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Red Spade Audio

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    Paul

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  1. Sorry SS, only just saw this, over a year later! I've used glue and screw with construction adhesive in the past. Quad in internal corners isn't a bad idea. If I were doing this now, I'd probably cut a rabbet joint which would then remove the waxy surface at the join. I wouldn't sand it because that's a slow and tedious job. A straight cut bit on the router is also an option.
  2. Ideally it's best to determine which positions with measurements and that informs the form factor you need. There's many ways to approach this, but here's one idea that makes sense for dual HT subs in a small room. Let's say you're placing them in the front corners. Let's suppose your goals are: reasonable enclosure size (<150L) modest footprint (max 400x400) extension to 20 Hz or lower max SPL below 30 Hz (in a HT this really determines the max real world useful output) These goals point towards a 12" ported design. Consider any of the Dayton 12" Reference series. 15" drivers require a larger footprint and a bigger overall footprint. Ultimax need larger enclosures. They tend to suit US style DIY subs - huge ported boxes tuned low in big rooms. So as a starting point, you'd be looking at an enclosure that might be 400 x 400 x 1200, standing up in the corners. Ports then become fairly simple. A pair of 100mm PVC straight ports - about 1m each with no bends. This recipe would work well with Dayton Reference 12" (HF). There's always that risk! Car audio drivers often work quite well for horns but they aren't typically my first choice for a HT sub. Lack of published TS parameters is one issue and often they are less than ideal for a HT sub anyway. Keep in mind that if you use pro drivers with high sensitivity, they require very large enclosures to achieve good bass extension. Quite often twice the volume or more, so you start to move into the same volume you might use with a horn. It's not the first recipe that I'd consider for a small room. When it comes to sub drivers and DIY sub projects, you really are spoilt for choice. Whatever you choose, keep in mind that it's actually other factors that make or break the final result - position, room acoustics and integration.
  3. Generally in a room like that you have excessive midbass above ~35 Hz. This comes from strong room modes here and you are forced to have speakers, subs and listening position near boundaries. Even modest sealed subs will sound impressive in the midbass, where most of the action happens. Below ~35 Hz it's an uphill battle. It's a good idea to first test all your potential positions. Ideally, lock in sub positions before you even look at sub designs. Now consider this. Around 30 Hz, a 12" ported sub has about the same max SPL as a sealed 18" where both have about the same total box volume. Assuming all else is equal. Below 30 Hz, the ported sub has a 6 dB advantage and above the larger driver has a 6 dB advantage in max SPL. This applies fairly well if you are comparing similar drivers, like say the Dayton Reference range. In a small room, the 12 actually makes more sense. You can make it tall to achieve the volume, therefore taking up less floor space. And it also provides more output capability where you need it more in a home theatre. Then again, sometimes it's not just about what "makes sense" logically. Sometimes you just want an 18! Along with Ultimax, also consider Reference series, which is a bit more versatile. Ultimax have higher excursion and generally require large enclosures.
  4. An acoustic difference? If you have equipment that is sensitive to vibration, then isolation is the critical factor. Here the materials and aesthetics are insignificant in comparison to having isolation mounts that are optimised for the weight and relevant frequencies. Here's what many people forget - the rack itself along with the equipment has a direct impact on acoustics. The worst case scenario here is where many people start - speakers sitting on top of a large entertainment unit, against the wall, no toe in, everything crammed together. It looks and sounds crammed in. Now move across to a minimal rack, placed for minimal impact, with speakers better positioned (usually with breathing space on all sides and toe in) ... now this is a big leap forward. It's less about the rack itself and more related to letting the speakers breathe. Very often when the rack is obtrusive, the speakers are forced into positions that hold the system back. There's always compromise in a living room system but when you take this as far as you can go, the rewards can be dramatic.
  5. First question: what are your goals with this project? If your main goal is to dive into the world of passive speaker design and it's all about learning something new, that's very different to seeking a particular outcome. A few things here look a tad haywire! The first is choosing a 3 way passive design. I wouldn't recommend starting with a 3 way design. It's taking on too many problems to solve. For your first few projects, you are best to start with simpler projects. 2 way designs with well behaved drivers. Start with a 1" silk dome tweeter and a 5" or 6" paper or poly woofer. Learn how to measure, model, tweak. This is quite a lot to learn for your first 5 projects. And it's not worth it if learning isn't one of your main goals. Now regarding this project, there are a few challenges caused by the drivers you've chosen. The tweeter has a very limited bottom end and the mid has quite limited bandwidth. The top end is quite ragged and these aspects result in a difficult tweeter to mid crossover. If you really had to work with these drivers for some reason, it's likely you might end up with a more complex crossover and the cost might even eclipse the cost of the drivers themselves. In starting from scratch, it's usually best to avoid these problems in choosing drivers with more latitude ie. tweeters which can cross lower and mids with more useful top end extension. This is one of the easy parts! Yes, you want a sealed chamber for the mid with the woofer using most of the volume. If you want to learn how to design sealed or ported boxes, WinISD is a very easy to use program to help.
  6. When home theatre first became a thing, the industry responded by adapting 2 channel designs. But now there is a growing trend towards speakers that are designed for more ideal cinema requirements, such as: far greater dynamic range due to high sensitivity and power handling constant directivity - where the off axis response is more consistent and treble response is maintained across all seats effortless - free from audible strain at high peak output levels benign impedance loads very low compression Typically this means speakers using compression drivers and waveguides or horns. (Not to suggest that every speaker with a compression driver will mean home theatre heaven). They sound different to conventional hifi speakers in many ways. Very quickly you realise something interesting. All hifi speakers have a sweet spot in how loud they will play before they start to sound strained. We tend to develop a habit of settling on a certain volume that avoids this happening. The interesting part is when you do a side by side comparison with a waveguide speaker. Suddenly you find you can listen a lot louder without any sense of strain or fatigue. It's then you realise how the speakers often impose a ceiling on how loud you can enjoy. The result of raising this ceiling is that now you have a more dynamic listening experience. Regarding sound isolation, one aspect often overlooked is that it's also about reducing the background noise level. You don't just want to avoid disturbing others, you also want to reduce outside noise getting in. This means you also enjoy the quiet parts of a movie more. Are you familiar with the triple leaf effect? It explains why you don't want a triple glazed window, or any part of the building envelope having 3 skins enclosing two air cavities. From your description in the original post, I'm not sure if you are considering a triple leaf design or not. It's critical to avoid this.
  7. Good point - in a nutshell yes, but I'll elaborate a bit more ... Given the way that most people position and integrate subs, one better quality sub is a safer bet. Often the decision is based on a combination of aesthetics/pragmatics and how it sounds initially. Around 80% of the time, there is a better position. It's a multi step process to find it. With one sub, it's already very difficult to find the best position, relying on how it sounds. The sub crawl will often result in a bad decision. The position that sounds best in a sub crawl, without any EQ, may actually be a poor choice. If you are using two subs, the challenge is far greater. It's like driving to work blind folded, hoping to navigate by the sound of traffic and all the car horns blaring at you! You really can't do it without measurements and the right process. The result may be inferior to a single sub, often due to sub-optimal positions and phase related cancellation. Without measurements you may not recognise that this is happening but you will certainly notice the difference when things are fully optimised. Putting a single sub into a room normally yields +/- 15 dB in the bass region. I've seen DIY efforts that worked very well. I've also seen pro jobs that were done poorly. The key point is this: I'd recommend two choices. 1. Buy one sub, the best you can afford and take your best crack at finding a good position, try as many as you can. 2. If you want to go the next step and add a second, keep in mind it will take measurements. That means either a learning journey or getting help. Reminds me of a Karate kid quote. Just after My Miyagi rescues Daniel from getting beaten up, he says: In this case, if you buy two subs and plonk them down randomly, it's not so much that you get squashed like a grape. Rather, it's a missed opportunity. You're almost certainly not getting the improvement that you paid for.
  8. This was more of a general comment, not so much about this year vs last year.
  9. It's not just the grille fabric but also the frame itself. I've tested many different grilles (on/off) and there is usually a big enough measurable difference that the average audiophile could expect to hear a subtle to moderate difference. Most speakers measure better with the grilles off. I've heard and tested many Osborne speakers in different listening rooms. The room is the real offender here when it comes to bass.
  10. The main question is impossible to answer definitively without knowing how all your possible sub positions perform (with measurements). Without some very specific information, it can go either way. Around half of the rooms that I test perform well with just one sub. I recommend one sub where none of the useful positions offer a significant advantage. In this situation, it's better to choose a single better quality sub. The other half of rooms that I measure typically fit into two main groups: 1. Those with no single position that performs well, where a second sub is actually essential. In this case, the decision is easy. 2. Those that can benefit significantly from a second sub, often due to aiming to optimise more than one seat. Here the decision is not so clear cut. SVS SB1000 are value leaders and impressive in what they offer for the price. But they are built to a price and 2000 series and even many of the older models are cleaner and more accurate. This topic of 1 vs 2 comes up every week. Often the take away is "one sub is fine for my room." WAIT! Not necessarily! I think I'm overdue for an article covering this topic properly. A mistake that many people make is buying two subs because they've heard they are better. I've tested so many systems where two actually performed worse. The benefit is not automatic.
  11. SVS and Rythmik tend to use multiple ports that are driven by commercial considerations. One is the need for a product they can sell in reasonable volume - hence they can't be too big. The other is that the bigger part of their market like the option of tuning below 20 Hz. So you might plug one of the ports to get sub 20 Hz tuning. What this does is move the peak in port velocity down lower. What works for 15 Hz tuning with a 16" driver is probably pushing your luck with an 18" driver tuned at 24 Hz. Both the higher tuning and larger driver mean you need more port area for similar performance. Keeping in mind, SVS typically represent sensible design compromises. In an overkill style DIY project, it's a good idea to try to go that next step. Of course, you'll quickly find you hit hard limits, where your ports no longer fit or you simply don't want to make the box any bigger. And this is where you start to understand why some people use passive radiators! A single round port outperforms all other options with the same port area. When you move to two smaller round ports, you have increased the surface area and there is a penalty in performance. With slot ports this is generally a greater compromise, so you need greater area for the same performance. Hence longer ports. Slot ports have thicker walls and therefore also result in a larger enclosure. But they do have practical advantages, like avoiding making the baffle larger to fit large ports and also the way they can integrate with the bracing. Further, you can create some very large flares on each end - much bigger than you can use if you're using a router bit. Each have their place and if you're building it, you will also have preferences around how it goes together. In the example above, it looks like a pro audio music sub, probably tuned an octave higher with higher SPL to mask any port noise. In a home theatre sub, an unflared port like that limits you to around 6 m/s port velocity. When you find your ports starts chuffing at about 90 dB, that's not a happy moment! By far the most difficult is a home theatre port with a high excursion driver and tuning around 20 Hz. Music tends to mask port turbulence and excite audible effects much less than LFE effects on movies, which can happen at quiet points in movies.
  12. Nothing like an overkill project! You probably don't want to hear this at this stage of your project, but the ports will limit the output given their size. In fact, it's possible that turbulence could limit the useful output to less than you would get in a smaller sealed design. A large box with ~18mm MDF or ply needs considerable bracing and this can get tricky when using dual bend ports! Large panels need to be braced in the middle with braces that connect opposing walls. You also need your bracing panels to be braced by each other. If you brace it well, then you need to plan your build sequence with the ports. Now is a great time to buy a dolly if you don't have one and figure out your journey from the workshop to the HT in terms of ramps.
  13. There is an inherent challenge in answering the main question. If we try to form an opinion based on subjective experience, we are comparing more than one thing at a time. How often do we compare the same speaker in a wide vs narrow version? If we really wanted to know the subjective impact of baffle width when all else is equal, it would take the kind of rigorous comparison that is almost never done. If we were serious, we'd take a given passive 2 or 3 way design, with a wide and narrow version and the same tuning. Crossovers would have to be matched quite closely. We'd also have to level match and compare them double blind with a short swap over time. Sounds like a bit of work doesn't it?! And what is the result of all that work? I haven't done this particular comparison but I suspect that many would find this listening test a little confronting. In the sense that you have to resolve the disconnect between things you are certain you can hear sighted, and what you actually can hear when put to the test. I suspect in this case, if the speakers were closely matched in response and level, the differences would be too small to identify. In my experience, the ability of a speaker to image well isn't easily predicted on the basis of baffle width. Imaging is a trick that wildly divergent designs achieve. Ideas like "narrow speakers image better" tend to catch on because they are simple and intuitively they feel like they should be true. Simple and intuitive ideas are easier to market and they tend to spread around easily. I think this is why so many of them are so persistent. The question of wide vs narrow does lend itself very well to a DIY experiment with a DSP crossover and some knocked together cabinets.
  14. Results with DEQX vary from amazing to awful! One of the plots showed a gradual roll off we usually see in a room, which is about 10 dB down at the top relative to about 100 Hz. This usually sounds fairly well balanced tonally and if you were "correcting" that with EQ to flatten out that downward trend, the results are usually nasty - forward, thin, bright, harsh. When you say "too flat" it can mean many different things. Is that above what you meant? There are two main factors here. One is where the drivers are located, which will alter the interaction with the room. The other is the frequency response - larger drivers may simply give you more sensitivity but less extension. Put these two things together in your room and you get a result that may be counter intuitive. You are probably dealing with a lateral depth mode (between front and back walls, along the axis the speakers fire). The good news is that when you resolve it for your chair, it typically also resolves the seats either side as far as that mode goes. In a very solidly built room, it's often not just about the bass but also the low midrange where you may have considerable stored energy. This is where broadband traps and larger absorbers with a decent air gap behind come into play. An average room is +/- 15 dB in the bass range and this room is in that range. I've seen much worse, although the frequency response is only part of the picture. On top of room modes, we also see SBIR, which is boundary interactions based on the offset of woofers to wall/floor/ceiling. Sometimes the speaker position that sounds best will have some SBIR dips that can't be avoided.
  15. Is this a why not project? Or is there a particular reason for using a passive filter?
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