pinkmouse said:As an employer, you have a duty of care towards those that work for you, (that includes listening panels), so the regulations are relevant and enforceable. In the freedom of your own home you are allowed to do whatever you want as long as it doesn't annoy the neighbours, but not in a work situation, and especially not in the litigious US.
I see
I understand that audibility test requires a listening panel but are members of a listening panel always to be regarded as employees?
What about inviting audiophile volunteers and testing this thing in Your private listening room?
Perhaps some sort of written consent (to be exposed to high SPL) from the members of the panel could be required like in the case of medical clinical tests
But "safety at work" regulations would certainly not be applicable in such a situation.
And after all what we want to check is audibility of the thing by music lovers (or "audiophiles") under normal listening conditions in a well designed but normal listening room and not audiblity by trained employees under laboratory conditions?
Perception of diffraction effects is certainly SPL dependent.
My "unscientific" but reasonable phenomenlogical observations using my own personal "diffracted sound generators" which are wooden exponential horns built about forty years ago and driven by very ancient PA drivers. They produce lots of HOM distortion which is a diffraction product:
At average 80 dB as measured at 1 metre with my Ratshack sound meter they sound "listenable to".
As I increase the SPL the sound quality degrades.
By @ 95 dB SPL they sound really nasty. I didn't bother to play them louder as I'm not masochistic.
The nasty effect is caused by diffraction: When stuffed with reticulated foam which absorbs the HOMs - the only change made to the setup - the horns sound if not pleasant at least "listenable to" at the higher SPL.
My participation in large musical ensembles makes me suspect there may be other kinds of "distortion" of which our perception is SPL dependent.
My "unscientific" but reasonable phenomenlogical observations using my own personal "diffracted sound generators" which are wooden exponential horns built about forty years ago and driven by very ancient PA drivers. They produce lots of HOM distortion which is a diffraction product:
At average 80 dB as measured at 1 metre with my Ratshack sound meter they sound "listenable to".
As I increase the SPL the sound quality degrades.
By @ 95 dB SPL they sound really nasty. I didn't bother to play them louder as I'm not masochistic.
The nasty effect is caused by diffraction: When stuffed with reticulated foam which absorbs the HOMs - the only change made to the setup - the horns sound if not pleasant at least "listenable to" at the higher SPL.
My participation in large musical ensembles makes me suspect there may be other kinds of "distortion" of which our perception is SPL dependent.
Referring back to some early posts (I haven't perused this thread until just now), I have some comments/questions for Dr. Geddes:
"Thus I recommend the use of several subs - as does just about everybody these days since it works so well. Place them around the room - random almost works as well as strategic placement."
This seems to be at odds with the concluisions of the Harman white paper "Subwoofers: Optimum Number and Locations"
( http://www.harman.com/wp/pdf/multsubs.pdf).
As I remember it, it's not practical to improve much beyond a small number of optimally placed (and equalized) subs; even 50 wouldn't do it.
I found parrticularly interesting the opposite midwall placements that cancel odd-order modes between the walls they're placed on, and don't excite the odd-order modes between the side walls.
Have you tried any of these and what were the results?
"To achieve "you are there" when "there" is a room much larger than the playback room, is, IMO, unachievable with two channels (and let's face it this appears to be the standard for some time to come.)"
So why limit yourself to two channels?
Properly implemented surround sound addresses the limitations you mentioned.
As I'm sure you know, the approach is to have a deadish room and have the spaciousness supplied by the surround speakers which are fed extracted recording venue ambience instead of having the room generate it.
"Thus I recommend the use of several subs - as does just about everybody these days since it works so well. Place them around the room - random almost works as well as strategic placement."
This seems to be at odds with the concluisions of the Harman white paper "Subwoofers: Optimum Number and Locations"
( http://www.harman.com/wp/pdf/multsubs.pdf).
As I remember it, it's not practical to improve much beyond a small number of optimally placed (and equalized) subs; even 50 wouldn't do it.
I found parrticularly interesting the opposite midwall placements that cancel odd-order modes between the walls they're placed on, and don't excite the odd-order modes between the side walls.
Have you tried any of these and what were the results?
"To achieve "you are there" when "there" is a room much larger than the playback room, is, IMO, unachievable with two channels (and let's face it this appears to be the standard for some time to come.)"
So why limit yourself to two channels?
Properly implemented surround sound addresses the limitations you mentioned.
As I'm sure you know, the approach is to have a deadish room and have the spaciousness supplied by the surround speakers which are fed extracted recording venue ambience instead of having the room generate it.
noah katz said:
I'm not Dr. Geddes, but for a few years now I have used either 4 or 8 subwoofers in a handful of rooms and I have tried many of the configurations in their paper. Most of the experimenting was done before reading the white paper and my conclusions were very similar. Both the four midpoints and four corners configurations work well in achieving a spatially uniform response, but the four corners gives a lot more output! We're not talking a trivial amount here- usually 6 dB or more. I really do think though that this is very much a case by case thing- you start with some configuration based on the placement of your other speakers and furniture, aesthetics, and a rough idea of how the speakers will excite the room, and then you measure it, interpret the measurements, adjust accordingly, and do over again. Maybe if you had some fancy acoustical modeling software and a very simple (predictable) room you could predict this sort of thing but I have never been in that situation.
SoundEasy provides some room analysis capabilities. Although many people believe in using multiple speakers and equalizers, and it does enhance the ambient effects; however, the transient effects are compromised, and the connection from initial sound and ambient is not as realistic.
Another way of handling the situation is making the room dead as possible, use appropriate delay in other subs not in the main speaker location such that the transient waves arrive at the listener the same time. Ideally one should consider main and surround speakers to reach into the sub region and not have separate subs. Thus when the explosion should come from a certain location, you not only hear the high frquency transient that localises the explosion, but you feel the low transient wave comming from that direction as well.
Another way of handling the situation is making the room dead as possible, use appropriate delay in other subs not in the main speaker location such that the transient waves arrive at the listener the same time. Ideally one should consider main and surround speakers to reach into the sub region and not have separate subs. Thus when the explosion should come from a certain location, you not only hear the high frquency transient that localises the explosion, but you feel the low transient wave comming from that direction as well.
soongsc said:
Ambience channels do not compromise transients, if anything, properly selected ambience enhance attack and dynamics. OTOH a dead room is killing transients and dynamics, or a (small) live room with its ambience is usually only good for a very specific kind of music (LGWG and other audiophile genre).
As realistic as what? Many wide band, low distortion ambience channels make the transition very believable.
soongsc said:
Thank you for mentioning SoundEasy- I usually write my own simulations when needed but after checking this out it looks like a worthwhile piece of software (and not easy to replicate). As far as your approach to LF I'm going to have to think about that and experiment a bit. I guess my experience up to this point has been that achieving perceptual "tightness" or whatever you want to call it (I like to leave "transient" for the technical meaning) is just a matter of achieving a flat transfer function at the listening position. Multiple subs and a little bit of EQ allows me to do this over a moderate sized listening area without too much work or investment into acoustical "treatements." I am curious about the kind of things you might do to damp the low frequency modes- I mean we're talking about absorbers of some pretty serious size aren't we?
noah katz said:
My differences with the Harman paper were noted in a Letter to the Editor (JAES) on this topic. Harman responded with, what I felt were a weak set of arguments. My beliefs remain the same.
I have a 7.1 system in my room. I really like the use of a center channel, but I don't find that the surround channels really add a realistic spatiousness - a good room does a much better job. And lets face it, two channels is the standard (>99% of all source material out there!)
graaf said:
We were testing at a university and they have very strict procedures for human testing which did not allow us to go over 90 dB since this is defined as "potentially dangerous". It can be done, but a whole other level of goverance policies comes into play - so we just stayed below 90 dB.
Rybaudio said:
I agree with your LF approach as this has worked the best that I have found to date. I do like to dampen the LF, BUT NOT the HF. This can only be done with damped wall stuctures - no placed "damper" is going to do much for the LF modes.
The term "transient" and LF don't mix. There is no such thing as a LF transient.
"This seems to be at odds with the concluisions of the Harman white paper "Subwoofers: Optimum Number and Locations"
( http://www.harman.com/wp/pdf/multsubs.pdf).
So why limit yourself to two channels?"
Maybe, or not, something got lost in the cut-and-pasting - the last question in the above quote was in reference to surround sound, not Harman's subwoofer paper.
With which did you have a difference with Harman?
If the subwoofer paper, where might I find your letter to the editor?
Thanks
( http://www.harman.com/wp/pdf/multsubs.pdf).
So why limit yourself to two channels?"
Maybe, or not, something got lost in the cut-and-pasting - the last question in the above quote was in reference to surround sound, not Harman's subwoofer paper.
With which did you have a difference with Harman?
If the subwoofer paper, where might I find your letter to the editor?
Thanks
pinkmouse said:
Just make them pay to listen. Then they are at a "concert" or "club" just like all the other punters who pay to be subjected to 110dB+ all night long.
I would never have been able to make a living in live sound if limited to 85-90dB. Although I can't say it's a bad idea. Why are concerts sooooo loud?
noah katz said:
Perhaps you do need to be a member to view the journals. You SHOULD BE a member. No where else can you find reputable discussions of audio.
There is a JBL badge on the very first slide of that presentation!!!
What you referenced was only the PPT of Todd's AES presentation. The full paper is a lot better. This can be ordered for sure.
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