Home Theater Forum and Systems banner

21 - 27 of 27 Posts

·
Premium Member
Joined
·
12 Posts
Discussion Starter #21
Is it muddy sound or just low volume?

If it's low volume
Another thing to consider is that Audyssey may have reduced the level of your center speaker compared to the other speakers in your system. Wayne's point about running Audyssey from just one listening position and moving the mic only slightly has some merit. I have an older Denon 4311ci and I do find the center channel's volume is low after running Audyssey. If I break out my SPL meter my fronts tend to be in and around 75dB and my center is 73dB from my main seating position. Going around the speakers and bumping up/down the channel levels makes a huge difference.

Thanks for your interest in my garbled vocal sound problem from my center speaker. I'm very confident the issue is not low volume. In fact, increasing the volume results in more distortion. However, once this issue is resolved, I will use my RadioShack SPL meter to verify the center channel level is the same as the other channels.

If it's muddy sound:
The 2D graphs don't take in to account the time domain, ie: reverberation or transient decay time (RT60). Looking at the pictures of the room there is a lot of absorbers on your front wall but it's hard to tell how thick they are. So I have lots of questions.
How thick are the absorbers and what material are they made of?
Do you also have them on the first reflection points on your side walls?
What other room treatments do you have?
Is your room in your basement?
If so:
Do you have a subfloor with insulation or is it carpet with underpad over concrete?
Are your walls stuffed with insulation from floor to ceiling?

What I'm thinking is that your RT60 over the frequency spectrum may be uneven. High at some frequencies and low at others. You might also have reflected sound reaching your ears from first or second reflection points (but not at all frequencies) smearing the sound. If you do a waterfall graph in REW it will give you a better understanding.
I appreciate your interest in the acoustic treatment in my home theater.

It is located on the second floor of our home. The walls and ceiling are 5/8" drywall, and the cavities between the studs are filled with fiberglass. There are no windows, and I had the original hollow-core doors replaced with solid-core doors with weather tight seals. The wooden floor is covered with extra thick wall to wall carpet and a thick carpet pad.

All of the panels are made by GIK Acoustics; they don't make public the exact material they use in their products, but I wouldn't be surprised if it is similar to Owens Corning 703. Other than the corner bass traps, each panel is 2" thick and custom framed with wood trim. By design, the wood trim moves each panel an additional 2" from the wall on which it is mounted (thus extending the absorption to lower frequencies). If you look at the independent test data on the GIK website, you will see the absorption of these panels is relatively uniform from about 2kHz and up.

Working closely with the folks at GIK, I have, on the front wall, 5 of the GIK panels. In the corners of the front of the room, there are floor-to-ceiling GIK Tri-Trap bass absorbers.

Before I removed them a few days ago, there was a panel on both of the side walls and the ceiling, between the speakers and the PLP. As you know, those panels were primarily for absorbing the first reflections from the speakers and the walls.

Across the back wall were 3 panels of the GIK panels that were framed with wood trim to move them 10" away from the wall and thereby increase their bass absorption.

I was also concerned that my acoustic panels may have resulted in the excessive absorption of the high frequency range of the audio. So, I have removed all of the panels, other than those on the front wall. Unfortunately, there was no impact on the high frequency roll off or the distorted vocal reproduction.

Please let me know if you have further questions about the acoustic treatment of my room; I find the subject fascinating!
 

·
Premium Member
Joined
·
12 Posts
Discussion Starter #22
I think I found the cause of my high-frequency response problem!

As I previously posted, my next step in trying to solve this mystery of the missing high frequencies was to substitute a separate amp for the center channel amp in my Denon AVR. To begin to make this swap, I went into the closet in my home theater where all of my equipment is located. I found the center channel speaker wire and took it off the Denon CC speaker binding posts.

To clear the path for the speaker wire to the substitute amp, I noticed that during my most recent installation I had coiled the excess speaker wire (about 20 feet) into a neat, small circular loop. The many turns of the loop were held together tightly in several places with cable-ties.

Seeing this configuration, and from the far distant past, I remembered something from my Electrical Engineering education. If you coil a wire into closely held multiple loops, at some range of AC frequencies, the coil can act like an inductor (i.e., a “choke;” an impedance that opposes the flow of high-frequency AC current-- the higher the frequency, the higher the impedance). Hoping this was the source of my problem (actually, grasping at straws!) I quickly cut the cable ties and let the speaker cable loose from its coiled configuration.

Next, I hooked the loose speaker wire to the Rotel substitute amp and turned everything on.

After performing an REW sweep, I knew I was on to the problem.

For the sake of comparison, here is an earlier scan with the coiled speaker wire and Audyssey Off & ON:

NEW CENTER  AUDYSSEY ON & OFF 4_17_2016.jpg

Here is a scan of the center channel without the coil and Audyssey Off:

Tue Cnt Spk Horiz Mic Aud Off 4_26_2014.jpg

Feeling confident, for the first time in many days that my system was working properly, I did another Audyssey calibration. Here is a scan showing the frequency response with the Audyssey turned On:

Tue Cnt Spk Horiz Mic 4_26_2016.jpg

Most importantly, I played the Blu-ray video that had the badly distorted vocal-audio, and found the distortion in the vocals was gone or at least 90 percent better (since this is a new center speaker and a new AVR, I have to gain some more experience to know what to expect). The speech reproduction was now clear and easy to understand.

So, to sum up this misadventure, it was my compulsive behavior that resulted in wasting many hours.

Lessons learned: 1. Don’t be so compulsive about the appearance of wire that no one will see; 2. Audyssey is not “plug-in-play.” You need to perform an REW scan before and after the application of Audyssey calibration; 3. Trust your ears – if something doesn’t sound right, it probably isn’t.

Next steps: I am still troubled by Audyssey applying nearly 6dB of gain in some of the frequency bands. So, I am going to compare the audio response (especially the distortion) with Audyssey On, and 1.with the substitute Rotel amp and 2. With the Denon internal center channel amp.

I would appreciate hearing any comments and suggestions.
 

Attachments

·
Banned
Joined
·
4,838 Posts
Seeing this configuration, and from the far distant past, I remembered something from my Electrical Engineering education. If you coil a wire into closely held multiple loops, at some range of AC frequencies, the coil can act like an inductor (i.e., a “choke;” an impedance that opposes the flow of high-frequency AC current-- the higher the frequency, the higher the impedance). Hoping this was the source of my problem (actually, grasping at straws!) I quickly cut the cable ties and let the speaker cable loose from its coiled configuration.
Not arguing with your results, but your coil is a real inductive coil with a single-conductor wire. With speaker wire, two conductors are packaged together side by side, and the "coil/inductor" effect is negated. It cancels out. That's the theory anyway. What type of cable have you used?

Lessons learned: 1. Don’t be so compulsive about the appearance of wire that no one will see; 2. Audyssey is not “plug-in-play.” You need to perform an REW scan before and after the application of Audyssey calibration; 3. Trust your ears – if something doesn’t sound right, it probably isn’t.
All true.

Next steps: I am still troubled by Audyssey applying nearly 6dB of gain in some of the frequency bands. So, I am going to compare the audio response (especially the distortion) with Audyssey On, and 1.with the substitute Rotel amp and 2. With the Denon internal center channel amp.

I would appreciate hearing any comments and suggestions.
A 6 dB of boost at mid or high frequencies creates an opportunity for boost if those frequencies are present in the program material. Usually, that material will account for a small percentage of the total power, so increasing that band of frequencies 6 dB ends up increasing total power by a fraction of that amount. To play it safe, though, go ahead and be careful, just not quite as conservatively as you have.

I still think that the mic calibration pattern could be troublesome. If you are happy, fantastic! Next time you run a calibration, try this mic pattern, in part two of post #1. It is better at ignoring the bounce off of a chair back that can lead to the dip that has been bothering you.

Not suggesting you do all the work over, if you are happy you are happy. Just something to think about for the future.
 

·
Premium Member
Joined
·
12 Posts
Discussion Starter #24
Thanks for your comments and suggestion.

Not arguing with your results, but your coil is a real inductive coil with a single-conductor wire. With speaker wire, two conductors are packaged together side by side, and the "coil/inductor" effect is negated. It cancels out. That's the theory anyway. What type of cable have you used?


I still think that the mic calibration pattern could be troublesome. If you are happy, fantastic! Next time you run a calibration, try this mic pattern, in part two of post #1. It is better at ignoring the bounce off of a chair back that can lead to the dip that has been bothering you.

Not suggesting you do all the work over, if you are happy you are happy. Just something to think about for the future.
SPEAKER WIRE ISSUE:

For speaker cable I am using simple, generic, 12 AWG, copper stranded wire. This choice is not due to cost, but the careful consideration of the effectiveness of more costly alternatives.

When I recently replaced the center speaker, I also replaced the center speaker cable. To feed the cable through the small opening into the equipment room, I had to separate the two conductors (i.e., “unzip” them from each other) and feed the individual conductors into the room, one at a time. So, I had two lengths of single conductor wire inside the equipment room; it was those single conductor wires that I neatly wound into coils. That is why the inductance was not canceled out by an opposing electro-magnetic field in an immediately adjacent wire.

TRIANGULAR/PLANAR MIC POSITIONS:

I took your suggestion and recalibrated Audyssey with the goal of using the mic pattern in part two of your post #1. With the one exception noted below, I tried very carefully to follow your directions for positioning the mic at the eight points you described in a triangular/planar mic pattern. (In addition, I included 2 layers of blanket draped over the chair and headrest.)

However, contrary to your diagram, I purposely did not place my mic tripod on the chair (please see my concern addressed below). Instead, I located my mic stand on the floor, between the back of the chair and the back wall. After elevating the height of the stand well above the head rest of the chair, I rotated the mic-end of the boom toward the front of the room, and downward to about 120-degrees from a fully vertical position. In this orientation, the stand and mic were mechanically and thus sonically isolated from the chair for all eight measurements.

The first measurement was taken with the mic located between where my ears are normally positioned, which is a few inches below the top of the headrest (the Primary Listening Position or PLP). Next, I raised the height of the boom, without changing the approximate 120-degree angle, so the mic was just above the headrest. This was the position for measurement number two.

For measurements three through eight, the mic stand height remained constant, only the length of the boom was increased. I used a ruler to ensure the eighth mic position was 12-inches forward from the first mic position, but was at the same vertical elevation as the first position.

Thus, all of the mic positions were in a vertical and right-triangular plane that was orthogonal to the headrest. The 90-degree vertex of the right triangle was midway between my ears in the PLP. The apex of the triangle was about eight inches above the first mic position. The remaining positions followed an imaginary line (the hypotenuse of the triangle) that connected the apex and a vertex 12 inches in front of, but at the same elevation as my PLP.

Please let me know if I did not follow your mic pattern.

(F/Y/I, when I followed the link in your post, none of the images or scans in your article were visible, even after clicking on them. Fortunately, in one of the responses to your article, your diagram of the triangular/planar mic pattern was reproduced. The diagram made the mic pattern much more comprehensible.)

FR COMPARISON -- TRIANGULAR VS OLD AUDYSSEY:

Here is a graph showing the FR of the center speaker before and after the triangular/planar Audyssey calibration. I have set up this graph so the two scans do not overlap for easier comparison. PLEASE NOTE: The blue trace is with the triangular/planar Audyssey; The red trace is the older calibration (the title of the graph is reversed).

Fri 4_29_2016 new vs old Aud On Overlay.jpg

Comparing the before and after scans, in the FR from 100 Hz to 20 kHz, the before scan is linear plus or minus 6dB. The after scan is linear, in the same frequency range, to plus or minus 4dB. So, that is a nice improvement.

SPEECH INTELLIGIBILITY -- IMPORTANT FREQUENCIES

Here is a chart of the importance of certain frequency bands to the intelligibility of speech (from: http://www.dpamicrophones.com/mic-university/facts-about-speech-intelligibility):


Facts-about-speech-intelligibility-Microphone-University-DPA-Microphones-05.png

With this chart in mind, the new frequency response in the range of 2 kHz to 4.5 kHz seems to be depressed compared to the old response.

This is an overlay of the FR of the two previous scans, but limited to the frequency range of 600Hz to 6kHz. This overlay makes clear the cut in gain, resulting from the triangular/planar calibration from 2kHz to 5kHz, ranging from 0 to a maximum of 9dB at 2.8kHz (the cursor location):

Fri 4_29_2016 new vs Old Vocal Overlay.jpg

It seems the notch I have been trying to eliminate since my first post has reappeared. Albeit subjective, the vocals have a more “hollow” timbre with the new Audyssey calibration

DENNON AVR EQ SETTINGS, BEFORE AND AFTER


Here is a photo of the EQ settings before I ran the most recent Audyssey calibration:

EQ cntr spk pre aud cal (1 of 1).jpg

Here is a photo of the EQ settings after I ran the Audyssey triangular/planar calibration:

EQ cntr spk after aud cal (1 of 1).jpg

Extracting the gain or boost setting from both photos, we can see:

FREQ BEFORE AFTER
63Hz.... +3... +3
125Hz... -4... -4
250Hz... +4... 0
500Hz... +2... 0
1kHz.... +2... 0
2kHz.... -2... -2
4kHz.... +4... +4
8kHz.... +3... +3
16kHz... +3... +2

Of course, the boost and gain settings are just a partial view of the EQ since we have no way of knowing, from the information my Denon AVR provides, what the Q is associated with each setting.

I do have a question regarding the methodology you used in optimizing the mic positions during Audyssey calibration. It appears you made your measurements with the tripod for the mic sitting on the seat of your PLP. Did you consider the possibility of coupling the sound waves from the speaker to the chair, through the tripod, and then to the mic?

Thanks again for your suggestions. Your help, and the help provided by those who have posted replies, has guided me in greatly improving the vocal clarity from my center channel.

Additional comments and ideas from everyone who reads this post would be greatly appreciated.
 

·
Banned
Joined
·
4,838 Posts
Thanks for your comments and suggestion.



SPEAKER WIRE ISSUE:

For speaker cable I am using simple, generic, 12 AWG, copper stranded wire. This choice is not due to cost, but the careful consideration of the effectiveness of more costly alternatives.

When I recently replaced the center speaker, I also replaced the center speaker cable. To feed the cable through the small opening into the equipment room, I had to separate the two conductors (i.e., “unzip” them from each other) and feed the individual conductors into the room, one at a time. So, I had two lengths of single conductor wire inside the equipment room; it was those single conductor wires that I neatly wound into coils. That is why the inductance was not canceled out by an opposing electro-magnetic field in an immediately adjacent wire.

TRIANGULAR/PLANAR MIC POSITIONS:

I took your suggestion and recalibrated Audyssey with the goal of using the mic pattern in part two of your post #1. With the one exception noted below, I tried very carefully to follow your directions for positioning the mic at the eight points you described in a triangular/planar mic pattern. (In addition, I included 2 layers of blanket draped over the chair and headrest.)

However, contrary to your diagram, I purposely did not place my mic tripod on the chair (please see my concern addressed below). Instead, I located my mic stand on the floor, between the back of the chair and the back wall. After elevating the height of the stand well above the head rest of the chair, I rotated the mic-end of the boom toward the front of the room, and downward to about 120-degrees from a fully vertical position. In this orientation, the stand and mic were mechanically and thus sonically isolated from the chair for all eight measurements.

The first measurement was taken with the mic located between where my ears are normally positioned, which is a few inches below the top of the headrest (the Primary Listening Position or PLP). Next, I raised the height of the boom, without changing the approximate 120-degree angle, so the mic was just above the headrest. This was the position for measurement number two.

For measurements three through eight, the mic stand height remained constant, only the length of the boom was increased. I used a ruler to ensure the eighth mic position was 12-inches forward from the first mic position, but was at the same vertical elevation as the first position.

Thus, all of the mic positions were in a vertical and right-triangular plane that was orthogonal to the headrest. The 90-degree vertex of the right triangle was midway between my ears in the PLP. The apex of the triangle was about eight inches above the first mic position. The remaining positions followed an imaginary line (the hypotenuse of the triangle) that connected the apex and a vertex 12 inches in front of, but at the same elevation as my PLP.

Please let me know if I did not follow your mic pattern.

(F/Y/I, when I followed the link in your post, none of the images or scans in your article were visible, even after clicking on them. Fortunately, in one of the responses to your article, your diagram of the triangular/planar mic pattern was reproduced. The diagram made the mic pattern much more comprehensible.)

FR COMPARISON -- TRIANGULAR VS OLD AUDYSSEY:

Here is a graph showing the FR of the center speaker before and after the triangular/planar Audyssey calibration. I have set up this graph so the two scans do not overlap for easier comparison. PLEASE NOTE: The blue trace is with the triangular/planar Audyssey; The red trace is the older calibration (the title of the graph is reversed).

View attachment 120409

Comparing the before and after scans, in the FR from 100 Hz to 20 kHz, the before scan is linear plus or minus 6dB. The after scan is linear, in the same frequency range, to plus or minus 4dB. So, that is a nice improvement.

SPEECH INTELLIGIBILITY -- IMPORTANT FREQUENCIES

Here is a chart of the importance of certain frequency bands to the intelligibility of speech (from: http://www.dpamicrophones.com/mic-university/facts-about-speech-intelligibility):


View attachment 120433

With this chart in mind, the new frequency response in the range of 2 kHz to 4.5 kHz seems to be depressed compared to the old response.

This is an overlay of the FR of the two previous scans, but limited to the frequency range of 600Hz to 6kHz. This overlay makes clear the cut in gain, resulting from the triangular/planar calibration from 2kHz to 5kHz, ranging from 0 to a maximum of 9dB at 2.8kHz (the cursor location):

View attachment 120441

It seems the notch I have been trying to eliminate since my first post has reappeared. Albeit subjective, the vocals have a more “hollow” timbre with the new Audyssey calibration

DENNON AVR EQ SETTINGS, BEFORE AND AFTER


Here is a photo of the EQ settings before I ran the most recent Audyssey calibration:

View attachment 120417

Here is a photo of the EQ settings after I ran the Audyssey triangular/planar calibration:

View attachment 120425

Extracting the gain or boost setting from both photos, we can see:

FREQ BEFORE AFTER
63Hz.... +3... +3
125Hz... -4... -4
250Hz... +4... 0
500Hz... +2... 0
1kHz.... +2... 0
2kHz.... -2... -2
4kHz.... +4... +4
8kHz.... +3... +3
16kHz... +3... +2

Of course, the boost and gain settings are just a partial view of the EQ since we have no way of knowing, from the information my Denon AVR provides, what the Q is associated with each setting.

I do have a question regarding the methodology you used in optimizing the mic positions during Audyssey calibration. It appears you made your measurements with the tripod for the mic sitting on the seat of your PLP. Did you consider the possibility of coupling the sound waves from the speaker to the chair, through the tripod, and then to the mic?

Thanks again for your suggestions. Your help, and the help provided by those who have posted replies, has guided me in greatly improving the vocal clarity from my center channel.

Additional comments and ideas from everyone who reads this post would be greatly appreciated.
First, I appreciate the detail of your posts, it is much easier to try to help someone who communicates those details so clearly.

Second, the attempt to follow my most recently suggested mic setup pattern has given the opposite of the result I hoped it would in the 2 kHz range. All I can say is...:dontknow: (that's the shrug that our teenagers often give us when we want an explanation, along with a monosyllabic u-u-uuh, their abbreviation for I don't know. Do not, repeat DO NOT try that one on your spousal unit.)

Part of the exercise I went through in determining that pattern was to take measurement each of the points of the pattern with REW and see if any of them have a peak (or dip) in the critical 1 to 3 kHz range. A cumulative peak there will lead to REW compensating in the opposite direction. If any of your measurements give a peak in that range, do not use that position. That is my suggestion for determining how that setup pattern might be affecting your result. Also, it is possible that the mic setup pattern is doing exactly what it was intended to and then Audyssey is adding that dip at 2 kHz by its own design.

Also, the pattern is meant to simplify the Audyssey setup process. No critical measurements after the first point, no L or R positions (which tend to only reinforce a peak measurement problem if it exists) and gives the best soundstage and imaging (SS&I) that I have been able to get from Audyssey.

Your point about placing the mic stand on the floor is a good one, next time I am doing work around the chair I will try it out. Generally I do not place the stand on the chair, it was part of the effort to come up with the simplified pattern and an easy way to accomplish it.

Edit; And thanks for the explanation on the coils of wire, now it makes perfect sense.
 
21 - 27 of 27 Posts
Top