I wonder why it didn't quite cope with the 30+ Hz resonance?DIRAC ART ON
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Measure your C50 in REW and tell us how your bass sounds!
- Thread starter Tim Link
- Start date
Keith_W
Master Contributor
The fact it's fairly straight and doesn't decay suggests it's not a resonance. Maybe an 1800rpm computer fan? Fridge compressor? Neighbour mowing the lawn?
But then it would have been the same before the correction?
I forgot where I save the recording of my '97 Ford Explorer purring))
Yep just waiting for AcoustiX release.
Just my old trusty EMX-7150, ARTA, and EKIO.
Full documentation of the system & setup -> http://www.hifi-forum.de/index.php?action=browseT&forum_id=267&thread=1363&postID=82#82
Here are the C50 results for Dirac Bass Control and ART.
The room size is approximately 4 m × 7 m × 2.3 m.
Because I ran the sweep at a fairly high volume, the low-frequency values became a bit strange in the measurement.
With ART enabled, the graph looks normal even at the same sweep volume.
This next one is from a different room, where the sweep volume was normal.
It’s a sloped-ceiling room about 4 m × 4 m × 5 m.
When ART is on, the low frequencies sound as if the walls aren’t even there.
The room size is approximately 4 m × 7 m × 2.3 m.
Because I ran the sweep at a fairly high volume, the low-frequency values became a bit strange in the measurement.
With ART enabled, the graph looks normal even at the same sweep volume.
This next one is from a different room, where the sweep volume was normal.
It’s a sloped-ceiling room about 4 m × 4 m × 5 m.
When ART is on, the low frequencies sound as if the walls aren’t even there.
With ART, it can’t completely eliminate those “reflection-like” areas I circled, but it still sounds incredibly clear.
I used to think the Bass Control low end was very good, but now I can’t go back.
This high-ceiling room has intentionally more reverberation, and I really like the acoustics here.
Added: The green circles were probably high-frequency reflections, so they weren’t related to ART. As for the mid and high frequencies, I feel no further adjustment is necessary.
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audiofooled
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I'm not convinced that this is much useful metric in small rooms. Anyway, here it is:
Headphones, point blank:
Wavelet, 1/24:
L+R+sub, MLP, 3,5m distance:
Wavelet, 1/24:
Vector average:
Wavelet, 1/24:
Phase:
Read as much bias as you like, but this being a stereo bass setup, subjectively it beats the headphones all day long.
Headphones, point blank:
Wavelet, 1/24:
L+R+sub, MLP, 3,5m distance:
Wavelet, 1/24:
Vector average:
Wavelet, 1/24:
Phase:
Read as much bias as you like, but this being a stereo bass setup, subjectively it beats the headphones all day long.
Keith_W
Master Contributor
EXACTLY. Clarity is a pretty useless measurement.
- Thread Starter
- #171
My interest in room clarity comes from the fact that I sell acoustic treatments. We have been looking for measurements that correspond to people's impressions. Before and after frequency response at the listening position can be barely changed by acoustic treatments and yet people report a profound perceptual improvement. When we look at clarity measurements in the lower midrange and upper bass we do see significant improvement in well treated rooms.
Some people perhaps don't find that compelling. I've even heard people complain about rooms that sound overdamped in the bass. They want less bass control, which is interesting. Overdamped in the treble is a common problem because it's so easy to damp those high frequencies.
DIY LCR - jbl tranducers + 2 x jbl 4645C- all in bafflewall and treated room.
Measurement with Dirac ART 1/6 smoothing
Bassrespons is explosiv with the feeling of being limitles as long i dont get below 20 - 22hz
Much cleaner bass then DLBC
Measurement is done with higher volume
Measurement with Dirac ART 1/6 smoothing
Bassrespons is explosiv with the feeling of being limitles as long i dont get below 20 - 22hz
Much cleaner bass then DLBC
Measurement is done with higher volume
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Keith_W
Master Contributor
The problem with "clarity" is that it does not actually correspond to clarity. There is no agreed-upon number on what good "clarity" is. Remember that clarity is the ratio of the early sound to late sound, C20, C50, and C80 being the first 20ms, 50ms, and 80ms respectively.
The first problem: the period of a 50Hz wave is 20ms, and a 20Hz period is 50ms. A C20 does not even wait for a 20Hz sound wave to fully emerge from the speaker! So "clarity" tends to underestimate bass clarity. OTOH, short wavelengths tend to be easily scattered and absorbed, so high frequency "clarity" is often high. The usual result is an upward tilting clarity measurement, which says nothing about actual bass clarity and gives you a misleading picture of upper treble clarity.
The second problem: one might argue that we should use C80 to look at bass and C20 to look at treble. However - C80 is 1.5 periods of 20Hz, and C20 is 12 periods of 20kHz - we aren't comparing like with like.
The third problem: most of us have problems measuring bass in rooms. The noise floor typically rises at low frequencies at the same time speakers roll off bass. The SNR is often very poor. How do you know if the "late" part of the clarity measurement is actually bass decay or the noise floor? The point is: clarity can't be looked at by itself. You need the actual MDAT so that you can examine the noise floor and make sure that the measurement is interpretable!
The fourth problem: you would think that higher clarity would be better, right? Not so. If you load up your room with acoustic treatment, you will reduce the "late" part and get a very high "clarity" score. Yet we know that overtreating rooms and pushing the RT60 down below 200ms actually reduces speech clarity (I can supply a Toole reference if needed). So, low clarity is bad, high clarity is bad ... what is the ideal "clarity" range? Nobody really knows.
IMO, there is no point looking at the Clarity graph. I think it is utterly useless. Just look at RT60, the step response, spectro, and the ETC and you will get far more information. There are published targets for RT60 depending on room size and application - just follow that instead.
As always, I am open to being persuaded but so far I haven't found any publications that describe what it's good for.
The first problem: the period of a 50Hz wave is 20ms, and a 20Hz period is 50ms. A C20 does not even wait for a 20Hz sound wave to fully emerge from the speaker! So "clarity" tends to underestimate bass clarity. OTOH, short wavelengths tend to be easily scattered and absorbed, so high frequency "clarity" is often high. The usual result is an upward tilting clarity measurement, which says nothing about actual bass clarity and gives you a misleading picture of upper treble clarity.
The second problem: one might argue that we should use C80 to look at bass and C20 to look at treble. However - C80 is 1.5 periods of 20Hz, and C20 is 12 periods of 20kHz - we aren't comparing like with like.
The third problem: most of us have problems measuring bass in rooms. The noise floor typically rises at low frequencies at the same time speakers roll off bass. The SNR is often very poor. How do you know if the "late" part of the clarity measurement is actually bass decay or the noise floor? The point is: clarity can't be looked at by itself. You need the actual MDAT so that you can examine the noise floor and make sure that the measurement is interpretable!
The fourth problem: you would think that higher clarity would be better, right? Not so. If you load up your room with acoustic treatment, you will reduce the "late" part and get a very high "clarity" score. Yet we know that overtreating rooms and pushing the RT60 down below 200ms actually reduces speech clarity (I can supply a Toole reference if needed). So, low clarity is bad, high clarity is bad ... what is the ideal "clarity" range? Nobody really knows.
IMO, there is no point looking at the Clarity graph. I think it is utterly useless. Just look at RT60, the step response, spectro, and the ETC and you will get far more information. There are published targets for RT60 depending on room size and application - just follow that instead.
As always, I am open to being persuaded but so far I haven't found any publications that describe what it's good for.
Much truth in what you say
- Thread Starter
- #175
A test you can do on headphones is to play 16th second bursts with 16th second rests between them at various frequencies. See how low you can go before you really can't make out the starts and stops of the bass tone clearly. If by bass we are exlcuding sub-bass and only talking about frequencies above 60Hz, you'll find that you can clearly hear 16th notes all through the bass range on headphones. This is not the case in most people's listening rooms. The rests between the 16th notes gets filled with reflected sound that makes the notes blur together to various amounts perceptually. This is a considerable problem in many people's listening rooms all the way up to over 600 Hz. Above that most people's rooms will clearly reproduce 16th note bursts and rests, so we're not so concerned with that. Up in that range it's more issues with tonality and imaging.
A 16th note is 62.5 millliseconds. C50 is dealing with 50 milliseconds so that's pretty close, and the perceptual testing I've done on myself with test signals suggests that if the energy in that period after the burst corresponds to about a 10 dB score on the C50 in the bass range, the bass will sound detailed and "quick." A lot of people's scores on this thread are way beyond that. But there are many people who have frequency ranges that are falling well below that, and when I have them play a test sweep of bass frequency bursts I can see and hear that they are having many problem areas at various frequencies.
You can listen to these bursts here: https://www.audiocheck.net/audiotests_matt.php
I just listened to it on my system and I've got a few frequency bands where the bursts get mangled. I can still hear the high frequency ticks from the start of the impulses, but the fundamental tone is blurred. This is a better, more detailed test than the C50 in REW because it lets you hear where you're having problems. Unfortunately it doesn't tell you what frequency you are at in any part of the test.
You can generate these bursts in REW at any frequency you want and find out if there are any problem frequency bands in your room.
I've been working on software that will analyze the burst sweep and chart out a detailed volume level chart that is color coded based on the difference in volume between the peak burst level and the average level in the rest between bursts. You can select any part of the chart and listen to the bursts in that zone, comparing a good measuring area to a bad measuring area. What I can tell you is that if you have a room where the C50 measurement is over 10 through the entire bass range there won't be many audible problems in terms of bass clarity.
Some people may argue that music doesn't use a lot of 16 note speed below 100 Hz. I think that's more or less true. But we can certainly hear it, so I think it makes sense that it should be clearly reproduced at our listening position.
Or D50 is greater than 90%. It's the same thing, but in percentages, and I find it easier to understand; or it's just my habit.
True audiophiles can listen to the matt test from the Stereofile test CD2.
Custom clarity time added in last version
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I still don’t fully understand the practical value of the C50 graph,
but in my room it jumps significantly when I turn Dirac ART on,
so at least it “looks good” and works visually for before/after comparisons.
Since I use Dirac and don’t build speakers myself,
I generally don’t run into integration or ringing issues,
so impulse response and step response haven’t been very useful for me in practice.
As for the ETC:
I can see reflections and spikes, but I don’t know how to interpret them.
Even if I identify a reflection, I can’t tell whether I should treat it with absorption, diffusion, or simply ignore it.
In that sense, ETC feels similar to C50 for me — interesting to look at,
but not something that clearly tells me what to do next.
Not directly bass related, but for actual "clarity" EDT seems to be the useful metric.
From REW manual
"
EDT
Early Decay Time, based on the slope of the Schroeder curve between 0 dB and -10 dB. This is not an RT60 figure, but rather an indication of how quickly the initial sound at the measurement position decays - it is much more location dependent than RT60. A fast early decay (low EDT figure) indicates better clarity than at positions where the EDT is higher.
"
EDT changes per measurement distance because it's a metric that describes relation of direct sound and (early) reflections, which are the most problematic issue in normal living room and rob the clarity. Why is this useful? Before measuring anything do this: Listen your system with small and large listening triangle (experiment by moving yourself, the listener) and try to notice what happens to perceived sound when you move further or closer the speakers (staying equidistant to both). Listen mono noise for example, and concentrate on "size" and clarity of phantom center image. When you are relatively close to speakers, iow small enough listening triangle, the stereo sound (phantom image) is much more precise and clear, than what you have if you move bit further from speakers. Listened too far away stereo sound seems to "bloat" and get hazy in comparison to the small listening triangle. Here you hear effect of early reflections to perceived sound quality. Now you just experiment with the listening distance, move your self and listen the sound in realtime. Experiment with as you learn how things sound there in your place, change positioning and toe-in as needed and determine yourself what you like in your room with your speakers using your own perception not some arbitrary numbers and metrics.
Now that you know how your system sounds like in your room, and how your own auditory system can change sound depending on how early reflections relate to direct sound (listening distance changes this) there might be no need to measure anything! If you want to measure, measure at least EDT and why not the clarity stuff as well, on two of these positions you found out, at position that you found good clarity and where you found it worse. Basically measure small listening triangle (listener closer to speakers) and bigger listening triangle (the listener, or mic, just further out in the room staying equidistant). Now you know quite exactly what metrics and numbers correlate with your perception. Keep on experimenting until you do, just move yourself, walk closer and furher from speakers to hear sound change in real time.
For bass, now that you've found what is maximum stereo triangle size you like the "clarity" of, you'd just move the triangle within your room so that your listening spot lands on place in the room where there is no serious issue with bass, like massive suck out right at some 40-50Hz or what ever. If the listening position is dictated by practical matters like position of sofa otherside of the room as your television, all you can do is acoustic treatment, and notch down worst offending peaks on the bass with EQ. Multisub setup helps for the bad dips.
IF you now do acoustic treatment, try to get EDT measure at listening position close to what you found out is good for you using the simple listening experiment. You might also find out while doing the experiments that you don't actually want that clear of a sound, but you might prefer the "hazy and bloated" sound of loud early reflections. I think this is only way to really improve on your system, from perception first, then measure. If you just measure and get some numbers, there is no way to figure out what to actually do to make it sound "better" to you, in your room with your system and your limitations how to position things.
Another simple test that needs no mics and interpretation other than a listening test: Flutter echo. Clap your hands, hear the robotic sound? That's really bad, the worst possible thing to reduce clarity on your sound. Now, treat at least one of parallel walls (could be floor and ceiling as well) with some acoustic treatment (you could use mattress, pillows, anything temporarily to test) and try to get the robotic sound, the flutter echo, to disappear. If you do this, you'll find out actually a normal livingroom with furnishing isn't too far from studio acoustics (suitable reverberation time), and the only issue is the early reflections. Just shrink your listening triangle size until they are no issue.
Then, go after the bass. The bass "quality" is very much dictated by room and best handled with multisub + DSP. In any case, I highly recommend just experiment with this stuff to find optimal positioning in room, which is the most important thing and varies some by room and by speaker system so there is no solution found online, only pointers.
From REW manual
"
EDT
Early Decay Time, based on the slope of the Schroeder curve between 0 dB and -10 dB. This is not an RT60 figure, but rather an indication of how quickly the initial sound at the measurement position decays - it is much more location dependent than RT60. A fast early decay (low EDT figure) indicates better clarity than at positions where the EDT is higher.
"
EDT changes per measurement distance because it's a metric that describes relation of direct sound and (early) reflections, which are the most problematic issue in normal living room and rob the clarity. Why is this useful? Before measuring anything do this: Listen your system with small and large listening triangle (experiment by moving yourself, the listener) and try to notice what happens to perceived sound when you move further or closer the speakers (staying equidistant to both). Listen mono noise for example, and concentrate on "size" and clarity of phantom center image. When you are relatively close to speakers, iow small enough listening triangle, the stereo sound (phantom image) is much more precise and clear, than what you have if you move bit further from speakers. Listened too far away stereo sound seems to "bloat" and get hazy in comparison to the small listening triangle. Here you hear effect of early reflections to perceived sound quality. Now you just experiment with the listening distance, move your self and listen the sound in realtime. Experiment with as you learn how things sound there in your place, change positioning and toe-in as needed and determine yourself what you like in your room with your speakers using your own perception not some arbitrary numbers and metrics.
Now that you know how your system sounds like in your room, and how your own auditory system can change sound depending on how early reflections relate to direct sound (listening distance changes this) there might be no need to measure anything! If you want to measure, measure at least EDT and why not the clarity stuff as well, on two of these positions you found out, at position that you found good clarity and where you found it worse. Basically measure small listening triangle (listener closer to speakers) and bigger listening triangle (the listener, or mic, just further out in the room staying equidistant). Now you know quite exactly what metrics and numbers correlate with your perception. Keep on experimenting until you do, just move yourself, walk closer and furher from speakers to hear sound change in real time.
For bass, now that you've found what is maximum stereo triangle size you like the "clarity" of, you'd just move the triangle within your room so that your listening spot lands on place in the room where there is no serious issue with bass, like massive suck out right at some 40-50Hz or what ever. If the listening position is dictated by practical matters like position of sofa otherside of the room as your television, all you can do is acoustic treatment, and notch down worst offending peaks on the bass with EQ. Multisub setup helps for the bad dips.
IF you now do acoustic treatment, try to get EDT measure at listening position close to what you found out is good for you using the simple listening experiment. You might also find out while doing the experiments that you don't actually want that clear of a sound, but you might prefer the "hazy and bloated" sound of loud early reflections. I think this is only way to really improve on your system, from perception first, then measure. If you just measure and get some numbers, there is no way to figure out what to actually do to make it sound "better" to you, in your room with your system and your limitations how to position things.
Another simple test that needs no mics and interpretation other than a listening test: Flutter echo. Clap your hands, hear the robotic sound? That's really bad, the worst possible thing to reduce clarity on your sound. Now, treat at least one of parallel walls (could be floor and ceiling as well) with some acoustic treatment (you could use mattress, pillows, anything temporarily to test) and try to get the robotic sound, the flutter echo, to disappear. If you do this, you'll find out actually a normal livingroom with furnishing isn't too far from studio acoustics (suitable reverberation time), and the only issue is the early reflections. Just shrink your listening triangle size until they are no issue.
Then, go after the bass. The bass "quality" is very much dictated by room and best handled with multisub + DSP. In any case, I highly recommend just experiment with this stuff to find optimal positioning in room, which is the most important thing and varies some by room and by speaker system so there is no solution found online, only pointers.
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Keith_W
Master Contributor
The timing of the spikes tells you the delay, and from the delay you can work out the distance. Then you look around your room and ask yourself which surface is responsible for the reflection. All described in the REW eBook.
ASR people must be sick of me pushing that book by now. But that's why the book was written - these questions come up really often.
Sure, I understand how to identify the surface geometrically.
That part is clear enough.
But what I'm still missing is the actionable part:
Even if I know
“this spike comes from the right wall 1.7m away,”
I still don’t know:
- Should I absorb it?
- Should I diffuse it?
- Should I ignore it?
- How strong does a reflection have to be before it's actually a problem?
- How much reduction is the target?
- What counts as “acceptable” in a small domestic room?
but it does not really explain what to do with the information
or what thresholds matter in practice,
at least for typical living-room environments.
So I can identify reflections, yes.
But the step from “I know the delay” to “I know the correct treatment”
is not explained, and that’s the part I was hoping to understand.
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