Bass punch threshold

[maxmercy]

My crude experiments with a generated drum impulse:

 

1. Original

2. BW6

3. LR2

4. LR4

 

You are right.   The room will introduce far worse problems than this, unless you run an SBA/DBA and baffle wall with proper 1st reflection absorption 1 octave below cross from sub to mains.

 

JSS

[TTS56A]

What about these? 

 

 

 

That's seems to be a powerful slamming, i'd like to know what kind of waveform has it! Of course mic has distorted it too much 

[Ricci]

I think the key is to know how different sound field properties behave:

 

1) car sound field: LP approach near field, then wave front behave like spherical wave, so PVL and SPL are out of phase

 

2) concert sound field: LP approach far field, then wave front behave like plane wave, so PVL and SPL are in phase.

 

That's may be a reason and i firmly believe that SIL plays a very important role in how we perceive the intensity through our body

 

 

Correct. In the car you are effectively nearfield. Do you have information on why the partical velocity and SPL would be out of phase? I'm not so sure about this but haven't researched it. The extent of my particle velocity knowledge comes from designing horn subs and deals with it internally inside the horn path and managing it at the exit rather than as propagated into a room.

 

Most car audio systems have a vented cab tuned near 35Hz with a high inductance driver. Combine the cabin gain, the LPF and HPF and the result is a mountainous peak 30-50Hz and a hole from 80-150Hz are typical. Usually the SW 10-20dB hotter than the rest of the range as well. This is not going to sound very "tight" rather booming and one note. I should have qualified this is not the type of system I would reference as a "good" car audio system. (Perhaps your friends was, I don't know) Capable midbass and HF devices and a at least somewhat flat/extended bass are required. I've heard a number of systems using sealed or IB bass drivers with no HPF and some attention given to the midbass transition and overall bass/lower midrange response shape and these can have extremely sharp attack/decay subjectively. What I have in my Jeep  currently is nothing special but the way kick drum transients are rendered is very addictive. I should probably take another set of more in depth measurements to see what is going on. I know that the mid and high frequency range is going to be a mess.

 

One thing I've not heard mentioned about outdoor sound is wind. That's one of the biggest detriments to outdoor sound. If you are far enough away you can easily hear the sound moving around in the wind. The HF and MF are most easily heard.

[Ricci]

On a somewhat related note I messed with REW's room calculator the other day and I must say it did match up quite well with the measurements of my basement even though it lacked a large hallway, fireplace and all of the furnishings in room. The major issues due to the room dims and listening position placement were spot on.

 

 

My crude experiments with a generated drum impulse:

 

1. Original

2. BW6

3. LR2

4. LR4

 

You are right.   The room will introduce far worse problems than this, unless you run an SBA/DBA and baffle wall with proper 1st reflection absorption 1 octave below cross from sub to mains.

 

JSS

 

 

I remember we briefly discussed this before. We know that the different filters will affect the time response of the signal passing through among other things. I can't recall,  the original drum transient was wideband correct and the filters applied would have taken effect inside the overall bandwidth?

 

A more telling analysis would be the acoustic signal captured from a wideband speaker with no crossover applied to the signal and the same signal output and captured from a 2 way system after being split and recombined in the active filter network using various filters. The on axis response shapes of the speakers would need to be matched closely as well. (Likely complicating matters with additional filters.)

[Kvalsvoll]

...

I can definitely see that space giving you a lot of trouble.  Is there any possibility of employing a compact near-field sub or MBM, disguised as an end-table?  I know, I know.  The answer is probably "no", so I will continue.

..

 

This room will be used for testing various bass systems, which will be set up on the front wall, in the corners.

That will change things quite dramatically.

 

But the sound is already much, much better - the front wall is finished.

More punch, if for nothing else because it is now pleasant at louder listening levels.

I will measure it today.

 

There is a plan, and the front wall is part of that plan, it does not solve everything by itself.

[Kvalsvoll]

My crude experiments with a generated drum impulse:

 

1. Original

2. BW6

3. LR2

4. LR4

 

You are right.   The room will introduce far worse problems than this, unless you run an SBA/DBA and baffle wall with proper 1st reflection absorption 1 octave below cross from sub to mains.

 

JSS

 

Exactly.

What the room does to those waveforms is much worse than any phase shift in filters.

[TTS56A]

Correct. In the car you are effectively nearfield. Do you have information on why the partical velocity and SPL would be out of phase? I'm not so sure about this but haven't researched it. The extent of my particle velocity knowledge comes from designing horn subs and deals with it internally inside the horn path and managing it at the exit rather than as propagated into a room.

 

 

Unfortunately i don't know yet the real reason why PVL and SPL are out of phase in the near field, though seems to be related to the way of propagation. Close to the source the air behaves as an incompressible fluid, then most of the particles are only bouncing around the cone but they stil don't propagate as energy, so the energy is actually stored. I think this is called reactive filed. As we move away from the source, once we get in the far field, the wavefront become a plane wave and if there are no reflections from boundaries this will be a pure active field (PVL and SPL are in perfect quadrature). However this is frequency dependent, than for long wavelenghts, the wave requires more traveled distance to be considerated as plane wave. I suggest this is the main reason why we can't feel "real" low frequiencies in small rooms.

 

i googled it a lot but there are no clear explanation though. Of course i'd like to know more about it! Unfortunately it's a niche argument and few people know the real truth... 

[Kvalsvoll]

On a somewhat related note I messed with REW's room calculator the other day and I must say it did match up quite well with the measurements of my basement even though it lacked a large hallway, fireplace and all of the furnishings in room. The major issues due to the room dims and listening position placement were spot on.

..

 

I have tried it on several rooms, and it is surprisingly good, considering the simple data set entered into the model.

Very good for finding speaker and listening positions, when you measure there is a good match between problems shown in the simulator and the actual response.

[lukeamdman]

I have tried it on several rooms, and it is surprisingly good, considering the simple data set entered into the model.

Very good for finding speaker and listening positions, when you measure there is a good match between problems shown in the simulator and the actual response.

 

I tried it as well and was impressed with it's accuracy.  It predicted the huge 30hz null I have on the front row near perfectly. 

[Kvalsvoll]

After fixing the front wall, the system sounds better.

 

If so, there must be a measurable and significant difference:

 

 

Grey is before fix, red and green are 2 different speaker positions after front wall fix.

Well, looks pretty much the same to me..

 

If you zoom in on unsmoothed graph, there are differences - the fixed ones are smoother and have less dips and peaks.

 

So, have I finally acquired those golden ears, which enables hearing things that can not be measured, you know those things that can not be explained by science..

 

But take a look at the decay:

 

First, pre-fix:

 

 

After:

 

 

This is a very significant difference.

Even though the steady-state response is similar, the decay is more dead and much more linear in frequency.

 

If we look at the velocity part of the sound field, we can also study the directivity of the sound field, which gives an indication about properties of the sound field:

 

 

Light green is 0 degrees, dark green is 90 degrees.

We see that part from an anomaly around 500hz, the sound field is quite directional, and the velocity level is quite good.

This indicates that the sound field is directional like a plane wave - an active sound field, with high sound intensity.

And this is how it sounds.

Powerful, with a sense of tactile feel, even at lower volumes, well up into the midrange.

 

Unfortunately I do not have velocity measurements from before front wall fix with the same speakers.

I do have measurements from this same room, with a different set of speakers, and those show a quite different situation, where velocity in different directions appear chaotic - pretty much like it is here around 500hz, all over the frequency spectrum.

The speakers are very different, but they are both acoustically small below a few 100hz, so differences at lower freqs can be assumed to be caused by changes in room acoustics.

 

[SME]

A more telling analysis would be the acoustic signal captured from a wideband speaker with no crossover applied to the signal and the same signal output and captured from a 2 way system after being split and recombined in the active filter network using various filters. The on axis response shapes of the speakers would need to be matched closely as well. (Likely complicating matters with additional filters.)

 

This sounds like overkill.  I think just adding the extra phase rotations into the signal using all-pass filters in your signal chain ought to work well enough.  As a point of related curiosity, I am currently running multiple kinds of speakers for my mains.  In order to fix the "timber matching" problem, I applied 4th-order all-pass filters in both types of speakers to imitate the phase rotation in the crossovers of each.  This ensured that the speakers played in-phase together and improved the imaging a lot.  OTOH, I have not noticed any audible degradation due to the extra low frequency delay.  Admittedly, I should actually A/B it before judging, but I suspect phase rotations are just more audible at some frequencies than others.

[TTS56A]

...but I suspect phase rotations are just more audible at some frequencies than others.

 

In my experiments i noticed that phase shift really matters for frequencies < 200 Hz. The main problem, however, is that typical rooms introduce a lot of phase rotations respect to a 4th order filter, so the final sound will be no worse than was before filter. I would think that only outdoor test can reveal the truth. Another important thing is that long and compressed impulses (as can be a dance kick 150-200ms) require more phase shift respect to short ones (jazz overdamped kick 30-40ms) to be audibile. That's the same for all transient sounds. This is the reason why low dynamic contents are less likely to phase shift.

[TTS56A]

If we look at the velocity part of the sound field, we can also study the directivity of the sound field, which gives an indication about properties of the sound field:

 

rom2 front wall fixed velocity.png

 

Light green is 0 degrees, dark green is 90 degrees.

We see that part from an anomaly around 500hz, the sound field is quite directional, and the velocity level is quite good.

This indicates that the sound field is directional like a plane wave - an active sound field, with high sound intensity.

And this is how it sounds.

Powerful, with a sense of tactile feel, even at lower volumes, well up into the midrange.

 

 

This is what i've always wondered! I'd like to know more about it 

 

Powerful, with a sense of tactile feel, even at lower volumes, well up into the midrange.  

 

You said well, this is the same sensation when i listen to outdoor concerts, even if the sound is played back, not well balanced or bass is less that what i aspected, i always feel a real sense of tactile feedback even measuring SPL lower than my room...

[Kvalsvoll]

This is what i've always wondered! I'd like to know more about it 

 

..

i always feel a real sense of tactile feedback even measuring SPL lower than my room...

 

I would also like to know more about this, because this is what really separates a reproduction that is engaging, exciting and interesting to listen to, compared to something that is merely background music, regardless of how "nice" and detailed and smooth it sounds.

 

Peaks spl obviously makes a difference.

On a concert there is feed directly from the instruments, no loudness-war limiter, and the speakers are capable of very high spl at close distance.

So peaks has a much better chance to survive.

 

Still, I believe there are differences caused by speakers and room acoustics.

Until now I had a 2. system with ordinary old-style hifi-speakers - dome tweeters, small midranges, small woofer.

(This system is now retired, along with the class-A amplifier, which is kind of sad, but necessary, to build this new room 2.)

I observed that this system played kind of laid-back and with less powerful sound, compared to the new generation speakers.

With calibrated level, it was easy to listen to something on one system at a known spl level, and then move less than 10m to hear exactly the same at the same spl on the other.

The new generation sounds louder and has much better impact, at same volume and with same program material.

 

This has to do with sound-field properties.

Intensity, direction, amount of direct sound, level and decay of reflections.

 

To get enough spl is relatively easy.

It can even be done by using hifi-drivers and dome tweeters.

Peak levels above 120dB is not very interesting, it gets too loud to be pleasant to listen to.

But spl alone is not enough.

[3ll3d00d]

@Kvalsvoll how are you measuring the sound field again? ISTR you posted the details somewhere but I don't know where

[Kvalsvoll]

@Kvalsvoll how are you measuring the sound field again? ISTR you posted the details somewhere but I don't know where

 

It is in the "Understanding tactile feedback"-thread, here is a link to one of the posts about measurements:

http://data-bass.ipbhost.com/index.php?/topic/404-understanding-and-optimizing-tactile-feedback/page-4#entry7461

[SME]

So you are saying that acoustic treatment has cleaned up the particle velocity field, and that the tactile experience is better as a consequence?  Hmm.  I can definitely see why bass absorption would tend to clean up the velocity field, but I remain skeptical that the velocity field is what's important to the tactile experience.

 

Do reduced bass decay times improve punch?  Absolutely, yes.  Our ability to hear bass is actually quite poor, and an excess of SPL at a certain frequency is more likely to mask sounds at other frequencies, including transients.  Worse still, small rooms tend to have modal resonances that ring for a long time when excited by wide-band transients.  These resonances substantially mask the other content in the transient and kill the perception of it.

 

Now, to the extent that you can address your early reflection problems on the ceiling and side-walls, you can reduce some of the nulls, and get more energy to arrive in that initial impulse.  I look forward to seeing where you go next with that space. 

[TTS56A]

I also don't believe more woofer radiation surface versus excursion makes any difference either.  The reasoning is the same.  What happens instead when the woofer size approaches the wavelength is that the woofer beams.

 

I took a look to it, and according to this manual, as the size of the radiator become larger compared to the wavelenght, ("ka" increase), the directivity factor also increase, but the wavefront become planar at closer distance. 

 

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[Ricci]

  Hmm.  I can definitely see why bass absorption would tend to clean up the velocity field, but I remain skeptical that the velocity field is what's important to the tactile experience.

 

 

Ditto. I'm still unconvinced that this is as important to the subjective tactile response as other factors. It is something worthy of further research and discussion.

[Kvalsvoll]

The sound field gets more directional and the particle velocity and intensity is closer to the plane-wave far-field situation when reflections are removed.

This can be seen from the measurements.

 

And the sound is perceived as better, the tactile is better and stronger, when reflections are removed.

As in the outdoor situation - there is more punch outdoor.

 

But it is not necessarily increased velocity that is the cause of the perceived differences.

Decay, frequency response smoothness, less gd/phase shift - all improves.

 

At low frequencies, <40hz, I am convinced that velocity is an important parameter for how the sound is perceived.

At higher frequencies the intensity alone may be more important - as in the upper mid-bass range 80-150hz.

Above the bass range, say >200hz, none of this may matter at all, it is quite possible that the perceived increase in tactile feel from small drums and midrange transients are caused by the improvements lower down in frequency, and the perceived improvement in sound may simply be because reflections are reduced.

 

Measuring the velocity gives information about the sound field, which, in combination with spl measurement and other analysis gives better information about what is going on with the sound.

 

To find out what the velocity and intensity means for the perceived sound, one must do controlled experiments.

After building the new front wall in my new room, I can sit down and listen to it, and believe that the tactile feel has improved.

But since it was perhaps several days since the last time I listened, this observation is useless as objective measure of any differences.

Kind of like abx-testing mp3 vs lossless, where you listen to one sample today, and wait 2 days to listen to the other; you would have no idea when asked if it is a or b playing now.

 

But from listening to different speakers, in different rooms, and measuring many of those scenarios, it is obvious that speaker radiation pattern and room acoustics together has huge impact on the perceived sound, and different systems which measure very equal in frequency response can give very different presentations.

[Kvalsvoll]

...

 

Now, to the extent that you can address your early reflection problems on the ceiling and side-walls, you can reduce some of the nulls, and get more energy to arrive in that initial impulse.  I look forward to seeing where you go next with that space. 

 

Building the parts for this now, it will be a very good room above 100hz, what happens with the bass is not so certain, the room layout limits what is possible to do, but there is hope to get some improvement.

[Kvalsvoll]

So you are saying that acoustic treatment has cleaned up the particle velocity field, and that the tactile experience is better as a consequence?  Hmm.  I can definitely see why bass absorption would tend to clean up the velocity field, but I remain skeptical that the velocity field is what's important to the tactile experience.

 

..

 

As I tried to say in the post above, nothing certain - in a scientific perspective -  can be said about the differences in tactile feel.

 

The measurements show huge improvements in decay, and the sound field with 2 stereo speakers is directional across most of the frequency spectrum.

 

An interesting aspect of this is that the front wall receives no direct sound from the speakers from lower midrange and up.

Still, the sound is perceived as better across the whole frequency range.

The decay reveals that decay is improved also at higher frequencies.

This is because the front wall receives reflected sound from the back of the room.

[TTS56A]

Hi Kvalsvoll, i'm very interested how to measure PVL in my room, i'd like to make my own velocity meter. Can you send me a pratical guide to do that? 

Thanks very much!

[3ll3d00d]

Hi Kvalsvoll, i'm very interested how to measure PVL in my room, i'd like to make my own velocity meter. Can you send me a pratical guide to do that? 

Thanks very much!

I'm going to give it a whirl as well. We should start a thread on the subject once up and running to compare data.

[Kvalsvoll]

Hi Kvalsvoll, i'm very interested how to measure PVL in my room, i'd like to make my own velocity meter. Can you send me a pratical guide to do that? 

Thanks very much!

 

I will send it to you in a pm.