[Sursound] Ambisonic microphone construction papers
Hi All I'm after papers on the construction of ambisonic microphones, particularly; 'A Soundfield Microphone Using Tangential Capsules' by Eric Benjamin. Any papers or pointers on the subject would be most welcome, but higher order microphone construction especially. Unfortunately i'm not a member of AES yet, so can't view on their site. Thanks in advance! Steve ___ Sursound mailing list Sursound@music.vt.edu https://mail.music.vt.edu/mailman/listinfo/sursound - unsubscribe here, edit account or options, view archives and so on.
Re: [Sursound] Calculating speaker placement (Marc Lavall?e)
Message: 4 Date: Wed, 9 Jul 2014 19:48:27 -0400 From: Marc Lavall?e m...@hacklava.net To: sursound@music.vt.edu Subject: Re: [Sursound] Calculating speaker placement Message-ID: 20140709194827.694b2639@telecino Content-Type: text/plain; charset=US-ASCII Hi Steve. You can use golden rectangles (of ratio 1/1.618) to calculate placements of your speakers. You can refer to: https://en.wikipedia.org/wiki/Icosahedron https://en.wikipedia.org/wiki/Dodecahedron https://en.wikipedia.org/wiki/Golden_rectangle -- Marc Hi Mark Of course, but not sure how easy this may be in practice. Would I use the first golden rectangle on the smallest plane, and intersect the others with that. Then use each rectangle corner as a line from centre until it hits reaches a wall and then mark the speaker position? The problem I have is the room has a sloping ceiling, low at front and then high at the back. I would prefer to extend the angles and attach speakers to the boundaries rather than build a frame to hold them, as that would use up space and become an obstruction. It is also easier to attach to walls and ceiling. I was thinking of having the face of a Dodecahedron on the floor. This way there will be less obstruction in the room and I will only have to embed one speaker in the floor (i'm using both the vertices and faces of dodecahedron). Does anyone know of a simpler and maybe more accurate method? Thanks Steve ___ Sursound mailing list Sursound@music.vt.edu https://mail.music.vt.edu/mailman/listinfo/sursound - unsubscribe here, edit account or options, view archives and so on.
Re: [Sursound] Calculating speaker placement (Matthew Palmer)
Message: 5 Date: Wed, 9 Jul 2014 21:35:06 -0400 From: Matthew Palmer palme...@mymail.vcu.edu To: Surround Sound discussion group sursound@music.vt.edu Subject: Re: [Sursound] Calculating speaker placement Message-ID: CA+dOoG1fH-GntUuqGEn02NYROiyubR6L73=ruarmlcu_twh...@mail.gmail.com Content-Type: text/plain; charset=utf-8 Curious what speakers you're using. -- next part -- An HTML attachment was scrubbed... URL: https://mail.music.vt.edu/mailman/private/sursound/attachments/20140709/aae25a55/attachment.html Hi Matthew To start with I will be using cheap second hand Hi-FI speakers. They are Gale Gold Mrk2. I have been collecting them off ebay for a while. The Subs I have are completely over the top from my PA, and are from DB Technologies. These really are too big for the room, so will be replaced at a later date. I have also bought quite a few MOTU 2408 mrk1s that will be feeding multiple 7 channel Denon 3802 amps. These were the cheapest clean power per channel I could find (100watts). They all also respond to the same remote, so matching gains and changing volume is easy! Everything is second hand, ebay is my friend. I did quite a bit of research and listening and I think this set up is one of the cheapest ok sounding, and expandable systems I could find. Ambisonics doesn't have to be expensive, and it is surprising how much better even first order sounds on a crap system. Even stereo encoded ambisonically sounds better compared to stereo on the same system. Well to my ears anyway :) This was the cheapest ok sounding expandable system I could construct on my budget. Eventually I will be building my own array, and not using any brand boxes, but for now this will be a test for the space. I also have 10 Yamaha NS10s (the marmite of speakers:) which may employed horizontally at a later date. They are currently in my soon to be old studio At home I have 8 orb audio speakers and their sub.. All the best. Steve -- next part -- An HTML attachment was scrubbed... URL: https://mail.music.vt.edu/mailman/private/sursound/attachments/20140711/b0564ef6/attachment.html ___ Sursound mailing list Sursound@music.vt.edu https://mail.music.vt.edu/mailman/listinfo/sursound - unsubscribe here, edit account or options, view archives and so on.
[Sursound] Calculating speaker placement
Hi All, After lots of head scratching (and buying more speakers), I have finally decided on a 32 identical speaker set up ( plus four subs) I have decided to base the array on platonic solids. Even though advise on this list has said there is no need, I wanted to be sure of the most accurate angle coverage, and also decoder efficiency. As this is new build, the construction can assist in placement, and I can preserve equal angle coverage. It also means all speakers will be in or against a boundary allowing for greater use of space. I will delay and adjust gain according to distance, and EQ each speaker at the centre to compensate. I want to use the vertices of both an icosahedron combined with the vertices dodecahedron. Effectively the faces and vertices of a dodecahedron. The problem I have is that I need to find the angles from the centre (listening position) to mark a speaker position (within the space), and was wondering what was the best way of doing this? Laser level protractor maybe or has anyone any other methods? Or is it all just a bad idea considering that not many speakers will be at equal distance? As usual all advise is greatly appreciated. Thanks Steve ___ Sursound mailing list Sursound@music.vt.edu https://mail.music.vt.edu/mailman/listinfo/sursound - unsubscribe here, edit account or options, view archives and so on.
Re: [Sursound] Sursound Digest, Vol 68, Issue 10
Hi Jörn (found it:) This all makes sense. I forgot that a sphere would refocus sound back to the centre position. It would probably make the sound more mono! I was concentrating on the least amount of reflections to the listener, from a stereo point of view, with the listener and speakers non central. Of course if the speakers are tangential on a sphere, the sphere will reflect energy back through the centre position. This is probably why it is used to an advantage in some speaker designs, as the driver is never centre, and it is obviously open at the driver end. I will ask you first when shares become available :) A few diffusers at the back will keep the vibe sweet I think, it will also help when I start recording drums Looking back at your speaker positioning, it seems that this set up would be the best (fourth order) set up for what I have. I wasn't planning on having a separate decode for the full range horizontal ring, unless thats a good idea? The less decoding the better I think. It may take a lot of eq to get both sets to sit together, but the full range set is definitely of better quality. Do you think it would still be fine to decode 3rd order to this rig? I think I have been reading to many old papers that obviously push home the platonic solids being the best for decodes. I wish I had explored the idea of 'rings' earlier, I had just presumed that they weren't optimal, even though I had read and seen everyone here talk about them. It just goes to show that It is quite easy to go down a less than optimal path with ambisonics, even though I have been researching or mixing in the format for 3 years! The studio is based in East London, you are welcome, as is everyone on the list. I will post when finished and peeps can arrange off list for a listening session. Kind regards Steve On 12 Mar 2014, at 16:00, sursound-requ...@music.vt.edu wrote: Message: 4 Date: Wed, 12 Mar 2014 13:19:20 +0100 From: J?rn Nettingsmeier netti...@stackingdwarves.net To: sursound@music.vt.edu Subject: Re: [Sursound] Construction of purpose built ambisonic studio (J?rn Nettingsmeier) Message-ID: 532050c8.20...@stackingdwarves.net Content-Type: text/plain; charset=ISO-8859-1; format=flowed 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
Re: [Sursound] Construction of purpose built ambisonic studio (Fons Adriaensen)
Thanks Fons This looks like great space and probably a good goal to aim for. I think the room will have a roughly rectangle footprint now , with the vertical sides tapering out towards the back. The vertical front wall will be slightly angled from the furthest away centre position to the sides.The ceiling will take advantage of the all ready sloped roof at the front, and then be just off parallel to the floor rising all the way back. The back vertical wall will be completely parallel to a fictional wall at the front, (I.e if the front wall wasn't angled at the centre). Haven't worked out listening position yet, as will need to do some calculations, and tests when built, to see which is best for sound and available space. It's always a compromise, but bass traps will be built! I am wondering whether it would be better to get a few more speakers, and go to fourth order, and if so how many more, and would the improvement be that noticeable for a treated space this size? Also although the rotation would provide 5.1/7.1 compatibility for the smaller satellites, it doesn't include the larger 10 of horizontal full range speakers. These are really important to me as they are a speaker that I am very used to mixing on, and need to be included as it will mean less time getting acquainted to. In fact I think the whole system needs to be built around these as they will be the dominant force in my mixing. Everything will be done in HOA but decoded realtime for A/B' ing. Would it be better to replace the head height horizontal ring of satellites with 8 full range ones or add these in between, with a rotation on the same decoder? I would probably always upscale lower orders to 3rd or forth, would this be a problem, or would it be better to have a dedicated sub set for each order? In which case not sure on the best sub set. This is where it will get really complicated! Cheers, Steve Message: 4 Date: Tue, 11 Mar 2014 00:20:20 + From: Fons Adriaensen f...@linuxaudio.org To: sursound@music.vt.edu Subject: Re: [Sursound] Construction of purpose built ambisonic studio. (Aaron Heller) Message-ID: 20140311002020.ga5...@linuxaudio.org Content-Type: text/plain; charset=us-ascii On Mon, Mar 10, 2014 at 09:50:43PM +, Steve Boardman wrote: Stanford's CCRMA room does look (and undoubtably sound) good, but the space below is maybe a bit over board for what I want to achieve, in the space I have. The actual area of the build space is probably around 180 square foot within a bigger space of 700 square foot on two floors. As an example of what can be done without digging holes in the ground have a look a this: http://www.rossinispace.org/. This is at the conservatory of Pesaro, Italy, and the best sounding and most accurate higher order Ambisonics studio I know of. Size should be comparable to your 180 sq.ft. Shape is approximately a square, but with no parallel walls. The space has a very low RT60 down to LF (bass traps are planned but not yet operational), the idea being that in AMB mixes most of the space should be provided by the signal and not by the room (which makes sense, creating virtual spaces is one reason to use full surround). The control desk, shown against the wall in the panaromic picture, can be moved to the center. The speaker system consist of * a ring of six at elevation -33 degrees (ideally this should be -45 degrees, but this requires an elevated listening position), * a ring of eight at ear height, * a ring of six at +45 degrees * a speaker at the zenith. * one subwoofer for a total of 21+1 speakers. This is an excellent setup for third order, in the sense that the decoder matrix is very well-conditioned (it doesn't rely on signals that would cancel acoustically). If you have four subs there's no reason for not using them (put them in the corners, with a dedicated decoder). One thing that could be improved is that the current ring of eight is oriented such that there is no front speaker. The alternative, rotating it 22.5 degrees, would provide a layout that is more compatible with formats such as 5.1 or 7.1. One point not yet mentioned in the replies so far is that for lower order (and in particular first) you should use less speakers. Also for this the rotated ring of eight would be better - the subset used for first order at the moment does not have L-R symmetry. Ciao, -- FA A world of exhaustive, reliable metadata would be an utopia. It's also a pipe-dream, founded on self-delusion, nerd hubris and hysterically inflated market opportunities. (Cory Doctorow) -- next part -- An HTML attachment was scrubbed... URL: https://mail.music.vt.edu/mailman/private/sursound/attachments/20140319/987d6c10/attachment.html ___ Sursound mailing list Sursound@music.vt.edu https://mail.music.vt.edu/mailman/listinfo/sursound
Re: [Sursound] Construction of purpose built ambisonic studio. (Aaron Heller)
Hi Aaron Thanks for your response. What I meant by 'angle errors', was that if the speakers are placed in a different part of the room that was structurally different, the sound waves would not be the same as the any of the others (due to reflection/absorbs-ion phase errors altering frequency/transient response). This can be improved through dsp, but it is never as good as getting it right at source. Maybe 'angle errors' was not the correct term. Stanford's CCRMA room does look (and undoubtably sound) good, but the space below is maybe a bit over board for what I want to achieve, in the space I have. The actual area of the build space is probably around 180 square foot within a bigger space of 700 square foot on two floors. It does have high ceiling though, with an apex over 4 metres (6.8 metres from ground floor to apex). This does dictate to a certain extent the shape of the room, as the room will be built on a mezzanine above the ground floor. This means the 'front' already slopes down to1.80 metres, rising to the back 4.5 vertical wall (that meets the apex). A box could still be constructed though, ignoring the slopes, but as I mentioned earlier this would actually be beneficial in front dominant mixing. I will probably go for a raised listening position to achieve more down positions, although to get a fully central head position standing may be required. I will be very interested in your forth coming paper on partial coverage speaker arrays, as to date I have only used the platonic solids, or only horizontal decodes. Cheers Steve Message: 10 Date: Sat, 8 Mar 2014 20:26:17 -0800 From: Aaron Heller hel...@ai.sri.com To: Surround Sound discussion group sursound@music.vt.edu Subject: Re: [Sursound] Construction of purpose built ambisonic studio. Message-ID: CA+MMR5BuP=iCrgw+YOKhoKkSk=y3rspyu0fjsaj+ezk9+ww...@mail.gmail.com Content-Type: text/plain; charset=utf-8 Steve, I'm not sure I follow everything you're saying about angle errors, but there are a few installations that work well here in the SF Bay area that I have personal experience with. The Listening Room at Stanford's CCRMA is a 3rd-order periphonic facility, described here https://ccrma.stanford.edu/room-guides/listening-room/ The others are in private homes, so I'll let the owners to chime in if they please. They're good sounding rooms, but without special acoustic treatment. (unlike my living room, which is glass on three sides). There are several accounts of Ambisonic reproduction not working well in very dead rooms, such as an anechoic chamber. Also, for 3rd order periphonic you need to place a number of speakers below the listener, which can be a challenge. The acoustically transparent floor in CCRMA's Listening Room is one solution.Eric Benjamin and I have a paper in the upcoming Linux Audio Conference on designing HOA decoders for partial coverage speaker arrays, such as domes and rings. Aaron (hel...@ai.sri.com) Menlo Park, CA US -- next part -- An HTML attachment was scrubbed... URL: https://mail.music.vt.edu/mailman/private/sursound/attachments/20140308/a123ed5c/attachment.html -- next part -- An HTML attachment was scrubbed... URL: https://mail.music.vt.edu/mailman/private/sursound/attachments/20140310/d8afee27/attachment.html ___ 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)
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 hz, again at 24dB/oct this lets you drive all speakers
