I had a great time a Vince's house. He has a beautiful house and theater. He has a ranch house with no basement so the theater is on the main floor and integrates nicely off the living room and kitchen. The equipment room is on the left of the hallway right before going up several steps to enter at riser level.
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Precisely what did he do?
There are four major parts of the audio calibration process with many small steps. The major parts are Evaluation, Verification, Design, and Calibration. Here is a summary of some of the steps.
- I listen to my own playlist before doing any changes, at the end of the calibration session, and after all major adjustments
- Source components, processor, and speakers are all checked for proper settings and correct connections. I've had people send stereo out of their DVD player and upmix at the processor.
- I use an oscilloscope on the output of the processor to see what bass management is doing and to make sure it won't clip. On the Marantz 8801, it would clip at -7 dB if the subwoofer trim was set to 0 dB. I lower the subwoofer trim to -7 dB and test for no clipping with real content. I also set the amps to not clip with the maximum real life signal. I was able to increase the headroom of the system by +17 dB! 0 dB on the Marantz volume control is actually -10 dB Reference Level after calibration
Processor DSP testing
- I also test what various settings do if I don't already know. On the Marantz 8801, the LFE + Mains is a subwoofer setting. If the mains are set to large, it copies the mains to the subwoofer. There is no way on on any Marantz receiver to route the LFE back to the mains. The Marantz has only 20 ms of overall delay. This makes it difficult to integrate a horn subwoofer properly. The Q of any PEQ filters is also sometimes measured.
- All positions are measured. Mains and center are place properly for a sweet triangle that encompasses the listening area. LCR are moved forward/back if possible to test for SBIR and best integration with sub(s). LR toe in is adjusted. Surrounds are pulled to edge of column.
- all drivers and tweeters are tested for correct phase
Close mic measurements
- All speakers/subs are measured from 1 meter
Listening position measurements
- All speakers/subs are measured from the listening position.
- room noise floor and reverberation are measured, room modes are noted
- I use three class 1 microphones in the listening area to get a dB and power average of the bass response with SMAART V.8 software. Both spectrum and transfer response measurements are taken. Transfer response measurement show the original signal, the out of the processor DSP, and the measured response are 3 locations and the average of the 3 measurements. The transfer response measurements are done with actual content and show the true room response with bass management and how all channels are contributing to the bass.
- subwoofer and center are blended first for the best dialogue intelligibility. This involves level, crossover, delay, and tone adjustments in the processor.
- PEQ and delay are done on my laptop using JRiver for quick testing of multiple settings. This allows me to completely dial in the system and find what is best in a short time. However, one is limited by the system capabilities for final PEQ. For example, the Marantz 8801 has limited EQ capability. I had a new laptop and hadn't loaded Audiolense yet. I use Audiolense in my own system. Audiolense does both time and frequency correction and can easily integrate subs and mains perfectly. When it is installed and licensed, I can test a system with Audiolense, too. I use SMAART to exactly match the subwoofer and main's phase at the crossover region. Depending on setup and available locations, time is spent on optimizing subwoofer placement in the room.
- All channels are calibrated to Reference Level. In the case of Vince's system, 0 dB on the volume control is actually +10 Reference Level.
This calibration was an on-site continuation of some earlier remote calibration using TeamViewer with Vince measuring with Omnimic and making changes as we went along. We made some changes to the subwoofer's own settings. This corrected a huge null at the crossover region and a roll-off of the bass at ~30 Hz. Fixing this helped immensely and gave us a good starting point. Vince's system can be improved with room treatments and outboard DSP. When I pulled down the room modes with narrow Q filters using my MOTU, the bass improvement was fairly high on my scale without much loss of bass energy. Unfortunately, the Marantz processor can't do this by itself.
I have a fairly extensive calibration report that I write up. I haven't done Vince's report yet. He may not even know all the changes I made since he wasn't always in the room. I let owners' comment at their own discretion what changes were made.