FAQ : Frequently Asked Questions
Can I run my amplifier at a lower impedance than what the specs say?
DD never recommends running one of their amplifiers lower than the recommended impedance. If the reactive impedance falls below the recommended spec it can cause severe damage to the amplifier.
Why do I need to turn my amp gain down? It's louder all the way up!!
A gain control IS NOT A VOLUME CONTROL. The gain control does not limit the power of the amplifier. A gain turned to 50% does not limit the amplifier to 50% power.
A gain control's only function is to tailor the amplifier's output to the volume knob on your head unit. All headunits put out different voltages, the gain knob allows the user to adjust the amplifier output to use the full range of volume control on the headunit.
An amplifier can be pushed to full output or higher(clipping) with input of less than 1 Volt. EQ settings, like bass boost, subwoofer level and loudness controls wil increase the output voltage of the headunit. Every 3dB of EQ gain will double to headunit output voltage.
One of the most common install mistakes that leads to audio component failure is setting the gain levels on your amplifier too high. Having the gains set too high results in clipping, which turns into heat, which will in time kill both woofers and amplifiers. The inputs on DD amps accept 6 volts to .2 volts, labeled on the amplifiers gain control/s. If you're using a headunit with a 2V RCA output your gain should be set at roughly 50%, and you're using a headunit with a 4V RCA output your gain should be set at roughly 25%. These settings will vary slightly with every install, but for the majority of installs this is a good rule of thumb. A couple of things that can alter the standard gain settings are the use of bass boosts and the use of different types of source materials: i.e. CD, IPod, thumb drive, radio, MP3, etc as they will all affect your headunits RCA output.
What should I tune my box ports to?
You should tune your box to the style of music that you intend to play the majority of the time. The DD box parameters that you can find on our website will result in a box tuning around 40hz. A 40hz tuning is good for a very wide range of music. If you need to tune your enclosure for a more specific style of music you may need to lower or raise the tuning accordingly. One popular misconception is that tuning a box to a certain frequency determines how loud your box will be at that frequency. The truth is that when playing the system at the tuned frequency you speaker will have the least amount of excursion and the amp will see the highest reactive impedance. This will result in more control over the woofer in that tuned frequency.
Why can't you put DD subs in a sealed box?
First off, we do have subs that can be used in a sealed box. The 1000 Series have lighter suspension and work pretty well right out of the box. All DD subs will work better when they break in.
Regular suspension DD subs are designed to last a very long time, the suspensions take time to break in, then they stay consistant just about forever. A fresh DD sub will have a high resonance frequency and a higher box resonance than a sub which has a loose suspension. It will take time for the DD sub's resonance frequency to drop.
Sealed boxes are on the low end of the scale for power efficiency and much of the energy built in to a DD sub will be wasted. One might expect to get 50% or less of the potential system energy.
If a sealed box is being picked for smaller box volume, then we suggest the use of the DDbox system to pick the correct box size first, not pick a driver diameter first. We developed this system to deliver a higher percentage of system efficiency. We have high efficiency subwoofers that will work in boxes with less then 0.4 cubic feet of airspace. One of our 8" woofers in a DD box will outperform a 10" or 12" driver being used in the same size sealed box. The 8" will play deeper, louder, cleaner with better sound quality.
Why does DD say not to use my box building program?
We make the subwoofers to work in our highly efficient box system tailored to the transfer function of a vehicle's interior. In todays high energy audio systems, high amplifier power and the resulting high moving mass force are more dominant factors than enclosure air load effect on the woofer's suspension compliance and motor force. Therefore, we've built and tested countless woofer variations to work in specified enclosure sizes with the best possible sound quality for a given power bandwidth, we build the woofer to work within a box parameter, not the other way around.
In addition, high motor strength, overdamped, controlled suspension woofers are difficult to measure accurate T/S parameters, nature of the beast. We have found that the parts used in a woofer to make pretty T/S parameters at less than 1 Watt of power are not the right parts to use in a woofer that will be used in the real world.
With a DD woofer, you'll notice a high BL product, much higher than the Qts indicates. The Fs looks high, but the suspension is built for moving mass control under real power levels. This also raises the Qts.
After a DD sub suspension breaks in, the Fs will drop down in the mid 30s. When you use the DDbox system, the sub will play any music content you throw at it and do it with clean accuracy. The sub and the box work as a system, it is what all the parts in the sub were designed for.
Can I have a system that hits high SPL numbers and has great sound quality?
SPL and sound quality are two totally different aspects of system design. SPL scores are set numbers, but sound quality is very relative to the listener. It is possible to make a loud system sound good, but sometimes you will sacrifice musicality when you concentrate on a specific SPL score.
What crossover points should I use to set up my system?
The following are general frequency ranges that can be used for basic system set up.
- Subwoofers: 30hz Subsonic to 80hz Low Pass
- Midbass: 80-250 hz
- Midrange: 200-3,000 hz
- Highrange: 3,000 hz and up
What is Clamp Testing, and Why should I do it?
Clamp testing is the way to calculate your amplifiers true output power and the actual impedance being driven, in it's real environment. Clamp testing, and understanding the numbers it gives, is a must if competing in SPL or interested in getting more performance out of any system.How to Calculate Amp Power and Impedance:
You will need a Digital Multi-Meter, AC Amp/Clamp Meter and Test Tones/Signal
The Volt-meter/Multi-meter test leads should go directly to the speaker leads from the amplifier. Pick a (-) and (+) to pierce your test leads into. Set your Volt-meter/Multi-meter to AC Voltage and turn on the Peak Voltage feature.
The Ampmeter/Clamp-meter should be clamped around only the (+) speaker wire coming from the amplifier outputs. Set the clamp meter to AC Amperage. Turn on the Peak Hold feature. Do not use the test leads of the Ammeter/Clamp-meter in this process.
When testing the system for output power and impedance at one specific frequency, test using that single frequency. To know the impedance curve and power curve, test tones from 70Hz down to 20Hz in 5Hz increments.
If you don't have a way of generating tones from 70Hz down to 20Hz, you can download the wav files we have created. 70Hz-20Hz ( in 5Hz increments)
If power and impedance numbers for a daily driving system are needed, we suggest warming up the subs and amp to get readings congruent with how the system is normally played, SPL competitors should take readings with coils/amps at room temperature.
Roll up the volume at the head unit that is just under clipping indication on the amplifier.
The Voltage and Amperage numbers are simply multiplied together to get your Wattage. (P=VI or Power equals Voltage times Amperage).
To find out what impedance the amplifier is seeing, simply divide the Voltage by the Amperage. (R=V/I or Resistance equals Voltage divided by Amperage).
To plot a power or impedance curve, repeat the previous test for each frequency, i.e. 70, 65, 60, 55, 50Hz etc.
The commonly used term "Box Rise" is the sum of the subwoofer(s) impedance and the additional acoustic impedance added by the enclosure and the vehicle.
For example, 4 subs wired to a 1.0 ohm load, after running an actual impedance curve, may present a load over 4 Ohms to the amplifier. That 1000w amplifier may be pushing between 200w and 400w of real power.
An informative experiment would be to test the box in its normal position, then change the position in the trunk or cargo area. Try moving the port and speaker about 2" away from boundaries in the cargo area and test it again. The numbers will come out different due to changing acoustic load presented by the new location, affecting the SQ and SPL of your system.
For an Ohm's Law Calculator and other useful tools, try the follwing link.
Why do my head lights dim when my bass hits?
The reason your headlights are dimming is because you don't have enough amperage to power everything in your electrical system i.e. amplifier, headlights, A/C etc, etc.
This is bad for a couple of reasons. First it's hard on the the factory components of your vehicle and secondly it's very hard on your audio equipment. When an amplifier is ran at low voltage/ amperage it compensates by out putting DC voltage to keep up with your power demands. DC voltage burns coils and low input power melts amplifier power supplies. Even if it appears that your voltage never goes below 12v you may still have a lack of amperage. If you are experiencing a charging system deficiency you need to calculate your total system current draw to determine what methods will best solve your problem. The most common fixes are adding a high output alternator, additional batteries, and upgrading the wiring from battery to ground, alternator to ground and alternator to battery.
How do I wire my DVC subs?
There are two ways to wire multiple voice coils together, series and parallel.
In a series connection on a DVC sub you connect the positive lead from one coil to the negative lead from the other coil, leaving one positive and one negative wire unconnected. To calculate the impedance of a series connection you simply add the impedance of both coils. So, if you have a dual 4 ohm speaker wired in series you would have a 8 ohm total load. 4 + 4 = 8
In a parallel connection on a DVC sub you wire both positive leads together and both negative leads together. To calculate the impedance of a parallel connection you take the impedance of one coil and divide it by the number of coils. So if you have a dual 4 ohm speaker wired in parallel you would have a 2 ohm total load. 4 / 2 = 2
What is the SuperCharge option? What will it do for me? Does my box have to be different from a normal DD woofer?
The specs don't change much for box building, the energy of the motor system is increased. In many box modeling programs, the model will show decreased bass due to more control on the voice coil movements. This is an outdated transducer/box model that originated when power amplifers were much smaller and most listening was done a 1-5 watts of power.
In this type of model, the box compliance plays a major role in the total system Q, and too much damping on the coil puts the brakes on low frequency.
In todays systems, the amplifier power dominates the whole system, the resulting high forces generated are more and more difficult to control. Our real world testing proved that overdamped systems, where the suspension and motor have tighter control, allow the cone to move with the original source signal. Traditional systems that look good on the modeling programs always lose control at real world power levels and cannot track the original source signal.
DD speakers will play tight and controlled throughout the power bandwidth. The supercharged versions add even more magnetic energy and you will hear tighter, even cleaner bass.
SPL cars that respond to higher energy levels will see gains in the peak spl possible.
- SuperCharged Motor Structures
Our Z motor research has developed techniques to take otherwise lost magnetic energy and redirect in the areas that increase the strength of the motor.
The SuperCharged option focuses 20-25% more energy into the magnet gap, allowing smaller and lighter motors to equal the drive energy of larger motors. Higher energy pays dividends in the impact delivered by the SuperCharged motors, impacts are sharper, details more crisp and transients more dynamic.
- Faraday Shorting Rings
When the voice coil of a speaker moves within the speaker motor, it will generate a "back EMF" - a voltage opposite of that which is driving it. So, at the same time an amplifier is trying to drive the speaker, the coil in the speaker is simultaneously trying to drive a counter-signal back into the amplifier. The EMF also distorts the flux in the magnetic gap. DD uses Faraday Shorting Rings machined from billet aluminum in the Supercharged option to reduce these distortion effects.
- SuperCharged Motor Structures
Why do my woofers stink?
DD woofers use the highest temperature adhesives on the market. All our voice coils are baked to thermo-set the adhesives. When temperatures around 500 degrees F are seen by the coils, some outgassing from the adhesives will occur. This is a signal that your amplifier is being over-driven and sending a heavy clipped signal to the speaker(s). Immediately turn down the system to let the coils cool, if not, permanent damage will occur. Some outgassing is normal when peak temperatures are approached, the coil adhesive will re-set.
In all likelihood, the volume may only be a couple clicks too high where added sound volume was not increased but clipping amplifier outputs begin dumping heat to the coils. A good rule of thumb: stop turning up the volume as soon as noticeable increase of volume does not coincide with each volume click. In most cases 95% of the SPL can be retained without overdriving the amp.
Why do my wooofers keep burning up?
The two main causes for burnt voice coils are a clipped signal coming from the amplifier and mechanically overdriving the speaker.
This means that in your system's current configuration, you are driving the system harder than it can safely deliver output. There may be several areas you need to look at in order to increase your system's capability.
- Your amplifier may not have enough supply current, battery and alternator upgrades may be necessary.
- You may not have enough clean amplifier power.
- You may not have enough enclosure efficiency.
- You may not have a clean source signal.
Consulting with your local dealer can help diagnose the issues and find an upgrade path to get your system's output where you like to play it.