(For the record, mentally planning out projects is how I cope with the stress of being in the Texas Legislature. Planning, building, and experimenting is my happy place. I just wanted to share my findings with my fellow nerds.)

The last time I posted about my system, I had said that I would work on integrating my PC laptop and running room correction on the software side next. Well, time and ADHD makes fools of us all. I got a bit side tracked... and ended up in two pretty awesome rabbit holes.

Rabbit Hole #1 - Cheap Tubes

I've been thinking about adding tubes to my system for a long time. People have raved about the sound, but I've never really understood what the "tube sound" meant. I've seriously considered the Shiit Freya+ for a long time, but the $1200 price tag was just too much without knowing what exactly I'm getting. 

In the last updates, I had been adding pro-audio equipment to compliment my existing home-audio system. I had been so happy with the results that I decided to see if there was such a thing as a tube pre-amp for pro-audio... and... Oh my stars. What sweet Pandora's box of insanity have I opened?

The answer is a very exuberant YES! There are lots of pro-audio tube pre-amps that run the gamut of specs and prices. (Most are listed as microphone pre-amps.) There's stuff as low as a hundred bucks and as much as $5k to 10k. I found a gently used ART Pro MPA II that seemed to have nice specs for few hundred bucks. 

So, now, I pass my DAC XLR output to the MPA and then to the dbx Active Crossover. I don't know why more people don't do this, because this is amazing.

The pre-amp has two separate amplification components. First there is the tube gain control, and then there's a secondary class A/B amplification gain. Basically, this means you can control HOW MUCH of the tube sound you want. You can go from basically 0% tube amplification to saturated, clipping-level tube amplification. If I want a more analytical sound, turn the tubes off. If I want to relaxex listening session, then 2/3 tubes. I don't know of many home audio tube pre-amps that allow you to do this.

The level of control is amazing. You can play with it and hear the soundstage expanding effect of tubes. I've been tinkering with it, back and forth, for days. It is great fun if you like experimenting. Best part? I got good "tube sound" for a few hundred bucks and it looks super cool.

The only downside is that it does add a bit more noise to my otherwise pitch black class D system. But, the barely noticeable increase in background noise is totally worth the "tube sound" for me. 

I'm going to be saving up for the higher end models now.

Rabbit Hole #2 - Omni-sound

So, a certain website, with the initials P.E., had a big sale on some pretty cool looking GRS RT2.0 ribbon tweeters. I didn't want to pass on the sale, so I got a pair in case I wanted to build some bookshelf speakers later.

Now, I had these tweeters just taking up space in my house, and I was not ready to build new speakers yet. Then, I started thinking about my only other real complaint about my Clayton Shaw Acoustic Lab Caladan speakers: that they're not truely omnidirectional as open baffle speakers are supposed to be; because the back of the tweeter is closed. Then I remembered that the Bitches Brew speaker project added a back-firing tweeter to artificially create an omnidirectional sound.

So, I got a cheap, but great sounding Chi-Fi amp (Fosi ZA3) to power the speakers. I used some camera clamps to hold the RT2.0 to the Caladans. Presto, we have some audio fun.

Here were my experiments:

1. As a Super-tweeter

I changed the dbx Active Crossover from 2-way to 3-way. Now, the subs are set to low and crossed at 140hz, the main speakers set to mid and crossed at 3k, and the RT2.0 are set to high. 

Sounds horrible. Not exactly sure why, soundstage was all over the place. Weird artifacts. No like. I tried changing the mid/high crossover to 9.6k (the highest it goes). Nah, still sounding awful. 

No, thanks.

2. As a dual, parallel tweeter

I ran the RCA loop-out output from my XTZ A2-400 amp through a pair of RCA line level 2500hz high-pass filters (the A2-400 is getting a >140hz high pass signal from the dbx Active Crossover, but the RT2.0 needs a 2500hz crossover). I used the WiiM Pro to re-do room correction now that there are two tweeters facing me. 

The sound is interesting. Very, very detailed. Analytical. You can hear everything in much greater detail. But I would not say that the sound is better. First, there's some weird artifacts (I think it's comb filtering as the sound sounds muted in certain parts). Second, the great sound stage has been flattened by about 50%. Third, it tends to be too much after a while. It feels exhausting.

Interesting, but not keeping it. 

3. As a back-firing tweeter

This was my original idea before trying out ideas 1 and 2. I used the camera clamps to flip the RT2.0 to face up and back. I used the WiiM Pro to recalibrate the system.

Bam! This is it. It sounds amazing. I have the Fosi ZA3 backed down to about 75%. (Any higher and the RT2.0 become tinny and overly bright). The effect is immediate and apparent. The additional back-spray makes the music sound larger and more substantial. Especially on live recordings; the sound just feels more life-like. But that's kinda the point right? Live music comes from all directions. 

I could not be happier with this. The soundstage feels significantly deeper and wider. Additionally, the off-axis sound is incredible now. Just standing around the room, you feel like your not missing much. 

Definitely keeping it. 

I might experiment with using an cheap $10-15 full-range 3 inch driver and see how that sounds. (The RT2.0 still feels too bright and sharp even as a back-firing speaker. And I can run a full range driver without the high-pass filter.)

Oh, and I also got a great floor standing rack from SoundTown. It's really nice and solid. It looks good, and it's an unbeatable price.

BTW - my pro-audio stuff came mostly from Sweetwater. Pricy, but their support people are the best. 

I hope y'all enjoyed my audio insanity. 


Cheap tubes and omni-directional sound.