Originally Posted by jchong
Thanks for chiming in Ricci and giving a bit more details about the test.
How does this long term output compression test differ from the CEA test? I notice it is called "long term" vs the CEA test which is described as "burst".
Short answer, the compression test is a much longer duration signal and is more demanding on the sub. It takes more continuous power from the amp and puts a higher thermal load on the amp and driver. The CEA test is a short burst test. To pass, each harmonic has to be below a certain level. The CEA value will almost always be higher than the sweep level. From Ricci's site, data-bass.com:http://www.data-bass.com/know-how
"Power compression sweeps are taken using a 24sec long sine wave sweep covering the range of 10-100hz starting at the base 90db at 50hz level. The level is increased by 5db for each subsequent sweep until the sub exhibits clear distress, the the amplifier exhibits clipping, or the output stops increasing notably. In some cases a final sweep of 2 or 3db higher level was tried as a jump of a full 5db at the extreme ends of performance is often far too much for the systems to handle. 2 types of graphs are generated from this test set. The basic overlay of each sweep which will show how the response changes with each increase in level and another graph which shows only the amount of compression that is occuring in the systems output. Ideally what you are looking for is the least amount of compression throughout the entire bandwidth at the highest sweep levels."
"CEA2010 maximum short term clean output. Maximum RMS short term output is measured at 2m ground plane. This test involved short 6.5cycle duration shaped sine bursts centered at 1/3rd octave intervals of 20, 25, 31.5, 40, 50 and 63hz. Additionally I added further test frequencies at both ends of the spectrum (10, 12.5, 16, 80, 100 and 120hz) to better represent more of the full bass bandwidth as long as the systems were capable of reproducing meaningful output in those bands. The DUT's output level is then increased while the distortion is monitored until either the DUT stops gaining in output level or the prescribed stair step distortion threshold for any harmonic is exceeded. (Disclaimer note: October 2010 1st round tests were not CEA2010 compliant. They were meant to be CEA2010 compliant but we did not have access to the software package to perform them at the time the 1st round tests were conducted in October 2010. The tests had to be approximated in a manual fashion which was very tedious. Since that is the case the data should not be compared to actual CEA2010 tests directly.)"