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ASC Tube Traps - Listening Room Optimization


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1 hour ago, Chris A said:

So the remaining piece is the "filling up the Haas integral with in-room reflections"--at higher frequencies than ~500-600 Hz.  These can be very early reflections before 5 ms (and after 0.7 ms), or they can be later reflections.  This is the part that I'm curious about, and what the difference in sound in-room is.  And identifying whether the reflections added to the direct arrivals are earlier arrivals or later ones.

 

Chris this is from the QSF application guide pdf I posted in a previous post and if I understand your question correctly I believe it provides the answer you are looking for.

 

Basically I’m creating a room within my room and it gives the ability to control how much and when my room’s acoustics are mixed with the QSF effect. In the below example I’m in effect replacing the Mic with the Listener and the Talent at the opening of the QSF with the sound from the Loudspeakers..

 

miketn

 

 

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18 hours ago, parlophone1 said:

Mike thank you for posting this.

How are you judging the results?

Is some measurement involved in the process? For example, I am thinking of REW that many here use already.

 

 

Your welcome parlophone1… 🙂

 

The results are judged by the most critical and ultimate test.. ie: Listening 👍😄

I will post some examples of how I’m testing the many QSF options for my optimum sound reproduction.

 

Some measurements and listening test help with the initial locations of the Loudspeakers and Listener position options.

 

In my opinion rectangular (unfortunately this room is close to square) rooms are easier to predict and Corner location of Bass Traps have pretty much been proven to be the optimum locations and first areas to install them. ASC’s QSF Concept/Products have been well documented and the techniques for using it has been well established in the professional and home studio fields for decades. The advantage of the QSF Setup is that it is basically creating a high quality room within an existing room and this ultimately just requires you to experiment with arrangement options while listening to determine the optimum setup based on your preferences in sound production or in my case sound reproduction.

 

miketn

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Here are few examples of some of what I’m listening with to assist in the optimization and comparisons of the many QSF Setup Options I have available and hopefully I will describe the listening experiences in a way that can describe the differences experienced in these two QSF examples I will post next.

 

Stereophile Test CD2

Track 1: Channel Identification. (I listen for Vocal Quality and Location/Focus in the imaging.)

 

Track 2: Channel Phasing.  (I listen for Vocal Quality and Central Location when in phase and lack of Focus when out of phase.)

 

Track 3: Acoustic Drum Solo (I listen for Dynamics, Clarity and Imaging in which you can visualize each Drum/Cymbal clearly focused and you should feel like you are in the same space/air where the energy emanating from the drums and flowing to you in a natural time as well as sensing the vibrations in your chair and on your body.

 

Track 15: Pink Noise. (I listen for a well focused central image when in phase with no spectrum colorations as the goal.)

 

Track 16:, Track 17:, Track 18: 1/3rd Octave Warble Tones.

(I listen to these (3) Tracks for even spl balance from band to band and a focused central imaging.)

 

Track 19: Music Articulation Test Tones. (The goal is to have high Articulation through the frequency sweep. This is a very challenging test for any system/room to pass.) Its best to listen on Headphones first to hear what the signal sweep should sound like without the room colorations interference.

 

 

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This CD is a live recording and Vocals, Instruments and Audience Sound and Imaging of them are a good test for me to use.

 

Track 7: Fountain Of Sorrow

Track 8: Your Bright Baby Blues

Track 9: For A Dancer

 

 

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This is an excellent recording especially of Male Vocals and Imaging 

 

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This is an excellent Recording of Female Vocals with a Live audience..

 

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This is a comparison (using the CDs and Bocelli and Clarkson Recordings listed In previous post) of the reproduction experienced with this QSF setup(1) versus the QSF setup(2) in the next post.

 

In this QSF Setup(1):

Stereophile Test CD2:

Track 1: (Fender Precision Bass Guitar and Vocal). The Left, Center and Right are properly located and well focused and forward in the soundstage.

 

Track 2: (Fender Precision Bass Guitar and Vocal).  In-Phase: A forward very well centered and focused imaging  /   Out of Phase: Very Wide Diffuse imaging no center location.

 

Track 3: (Acoustic Drum Solo).   Very Dynamic with each drums pitch discernible and image location of each drum well placed. Image size of the Drum Kit was properly sized and upfront in the soundstage with a good sense of the recording space.

 

Track 15: (Pink Noise).   In-Phase: Had very tight forward imaging.  /   Out of Phase: Imaging was spread well to the sides of the soundstage.

 

Tracks 16, 17, and 18: (1/3rd Octave Warble Tones).   These were reproduced with a forward well centered imaging with only a slight shifting to the right at 50Hz and 40Hz noticed.

 

Track 19: (Music Articulation Test Tones - ie: MATT Test). While still some areas of articulation still need improvement overall this was the best my system has performed this test thanks to the Corner TubeTraps and QSF Setup at the listening chair.

 

 

NEXT: Jackson Browne solo acoustic vol. 1

Track 7: (Fountain Of Youth).    

Vocal: Was centered and upfront and vocal echoes were heard to the right side/back area of the soundstage. Vocals had good clarity but also felt a little bit of an edginess at times with more of an analytical presentation versus the QSF-2 Setup.

 

Piano: Was well focused with good clarity but again it was felt a bit analytical in presentation versus the QSF-2 Setup.

 

Audience: The audience was sensed at the beginning of the track about the width of the diffusers between the speakers about 20ft deep in the soundstage.

 

 

Track 8: (Your Bright Baby Blues).

Vocal: The vocal was Forward and Centered in the Imaging and placed clearly above the guitar with good clarity and dynamic but also a bit of an analytical sound. The Vocal echoes were sensed to the far left and far right of the soundstage at times.

 

Guitar: The instrument had a forward well focused image presentation and a very dynamic sound.

 

Audience: Focused with a slight sense of harshness with a more realistic presentation than Track 7 Audience.

 

 

Track 9: (For A Dancer)

 Vocal:  The Vocal very solid and upfront in the soundstage with good clarity.

 

Piano:  Good clarity with attack, sustain and decay well presented.

 

Audience:  Forward with a bit of a boxed sound.

 

 

Andrea Bocelli and Matteo Bocelli (Fall On Me) recording:

Vocals presented upfront in the soundstage and had good clarity and dynamics but with a slight bit of harshness a few times was experienced. The Piano was focused with good clarity and just an ok sense of location in the soundstage. Strings fill up the soundstage with a great sense of depth with low frequency pressure waves from the drums coming from the back of the stage moving past the listener and pressurizing the room. This is a very dynamic large enveloping recording with soundstage depth feeling of 20ft and width feeling of 20ft. Vocal echoes were clearly heard at the right rear of the soundstage.

 

 

Kelly Clarkson (I’d Rather Go Blind) recording:

Again this is a big sounding recording with audience sounds. The vocal presentation is very focused, dynamic with very good clarity and centered in the soundstage. Vocals are well projected in this recording.

 

 

 

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This is a comparison (using the CDs and Bocelli and Clarkson Recordings listed In a previous post) of the reproduction experienced with this QSF setup(2) versus the QSF setup(1) in the previous post.

 

In this QSF Setup(2)

Stereophile Test CD2:

Track 1: (Fender Precision Bass Guitar and Vocal). The Left, Center and Right are properly located and well focused and forward in the soundstage. The guitar has a better sense of body versus the QSF Setup(1) presentation

 

Track 2: (Fender Precision Bass Guitar and Vocal).  In-Phase: A forward very well centered and focused imaging  /   Out of Phase: Very Wide Diffuse imaging no center location. Again the guitar has a better sense of body versus the QSF Setup(1) presentation.

 

Track 3: (Acoustic Drum Solo).   Very Dynamic with each drums pitch discernible and image location of each drum well placed. Image size of the Drum Kit was properly sized and upfront in the soundstage with a good sense of the recording space. There was more Drum Body perceived with an increased sense of dynamics and impact from the drums versus the QSF Setup(1) presentation.

 

Track 15: (Pink Noise).   In-Phase: Had very tight forward imaging with a little more sense of a better balance at the lower portion of the frequency spectrum.  /   Out of Phase: Imaging was spread well to the sides of the soundstage with again a little more sense of a better balance at the lower portion of the frequency spectrum.

 

Tracks 16, 17, and 18: (1/3rd Octave Warble Tones).   These were reproduced with a forward well centered imaging with only a slight shifting to the right at 50Hz and 40Hz noticed. I would say there was a very slight increase in the L + R shifting from center versus the QSF Setup(1) presentation.

 

Track 19: (Music Articulation Test Tones - ie: MATT Test). While still some areas of articulation still need improvement overall this was the best my system has performed this test thanks to the Corner TubeTraps and QSF Setup at the listening chair. I would rate the QSF Setup(2) equal to the QSF Setup(1) on the test.

 

 

NEXT: Jackson Browne solo acoustic vol. 1

Track 7: (Fountain Of Youth).    

Vocal: Was centered and upfront and vocal echoes were heard to the right side/back area of the soundstage giving a perception of lighting up the soundstage. Vocals had good clarity with more sense of body, air and bloom and simply a more natural presentation versus the QSF Setup(1) presentation.

 

Piano: Was well focused with good clarity but again there was more body more bloom that felt more natural and lights up the soundstage more. The sense of vibrations emanating from the piano out of the soundstage seemed more felt on me and in the listening chair.

 

Audience: The audience was sensed at the beginning of the track as wider with more full/deeper body presentation leading to a more realistic natural presentation versus the QSF Setup(1) presentation.

 

 

Track 8: (Your Bright Baby Blues).

Vocal: The vocal was Forward and Centered in the Imaging and placed clearly above the guitar with good clarity with an increased sense of body and bloom during the dynamic swings of the vocal versus the QSF Setup(1) presentation. The analytical sound of the QSF Setup(1) wasn’t perceived in the QSF Setup(2) presentation. The Vocal echoes were sensed to the far left and far right of the soundstage at times.

 

Guitar: The instrument had a forward well focused image presentation and a very dynamic sound with more body presentation versus QSF Setup(1).

 

Audience: Well focused with more sense of body and natural presentation without the harshness noticed in the QSF Setup(1) presentation.  

 

The overall Image and Soundstage presentation of QSF Setup(2) felt more realistic and as if everything was sharing the same air if that makes sense.

 

 

Track 9: (For A Dancer)

 Vocal:  The Vocal very solid and upfront in the soundstage with good clarity and more sense of body with a more natural presentation versus the QSF Setup(1) presentation.

 

Piano:  Good clarity with attack, sustain and decay well presented with an increased sense of body, presense and naturalness which lights up the soundstage more versus the QSF Setup(1) presentation.

 

Audience:  Forward with more body, realism and presence in the soundstage versus the QSF Setup(1) presentation.

 

 

Andrea Bocelli and Matteo Bocelli (Fall On Me) recording:

Vocals presented upfront in the soundstage and had good clarity and dynamics with more body , bloom and naturalness without the slight harshness of the QSF Setup(1). The Piano was focused with good clarity and increased sense of body with a better sense of location and presence in the soundstage versus the QSF Setup(1) presentation. Strings fill up the soundstage with a great sense of depth sounding more natural with air and bloom compared to the QSF Setup(1) presentation. Low frequency pressure waves from the drums which have more body and bloom in this QSF Setup(2) are still coming from the back of the stage moving past the listener and pressurizing the room. This is a very dynamic large enveloping recording with soundstage depth feeling of 20ft and width feeling of 20ft. Vocal echoes were clearly heard at the right rear of the soundstage.

 

 

Kelly Clarkson (I’d Rather Go Blind) recording:

Again this is a big sounding recording with audience sounds. The vocal presentation is very focused, dynamic with very good clarity and centered in the soundstage. Vocals are well projected in this recording in either QSF setup but I give the edge to the QSF Setup(2) overall presentation but it was surprisingly close.

 

 

Ultimately its very hard to describe in words the differences I experienced between these two QSF Setups but when you can hear it for yourself it was pretty clear that the QSF Setup(2) was simply a more natural and better sounding presentation of these recordings. The QSF Setup(2) Soundstage and Imaging presented the vocals and instruments as if they were sharing the same space and air with their energy emanating from the soundstage to me in a manner that draws me more emotionally into the recordings.

 

 

miketn.

 

 

 

 

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14 hours ago, mikebse2a3 said:

Chris this is from the QSF application guide pdf I posted in a previous post and if I understand your question correctly I believe it provides the answer you are looking for.

 

Basically I’m creating a room within my room and it gives the ability to control how much and when my room’s acoustics are mixed with the QSF effect. In the below example I’m in effect replacing the Mic with the Listener and the Talent at the opening of the QSF with the sound from the Loudspeakers..

 

Believe it or not, the effects that are being described in that excerpt you provided (thanks--that is what I was looking for) pretty much match what I've settled on in my listening room, with some slight exceptions:

 

1) the QSF minimum dead time is quoted as 2 ms (i.e., 27 inches of travel at room temperature), while I've found in my listening room that that dead time needs to be increased to about 2.5-->3 ms (i.e., about 44 inches, minimum offset distance).  This includes the path length of sound being emitted inside the loudspeaker and being directed via the horns to the listener (about an extra 17 inches in the case of the K-402 horn and the compression driver path length). 

 

2) In the case of recording musicians (the original QSF concept), the reflected sound is first emitted near the microphone by the vocalist or instrumentalist, then it travels to the reflective/diffractive surfaces of the tube traps, then it returns back to the microphone--a two-way trip.  In the case of a listener's position in stereo reproduction, it's the direct arrivals from the stereo loudspeakers (in your case) and a 5.1 array in mine --> to a reflection or even diffusion from the tube traps--> then on to the listener. 

 

This means that for stereo reproduction, the minimum distance of the tube traps from the listener's position needs to be increased over that distance found in a sound recording studio with a musician singing or playing into a microphone--because of the geometry of the sound propagation/reflection paths.  I put that minimum distance for home-sized listening rooms to the reflective objects around both the loudspeakers and the listener's position closer to ~40 inches. 

 

3) The tube traps of QSF design are themselves curved-surface diffusers to a degree (by the figure you posted, above, and reproduced below):

 

image.png.701ac43959c4219a3b47704307e44bc0.png

 

The setup in my listening room includes diffusion from the disc racks on the right (starting about 1 kHz in terms of depth of the diffusion), and equipment racks on the left.  The surrounding AMT-1/Belle bass bins provide additional diffusion surfaces at 90 degrees to the on-axis sight line to the center of the stereo loudspeakers/center loudspeaker.  I keep a clear path from the loudspeakers (including center MEH and two corner-located Jubilees) to the listening position, and just enough covering on the floor to control the floor bounce a bit (but not enough absorption to get good REW measurements including phase/group delay, etc.).

 

4) I've found that the minimum and maximum T30 (reverberation times) vs. frequency is dependent on the room volume, with smaller rooms requiring shorter T30 times.  I find that 0.4 second T30 times (measured near the loudspeakers) are about optimal for my size of listening room--which is ~5500 ft3 (156 m3) in volume. 

 

5) The front wall diffusors in your room would be comparable to the brick masonry and elevated center loudspeaker in my array, except that I found empirically that there needs to be more absorption covering the brick masonry on my front wall in order to create a strong phantom center stereo image, along with a row of 2' wide absorption tiles just at the K-402/Jubilee bass bin mouth exits along the side walls.

 

All of these characteristic reflection and diffusor distances are visible in the REW spectrogram plots, including the specular intensity vs. time/distance.

 

Chris

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Mike and Chris,

Very, very informative. Thanks for all the work that both of you have put in to explain so much.

 

I hope you both have all of your writing archived, so it could be posted somewhere if the site got corrupted.

 

Bruce

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