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Old 11th June 2005, 08:37 AM   #1
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Default Ultra high Db levels... where do they come from

I was reading a post here and a really high Db number was mentioned. I am totally ignorant on how these numbers are achievable. So if anyone here has any insights please chime in.

I did some quick thinking and can get nowhere close to the numbers quoted. I do believe the high numbers are possible, so I obviously left something out. here's what I came up with....

speaker 93Db@1W

amp 512W gives +26Db
1024W gives +29Db

2nd speaker gives +3Db

Cabin gain +9Db (guess but depends on frequency)

Totaled up (1024W) 134Db

This is way lower than what I have seen. I can think of a few ways to get more Db. Such as tuning the frequency played to resonance of the car, making a resonant speaker box to spike at a certain frequency, addition of mid and tweeters, and removing upholstered parts and other damping materials. I would guess the most likely is the addition of mid and high components, but that leaves the question of what to play.
I am not interested in building a Db beast but I am interested in the engineering in doing so. Any insights or guesses would be awesome.
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Old 11th June 2005, 01:19 PM   #2
Mark Kravchenko
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Default THe winner is

The only way to get louder is more drivers more power and as you alluded to greater cabin gain. Those competition monkeys are basically producing bass farts. Loud yes. Good sound that is debatable.

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Old 11th June 2005, 07:42 PM   #3
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you're basically right


Ported box tuned to the car's resonant frequency can increase the sub's efficiency at that frequency by a LOT. Then feed it 10-20kW (remember you're playing at the tuning frequency, the mechanical power handling of the sub is incredible) and you get high dB numbers. It's pretty simple stuff really, the people who win are the ones who play with their box designs all the time and manage to squeeze an extra dB or two by changing the port size or the firing direction, cementing their doors, etc. Having a high budget so you can replace blown subs is nice too.
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Old 11th June 2005, 09:35 PM   #4
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One more question:

What kind of "music" is typical of this kind of competition? I figure there is no way they are playing anything I would remotely consider music. Square waves are out since they need resonance, and a plain sine wave is out because it woulsn't use the other speakers.
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Old 11th June 2005, 09:38 PM   #5
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Just a sine wave, true SPL cars typically don't even have mids and tweets, they add nothing to the performance of the vehicle. The cars that just compete in SPL events but aren't true "competition" vehicles will normally have mids and tweets for every day listening, but they're turned off for competition.
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Old 12th June 2005, 12:36 AM   #6
micb is offline micb  United Kingdom
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The speakers measured sensitivity/efficency rating often means close to nothing at low bass frequnecys.

Most SPL boxes are large and very efficent. As you say the are oftend tuned so that thay play the vehicles peak the loudest.

It is not uncommon for 3000-10,000+ WRMS used to hit decent SPL numbers, huge banks of batterys are used to supply lots of current to the amps which are often loaded down (sometimes well below 1 ohm) because you get a rise in box impendence and the amp can take it for the short 2 seconds that you play sound for.

Usually to hit much above 150db often requires you to wall the vehicle, although some cars can get loud with a regluar size box.

Lots of port area is often used, it is not uncommon for people to use over hundreds of square inches of cross sectional area.

One of my aquantences recently got burped at 160db+ @ 57hz for longer than planned!

http://users.gridstar.net/~easytease/test.wmv

Harsh.

System specs.

Subwoofers 6x SPL Dynamics 15d2e's and 6x 2000d SPL Dynamics amplifiers! Plus a massive amount of good batterys.

Bear in mind that was 160 on a TL sensor is in the middle of the van with the sensor over his shoulder.

On the dash the van is around 163db one of the loudest in its class in europe!
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