To Diego Estan,
I read your article on the MartinLogan Motion 60XTi that was published last month. I found the article particularly interesting because I’ve recently become interested in using the XTi-series speakers in the home-theater/music room that I’m building. I was rather surprised by the testing results at the Canadian NRC. The frequency-response plot definitely wasn’t what I would have expected from a speaker in this price range. The peaks and nulls easily take up every bit of the ±3dB tolerance, however, what really grabs my attention is the very sharp bass roll-off starting at 80Hz. I find it difficult to believe that a tower with two 8” drivers would exhibit something like this, especially at that part of the frequency range (your review mentioned the bass was good). I could understand the plot better if it were taken in something other than an anechoic chamber, so I’m wondering what would account for it? Or is there something about the speaker you didn’t like but didn’t want to put in the review?
First, thanks for taking the time to read my review. I appreciate it.
With respect to the first part of your question, our measurements are taken and plotted at 1/24th octave, which is likely why your eyes are drawn to all the little peaks and dips. If you contrast our measurements with, for example, Stereophile’s, that don’t generally provide as much detail or are smoothed to 1/10th or 1/6th octave, ours look a little choppier. That said, the Motion 60XTi’s frequency response is, to my eyes, relatively smooth and likely to fit fairly well into a ±3dB window, even at 1/24th octave. Smooth the chart to 1/8th, 1/6th, or 1/3th octave, like others do, and it would easily fit.
The large drop at around 80Hz and then slight rise at 40Hz is due to the measurement microphone’s placement (in front of the speaker) relative to the 60XTi’s ports (behind the speaker). Based on the impedance plot, the ports appear to be tuned to about 60Hz. Had we captured the extra energy from the ports with a second microphone, then summed their outputs with what’s measured from the front of the speaker, we’d see a much gentler downward slope. Furthermore, bass in an anechoic chamber is always less than what you experience in a real listening room, due to what most people call "room gain."
As to the second part of your question, I definitely did not withhold any negative observations in my review. I really liked the MLs, and, in my medium-sized room, they had plenty of taut, extended bass. I measured a very respectable in-room bass output from the 60XTi loudspeakers to about -3dB at 22Hz! That should tell you something. . . . Diego Estan