Measurements
Contents
The measurements we have made are both on-wall and stand-alone. This to give a good picture of the influence of the back wall. Normally it will be made of stone, so there may be a slightly different response. We have presented all measurements to ATC for a double check.
As you can see, the ATC HTS40 has a clear dip between 1500 and 6000 Hz. This is confirmed by ATC itself. Although they measure a less deep dip. With us it is around the -4dB of the reference axis. At ATC they say -2.5 dB. But the zone is the same. Here the explanation of Ben Lilly of ATC:
It is not a deliberate tuning – we always strive to deliver a neutral sounding product – but rather a characteristic of this particular design.
The broad speaker baffle and on-wall mounting boosts the lower midrange, giving the mid-band response a slight downward ’tilt’.
Some of this is corrected in the crossover, as you would expect but passive designs have many limitations when trying to optimise magnitude, phase and impedance; optimising two of these parameters is relatively easy, three sometimes very challenging. An improved magnitude-frequency response is possible but not without compromising the impedance & phase a little.
That is a clear explanation in our opinion.
If we look at distortion, it’s very low. From the start at 20 Hz, we are already around 1%, after which it drops well below 0.5%. The dome midrange even dips well towards the 0.1%. That’s a good thing.