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bmw e30, how to improve spl?


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ishy_101 
Member - Posts: 11
Member spacespace
Joined: July 16, 2007
Location: South Africa
Posted: August 27, 2007 at 3:18 AM / IP Logged  

Hi Guy and Girls,

I recently did a SPL, with my current setup, I managed a 126.2db on the meter.

My current setup includes 2x 12" Earthquake subs (MODEL: DB-12 Street Pro,1000 MAX, Frequency Response = 25Hz - 1.1k, Sen = 89dB), 1x Earthquake amp( T1000W/2, Number of  channels: 2, Max Power output:  1000 Watts, RMS Power 4-Ohm Bridged: 1 x 400, RMS Power 2-Ohm Stereo:  2 x 300, RMS Power 4-ohm stereo:  2 x 200, Damping Factor:  >800, Cross over Slopes:  24dB/OCT, THD:  >0.005, SNR:  90dB, Class:  A/B), running off a JVC Mp3 headunit 50x4. 

The subs are in a prefab sealed box. The whole system is installed in a BMW E30 Model, with the subs being in the trunk of the car. Power leads are of 10 gauge.

How can i improve on my meter reading, with out doing the obvious of changing the amp. That would have to be my last option.

Much appreciate the help and advice i can get.

Thanks

haemphyst 
Platinum - Posts: 5,054
Platinum spaceThis member has been recognized as an authority in Electrical Theory. Click here for more info.spaceThis member has been recognized as an authority in Mobile Audio and Video. Click here for more info.spacespace
Joined: January 19, 2003
Location: Michigan, Bouvet Island
Posted: August 27, 2007 at 11:48 AM / IP Logged  
With 200 watts RMS per woofer, 126dB isn't too bad, but not real SPL potential, as you have discovered... bmw e30, how to improve spl? -- posted image.
With those woofers, you won't get but maybe 3 to 6dB more than that, and most likely toward the lower end of the 3-6 dB range...
Three things make SPL. Efficiency, cone area, and power. 89dB with 1000 watt max power handling translates to roughly 119dB peak output, anechoic, with cabin gain making up the difference. Two of them, with 1000w each (again, peak) will make 125dB. Vented enclosure might offer an additional 3dB or so. Those woofers are NOT going to do it. You need something rated MUCH highr, efficiency-wise, like something in the CV lines. You are going to seriously compromise your low-frequency extension, though.
A properly designed bandpass could get you maybe an additional 9 to 12dB, but you still are into real SPL territory...
Basically what am trying to tell you is this: You need a: different and/or more woofers, b: VASTLY more power, c: a proper enclosure, i.e. no pre-fab boxes, period!, or potentially a different alignment (at a minumum, a vented enclosure).
It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."
stevdart 
Platinum - Posts: 5,816
Platinum spaceThis member has made a donation to the12volt.com. Click here for more info.spaceThis member has been recognized as an authority in Mobile Audio and Video. Click here for more info.spaceThis member consistently provides reliable informationspace
Joined: January 24, 2004
Location: Pennsylvania, United States
Posted: August 27, 2007 at 10:13 PM / IP Logged  

10 gauge power wires does not equal SPL.  10 gauge should be left on the shelf.  At least 8 gauge power wire for a better-than-factory sound system.  You should be running 4 gauge power and ground.

...and everything that Dorothy Thompson said ^^^.

Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.

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