By placing the measurement microphone about six-inches directly in front of each driver to be measured should minimize its first reflection back to the microphone. Of course the best, but usually not practical solution would be to place the speakers to be measured either outdoors or in a very large indoor space short of in an anechoic chamber. In my case with the Apogee FRs, the mid-range and tweeter ribbons are crossed over passively and are treated as one driver by the Pre-8. For that reason, I have to set the measurement microphone directly between the mid-range and tweeter ribbons about 16- to 18-inches away from the area in front of the two ribbons. For consistency, I also measure the bass panels from the same distance as well. Unfortunately, moving the measurement mic away from the driver, such as in my case, is not ideal since by doing this allows more time for the first reflection to be picked-up by the measurement microphone.
During the ownership of four DEQXs over the last 12 years, I have found that trying to create a quasi-anechoic environment with easy or economically to obtain items is almost impossible. A specific material may be great at absorbing energy at some specific frequency but actually reflects sound quite efficiency at other frequencies. I have always taken my best measurements when the measurement mic as close to the drivers a practical. Again, about six-inches seems to work best for conventional come and small drivers, but you may need to back away a little when measuring ESL, magnetic planer, ribbons, etc.
For the "trim" adjustment, as I understand it, this setting is used to truncate the lowest frequency of speaker correction. Trim is set so the DEQX will not correct frequencies that occur after the first reflection. You can determine the first reflection after you complete the "Measure Drivers": task by changing the graphical view to.from Frequency Response to Impulse Response and the expand the X-axis noting where there is a small second impulse after the decay of the initial impulse. At this point you can locate your trim slider to position it immediately before the first reflection point. This will create the "perfect" trim or truncation. That being said, there is always some wiggle room either up or down test for what sounds best. Moving the trim slider to the right past the reflection point can make the bass woolly; to the left the bass can get thin. What’s nice is that you don’t need to take a new measurement each time you want to change the trim point, or any other setting for that matter. Just reload the existing left- or right-driver measurement file, make the adjustment and save it as a different file name.
As for attenuation/boost, I too am at a loss on how to use these adjustments. I think that attenuation/boost controls the amplitude, up and down, limits of speaker correction. I played around with these settings a little and the sound always got worse as I moved away from default. I also played with smoothing a little but didn’t find any real difference - but I only moved it down to 9 from 10. So that’s not a real test.
Right now, I've created my best profiles with all the settings in the default positions, except for trim.
I think it would be great if DEQX would document all of these setting in detail. It would sure be a great help to the Gen 4 community..
