I want to provide a follow-up to my November 2020 post on the modifications I performed on my Omen Dirty Weekend Mk.II and detail some discoveries I have made since then. It has been 3 years since I completed those mods and the speakers still continue to amaze me. In that time I have gradually upgraded nearly every component upstream and the speakers have allowed me to hear every change—the Zu 103 full-range drivers in combination with the Radian 475 beryllium supertweeters are very revealing and I learned that your upstream components need to be up to the task. I love the tone density and “shove” of the modded speakers—qualities Zu speakers are best known for—but wanted to further push my system to achieve greater transparency, realism, resolution, and holographic imagery through upstream components.
In the past year I have dove into the world of L-pad calculators, first order crossover calculators, and the software Room EQ Wizard (REW). The reason being that while the modded speakers are thoroughly engaging, I have noticed that on some music I was missing a bit of upper-midrange and above “presence” especially in female vocals. Measuring the speakers with REW confirmed my suspicions, and I could see a gradual decline in the frequency response starting at 1.5kHz out to 20kHz. The L-pad I used with 3ohm and 4.7ohm resistors calculates to about 6dB of attenuation to the tweeter, so my hunch was that this was the cause. I suspected that by removing the L-pad and having just the 1uF capacitor (like in a stock ODW) would solve this. Bear in mind that a stock ODW Mk.II uses Zu’s 206 full-range driver and Eminence ASD1001 tweeter. In addition, the L-pad used in a Zu Soul Supreme with the 103 driver and Radian 850 supertweeter also provides about 6dB of attenuation, which lead me to the conclusion that the Radian 475 beryllium is just a very different animal than an 850 aluminum, so using a 475be in combination with the 103 driver requires a different filter network.
While I could have re-purposed the 1uF Duelund tinned-copper capacitors I used in my 2020 mod, I didn’t want to take apart the filter network I soldered together in case my hunch was wrong. So when a discounted pair of V-Cap ODAM 1uF caps popped up on PartsConnexion, I jumped on them. Everything I read about the ODAM caps, with their characteristic grain-free sound quality and holographic imagery appealed to me and I was very curious how they would compare to the Duelunds.
With just the 1uF ODAM cap hooked up between the 103 driver and Radian 475be, built similarly to Zu's stock Erse caps or upgraded Clarity caps, they are simply a revelation. They sound just like people have described—utterly grainless, holographic, and oh so smooth. I thought the Duelund tinned-copper caps sounded wonderful, but the ODAM caps really are on another level. I measured the speakers again with REW and was very relieved to see that the frequency response from 1.5kHz to 20kHZ was now nearly ruler flat. Female vocals now have greater presence, and because of the reduced “grain” sound spooky real. I close my eyes, and my brain is tricked into thinking the singer is in the room. Success!
I uploaded a graph comparing the frequency response of the speakers with the Duelund caps/Path Audio resistors versus only the ODAM caps (measured using a miniDSP UMIK-1 mic at 1 meter, volume set to 75dB SPL, with Psychoacoustic smoothing). I am quite satisfied with how smooth the graph is considering my listening room is untreated. There is a slight dip at around 150Hz, so I’m currently considering why that might be and ways to alleviate it. I suspect there might be some phase cancellation due to my untreated room at the first reflection. Or perhaps I'm just at the DIY limit to what can be improved upon with the ODW's cabinet to reduce resonance.
I will end this post by re-stating something I wrote in a post several years ago: DIY will change your life. It literally changed mine. Thanks for reading.