Here are some tips for all you SPL competitors out there from Maxxsonics, a leading manufacturer of car audio amplifiers and speakers.

• Sound deaden your vehicle prior to building your enclosure as this changes tuning.
• Upgrade your batteries to the size and quantity allowed based on your SPL organizations rules.
• Upgrade your alternator.
• Run as many runs of POWER and GROUND, from the front battery to the back, as your SPL organization allows. This reduces resistance and voltage drop.
• Ground front battery to sanded strut tower in your engine compartment. Best vehicle ground!
• Make sure all air leaks are sealed in your vehicle so that it will contain air pressure.

CHOOSING EQUIPMENT:

• Review the rules of the SPL organization that you plan to participate in and determine what is best for your budget and class selected.
• Choose subwoofers that will function optimally in the airspace you have available.
• Choose amplifiers that match the impedance and rms power requirements of your subwoofers.

DESIGNING ENCLOSURE FOR TRUNK CAR WITH FOLDING SEATS:

• Measure out for the largest enclosure possible while still leaving room for your batteries and amplifiers.
• Fire subwoofers forward with slot port in the middle.
• Seal off all around the enclosure so that there are no voids between the enclosure and the box.

DESIGNING ENCLOSURE FOR HATCBACKS:

• Two designs are often used. One that has subs firing forward and ports firing back and one where subs fire up and ports fire back.
• Consider external Aeroports in this application with smaller enclosures.

ENCLOSURE DESIGN PROGRAMS:

• Bass Box Pro 6 : This is the best program available. www.ht-audio.com $99.00 US
• WinISD : Good program. www.linearteam.org FREE

SPL MEASUREMENT SOFTWARE/HARDWARE:

• Term-Lab : Best SPL meter available. www.termlab.com $649.00 for software and meter, still require computer.
• Audio Control SA-3055 and SPL-190 mic: Good meter. www.audiocontrol.com Around $2000 new for meter and sensor. No computer required.

ENCLOSURE TYPES:

• Larger enclosures are generally more efficient, but the trade off is that they make your subwoofer reach full excursion faster and therefore reduce power handling characteristics of the subwoofers.
• Smaller enclosures are generally less efficient, but the trade off is that they will maintain power handling characteristics of the subwoofer.
• Larger enclosures reproduce lower frequencies better.
• Smaller enclosures tend to be very peaky and are better at higher frequencies in most cases.
• Sealed enclosures don’t reproduce low frequencies very well and tend to be punchy.
• Ported enclosures reproduce a wide range of frequencies and have much better low frequency response.
• Bandpass enclosures are difficult to design properly and should not be attempted by those without experience designing and tuning them. You have more control within the tuning band, but no control or power handling above or below the selected tuning frequencies.

SPL ENCLOSURE TIPS/TRICKS:

• Round all 90 degree angles either by sanding or using BONDO and sanding them round/smooth. Especially back corners in the box.
• When bracing the walls of your enclosure inside of the box, use threaded rod rather than wood as this reduces turbulence and takes up less airspace.
• Use ¾inch MDF or thicker on the entire enclosure.
• Make your baffle double thick so that the front doesn’t flex.
• Make sure to use wood glue on all joints of the enclosure when putting the pieces together.
• Use liquid nails inside of the enclosure on all joints once the enclosure is glued and screwed together.
• Once all changes are complete with port tuning, secure the port with plenty of screws, wood glue and liquid nails.
• Round inside and outside of port ends to reduce turbulence.
• Once the enclosure is tuned and all changes are complete, coat the entire enclosure with fiberglass resin. It may take 2 coats because MDF is very porous.

HEADUNIT SETTINGS:

• Bass, Treble and EQ must be flat or OFF.
• Loudness or Boost must be off.

AMPLIFIER SETTINGS:

• PHASE at 0.
• SUBSONIC all the way to the left.
• LOW PASS all the way to the right.
• BASS EQ all the way to the left.
• LEVEL ¾ for SPL, in some applications this will change due to headunit output voltage through RCA’s.

SPL HEADUNITS / CD PLAYERS / CD CHANGERS:

• Look for 4volt pre amp outs or better.
• Anti-skip is a good feature to have.
• Pause feature is a MUST.
• Kenwood and Pioneer are trusted SPL headunits.
• CD Changers are ALWAYS better because they are even less likely to skip.
• In an SPL application, it is often best to run 12awg or better POWER and GROUND wire directly from the battery to the headunit. This will ensure that the headunit doesn’t get starved of voltage due to 24awg factory wiring and shut off while burping under heavy stress.

LIST OF MAXXSONICS SUPPORTING COMPANIES:
- Batteries: Kinetik www.kinetikaudio.com
- Batteries & Alternators: Powermaster www.powermastermotorsports.com
- Wiring & Connectors: Hooker www.hookeraudio.com
- Sound Deadening: Second Skin www.secondskinaudio.com