Frequently Asked Questions

Do I need to add a capacitor or extra battery to my system?

Adding amplifiers to your vehicle will put an additional burden on your vehicle's electrical system. This may result in dimming dashboard or headlights especially when extremely loud bass notes "hit". This extra burden can also affect the performance of your system which can be noticed in excessive overheating and shutting down of the amplifiers in the system. Often times adding a capacitor or battery is the quick solution to the problem but it may not be the best solution. For example, a 2000W RMS amplifier will potentially draw up to 240 amps of current depending on the design and efficiency of the amplifier. Even though the normal operation of the amp will probably run less than that on average, even half of that, 120 amps, is more than most vehicle electrical systems supply to run the entire vehicle. Most stock electrical systems use alternators that are between 60 and 120 amps. Even if you add capacitors or batteries your stock alternator will still limit the amount of current that can be sent to the batteries and caps. Although upgrading your alternator may be more expensive, in the long run your system and vehicle's electrical system will perform much better than just adding a capacitor or battery.

Consult your local specialist installer or call 1-800-CALL-MTX for advice on current draw from your amplifier to see what would work best for your system.

Should I upgrade the power wire between my alternator and battery when I install my system?

In some vehicles, the wire size used by the factory between the alternator and the battery is calculated to limit the amount of current that can be drawn from the alternator. This can protect the alternator from excessive draw due to a bad cell in a battery or multiple batteries in the circuit. Upgrading the ground wire is a good practice but you should only upgrade the wire between the alternator and battery if the alternator is upgraded to a high output unit. If you are using a factory alternator, it may be best to assure that the factory wire is in good condition and then leave it alone to so as to avoid damaging the alternator.

What is the difference between a capacitor and a battery?

Capacitors and batteries are often added to audio systems in order to help overcome vehicle electrical system shortcomings.

Capacitor - A capacitor in a system is designed to help an amplifier to compensate for transient current peaks, it is not a power supply.

Battery - A battery in a system is designed to allow extended play time when the engine is not running.  A battery will be an additional load on the charging system.

Alternator - Your vehicle's alternator supplies the actual current to the vehicle's batteries and consequently the sound system. 

What is a mono block amplifier?

A monoblock amplifier is a 1 channel amp (mono literally means 1). Since bass is omnidirectional, meaning you can tell where it's coming from, it isn't necessary to run subwoofers in stereo. you may see 2 sets of speaker teminals on monoblock amps and they will be labeled as either speaker 1 and speaker 2 terminals, or simply + + and - -. that is because the two + terminals are connected to each other inside the amp, as are the two - terminals. The second set is there simply to make it easier to connect multiple speakers to the amplifier. Do not confuse the two sets of terminals as separate channels. if you're not sure whether an amp is a mono or two channel amp, you can look at the labels above the speaker terminals. a multichannel amplifier will have the separate channels labeled as Left and Right, or L and R.

What does Class D mean?

An amplifier's Class refers to the amplifier's output stage. Although a Class D amplifier can also be a digital amp, the "D" does not stand for digital. What "Class D" does signify is that certain parts of this amplifier turn On/Off to create a signal instead of constantly varing the voltage or current. Changing how long these parts are On or Off changes what you hear. Class A and Class A/B amplifiers are always "On" to some extent, being more or less On as the audio being amplified calls for. The benefit of Class D topology is that current only flows when the parts are On, meaning they run cooler and are more efficient. The problem is that the switching creates distortion, so a low pass filter must be used to counter the distortion produced, because of certain characteristics of the parts used in this circuit, it is much easier to adapt Class D technology for low frequency (subwoofers) applications than for full range speakers. See the Technology section to learn more about MTX Patented Adaptive Class D Technology and its added benefits.

How do I match the correct subwoofers and amps?

Matching an amplifier with the correct subs can be a little confusing. The rule of thumb is to match the amplifier RMS power output, (also known as continuous power) to the subwoofer with comparable RMS power handling capability. When using multiple subwoofers, you must total the power handling for all the subs. That number should closely match the amplifier dynamic power.

Keep in mind that many subs are rated in peak power handling, and you always want to find out the true RMS to determine the correct power handling. In many cases you will find, the RMS is half of the peak power rating. For example, if the peak power is 500, the RMS is 250, but that is not always the case. Please contact the MTX technical support department to determine the correct RMS rating for your subs if you are not sure.

What is the difference between single and dual voice coil subs?

It is easy to confuse a dual voice coil sub as a better subwoofer, but that’s not the case. You will get the same output from either sub when used in the right application. Both sets of terminals must be wired up when using a dual voice coil subwoofer. Your amp and the number of subs will determine which subwoofer you would want. For example, if you had a TA5601 amplifier and wanted to run a pair of 12s, you would want single voice coil 4Ω woofers. Wiring the two woofers would give the amplifier the correct 2Ω impedance when wired in parallel.

Read more on single and dual voice coils.

How do I check my subwoofer impedance with a Multi-Meter?

Set the Multi-Meter to resistance, which is measured in Ohms (Ω). With the meter set to resistance, place the + and – leads to the speaker terminals. Depending on the resistance of the voice coil, the actual resistance will vary. A normal 4Ω voice coil will usually range from 3.4-4.4 Ohms, depending on the speaker. When a speaker is damaged it will be obvious, it won't be anywhere near the correct impedance. Most blown subwoofers will show an open circuit or short, and, in that case, the meter would read zeros. Keep in mind, if there is any type of inductor attached (including amplifier) to the speaker, a correct reading will not be received.

What are the RCA to speaker wire cables for that came in the box?

Most MTX amplifiers feature a patented auto sensing turn on technology called Smart Engage. Smart Egage technology allows you to use the signal sent through the full range speakers in your car as the remote turn on mechanism for your amplifier rather than having to install a remote wire from the head unit to the amplifier. This is especially convenient if you are using a factory head unit as it allows you to install the amplifier in most instances without having to remove the head unit making for an easier and faster installation.

What is the EBC port, and how does it work?

An EBC (External Bass Control or RBC Remote Bass Control) is a Remote Subwoofer Level Control (Remote Gain) - Let's say the amplifier's gain is set at halfway, when the remote subwoofer level control is plugged in, you now have external control of the gain from zero to halfway. The installation of this level control is NOT necessary to get full power from the amplifier. Note: One EBC (External Bass Control) can control two or more amplifiers using a mini plug Y adapter.

Read more on External Bass Control.

What does the input sensitivity adjustment on my amplifier do?

The input sensitiviy adjustment, or Gain, on an amplifier is designed to match the input voltage of the amplifier with the output voltage of the head unit (source). Different head units have different pre-out voltages, 2v, 4v...8v. Unfortunately, no one tells you what that means or why they're offered. the speaker level output of your head unit has been amplified internally, the pre-outs have not. everything that an audio signal has to pass through will lower the "quality" of the signal by adding it's own distortion to it. in most cases, it's so little we can't hear it, but it adds up. since the pre-out signal has not been amplified in the head unit, which is why it's considered to be a "cleaner" signal to send to an amplifier. the higher the signal voltage, the better the signal to noise ratio, which is why you see higher pre-out voltages with more expensive head units.

How do I set the gain on my amplifier correctly?

Follow these steps to correctly set the gain on your amplifier:

  1. Selecting the Input Sensitivity Range - Before you turn on your system, you must select the proper input sensitivity range on your amp using the button labeled INPUT SENS located in the GAIN CONTROL section of the control panel.
    •  Setting for Aftermarket Source Units: Refer to your aftermarket owner's manual for line level output specification. If the specification is not available, please follow the instructions listed below. X1 POSITION: 100mV-1V (Typically for RCA Input)
    • Setting for Factory (OEM) Source Units: To check the amount of voltage that is present from the source unit, take a multi-meter, or a volt/ohm meter, on the AC setting, (range from 100mV up to 1V) attach the positive and negative leads directly to any exposed speaker. It does not matter if the polarity is correct, it will read the same amount of voltage. X10 POSITION: 1V-10V (Typically for Speaker Level Input) Note: It is important not to have the amp set up to receive a low voltage signal and give it a high voltage signal. Doing this can cause damage to the amp.
  2. Adjusting the Gain Control - Before you start setting your amp gains, be sure to defeat all EQs ("off" position). You want to set the gain levels properly BEFORE applying any equalization. Start with the source unit's volume around ¾ of the way up, and the gain on the amp all the way down (counter-clockwise). Slowly increase the gain clockwise until the speaker starts to distort. Immediately decrease gain until the distortion goes away. This will be a good reference point on the volume control to where the signal starts to distort. Remember every CD will be different; use common sense and constantly listen for distortion and adjust volume accordingly. The gain on the amp has nothing to do with how much power the amp can produce, just how fast the amp puts out max power. Just like in an automobile, full throttle is very rarely needed.

How do I bridge my amplifier?

Bridging an amplifier is often most useful when you have a 2-channel amplifier that you want to use to run as a mono channel or a 4-channel amplifier that you want to run as a 2-channel amplifier. Bridging is the combination of the left and right channels of an amplifier, using one terminal from each side, to make 1 (mono) channel with a higher output than either channel running separately. A mono block amplifier has only 1 channel and cannot be bridged. The 2 outputs of a mono block amplifier are there to easily connect multiple subwoofers. If you are not sure whether your amp is a mono block or a multi-channel model, look at the speaker terminals. Multi-channel amplifiers are labeled Left and Right while mono block amplifiers are labeled Speaker 1 and Speaker 2. Every amplifier has different requirements for bridging, so consult your manual or installation instructions before making any connections.

How do I bridge my Class A/B stereo amplifier?

When bridging an amplifier, there are a few things you would want to check before you connect the amp to the subwoofers. First, check the minimum load the amplifier is stable to when bridged, and make sure you do not exceed the minimum load. Most MTX amplifiers bridge the same way, using the Left Positive (+) and Right Negative (–) terminals. However, some older models, like the Thunder 942, may use the Right Positive (+) and Left Negative (–) terminals when bridging. Check your specific model’s manual or call MTX.

How do I bridge a Class D mono amplifier?

Since we have come out with the Class D line of amplifiers, we have had an abundance of technical calls inquiring about how to bridge them. It isn't possible to bridge any mono-block Class D amplifiers. All of these models are Mono amplifiers, meaning they only have one channel. Then why does a single channel amp have two terminals (L and R)? We put both terminals there for your convenience. If you have two speakers, it is hard to attach two speaker leads under one terminal screw. Thus, it makes for a cleaner, easier install. Example: If you had two of the single voice coil 4Ω MTX Thunder7500 12" subs (model T7512-04) and wanted to power it with a TA7801, you could use either terminal. Since it is a Mono amp, as long as the speakers are wired in parallel, it will see a 2Ω load. If you wanted to wire each speaker to a terminal, the amplifier would also see a parallel configuration.

What size power wire do I need to connect my amplifier to my battery?

As a general rule you should use the largest gauge power wire that your amplifier's input terminal is designed to accept. For example, if your amplifier has a 4 AWG power and ground wire input you should use a 4 AWG power wire. Consult your owners manual or installation instructions if you are unsure what size input terminal your amplifier has.

My amplifier is going into thermal protection, what can I do?

Thermal protection is not a defect in your amplifier. Every amplifier has thermal protection built into it as a safety precaution against damaging critical electronic components within the amplifier due to excess heat. The amplifier once cooled down will resume playback. If your amplifier is going into thermal protection often, check the setting of your input sensitivity to ensure that it is properly set to match the output voltage of your source unit. You can also lower the volume on your source unit to increase the intervals between thermal events.

What is volume displacement?

Volume displacement is the amount of air that a subwoofer or speaker can move during use. Volume displacement relates to the speakers ability to generate higher levels of SPL. Volume Displacement is calculated by multiplying the Surface Diameter (Sd) of a subwoofer, most often measured in square inches in the U.S., times the Xmax of that subwoofer, most often measured in inches in the U.S., with the resulting volume displacement number being measured in cubic inches. The final equation then looks like this: Vd = Sd*xmax. The values for Vd, Sd, and Xmax can most often be found in the Thiele/Small parameters of the subwoofer.

How do I calculate air space for an enclosure?

It is fairly easy to calculate air space when designing and building enclosures. The formula is internal cabinet length X width X height, divided by 1728 (ex: 12 x 12 x 12 / 1728 = 1.0 Cu. ft.) If you have a complicated enclosure to calculate, you can fill it with liquid; one cubic foot is equal to 7.48 gallons. For more information about calculating air space you can see our article on Enclosure Construction and Enclosure Design.

Does a subwoofer sound different if it is reverse mounted?

A subwoofer that is reverse mounted will not sound any different than a subwoofer that is mounted traditionally. The advantage to reverse mounting a subwoofer is that you can use a much smaller enclosure since the volume taken up by the subwoofer would not be a factor as it would be mounted outside of the enclosure. Read more about controlling phase of reverse mounted subwoofers.

How can I eliminate the rattle my car has when I play my subs?

Subwoofer frequencies often generate a considerable amount of rattle when played at high volumes in cars. The best way to eliminate rattling is to use a sound dampening material to absorb the soundwaves created by the subwoofer before they can reverberate and rattle parts in your vehicle. Sound dampening material is an adhesive material that can be stuck to the inside of doors, the headliner, the trunk or anywhere else a rattle can be heard. MTX recommends ZeroNoise NoiseKiller Mat from StreetWires as an excellent sound dampening option.

My subwoofers are distorting, what is wrong?

If your subwoofers are distorted you may have the input sensitivity (gain) on your amplifier incorrectly set. Distortion is caused when a soundwave has its amplitude adjusted from a traditional sine wave (round peaks) to a square soundwave (square peaks). Square waves are caused when the input sensitivity (gain) is set in excess of the output voltage of the source unit (ie. radio) and the volume is turned up louder than when the amplifier was set. This "amplified" signal results in the square soundwaves that you hear as distortion. You can use an oscilloscope to check the output wave if you have one available or you can use a multimeter and measure the output voltage of the amplifier at the speaker terminal and then use this calculation to determine if your gain is set correctly. Voltage equals the square root of RMS Power times Resistance. For example if you have a 1000W RMS amplifier connected to a 2 ohm subwoofer the optimum voltage should be 44.72V. You can adjust the gain up or down while measuring the voltage until the multimeter measures that voltage and your amplifier would be properly set and the distortion should be eliminated. Watch our Set Your Gain instructional video for more information.

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