Bulding the Room2 listening room

[Kvalsvoll]

Nothing to see so far, still working on it.

 

Absorbers close to speakers improved things, you can see it in the measurements if you look very closely.

Which means it did not improve enough.

But they look nice.

 

I have to improve this, the room is useless for the intended purpose like it is now.

Unfortunately the dips are most likely caused by a combination of reflections from the back corners and side wall reflections, and that is not easy to fix without reconstruction.

 

Lets see.. the measurements are open here, I can find a plot of the situation like it is now:

 

The problems are the peaks around 800hz-1k and the dips in the 200-500hz range.

Measurements with a different set of speakers shows close to identical response, this is caused by the room.

 

[Kvalsvoll]

Comparing the Room2 with some eq and The Moderate HT.

 

I measured both rooms, spl and velocity.

That they sound different should not be a surprise, but the differences I am trying to analyze now, is the low-mid - mid range.

The ModerateHT has better realism and impact in this range.

 

Why is that so.

The differences can not be explained by looking at the frequency response alone.

With eq on Room2 to boost the 200hz-600hz range, it sounds more balanced, and  freg resp does not have the dip.

 

Room2 spl and velocity 0-90-h directions:

 

MderateHT spl and velocity 0-90-h directions:

 

Room2 decay (20ms lines, 10ms pre-window):

 

ModeratHT decay:

 

Room2 spectrogram:

 

ModeratHT spectrogram:

 

The problem is the Room2, the other room can be seen as a reference.

The velocity spl plots reveal that the cause for the peak around 800hz is likely to be ceiling or floor.

The dips may be cause by reflections from the back, but down at 200hz there may be a sideways reflection, and up closer to 600hz there may be a vertical reflection.

 

If I place the speakers from the ModerateHT room in to Room2, they have the same faults in the response, only worse.

So this has to be fixed, and it is a room acoustic problem, it is not the speakers.

 

[SME]

I would try the spectrogram with a variety of different window sizes, as little as 0.5 ms but no more than 10 ms or so, to see if you can identify the approximate time of arrival of one or more reflections that adversely impact the sound in the lower/mid midrange.  With a window size of 40 ms like you appear to be using, you won't have nearly enough time resolution to identify discrete reflections.

 

As I've already said, a big caveat to the ETC and IR are their accentuation of high frequency energy.  It makes it very easy to see reflections that have high frequency energy, but if your room treatments absorb the highs while leaving some mid-range intact, than it will make the reflection much harder to see there.  Likewise, if the inverse is true, you may see the reflection(s) in the IR or ETC but not realize the absence of mid-range there.  The spectrogram with small windows is very useful for examining not just the time of arrival of reflections but also (with limits) the frequency composition of those reflections.  Knowing the time of arrival of a reflection can help you identify the path that the sound travelled as well as how well your room treatment (if any) is working in that location.

[3ll3d00d]

 

Room2 spl and velocity 0-90-h directions:

Rom2 spl v 0 90 h.png

 

 

The velocity spl plots reveal that the cause for the peak around 800hz is likely to be ceiling or floor.

The dips may be cause by reflections from the back, but down at 200hz there may be a sideways reflection, and up closer to 600hz there may be a vertical reflection.

 

What is the h direction? what in that plot tells you the peak is the ceiling or the floor?

[Kvalsvoll]

What is the h direction? what in that plot tells you the peak is the ceiling or the floor?

 

h direction is horizontal, meaning it is measured in the horizontal plane, it shows the amplitude of the velocity vector normal to this plane, so this will then be the velocity of the sound in the vertical direction.

 

Sound waves can be fully described by its scalar pressure - spl - and the particle velocity.

Particle velocity is a vector -  it has both magnitude and direction.

Usually we only measure the spl, and leave it at that.

Measuring the velocity in 3 directions gives additional information about the sound, such as direction.

 

In free field with no reflections there will only be velocity in the 0-direction.

When the h-direction plot shows velocity with magnitude close to or above the 0-direction something has changed the direction of the sound waves.

In a room this directional change is a result of the reflections from the surfaces in the room.

 

By looking at the velocity plots it is then possible to get more information about what is causing a troublesome reflection.

[Kvalsvoll]

I would try the spectrogram with a variety of different window sizes, as little as 0.5 ms but no more than 10 ms or so, to see if you can identify the approximate time of arrival of one or more reflections that adversely impact the sound in the lower/mid midrange.  With a window size of 40 ms like you appear to be using, you won't have nearly enough time resolution to identify discrete reflections.

 

As I've already said, a big caveat to the ETC and IR are their accentuation of high frequency energy.  It makes it very easy to see reflections that have high frequency energy, but if your room treatments absorb the highs while leaving some mid-range intact, than it will make the reflection much harder to see there.  Likewise, if the inverse is true, you may see the reflection(s) in the IR or ETC but not realize the absence of mid-range there.  The spectrogram with small windows is very useful for examining not just the time of arrival of reflections but also (with limits) the frequency composition of those reflections.  Knowing the time of arrival of a reflection can help you identify the path that the sound travelled as well as how well your room treatment (if any) is working in that location.

 

Yes, ir/etc is not useful at all to see what is really going on, it is also quite easy to get a very "good" ir by adding some thin high frequency absorption in the right places, but this will not improve the sound, only make it more dead at high frequencies.

 

I have the mdat-files, so for me it is possible to view and analyze these measurements in any imaginable way, but when posting measurements it is not practical to present more than a few graphs, with one scaling for each chart type.

 

The idea of making the complete set with spl and velocity is to have information that can reveal where the reflections are coming from both in time and direction.

 

I managed to remove the 200hz dip completely, but the sound did not improve much.

Or did it.

Sometimes I wish I had golden ears; then I could just swap the speaker cables, sit down and listen, and experience a huge improvement across the whole midrange, with "prat" and "palpable bass".

But some of us are not so easily fooled, we need real improvements to be satisfied.

 

I need to find a more reliable way to do listening evaluations, I think I will look into that later today.

 

It's not that the sound is horribly bad, it is just that the other room is so much better.

Having this possibility to compare instantly reveals differences quite effectively.

[maxmercy]

Interesting.  How do you feel the delayed LF in Room 2 according to the spectrogram plays a part in what you are perceiving?

 

JSS

[Kvalsvoll]

It should not have significance, but more experiments are necessary to remove that possibility.

 

The bass is actually not delayed, the initial pulse starts at 0, it is the room that makes adds group delay and time smearing.

The bass is perceived as quite good, but not like the other room, especially when turning up the volume the difference is very obvious. 

Understandable and acceptable, considering the very huge difference in size and capacity of the bass systems.

 

Some of the differences may be caused by the F2 speaker with the rather generous contribution in the 2k-5k range, this is caused by a fault in the radiation pattern of the horn.

The added late energy in the 2k-5k range will affect perception of tonal balance on transients, and can also (as mentioned by @SME) mask.

 

It's like the transients have lost a lot of the addictive realism that the other set-up has, and that is a huge contributor to the addiction you get when listening to it - you always want to hear one more album.

 

Smoothness and clarity and resolution at higher frequencies is a little better on the F2 speakers, but they also sound a little more laid-back.

Voices have very good presence, like there is a person inside the room.

 

But there are measurable differences, clearly there is a problem in the lower mids where you get huge cancellations, and the phase and timing errors will still be there even after eq.

The peak around 600hz-1k will also contribute to the tonal balance, it is quite huge.

.

[SME]

The idea of making the complete set with spl and velocity is to have information that can reveal where the reflections are coming from both in time and direction.

 

I managed to remove the 200hz dip completely, but the sound did not improve much.

Or did it.

Sometimes I wish I had golden ears; then I could just swap the speaker cables, sit down and listen, and experience a huge improvement across the whole midrange, with "prat" and "palpable bass".

But some of us are not so easily fooled, we need real improvements to be satisfied.

 

I need to find a more reliable way to do listening evaluations, I think I will look into that later today.

 

It's not that the sound is horribly bad, it is just that the other room is so much better.

Having this possibility to compare instantly reveals differences quite effectively.

 

Ahh, now I see how velocity measurements could be useful for acoustic evaluation.  I expect this will work better for higher frequencies, and I see a caveat.  What happens to particle velocity when reflections arrive from two different directions at the same time?  They combine to yield a vector that doesn't necessarily point in the direction of either reflection.  What I'm not sure of is how to tell whether that's happened or not.

 

As for listening, that's the most important part of setting up a system and is also the hardest part.  Audio memory is very finicky, even in listeners with real skill.  I'm just a bit amazed and disturbed at the kind of things placebophiles obsess over.  It's so sad and makes me think that the vast majority of the population has never heard a good sound system with good room acoustics in their lives, despite hearing problems becoming more widespread.

 

Admittedly, I don't think I've ever heard what could be regarded as a reference quality system.  I hope to eventually achieve this in my living room, and I hope that once I finish my speakers and subs, add more treatments, and optimize my DSP, I'll be very close.  Or will I?  At some point, I may have to do a tour of top-shelf sound systems, both DIYers like people here and a high end music mastering studio and dubstage in order to calibrate my ears.  Because at the end of the day, I make decisions based on my ears in the context of the data I measure.  Measurements provide a lot of useful data, but it is not always clear how to interpret that data, especially when my measurements and my ears seem to disagree.  There's no view of the measurement data that fully characterizes how the system will sound.  Some helpful tools exist like frequency-dependent windowing to try to get a more psychoacoustically accurate view, but I believe these are incomplete and that there's still a ways to go before we have a reliable way of understanding the data in a psychoacoustic context.

 

I think your work here is fascinating.  I can imagine you or I being quite happy with the sound of the system in Room 2, were it not for the fact that a better sounding system/room is "just down the hall".

[Kvalsvoll]

Velocity measurements can only tell the direction of the sound, what is actually happening can be a mix of reflections from many directions.

From the plots I presented here it is not even possible to see if the sound comes from front or back, only if the direction is front-back.

 

Just listened to several tracks, comparing the 2 systems.

I still believe there is a difference in transient attack in the midrange.

Like the drums loose some of the initial snap.

Had the spectrum analyzer running, to see what i am actually listening to. 

Frequency distribution of signals are often much wider than you think.

Example: Hadouk Trio, Moussa.

 

I also believe the Room2 system has improved.

EQ to remove the loss of energy in the 200-500hz range, adjustments to acoustic absorption.

 

I find it fascinating to observe properties of sound, and then try to find what is causing what I hear.

Everything can be measured, but it is not that easy to tell how to analyze the measurements, and see how they correlate with what is actually heard.

[Kvalsvoll]

Solved one part of the problem - the peak around 1k:

 

Turns out the last crossover version on the F2 speaker had a fault in the correction circuit for the lf driver.

A quick-fix improves things a lot, much smoother response, now it sounds kind of ok without additional eq.

 

At 500hz+ wavelengths are already getting small enough to be possible to find by moving a smaller absorption panel around, while observing changes in the response on rta, I use this technique a lot, both for placement, room acoustics and also to help identifying problems with speakers.

 

But I could not get rid of this peak, no matter where and what I placed around in different locations.

The only thing that worked was blocking the direct sound from the speaker.

Dragged a different speaker into the room and placed it at the exact same location and there it is - no peak, just horrible response below 500hz.

 

There is still some gain above 500hz, but the level is acceptable.

So now the problem with the dips from 500hz and down remains.

[Kvalsvoll]

Some minor acoustic fixes, and repositioned the speakers - with the corrected crossover.

 

Starting to sound quite nice now, can easily enjoy music for several hours in there.

 

If I can fix the remaining issues, this will be something quite special.

Now there is much more defined body on instruments in the lower midrange, it is fun when it starts to sound like real things are playing.

 

So far I believe the listening experience correlates well with measurements.

The better it measures, the better it sounds.

But it can sometimes be a challenge to analyze and find what exactly caused a specific difference in perceived sound.

 

The only deviation from ideal, clean, uncolored I have found to be good for sound is the slightly tilted response with more level at lower frequencies - perhaps also the added reflections from sides, because they do actually compromise the IR.

 

Clarity down through the whole midrange has improved.

One interesting observation is that even with this very dry front stage it seems to amplify room information from the recording - it is much more like you move the whole listening room in to the concert hall, or jazz club, or studio - depends more on the recording, and the acoustics of the listening room is simply not there.

And there is so much of this room information, it is like there is much more room than you get in a listening room with no acoustic treatment.

 

QSound sounds better than a surround system you can buy at a local shop.

There is sound from the sides, and even above, and from behind.

And not only ambient effects, there are objects with physical size and location, like you get from a very good surround setup.

But of course, this only works in the sweetspot.

 

The work with this room confirms that focusing on a flat/smooth frequency response alone is not enough, what happens in the time domain is what makes the real differences.

[Kvalsvoll]

Pictures of the cylindrical diffusors while we wait for the acoustics to "burn in".

 

Left side diffusor:

 

The back of the room with 2 side, one small back, one larger top back:

 

Cylindrical diffusors are simple and should work well with the small distances in this room.

Reflection level from the left speaker - reflecting from the right corner with the fireplace - is quite high.

 

[Kvalsvoll]

I have mentioned before some of the consequences of radiation pattern - mainly, general differences between horn - small direct radiator.

 

One aspect is that the horn tend to sound brighter/louder, for same spl and frequency response.

This is due to differences in radiation pattern.

 

The small direct radiator (dome and very small midrange cone driver) has a wide radiation pattern where the sound slowly decreases in level as you move further off-axis.

The controlled radiation horns in my speakers have fairly flat response across a defined angle, and then drops very fast when moving further off-axis. 

 

The consequences are that reflections from the room behave very different.

The horn focuses the sound more towards the back of the room, and actually creates louder reflections, after some time.

The dome/small speaker will have stronger reflection level overall, especially very early reflection level will be louder, but the reflections coming from the back of the room will be smaller.

 

I tried to make some graphs to help illustrate this:

 

ETC with smoothing so you can see the individual plots - horn gives overall lower reflection level, but some around 10ms are louder:

 

IR, no smoothing, show that the peak is quite a lot higher in level on the horn speaker:

 

 

ETC/IR plots are normalized, so differences in loudness between the speakers have no significance.

 

This can also be seen in the waterfall plot - the horn will tend to have more late energy.

It is this late energy that adds to the perception of tonal balance.

 

One consequence of the horn radiation is that it makes it easier to create the sound I want in Room2.

Less early reflections even with the speakers close to wall boundaries give improved clarity, and the strong focused sound towards the back makes it possible to use small diffusors to create lots of ambience.

[Kvalsvoll]

I think I have the perfect recipe for selling uber-expensive speakers in the Room2 now:

 

- First, play some dynamic and full-frequency content in the Moderate Cinema, on the big system, at full volume (that is in the 0dB to +8dB range).

- Then move the customer into the sweetspot in Room2, and put on some quiet vocal music like Susan Wong, play at modest volume, make sure to point out how "real and present" the vocal is.

- The potential customer has already a memory of the transient response and dynamics and realism from the other system, and now experiences this audiophile vocal qualities - all those qualities are now mixed up together, in an assumption that this is what will create the magic sound in their own home.

- The customer brings the uber-exp speakers home, and.. disappointed - realism and dynamics are lost, it does not sound like the demo. But the vocal sure is nice, at modest volumes, after placing the speakers out in to the room far away from the front wall.

- Since the magic sound did not manifest, something must be wrong with the gear or the room. Perhaps a larger bass system is what it takes, or some new amplifiers.. perhaps a new dac..

- And there you have it, we have a business - this customer will never be satisfied, and will continue upgrading and changing gear forever or until the money runs out.

 

 

Installing the F1 speakers in Room2 confirms the room is not that bad now, though there are still some problems with cancellations.

However, I now believe it was a huge mistake to do this project with the new prototype F2 speakers.

Those speakers are still in development, lots of issues remain.

They do not image like the F1, they do not have that sense of effortless transients at moderate volume, they do not have that realism and explosive impact on louder volumes, the high frequencies sound kind of muted and there is a distinct color to the sound in the upper midrange, they do not sound pleasant and comfortable at tear-the-house-down volumes.

 

While the F2 in the current state sounds more like a typical hifi-speaker on steroids. the F1 is a different animal.

As an example; put on Flashbulb - We are the dispelled (find it on bandcamp).

Play this at 0dB in the Room2 - sounds loud, but not too loud, still not pleasant, and it sounds like the resolution in the recording is not very good, the bass is very colored, this is not a fault of the F2 rather than the bass system with 2 excellent but toooooooo small S6-14 in combination with the room.

Now fire up the Moderate Cinema system, and enjoy.

The difference in resolution and realism and dynamic impact is huge.

That the bass is much better should not come as a surprise, but there is more to it than that - the midrange is more see-through and dynamic, the highs have more clarity and reveals more of the instruments individual character, the whole presentation is a lot more pleasant to listen to, and it sure makes sense to listen at this quite loud volume.

 

I think I will put another set of F1 speakers in to the Room2.

The F2 speaker was something I wanted to make because I Iiked the idea, and I needed to try out a new HF section for higher output and ability to go lower than the horn loaded ribbons.

Other larger speaker designs are coming up, and those will use the 8" LF/mid drivers from he F1/C1, but I had hoped to be able to use the higher output AMT horn for HF, but as this turned out that is really not an option.

 

The room is important, but it is the speakers the determines what is possible to achieve.

[Kvalsvoll]

Testing new F1-p speakers in Room2:

 

The room got a new left sidewall absorber, the small one below the window is not good enough.

 

I am now using the room to work on new speakers, and it is easier and better to work in compared to untreated. 

Both measurements and listening is more consistent and easier, and it also sounds much better.

 

The F1-p presents a sound different from the unfinished F2.

I have some measurements I may want to share later, initially it looks like they measure about the same, but there are differences, but they are not very obvious. 

 

[maxmercy]

So it looks like front wall, side wall 1st reflection, floor 1st reflection are addressed in that photo.  Are back-wall reflections simply diffused?  Anything on the ceiling?

 

JSS

[Kvalsvoll]

Here http://data-bass.ipbhost.com/index.php?/topic/538-bulding-the-room2-listening-room/page-4#entry13919 is a picture of the back, there is a large opening and not practical to do much more. The opening obviously does not reflect any sound. There are 4 ceiling absorbers, you can see the 2 back units in the picture.

 

The floor reflection is far from completely absorbed, the small boxes only changes things a little to the better in the midrange, the F1 benefits from having something on the floor in front of them.

[Kvalsvoll]

This is how it looks now:

 

 

Measures like this (20ms interval, 20ms pre-window):

 

 

 

Velocity measurements reveals the directivity is very good, better than the larger F2 speakers from previous measurements. 

 

The sound can be described as addictive.

[maxmercy]

What is below the vertical blinds on the left?

 

JSS

[Kvalsvoll]

That is the left sidewall absorber. 

 

It is much larger than the first version, now covering the lower part of the window and 20cm thick.

Experiments with two 120cm x 60cm absorbers on the left wall showed significant improvements, so I had to change it.

 

The room is quite narrow in width, and that is a problem.

[SME]

This is how it looks now:

 

F1p testing i rom2 2.jpg

 

Measures like this (20ms interval, 20ms pre-window):

 

F1 decay 1.png

 

 

Velocity measurements reveals the directivity is very good, better than the larger F2 speakers from previous measurements. 

 

The sound can be described as addictive.

 

That looks real nice.  Are you getting the 3D sound you were looking for?

[Kvalsvoll]

@SME, thank you for the 'nice', was going to comment on that, when I realize I don't know if you mean the visuals or the technical performance..

 

3D is quite good, with much better placement and separation in depth compared to The Moderate Cinema.

Vocal is better,

But of course the resulting sound depends on the speakers.

I have never heard a traditional hifi-speaker that can give a realistic presentation like when instruments appear like physical objects, regardless of room acoustics, I believe it is necessary to have horns or larger planar panels to get that.

Those F1 speakers are too small to have good directivity control at lower frequencies, but still they present sound in a very physical and realistic way.

In this small room it works quite well.

 

The tonal balance is too bright, and it does not sound as relaxed and pleasant as the other room.

The cancellations and reflections in the low midrange is a problem that needs to be solved, you can see it on the frequency response and the decay - there is too little energy in the 200hz - 600hz range. 

[SME]

I think the technical performance looks better than previous data you posted.  I know that room is very small and difficult, and I think it's interesting to see what can be achieved in that size space.

[Kvalsvoll]

The difference is in the radiation pattern of the speakers, the F1 horn has better pattern and 2 bass drivers makes it possible to achieve a better pattern in the midrange.

 

I will fix the remaining issues, but I am not sure how to proceed right now.

Next up is a new small bass system, to be tested in this room.