It’s been about a month since the completion of these speakers and it’s about time I do a write-up on how I set up and tuned these speakers. I’ve spent the last several weeks and many hours setting up and dialing in these speakers and overall I’d say I am very happy with the results of this setup. I doubt this will be my final tuning/crossover setup with the MiniDSP but for now I’m just enjoying the new speakers and how awesome they truly do sound. Because overall the speakers sound fantastic. Better than I could have hoped for. Of course, my opinion is somewhat/mostly biased. But they literally sound just how the response plots would indicate – flat and neutral. No frequency range sounds out of balance, neither too forward nor too timid. But before I get into the subjectivity that is describing hi-fi sound, let me share the setup.
The above block diagram details the setup for measuring and tuning the speakers. The setup starts with a pair of laptops, one running windows 7 with the MiniDSP 4-Way Advanced Crossover Plug-in while the other is running Lunix Mint Cinnamon and REW 5.19 Beta 4. The sound card is a Behringer UCA222 connected via USB. My measurement mic is a Behringer ECM8000 using the cal factors available from Behringer’s website. Home Theater Shack also has a popular cal table for the ECM8000 (newecm.cal) but I felt like it over-corrected above 10 kHz and wasn’t realistic of the actual response of my microphone. When I use it, it causes almost every speaker I own to have this rising tail at 20 kHz that I just don’t believe. Behringer’s correction factor is more subtle and even though I am sure it still does not perfectly represent my microphone, I feel like it’s close enough for casual home use. See my comparison plot below.
Also the Behringer cal table includes phase. I think the main reason people use the newecm.cal is because the correction factor goes all the way down to 5 Hz to satisfy all the bassheads need for insanely low frequency measurements. Since the mic needs 48V phantom power, I use a Behringer XENYX 1202FX mixing console (which is normally part of my home recording studio) between the mic and the UCA222. A Schiit Audio SCH-13 Sys Preamp allows simple volume adjustment of two different sources. For my modest setup at the moment, I have an old Sony DVD/CD player and an Apple Airport Express. Better sources are in the works, including a real pre-amp, but for now, this is what I’ve got. The Airport Express is more for just convenience of listening than any kind of critical listening. Check out this post here on my whole house audio system.
So I debated doing a really nice all-aluminum housing for the MiniDPs and in the end just installed everything into an old VCR enclosure. The big spring-loaded slot in the front makes for easy access to the USB cables that I keep tucked away in there when not in programming mode. It’s not super glamorous, but is functional and practical. Both MiniDPSs are mounted on standoffs along with four LM317 linear regulator kits I picked up for $2 a piece on Amazon. I had an old 15 Vdc wallwart that after tearing it apart realized it was complete garbage. It claims an output current of 1000 mA which is just about right for two MiniDSPs (they draw 150 mA each) while maintaining some overhead. But with only a single transformer, a full-wave bridge rectifier and one capacitor, this would not be my first choice in powering any audio gear. But it’s nothing we can’t clean up nicely with some decent linear regulators. The wallwart provides 15 Vdc and feeds the first LM317 which takes the voltage down to 10 Vdc. The second LM317 takes the voltage down to 5 Vdc and over to the MiniDSP. Each LM317 claims roughly 65 dB ripple rejection so long as Vin-Vout > 5 Vdc at 150 mA. So with two in series, we probably get around 100 dB rejection which should be enough for even the most demanding audio needs. Since the MiniDSP outputs feed the UPA-700 amp with a fixed 29 dB of gain, everything in the signal path and DC bias paths needs to be dead quiet in order to provide quiet, hum-free and hiss-free experience. I think I succeeded because even though there exists what I would call traditional background white noise in the setup, you only hear it from less than 1 foot away from the tweeter with your ear directly in front of the speakers. Once you back up a couple of feet, everything is dead quite. And this is with the original MiniDSP kit which only claim >98 dB SNR. It’s definitely plenty for me. And yes, the MiniDSP’s are on all the time. For curiosity sake, I plugged my little VCR/MiniDSP setup into a Killawatt meter and measured a measly 3 watts (or 0.003 kW/h) which if left on year-round amounts to only 26 kW/year (24*365*.003). I pay about $0.1/kWh at my house on average which amounts to a grand total of $2.60/year. So to leave on a pair of MiniDSP’s 24-7-365 costs less than a side of fries at Five Guys. In other words, it’s basically peanuts. Which oddly enough, you can also get at Five Guys.
I made six sets of speaker cables that are each 14 feet in length from a 100-foot spool of 12 gauge OFC speaker wire from Parts Express. I bought 12 sets of black/red screw-style banana plugs which dressed up the cables nicely and provide a clean transition from speaker cable to the binding posts at the back of the speakers. I wanted to do something fancier on each side, like bundle each set of cables into some nice black expanded cable sleeving but just ended up leaving the speaker cables exposed for now. It’s functional and does the job. No complaints here.
Here’s a quick shot of the back of the upper cabinet with the nice Dayton Audio Premium gold-plated binding post terminals and aluminum face plate from Parts Express. Normally I wouldn’t go all out and buy such fancy binding posts, but for this build I decided they would complement the high-end feel of the speakers overall. They are super nice and provide a robust quality and feel to the speakers. I definitely recommend them for that great premium look.
Here’s the basic microphone setup for doing near-field measurements of just the midrange driver. I moved the microphone around a lot during my measurements. I did near-field plots of each driver at 0.5″ distances and then 6″ and 12″ and 30″ and 1M distances (approximately) as well as in-room measurements. I haven’t done a lot of off-axis measurements yet. But I do plan to take more measurements as time permits. This mic orientation and distance do not represent all of the measurements taken/shown here.
So this is sort of how the setup looked. The old Dell Inspiron was used to connect to each MiniDSP and provide instantaneous crossover and PEQ changes while the HP Elitebook on the right was running REW for taking and recording all the measurements. I only played with one speaker at a time, so I could make all the adjustments to just one MiniDSP unit. Once I was satisfied with the settings, I saved a configuration file and then loaded the settings onto the second MiniDSP. I did some casual listening of various types of music with each setting. Then I would go back to making adjustments as needed and redo the process of tweaking one unit, taking a measurement, loading the second MiniDSP and then doing some listening. I basically did this for about a month. What I’ve really been doing with this whole experience is educating myself on not only the basics of crossover design but some of the more complex elements as well. I figured I have a really nice set of speakers built into a great enclosure, now is my opportunity to really understand the benefits of different slope rates or crossover types on a really nice set of speakers. I have at my disposal the ability to test multiple filter types and slopes and take tons of measurements to see just what makes one filter better than another.