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Paul Spencer

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About Paul Spencer

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    VIC
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    Australia
  1. Making multiple sub-woofers work in practise

    Ideally you should keep in mind that many things change, once you know the specific acoustic characteristics of your room. As an example, you may have read it's beneficial to overlap the mains and the subs. If you have just one sub, that means you are now combining 3 sources, which can smooth the response in the overlap region. The benefit of doing so is quite specific. That means it's only a good idea in the precise instance where it provides the intended benefit. Otherwise, there is no benefit and at the same time, you have added a bottleneck in terms of headroom. Another example is the Harman configuration. It works well based on the chosen assumptions involved in the original study. They were looking for the greatest consistency over means seats in a multi-row rectangular room. However, when I work with clients and ask about their seating arrangements, quite often they want to focus on one or two prime seats. If they can get a good result with one or two subs in practical locations, they are often happy with that. With this in mind, actual tests in the room often lead to other sub positions working better than front and back midwall positions. It's not a problem with the Harman paper but rather the reality involved in applying one configuration to a specific room with different priorities and conditions. Typically you won't run the subs higher than 80 Hz, so the benefits of multiple subs are confined to two octaves. The actual experience is greater than this implies. If the bass is right, everything else improves. The low midrange region, from say 80 - 500 Hz is a separate consideration. Quite often studios have this region better under control, with a nearfield setup, some consideration given to boundary interference and treatment that is effective here. When I measure studios, the response is usually much flatter than you ever see in a listening room. Often things in a room, whether dedicated acoustic panels or furnishings, aren't very effective in this range. Here, you aren't as free with placement as with subs. Maintaining a good relationship with the midrange along with a coherent stereo image is key. This will usually be the highest priority. It's a good idea to trial some different positions. See how they measure. See how this impacts the sound stage. It's a trial and error process. Once you've found the compromise you like best, it's then a matter of looking at treatment and calibration. When you have a horn system with dramatic dynamic range capability, if you get these things wrong, it can fail in a big way. When you get to have a listening session and turn it up, a not quite right calibration can stick out and get ugly! But when you get it right and it all comes together, the experience goes to another level ... and you can get carried away, flying high as a kit in your own little musical experience ... then you hear a banging sound. It strikes you as startlingly realistic and life-like. For good reason - it's the police at the door!
  2. How to select sub for a horn system

    Thanks for the mention Matt. When it comes to selecting a sub, the quality of the sub matters. You can go through the right process, choosing the optimal number of subs and positions for your room, treating the room with bass traps for ideal decay and applying EQ for a flat in-room response - you can do all this and still get a poor result, one which does not subjectively sound good, whether for critical listening with music or movies where we might be less fussy. It's a disappointing result where you've done everything right but you are still not getting that tight, articulate, accurate bass you were hoping for. It takes just one weak link in the chain and in some cases, it can be the sub itself. If you decide based on dollars and decibels only, the result might not necessarily be the most satisfying. I've made that mistake and I've worked with clients who have made it also.
  3. Room acoustic help needed in Perth

    Hi Adrian, All rooms benefit from bass traps but it's a decision best made after considering how the room performs acoustically. When you can see the decay performance then you are better positioned to weigh up whether or not you want to add traps. Some rooms have major problems making it a clear choice. Others are already fairly well behaved and won't see significant improvement without adding traps larger than you may accept. You will need to check with your local dealers. Consider 50mm Polymax which is easier to cut and you can simply add two sheets. It also comes in black, which provides extra options when it comes to building your own. DIY acoustic panels are a great DIY project. How easy depends on your DIY skillset and your expectations.
  4. Bathurst 2017

    To anyone new who might be wondering if Graham is really like this in real life ..... YES! HE IS JUST LIKE THAT!
  5. Bathurst 2017

    Penciling it in
  6. Insulation v's Foam

    There are lies you must tell yourself at the start of any DIY project. Or it never starts!
  7. Insulation v's Foam

    And besides ... "this will be quick" is what I always say at the start of a DIY project. Otherwise, I never even start.
  8. Insulation v's Foam

    Compared to drilling hundreds of holes with a large spade bit.
  9. Insulation v's Foam

    Breadknives or Stanley knives need not apply! That's why we cut to size. RF on the other hand is easily cut but the downside is it must be wrapped in fabric. When I get the chance, I will be making some custom panels for my ceiling and rear wall. The ceiling panel with black slats over black Polymax over a black ceiling. The rear wall panel with varnished timber slats over Polymax. These have to be quick builds or they will never ever happen!
  10. Foam panels on back wall

    Creating a profile does two things. First, it reduces the effective thickness, which reduces absorption in the midrange. Second, this only works on the sound which is not first absorbed. So you get a reduction in absorption at the low end mixed with a very slight scattering at higher frequencies. But mostly, the profiles just make them look the part. If you can effectively use diffusion on the rear wall (ie it's not too close) then I'd suggest it's often a good idea. In practice there are many factors not known here which lead to the best way to treat a particular room. The front wall reflection has a strong relationship with the depth of the sound stage and the speakers chosen and their placement. There are many diverse approaches that may or may not work here for different systems. The side walls often get a lot of attention but it's not always the best solution to absorb the side wall first reflection points. In a studio this is much easier to answer. I've had clients who felt that treating side wall reflection points made a big difference. I've had others who preferred the sound without. With monopoles, the front wall has reduced treble and it contributes most notably to sound stage depth, which is also influenced by speaker placement. Generally more treble energy is radiated to side walls and the impact of treatment here is actually different. Side wall reflections contribute more to perceived spaciousness. Measurements are part of the process of working out what works best for a room but if we use a car analogy they are more like the speedo and less like a GPS.
  11. Foam panels on back wall

    If they fit the openings then it's a cheap and easy solution, but not necessarily a good one, for two reasons. First, foam panels around that thickness only work for part of the midrange. They can make a room sound dead by reducing treble reflections without addressing the midrange well. Second, you may not always want to add significant absorption to the rear wall.
  12. Insulation v's Foam

    Foam is cheap and easy to install as it's also very light. For absorption in the midrange and above, it's the cheap easy quick solution. The weakness with these foam panels is that they tend to be quite limited in low midrange absorption. Foam bass traps are in most cases better described as low midrange absorbers. For better performance you want higher density materials like rigid fibreglass or acoustic polyester. Rigid fibreglass is simply a higher density version of thermal batts - it requires covering and it's nasty stuff to handle. In terms of performance it's similar to a high density polyester acoustic panel but polester has no handling issues and you might get away with not wrapping in fabric at all.
  13. The critical factor here is the proportion of sound that is directed towards the front wall. Where a horn radiates less energy it will also have a corresponding decrease in associated acoustic effects. Some horn speakers are not much different in this aspect.
  14. Dipoles have a strong relationship with the wall behind them, so another consideration could be treating the front wall. You can further improve the transparency, alter the precision of the imaging and the size of the sound stage, all at the same time. Or do you just want to try something new and different?
  15. Sound stage

    If you're tired of hearing about sound stage in reviews, the solution might be to stop reading reviews! What does it mean when a reviewer says "the sound stage has improved?" Without qualification, it actually means nothing at all. If they are talking about sources, cables, DACs, preamps and amplifiers then the differences will be relatively subtle. However, if it's about speakers, their placement, acoustic treatment and the room, now it could be much bigger differences. Generally when talking about imaging, it will be about how clearly you can identify an apparent location for each sound. The sound stage will tend to refer to the size of the "acoustic picture." However, it can actually be more involved. For example? Does is bigger sound stage better? Very often, when one hears a bigger sound stage, it will seem like an improvement. For quite some time I preferred open baffle speakers for their larger sound stage. The depth of the sound stage in particular was highly attractive. The downside was that in many cases, this was actually an unnatural distortion of the sound stage. Dialogue became artificially stretched and vague in location. In other words, imaging suffered in terms of precision. With sound staging, we can talk about the width, height and depth. We can talk about the separation, which is not exactly the same thing as simply talking in terms of size. With regards to imaging, we typically are talking about the precision. By far the largest differences you can make all relate to the speakers, their placement, the room and how you have treated it.
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