Tag: car subwoofer

Damping Factor

The Damping Factor of Your Amplifier Tells You How Well it Controls The Movement of Your Speakers

When you look at an amplifier’s specifications you may come across one that says “Damping Factor”. The damping factor describes the ability of the amplifier to control the movement of a speaker, more specifically, unwanted movement. This is especially important for lower frequency speakers such as car subwoofers.  Damping factor can be looked at from many different angles and several factors affect the overall damping factor in a system.

In a simple sense, the damping factor tells you how well an amplifier can control a speaker system. The larger the number associated with damping factor the better an amplifier is at controlling speakers. Anything above 100 tends to be very good while below 30 is poor. Most aftermarket car audio amplifiers to date won’t have such poor damping factor specifications to the point where it would become a concern for the average listener if they follow specs. This means that if you’re trying to get the best sound possible you need to look for a higher damping factor, assuming everything else is equal.  Below I will get slightly more technical, so the above information is very simplified.

Most manufactures do not specify damping factor accurately in their specification charts. An accurate damping factor will look something like this: Damping Factor = 100 at 4 Ohms. Rarely is the impedance (ohms) listed. Damping factor is the speaker systems final impedance (load impedance) divided by the amplifiers output impedance. So if you have one speaker at a perfect 4 ohms impedance and divide it by the amplifiers output impedance, let’s say 0.4, you get a damping factor of 100 (4.0 / 0.04 = 100). If your final impedance is 1.0 ohms and the amplifiers output impedance is 0.04 your damping factor becomes 25 (1.0 / 0.04 = 25). Using this formula, as long as you know the amplifiers output impedance and your speaker systems final impedance, you can calculate the damping factor. This is why it is important for the manufacture to list what impedance they list their damping factor at for the most accurate number. However, using the formula you can find out if you have most of the other information.

Let’s throw a monkey wrench into the mix. In the real world, a speaker’s impedance is affected by everything in the system. A  car audio speaker will fluctuate anywhere from 1 ohm to even 30 or 40 ohms while it is operating. So if damping factor is based off of the speaker’s impedance but it’s always jumping up and down then that means the damping factor can’t be a single number. Damping factor is a major simplification of what is actually going on but it is still important! If everything is relatively equal you would be able to notice the difference between a damping factor of 100 and 25. While this should not be your go-to to find the best quality in an amplifier, if all the other specs are closely matched you can look at it to help make a final decision. Knowing all the specifications and what they mean can really help put everything into perspective when selecting an amplifier and speaker combination. Remember, it all comes down to what sounds best to YOUR ears.

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Competition Grade V.S. Standard Subwoofers

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So you want to step it up and bring your a-game to the competition? You wake up at night in a cold sweat having dreamt about the loudest or best sounding system in the world being yours. While there is nothing wrong with having grand dreams, what good does it do if you don’t bite the bullet and take the plunge? So what is the deference between a competition grade subwoofer and a normal subwoofer?

Competition grade is not a “real” classification. It generally refers to high output, high powered woofers that are pretty hefty in weight. There are no distinct guidelines and technically anything that can be used in a competition is competition grade. There are of course woofers that have been designed specifically for use in competition settings, like the HCCA Series and Solo-X woofers. These competition grade woofers have available recone kits that allow you to fix the woofer in case of damage, which is likely in competition settings. Even competition woofers can be used in your commuter car for every day listening. When it comes to competition or normal woofers, the box plays an extremely important role in the sound properties of the woofer. Follow that up with quality gauge wire and the correct amount of power.

Being that there is no classification, if you see a subwoofer with the title of “competition grade” it most likely follows these guidelines for SPL (Sound Pressure Level) competitions:

  • Subs with power handling at or above 1000W RMS
  • Subs with a voice coil larger than 2.5″
  • Subs with an Xmax excursion of 1”( 25.4mm) or more
  • Subs with spiders larger than 7″
  • Subs featuring composite cones or any very strong material

If you find a woofer with a large excursion and high power handling, it tends to fit into all of the other categories automatically. So to wrap it all up, does this mean you could technically get $25 subwoofers and enter in a competition? Yes it does, you most likely won’t succeed but you could do it. Should you try to buy “competition” grade equipment? It does not matter so long as it fits the two most important specifications (power handling and excursion) and you get a great box builder. Oh and one more thing, if your new to competition, go to a few events and talk to the pros before even considering building your system, there is a lot to it!

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What is the Difference Between 2 and 4 Ohms?

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Ohms are the measure of resistance to the flow of electricity in an electric circuit. Think of it like a freeway, the more cars congesting the freeway, the slower everyone will move due to traffic. Electricity, like the cars, can be slowed down in the circuit due to higher resistance.  The higher the ohm value, the more difficult it is for current to flow through a circuit. Likewise, the lower the value, the easier it is for current to flow. Based on this, is there any other differences between the most common 2 and 4 ohm impedances?

Certain amplifiers are designed to power subwoofers at different impedances (ohms). For example, a 2 ohm rated amplifier will power a 2 ohm subwoofer, so long as the woofers “final impedance (ohms)” is 2. You can connect multiple subwoofers together and run them off an amplifier, so long as their final impedance is equal to the amplifiers impedance. We cover this in a different article. If you have 100 watts at 2 ohms, and 100 watts at 4 ohms, is there a difference? The answer is subjective, you will hear people say there is a sound difference, and some say there isn’t. It depends on how efficient the amplifier runs at the specified ohm level, as well as the speaker itself.

If you get technical, the different resistance values of a speaker will change the sound slightly, assuming wattage is the same. A lower impedance subwoofer has a voice coil with fewer windings, meaning less weight. A higher impedance subwoofer will have more coil windings, meaning more weight. It has more windings to counter act the resistance, so it’s like adding more lanes to the freeway to ease up traffic. This slight difference in weight will produce a slight sound quality difference. At 2 ohms you tend to have more projection of sound (louder), which causes poorer sound quality. At 4 ohms you will have less mid bass frequencies then at 2 ohms; however the sound quality is slightly improved.

If you’re not an audiophile, does this matter? Honestly, no it does not. Do not let this be a make or break when looking for sound system components. Two of the same subwoofers, just with different impedances, will produce almost the same sound if they are run at the same wattage. The difference in sound is so slight that it has little impact, especially when dealing with subwoofers, that you likely can’t tell the difference.

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What are the Differences Between Single and Dual Voice Coil Subwoofers?

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You’re shopping for subwoofers and you see two identical looking woofers. You read the specifications on the label and notice they are the same for both car subwoofers. The price is slightly different and the model numbers are slightly different, but everything else is the same! But wait, you turn them over and one says “Single 4 Ohm” and the other says “Dual 4 Ohm”. This is no deception, your eyes don’t lie. Before you bag one up and take it home, do you know the difference between a Single and Dual voice coil subwoofer?

First of all, what is a voice coil? The voice coil in a subwoofer is a coil of wire wrapped around a cylinder called the former, which accepts the amplifiers current. Current from the amplifier causes the coil to react with the stationary magnet, moving the former up or down. The former is attached to the speaker cone which produces changes in air pressure when moved, producing sound.

A single voice coil (SCV) is one length of wire wrapped around the former. A dual voice coil (DVC) has 2 coils of wire wrapped around the former. A single voice coil subwoofer will have a positive and negative terminal, while a dual voice coil subwoofer will have 2 positive and 2 negative terminals, one for each coil. The price of a DVC subwoofer will usually be slightly higher than its SVC brethren due to the extra coil. There is no performance advantage between the two types of voice coils, so why bother?

The advantage of a DVC subwoofer over the SVC subwoofer is your available wiring options and flexibility. Single voice coil subwoofers can only be wired at the ohm level specified, for example 4 ohm. A dual voice coil will say 4 ohm, but it will actually wire to 2 ohm or 8 ohm. That last sentence alone tends to blow the minds of many, you are not alone. The ohm level needs to match up with the ohm level your amplifier can handle. A DVC woofer has 2 wiring options while the SVC has only one option.

When everything is all said and done, the only real difference between a single and dual voice coil subwoofer is the number of coils, which means a greater wiring flexibility. The power handling, frequency response, box volume specifications, etc. will remain the same for both types of woofers (except in rare cases). Feel free to use the Sonic Electronix subwoofer wiring diagram to help you configure the right subwoofers.

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T/S (Thiele/Small) Parameters

T/S Parameters

Thiele and Small Parameters (also referred to as T/S parameters) are used to define technical electromechanical parameters for a loudspeaker.  These specifications are used primarily by advanced consumers that are looking for low frequency performance of a subwoofer.  A manufacturer runs a series of tests to determine the parameters of the loudspeaker and will typically print this information in the product manual of the subwoofer.  This information is used by intermediate to advanced car audio box builders to make a subwoofer enclosure designed to the exact specifications of the subwoofer. The ratings are named after A. N. Thiele and Richard H. Small, the two men responsible for these detailed parameters.

Here is an example of the T/S parameter from an RE Audio SEX12D4

  • Qes Electrical Q Value: 0.49
  • Qms Mechanical Q Value: 4.5
  • Qts Total Speaker Q Value: 0.44
  • Fs Free Air Resonance: 25.1 Hz
  • Vas Equivalent Compliance: 72.9 liters
  • Xmax One-Way, Linear Excursion: 18 mm
  • Efficiency (SPL 1W/1m): 86.1 dB SPL
  • Sd Effective Piston Area: 480 cm2
  • Re DC Resistance: 2.8 ohm
  • Znom Nominal Impedance: Dual 4 ohm
  • Pe Thermal Power Handling: 600 W
  • BI Force Factor: 17.7

What exactly do these abbreviations and numbers mean?  Below is a list of the different types of parameters that manufacturers can use to define their subwoofers.

Fs: The free-air resonance frequency of the subwoofer, measured in Hz.  At this frequency the weight of the moving parts is perfectly balanced with the subwoofers suspension system.
Q: This refers to the relative damping of a loudspeaker.  This is the “Q” that is in the other Q parameters. The damping is the effect that reduces the amplitude of oscillations within the subwoofer
Qms: This is the subwoofers relative damping (Q) at the resonance frequency  (Fs), including mechanical losses.  Also called the mechanical damping of the subwoofer.  This unitless measurement usually varies from 0.5 – 10.
Qes: The subwoofers relative damping (Q) at the resonance frequency (Fs), including electrical losses.  Also called the mechanical damping of the subwoofer.  The unitless measurement usually varies from 0.5 – 10.
Qts: This is the subwoofers relative damping (Q) at the resonance frequency  (Fs), including all dimensionless losses.
Mms: The total mass of the subwoofers cone, coil, and other moving parts.  It is measured in grams.
Rms: The mechanical resistance of the subwoofer, taking into account the driver’s suspension losses (damping).  It is measured in kg/s
Vas: This is the amount of air that has the same stiffness as the subwoofers suspension. The greater the rating, the lower the stiffness and larger recommended enclosure.  It is measured in Liters.
Xmax: The maximum amount of linear excursion a subwoofer is capable of.  It is typically measured in millimeters. The excursion is the amount of linear movement that the voice coil can travel.  Also referred to as maximum linear peak or peak-to-peak.
D: This is the effective diameter of the subwoofer.  It is usually measured in metric units, however some manufacturers will list it with different units.
Sd: The surface area of the cone measured in square centimeters.
Vd: This is the maximum amount of linear volume displacement the subwoofer is able to produce.  It is the total air volume the subwoofer’s cone will move, measured in cubic meters. The formula Xmax multiplied by the surface area (Sd) is used.
Re: Amount of DC resistance of the subwoofer when measured with an ohm meter.  Typically, this will read less than the impedance rating of the subwoofer.
BL: Total magnetic strength of the motor structure measured in Tesla meters.
n0: The reference efficiency of the system.  It is often more accurate than the manufacturers sensitivity rating and is expressed as a percentage.
SPLo: Represents the subwoofers Sound Pressure Level (SPL).  The rating is measured at 1 watt, from 1 meter in front of the subwoofer.
Pe: This is the thermal capacity of the subwoofer. Using the driver at higher ratings can cause damage and failure to occur. It is measured in watts.
Pt: This is the thermal power handling of the subwoofer and is typically the recommended RMS rating of the subwoofer measured in watts.

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Differences In Subwoofer Sizes

Cars come in all different shapes, sizes, flavors and variants. So do subwoofers, speakers and amplifiers.  It is this fact alone that allows everyone to get exactly what they want, but what good does it do if you don’t know what you want because you have no idea what it all means? This kind of confusion is common place in the world and turns even the most knowledgeable of humans into babbling messes. I am particularly eager to inform you about the different subwoofer sizes as this seems to be a common confusion among many. The four most common subwoofer sizes are 8, 10, 12, and 15 inches. Size is important ladies and gentlemen, so let’s get to it!

8 inch Sub – Kicker L7 08S8L72

8 Inch Subwoofers: These subwoofers are the standard small woofer and can normally be found in stock sound systems in cars. They have been deemed the smallest woofer that will still get you nice bass. 8″ subwoofers add a bit of rumble, or flavor, to your cars music without sacrificing space. Because of the small cone area and weight, it is easy for the magnet to move the assembly resulting in punchy, accurate bass reproduction.

10 Inch Subwoofers: These subwoofers are common in smaller cars and are noted for their responsiveness and compact size. They cannot hit the lower frequencies as well as a 12″ woofer but they are much quicker to the punch. 10″ woofers are usually selected for those who listen to a lot of rock, country and metal. It is not uncommon to see two 10″ woofers to get punchy yet loud and crystal clear bass.

12 inch Subs – Kicker CVR122

12 Inch Subwoofers:  By far the most common subwoofer is the 12 inch subwoofer; it’s a great mix of accuracy and loudness. They hit the lower notes without using all that much power. A 12″ woofer can be both punchy and boomy, this is where your box comes in to tune your woofer exactly how you want it. If you are torn between punch and boom, go with a 12″ woofer, it is a safe bet.

15 Inch Subwoofers: These monstrous subwoofers produce lower frequencies better then the latter woofers due to their large cone area. 15″ subwoofers easily tackle long resonant bass notes and are a top choice for bass heads. However, because of the cone size and weight, it is difficult for the magnet to slow the cone down, so sound quality lacks but boomy bass shines through. These woofers are ideal for rap, r&b, and techno.

Note: These are generalizations based on average subwoofer sizes if all of the mentioned woofers are equal in material and craftsmanship. An 8″ speaker can be designed to play low notes and a 15” can play higher notes. Cone size is no longer a completely accurate way to determine what a subwoofer can do. Mid range frequencies are best produced using light weight cones, and low frequencies are best produced with heavier cones. Enclosures play a huge part in the performance of a subwoofer as well. This is a general guideline to get you on the right track!
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