Long overdue update. Been incredibly busy lately, so here's a look at the progress I've done with this speaker.I added a preamp board into the speaker. The amplifier needed 2.7V of input sensitivity to reach full output, but my output stage on my Xonar U7 only outputs 1V. This is made from the OPA1642 op amp. The second PCB is for filtering the noisy auxiliary power from the ICEpower amp. The preamp steps up the voltage by 4x. Even though I only need 2.7x, I used 4x to allow spare headroom for the DAC. Now I can finally get full power from the amps and really crank out the SPL.There were many problems along the way. I had a lot of buzzing problems! I had a ground loop buzz problem that took a lot of effort to find the cause, and it was because the RCA connectors were directly mounted to the baffle without an isolator. Even though wood is a terrible conductor, it was enough to cause a very slight hum that was audible since the amp is running full tilt. I had another buzz problem that was extremely peculiar as well, and turns out it was a few screws that were not tightened inside. I had another buzzing problem that was because the rear end of the passive radiator isn't completely flat, so the washers were rubbing each other at high excursions. Another buzz was due to wires slapping the baskets at high volumes. 4 different sources of buzzing, and this has to be the hardest game of whack a mole I've ever played!I did some more tuning of the speaker. I need a really high quality speaker to be used as a reference for this speaker. So I went to a friend's house to use his ATC SCM150ASL's as a benchmark and reference.
Before the tuning, while the Reference Mini held its own quite well, the ATC sounded noticeably better in every single metric. The speaker sounds much better after the tuning, and sounds much more similar to the ATC except in the bass. The ATC is a bit bass shy, and I like mine with more bass.