resonant freq.
09-14-2004, 06:49 PM
#6
hmmm thats kinda strange...whenever I did a transfer function I was +/- 1 Hz of where I needed to be...
what box are you using ported or sealed? and are you testing the box inside the vehicle for peaks...and then outside the vehicle to see what the actual frequency response is of your test box? ... then comparing the output of each test against each other?
I need to do that with my Rabbit still...lol... it works best with an AudioControl meter..never tried with the termlab yet...hmmmm maybe next slow day at the shop i will try it
what box are you using ported or sealed? and are you testing the box inside the vehicle for peaks...and then outside the vehicle to see what the actual frequency response is of your test box? ... then comparing the output of each test against each other?
I need to do that with my Rabbit still...lol... it works best with an AudioControl meter..never tried with the termlab yet...hmmmm maybe next slow day at the shop i will try it
09-15-2004, 06:40 PM
#8
best results using an AUDIOCONTOL METER!
when testing in the vehicle you will need to place the meter where it would normally be placed during a show...for example DB Drag... 12" to the left from the A pillar and 4" up from the dashboard
set your volume so that you will measure aproximately 130db @ 50Hz, record what volume you used and make sure to keep all equalizer settings flat and put the lowpass filter to full as to allow all frequencies to pass through.also make sure your front and rear speakers are shut off. once you have tested from 20-80hz and recorded the output at each frequency you are ready to test the response of the box itself. you may want to try several different positions in the vehicle with your test box, mark and name each position.
when testing the box outside the vehicle try to find a field where you can setup without any surrounding objects like buildings or trees and an area where noise is extremely low(good luck if you're in the GTA)... you will need to suspend the box in the air facing forward and also place the meter 1 meter infront of the box, mic tip facing towards the speakers ( 2 ladders seems to work really well for me and some ingenuity to attach the box and mic to it) same process as inside the vehicle, test the output from 20-80hz and write it down
when you are finished find the difference of the 2 tests...lets say at 40 hz in the vehicle it measured 128.4db and outside it only showed 116.2db it means you have 12.2db Cabin boost at 40hz...reversly if at 65hz it teted 120db inside the vehicle and tested 124db outside... it means you havea 4 db cabin loss at 65hz.... you will find a few spots between 20-80hz that have large cabin gains ..those are the frequencies you want to aim for when tuning you box...my cabin gain is over 20db at 48hz.
hopefully this helps... works awsome for me in street/stock cars walls are a bit more work but the idea is the same. if some thing is a bit unclear PM me i'll try to explain it a bit better
[ September 15, 2004, 07:53 PM: Message edited by: MTA ]
when testing in the vehicle you will need to place the meter where it would normally be placed during a show...for example DB Drag... 12" to the left from the A pillar and 4" up from the dashboard
set your volume so that you will measure aproximately 130db @ 50Hz, record what volume you used and make sure to keep all equalizer settings flat and put the lowpass filter to full as to allow all frequencies to pass through.also make sure your front and rear speakers are shut off. once you have tested from 20-80hz and recorded the output at each frequency you are ready to test the response of the box itself. you may want to try several different positions in the vehicle with your test box, mark and name each position.
when testing the box outside the vehicle try to find a field where you can setup without any surrounding objects like buildings or trees and an area where noise is extremely low(good luck if you're in the GTA)... you will need to suspend the box in the air facing forward and also place the meter 1 meter infront of the box, mic tip facing towards the speakers ( 2 ladders seems to work really well for me and some ingenuity to attach the box and mic to it) same process as inside the vehicle, test the output from 20-80hz and write it down
when you are finished find the difference of the 2 tests...lets say at 40 hz in the vehicle it measured 128.4db and outside it only showed 116.2db it means you have 12.2db Cabin boost at 40hz...reversly if at 65hz it teted 120db inside the vehicle and tested 124db outside... it means you havea 4 db cabin loss at 65hz.... you will find a few spots between 20-80hz that have large cabin gains ..those are the frequencies you want to aim for when tuning you box...my cabin gain is over 20db at 48hz.
hopefully this helps... works awsome for me in street/stock cars walls are a bit more work but the idea is the same. if some thing is a bit unclear PM me i'll try to explain it a bit better
[ September 15, 2004, 07:53 PM: Message edited by: MTA ]
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