This was the setup of the two ATs, placed side by side in a 'dual afterburner configuration' in a Citroen C3…:
The test rig was set on the passenger's seat:
The measurement microphone's location:
The comparison was done with all conditions, levels and other settings throughout the system equal and untouched.
Only the selector switch was used to alternate between the cabs.
This is the combined plot of all 7 test runs, the different traces explained below.
Here is the full spectrum view:
And here a zoomed view of the low end:
First, the cabs ware pushed all the way forward against the backs of the front seats, leaving about 40cm (16") from the horn mouth to the back door, like this:
In this position I first tested the response with the back door open. The (lower) green trace is of the JBL and the purple trace is of the TB.
I then closed the back door. The yellow trace is of the JBL and the orange trace is the TB's.
Following, I moved the cabs all the way to the back, with the horn mouth right against the (closed) back door, like this:
The light blue trace is of the JBL and the (top) green trace is of the TB.
I then returned the car to its 'normal' configuration, and placed the JBL loaded AT in the trunk, like so:
The top blue trace is of this configuration.
I then took some power and SPL readings. This is 40Hz at 1w:
This is 40Hz at 100w:
And this is 40Hz at 150w:
Summery;
I played a variety of tracks, constantly alternating between the cabs, and to my humble ears there wasn't any noticeable difference between them.
Both sounded exactly the same and just great. Both supplied a nice and amazing low end (down to 30Hz and lower… I know, small cabin…)
In view of these listening tests, as well as the measured plots, I think it is correct to conclude that both the JBL and the TB are suitable and perform equally (well) in the AT.
It definitely looks like the small variations in the JBL's T/S parameters (compared to the recommended TB) are probably not off enough
to spoil the amazing performance of the AT design.
