settings used [size=small](Sensitivity and Discrimination)[/size], the headphones used, and the individuals hearing. It really falls onto the operator's skill in discerning 'iffy' audio responses, and almost all Tone ID models that have a more modulated audio will have poor audio tones on deeper and/or smaller-size targets compared with a single-tone audio response.
I used to have a few M6's and used them a lot, and now rely on my MXT Pro with the same 7-Tone ID feature. However, I only use the Tone ID in the Coin & Jewelry mode now and then, often as a way to check some targets based upon the type of site. I might use Tone ID, if I am just kicking back and taking it easy as I cruise a site, like a sports-field, when most fresh-loss targets are shallower. Then the Tone ID is more correct, and I can be alerted to a potentially desired target by the tone.
I also will sometimes use the Tone ID in a site with iron nails. I often hunt at '0' Discrimination and the low, bass-like audio from ferrous trash alerts me that iron is there and could be masking a desired find. I let the 7-Tone ID audio help me, a times. Most of the time I just use the single-tone response because it will be cleaner and crisper, especially on deeper targets, or if they are of odd metal make-up that would fluctuate between tones. Those can be ugly sounds, especially if the targets are mid-depth or deeper.
So, you can experience some depth loss just based upon the audio response not being strong or clean an you ignore the ugly audio report. However, nobody is required to use Tone ID all the time, and both the M6 and MXT Pro have a quick on-and-off Ton ID selection.
Monte