Re: [Sursound] Construction of purpose built ambisonic studio (J?rn Nettingsmeier)
--On 13 March 2014 07:30 + Dave Malham wrote: > It had an awful focusing effect at > the centre until a brilliant guy in our estates department came up > with a relatively low cost solution which was to get a large (~3-4 > metre diameter) end dish from a beer brewing vessel and suspend it, > concave side facing down, below the centre of the ceiling, near its > focal point, to break up the main modes. The difference was amazing. Just like the flying saucers in the Royal Albert Hall, in fact! Paul -- Paul Hodges ___ Sursound mailing list Sursound@music.vt.edu https://mail.music.vt.edu/mailman/listinfo/sursound
Re: [Sursound] Construction of purpose built ambisonic studio (J?rn Nettingsmeier)
I would definitely second Jörn. We had a 16 speaker array (4-8-4) in a room which was hexagonal (with a pitched roof) that comes out as near a hemisphere as far as audio is concerned. It had an awful focusing effect at the centre until a brilliant guy in our estates department came up with a relatively low cost solution which was to get a large (~3-4 metre diameter) end dish from a beer brewing vessel and suspend it, concave side facing down, below the centre of the ceiling, near its focal point, to break up the main modes. The difference was amazing.- the room was still not really good but it was usable and was far better for it's main use as a rehearsal room, as well. No digital room correction as it was back in the day - analog decoder design by Dylan Menzies, installation of the rig by various masters Music Technology students (were you one, Richard F?, Can't remember now...). Was in use for a decade until the Rymer Auditorium was built and we transferred the speakers and amps over, retired the decoder and replaced it with a digital one. Dave On 12 March 2014 12:19, Jörn Nettingsmeier wrote: > On 03/10/2014 11:50 PM, Steve Boardman wrote: > >> Hi J?rn (not sure what the character '?' is as it always displays >> that way) >> > > an o with double dot. > > the way i approach it is: * keep the early reflection paths clean >>> for every speaker, like you would for stereo. no reflections < 10 >>> ms is a good thing, if possible. * keep the diffuse field under >>> control. off-axis mud adds up as you add more speakers, so proper >>> bass absorption and diffuse reflection in the treble and upper >>> midrange are important. * use mild digital room correction in >>> addition to acoustic treatment, it can do wonders for bass >>> problems, where mechanical measures are difficult. * if you have to >>> make compromises, keep the frontal direction as perfect as >>> possible, and use it as a "magnifying glass" to work on details >>> even if the respective sound later moves elsewhere. >>> >> >> This is interesting, as I have had various opinions on this. Some >> people say that spheres are the best as they have no parallel sides, >> so reflections are reduced. >> > > the center of a sphere is absolutely unusuable. all kinds of weird stuff > from in-head localisation to total collapse of localisation, changing > rapidly and erratically with just a few inches of head movement. > > the curvature of the walls does not mean that reflections are reduced, > only that they are focused towards the center. > there can even be a flutter echo. > > They also only have one room mode, that >> can be predicted and treated. Or not excited (depending on the size). >> > > i'd love to hear a spherical room that is not totally abysmal, and be > proven wrong. but i won't buy shares of your studio when you go for a > sphere :) > > I do know of speaker box technology that uses this thought to it's >> advantage, but I have never considered it for studio construction, >> due to complexity and space. It would also have to be very large for >> the lowest fundament not to excite it! >> > > think whisper gallery. do you want that in your control room? > > I must say, I like dead rooms, although I do agree that they are not >> the best places to work. In fact quite disorientating. Listening to >> ones own body internally is very off putting. As a consequence I >> generally make the front complete dead with absorb-tion materials and >> then have the back handle for reflections via random breakup >> reflectors. Is this still a good idea? >> > > i guess so. my (modest) experience tells me that overly dead rooms often > call for "freshening up" by thin layers of HF-diffusing surface on top of > the bass absorbers... > > A little room correction will of course be needed, especially for >> bass. >> >> an off-the-cuff suggestion: * four subs in the corners. * the >>> fullrange speakers on a horizontal ring, with one speaker in >>> front, for a decent approximation of ITU 5.1 and 7.1, if >>> necessary. * the satellites in a lower ring-of-eight, an upper >>> ring-of-eight, another ring of six, one zenith speaker. then you >>> have two spares, and they will come in handy some day. >>> >>> the bass management will be tricky. first of all, each speaker >>> needs to be perfectly delay-compensated to the listening spot. then >>> i'd try to create different layers of decoding: >>> >>> * separate first-order decode for the subs, low-passed at 60, >>> 24dB/oct * fourth-order decode for everything else * horizontal >>> speakers high-passed at 120/24 * satellites high-passed at 120/24 * >>> a separate horizontal-only decode (of the same full-sphere input >>> signal) for the range from 60 to 120 hz, again at 24dB/oct >>> >>> this lets you drive all speakers to the best of their abilities, >>> and puts the missing bass frequencies in the correct direction. >>> $DEITY help you if anything is not perfectly phase-aligned, >>> though. >>> >>> disclaimer: i'v
Re: [Sursound] Construction of purpose built ambisonic studio (J?rn Nettingsmeier)
On 03/10/2014 11:50 PM, Steve Boardman wrote: Hi J?rn (not sure what the character '?' is as it always displays that way) an o with double dot. the way i approach it is: * keep the early reflection paths clean for every speaker, like you would for stereo. no reflections < 10 ms is a good thing, if possible. * keep the diffuse field under control. off-axis mud adds up as you add more speakers, so proper bass absorption and diffuse reflection in the treble and upper midrange are important. * use mild digital room correction in addition to acoustic treatment, it can do wonders for bass problems, where mechanical measures are difficult. * if you have to make compromises, keep the frontal direction as perfect as possible, and use it as a "magnifying glass" to work on details even if the respective sound later moves elsewhere. This is interesting, as I have had various opinions on this. Some people say that spheres are the best as they have no parallel sides, so reflections are reduced. the center of a sphere is absolutely unusuable. all kinds of weird stuff from in-head localisation to total collapse of localisation, changing rapidly and erratically with just a few inches of head movement. the curvature of the walls does not mean that reflections are reduced, only that they are focused towards the center. there can even be a flutter echo. They also only have one room mode, that can be predicted and treated. Or not excited (depending on the size). i'd love to hear a spherical room that is not totally abysmal, and be proven wrong. but i won't buy shares of your studio when you go for a sphere :) I do know of speaker box technology that uses this thought to it's advantage, but I have never considered it for studio construction, due to complexity and space. It would also have to be very large for the lowest fundament not to excite it! think whisper gallery. do you want that in your control room? I must say, I like dead rooms, although I do agree that they are not the best places to work. In fact quite disorientating. Listening to ones own body internally is very off putting. As a consequence I generally make the front complete dead with absorb-tion materials and then have the back handle for reflections via random breakup reflectors. Is this still a good idea? i guess so. my (modest) experience tells me that overly dead rooms often call for "freshening up" by thin layers of HF-diffusing surface on top of the bass absorbers... A little room correction will of course be needed, especially for bass. an off-the-cuff suggestion: * four subs in the corners. * the fullrange speakers on a horizontal ring, with one speaker in front, for a decent approximation of ITU 5.1 and 7.1, if necessary. * the satellites in a lower ring-of-eight, an upper ring-of-eight, another ring of six, one zenith speaker. then you have two spares, and they will come in handy some day. the bass management will be tricky. first of all, each speaker needs to be perfectly delay-compensated to the listening spot. then i'd try to create different layers of decoding: * separate first-order decode for the subs, low-passed at 60, 24dB/oct * fourth-order decode for everything else * horizontal speakers high-passed at 120/24 * satellites high-passed at 120/24 * a separate horizontal-only decode (of the same full-sphere input signal) for the range from 60 to 120 hz, again at 24dB/oct this lets you drive all speakers to the best of their abilities, and puts the missing bass frequencies in the correct direction. $DEITY help you if anything is not perfectly phase-aligned, though. disclaimer: i've toyed with such hacked-up multiband setups, but none of them ever went to production (or had to), so there may be pitfalls i've overlooked. First order decode for the four subs in the corners was what I was thinking. Didn't think about going to fourth order on everything else though, as I didn't think the increase in channel count was worth the little improvement. I also want to leave some processing power for mixing plugs (I use a lot) :) well, i started from the number of speakers you said you had available. Agreed on the full range horizontal ring. I was more thinking of a dodecahedron for the satellites, either only 20 on the vertices, or get 5 more, and would it be possible to use the edges? you mean you want to create entirely separate horizontal and full-sphere systems? Is it better to use platonic solids, or doesn't it matter? with the recent advances in optimizing for irregular layouts by zotter et al and heller et al, there is no longer a compelling reason to go for platonic solids, except that they are kind of pretty :) layouts based on a horizontal ring have the big advantage of better horizontal-only performance, without much degradation in the 3d case. Thanks again, and needless to say I will be asking a few more questions as I progress. The build won't start for another month, and when it's fi
Re: [Sursound] Construction of purpose built ambisonic studio (J?rn Nettingsmeier)
Hi J?rn (not sure what the character '?' is as it always displays that way) Wow, thanks for al the info! > still holds for ambisonics. try to get as many different room modes as > possible. This is good news, and obviously what I presumed but it is the idea of the same response from each speaker that is threw me off that train of thought. > my setup has its front speakers close to a wall, and the remaining short > reflections are compensated with FIR filters to some degree. the sides > are against a bookshelf and free-standing in the room, with very > different acoustic loading and hence vastly different FIRs. the rears > are wedged between sofas. > > that makes my front direction the most "analytical", and the system > nowhere near isotropic. but it sounds very good. i just know that when i > want to dissect something in detail, i rotate it to be in front. > > unless you can afford a purpose-built room like the (mostly heptagonal!) > listening room at CCRMA (which, despite its very modest speakers, is > quite amazing - goes to show the importance of the room), some > pragmatism is called for :) Yes I think that it still will be front centric, and it seems that having a larger area behind will make it even more so. I actually hadn't thought of the rotation trick, (even though I use it regularly while mixing). That really means I can be a bit more pragmatic with the space. It will be purpose built though, it was just the shape I was having a problem with. It will be completely sound proofed and have all walls treated with sound absorbing materials. > symmetry between left and right of the most frequent listener > orientation is still a good thing. Agreed > central to the speaker system, yes. there is no benefit to being in the > exact center of the _room_, though. i'd go for some front-back asymmetry. Central to the speaker position but not the room would be fine in a cheese wedge space that I have but symmetry of back and front is where it gets difficult, and probably means it isn't such a good idea to have the back higher than the front. Maybe heptagonal is the better, wasted space option > a sphere would be absolutely disastrous, unless it is anechoic, and then > the shape does not matter anyways. and as aaron pointed out, overly dead > listening rooms lack proper masking of interference artefacts and will > be very irritating to work in. > > the way i approach it is: > * keep the early reflection paths clean for every speaker, like you > would for stereo. no reflections < 10 ms is a good thing, if possible. > * keep the diffuse field under control. off-axis mud adds up as you add > more speakers, so proper bass absorption and diffuse reflection in the > treble and upper midrange are important. > * use mild digital room correction in addition to acoustic treatment, it > can do wonders for bass problems, where mechanical measures are difficult. > * if you have to make compromises, keep the frontal direction as perfect > as possible, and use it as a "magnifying glass" to work on details even > if the respective sound later moves elsewhere. This is interesting, as I have had various opinions on this. Some people say that spheres are the best as they have no parallel sides, so reflections are reduced. They also only have one room mode, that can be predicted and treated. Or not excited (depending on the size). I do know of speaker box technology that uses this thought to it's advantage, but I have never considered it for studio construction, due to complexity and space. It would also have to be very large for the lowest fundament not to excite it! I must say, I like dead rooms, although I do agree that they are not the best places to work. In fact quite disorientating. Listening to ones own body internally is very off putting. As a consequence I generally make the front complete dead with absorb-tion materials and then have the back handle for reflections via random breakup reflectors. Is this still a good idea? A little room correction will of course be needed, especially for bass. > an off-the-cuff suggestion: > * four subs in the corners. > * the fullrange speakers on a horizontal ring, with one speaker in > front, for a decent approximation of ITU 5.1 and 7.1, if necessary. > * the satellites in a lower ring-of-eight, an upper ring-of-eight, > another ring of six, one zenith speaker. > then you have two spares, and they will come in handy some day. > > the bass management will be tricky. first of all, each speaker needs to > be perfectly delay-compensated to the listening spot. then i'd try to > create different layers of decoding: > > * separate first-order decode for the subs, low-passed at 60, 24dB/oct > * fourth-order decode for everything else > * horizontal speakers high-passed at 120/24 > * satellites high-passed at 120/24 > * a separate horizontal-only decode (of the same full-sphere input > signal) for the range from 60 to 120
