In my opinion, all 3 models play sensational. However, they are clearly different.
Falcon C is for me one of the best iem at its price. It is a very energetic sound with very detailed and aerated treble, neutral very detailed mids and fuller quality bass with great control. I like their lightness and airiness in playing. Have very good separation and create space. Male vocals are heavy enough, and female can make a sense of intimacy. Really nice tuned V . However, for the folds to play well they need a strong source. Otherwise, they play flat, tend to pull sibilants, and play narrowly. The important information is that they show their charm only after a long play. It really didn't work out after playing 150-200h. They also react very well to changes in cables and tips. My favorite combination with falcon is ibasso dx160 + EA Eros II and Sony zx300 + EA Ares II + and spinfit cp500.
Dunu dk3001 Pro is one of my favorite iem. Like Falcon C, they only stack up after losing ~ 150h. They play well already from the box, but at first the medium tones seemed closed and I didn't like their vocals. Now they have over 400 hours on the counter and sound great. According to me, they are tuned in V, with slightly shifted mids and more strongly emphasized medium bass. Because of this it may seem that they have a loss in sub bass. Very neutral, but also musical playing, without dragging in any tones. Low tones of very good quality with a strong beat. Mids are neutral, detailed , with appropriate vocal mass. Aerated and retail top, without tendency to sibilants. Very good width and depth with a clear distribution of instruments. Initially, I lacked bass filling. I used spinfitow cp360 added to the set and caught the perfect seal. However, I changed the tips to cp500 and ... there was lower bass, depth and space. Very good and I think it will be a better choice for many than dk4001. The Lyre cable included with the dk3001 pro is also of very good quality and I could not find a better pair for them. I checked the effect audio Ares II +, Eros II, dunu hulk and a few others and no one didn't play better than Lyre ! Some brought bigger changes, others smaller, but none was better enough to be worth mentioning. Hulk make bass fuller, brought the vocals closer and made them feel better, but I like the lyre in the long run. I listened to them on several daps like: dx160, dx220 (with amp8 and amp9), sony zx300, wm1a, ak sr15, fiio m11 and m11 pro and with everyone (except maybe fiio m11) they played very well. However, they suited me best with the dx160. They got bass filling, weight and even greater musicality.
Dk4001 is my favorite model. Initially, with A-B comparisons I often had the impression that dk3001 pro are ... better. Wondering how it was possible and a little incredulous, I gave them time, because learned from experience with previous models, I knew that dd needs time. It also happened. After about 200 hours of playing, the differences finally became clear. Dk4001 play with fuller sound than dk3001 pro. They play stronger and better quality, very fast bass. Sometimes I have the impression that I can't hear the bass booming, but I just feel it !!! The midrange is neutral, slightly tilting in a warmer direction, the instruments have adequate mass, and the vocals sound wonderful. Feel this lightness from Falcons, but at a higher level. High tones the best I've heard. Properly aerated, detailed, with no tendency to sibilate, but if they are in the recording, they will be heard. They make that despite the strong bass base I would place the dk4001 on the bright side of the game. The stage is good in width, but not as wide as in the dk3001 pro. Sepration in the lower model also seems to be better, but the dk4001 sound more coherent and you feel that it is the highest model. What I noticed, however, is sensitivity to the source. With ibasso dx160 and dx220 they sound really great, but with daps from fiio ... I would say, they sound average. In the near future plans to try them with some other high-end daps, but with dx229, dx221 and also with dx160 sounds really phenomenal.