Woofer Box Aiming Actual Testing (Part 2)

by Eddie Runner (NU5K)

The test gear used for the tests today is as follows:
Computer with the Loudspeaker Measurement System by Linear-X (Loudspeaker Measurement System) hardware and software.
Audio Control TRA - Real Tim Analyzer
Toshiba Oscilloscope
Sound Technology Signal generator
CROWN PRO AMP
Prefab box with one 12 Memphis woofer (the orange one)

Woofer Testing in Dodge Neon

We chose Dwayne's car to do these first tests on, the car was not running and the cars stereo was not playing, the test system we used (above) uses its own amp and subwoofer box. Our goal here is to measure the accoustics of the car with our test gear, not the gear already installed in this particular car.

	We placed the LMS microphone on a simple tripod in the drivers seat and left it alone for this cars entire series of tests.
In this picture you see the prefab woofer box and the 12 inch woofer is aimed towards the front of the car. This woofer box is hooked to our CROWN amp on our test bench (pictured above).
	In this picture you see the prefab woofer box and the 12 inch woofer is aimed towards the rear of the car. The results of the test are pictured below.

click on this picture for a LARGE closeup view

This is the test results for the Dodge NEON. The test is a sweep from 120Hz to 20Hz (typical frequencies run through a car stereo bass xover)
The Green trace that doesn't look so good is the BOX AIMED FORWARD! You can see a huge dip (cancellation) at about 100Hz (about 23db!!!!!)

The Purple trace is the exact same sweep! The only thing we changed was to turn the speaker box around and aim it towards the rear of the car! As you can see there is MORE BASS on the purple trace.

Woofer Testing in Chevrolet Tahoe

Again, just like we did in the NEON we placed the LMS microphone on a simple tripod in the drivers seat and left it alone for this cars entire series of tests.
	Here is the test box aiming towards the front of the car.
All we did was to turn the speaker box around to aim to the rear of the car... We did not change the speaker wires, we did not change the volume control, we did not change ANYTHING! (the speaker cant be in or out of phase with any other speaker because this is the only speaker playing! ONE!)

On this graph of the Tahoe, the purple trace is the REAR AIMING and the green trace is the FRONT AIMING....

We also played with the box aiming sideways and straight up with varying results, the REAR facing was the best off all the tests we ran in both cars.

We also ran some FRONT DOOR CLOSED and FRONT DOOR OPEN tests which also had major differences.
We didn't bother publishing all the test results we got because we thought it would just make this page alot bigger than it needs to be.

Woofer Testing in VW Jetta

Today we set up and did a couple of more cars, Now that I have this LMS computer working again and have the latest version of the LMS software I should be doing alot more of these actual measurements for our tech pages.

The Mic placed in the drivers seat as usual.
	James positioning the box with the woofer facing forward.
Picture of the woofer aiming backwards NOTE: all these tests are with the TRUNK LID down! We show you the picture with the trunk lid up so you can see how the box is positioned, I imagine most of you know this but just to be sure there is no misunderstanding the trunk lid IS DOWN DURING TESTING!

Jetta
PURPLE - box aiming towards the front of the car.
RED - box aiming towards the rear of the car.

This is a different and very interesting comparison of sweeps in the Jetta.
PURPLE - Jetta with box aimed forward
GREEN - Jetta with box aimed forward and drivers door open.
RED - Jetta with box aimed forward and trunk lid open (and doors closed).
(this is one where we DID do it with the trunk up!)

Woofer Testing in VW Bug

Bug with box aiming forward
	Now we swapped the box around to aim to the back for the next sweep.

The measurements of the VW BUG
PURPLE - Box aiming forward
GREEN - Box aiming backward

Tests performed 12/03/03 and 12/04/03 at River Oaks Car Stereo by Eddie Runner (NU5K), Dwayne Jones (KB5YTA) , James Kern (KD5QWG) and Chris Koonce (KD5TOM)...
Contents of this page copyright 2023 Eddie L. Runner

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