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Old 18th October 2012, 05:23 PM   #481
Elias is offline Elias  Finland
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Originally Posted by markus76 View Post
Put a sub directly behind your listening position at shoulder height and get a frame of reference what good low frequency reproduction sounds like.
But I don't like the bass inside my head. The sound will be between my ears. It's similar to headphones. Sounds very unrealistic.


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Old 18th October 2012, 05:29 PM   #482
Elias is offline Elias  Finland
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About the Barleywater's results, it is possible to calculate inverse of the room impulse response and approach ideal impulse. I've done this numerous times. But it is valid only in one point is space. I thought it was obvious ?


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Old 18th October 2012, 05:31 PM   #483
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But I don't like the bass inside my head. The sound will be between my ears. It's similar to headphones. Sounds very unrealistic.


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Did you ever try it? Bass won't be "inside your head".
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Old 18th October 2012, 05:39 PM   #484
Elias is offline Elias  Finland
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Did you ever try it? Bass won't be "inside your head".
Yes. Maybe not in yours but it is in mine.

This is also what Griesinger explains about bass externalisation, as without interaural fluctuations there will be inside the head locatedness.

Apparently there is no fluctuations in the nearfield bass since the sound remain inside my head.
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Old 18th October 2012, 05:42 PM   #485
puppet is offline puppet  United States
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Try it Elias ... the right channel Uframe woofer in my system is located about 3' behind my right shoulder along a 45* angled wall. It's elevated about 36" AFF. Don't even know it's there most of the time. Doesn't put bass into the head.
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Old 18th October 2012, 05:45 PM   #486
Elias is offline Elias  Finland
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I could add to my previous post the sometimes I got inside the head bass with a monopole bass as well. After moving to dipoles I don't recall it ever happened again.

It must be because the signal modulations are reproduced better with dipole bass so apparently the interaural fluctuations are introduced.


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Old 18th October 2012, 05:47 PM   #487
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Yes. Maybe not in yours but it is in mine.

This is also what Griesinger explains about bass externalisation, as without interaural fluctuations there will be inside the head locatedness.

Apparently there is no fluctuations in the nearfield bass since the sound remain inside my head.
How did the near field configuration look like?

Don't know what specific paper of Griesinger you're talking about but his stereo bass "installation" creates such "fluctuations" just at one or two single (!) frequencies. That should be the one and only reason for externalized bass?
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Old 18th October 2012, 05:48 PM   #488
Elias is offline Elias  Finland
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Try it Elias ... the right channel Uframe woofer in my system is located about 3' behind my right shoulder along a 45* angled wall. It's elevated about 36" AFF. Don't even know it's there most of the time. Doesn't put bass into the head.
And where is the left channel located ?

It sounds like you have very unsymmetrical system, which in itself can generate those fluctuations.
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Old 18th October 2012, 05:58 PM   #489
Elias is offline Elias  Finland
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How did the near field configuration look like?

Don't know what specific paper of Griesinger you're talking about but his stereo bass "installation" creates such "fluctuations" just at one or two single (!) frequencies. That should be the one and only reason for externalized bass?
Like you suggested single mono bass behind the head. If you stop and think about it, and recalling that we are talking about near field so room effect is diminished, it will generate identical ear signals so the only change for perception is inside the head. If there would be reflections like in a natural sound field the bass will likely be externalised.

It also depends somehow on the signal as well. In some recordings there might be reverberation down to bass range which helps in this matter. I remember synthetic bass was the worse stuck inside the head all the time.

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Old 18th October 2012, 06:00 PM   #490
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Interesting discussion!

I've always wondered about the transmission of sound at low frequencies. At higher frequencies (above the Schroeder-frequency) I assumed it would be mainly a function of radiated power, but at lower frequencies I would assume standing waves play a role: at frequencies where there are standing waves, the pressures at the room-boundaries are the highest and thus walls would flex more and there would be greater sound-transmission. Of course this is all ignoring the mechanical/acoustical properties of the room boundaries. Could anybody fill me in?
Do a web seach on TL measurement (Transmission loss versus frequency) or STC measurement (sound transmission class, the single number rating of walls as a sound barrier). Since the transmission loss definition is power transmitted vs. power impinging on the wall the measurement and calculation is a little complicated.

The acoustical testing facility will have a large reverberent room that they will bisect by building the sample wall. Generally they will measure reverberation time on the noise source side and also on the receiving side, typically at 3 spots in each room. This will allow them to calculate the absorption present in each room. Knowing SPL and absorption they can calculate acoustic power in each room. That allows calculating the difference (in dB) or the ratio in powers which is the transmission loss.

The acoustics of each chamber is key. For example, if your neighbor has fairly dead acoustics in his room then the sound power that makes it into his space will not build up to as high a level as it would if his space is reverberent. So a wall rating isn't as simple as dB on one side vs dB on the other.

For the particular case of having standing waves in the transmitting room, then yes, transmission will be higher for frequencies where the pressure at the wall is maximised by the standing wave. I don't recall any acoustics texts going into that, but be aware that the industry is primarily concerned with voice frequency transmission and very low frequency measurements (below 125) are seldom given. This is changing slowly with the popularity of home theater.

There is lots of info on the web on wall construction to achieve a needed STC. Mass is key and many wall systems follow a mass, compliance, mass ideal with staggered studs or flexible straps to give decoupling between the inner and outter layer. Resonances are also an issue with TL heavily degraded by coincidence frequencies or panel resonances. An ideal limp mass barrier would have maximum TL in proportion to its mass, with a 6dB per Octave characteristic (higher at mid frequencies) and would be resonance free.

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