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CTXMatrix - Free Ambiophonics Plugin
- Thread starter STC
- Start date
Keith_W
Master Contributor
Hello @STC. I downloaded CTXMatrix Beta 17 and had another go. I paid attention to your note that delays are important, so this time I tried to find an optimal setting with "balanced" delays and gains. This is what I came up with:
Stage 1: Gain -6 Delay 2 samples
Stage 2: Gain -3 Delay 2 samples
Stage 3: Gain -6 Delay 2 samples
Stage 4: Gain -3 Delay 2 samples
The good news is that the tonality is closer to the original, but missing some treble. Adjusting the treble gain makes the treble harsher, but does not actually give "life" and "brilliance" back to music. I think the treble setting is probably too low in the frequency range, i'm not sure.
It's a bit difficult to describe the soundstage widening effect, so i'll draw a diagram.
If you imagine five soloists, this is what I hear with no processing.
This is what uBACCH seems to do. The central instrument stays the same size, but instruments further to the side are stretched out. The tonality is either the same as the original, or very very close.
And this is what I hear with CTXMatrix. The vertical soundstage seems to compress, and all instruments are stretched. A soloist who is pinpoint dead centre in the original sounds stretched and smeared in width.
I am starting to think:
- attempting to optimize this further for a 60deg listening angle is going to be a waste of time. I will need to move my speakers to a 20deg angle and try again.
- dialling this in without measurement is extremely difficult. Surely there is a way to dial this in with measurements?
- I don't know how much more I can help you. I don't know enough about how the algorithm works short of a vague idea that it cancels crosstalk.
Maybe we should chat on the phone. I'll inbox you with my phone no.
Stage 1: Gain -6 Delay 2 samples
Stage 2: Gain -3 Delay 2 samples
Stage 3: Gain -6 Delay 2 samples
Stage 4: Gain -3 Delay 2 samples
The good news is that the tonality is closer to the original, but missing some treble. Adjusting the treble gain makes the treble harsher, but does not actually give "life" and "brilliance" back to music. I think the treble setting is probably too low in the frequency range, i'm not sure.
It's a bit difficult to describe the soundstage widening effect, so i'll draw a diagram.
If you imagine five soloists, this is what I hear with no processing.
This is what uBACCH seems to do. The central instrument stays the same size, but instruments further to the side are stretched out. The tonality is either the same as the original, or very very close.
And this is what I hear with CTXMatrix. The vertical soundstage seems to compress, and all instruments are stretched. A soloist who is pinpoint dead centre in the original sounds stretched and smeared in width.
I am starting to think:
- attempting to optimize this further for a 60deg listening angle is going to be a waste of time. I will need to move my speakers to a 20deg angle and try again.
- dialling this in without measurement is extremely difficult. Surely there is a way to dial this in with measurements?
- I don't know how much more I can help you. I don't know enough about how the algorithm works short of a vague idea that it cancels crosstalk.
Maybe we should chat on the phone. I'll inbox you with my phone no.
- Thread Starter
- #43
Thanks Keith for sharing the violin illustration! The image spread evenly looks pretty good at 60 degrees for CTXMatrix.
I ran a quick test with my $10 PC speakers with 60 degrees and got a delay of about 30 to 40 samples with an attenuation of roughly 3.5 to 4 dB for 60 degrees. Your 2-sample delay doesn’t quite cut it for matching the inverted signal, which probably explains why the image looks a bit smeared.
Even my main speakers, which are right next to each other,
Here’s what I measured:
• -2.5 dB at 8 samples
• -3.7 dB at 10 samples
• -3.2 dB at 9 samples
• -2.4 dB at 8 samples
(this one works best for me)
I also tried settings like -1.5 dB at 3 samples which works, but you can definitely hear the difference between an effect and actual cancellation. I’d suggest testing with human speech since our ears pick up on those changes really well. Playing around with 3 to 4 dB and 30 to 45 samples should do the trick. THe actual delay should be around 150 μs to 200 μs but my samples is dependent on the source or your system sampling rate. it was designed to work up to 384kHz .
- Thread Starter
- #44
Here is what you can expect with CTXmatrix compared to BACCH4Mac.
Some insights on BACCH4Mac based on Tom Martin’s detailed review in The Absolute Sound (full article here: https://www.theabsolutesound.com/ar...ied-physics-bacch4mac-stereo-purifier-review/).
To illustrate the difference, here’s a relevant quote from the review regarding Bob Dylan’s The Freewheelin’ Bob Dylan (1963):
“With BACCH, you hear Bob in the center where you would kind of expect him if you think about how most stage performances are arranged, and then the recording engineers put his guitar on the right and the harmonica on the left. That isn’t how it would sound live, but this is a studio recording and you hear how the engineers placed things so that it sounds a bit like a trio. Apart from the deviation between studio and live, what’s impressive is the guitar occupies a space that extends outside of the right speaker and feels appropriately sized for the dreadnought Gibson guitar that Bob played in this period.”
In comparison, with CTXMatrix, my observations on the same recording are more constrained: the guitar is positioned on the right but extends less than 30 degrees from center; Dylan’s voice is not precisely centered but slightly offset toward the left, maybe 5 degrees; and the harmonica reaches roughly 45 degrees to the left. ( Blowin’ in the Wind - Apple Music Hirez streaming)
Another example from the review involves Art Blakey and the Jazz Messengers’ Buhaina’s Delight (1961):
“On Art Blakey and the Jazz Messenger’s album Buhaina’s Delight, the players are arranged in a 270° arc around the listening position that may be effectively where the microphones were. However, I have to say it’s a little bit odd to hear Art Blakey playing in a position slightly behind where I’m sitting, and on the right side. There is a horn off my left side. The other players are arrayed as you would typically hear on stereo between the speakers. Not what you would hear in a club. This studio recording is from 1961 and I just don’t think stereo recording in the studio was evolved to the point where the engineers were trying to do this. I think the engineers wanted Blakey right front so they pan-potted him hard right and the data on the recording has this placed at the right rear. I got similar results with Dave Brubeck’s Time Out, from 1959. But Bill Frissell’s Valentine, a jazz trio studio recording from 2020, sounds phenomenal in the sense that the performers are where you would expect them.”
With CTXMatrix on the same Blakey album, the soundstage remains far more limited: the most extreme left placement trumpet reaches about 40 degrees to the my left,; a similar instruments appears at roughly 30 degrees to the right; and the piano stays centered maybe slight left. It moves abit. Drums is to the right. In short maybe a 70 to 80 degrees angle to the listeners. In short, CTXMatrix does not achieve a 270-degree arc or placements behind the listener. Listening to Take Five from the Time Out album. Drums at about 15 more to the my left but hit hat smears from to centre and right forward ( decaying) occasionally. PIano is to my right. The sax is centre slightly off centre toward my left. The right side remains very much with 10 to 30 degrees only. Nothing goes outside the imaginary 60 degrees unless you push the volume up and some reverbs extends more. This is from CD.
But the question is should it? Is that correct? Can CTXMatrix achieve the so called 270 degrees? Users can play with the delay and cancellation to find out. And accept the limitation of CTX. It cannot do miracles. It is just a crosstalk cancellation plugin.
Some insights on BACCH4Mac based on Tom Martin’s detailed review in The Absolute Sound (full article here: https://www.theabsolutesound.com/ar...ied-physics-bacch4mac-stereo-purifier-review/).
To illustrate the difference, here’s a relevant quote from the review regarding Bob Dylan’s The Freewheelin’ Bob Dylan (1963):
“With BACCH, you hear Bob in the center where you would kind of expect him if you think about how most stage performances are arranged, and then the recording engineers put his guitar on the right and the harmonica on the left. That isn’t how it would sound live, but this is a studio recording and you hear how the engineers placed things so that it sounds a bit like a trio. Apart from the deviation between studio and live, what’s impressive is the guitar occupies a space that extends outside of the right speaker and feels appropriately sized for the dreadnought Gibson guitar that Bob played in this period.”
In comparison, with CTXMatrix, my observations on the same recording are more constrained: the guitar is positioned on the right but extends less than 30 degrees from center; Dylan’s voice is not precisely centered but slightly offset toward the left, maybe 5 degrees; and the harmonica reaches roughly 45 degrees to the left. ( Blowin’ in the Wind - Apple Music Hirez streaming)
Another example from the review involves Art Blakey and the Jazz Messengers’ Buhaina’s Delight (1961):
“On Art Blakey and the Jazz Messenger’s album Buhaina’s Delight, the players are arranged in a 270° arc around the listening position that may be effectively where the microphones were. However, I have to say it’s a little bit odd to hear Art Blakey playing in a position slightly behind where I’m sitting, and on the right side. There is a horn off my left side. The other players are arrayed as you would typically hear on stereo between the speakers. Not what you would hear in a club. This studio recording is from 1961 and I just don’t think stereo recording in the studio was evolved to the point where the engineers were trying to do this. I think the engineers wanted Blakey right front so they pan-potted him hard right and the data on the recording has this placed at the right rear. I got similar results with Dave Brubeck’s Time Out, from 1959. But Bill Frissell’s Valentine, a jazz trio studio recording from 2020, sounds phenomenal in the sense that the performers are where you would expect them.”
With CTXMatrix on the same Blakey album, the soundstage remains far more limited: the most extreme left placement trumpet reaches about 40 degrees to the my left,; a similar instruments appears at roughly 30 degrees to the right; and the piano stays centered maybe slight left. It moves abit. Drums is to the right. In short maybe a 70 to 80 degrees angle to the listeners. In short, CTXMatrix does not achieve a 270-degree arc or placements behind the listener. Listening to Take Five from the Time Out album. Drums at about 15 more to the my left but hit hat smears from to centre and right forward ( decaying) occasionally. PIano is to my right. The sax is centre slightly off centre toward my left. The right side remains very much with 10 to 30 degrees only. Nothing goes outside the imaginary 60 degrees unless you push the volume up and some reverbs extends more. This is from CD.
But the question is should it? Is that correct? Can CTXMatrix achieve the so called 270 degrees? Users can play with the delay and cancellation to find out. And accept the limitation of CTX. It cannot do miracles. It is just a crosstalk cancellation plugin.
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