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Kvalsvoll

Bulding the Room2 listening room

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Kvalsvoll    71

And I'd love a pointer to a thread (couldn't find the one you referred to) on a velocity measurement kit to build or device to buy.

 

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

 

I can send you a description on pm, the one that several others already have received. I just do not want to put it out in the open.

 

Don't worry about OT, that decent audio forums are dying is far worse. And this is on-topic enough, just today I have set up, calibrated, measured and listened to 4 different bass system configurations in Room2.

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Kvalsvoll    71

Sorry to take it off topic with the sound velocity meter but I really didn't as I've noticed what you described above as well. Why does a 12" midbass have more impact than a 6"/8" midbass when played back at the exact same sound pressure level? I've asked multiple times, at least on AVS and I haven't ever received a satisfactory answer. I was hoping measuring the velocity would help point me in the right direction so I can understand this phenomena better. If you have ideas on the physics, I'd love to hear it.

 

And I'd love a pointer to a thread (couldn't find the one you referred to) on a velocity measurement kit to build or device to buy. Purchase depends on cost as well as if that will help me understand this size difference better. Thanks.

 

Exactly. The question is not IF the larger driver sound different, the question is WHY. Once that is established, we can move on and try to learn and find out what is going on.

 

I think there is at least two different causes at play here.

 

One is size of radiating area - the larger couples better to the air and creates sound with more intensity.

 

But capacity is also important. Even if they play at same spl, the smaller driver can be at its limits, causing dynamic compression of transients. This will not be audible as distortion before you turn it up much , much louder. But the peak level of the transients are missing.

 

I believe size is important from mid-bass and up into the midrange. At very low frequencies the size of one radiator is very small whether it is a 6" or a 24". But if you have 2 subwoofer units, they combine, and create a very large radiator together. If each of those units are very small, that does not matter.

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Kvalsvoll    71

... a velocity measurement kit to build or device ...

 

@dgage, I sent you a pm several days ago with this, I saw today you may not have read it yet, you should be able to see it in your Inbox.

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Kvalsvoll    71

One day I may elaborate some more on the velocity measurements - what is it useful for, what can you see and what is still missing.

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Kvalsvoll    71

What can we see from the velocity measurements.

In addition to the normal spl we can get more information about what is going on when measuring the velocity. We can see the direction of the sound, resonances that does not appear on spl, cancellations of sound intensity.

Ideally, the v should match the spl across the whole frequency range. If we measure outdoor, we see that this is the case when there are no reflections or standing waves or room modes present.

In a room and with multiple sound sources, this changes dramatically. Here are 2 examples from the same room, 2 FL FR + bass system cf 120hz.

System with 2 V80 bass horns up front, spl and velocity in on-axis direction:

598a1e441830d_System12xV80front.png.b7e20b1f7dd628432c0d7914d6828fce.png

 

System with 2x V6030 behind, almost nearfield:

598a1e4d74688_System22xV6030backnearfield.png.2a645cf55061b231ce9605e09ca1d2da.png

 

We can see that the velocity does not follow spl at low and low-mid frequencies. This is caused by room acoustics and subwoofer locations.

The 2. has better v at very low freqs, and there is less v around 100-200hz. This may actually be due to the sound waves from the front main speakers meeting the same phase sound from the subwoofers located behind, causing v to cancel out while spl looks good.

 

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Kvalsvoll    71

Looking at v in 0 (on-axis), 90 (sideways) and h (vertical) directions gives information about the direction of the sound.

Direction reveals where reflections come from, and indicates the intensity of the sound. High intensity sound is directive.

Here we can see that the 70hz spl dip is caused by reflection from the ceiling, because h direction v has a top in this same range.

Up through lower midrange the sound field becomes more directional and resembles the outdoor free-field situation.

Above 1K the measurement device is no longer valid.

At low freqs the velocity drops, and that is not a good thing. But there is not much that can be done with that, unless one is prepared to do structural changes to the listening room - moving walls, closing off the open side wall door. For music it does not matter that much, and the low bass (<20-30hz) is experienced as airy, powerful, tactile. Sound intensity is the vector product of velocity and pressure, and there is plenty of energy to move the floor enough to create the necessary tactile feel.

Sound intensity is what drives tactile feel, and vibration of objects. If we eq this spl response to flat - such as removing the 70hz dip, it will not sound more flat and balanced, because we induce too much velocity and intensity in the sound field in the range that already has a velocity resonance.

598a2383a9fed_System12xV80front090h.png.dfd8ca3fccec37fc153aa27eb957d4ae.png

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Kvalsvoll    71

System 2 with subwoofers units located behind - spl is more flat, it does not extend very low, velocity is very different.

V6030 is tuned much higher, so it is limited to around 25hz, and the placement is very bad for low bass.

We see the v at low freq is much better, overall the v is higher in the bass range. This is expected, the units are quite large acoustically, so you are actually in nearfield in the listening position.

We observe the same vertical 70hz resonance, so moving the subwoofers did not change the room. Some effects are due to the room-listening position interaction - will not change, others are caused by speaker boundary - changes when speakers/subs are moved.

100-200hz there is a dip in v, this would have to be investigated further to make this into a resonably good sounding system. First would be to find out what cause this, a new meas with fronts off would reveal if it is the interaction between front and subs causing the problem. It is not spl, phase, timing related (which you would see if you have the .mdat).

This system does not sound good. You can easily hear bass coming from behind, and even though the tactile is quite strong, it does not feel right, something is missing, and it does not sound well integrated and coherent.

Can you hear direction of bass? No, not below around 100hz, but the subs on cf 120hz will emit sound much higher up in frequency.

Can you feel direction of sound? No, and yes. Very close to the sound source you can feel it, and I conclude due to the velocity and intensity being higher on the side of your body facing the sound source - now we are talking about sound that has so large velocity that it actually feels like wind on your body. Direction in itself is not perceivable, and once you get reasonably far from the source, you can not detect direction.

(image hosted on my web)

System%202%202x%20V6030%20back%20nearfie

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Kvalsvoll    71

Seems I have posted too much, there is a limit to attachment uploads so I can not post the graphs. Solved by hosting images on my web.

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Kvalsvoll    71

Different subwoofers up front gives a different result. Swapping the V80 units for very small V6 shows no significant reduction in velocity when the sound source now is half the size acoustically.

The difference in response (spl) and velocity are mostly caused by different location of the sub units, and the smaller ones roll of much earlier.

At louder spl levels it is obvious there will be a difference where the larger V80 has the advantage, but the V80 system also sounds better at low volume. Having a large system makes sense even if the capacity is never put to use.

System%203%202x%20V6%20front%200%2090%20

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Kvalsvoll    71

The Room2 is a test and demo room, but it is also where I listen to music most.

So I want to share with you what music I played in a short listening session this evening, music examples are something I always find very interesting and useful, so perhaps someone finds inspiration for new things to listen to. I suspect many of you have never heard about none of these.

 

1. Voices of Music - La Folia.

The long 10 min one, with the dancers. The F2 speakers allow for a little louder master (-3dB) than you would experience in a live performance for this sort of music, but that makes the realism better, especially when the dancers stomp the scene floor - the recording is full-frequency-range, so you actually feel the scene floor moving.

2. Voices of Music - La Folia.

A different version.

3. Flashbulb - Piety of Ashes.

New release, only one track available as preview. Excellent, this is something quite different from the baroque ensembles. Master 0dB.

4. Flashbulb - Soundtrack To A Vacant Life, tracks 4, 5, 6.

Excellent music, excellent production. This is electronic music, with a complex and detailed sound landscape. Bass is physical and tight. Master 0dB.

5. Jøkleba - Jøkleba!  Nu jøk - Girl, Firefly.

Jazz. Very dynamic recording, heavy and tight punch from the large drum, trumpet so present and rendered with such clarity you can see the fingerprints on the brass. Master +3dB.

6. Daniel Herskedal - The Roc - 07 The Afrit, and 08 There Are Three Things You Cannot Hide; Love, Smoke And A Man Riding On A Camel.

Jazz. Herskedal experiments with his tuba and creates a musical journey. Again - bass is physical, and the drums has this realism you otherwise only get at a live concert. Master +3dB. 

7. Hadouk Trio - Utopies, Shamanimal Live.

Jazz. Here the V80 horns excel in rendering the deep, powerful bass tones. Master +3dB.

8. Jøkleba - Jøkleba!  Nu jøk - 16 - Schopenhauer.

One last jazz track. Master up to +6dB for a truly visceral experience on this relaxing masterpiece.

 

The music can be found on Bandcamp and Tidal. Voices of Music on youtube unfortunately, make sure to get the best possible quality on the audio stream.

Current equipment in Room2: F2 main speakers and 2x V80 compact horn bass-system.

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