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  1. This paper is brilliant, he is a great engineer. HIs limiting dispersion in small rooms does work if this narrow dispersion is extremely uniform in spectral info. (There are very few devices that can do that) The paper contains information complex enough to be misunderstood if you don't have a good engineering understanding of the principles he's discussing. For example, Constant Directivity applies mostly to horns and wave guides. Constant Directivity does NOT mean uniform response with angle. But he is super gifted guy- and way more educated in loudspeaker engineering than I-so worth reading over and over!. He's also a big proponent of multiple subs, something I believe in and have been pursuing in the pro side. Here's another paper worth reading: ATCWhitepaper.pdf
  2. Right on HI FI! Some of the folks selling speakers don't even know what wide vs narrow dispersion is. They are buying parts, they may not even know what the measurements in their cabinet are. Its easy for us to check them though- just move on and off axis. And if you see a speaker in a store or at a demo super close to a boundary with no treatment on it, you know they don't know. Brad
  3. I have to say what an excellent conversation you guys have going. There is a lot of important stuff being said. Despite the misinformation on other threads online, this one has quite an intelligent discussion happening! There is nothing more important than how you put speakers in a room and the basic idea of dispersion. I know Floyd Toole, he worked at JBL while I was there (but I was in JBL pro at the time). Brilliant guy. I now know Billy Woodman, who is also quite brilliant and reminds me of Floyd. Billy espouses the same set of principles and ideas. The only difference between the two is Floyd worked for Sidney who ran a public company that had to turn a profi and increase stock value; Billy works for himself and can do what does NOT make sense financially to closely follow his engineering goals. Wide dispersion can get you in trouble in tiny spaces. In pro, we'd sort this out via room treatment, but of course at home this is more difficult unless you live alone! The conundrum is purchasing a narrow dispersion speaker to over come terrible room reflections is buying a speaker with the inverse problem of your room. You have bought a problem- one that helps you today but may not tomorrow. This usually does not work out over time as the eventually you move or change furniture or room layout, etc. So sticking with the best engineering practices is the only safe bet, mitigating the less positive things best you can. For example, you're in a glass room- wide dispersion speakers? Seems like maybe you are asking for trouble, but you might decide yes, I'll install drapes to cover the sides walls, drawing them when you listen. If cannot do drapes, I use overstuffed couches and chairs, push furniture to the sides when you listen so they are between my speakers and the glass. Or maybe I buy some 4 inch rockwool absorptive panels and when I listen I set them up and take them down after. Keeping the level low would also help, to reduce the energy being reflected. Obviously not everyone would do that and many would take speakers home to demo in the glass room and pronounce "the narrow dispersion speakers are far far better in my room". By understanding the issues of dispersions and reflections you can make an informed choice and not be mis led by the problems of a space. "Near field monitoring" came about when engineers wanted their own speakers that they knew, in a room they didn't. So reducing the triangle down to a very small one, staying on axis, effectively pushing the walls further away for your speakers and therefore reducing reflection energy really helped get a better result across different [studio] rooms. A number of these mixers specifically did not monitor loud on top of that, and it's almost like isolating yourself to a degree from the room; the low level and very close speakers DO reduce the reflection energy. So hearfeild is now how it's done. Very few records if any records are mixed on the big monitors in the wall anymore. Since most mix engineers are not "house engineers" anymore, working in different rooms all the time is normal. Setting up that small triangle with wide dispersion speakers is the way of studio work now. Brad
  4. Oh and BTW< very few recordings are done with the entire band in one room and include an attempt at recording the entire space. This is how it's done in live location recordings, but not studio. In studio, its individual element tracking 98-99%. Even live performances in the studio are often split up across rooms. Hiromi for example, everyone plays at once to get the interaction going, but they are all wearing headphones hearing the "mix" because her piano is in a different room from the Simon's drums. The image in studio is created by the mixer though panning (a balance control type of adjustment) - like Alan Parsons did on Dark Side. Except Alan figured out how to do front to back panning to get even larger illusions! Brad
  5. Yes, if you deal with the room reflections and have wide dispersion devices you can get that hologram like image. Brad
  6. We generally tell people to create a triangle, using the same distances between the speakers as you are from each of them. When things are right, with few room influences, you can move left to right and front to back within a few feet and it all sounds good. When things are amazing its even larger. When things are messed up you cannot move at all. As you make the triangle larger you may not make a larger sweet spot, you must listen to the results of every move of a speaker location. Its always amazing to me when people place their speakers once and never touch them again. We know that sometimes an inch can make all the difference when interacting with boundaries and furniture. A good habit is to move everything around and experiment. Also, another important idea is you cannot stand in front of your speakers and judge them. Typically vertical dispersion is straight out from the speaker (parallel to the floor) and down 10 to 15 degrees. You need to be below the tweeter to hear that. You need to know the acoustic center of your speakers. So without boundaries, a general answer is (when set in a triangle), "As wide as the mutual full bandwidth dispersion of the two speakers HF devices" - as a maximum. You can look up the dispersion of your speakers hopefully and draw it out on paper. Sometimes, toeing in a speaker reduces the image size, makes a small er sweet spot. Brad Brad
  7. I think the word "spot" is confusing. At work we discuss enlarging the sweet spot all the time, trying to move things around in a room or a studio to get a larger sweet spot. We were in studio yesterday where they had a TV monitor centered between the speakers, severely affecting the image. The point of wider bandwidth with wider dispersion is a larger sweet spot. Someday we'll get the entire living room to be the same. Brad
  8. No, its not a spot where you are, it's where the speakers sound their best, image and response. If that's your seated spot then Hooray! You win the grand prize! Brad
  9. I don't think "sweet spot" has a specific or universally defined value for all. It's a descriptive term adopted by a lot of folks for a wide range of applications even beyond audio. Sweet spot has a meaning in projection video and many other video forms. Having been in loudspeaker manufacturing for a long time, I can tell you that they call the sweet spot where both the image and sound quality are at their peak- directly related to dispersion. This "spot" is obviously greatly influenced by the room the speakers are in. So most engineering based loudspeaker companies do technical measurements of speaker/driver horizontal dispersion at multiple frequencies and vertical dispersion at the same multiple frequencies. These measurements must take place in a boundary free environment, or as close as they can get (JBL's rooftop half space measurements). Once you understand the behavior of a given device you've measured in a boundary free location, it's much easier to predict behavior in the intended environment, like a living room or a recording studio. The microphone used (just one) for measurement must be calibrated to its preamp and measuring device and the combo be dead flat across the measurement band and beyond. Otherwise errors in the microphone/mic preamp/measuring device look like errors in the speaker response. Same with anechoic chambers, they aren't good down low unless they have a very large dimension and measurements down below the useable limit of the chamber are misleading. Almost no speaker manufacturers have access to extremely large chambers and most have no access to a chamber at all. A lot of time is invested by the industry both pro and consumer in "the sweet spot". Brad
  10. When I say "sweet spot" i am referring to the area within a room where the image is intact and the sound quality is at it highest level. Or, where the speakers sound proper. Brad
  11. Comparing the size of a voice to the size of a sweet spot to determine if this larger dispersion is accurate is not the best example. In a proper image, it should sound exactly like a voice, a real person singing from one spot. The sound of the room in the recording, or the instruments surrounding the voice- that could be placed around the voice as the band is arranged by the mixer or placed as the real event if recorded live, these additional elements would give you the clue how large your sweet spot is. If everything is down to a tiny point and voices instruments all appear to be coming form one small spot in space between the speakers, that is not correct. That's what mono sounds like with two speakers. Thats what a tiny sweet spot and poor speaker dispersion will do. A wide dispersion speaker placed well in a reasonable acoustic space gives the playback listener a sense of a single voice in the middle of a larger band- all elements spread out with their own space, with the drums there, the bass over there and the guitar over there. Patricia Barber live shows in NY recorded by Jim Anderson give you that if you have a nice system. Now to be fair, recreating the complete width of the band in the real recording space is not easily possible with a stereo, as the band could be spread out across a large distance as an orchestra is spread out across a stage. For this we need more speakers spread wide in a larger space PLUS additional mix channels - and that brings us to the next level of production: : immersive. Object based mixing is happening for music (the underpinning of Dolby ATMOS or DTS X), I've already attended a mix session or two in LA that were mind blowing. Very exciting stuff! Brad
  12. Exactly! Wide dispersion and linear frequency response makes for a BIGGER sweet spot than would normally exist in a room with boundaries. Brad
  13. Seems like you understood it well. Know that two different sounds added create a third sound which is not like the two it's made from. The reality of off axis response is how the spectral (freq response) content of these reflections is different from the on axis (direct) sound. The total, the sum of these two sources created by your speakers and room together is what you hear from your stereo. So reflections (from your speakers in the room) added to the direct sound (from your speakers straight to your ears with no barriers) is what we perceive as "the sound of my speakers". This is why off axis response is so important. SO the reflections are also delayed as they take a longer path to you as compared to the sound that goes straight from the speaker drivers to your ears. Anything delayed by a longer path to you creates out of phase information that when added back to the original direct sound, will cancel part of the direct sound. if the timing /phase is shifted out of phase exactly 180 degrees it will totally cancel the 0 degree in phase sound. Since the reflections have all kinds of different paths to take to bounce around your room before the land at your ears, they are time shifted in many different ways ( arrive at lots of different times) and will not all be the same delay, they will be lots of different delay times. This means lot of different cancellations, some complete, some partial and some just a little. So if this sounds like a sonic mess, it is! You can easily see that going somewhere where there are few reflections is the best way to evaluate your speaker for its true sound. if not outside, a very large space where boundaries are far away. That's what an anechoic chamber is, it absorbs MOST reflections and enables you to evaluate only the direct sound. All of this is a clear argument for why consistent good off axis response solves a lot of problems in advance and is the best way to design a pair of speakers for our imperfect rooms. Brad
  14. Nice of you to say "insight" but truthfully its just a lifetime of trial and error and engineers who design speakers teaching me the physics of it all. So to try again at this....Many speaker engineers say that to have a larger listening area (ie. expanded sweet spot)you must widen dispersion and have it roll off consistently with angle (the off axis response is more similar to the on axis response). That is why with old horn systems (say the klipsch la scalas I owned long ago) the narrowing dispersion of HF by the horn makes the sweet spot quite small. You cannot fix that, unless you redesign the horn itself. The sweet spot of these old horns may be just a few degrees wide at 10K, and if you sit in the triangle, its okay if you are precisely in the right spot; if you move just a little in either direction, you can hear the HF greatly reduce. For a wider sweet spot you need transducers that have a wider dispersion by nature and less narrowing behaviors. This is why domes where developed, as this dome shape helps reduce narrowing with frequency. The company I work with developed a mid dome, for the same reason. The purpose of that is say in a scoring studio, where there is a very wide mixing console and you have a lot of people all moving around left to right doing their jobs. They all need to hear the exact same content if possible, so they can judge if something needs to be fixed or not. Having perfect image is not critical here, having consistent content over a wide area is. Eventually in our living rooms the off axis information (reflections now) gets summed with the on axis (straight line, transducer output to our ears). Anything out of of phase causes a cancelation. The off axis is bouncing all over the place, it takes a longer path and is therefore shifting in phase compared to the untouched on axis content. We can use absorption to reduce the level of all this off axis bouncing reflection information and this can help. This is why people say you should use absorption at the "first reflection points"- that first reflection is in some ways the most important one. But you cannot absorb all the reflections as it bounces/echoes all over the room, hitting the floor and the ceiling and the cabinet in the corner and the bookshelves PLUS the walls. Since all this off axis reflection content is the stuff that messes things up, its super important to any listener to try and reduce that differing off axis info to improve things. If this off axis content is different in frequency response from the on axis info, the phase cancellations that happen when the two eventually sum together can really screw up sonics. It can not only destroy an image it can completely change the sound of your speakers at your listening position. People bring speakers back to dealers over this, insisting "they suck in my room". The speakers may not suck on axis, but because the reflections are so strong in a highly reflective room, the off axis content is so different from the direct sound ( on axis sound) the sum of on and off axis sounds awful to you. The cancellations are not similar to the on axis info and therefore change the sum greatly. With well designed domes, the dispersion area is wider (sweet spot is wider) and therefore we have more of the content we want and less of the off axis content we don't want. If it the dispersion was perfect, covered out entire listing area, the reflections are the same as the on axis info and these (out of phase) reflections are pretty much the same as the on axis info. This would greatly help image and keep the speaker sounding like it's supposed to. Differing off axis response creates different room reflections which are the enemy to good sound and image. So the two issues are linked: a wider sweet spot (meaning wider dispersion) would usually mean a bigger image and the less the speaker will sound "different" room to room. I am over simplifying a very complex subject, but does any of that make sense? . Brad
  15. Since science shows us transducer dispersion narrows with increasing frequency (ribbons, horns, cones, planars) the speaker designer tries to provide a wider listening area and expand the triangle. Few can sit in a single spot sue to furniture or other reasons (a mix engineer moving back and forth across a console). The better the off axis response the more stable the image is. Off axis response also affects what the reflection content is, so the more the reflection content remains consistent with on axis content, the better the image. So checking response of a speaker off axis is certainly one important aspect of an ideal speaker. Even a wide dispersion speaker is affected by reflections (ceilings, floor, walls) and can fool you into thinking its the speaker when in reality its the room. So the other technique to evaluate a speaker is to listen to it in a very large space with boundaries as far away as possible, so reflections are minimized and the boundaries in your listening space are removed. Now you can hear your speaker with much fewer reflections and off axis tests are pretty clear and realistic. For us at home, taking a speaker outside to the driveway or back yard is a good way to accomplish this. If the off axis is good, the speaker will likely image well over a larger area. If it is not good, getting a great image will be difficult, even on axis when returned to a room with real reflections. Brad.
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