How to set up an M104 environmental equalizer

act1292

New Member
I inherited a pair of XR7 speakers that came along with the M104 environmental equalizer. I have been trying to get the system set up and am not sure what the procedure is for tuning the equalizer. Anyone here have any experience setting up the equalizer? More specifically:

1) Should I take my frequency response measurements with the equalizer mode set to "In" or "Out"

2) How do I set the low frequency compensation?

I have been thinking that I use the following procedure:

1) Remove all filter capacitors and set the response to "Flat" for all filters.

2) Take measurements for low frequencies and then adjust the low frequency compensation till I get a fairly flat low frequency response 20-250khz

3) Take frequency response measurements at various listening positions

4) Compute the desired filters and install proper caps to obtain a flat response.

Does this sound like a reasonable procedure for setting this up?


Thanks in advance
 
I think the low frequency compensation is always on.....

I always measured from the primary listening location.

With 7s I would expect complex issues in the 80 to 200 hz range, not uncommon to interact 3 filters together to correct these standing wave issues. Lots of low frequency energy out of these speakers can really excite the room.

What are you measuring with?

I think I posted 6s in a client's LR a few years ago.
 
When you say "the low frequency compensation is always on...", do you mean that it is always on even with the equalizer mode set to "Out"?

What I am not sure of is whether I should set the low frequency compensation prior to picking my filters or is that something that is set afterwards.

I am using a Phonic PAA3 Audio Analyzer for making the measurements. I am measuring at different listening positions and taking the average to set up my filters.
 
I would check out this site for Mac white papers, I believe there is one for the theory about the use of the MQ 102 and 101 versus the placement of the speaker. If the speaker is up against a wall but not in a corner then set the switch on 3. Then use your analyzer to examine the over all response. Check the bottom octave and see if it is balanced with the 1K octave. and correct accordingly. Then use the filters to shape the areas in between 1k and 40 HZ. Don't worry about narrow smaller peaks at first, get the general shape as flat as possible with 3 filters and save the 4th for the most prominent narrow 1/3 octave peak. Do not try to correct for dips or valleys. They can be nulls and or resonances in the room absorbing energy from the speaker and you cannot correct those with out adding distortion and possible damage to your system.
 
Thanks twiiii. I went back to the Roger Russell site and re-read his writeups on the M101, 102, and 104 equalizers. Indeed it states there how to first set the low frequency compensation based on speaker placement.

I will set those and go back and make my measurements.
 
Another question regarding setting this up. When using the PAA3 audio analyzer to take measurements, should I use the Flat weighting or should I be using A or C weighting? My thinking is that I should use flat weighting but I could imagine the argument that the A weighting should be used since it mimics the capabilities of the human ear.

Any thoughts on this?
 
The XR series of speakers were developed in conjunction with the MQ 104 AND AA2 analyser. I do not believe it used any weighting. Posted in Mac tech sticky is a copy of he posting sheet we used as well as a filter chart. I had a particular keen eared XR7 owner back back in the day and Sid Coderman played math prof and taught me the formulas to create custom extra narrow sloped filters.....lost somewhere , most likely with the notebook with the hundreds of rooms/ speakers I measured back in the day.

If you do not have a PG equipped amp, and bunches of power, be careful with the bass boost, you will take out the mid domes in the blink of an eye of amp clipping. Being that the XR series were designed with this EQ they do have enough "headroom" in the range covered by the 2 12s and the 8 inch drivers. Do NOT boost mids or treble coverd by the mid dome and tweeters.

This process was extremely important to Gordon Gow (2nd only to turntable setup) and we talked often in the evening when I would come across a strange, therefore interesting room/speaker aberration.
 
Last edited:
Thanks c_dk,

I am running it with a MC2500 amp so I have power guard and plenty of power to drive these speakers. Regarding the mid-dome & tweeter boost, are you referring to everything above 1.4kHz crossover or everything above the 250Hz crossover?

Thanks again as this is a learning process for me.
 
Speakers systems are not measured using any weighting....Weighting=OFF.

A weighting is a curve for measuring environmental noise levels with regards to human hearing......
 
Too many XR7s were paired up with underpowered non PG amps. It was not uncommon to find one of the mid domes with issues. You said you inherited them.....what amp was driving them before?

The kit that came with the MQ104 limited the center frequencies to a max of 1k HZ.

I never cared what the response was throughout the room.....prime listening spot of the owner was my priority.
 
I inherited the whole system from my father and included C31V A/V preamp, the MC2500 amp, the environmental equalizer and the speakers. They are all in good working order. My brother had it checked out by Audio Solutions in Indy about 5 years ago prior to installation in my fathers house and all components are in good working order.

The only thing I am missing is the capacitor set for the equalizer as we couldn't find it when going through the estate. Once I have my filters chosen I will have to purchase the caps individually. I just want to make sure I stay within the range it was designed for so as not to damage any of the components. From the frequency programming table, it looks like I should keep my filters below the 1.4 kHz crossover and that should avoid damaging any of the midrange and tweeters.

Thanks for all the help
 
If you post your measured curves with the old school charting paper( only because I've been looking at them for 37 years) I can help you with the values....
 
I have attached a .png of a plot of the frequency response. The y-axis is in db while the x-axis is the frequency. It is a logarithmic plot so each data point corresponds to an octave. One curve is an average of the response I took from various positions within the room. The other is from the sweet spot - which is what I think I ought to tune it to since that's where I will spend most of my time

Thanks for your help on this.
 

Attachments

  • FreqResponse.png
    FreqResponse.png
    61.1 KB · Views: 11
Thanks for the feedback. I have retaken the data with each speaker independently. Again the average is taken from various points in the room while the other plot is the sweet spot. Each speaker measurement was taken with the other speaker disconnected.

All the equalizer settings on the preamp were set to flat as well as the loudness. The low frequency compensation of the M104 was set to 3 based on the speakers being near the wall but not in the corners.

I appreciate your help and patience on this.
 

Attachments

  • Right Speaker.png
    Right Speaker.png
    59.3 KB · Views: 10
  • Left Speaker.png
    Left Speaker.png
    57.8 KB · Views: 9
Rh speaker: pull down at 50 and 250 put a filter at 125 to lift when it ispulled down by other 2. Save last filter to push up 500 slightly.

Lh speaker: push up 125 as you pull down 200. You will probably need to pull down 50 and push up 500.

I think Skizo posted cap values in the Mac tech sticky.
 
I have a couple of kits here(not for sale) the list is quantity-value......

2-4.7, 2-2.2, 6-1.0, 2-.82, 6-.56, 4-.39, 2-.27, 6-.22, 4-.18, 8-.12, 4-.082, 8-.056, 4-.039, 8-.022, 4-.018, 6-.012, 4-.0082.

This kit was my "on the road kit" back in the day when I was setting these up a couple three times a month. When doing a client's new home their kit was usually lost in the move....
 
Just placed my order for capacitors. Won't be here till Thursday at the earliest. I'll keep you posted how it turns out.

Thanks for all your help on this.
 
Back
Top Bottom