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Ok this month has been totally crazy for me. I feel like I've covered the lower 48 completely this month. From Memphis to Nashville back to Memphis and then to Panama City Beach, FL and then back to Memphis all in a matter of 3 days, but hey I love going to shows so I guess I'd better not complain. In the past 3 months I've had the opportunity to visit my roots in car audio. I attended 2 USACi events and I also got to visit a shop that I used to work at in Ft. Walton Beach, FL, Jimmy's Car Stereo. This was a shop that was started with less then five hundred dollars some short 12 years ago and now it has turned into a mega shop carrying some of the best lines in car audio. I was amazed that this shop had grown from a mere small business to the giant that it is today. My congratulations go out to Brian Majors and the crew for turning a small investment into a great shop. OK enough of the kudos. This month we are going to cover a topic that is much heated and of much controversy, Sound Pressure Level or SPL. I'm going to state some facts and theories that to some may sound absurd, but there true. I studied several great names in car audio one being David Navone and the other being Mark Fakuda, both of these guys are geniuses in the field of car audio and know what it takes to produce SPL. Everyone has different theories or opinions as to this topic. A lot of what I'm going to write in this article is not opinion it's fact. The remaining portion is all opinion so I hope you take it as that. Lord knows I will be receiving hate mail for this one. First SPL is defined as the level, in decibels, of an acoustic waves pressure. Well what does that mean to you and me. SPL is the pressure exerted from a sound-producing instrument such as a speaker or a horn in the form of a sound wave. SPL is measured in Decibels or DB. To produce pressure there has to be the movement and pressurization of air on a fixed object. In most cases this fixed object is your inner ear drum. But in the case of car audio competition the fixed object is a SPL Meter, a device used to measure the pressure being exerted on the microphone the SPL meter uses to measure the SPL. So what does it take to produce high SPL levels? To compete in outlaw SPL and some of the other SPL competitions what does it take to win. First SPL has very little to do with the subwoofer, the box or even the amp your going to use to power the sub. It all has to do with the vehicle the system will be installed in. Now I know what your thinking that's crazy but think about it? If you take and build the an awesome box with a high dollar sub and back it up with the biggest
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amp money can buy and set it out on the ground I your drive way it's not going to sound like it will inside a vehicle. There has to be something for the wave to reflect off of and produce pressure. Lets take a balloon fill it up to 10 PSI of air pressure. This imaginary balloon now has a diameter of 10". Lets now blow this balloon up to 15" in diameter, the pressure is still 10 PSI, why because although the diameter increased the air pressure stayed the same because the balloon had room to expand. Now lets take our 10" 10 PSI Balloon and shove it into a 5"x5" square solid box. The pressure now has increased to 50 PSI (hypothetically speaking) and the Diameter has been reduced to 5"x5". Well what does all this mean, simple to increase pressure the air being pressurized cannot have room to expand. Vehicle preparation is one of the most overlooked areas when anyone installs a system. Most people go out and buy some high dollar equipment backed up by some high dollar amps slap it in a vehicle wire it all up and get pissed cause it doesn't perform like they feel it should. Then they get on a forum on a web site and blast this produce for not meeting their expectations. They forgot to tell you they installed it in the trunk of their car and the trunk lid rattling around was louder then the subs were. I remember back in the day my buddies and me would build these crazy (16) 12" sub systems and (8) 18" sub systems and yes they were loud. I remember watching Wades windshield almost fall completely out, it stayed busted most of the time and then the roof of his Nissan moved like 6" or we could make the doors move 3" or better thinking the system we had built was a world record holder. Cops in our town hated us. We thought we were the bomb. But when we went to shows we always got blown out by guys with half the equipment we had and when you heard it from 10 feet away you could barely hear it. There vehicles were tighter then a can of Heinz pork and beans. We would come thru the line and people's jaws would drop cause you could feel the pressure with the doors shut from 10 feet away we barely was able to produce Db readings in the 150's. Yeah it was a nice crowd pleaser but it killed our pocket books going and competing and coming home with no points towards finals. After awhile we learned from our mistakes and began to read articles on this issue. We later took (8) 12" subs in the same truck but this time the truck was as solid as a Sherman tank and gained 10 to 12 Db. This same truck now has only (4) 12" subs that produce over 160Db. The very first thing you need to do is prepare the vehicle. Brace and re-enforce all areas that can
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