Audio Level Measurement (SPL Measurement)

Retepetsir

King of Subsonic
Arnold, you asked about this in the other thread :)

The best thing to do to begin with is get your system scoped, which basically means using an oscilloscope and a test tone to make sure that your system is setup to achieve maximum output without driving the amp/speakers into clip. A clipped signal (flattening of the peaks of the sine wave audio signal) can quite often result in toasted equipment :glance:.

Once that's done, you might want to find out the dB output that your setup can acheive. This is done with a special audio mic and measuring device, usually designed for in-car use.

The old standard (used in competitions) was the Audio Control 150 or 160, measuring to 150db or 160db respectively. The mic is attached to the windscreen on the passanger side of the car.

However, the new standard is the Termlab, which is more accurate, and actually measures slightly lower than the older mic's (by around 5-7db) but has greater accuracy. The Termlabs are around £500 to buy, which is expensive for most people, but a bargain for the spl competitors....

i.e. A 150db score on the old mic's would result in around a 145db score on the new mic's.

The current world record is something stupid like 177dB on the new mic's, which to put it mildly, is insane!

It's good fun measuring SPL (sound pressure level), but you need to remember that a lot of factors effect the final reading! From box tuning frequency, to sub choice, to frequency that is played for the reading, the power per sub, etc, etc.

The pro competitors tend to just 'burp' their subs with a single frequency for 3 seconds, to get the highest score possible.

However its much more fun to see what score can be acheived with music :devil:

If you want your car metered, I know that you can enter the free 'TALON' talkaudio compeition at the talkaudio T-meet's. For more info, checkout their forums at www.talkaudio.co.uk. It's also a great place for looking up answers to questions, and asking for advice.

Hope that kind of helps people!
 

Ed

Fusion Motorsport
MSC Founder
Official MSC Trader
Mine was playing music. And I got 142 from a single 12inch sub. However my previous set up in a previous car was much louder, had two 15's was far far more efficient and also the system as a whole sounded so much nicer. I have never heard anyone in a micra achieve in my opinion what that sounded like, again in my opinion I built it to sound - not looks. :)
 

Arnold

www.alanarnold.co.uk
Moderator
cheers for that info Pete. I signed up there ages ago to buy that brax voltmeter but never stayed on there after that!

Ed, so how did you measure that reading? Thats quite impressive for one sub isnt it?
 
OP
OP
Retepetsir

Retepetsir

King of Subsonic
Ed said:
Mine was playing music. And I got 142 from a single 12inch sub. However my previous set up in a previous car was much louder, had two 15's was far far more efficient and also the system as a whole sounded so much nicer. I have never heard anyone in a micra achieve in my opinion what that sounded like, again in my opinion I built it to sound - not looks. :)

Didnt realise that was from your Orion, but thats about right with the power it was getting :)

Was that an average over a period of time? 142 is about 135dB on the Termlab, which is a decent score for a ported 12!

Same with my new system, I'm aiming for the quality of the sound over anything else, but it still goes loud when wanted.

I'm looking into getting Image Dynamics Mini Horns next, but I need to measure up the dash first to see if they will fit where required...!
 

Ed

Fusion Motorsport
MSC Founder
Official MSC Trader
Horns rock! I used to utterly love my USD wavequides.
 
OP
OP
Retepetsir

Retepetsir

King of Subsonic
Ed said:
Horns rock!

I've heard that from so many people so far....

Even though they go under the dash, they usually bring the soundstage right up high, and are fairly efficient so dont need too much power to drive them nicely.

Cant wait to get some anyway :)
 

Ed

Fusion Motorsport
MSC Founder
Official MSC Trader
They are very efficient in comparison some exceed 15% or so compared to a sub which from memory is at best 1-2% still took 250w rms /ch to balence with the bottom end. the best thing though is the huge frequency response of a good horn (down to 1khz) that means the mids have much less work to do and again they can then be optimised.
 
Top