“In the 1950s, the term high fidelity began to be used by audio manufacturers as a term to describe records and equipment which were intended to provide faithful sound reproduction.”
faithful – true to the facts, to a standard, or to an original.
At Musicar, we believe that music is more enjoyable when it sounds real. Every note that sounds wrong, every note that’s missing, every time we hear an electronic distortion that should’t be there – those things take away from our enjoyment of the music. But reproducing the sounds played is only part of it – we also want you to hear the potential of the stereo information in the recordings that you’ve already paid for.
Some of this is the gear you buy, but a lot of it is how that gear is installed. Expensive gear can’t cure poor system design or improper installation.
You don’t need to read this page. – it has a lot of technical information which answers some questions we are regularly asked. It’s intended to be accessible to a larger audience (there’s no math involved). If you’re interested in learning more at a technical level, we are happy to recommend various books on the subject. Please feel free to email us with questions.
OK, here’s Ken’s 25-year-old “30-Second Speaker Explanation TM“:
Our eardrums detect air pressure, and we interpret air-pressure changes as sound. Our ear/brain system hears sounds roughly between 20 air-pressure changes per second and 20,000. (“Changes per second” isn’t an acoustic term – it’s “cycles per second”, or “cycles”, or “frequency”, or “Hertz”. We will use “cycles” as a shorthand term.) 20 cycles is the lowest note you’ll ever hear – and lower than almost any musical instrument can play. 20,000 cycles is really a higher note than we can hear – it’s dog-whistle territory – but it’s a nice round number. FM radio can only play sounds from about 50 cycles to 15,000, while CDs can play from 20 to 20,000. Compressed files, such as MP3 and its variants, have differing degrees of frequency response.
A speaker’s job is to push on air, which then pushes on our eardrums and creates sound. Here’s how that happens.
The part of a speaker we see most often is the cone. The cone can be thought of as as resembling a paper plate. (Some speaker use domes rather than cones, but it doesn’t matter – technically, it’s called a diaphragm.) The cone is what moves back and forth and pushes on the air, which then pushes on our eardrums.
(A thin speaker seen in cross-section)
On the back of the speaker, there is a tube. It’s glued to the cone. Think of a paper-towel roll after the towels are all gone – that’s a good example. The tube is like a handle for the paper plate – if you push or pull on the tube, you move the cone. You can see the tube in this cutaway picture.
On the back of the speaker, there’s a magnet. These magnets look like discs, but they are really doughnut-shaped, with a hole in the center. The magnet is a permanent magnet, so there’s always a magnetic field inside the doughnut hole. When the speaker is assembled, the tube is inside the doughnut hole. You can see how the tube is inside a circular hole in the magnet in the picture.
There is also a coil of wire. It’s glued to the outside of a tube in a spiral (also visible in the picture, at one end of the tube). One end is connected to the speaker’s (+) terminal, and the other end is connected to the speaker’s (-) terminal. This coil is an electromagnet, and it is called the “voice coil”.
So, if we send positive electricity down this wire, we create a positive magnetic field around the tube. Well, there’s already a permanent positive magnetic field in the doughnut hole, and thanks to our childhood experiments with refrigerator magnets, we already know that like magnetic fields repel. That’s what happens in a speaker – since the tube gets shoved away from the magnet, the cone is also pushed outwards. If we send negative electricity through the wire, we create a negative magnetic field around the tube – we know opposite magnetic fields attract, and the cone gets pulled inward, toward the magnet.
Well, what happens if we send this speaker a signal that changes from positive, to negative, and back again – let’s say, 42 times a second? The speaker moves in and out 42 times a second, and we hear the lowest note that any bass guitar can play. Now you know more than everyone at Best Buy.
More useful information about speakers
– Speakers don’t have “watts” – speakers are sent electrical power, which is measured in watts. The “power rating” of the speaker refers to how much electrical power the voice-coil wire can handle without melting (at least that’s what it’s supposed to mean – ask any electrical engineer). Unfortunately, the power-handling capability of that voice-coil wire has nothing to do with how good the speaker sounds, or even how loud it plays.
– As a speaker plays higher and higher notes, the sound is emitted in a narrower and narrower beam (like the beam of a flashlight). This “beaming” is much more important in car audio than in home audio (where we can usually control the speaker’s orientation). This physics phenomenon is directly related to the diameter of the speaker, and it affects all speakers. It causes the upper midrange from a 6.5″ speaker to be attenuated off-axis, and it causes the upper treble from a 1-inch tweeter to also be attenuated off-axis. This is one reason that the same speaker can sound different in different cars, and why speakers always sound different in display boards than they do in cars. At Musicar, we take into account the factory speaker position and orientation when we make our speaker recommendations, so that you don’t miss any of your music.
– Small differences don’t matter much in the upper treble, and small differences matter a lot more in the lower bass. Octaves are a pretty useful way to think of how we hear musical notes. An octave represents a range of sounds between a note n and another note 2n. If n is 500 cycles, then 2n is 1000 cycles, and the range in between is an octave. If you want to play notes one octave below 100 cycles, you need to play down to 50 cycles. Why is this important? The difference to our ears between 40 and 80 cycles is about the same as the difference to our ears between 8000 and 16,000 cycles.
– When a given speaker needs to play one note at a given loudness, and then it needs to play a note one octave lower at the same loudness, the speaker must move four times as much air. Since the speaker cone can’t get any bigger, the only way for that speaker to move more air is for the cone to move farther – it must move four times as far. This is why speaker types get bigger as they are designed to play lower notes – because mechanical excursion can only do so much, and beyond that point we need more cone area to move more air. There are not absolute rules for speaker size and capability – pro audio speakers used in sound reinforcement look and work very differently from speakers made for other applications, for example – but there are some broad classes of speakers which you’ve probably heard of.
— Woofers play bass. Technically, the bass region is all notes 300 cycles and below. Sub-woofers play just the lowest bass – technically, sub-bass is 50 cycle notes and below, but the term gets misused a lot. To create air-pressure changes at these notes which we can hear, woofers need to be larger, move farther, or both.
— Tweeters play treble. The treble region is the range of all notes from 3000 cycles up. Tweeters can do their job with small diaphragms – they actually can’t be too big and heavy or they will never move back and forth at 18,000 cycles per second!
— Midranges (which in Japan used to be called “honkers”) play midrange – technically the region from 300 cycles to 3,000. This region is the one that humans are most sensitive to – we are best at hearing voices – and it’s butchered by many audio systems.
A two-way speaker system has a woofer and a tweeter. A three-way system has a woofer and a midrange and a tweeter. You may have guessed that a four-way system has a subwoofer, a mid-woofer, a midrange, and a tweeter. For cars, two-way systems can sound great – but they are limited in their bass response. Three-way systems are the most popular and can sound really very good. Four-way systems are the most complex, and can yield the best results when properly executed. At Musicar, we do excellent-sounding two-way, three-way, and four-way systems.
– A “crossover” is another name for a filter. A crossover filter attenuates the notes which we don’t want a speaker to play at full volume – usually because we have another speaker playing those notes and doing a better job. If we have a tweeter in the car, and we let it play bass notes at any audible volume, it will distort quite a bit as it tries to play those bass notes. To keep the sound clean, we need to keep each speaker doing what it does well, and that’s what crossover filters do. Good crossover filters are complex, and factory audio systems use very rudimentary and low-performance crossovers.
— “Crossover frequency” means the point at which one speaker starts getting quieter and the other speaker takes over. If you draw this out on a graph, you can see where the term “crossover” comes from – the lines representing the output of each speaker cross over each other.
—- High-pass crossovers attenuate low notes and let high notes pass. Low-pass crossovers attenuate high notes. Band-pass crossovers are made from a high-pass and a low-pass crossover together.
There are two kinds of crossover filters:
— Passive crossovers go in between the speaker and the amplifier. They attenuate the notes they need to, and they can sound great in so doing, but the best passive crossover filters also soak up a lot of the power on the way to the speaker, and can’t be used with low-power amplifiers because there isn’t enough power left over to power the speaker properly. These are sometimes called “speaker-level” crossovers.
— Active crossovers filter the notes before they get to the amplifier. Active filters can sound better than passive filters, but the more active crossover filters you have in a system design, the more amplifier channels you need, and the more complex the wiring and the tuning become – so the price of the overall system increases. These are sometimes called “electronic” crossovers.
A good-sounding speaker system will at least be a two-way speaker setup with a crossover filter for those speakers. Three-way speaker systems can sound better, and four-way systems have the most potential for great sound. Good systems often use active filters for lower crossover points, and passive filters for higher crossover points (where lower-value components with fewer acoustic side effects can be used).
How does Musicar maximize speaker performance?
Speakers have been installed into cars for decades – but usually pretty poorly. Cars are not designed to be listening rooms, and car interiors are not designed to be speaker enclosures. We still need the speakers to “push” on the air in the cabin, and we need that pressure to be delivered to our ears. It turns out that you can get a lot more out of any speaker when some basic practices are followed during its installation. At Musicar Northwest, we install every speaker in a manner which lets it sound its best. Our research shows that (despite what gear manufacturers might imply) we get you better results by spending less of the budget on gear, and spending more time and attention on the way we mount the speakers into your car so that they perform optimally. Some of the techniques we use:
– Door-mount reinforcement
– Door-panel noise control
– Musicar’s precisely-made mating-spacer rings
– Gaskets and seals
– Best-practice quality control
– Door-panel reinforcement: Most factory speakers now have thick frames intended to add stiffness to the door they attach to.
Most aftermarket speakers have thin frames to help them fit into tight spaces, and aren’t intended to act as structural reinforcement. Musicar reinforces doors two ways – with our precision mating-spacer rings, and with constrained-layer damping tiles. The rings are stiffer than the stock speaker, so bolting them to the door reinforces the structure to a higher degree than stock. The aluminum-backed “Musidamp” constrained-layer tiles “float” a layer of aluminum on top of the door itself, making it stiffer and less likely to flex or vibrate.
– Door-panel noise control: Many install shops “control noise’ by slathering on layer after layer of damping material. The way this is often done, access holes are covered, factory bolt heads are no longer accessible, and the entire window – window track, window motor, window glass, wiring harness – becomes nearly impossible for a mechanic to service. At Musicar, we use the right materials in the most effective way. That means “Musidamp” constrained-layer damping tiles in a 20% coverage to reduce vibration and flex, closed-cell foam to reduce sound, and in some cases mass-loaded vinyl sheet to block sound even more effectively.
– Musicar precision-made mating-spacer rings: Factory speakers nowadays have a spacer built into them. This spacer serves two functions – it keeps the magnet from interfering with the window mechanism, and it seals against the back of the door panel. This latter function is rarely replicated in aftermarket installation, but it’s an essential part of playing accurate and immediate bass notes. A speaker needs a “baffle” – a panel to seal the front of the speaker off from the air behind the speaker. If there isn’t a baffle performing this function, much of the amplifier energy – and the speaker cone’s motion – is wasted. The car door fits in such a way that when the stock speaker’s cone moves forward, all the air in front of it is pushed right out the stock grille opening. A basic off-the-shelf thin plastic speaker ring won’t have the same results. Musicar duplicates this stock function so that you can have immediacy and impact from your front speakers.
An average speaker installation with a spacer just thick enough for the magnet to clear (note the lost sound pressure within the door):
A Musicar speaker installation (note how all the sound pressure created couples directly with the cabin air volume):
– Gaskets and seals: The precision spacers mentioned above require gaskets and foam seals to work properly. The factory speakers, which are usually of horribly low quality, always use these gaskets to sound their best – so we make sure your new high-performance speakers do as well.
– Best-practice quality control: Every audio system is listened to by two people prior to delivery. The settings are verified electronically and the result is measured acoustically, using state-of-the-art gear most shops don’t even have on hand. We offer free testing and re-verification of system performance as long as you own the vehicle.
“Stereos” in Greek means “solid”, and refers to what good old two-channel stereo sound was invented to do – create a solid illusion that’s so convincing, you can hear the individual musicians as if they were arrayed across a stage in front of you. Stereo for the home needs two speakers, and the stereo illusion happens in front of you (no rear speakers are required).
Stereo doesn’t work as well, if you sit on the couch in the wrong spot. This is for two reasons – sound travels relatively slowly (so the sounds from the different speakers arrive “out of sync”) and closer speakers sound louder and drown out the farther speaker.
Few people have heard stereo implemented well in a car, and there are several reasons why:
– The speakers are different distances from the listener (remember, sound travels relatively slowly):
– The various speaker drivers – the tweeters, the woofers, and the midrange speakers – are not all in the same location, the way they are in home speakers
– If a subwoofer is present, it’s farther away than the front speakers, and the sound arrives “out of sync”:
Despite those obstacles, realizing more of stereo’s potential is always Musicar’s goal.
“Don’t we want ‘surround sound’ nowadays?” Well, several multi-channel technologies have tried to displace stereo sound, but they have all failed – 99% of all commercial music recordings still come in stereo. Most multi-channel technologies we know today – Dolby Digital, DTS, etc. – are for movies, not music. Some genres don’t take full advantage of stereo’s capabilities – some popular music today is really meant to be heard in clubs with speakers everywhere, and even producer Phil Spektor’s old “Wall of Sound” approach didn’t use stereo as it was meant to be used. For most recordings, though, the goal is to recreate the concert experience – you, looking at a stage, with musicians performing on that stage. We don’t need “surround” for that – we’re not standing on the stage, it’s in front of us. Although many modern cars have center-channel speakers and rear effects speakers, this is not to make stereo sound better – it’s often part of a plan to sell more speakers to carmakers, actually.
What do we need to do stereo right? We need two sources of localizable sound in front of us, one on the left and the other on the right. Humans don’t hear the location of low bass notes well, so a well-designed subwoofer can go wherever it fits as long as the front speakers play convincing midbass. We need to set up the system so that the stage seems to be out over the hood, in front of the windshield.
This is why Musicar Certified Sound systems use a pair of front midranges and tweeters. Many also use a subwoofer. As far as rear speakers and center speakers, they aren’t essential parts of great sound, and we typically delete the center and leave the rear speakers stock – spending your money on rear speakers gives a poor return on investment, since humans hear detail from behind very poorly.
Since we’re in a car, our physical relationship to the speakers – the relative distances and the speaker’s orientations – are not optimized. Without significant modifications to the car, huge compromises are involved – some speakers are too close, some are too far away, some are aimed right at us and others are aimed away from us. Some folks want to modify the car to compensate for these flaws, and those projects are fun to execute – but we know that most folks want their vehicle to look and function just as it already does – they just want good sound. Using digital signal processing equipment from a few different suppliers, Musicar is capable of compensating for differing speaker distances and orientations, getting startlingly realistic and musical results without changing the appearance of the vehicle. This compensation happens in both the time and amplitude domains – we are actually making up for the different arrival times as well as the different apparent loudnesses of each speaker! We can also compensate for the acoustic response of the cabin, so that the music is balanced and present at all notes, without undue attenuation or emphasis.
Musicar also uses DSP processing to correct for the acoustics of the cabin. We can make up for the differing distances, the odd cabin surfaces, and the varying speaker sizes, using technology unheard-of for the car just ten years ago. Ask us about our DSP-based systems – available using factory head units or aftermarket head units.
The Musicar goal:
What sounds right
We have years of experience at system design and execution. We know where to spend time and effort to get good sound, and where it yields less return.
We deliver a wide range of sound, without holes in it (missing sounds in the middle are more objectionable than a limited range of sounds that’s smooth within that range).
We deliver a good stereo image. We give you the best midrange possible – for clear vocals, strings, horns, and piano – and the most accurate and musical bass notes possible.
We keep the car looking the way it should, and we keep everything working the way it should.
For a good two-way system, this is going to take:
– Two tweeters
– Two woofers
– One amplifier
– Either a good in-dash receiver, or a good factory integration
– Musicar integration and tuning
We also regularly do three-way systems, which include a subwoofer. We do four-way systems for those customers demanding the highest in performance. We do full digital systems using digital media players, noise-free Toslink S/PDIF lines, and trunk-mounted D/A processors as well.
The audio world is full of “specs” – signal-to-noise, channel separation, harmonic distortion, intermodulation distortion, dynamic range, dynamic headroom, power handling, impedance, sensitivity – we know which specification numbers make a big difference and which ones don’t (and which ones are just made up). We also promise to deliver – our Musicar Performance Guarantee is unparalleled in this industry.
We hope you’ve enjoyed reading about audio theory and about some of our techniques and approaches. Please contact us and ask what we recommend for your car!