I had a great time at RMAF again this year. With a 5.1 channel room, we had to allocate a lot more of our setup time for other things besides audio calibration. We had to put together the projector screen and stand; create our own screen wall at the front of the room; setup 13 "bass" traps in the room; setup the projector, calibrate, and make a 3D LUT file; unpack and setup 5 amplifiers, unpack and setup 5 speakers, unpack and setup 2 subwoofers, connect all cables, and a do a bunch of other setup stuff.
I arrived at about 10 am and started carrying things up to the room with my son and his friend. Jeff arrived at about 2:45 pm after I had just finished getting the projector screen setup. I took the boys home in the evening. Jeff and I then worked until about 1 am, slept on the floor of the room, and woke up at 6 am and continued to setup until the show started at 10 am on Friday. We did a few more tweaks with speaker location and some bass EQ on Saturday and Sunday, but left everything else alone.
It was great seeing dlbeck, RMK!, jaimectrs, sandbagger, Mark Seaton, and others. I also saw some guys I've known from other forums. It was also nice to finally meet Jim Hillegass, the owner of JRiver.
I'll start at the beginning of the signal chain and explain a few things.
- I use the media server which I built and is used daily by my family for tasks like spreadsheets, documents, e-mail, audio playback, Blu-ray playback, gaming, etc. It uses a Silverstone GD07 case that I've customized to allow for a Corsair H75 water cooler. This cools the CPU and is completely silent. The graphics cards is a MSI GTX 970 and is completely silent (no fan in use) until the temp is over 60 Celsius, which doesn't happen at all during audio use. The power supply is a Seasonic Platinum which is also completely silent (no fan in use) until the load is over 50%, which never happens. There are six 120 mm Noctua fans, all for air intake, that spin at about 300 rpm. These cannot be heard unless the case cover is off and the ear is next to the fans. The drive is a Samsung M2 SSD drive that mounts directly to the motherboard. It has no moving parts and there are no cables. So, I have a completely silent media server that can playback just about any media and be used for any task.
- My Media Server has Thunderbolt connections so I use an external ThunderBay 4 drive array connected to the server by a Corning Optical Thunderbolt cable. I only have the array loaded with three 4 TB drives so I have 12 TB of disc space. Since the drive array is cooled with a small fan, it was placed in the bathroom so it couldn't be heard at all. The throughput is so great that you can rip and play multiple Blu-rays concurrently.
JRiver Media Center
- This is what makes everything work so smoothly on the Media Server. I had Views setup for Blu-ray Movies, Blu-ray Concerts, CD, Hi-Rez, DSD, and RMAF Blu-ray Concert Songs. I also had an RMAF playlist for 2 channel audio. Since I used different settings and EQ for multi-channel vs stereo, I had two Zones setup. I used a feature called ZoneSwitch to automatically switch to the correct Zone depending on channel count.
The multi-channel zone had bass management set to use a 60 Hz crossover with a 12 db/octave high pass on the speakers and 24 db/octave low pass on the subs. I pulled down a few room modes with two PEQ filters and also applied a low shelf filter at 40 Hz with a gain of -5 dB. This provided for good speaker/subwoofer integration and eliminated too much room gain. Since people sit in a lot of different places (we had six seats) you need to make sure you don't correct just for the sweet spot and leave other seats worse. It is a balancing act and judgment call that will leave those sitting in the sweet spot without the best possible sound, but won't sound as bad as it could in the other seats. The stereo zone had a broad gain centered at 255 Hz that we pulled down a little with a filter. A 28 Hz 12db/octave high pass filter was also used for the stereo zone.
All processing is done at 64-bits and then dithered to the maximum bit-depth of the DAC. In this case it is 32-bits. This means that volume control is complete transparent until it is too quiet to hear.
JRiver can be controlled multiple ways. I had my laptop in the room and had it setup as a client for the server. I could setup and change the playlist from it. I had a Logitech K830 keyboard on hand. It is the best theater keyboard I've used. It has illuminated keys for a dark room, but you can also turn off the illumination. Most of the control was done using the Gizmo, Eos, or JRemote apps. Both Jeff and I had these on our phone and would add music or concerts to the playlist, skip songs, etc. The apps, laptop, or keyboard could all control the volume.
- I brought my own MOTU 1248. It has dual 8-channel ESS Sabre32 DAC chips. However, one chip is only setup to use 4 outputs so there are 12 outputs total. You can use the left and right output on a different DAC chip for no crosstalk. The DAC has DC-coupled balanced outputs. It has a Thunderbolt connection, but that is currently only supported on MAC. I use the asynchronous USB connection which supports up to 64 channels in/out with the MOTU drivers. Using 2 or 7 channels is such a small part of the bandwidth capability that it is impossible to have any audio related issues when properly configured. The SNR is rated at -123 dB. However, this noise is at 192 kHz which is the maximum sample rate. Within the audible band, the noise floor is around -140 dB at its highest point of 20 kHz. As you go down the frequency spectrum to DC, the noise floor continues to diminish. The key thing benefit of the DAC, which is often overlooked, is that it can provide +20 dBu (7.75 V) of output. Having a high output voltage lowers the noise floor of the entire signal chain and allows one to use lower gain amps - like the Maraschino Cherry amps.
I used my own King 60V Desktop King Maraschino amps for the L/R and Tommy of Digital Amp Company sent me some of the new hanging Maraschino amps for the Center, Left Surround, and Right Surround. These are all connected to the MOTU with balanced cables. I was going to bring my big Cherries, but these are lighter, easier to place in such a small room, have tighter bass when used with fullrange speakers. They are also lower gain which requires more input voltage, but can lead to an overall lower noise floor. The Maraschino provides constant voltage to any impedance, has a super low output impedance, and can handle lots of current. They are very smooth and detailed with massive dynamics. The Maraschino can supply 400 watts continuous at 4 ohms.
Torus Power RM20 - I own this and two other Torus Power RM2.5's. This provides constant power for the amps and subwoofers. It is capable of delivering 100 amps for 10 seconds and 200 amps for 1 second and 400 amps for 1/2 cycle. This eliminates the hotel electrical fluctuations from causing any issues. It also enables the Maraschino Cherry's to be capable of some incredible dynamics.
The speakers used were five JTR Noesis 210RT. These are a 3-way speaker with horn loading down to 400 Hz. Two 10" woofers handle below 400 Hz. They have a spec'd frequency response of 38 Hz -24 kHz, but were flat to below 20 Hz at RMAF. Jeff specs all his frequency responses in free air unlike other companies that include room gain. They have a 95 dB 1W/1M sensitivity and can handle 2000 watts RMS. Jeff designs his own cabinets and uses 24 mm, 18 ply, void free Baltic birch for these which is cut on a CNC machine.
Jeff brought two Captivator 1400's. These have an actual third party verified frequency response of +/- 1dB from 16-200 Hz. Using two subwoofers smoothed the bass response and lowered distortion even further. It also increased maximum output.
Room treatments or the room itself are the last thing the reflected sound hits before your ears. We had a total of 13 "bass" traps in the room. I say "bass", but they are really broadband traps
. All the room treatments are owned by me.
The projector was a DLA-RS67U supplied by JVC. I calibrated the gamma, greyscale, and color and then created a 3D LUT file to use in JRiver. A 3D LUT file changes the output from the HTPC so that when the projector incorrectly changes the final output it is closer to being correct. It is similar to adding a frequency dip to the digital audio signal so that when the room creates the peak at the same frequency it will be closer to correct. The projector was almost completely inaudible at low power mode. I had it at high power mode some of the time. While it seemed loud to me when no media was playing, as soon as media was playing you couldn't hear it.
The screen was a Seymour Screen Excellence Enlightor-4K with the Series-3 fixed frame. Since we were playing mostly 16:9 concert Blu-rays, we used a 126" diagonal 16:9 screen. The screen came with some T-stands to raise it about 23 inches off the floor. I added a 4' piece of aluminum u-tract to each side that went to the ceiling. Attached to the u-track was a 152" piece of aluminum angle that went from one side of the room to the other. I hung three panels of black Seymour Millibell fabric from the 152" aluminum using velcro. The blacked out the sides and top. One the bottom of the screen I stretched a piece of velvet lycra to black out the bottom. The velvet extended about 3' into the room on the floor.
Interesting facts about the room:
Shortest speaker cables
- The speaker cables were 6"-18" long . These let the amp be located behind the speaker and keep the impedance low from the amp to the speaker.
Smallest gauge speaker wire
- We used 16 gauge wire for some channels. At 12" this has the same voltage drop as 16' of 4 gauge wire or 4' of 10 gauge wire. Nobody else at the show probably had either wire this small of gauge or with this low of voltage drop.
-The distance from source to left surround was about 60'.
- I have an Omnimic that is SPL calibrated with a Galaxy SPL Calibrator. I hooked it up for some songs in the room. When Tyson and Pez from Audiocircle were in the room we hit peaks of 129.8 dB Z-Weighted and still had 7 dB of gain left in the tank. This is from 4 meters from the front speakers! We later hit 133 dB. At these levels the sound remains crystal clear with no distortion or compression.
Most Speakers in Use
- The Martin Logan room had four speakers - we had five.
Only room capable of output flat to DC
- Not only is the DAC DC Coupled, but the Maraschino amp is too for flat frequency response to 0 Hz.
Fewest Visible Cables
- At a show where many like to show off cables this probably seems like a strange fact - especially due to the number of speakers, subs, and amps we were using in the room (seven). We had an 8 channel Mogami snake on the right side of the room and a single Mogami Gold interconnect visible on the left side of the room when seated in one of the chairs. That is it.
On the first day the DAC kept loosing its connection to the HTPC. It only took a few seconds to refresh the DAC's mixer in a browser window or redo the USB connection, but it is embarrassing to have problems. It turned out that both the HTPC and DAC were connected to my Torus Power RM2.5 which puts out 2.5 amps continuously. My son had connected things and I hadn't double checked his work. The maximum requirement of the DAC is .5 amps and it is plugged into the Torus at home. The maximum requirement of the HTPC power supply is 13 amps and it is plugged into the wall at home. As soon as I plugged the HTPC into the wall at RMAF, the problem went away. The DAC was experiencing a drop in power that was enough to lose the connection, but not enough to shut it down.
The second problem happened twice on the last day. The HTPC either froze up or rebooted. Both times were when inserting a CD from an attendee. We had played a Rush Blu-ray other Blu-rays directly from the disc with no issue, but it had the problem with the CD. This one was a little more complicated and I didn't figure it out until after the show. I have both JRiver Media Center V20 and V21 installed on my HTPC since I sometimes have to do testing on V20 to help someone out. V20 was still set as the default media player in Windows for a few file types. When the CD's were inserted, V20 was being launched. It attempted to start playback at a different sample rate on the audio device that what was currently being used by V21. A pro audio audio device, or any audio device for that matter, can only play back one sample rate at a time. Attemps to use multiple sample rates were causing the audio device driver to crash the HTPC.