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Measuring Distance to MLP & now REW instructions


USNRET

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Speaking HT here using McIntosh MX151 Room Perfect
Tech support from MC advises critical distance input is very important and that laser instead of tape measure should be used,
I have L/R Khorns and Belle center

Where do you think I should measure from?
As a beginning I tape measured at an angle from MLP to a point on the top hat approx half way between tweeter and mid driver.
Sounds good so far.
In the past I have just measured from center of speaker front.
Thoughts?

If I use my laser where should I put the reflector for a best average distance?
 

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Seriously, laser is preferred over tape measure?  To me, that's just ridiculous.  But regardless, I would think that your MLP is highly dependent on the distance between each of the LCR speakers, and then the possible seating distance from the LCR speakers, and then all of the other's would fall into place after that is decided.  I'm not an HT guy, but that just seems to make sense to me.

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Jim, I am trying to determine a best position to measure from since the drivers / horns create a "non time aligned" position. Mc has advised an 80 inch  addition to sub distance as a starting point as the subs are parallel to KHorn folded horn fronts.

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I was ever so hoping that the MX151 with on board Room Perfect would satisfy my 2 channel pleasure; not so much. It does wonders in HT / 5.2 mode compared to my previous pre-pro using the same Emo amp. Loving that and actually watching movies again.

The McIntosh C2500 > MEN220 Room Perfect > MC 275 puts the MX151 > Emo XPA-5 to shame in 2 channel. I have not tried swapping amps (MX to 275) so that is an unknown.
 

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Mike, a tape measure or laser is of little value.  What you need is acoustical distance which could or could not be the physical distance.  Mc Intosh mention 80 in.  That is a lot.  At 7 ms there will be a 180 phase shift which is slighty under the 80 in. mark.  This is assuming an 80 Hz xo and works out to 6.7 second.  If you use the 80 in. for the sub/bass driver  delay, try lowering the sub/bass driver delay by 2-3 ms two times to see if that brings things together.  What sub are you using?  It is surprising the Room Perfect is good for HT and not 2 ch.  The same numbers should exits for both.  

 

My friend, to help further, you need some measurement gear like Omnimic or REW.  Otherwise it is a lot of trial and error and even then you will have doubts.

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I had to improvise... I began with physical distance from mouth to LP, then I used my ears to make adjustments a 1/2" at a time. It took a long time but sounds good... however I am still not 100% satisfied but I don't have any way of doing it.

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16 minutes ago, Schu said:

I had to improvise... I began with physical distance from mouth to LP, then I used my ears to make adjustments a 1/2" at a time. It took a long time but sounds good... however I am still not 100% satisfied but I don't have any way of doing it.

Measurement is the last horizon.  I hear that you are not 100% satisfied but, you may be there as far as what you can do or willing to do in the room.?  This sounds odd but, for each room and it's level of room tx and correction, etc., there is a " this is it or this is the best".  Any room other than one with perfect dimension, Room Tx, etc. have an end point.  Knowing that will allow one to sleep at night and leave the circus happy having enjoyed the. show.

 

For example, I could put of ceiling room TX, bass traps from floor to ceiling, ect. but, I won't.  This is a sitting room and I am not going to ruin that aspect of the room for more sound refinement and live in a studio setting or an-echoic chamber.  We all need a defined end point on when to leave the circus.

 

Image result for circus train gif

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For me, the manifestation of the lack of satisfaction is based around timing (milliseconds)... sound is good, sound is natural, all timbre is very well matched (center could probably be better with one of the larger heritage) yet there is a weird timing issue going on. At times it seems really perfect as sound arrives at LP at the natural correct time, and any other times there is a weird echo/reverb happening. It may be related to how long it takes the signal to travel to the rear speakers or perhaps its a processing thing with sound movement in 5.1.

 

Some parts of songs are truly elegant and fully enveloping, at other times its annoyingly reverberated.

 

I have not spent a lot of time working on it other that setting the distance, but I am sure a solution is in the AVR somewhere.

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The sound is good but why not attempt better; hence the question.

I have a laptop, REW and mic; just beyond me to use

Subs are a pair of PSA XS30SE only used in 5.2 although the MEN220 gives 2.2 capability

My opinion on the 2 channel vs HT is the different pre-amps but I haven't proven that...yet

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8 hours ago, Schu said:

At times it seems really perfect as sound arrives at LP at the natural correct time, and any other times there is a weird echo/reverb happening. It may be related to how long it takes the signal to travel to the rear speakers or perhaps its a processing thing with sound movement in 5.1

This sounds like a room issue related to comb filtering.

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12 hours ago, USNRET said:

Tech support from MC advises critical distance input is very important and that laser instead of tape measure should be used

Actually, I think that this is part of the problem.  If your loudspeakers' drivers were all exactly the same distance from your ears, then it might make more sense.  They're not, so the best that you can do is to align to either the midrange drivers or the tweeters (since the bass bins are much less sensitive to delay due to the length of the wavelengths produced).  I'd choose the midrange drivers.

 

So I'd recommend measuring however you want to to the front panel of the loudspeakers (i.e., laser or tape measure) as long as you're measuring from the centerline of the midrange horn mouths, but add the differential distances of the midrange horns. 

 

For the Belle, this distance is a little bit shorter than the K-400s in the Khorns.  So you can do the math in your head: the ratio of 400/500 times the K-400 horn length, which equals the relative length of the midrange horns in the Khorns vs. the Belle.  That differential distance is about 1.7 inches (1/4 wavelength horn) putting the Belle's front face that much closer than the Khorns.

 

By the way, that's not very much--and probably not worth the bother since you're probably not sitting exactly on-axis.  Most AVPs/AVRs don't bother with anything less than about 4 inches (0.3 milliseconds at room temperature). 

 

12 hours ago, USNRET said:

Where do you think I should measure from?

 

As a beginning I tape measured at an angle from MLP to a point on the top hat approx half way between tweeter and mid driver...In the past I have just measured from center of speaker front. Thoughts?

If I use my laser where should I put the reflector for a best average distance?

The top hats where the midrange horn mouths are on centerline to the place where your ears are located when sitting in the main listening position.

 

 

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2 hours ago, USNRET said:

I have a laptop, REW and mic; just beyond me to use

As you probably know, this is the best way to align everything using time delays in the room correction device/firmware, since the electronic filters in the sub and the crossovers add delay, too. 

 

If I can be of any assistance in using REW, let me know.

 

Chris

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17 hours ago, Schu said:

For me, the manifestation of the lack of satisfaction is based around timing (milliseconds)... sound is good, sound is natural, all timbre is very well matched (center could probably be better with one of the larger heritage) yet there is a weird timing issue going on. At times it seems really perfect as sound arrives at LP at the natural correct time, and any other times there is a weird echo/reverb happening. It may be related to how long it takes the signal to travel to the rear speakers or perhaps its a processing thing with sound movement in 5.1.

 

Some parts of songs are truly elegant and fully enveloping, at other times its annoyingly reverberated.

 

I have not spent a lot of time working on it other that setting the distance, but I am sure a solution is in the AVR somewhere.

I do not know you or your situation but the description you give sounds VERY much like a room treatment issue.

Some*times* it sounds good and not others, obviously the room isn't changing but the frequencies played are.

 

At some frequencies there is ringing as the frequency lingers too long compared to the others.

 

Waterfall graphs, from REW or otherwise, can show this clearly and easily if you have a measurment mic.

 

 

 

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So REW loaded

ASIO files downloaded and REW lets me select that
Umik calibration file loaded, laptop (Win 8.1 for now) sees mic and it works
all that's left is all the stuff I am clueless about. I have not connected laptop to prepro via HDMI yet (well I have previously just not in attempt to run REW). I did run it once on another laptop and the Marantz and actually got some display of something

and here is where @Chris A shows up at my doorstep....

 

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