Archive for August, 2009

Getting Hold of Car Insurance For Young Female Drivers

Did you know that young females are far less likely to have a serious car accident then their male counterparts? It is a reality that young woman drivers have fewer accidents in traffic than young men do. Why is this? Well, men tend to take a lot more chances in traffic, drive faster, and generally uses the car a lot more than most woman do. This fact give woman drivers an advantage when it comes to insuring their cars.

Because the accidents woman are involved in are usually less serious and more likely to happen while in low speed (for example: broken bumpers and car lamps), it is less risky for the car insurance companies to take on female drivers at lower rates.

What you should look for are car insurance companies that distinguish between male and female drivers, and search the web for low insurance rates for woman, this will give you a lot to pick from. There should really be no problem finding many good solutions.

Another good tip I can give you is to do a search for female car insurance reviews, comparisons, and user experiences in Google or any other search engine, as well as checking out yahoo answers and forums. This can save you lots of money, as you get to hear what experiences other people have had with the various companies.

It is easy to understand that it is more risky for the car insurance companies to take on inexperienced younger drivers, than more experienced ones, but there are opportunities to save quite a bit of money if you do a little research on the wold wide web.

I really hope this article has helped you a lot, follow follow these simple tips, and I am sure you’ll be able to find a few great deals.

Used Outboard Motors – Their Care and Maintenance

Used or new outboard motors need no require regular care after every use. Outboard motors are not like car engines in the sense that they are going to need more maintenance than just every 3000 miles. Outboard motors have to deal with a lot more environmental elements than a regular car engine. Point of fact, car engines don’t have to deal with salt deposits left from salt water use. Now do they have to worry about constant water intrusions that outboard motors deal with during every use. So, it is no wonder that outboard motors will require maintenance after every use.

Actions that need to take place after every trip with a Outboard motor:

1. Flush the engine – This does not apply to just salt water outings, fresh water can do just as much damage as salt water.

* Buy a pair of rabbit ears. This is a flexible rubber seal connected to a metal clamp. This unit is help flush the engine. connect the unit on the lower part of the motor were the water is picked up. Connect a water hose to the back of the rabbit ears.

2. Start the engine and let the water pump to its work. The water pump will pull in the clean water and wash away any left over salt or sentiment that might have built up during your adventure.

3. While flushing the motor check the water pump to see if your getting a good water flow. Carefully, put your hand in the stream of water. If the water is not pumping hard then you may have a block again the outflow tube. If so stop the engine immediately and clear the debris. You can do this by sticking a small wire into the flow tube and working it back and forth. After you think the tube is cleared re-start the engine and check the flow again.

4. Once the flushing of the engine is complete discount the gas line and allow the engine to run off the excess fuel in the . After excess fuel is burnt off put the fuel line back in place.

5. Next check for old and water leaks. This is done by taking the cowling off. If you find a link consult a boating mechanic to have the issue fixed.

6. Once you have cleaned and checked everything it is time to wipe everything down and spray with a anti-corrosive like WD40 or Quick-lube.

7. Replace the cowling and place a plastic cover on the engine to prevent anything from getting in on your engine.

Freight Value Increase 37%

Increases to trade and consumer activity are welcome news for the recovering economy as well as for consumer based industries such as trucking. According to the Bureau of Transportation Statistics (BTS) of the US Department of Transportation, trading between Canada, the US, and Mexico that used surface transportation had a 37.0% increase from March 2009 to March 2010. This significant $69.9 billion increase in trade has a much needed positive influence towards a struggling economy.

This year by year increase is the largest recorded to date, however, freight values still continue to struggle. Freight values continue to measure 1.2% less this March than 2 years ago illustrating the distance the economy needs to travel for complete recovery. Still, with consumer activity increasing, trucking companies can breathe a little easier.

This pattern of increase can be seen from a month to month basis in addition to the yearly statistics. According to trucknews.com, trade between the US and Canada increased 17.6% from February to March this year alone. While the overall freight value is not comparable to the rate in 2008, there has been some increase over the last year to the value of cargo. In this most recent year there has been a 19.4% increase to freight value, a welcome change, but not enough to offset the decreased value seen in preceding years.

All these increases in surface trading predict positive changes in the trucking industry and economy in general. More trade means more hauling for truckers. More hauling will signal a need for increased maintenance and a greater emphasis on the safety of equipment and rigs.

Auto Body Collision Repair – Find the Right Shop

Nobody hopes to get into a car accident. Its not on someone’s “to do” list at the beginning of their week. Nevertheless, it does happen and when it does you want to be able to get your vehicle repaired to its original condition in a timely manner. Finding the right auto body repair shop will ensure just that.

Here are some things to look for when you are selecting a collision repair facility:

1) Do They Have the Latest Tools

The cars of today have a lot of computer components in them. They are also more advanced and new to be diagnosed properly before work can even be started on them. Smaller auto body repair shops may not be able to afford all the expensive machinery needed to work on some of the newer vehicles. Make sure they are prepared.

2) What Does Their Repair Shop Look Like

Take a look at their auto body repair shop and make a mental note about what you see. Are employees wearing uniforms. Do you see a different variety of tools for different applications. Is it neat and orderly? You want to do business with a professional auto body company that is organized and a filthy shop with parts and tools all over place does not say that.

3) Do They Handle the Little Things

I would ask if they deal with the insurance companies for you and take care of things like getting your car towed and obtaining a rental car. Again, the bigger auto body shops usually have a customer service department that handles this “minor” details while the smaller auto body collision repair shops will not. You will be on your own and I can tell you, from firsthand experience, that an accident is already stressful enough.

4) What is their Current Parts Ordering System

If they cannot get the parts they need in a timely fashion your vehicle will just be sitting in their shop waiting. I have seen cars just sitting for weeks a because an auto body technician could not get the proper part he needed. Having a wide network of quality OEM parts suppliers is important and can be the X factor on how long your vehicle takes to get fixed.

5) Get Tons of Reviews

First, ask your friends family, and co-worker who they have gone with. This is an excellent place to start. They will not recommend someone who was not good to them.

Second, there exist a lot of online local review sites where people can post comments about their opinions and experiences about businesses they have done business with. The major search engines each have their own review places where you can look as well.

By following these five easy steps and asking a lot of questions you will be able to find a good and dependable local auto body repair shop. The whole accident process is stressful and hopefully the phase where you need to get your vehicle repaired will not be one of them.

Motorcycling – It’s A Tough Sport!

The sound of motorcycles thundering down the highway is once again being heard across the fields and roadways this spring. The image is most welcomed by the free spirit in all of us as the days turn long and temperatures increase. Before we wheel out on the roads for that first ‘putt’ let’s take a moment to remind ourselves of the simplest precautions we need to take for our own safety and for our passengers too.

Motorcycle fatalities are anticipated to be down by at least ten per cent ( 10 %) for the year 2009 by the Governors Highway Safety Association (GHSA). Hopefully this is the beginning of a much longer trend. The riders & their passengers need all the personal protection they can live with and still enjoy their passion, riding. You still should have protection between yourself and the road.

As most motorcyclists are only too aware the statistics bear out their vulnerability to the passenger vehicles on the roads. Approximately three-fourths of these motorcycle accidents involved collision with another vehicle, which was most usually a passenger automobile. In the multiple vehicle accidents, the driver of the other vehicle violated the motorcycle right-of-way and caused the accident in two-thirds of those accidents.* So the old one liner that, ‘ I had the right of way’ being placed on your headstone has justification.

Approximately one-fourth of these motorcycle accidents were single vehicle accidents involving the motorcycle colliding with the roadway or some fixed object in the environment. Most motorcycle accidents involve a short trip associated with shopping, errands, friends, entertainment or recreation, and the accident is likely to happen in a very short time close to the trip origin.*

Lack of attention to the driving task is a common factor for the motorcyclist in an accident.*
Almost half of the fatal accidents show alcohol involvement.* Don’t Drink & Ride! Leave your buzz until the days riding is finished!

The likelihood of injury is extremely high in these motorcycle accidents-98% of the multiple vehicle collisions and 96% of the single vehicle accidents resulted in some kind of injury to the motorcycle rider; 45% resulted in more than a minor injury.

The use of heavy boots, jacket, gloves, etc., is effective in preventing or reducing abrasions and lacerations, which are frequent but rarely severe injuries.*

The most deadly injuries to the accident victims were injuries to the chest and head.* So take caution while operating your two wheeled vehicle, or any vehicle for that matter and have an enjoyable safe ride!

Custom Wheels and Tires and Chrome Rims To Make Your Car or Motorcycle Stand Out

There are a lot of different choices on how you are going to customize your car or truck. Many of these choices are going to show it off at first sight, others will be more subtle. As a group, however, all of these customizations will make your car unique and will help it to stand out in a crowd. One of the first things that you should do for your car is to mount some custom wheels and tires. There isn’t anything else that you can do to your car that will make it stand out more that a great set of rims. The only thing that you will have to do is to choose a set that goes along with anything else you want to do to the car.

The choices of wheels and tires are almost endless, and some people take weeks or even months to decide on the ones that will be on their car. You have to choose everything from style to finish, and even then you will have many to choose from. I find that it is always best to break the choices down into smaller groups. In this way you are eliminating having to sort through any that you wouldn’t put on your car anyway.

Once you pick out the perfect set of wheels and tires, you are going to have to take care of them. Not only will they need cleaned on a regular basis, but if you are going to be doing any more custom work to your car then you need to protect your custom wheels and tires from harm. Make sure that you keep them covered and dry as much as possible and they will last for the life of your car, if not longer.

Don’t be overwhelmed by all of the choices for custom wheels and tires. Just take your time and look through all of the options. By doing this, you will end up with the set that is perfectly matched for you and your ride. It will be the start to a great custom car that in uniquely your own.

How to Make Sure Your Vehicle’s Transmission Remains in Good Condition

Your car’s transmission should last for over 100,000 miles. It’s not uncommon for this assembly to last much longer – often, twice as long. Unfortunately, many drivers unwittingly shorten the life of their transmissions by allowing them to slowly fall into disrepair. Unless you’re actively checking for problems, you’re unlikely to detect them. Eventually, your tranny will begin to experience difficulty changing gears, or finding the right ones. This is the gradual descent toward the assembly’s failure.

Replacing your transmission can cost up to $3,500, depending on the make and model of your car, and whether you purchase a high-quality rebuilt assembly. Even a used replacement can cost up to $2,000. For this reason, invest the time to periodically check for problems. When they form, have them fixed.

In this article, we’ll provide a few helpful tips for making sure your vehicle’s transmission stays in topnotch condition. If you do nothing more than the following, you’ll prolong the assembly’s life and postpone expensive repair bills.

Check For Indications Of Fluid Leakage

The transmission is a closed system. Hence, the fluid level should remain constant. However, the seals can deteriorate and the gaskets can lose their integrity over time. When either occurs, leaks can form.

The problem with leaks is that your transmission depends on fluid for lubrication of its moving parts and heat transfer away from the assembly. If the level declines too far, the moving parts in your tranny will create excess friction. This leads to internal damage, which is expensive to repair. Make a point of checking the ground underneath the assembly for signs of fluid leaks. If you notice a few drops, replenish the level and have a mechanic find and fix the source of the leak.

Look For Signs Of Declining Quality In The Fluid

Transmission fluid begins to degrade from constant circulation over tens of thousands of miles. This is the reason it needs to be changed periodically. You should also check its condition on a regular basis to ensure it doesn’t degrade prematurely.

Start your engine and let it idle for a few minutes. Then, pull out the dipstick and inspect the fluid’s color and consistency. If it is in good condition, the fluid will have a clear reddish tint to it. It will also appear thick, but slightly runny, and be devoid of metal filings. If it smells as if it is burning, or appears dark or opaque, it needs to be changed.

Note Any Changes In The Assembly’s Behavior

While driving, you should barely notice your transmission shifting gears. The process should be smooth and seamless. There should be no hesitation while the assembly searches for the right gears to engage. Nor should there be any lurching or hard shifting when the gears change.

Pay attention to these, and other, strange behaviors, including whining, whirring, or vibrating near the pedals. Each is a sign that something is wrong with your tranny, and needs to be resolved. If you have the problem addressed soon enough, your mechanic may be able to fix it without completely dismantling the assembly.

Change The Fluid Periodically

From the above discussion, it’s obvious the level and condition of the fluid in your transmission is critical to the life of the assembly. As noted earlier, it needs to be changed periodically. Look in your owner’s manual for the automaker’s recommended service interval. It can range from 20,000 to 60,000 miles, though most auto technicians will suggest having it drained and replaced every 30,000 miles.

This is a job you can easily perform on your own with a few tools. While it takes time and effort (along with a bit of patience), changing the fluid will prolong your tranny’s life and improve its performance.

Making Model Trucks That Have Working Parts

No matter what sort of model trucks that you like to collect you will find that it can be fun and very interesting as well. Die cast ones that come pre-assembled can be fun but the plastic ones that you can build yourself can make a great hobby. It will be a hobby that you will be able to share with your children and your family as well. Another benefit comes in when you find out that you are able to stand back and admire the work that you have put into the model that you have been able to modify yourself.

A way to really add a great deal of detail to your model truck is to make working parts for it. You can created many different parts that work including headlights and tail lights that work all the way down to working doors, hoods, and tailgates. This can help to dress up a tuck so that it is much more interesting. One of the things you will need to consider will be the scale of the truck with which you are working. Too small of a scale will limit you as to exactly which changes you might be able to initiate. There are some changes that will not make very good matches for your project.

If you will want to make an opening tailgate for your truck then you should be able to handle it rather easily. All you will have to do is to take a sharp bladed hobby knife and carefully detach your tail gate from the rest of the truck bed. Try not to remove too much material when you do this. You will have to consider exactly how you wish to reattach the tailgate once you have it cut loose. You may have to use a paper clip to make a small joint for the tailgate to pivot on. You will just have to straighten it out and snip part off. You can then run this part through the tailgate and into the sides of the bed.

This will give you a good looking and functional tailgate. You can also use this paper clip trick to be able to create some hinges for your doors if you choose to make them work as well. Once again you will need to make sure to cut them out slowly and carefully. Another thing you will have to consider is whether you will add any more changes such as adding a spare tire to your new truck bed for looks or by throwing some painted up spare parts from other cars in the bed to look like you are transporting parts.

Another change you can make quite easily is working head and tail lights. For these you will first need to make sure that your model truck has come with light covers that are not opaque. You will first have to remove some material from the body where the lights will be mounted. Next you will be able to run some doll house lights from to each of the head and tail lights. You can then run your wires to the battery in one of two ways. You can either run them down the undercarriage and attach the battery there or else you can install it in the bed of the truck.. This can look poorly so you might want to consider the former choice first.

Finding the Best Looking Car Audio Systems

For car audio fans this is still a question on their lips, should I go for looks over performance? Or performance over looks? Of course, this question is mainly for stereo and the amps, as subwoofers generally have a limited look; however, you can give your car audio system that pimped out look by looking at a variety of interesting systems with different forms and colours.

All car audio specialists agree performance is the utmost important aspect of a in-car music system; yet, looks are without a doubt one of the reasons why people buy a certain car stereo and accessories. After all, no one wants a system that is ugly, with unpractical oversized buttons and small barely visible letters. Not only is it unsightly to the eye, it is also impractical.

Although overall stereos have to be the same shape, alterations can be made through choice of colour, the aesthetics of the display screen and the layout of the buttons. The main frame of a stereo can generally be found in black or silver, with colour additions on the display screen or buttons – these are usually are red, green and blue.

Unlike stereos, amplifiers are not as limited in their aesthetics. Although, traditionally a flat rectangle, there is no reason why they cannot be made into interesting and unusual shapes. Already, the market has seen tubular and triangle amps added to car audio systems. With amps, you can pretty much have free reign over design; yet, manufactures still stick to the traditional rectangle metal style mainly due to its popularity.

Even though you could say ‘amps’ have been typecast, there are still diverse looking models on the market. Mcintosh with its compelling but ostentatious look gives the impression that the amp is screaming for and demanding attention. Brax, a German creation often provides that cold steel and accurate persona, with its devastatingly precise structure. No angle is rounded or wrong with this beautifully precise piece of engineering.

On the other hand you’ve got models that simply grab you attention, without being slick, smooth or ostentatious. The Blast BL-500, a model that gained my notice immediately, shows offs its curves and angles in a zesty lime green colour. Colourful and with definite but smooth angles, this model certainly looks the part in a car audio system. Edge, a company that relies on its eye catching looks, as well as extreme power, continues to prove the point that amps can still be beautiful with its tangy orange amp.

Car audio systems do not have to be unnecessarily ugly or even boring looking, as there are quite a number of models out there that will give your car audio system a unique and individual look. However, don’t sacrifice quality for looks as having a high quality should be a top priority.

An Introduction to Car Audio System Design, Stereo Imaging and Staging

Although many car audio enthusiasts already have a good understanding of how sound is produced, no technical manual should start without covering the basics of its subject matter. Writers sometimes wrongly assume that the reader will already know quite a lot about the subject and so they skip the basics. Because of this, some may find it difficult to understand the reasons for installing speakers in particular positions in the car, for example, or why a woofer operates best in a particular size and type of enclosure. Most people find it embarrassing to admit that they do not understand something which they assume everybody else knows. The truth is that there are probably several other people in the same group who would like to ask the same question.

Here I will outline the basics of the subject and briefly discuss how these basics apply to the world of car audio. It is not supposed to be a complete guide to sound because we don’t want to send you to sleep! If you would like to know more about sound and the principles of hi-fi sound reproduction, there are many good books on the subject.

So what is sound?

Sound is caused by the movement of air. If a large wooden panel is vibrating, the air next to it is pushed away. If the vibration is slow then the air just moves out of the way, but as the rate of vibration increases to between a few tens and a few tens of thousands of excursions per second, the air cannot move out of the way fast enough and therefore compresses as the panel pushes it away. The air’s natural elasticity comes into play. The particles of air against the panel are pushed against the next particles, which push against the next ones and so on, creating a ‘pressure wave’. As the panel returns to its starting position, the air becomes less dense as it fills the void in front of the panel.

The rate at which ‘pressure waves’ are produced is called the ‘frequency’ and is measured in ‘cycles per second’. Instead of ‘cycles per second’ we usually describe frequency in terms of Hertz (1 cps = 1 Hz). Imagine a bath full of water. If you put your hand in the water and move it slowly backwards and forwards, not much happens – the water simply slips around the sides of your hand. But if you move your hand very fast, the water doesn’t have time to move out of the way and you create a wave in the bath. Soon the water is flowing over the edges of the bath and soaking the carpet. If you used something larger than your hand to move the water, such as a dinner plate, you could cause the water to overflow without moving your hand as fast as before. Air reacts in much the same way. Big objects and small objects can generate pressure waves and therefore sound, but a small object must move quicker to cause the air in front of it (and behind it) to be compressed.

You are probably one step ahead of me by now, but this is why we find tiny tweeters and very large woofers. All sizes of speakers can produce sound, and the reasons why tweeters are small and woofers are big has much to do with the size of the pressure wave they are trying to reproduce and the weight and characteristics of the moving ‘panel’ – which in the case of a speaker is usually a cone, a dome or occasionally a flat diaphragm. To reproduce high frequencies, the cone or dome needs to move very fast. The smaller and lighter it is, the easier it is for the amplifier to control it. We’ll come back to this later. First we need to understand a little more about sound itself.

Pressure Waves

Pressure waves of a sound travel at a fixed speed of around 1100 feet per second (actually, air temperature affects the exact speed but we don’t need to worry too much about that). If we know the frequency (the number of waves per second), we can calculate the distance between corresponding points on successive waves – in other words, we can measure the length of a wave, or the ‘wavelength’. A sound that has a frequency of 1100Hz has a wavelength of one foot. A sound of 2200Hz will have a wavelength of six inches, and a sound with a frequency of 550Hz will have a wavelength of two feet.

The notes of the musical scale simply represent sounds at certain frequencies. Middle A on a piano is 440Hz for example (a wavelength of 2ft 6in). In the case of a church pipe organ or electronic synthesiser, it may be possible to play an A which is four octaves below middle A. This has a very low main or ‘fundamental’ frequency (additional frequencies or ‘harmonics’ will be added naturally, which gives each instrument its own individual tonal character) of 27.5Hz, a wavelength of around 40 feet! At literally the other end of the scale, an A played three octaves above middle A has a frequency of around 3500Hz and a wavelength of just 3.75 inches.

The size of the musical instrument (and loudspeaker) tends to suggest the size of the wavelength it’s designed to produce. The soundboard of a piano and the large pipes of a church organ are capable of producing large wavelengths, which means lower frequencies. Similarly, a 12-inch diameter subwoofer is designed to give low bass. If we ignore for a moment the mechanical limitations, there is nothing to stop a good 6 inch mid-woofer from reproducing very low frequencies. It can move at the required cycles per second, but its size means that it can only displace a certain amount of air during each cycle. It may produce very low frequencies, but only at very low output levels. This takes us back to the analogy of the hand and the dinner plate in the bath full of water. The surface area of a 12-inch subwoofer is like a dinner plate, able to move enough air in one cycle to produce a pressure wave capable of rattling the windows in the house across the road!

Imaging and Phase… creating the illusion of reality

When we install a hi-fi system in the home or in the car, we are attempting to reproduce a very complex pattern of sound waves within an environment that is quite different to the one in which the instruments and vocals were recorded. We are trying to recreate not only the sounds of the various instruments and singers accurately but also their positions on the ’sound stage’. This is often called ‘imaging’ or ’stage image’. It may also be described as ’staging’, but in car audio this word is generally used to describe the position of the stage itself (whether it appears to be in front of the listeners or behind them), rather than the position of the performers on the stage.

If we listened to and recorded the sound of a single flute in our living room, for example, and then replayed it via a single full-range speaker positioned in exactly the same place as the flautist, there is a good chance (if the recording equipment and hi-fi system is of a good enough quality) that it will sound more or less identical. The reverberation characteristics of the room will be the same and, since we are using only one speaker instead of trying to artificially recreate the position of the flautist in the room by using stereo techniques, the instrument should appear to be in exactly the right place.

If we had a complete orchestra in our living room and wanted to copy what we did with the single flute, we would need to use a multi-channel recorder, several channels of amplification and however many speakers it took, each arranged in exactly the right place for each instrument. Having witnessed this done at a hi-fi show in Paris some years ago, I can tell you that it can sound very realistic. The problem is that it is not currently feasible to do this in most homes, and certainly not in a car, which is why we have… yep, good old stereo.

Stereo aims to recreate the exact positions of the various instruments by using only a single pair of loudspeakers, and it achieves this mostly by increasing the level of a particular instrument in one of the channels relative to the other channel. Only the levels are different – the wavelengths from both the left and right channels will be identical in every other way. They are said to be ‘in phase’. This means that if you could somehow freeze the sound and see the wavelengths emanating from the two speakers, both wavelengths would be at the same point in their cycle.

When sound is recorded for stereo reproduction, it is assumed that the listener will be positioned equidistant between the two loudspeakers. Of course this is rarely the case in a car, unless you happen to drive a McLaren F1. We compensate for not being seated central to the loudspeakers by adjusting the balance control on the CD player, which increases the volume level on one side relative to the other. This only corrects the stereo image up to a point, because we are still physically closer to one speaker than the other, and adjusting the balance control has no effect over the phase and timing of the signal reaching our ears.

If we are sitting in the front of the car, close to the left-side speaker, then we will hear the sound from that speaker very slightly earlier than the sound from the speaker on the right, and from those speakers behind us. It is also likely that in the upper frequencies, where the wavelengths are very short, the sound we hear through our left and right ears may be slightly ‘out of phase’. These timing and phase distortions confuse the brain and can destroy the stereo effect. When this happens, you hear most of the sound is coming from the speaker closest to you, instead of from an imaginary stage across the windscreen – the stereo trick fails to work.

Our earlier analogy with water may also help us to understand what is meant by sound being ‘in phase’ and ‘out of phase’. Imagine that you start a gentle wave from one end of the bath. If you use both hands to start two waves at exactly the same time, the peaks of the waves will occur at exactly the same point and the waves could be said to be ‘in phase’. Now start a gentle wave from the other end of the bath. What happens when the two waves meet? Both waves clash and effectively cancel each other out. Now imagine speakers at the front and rear of a vehicle, each producing sound pressure waves. These mix and create some very complex alterations to the sound. As the pressure waves meet, the air may be pushed stronger in the same direction in which it was already travelling (so we get additions which can lead to peaks in the frequency response), or one pressure wave may compress against another travelling in the opposite direction. In the latter case, if the two waves are identical in terms of frequency and pressure and are exactly half a wavelength out of phase, they will cancel themselves out completely, leaving silence.

Usually the two sound patterns are so complex that they will only partially cancel, but relatively pure tones of long wavelengths and high pressure are more likely to noticeably cancel. The lower the frequencies being produced and the more loudspeakers there are reproducing that range of frequencies, the more likely it is that phase cancellation will occur. If speakers are wired with the + and – terminals reversed on one speaker, the speakers are placed 180 degrees (half a wavelength) ‘out of phase’. In theory they should cancel themselves out, but in practice the bass region suffers most cancellation and the remainder of the sound becomes confused, with little or no central image.

Speaker placement… for those without a McLaren F1

By installing many speakers inside a vehicle, we create a very complex mix of pressure waves which can cause problems with the overall sound. This does not necessarily mean that it is a bad thing to install a large number of speakers. We may want to split the frequency range into small portions – sub-bass, bass, mid-bass, midrange, upper midrange, high frequencies and ultra-high frequencies – so that each range has a pair of speakers dedicated to it. Because of the limitations of loudspeakers, this might be a good idea if we are looking for absolute sonic fidelity. Of course space in a vehicle is limited and so we tend to install fewer speakers, usually covering the sub-bass, mid-bass, midrange and upper frequencies. This can give good reproduction of the tonal qualities of the various instruments and voices but there are still the problems of phase, ‘time alignment’ and ‘off-axis’ performance to consider.

We should generally try to avoid reproducing the same frequencies from speakers positioned at different distances from the listeners. For example, if we have a pair of 6-inch speakers producing mid-bass at the front of the vehicle, we should avoid having another pair of speakers reproducing exactly the same range of frequencies from the rear shelf. The colliding pressure waves will cause additions and subtractions, according to the phase of each wave, at the point where they meet. Frequency peaks and troughs could be adjusted with a third-octave equaliser, and the timing of the sound from each speaker could be adjusted using a ‘time alignment’ digital signal processor, but there is no practical way of compensating for the phase distortions. It is much more sensible to avoid the problems from the start, as much as possible.

When deciding where to position speakers, especially midrange and tweeters, try to install them so that the left and right speakers of each matched pair are equidistant from the listeners. This is often very difficult to achieve of course, but do the best you can. The footwell positions often work well for midrange speakers and sometimes tweeters too. If you decide to mount the tweeters higher, try if possible to mount them in a position which is half the distance to the midrange speaker – there is some evidence to suggest that placing the mids and tweeters exactly 180 degrees apart can improve stereo imaging.

Larger bass speakers can often be installed in the doors without too much affect on imaging, if you make sure that the crossover point is set so that their output does not overlap the frequency range of the midrange speakers too much. The subwoofer, or subwoofers, usually have to be installed in the rear of the vehicle because of their size. Take care when choosing the slope and setting the crossover point on the channel(s) feeding these speakers. With a 6dB per octave ‘low-pass’ filter (a filter which only passes frequencies below a certain ‘crossover point’) set to 100Hz, the output at 200Hz will only be 6dB lower, and since subwoofers tend to be driven loud, the pressure waves created in the middle frequency region will probably be strong enough to interact with the speakers at the front of the vehicle. It is generally wise to choose a 12dB or 18dB slope for subwoofers.

Installing full-range speakers in the rear shelf, or in the rear doors, often confuses the stereo image at the front of the car because the same sounds are coming from more than one source and this is unnatural. If you need to install speakers here to provide ‘rear ambience’ or a ‘double front stage’ because you often carry passengers in the rear seats, adjust the front/rear fader control on the CD player so that the front speakers are considerably louder than the rear speakers when listening from the driver’s seat.

You may still find that the stereo imaging at the front of the car is confused. If this is the case, it is worth experimenting by reversing the +/- connections to all the full-range speakers at the rear, putting them 180 degrees ‘out of phase’ with those in the front. It may sound crazy but sometimes works well. Always ensure that you reverse the connections on both speakers in a pair.

In an ideal situation, all the sound at all the various frequencies should start out from exactly the same place. A speaker system which attempts to provide this is often described as a ’single point source’ because the various drive units are physically aligned so that, in theory at least, the sound will be ‘in phase’ and ‘time aligned’ across the entire frequency spectrum. What usually occurs in a vehicle, however, is that speakers are positioned some way apart and at different angles relative to the driver and passengers. A speaker that is pointed directly at the listener is said to be ‘on axis’, while a speaker installed low down in the door next to the driver is described as being ‘off-axis’. A speaker’s output characteristics alter when it is listened to ‘off axis’. Its frequency response is affected, and phase changes may also occur. It is important to know this and experiment, where possible, by altering the mounting angle of the speaker to achieve the best results.

Shake, Rattle and… Why materials resonate

One thing we want to avoid in a car audio system is any panels (such as the metal panels of the vehicle itself) that resonate, that is, vibrate because of the movement of air within the enclosed space of a car. It’s a bad thing because these panels will produce a sound of their own or, in the case of the walls of a bass enclosure, if they’re not rigid then we’ll lose some of the power and definition from the low frequencies.

Musical instruments which produce sound naturally (not electronically) do so by either causing something to resonate – such as guitar and piano strings or the skins and metallic surfaces of a drum kit etc. – or by directly moving the air, as in the case of wind and brass instruments. Every material has a particular ‘resonant frequency’ – this is the frequency at which the material will vibrate or resonate most freely – and this, together with the size of the resonating object and many other factors, contributes to the sound which an object will produce if it is sufficiently excited.

Of course something very dense and rigid like a brick is less likely to be made to resonate than a guitar string or a thin piece of wood. Brick is a much less efficient resonator than wood. Sometimes this can be useful, especially when building a bass enclosure where we need the sides to be very rigid and acoustically ‘dead’ so that it doesn’t resonate, since this would add some of its own sonic character (or ‘coloration’) to the bass sound we are trying to reproduce.

Unfortunately, brick-built bass cabinets in cars haven’t really caught on, and more practical alternatives had to be developed for making wooden enclosures and the metal parts of the car less resonant. Good quality particle board (MDF) is especially dense and provides a good starting point, and this can be treated, if necessary, with sound deadening sheet or a spray treatment. In the case of sound deadening sheet, this bonds an acoustically ‘dead’ material to the more easily excited panel, such as the vehicle’s metal inner side panel, door panel or inner boot (trunk). The sheet helps to absorb panel resonance because its own resonant frequency is very low, so the resonance occurs at a much lower frequency and becomes less noticeable. In the case of NoiseKiller, a spray treatment developed by Swedish company Audioform, the resonance absorbed by the material is not simply frequency shifted. Instead, it is transformed into a tiny amount of heat. The manufacturer claims that the material produces absolutely no sound of its own – in other words, the panel resonance is completely eliminated.