Phasing Issues Becoming Phasing Helpouts!

[carfreak1024]

Well i was doing some reading online and i found an interesting few sentences a guy wrote and he was talking about how when building ported subwoofer boxes you can use the port frequency so that the phasing of particular frequencies can be tailored to make a certain frequency appear to be louder in the car. My question is if you can use this to reinforce the lowbass potential of the car like from the 20-30hz region.

I think i achieved this previously with the port to the rear of the subwoofer enclosure and using minimum port area. But i have absolutely no idea how to explain this.

SR and Silent_Riot and Jeff might know how this works. As it applies to SQ.

[meccalli]

I'm not sure about phasing in itself causing reinforcement which works in the system of driver and enclosure, however measuring peaks and troughs in a vehicle can reveal a lot for sq as well as a resonant frequency. Resonant frequency in cars however are not in the 20-30 hz region but rather maybe 45-60 which as you would probably know is the range used for spl testing for burps and so on. reason being, you can tune the driver system to the resonant frequency of the vehicle and hence produce db gains. I'm not sure of its use in sq as we would not want peaks at all considering SQ is based on flat frequency responses.
In terms of phase, its a tricky thing to grasp. Its really about wavelengths and how their relationships are in their spaces. when they meet they can form alliances or break up, phasing the entry and exit waves can greatly affect how the system performs and give what your refer to as illusion. If you were to plot the box you built with the so called phasing, the actual results will be completely different from what you would see. i saw an example of this in a box where the port had massive airspace and exited the box @ 90 degrees to the woofer, plotted it would cross -3db line at around 50 hz yet it was a super strong super low performer.

[carfreak1024]

^^^^^interesting. So how does one figure out the resonant frequency of their car without a meter.

[nervewrecker]

^^^

you read the third line?

Resonant frequency in cars however are not in the 20-30 hz region but rather maybe 45-60 which as you would probably know

[meccalli]

If you want to determine your car's resonant frequency, the most common method is using a control woofer, say a small 10 or 12 in a sealed box -around 1 cube-with a relatively flat response. The process is then to run a sweep and meter the loudest reading is usually the res freq., however there is also cabin gain which most prefer to calculate and use that as the resonant frequency- at which freq. the highest cabin gain is achieved. You also want to experiment with box placement and see what gives you the best result at your meter placement. Both methods are usually very close. In terms of the control woofer, anything you can probably get for a Q of .7 in 1 cu.ft.

[carfreak1024]

yeah but tailoring your EQ to compensate for the peaks and dips in your car can allow you to maximize your lows.