posted
Ok, when I first put my wall in I used one sub and it was centered in the car. It was sealed from the rear completly. I used a 150x1 amp to run it. At a moderate volume level I did the whole in car response thing and right in the parking lot, same day, same meter, tore my wall down and metered it again outside of the car. I got the normial two gains, one at 41hz and the other around 59hz. The 41hz note was showing more of a gain, so I used it. Then I went with a different port at 46 hz that for some reason gave me a bit more spl at 42hz????
NOW, earlier tonight, I went to a parking lot and ran an in car test over the spectrum (30-70hz). I can't belive what I saw, And I can't explain it. My respones was 123db from 38-51hz...flat by means of radioshack meter. At 52and 53 hz I was at 124, and then it dropped back down to 123 all the way up to 62hz when it starts to rool off at about 10db per octave.
WTF is going on? My box is made for 46 hz, my car likes 41 hz and 59 hz yet I am peaking at 52 and 53?
I also ran a voltage check at a set high volume, it ranged from 54.1-59 volts, 59 being at 52&53 hz.
What does this mean? From what I know, I am guessing that the box is ported at 52hz and it is filling the cars natural response dips almost perfectly. That's what I came up with. The cars resonate frequency filled in the roll off point of the sub....????
posted
LOL, its the radio-**** meter. the thing doesnt peg at 125+ dB, itll just read around 124db. I wouldnt use it above 120dB and dont be so sure its accurate.
------------------ 2-DD 9512's 2-2000X's (for now) 8.0ft^3 box in a civic trunk One big ass port ?????dB's
It's not the size of your woofer, It's the size of the waves your woofer makes!
Posts: 1247 | From: Fullerton. CA ,USA | Registered: Oct 1999
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posted
Actually, the rat-shack meter reads 1db low@50hz, 3.5db low@25hz, and 5db low@20hz. In the manual for my Sunfire True Sub Signatures, Bob Carver explains that this particular SPL meter(30-2050) reads low at the different freqs, and only reads average SPL as opposed to peak, so 3db should be added to your measurement as well. He also explains that you can swap out 6 of the caps in the meter, and it will read flat to 20hz. I'm doing the mods to my meter tonight, so I'll let everyone know how it turns out. I'll have to do lots of comparison numbers, but it SEEMS logical, and the caps are easy to swap out...email me if you want the cap values and numbers to switch out.
------------------ -j Still adding parts, but currently running Eclipse 7001, 5961, 55090, 39011, 5122, Nak TD-700, Sharp 15" Flat Screen, Sony PS2, some mediocre mids and highs, and one of my T-Domes...soon will come madness.
Posts: 147 | From: somewhere over the rainbow | Registered: Aug 1999
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