibration which causes the sound. If they look cracked and brittle at all, water damaged, etc, good idea to replace the speakers. If the membranes check out ok, verify that the speakers are still mounted securely to their supports. If they are loose at all, that will affect the sound quality and can create buzzing sounds. Sometimes the speaker units are glued to the supports, and come unglued over time; a re-gluing them often fixes the sound quality.

When you switch out the stereo of course, everything depends on the sound quality capability of the replacement stereo. All bets are off if the stereo isn’t putting out good sound quality. Usually the problem folks run into when switching out the stereo isn’t the stereo is not good; instead they don’t get the correct impedance match between the stereo and the speakers. The stereo is usually rated for a certain speaker impedance, for cars usually 4 ohms. But it varies from stereo to stereo. So double check that. When you buy a boxed set, a stereo and the speakers from the same manufacturer, that’s one way to up your odds the stereo and speakers are impedance matched.


#12

@texases, that would be a very poor quality amp indeed. Even the lowest quality amps I’ve seen will limit the power out to 10%THD. That will sound crappy, but it wont damage the speaker. Most amps are limited to 1% THD or less.

The power rating of speakers is based on the highest power that they can handle continuously for a given temperature rise. You can use a higher powered amp as long as you don’t turn up the volume. Once you exceed the speakers rating, it will overheat and burn up.

Impedance matching is not the big deal it once was. Tube amplifiers were very sensitive to impedance matching but everything is solid state now and they have a lot more tolerance. Most automotive amps are 4 ohm as are most automotive speakers. Many home systems are 8 ohms. Many sub are 2 ohms.

BTW, impedance is not even across the speakers bandwidth. It varies with the frequency of the signal. The impedance rating is usually the average, or the impedance at 1000 Hz.


#13

keith: that is the distortion at max rated output. But if you crank the input higher, attempting to get more power, the distortion increases, it has to.


#14
"Speakers are more likely to get damaged by an under-power amp driven into clipping than a high-power amp. "

Huh?

@Texases is 100% correct. An amp that’s clipping can destroy tweeters.


#15

AND . . o.e. speakers are usually a different ohm rating that the a/m units. That ohm mis-match will result in a different sound quality.
Match speaker ohms to output.

I have two different o.e. speakers here now , one is 5.3 ohms and the other 6.6.


#16

Any good quality amp can handle different ohm speakers. There will be no difference in sound quality unless the amp can’t handle the ohm. Ohm rating is an AVERAGE over the speaker range. The speakers do not have a constant ohm over it’s entire frequency range.


#17

" @Texases is 100% correct. An amp that’s clipping can destroy tweeters. "

That statement by itself is true, but that is taken out of context. His whole post as written is incorrect. An underpowered amp is not going to hurt the speakers. The speakers are not causing the clipping. The clipping is caused when the input to the final stage of the amp drives the device (transistor or tube) into full conduction and/or full cutoff. At the full conduction end, odd ordered harmonics are formed.

If the input to the final is so high that it sends the final into full conduction immediately, the maximum amplitude of the third order harmonic will be 1/9th of the output. The 5th order harmonic will be 1/25th etc. This is the absolute worse case where the output forms a perfect square wave. These harmonics will be far far less in the real world.

What damages the speaker, tweeter, mid range, woofer or sub, it does not matter is heat and heat comes from power. A speaker designed to handle high power will be able to handle anything that comes from the low powered amp.

If you drive a high powered amp to clipping, then that can damage the tweeters in the speaker, but they will not be damaged by an amp that is below their capacity.

BTW, most subwoofer amps spend a great deal of their time at full conduction. They drive the final into clipping at all levels of sound input, but of course there aren’t any tweeters connected to the sub amp.

"keith: that is the distortion at max rated output. But if you crank the input higher, attempting to get more power, the distortion increases, it has to. "

Bill, I almost don’t know where to begin. The amplifier stage consists of two stages in most cases. The first stage takes the signal from the source and amplifies it a little. These is also where the volume control is as that amp is variable. It then is fed to the final amp, which in most cases today is a push/pull class AB amp, except for the sub. The first stage is designed to limit the maximum output to what the final can take. Making the first stage more powerful would be a waste of money.

Now if the source has a much higher input amplitude, then you would drive the first stage into clipping. Now the distortion occurs before the amplifier section. Some old audiophiles can remember the days of a high end component system when the only sources available were a receiver, tape deck and phonograph. The phonographs has such a low signal strength, that it was fed into a preamp first. Except for some extreme systems, the preamp was built into the input of the amp. If you accidently connected the tape deck to the phono input, you would get a painful audio experience, if the amp even survived.


#18
An underpowered amp is not going to hurt the speakers. The speakers are not causing the clipping. The clipping is caused when the input to the final stage of the amp drives the device (transistor or tube) into full conduction and/or full cutoff. At the full conduction end, odd ordered harmonics are formed.

He specifically said when driven into clipping. And you are more apt to drive an underpowered amp to clipping then you are an over powered amp.


#19

but they will not be damaged by an amp that is below their capacity.

Rated capacity goes out the window during clipping. The actual delivered output power is much higher under those conditions. But you’re right, if the speaker is designed to handle it, it will not be damaged. But most systems are sold as paired components with like ratings. That usually doesn’t translate to excessive margins in the load device. Good amps (ala more expensive) have circuits in them to protect against clipping where those conditions would exceed the rated outputs and potentially damage the loads. Cheap amps usually less expensive because they left something out :wink:


#20

This argument could go on forever.

The first stages of a typical AB amp see less voltage than the final as there is voltage gain in the first stages. The final stage can be CE or CC, with CE (common emitter) the most popular. In this case the final stage has voltage gain, so it can clip while the earlier stages are operating in linear mode. Of course the feedback modifies that, as it attempts to prevent the clipping, but is unable to; so all the stages show distortion. But the distortion/clipping is due to the final stage being overloaded, driven into saturation.

The CC type has no voltage gain in the final stage, so it’s the prior stage that clips. But the end result is the same.

I think we are saying the same thing in different words. If you arbitrarily increase the input signal level to an amplifier, at some point it distorts badly, ie, it clips. The power rating of the amplifier is written for smaller input signals, and the amp is designed to operate at those lower input levels.