GuitaRF

Any reviews from anyone on the ISK? I've been thinking strongly of getting one of the ISK Little Gem pencil condensers to accompany a 2b . . . I just ordered one of the se GuitaRF filters for both recording my guitar and amps. Seemed like a cool device to help with my untreated space.

Any experience with the sE Electronics guitaRF Amp/Mic Reflexion Filter? https://www.sweetwater.com/store/detail/GuitaRF Will be tracking guitars in a large room, that's untreated - some furniture to absorb sound, but no real treatment. Will something like the GuitaRF be valuable in this situation to minimize unwanted room reflections? Will be close mic'ing with a 57 and Royer 121....

...have is that I like putting large diaphragm dynamics on guitar cabs. RE20/sm7b/md421. Has anyone used the Studio Electronics GuitaRF with those mics or mics of similar girth? Thanks.