Paul Spencer

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About Paul Spencer

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  1. 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?
  2. 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.
  3. If buying new, I'd suggest you want to spend $900+. The SVS in the classifieds is a good buy. Replying to the original question: Why a sub for music is a good idea (StereoNET article) http://www.stereo.net.au/articles/6-reasons-to-use-subwoofers-for-music And some help on setting up http://www.stereo.net.au/articles/subwoofer-setup-a-basic-guide Don't forget guys - SNA is more than just a forum!
  4. First thing to keep in mind is that changing the enclosure in any way will divorce the drivers from their crossover. Even small changes like moving the drivers on the baffle or changing the edge treatment - adding roundovers/chamfers or removing a protruding lip. Baffle edge diffraction is impacted by all of these things and it's part of the tonal balance of the speaker. Things which you expect to be an improvement can actually take you in the other direction. There is a lot of room for improvement with the enclosure but to really benefit you need either a modified or completely new crossover. If you don't want to go down that path, then you might be better with a refurb. You can do things like adding rubber/bitumen lining to the enclosure and checking the lining/fill. Possibly also a crossover rebuild. The original caps are electros which you might consider replacing. I recently worked on a Celestion Ditton 66. It's owner had changed the drivers and slightly modified the front baffle. You can see why from the measurements it required a new crossover. Not quite the same as your project but you may find it an interesting read. http://redspade-audio.blogspot.com.au/2017/05/celestion-ditton-66-mod.html With respect to your new cabinets, the main parameter of interest with the bass driver is the net volume. The original has a Q of 0.75. If you make a smaller box, it will raise the Q - this reduces the extension and introduces a low mid hump. If you make the box larger, you lower the Q resulting in a more gradual roll off. Whether this is preferable depends on the room in question. A more precise way to change the bass is with a MiniDSP 2x4 unit. If you have some headroom then you can use it to dial in a different bass response.
  5. Good question. We're about to review the timeline, so I should have a better answer next week.
  6. There is a DIY point source horn kit in the works. Happy to answer questions.
  7. The first question I'd ask is have you done any in-room testing in the bass and low mid range? This can have a profound impact on what actually makes sense as a plan going forward, unless you change houses more often than speakers! You might find that giant coffin speakers actually have poor bass response. It can happen and it's quite disappointing when you get poor bass from speakers that look like they should really know how to rock. Sometimes this is make or break. The next question is what range do you need to cover? This also relates to the first question. Final question. Are you building separate subs or are you classing your larger woofers as subs? Without knowing your answers yet my initial inclination would be to start with subs that are optimised in number and location to cover the range up to 80 Hz. Mostly one or two are ideal for a single chair with perhaps a spot either side as well. (In some cases the left and right positions are close to ideal, then the situation is different). If using subs, then for the midbass, the choice is easier and you can choose a woofer with extended midrange response. It might mean simplifying the plan where a 12 - 18" woofer covers 80 Hz up to your woofer to horn crossover. If covering say 80 - 500 Hz then you could be looking at a fairly compact sealed enclosure with a 15" driver. With a project like this, there is a network of decisions that work together. What we seek here is a synergy in which the final outcome is better than a series of good parts and apparently sensible choices would deliver. In reality what often can happen with projects like this, is that certain goals are pursued at the expense of things that matter more to the final sound. Let's consider what might happen with different choices. Let's suppose you want to avoid separate subs. We already know this could mean a poor in-room bass response, which might not be fixable with EQ. Moving beyond this what are the other implications? With high sensitivity and greater bass extension being the goal, we move to a ported box with a 15" woofer. The resulting enclosure size is now multiplied and we work on the trade off between size, sensitivity and extension. Even with 40 Hz extension, the box is large for a moderate 94 db sensitivity. The larger box requires more bracing and unlike the sealed box (which we could fill), we're now limited to lining the enclosure. Although the woofer might have potential to meet the horn, care is needed to ensure that enclosure resonances don't limit the useful top end extension of the bass driver. We may at this point be adding in further complexity, with a sealed woofer covering the midrange to meet the horn. In other words, a decision to extend the bass response with a ported design can also limit the upper bandwidth limit. A prototype is a good idea for testing. If you are headed towards a 3 way design as shown in your sketch, then the choice of woofer is likely to be quite different. Yet another consideration is SBIR. When a midrange driver is elevated, you may experience a significant floor bounce dip in its passband. It's something to consider with the type of configuration in your sketch.
  8. I once purchased on of these via ebay, intending to replace an old Akai Integrated amp which came out of an old and very entry level system. Much to my surprise at the time, I found it to be a step back sonically. It failed within two weeks and I had it repaired twice, eventually costing nearly as much as a new amp in total. The second time it kept failing on the repair workbench. In the end I sold it for peanuts to someone who intended to repair it. This was more than a decade ago and I'd be even less inclined to touch it now. I replaced it with a Behringer A500 - this is a studio amp with more power, better sonics and costs about as much as getting the NAD repaired. My point being, it's probably not worth fixing.
  9. It's important to know if you are talking about voltage sensitivity (2.83V) or 1W1m. With an 8 ohm speaker, they are the same. With a 4 ohm speaker, parallel adding a second driver increases sensitivity by a further 3dB. If your amp is not suited to a 4 ohm load then you want either 4 or 16 ohm drivers. If your amp is suited to a 4 ohm load, then voltage sensitivity best reflects the real world impact of the second woofer. Yes you are now looking at 2W but the amp will deliver more power into a 4 ohm load. It becomes more complicated when we consider two things. First, amps may vary in the maximum output into 4 ohms. Second, speaker impedance can vary a great deal from the nominal value. If achieving relatively high output is important then in the real world this is also quite a bit more complicated. Some drivers with high sensitivity handle large signals poorly with listening fatigue kicking in long before the maximum theoretical SPL is achieved. It can even happen at 1 watt! But that's another discussion.
  10. You may not have experienced extension flat to 14 Hz in your room. There are two most likely reasons why you may not: 1. Incorrect settings - the controls are quite sophisticated and take a bit more figuring out than most. When I get the chance I will be publishing some measurements showing how they combine. 2. Masking effect of room modes - room modes that add large peaks have a masking effect, which emphasize the midbass at times without supporting the lower bass. This can actually hide the deep bass capability of the sub. This is what 14 Hz extension looks like when measured without room effects: The servo mechanism isn't a band aid. It's a very well engineered and effective solution to multiple challenges.
  11. It's nice to see someone putting their beliefs on the line! It is hard work - that's why it's not often done. It's not exactly the most fun you can have in audio! I think you are making it more difficult than it needs to be. Can I suggest an alternative to make it easier? First suggestion: pick a single track that you feel is most likely to show a difference. Ideally not your favourite track, because you're going to ruin it! Ideally just 30 seconds - 1 minute. The point is to listen in a very disciplined and deliberate way. It's about listening to observe not listening to enjoy. This will be against the grain for most but it's the only way you will get through a well designed objective test and demonstrate you can hear a difference. Next suggestion: run it as an ABX test. It goes like this: 1. Cable A - your wife reveals which cable is being used, either your chosen fancy pants cable or the bog standard cheap as chips IEC. 30 sec - 1 minute. 2. Cable B with the same sample. In 2 minutes you've formed your opinion about what you think you can hear with that sample. If you're not confident at this point, pick another sample. 3. Cable X - now you have no idea which one is in play. All you have to do is say "I think that's the cheapie." In just 3 minutes you have a result. You've given yourself the best chance at hearing a difference. Now repeat at least 10 times. Now you have a score out of 10. Now you're ready to destroy another piece of music that you will never want to hear again. Choose wisely!
  12. Behringer Europower amps are hard to go past for value, flexibility, reliability and power. They will handle 2 ohm loads or bridge one channel into 4 ohms. If you are a serious DIYer then they will serve you for just about any current or future project. However, fan noise and installation are the downsides. Even if you do the fan mod, you are likely to find it's not quiet enough to be in the room, except perhaps in a cabinet with a door. So you are looking at installing them outside the room with long cable runs.
  13. The most difficult rooms I've tested in the bass region are also the most solid, with concrete floor, rendered double brick walls and concrete ceiling. If your room is build like a cave, it will sound like one. These rooms need the most treatment. If you have a concrete floor only with brick veneer walls and otherwise conventional stud/plasterboard construction, that's very different. In considering plasterboard vs rendered brick, the main issue typically is bass. Here plasterboard is the better solution, provided that you don't have rattles and insulation is important. This will help with your single biggest and most difficult to resolve problem - bass. In many rooms with conventional light construction, you can get good bass without bass traps. Above the bass range, you can easily treat either solid brick or plasterboard. By contrast, in a cavernous room your problems will extend beyond the bass into the low midrange.
  14. Tubes are best appreciated in a system that does not need them. Let me pose a different question: what is the best way to deal with edginess? I suggest it's always best to deal with a problem at the source. If you have a problem in your system and you don't isolate the cause, then you end up going around the mountain endlessly, chasing something elusive. That's fine if your hobby is about the pleasure of a shiny new purchase, where every problem is really just an opportunity to buy something new. However, if you want to get that problem out of the way and sit down and immerse yourself in the music, then you want to find out where your problem lies. When you do that, the solution will tend to become obvious. More often than not, the problem of edginess will be related to your speakers or the room. In many cases both. The changes you experience in changing from one quality amplifier to another are much smaller. It's a challenge to set up both a 2 channel and home theatre system in the one room, as they have conflicting requirements. The first thing to do is be clear about your priorities - whether it lies more with music or home theatre. There is a variety of ways you could go about this, each of them with different implications in terms of your music listening and home theatre experience. With your dipoles, the front wall reflection is a major part of the depth of the sound stage. Frank's system is a good example here. One thing I noticed in Frank's room is that you could easily appreciate the difference the diffusers made even when having a conversation in the room. Dipoles don't tend to perform very well with movie dialogue. What you enjoy in music as enhanced ambience and depth becomes vague location of vocals, which doesn't work as well for movies. This is where monopoles behind an AT screen work better. I agree with the direction you are taking there. This arrangement provides you with a few opportunities. One is to use treatment behind the screen without any concerns over aesthetics. It's a good place for DIY treatments. Another is to use speakers that are now ideal for home theatre. Putting them behind the screen means you're not cluttering up the room full of speakers.
  15. How about free tweaks? The first one to consider is speaker placement. It happens so often when I visit a client for the first time. The speakers have been put into one position, going with the first idea they had and nothing else has been tried. Simple things like toe in which I wrote about here in the StereoNET articles section: http://www.stereo.net.au/articles/speaker-toe-whats-it-all-about (if you've never browsed the articles before, take a look!) Sometimes you can improve a space by putting in some things normal people would use anyway. Like a rug - the difference here is that you want to aim for a thick rug and you might consider putting something under it. Blinds, curtains, shelving, furniture - these things all help to create a baseline. These things are the reason why many rooms I go into don't necessarily require a large investment in adding acoustic treatment. In terms of dedicated acoustic room treatment, the biggest amount of improvement for the smallest outlay is the humble broadband absorber. You can start with those cheap raw foam panels on ebay. Ideally I recommend better but if you want something non-DIY on a tight budget, this is what you get. The weakness is that they have limited effectiveness in the midrange region. This is where you notice the difference between taking a crack on the cheap and making a serious improvement. The better choices are either thicker, have an air gap behind or both.