[W9TR]

More background info on Room Perfect from Ron Cornelius of McIntosh. It calls out the MX 150 but the 151 is identical in this aspect.

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Room Perfect Microphone Measurement Techniques

The purpose of this brief explanation is to gain a better understanding of how to efficiently calibrate Room Perfect as used in the McIntosh MEN220 room correction system and MX150 A/V Control Center.

STEP ONE is to decide how the speakers are configured in the system.
In the case of MEN220 one may have a simple two speaker stereo system. One may also use a single mono or two stereo subwoofers for 2.1 or 2.2 configurations. If subwoofers are used you will want to enter delay times into MEN220 for the subwoofer(s). Measure the distance to the subwoofers and main speakers, the difference should be added to the subwoofer output delay in MEN220 set up menu. It is also recommended that the subwoofer(s) run with their internal crossovers bypassed and the crossover point is set in the MEN220. LR-4th order crossover slopes are suggested.

When using MX150 the distance measurement from each speaker to the listening seat will need to be put in the set up menu. This is done by measuring with a tape measure and then entering:
Installer Menu-> Speaker and Room Setup-> Speaker Configuration-> Edit/Select Setup at the bottom of menu:

Next step is to enter the size/ crossover points for each speaker. If no speaker is used in a position this must show a – under the right hand size designation window. Room Perfect will throw an ERROR code if a speaker is designated but not connected during the measurement process. Once speakers are decided go to VERIFY CURRENT SETUP and run test tones through all of the speakers. You may use a sound pressure meter to adjust the sub woofer gain control levels to match the mains. All other speaker levels will be automatically set by Room Perfect during the measurement process.

Next go to DISTANCE SETTINGS and enter the distance of each speaker to the primary listening position. For the first Focus Position measurement, an arbitrary position in the area of your main seating area and centered on the video display is fine.

Important, BEFORE STARTING MEASUREMENT PROCESS! Once the Room Perfect measurement process is started it is assumed that the speakers will not be moved from the entered positions. Any time speakers are moved or changed a new full set of measurements will need to be taken.

THE FIRST MEASUREMENT: Both MX150 and MEN220 use a GUIDED measurement system that will prompt the user through the measurement process.

The first measurement is called FOCUS POSITION. This should be with the microphone placed at normal head height and pointed forward to a point centered between the main left right speakers. The McIntosh microphone stand will allow easy positioning of the microphone. A 25 foot long cable is included and more cable may be added for very large rooms.

All measurements are accomplished with two sets of test tones. These are specific 1/12 octave tones which will play in each speaker in two groups. 50 tones are below 350Hz and 71 tones are above covering all 10 octaves of the musical spectrum. Since test tones are used there can be background noise in the room but noise will slow down the measurement process.

MEN220 and MX150 will initially indicate the correct volume setting up or down as needed to achieve 80Db at the microphone. This may be uncomfortably loud to some and a lower volume may be used in some situations. If a lower volume is used all other sounds in the room should be minimized.

After the first FOCUS position measurement is finished the front panel display of MX150/MEN220 will show a ROOM KNOWLEDGE read out in percentage. This may be a number from 20 to 60%. The next series of ROOM MEASUREMENTS will add to the ROOM KNOWLEDGE base after each measurement is taken. The goal is 95 to 100% ROOM KNOWLEDGE.

THE SECOND SERIES of MEASUREMENTS are ROOM POSITION measurements. The microphone placement rules for efficient measurement are:
1-Do not measure behind or within the immediate area of any speaker. Four foot distance or more is preferred. Take measurements in the rear 2/3 of the room when possible.
2-Do not point the microphone directly at any speaker. This is a bit tricky with multi-channel systems where speakers are placed throughout the room.
3-Measurements of the floor, walls, and ceiling yield accurate Room Knowledge.
4-Point the microphone at bookcases, doors, coffee tables, or any large surface while staying back at least two feet. Under tables or behind furniture is allowed as is pointing the microphone at the rear walls.

It may take 5 to 10 measurement positions through the room to gain over 90% ROOM KNOWLEDGE. When this is attained the choice is offered to end or take more measurements. Once ‘Continue- NO’ is selected the correct filter will be created to correct the room. This will take one or two minutes to create.
ADDITIONAL MEASUREMENTS: Up to eight focus positions may be added. These may be labeled in MX150 such as couch, left recliner, desk chair or whatever is appropriate. When a Focus Position is selected the sound will be, well, Focused in that position for maximum imaging, frequency balance and spaciousness. If multiple listeners are in the room the Focus Position may be switched or the GLOBAL Room Perfect setting can be chosen to blend all of the Focus positions such as when watching a movie with a full house of guests.
Room Perfect is a powerful tool that will correct the problems caused by a room’s dimensional effect on the natural sound of a speaker. The implementation of Room Perfect as in MX150 and MEN220 will deliver a startlingly real audio reproduction experience.

Ron Cornelius