Articles for Audiophiles by Steve Deckert
AUDIO PAPER #019
HIGH SOUND PRESSURE LEVELS
by Steve Deckert
Another e-mail came in today, and it dawned on me that over the past years my subwoofer enclosure designs have been built in over 23 countries that I know of, and the constant unexpected success stories from those who've built them are the very thing that keeps my spirit going!
Perhaps the most popular is the transmotional symmetrically compensated reflex bandpass design that was nicknamed "the Death Box" during its development. That particular cabinet I did 103 variations of until I could no longer optimize it any further. It was designed to load properly in cars and without exception with only a 10 inch subwoofer, performed better than conventional wedge style cabinets using dual 12's.
It's transmotional design (Figure 2) made it truly the first generic enclosure for 10" subs that could be tuned to optimize almost any brand of 10" woofer from the $49 specials to the exotica. To date I have sold plans for over 6500 of these cabinets worldwide and almost all the feedback has been positive. The best performance report I received was from a serious IASCA competitor who installed 4 of these cabinets using 4 of our DHM-108 woofers and hit 151.8dB during the Outlaw SPL Contest last year, and did it without any audible distortion or clipping.
BUT MY FAVORITE is a ZEN DESIGNED series of cabinets I called the Wicked One. Pictured in Figures 1,3 and 4) this formula for a binaural folded horn can be scaled also to work with a large family of drivers. It's neatest feature is the fact that I figured out you can share the last order of a horn flare between two horns if you couple them properly, thus reducing the size of your enclosure by half. A Wicked one is 12"H x 36"W x either 24" or 36"D depending on where you scale it. Not very big at all considering what it does. Trust me the name says it all. Anyway, today I got another email which put my mind on this train of thought and motivated this rather self indulging paper.. It is representative of dozens of similar emails that I have stashed away. It reads as follows:
"I wanted to let you know that today at a USAC show in Birmingham Al. A friend of mine that has a Wicked One box that I built went through extreme spl with 4 MTX Thunder 5000 10's powered by a MTX 225HO did 161.3, the high spl of the day. I also have a question. Have any of you messed around with Cerwin-Vega Stroker subs? I have a friend that has 2 Stroker 15's and is interested in a Wicked One box. What do you think about this? Thanks for any help"
-Tommy from Hoover Al.
The reason I wanted to let you know about this isn't really to toot my own horn, but because I am relatively certain that you probably didn't realize these kinds of SPL's are being obtained. This is approximately impossible in a house regardless of power, so it should make anyone who thinks they have a ball bustin stereo, think again. It wasn't but a few years ago, maybe 5 or 6 that these high SPLs were impossible to achieve even in a car. In fact when I was in the business in 1992 the world record was around 148 dB and that was done with 26 ten inch drivers in a van. Hitting 161.3 using only 4 - 10 inch woofers is testimony to the all knowing forces above that inspired the design during a Zen session at the workbench. Thank God when I discovered that channel I was smart enough to listen.
That original Wicked One enclosure was done in around 1995, and then a virgin folded horn shown on the left happened in 1997 and encapsulated everything I knew about audio. It was designed as THE audiophile subwoofer. Imagine bass that has the speed and transient detail of electrostatic panels...
Back to the point:
In the past 20 years car audio has become more lucrative than home audio in many urban areas, with the emphasis on BASS and maximum SPL. That's of course rather unfortunate but what would you expect from young kids who are all too easy to convince that "more is better" ?
During the time I sold and designed "high-end" car audio systems, I observed a pattern that was repeated by most young boys just getting into their first loud car stereos. It too is rather unfortunate, but goes something like this:
Kid comes in and wants the biggest woofers he can fit in his car. We try to educate the kid that more bass can be obtained with smaller drivers talking about cabin gains in the vehicle and so on. Kid doesn't get it. We demonstrate by letting him try the biggest box he can fit in his car for a couple days. Then we remove it and install a "Death Box" with a single 10 inch woofer. Kid has more bass, is amazed. Kid has friends with 15's that don't have as much bass, friends come by. We fix friends up. A few weeks go by and Kid returns claiming his bass is not as loud anymore. We check, and discover it is exactly as it always was, no change. Kid is suffering from the first stages of continued compression and has temporary hearing damage. Kid needs more bass - in his own words. We kick it up a notch and give Kid what he wants. Two weeks later kid returns claiming the bass is not as loud as it used to be. We check, no change. You get the idea.
There will be an entire generation of deaf audio enthusiasts who were brought up on CD players and Best Buy receivers, largely pathetic electronic music and so on. These people won't know good sound if it bites them in the ass, so in the end the industry wins.
Personally, I blame the whole thing on front wheel drive. Back when cars were cool, and V-8's roared through the parking lots, kids had a way to flaunt testosterone. Now most cars are a joke in the horse power department so rather than be measured by how fast their cars are, it's how loud they can boom.
Naturally, with SPL levels now reaching levels that will launch the front windshield onto the ground... we all need to be careful!