Have A Question?
Straight from a professional gear head's mouth.
Submit a question, if our pro selects it, we'll feature it in our Q & A.
Aug 13th, 2008 Q&A
Submited by Anonymous
Can two woofers play in the same air space within an enclosure?
As long as the woofers are the same model, size and impedance, enclosed in the appropriate air space (per woofer) and wired in proper polarity with each other, there shouldn’t be a significant difference when the two (or more) woofers are sharing the same space compared to having individual chambers. However, I would suggest creating individual chambers when possible because isolating woofers from each other is beneficial in the event that one of the woofers fails. When a woofer fails in a common chamber enclosure, sound quality will immediately suffer, because the working woofer suddenly “sees” the whole enclosure space and the backpressure will cause the “blown” woofer to move out of phase. If the listener fails to notice the blown woofer, the situation can cause the surviving woofer to fail prematurely.
Submited by Anonymous
The manufacturer of my 12” subwoofer recommends between 0.7 and 1.0 cubic feet for a sealed enclosure. Which size should I make the enclosure?
When most manufacturers recommend a range of sealed enclosure volumes, the “ideal” enclosure size will be the half-way point between the two recommended volumes, which is 0.85 cu. ft. in this case. Choosing an enclosure on the lower part of the range will have a higher resonant frequency and the sound will be a little “boomier” with less low frequency extension. A choosing an enclosure size on the higher part of the range will have slightly better low frequency extension, but the bass may become a little “loose” and power handling may decrease. In general, audible differences are very minimal between sealed enclosures that are within 10% to 15% of each other in volume. In situations where space/size is not limited, I would recommend building the larger enclosure because you can easily reduce the volume of the enclosure by adding foam or wood blocks to experiment with the sound.
Submited by Anonymous
Should I use MDF or Plywood for my subwoofer enclosure? Which is stronger?
Although most varieties of plywood have higher tensile strength (resistant to breaking) compared to MDF (medium density fiberboard), MDF has higher density, making it more resistant to flexing and vibration, which is more desirable for subwoofer enclosures. A high quality birch plywood can be a good choice for subwoofer applications, but MDF is cheaper, easier to cut/shape and doesn’t splinter. Regardless of material choice, I recommend reinforcing the enclosure with internal bracing, which will make it more solid.
Submited by Anonymous
What is the significance of the amount of voltage a head unit's preamp out's have?
A common misconception is that the purpose of a head unit with higher voltage preamp outputs is to play louder than a head unit with lower voltage preamp outputs, but this is not necessarily the case. The main advantage of a head unit with 4 volt (or higher) preamp outputs is that it allows the amplifier’s input sensitivity to be lowered, reducing noise floor hiss and the system’s susceptibility to alternator whine and other induced noises.
Submited by Anonymous
Is it a bad idea to hook the amp ground wire to the battery negative post?
Although I wouldn’t call it a “bad” idea, connecting the amplifier ground wire to the negative post of the battery is not common practice in the car audio industry. In almost all modern vehicles, the steel or aluminum body is used as the electrical ground. There is usually enough steel in the body to pass the “ground current” needed to run an amplifier, so the ground wire can be connected to the body of the vehicle (in a suitable location) near the amplifier, instead of running a ground cable all the way to the battery. A “good” amplifier ground connection should be made to a part of the chassis that is clean, bare metal, preferably in an area where the sheet metal is thick and solid, like a factory bolt or brace.
In the marine world (and with composite body vehicles like the Corvette), the body is made with a non-conductive material, so a ground wire must be run to the battery. Some newer car bodies, while constructed with metal, are assembled with adhesives rather than welds, creating less than ideal electrical conductivity through the body. An amplifier installed in this type of vehicle may benefit from a separate ground wire. For optimal current transfer in a moderate to high power system, I would highly recommend using properly sized wire, checking and upgrading the ground wires between the chassis and the negative battery terminal, and also between the engine block and the chassis (for the alternator ground).
Submited by Anonymous
How do you keep factory remote controls working with aftermarket decks?
Many of today’s aftermarket head units have remote control capability either via wired or wireless input. Depending on the year, make and model of the vehicle, companies such as PAC (
www.pac-audio.com) offer an interface (which requires installation and programming) that allows many or all of the factory steering wheel remote control buttons to operate an aftermarket head unit.
Submited by Anonymous
My amplifier is rated to play down to 1 ohm for maximum output. Is that a good idea?
Most people like to “get what they paid for.” Unfortunately, many people feel that way about car audio amplifiers, and feel like they have to “max-out” their systems in order to be satisfied. Even if an amplifier is able to handle a 1 ohm load, it usually creates a lot of heat doing so, and heat is the enemy of all electronics. If I were creating a manufacturer–sponsored SPL (sound pressure level) competition vehicle, I would wire the amplifiers to maximize output (who cares if you blow up an amplifier!), but I usually try to keep the total impedance of the subwoofer system at 2 ohms for my “daily driver” systems, because it strikes a balance between good output and amplifier reliability. I explain to my customers that even if you owned a sports car that produces 500 horsepower, you wouldn’t always drive around with the pedal to the floor just to get what you paid for, just as you don’t need to squeeze every last watt out of an amp to get your money’s worth.
Submited by Anonymous
Should I add an equalizer or sound processor to my system?
The interior of a vehicle is a very difficult place to re-create high fidelity audio. Less than optimal listening position, poor speaker placement and numerous near-field reflective surfaces are just a few of the obstacles that we face. Assuming that the installation is solid, a high quality equalizer/sound processor can help address some of these problems, if used properly. In the right hands (and ears), a processor can transform a good sounding system into a great sounding one, but without a qualified person doing the tuning, results can be very “hit and miss.”
Information contained in this communication is of a general nature and is subject to change without notice. Information is not intended to provide professional advice or to take the place of licensed professionals. You are encouraged to consult with a licensed professional about your particular circumstance prior to acting on any of the information contained herein. OPTIMA Batteries, Inc., makes no warranties, express or implied regarding the accuracy of information contained in this communication, and assumes no liability for loss or, damage (including death) resulting from the use of information herein.
