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Paul Spencer

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  1. It's a mono amp with just under 1kw when using a 4 ohm driver.
  2. Will this crossover work?

    They are useful for spare parts only. Or for blog posts showing why they are a bad idea for just about every combination of drivers and enclosure you could consider! A future blog post perhaps. Here is a crossover that is actually much closer to ideal than most of these types: (Each vertical division is 5 dB) In this example a commercially designed crossover is used but the drivers and baffle edges have been changed. You can see the tweeter is more sensitive, but it's not just a matter of padding it down - the actual slope needs shaping. The mid dome has been switched to a Morel and you can see a hump either end of the passband - those need to be controlled and no textbook crossover will achieve that. The original design would have worked for the original drivers and baffle. The owner attempted to get suitable replacements as close as possible to the originals and had researched the options carefully. So this is actually a combination with more chance at working than a generic textbook crossover board. Full project write up here >
  3. Will this crossover work?

    Is this for a school project? My first speaker project was a school project for Physics class. I did everything wrong but still managed to get an A! Luckily for me, our Physics teachers knew more about physics than speaker design. If you can tell us a bit more about your project, perhaps we can give some more useful suggestions. One of your problems is that a school project will have a limited scope and a limited budget. You will probably find just one small part of this will blow the budget and take a lot of time. If you buy an off the shelf crossover, then consider just buying one and picking up a measurement mic to show how it goes wrong. Or it might be enough just to model and design a ported box. You can also pick up an active crossover fairly cheaply and use your amp to drive just one 2 way speaker. Rest assured any off the shelf passive crossover won't work well for any real world design at all. They use the bare minimum of parts to provide textbook electrical filters. Any half decent crossover is adjusted so that the hand fits the glove. The values move away from the theoretical textbook values to compensate for driver roll off, baffle effects and driver sensitivities. Any good design will also work through some issues that aren't knowable until you have that very specific network of decisions on the table. A smart design might actually do more with less. Sometimes a cap of just the right value does a better job than four parts designed with a textbook filter. (Not for the reasons you might read in the brochure!)
  4. Polymax XHD black acoustic panels

    There are two options: 1. Panels cut to 600 x 800 (which would fit in packing boxes we have) at $26 each (min order 6 with up to 12 to a box) 2. Pack of 6 full sheets as they arrive from the factory (would have to confirm if this were possible) We did end up shipping previously via courier to one of our local customers. It took some convincing to get the courier to take delivery in plastic rather than a packing box which is normally required. We would have to check they would deliver a full pack of 6.
  5. Tannoy Monitor Golds with active crossovers?

    The problem with basic analogue active crossovers is that they are less sophisticated than the passive crossovers they replace. A capably designed passive will usually shape the response beyond what you get with simple textbook high and low pass filters. As a result, they will typically sound better. In order to realise the benefits that Rod talks about in his articles, you need an active crossover that is a good fit for both the drivers and the enclosure. In other words, a custom design. You can do it more easily with MiniDSP, but keep in mind that the skill required to design active and passive crossovers is the same.
  6. You are starting with an ideal situation here, in terms of getting the ideal bass performance. You have a pair of large 18" woofers that could easily cover 30 Hz with some EQ. Once you start taking measurements, you can see if they will help with a smoother midbass response. This might not be on the table, since you might do just as well with a pair of subs in that range. Then it's a simple decision and a simpler set up. Another factor is the EQ requirements to achieve extension. Room gain and room modes are factors here. How low can your woofers go without boost? Or, how low can you go with a modest amount of boost that still retains enough headroom? The real key here is to use the data to help you find the best solution.
  7. 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!
  8. 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.
  9. 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.
  10. Bathurst 2017

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

    Penciling it in
  12. Insulation v's Foam

    There are lies you must tell yourself at the start of any DIY project. Or it never starts!
  13. 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.
  14. Insulation v's Foam

    Compared to drilling hundreds of holes with a large spade bit.
  15. 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!