Speltz/Atma-sphere & Merlins

I asked Bobby about the impedance boxes awhile back and he said I didn't need them.

I suspect your right. Have not tried them, but I think Bobby's speakers are as OTL compatible as you are likely to get.

I have Atma-sphere M60 Mk3s with Coincident Technology Super Eclipse speakers. I tried the Zero boxes to see if there would be an improvement. Instead the sound became ever so slightly veiled but definitely noticeable.

Speltz Zeros are effective in some implementations and deleterious in others. Multiplying impedance is of no help with Merlins, as by design these speakers have a high impedance curve. I experimented with Zeros & VSM-MX to find out if a 3wpc SET amp would be complementary. It was not. Yet the Zeros had previously worked well to mate this low-powered SET to Wilson Watt/Puppies. Wilsons are 4R speakers with difficult dips to 2R. They are also several db more sensitive than the Merlins. The Zeros make Wilsons look like high-efficiency 16R speakers, whereas with Zeros the Merlins look like medium-efficiency speakers with anomolous 20-40R impedance. Bottom line is that Zeros work well when there is a mismatch to resolve.

with the Speltz you can increase the impedance to your heats desire and things will tighten up as you go however there is a sweet spot where you do not want to go higher as the sound becomes dry and too lean, you can definetly ruin the sound with too high an impedance. Also you are near the 'sweet spot' impedance of 12 - 14 ohms according to some of the posts on his website and in my own experience and you will retain the sound of his wire instead of your current wire - weather you will like that part of it or not remains to be seen.