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Red Spade Audio

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About Red Spade Audio

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    Melbourne
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    Paul

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  1. I'd call 140 - 400Hz low midrange. Others may define this differently but I'd class midbass as approximately 40 - 60 Hz. I came up with the 120 dB midbass chest thump threshold based on a particular system that I designed and set up for a night club client. It was a 4 way horn loaded system. I found that once the level on the dance floor reached 120 dB around 45 - 55 Hz, you could feel that chest pounding sensation. The mids and highs were lower in level. Of course, using different music or even a system with a different response, you may find a very different result. The details around how you measure can also have a big impact. As a rule, clients don't specify SPL targets.
  2. Keep in mind that if you use high level inputs, this eliminates the chance of using EQ, either from your AVR or an external device. For this reason I'd call it the "last resort" option for systems that have no other way. In the vast majority of systems, it's a big compromise.
  3. When you reach a midbass level of 120 dB, I'd call that the "chest thump threshold." That's the easy part. There are too many variables to give a definitive answer in terms of power/m3. The room in particular adds so much uncertainty. If someone wanted to actually design a system to reach a specific target, it would take a process with several steps. It involves things like testing sub positions and measuring the actual response in the listening position for a known reference. Armed with the right data, I can then work backwards to determine how to reach the target. Power is just one of the parameters. In reality, people don't usually have a specific SPL target in mind.
  4. I've seen this many times in systems that I've tested, it's quite common. I've also seen many cases where the setup wasn't lacking in this aspect but they hadn't dialed in a suitable room curve. I've seen many systems where they actually have more actual in-room bass extension than they realised, yet they didn't have the impression of enough extension. Quite often there is a big difference between what people have and what they think they have. If you are talking about that live concert experience, in which you feel the kick drum thump in your chest, this is an experience very few people achieve at home. Most likely you won't get there if all you do is upgrade your sub. Even the Fathom range will fall short of delivering that chest thump in many rooms. Firstly, most subs lack the necessary fire power. Beyond this, it's also about having the right number of subs for your room, optimising their positions, and correctly integrating them. There are several steps involved, all of them essential.
  5. Enclosure has been picked up ... hope to see some photos!
  6. Pickup organised for tomorrow morning
  7. Further information: FREE! DIY acoustic panels. These came out of a room in which we installed new acoustic panels. Microfibre fabric is wrapped around a pine frame with approx 100mm thick acoustic material, with an air gap behind. These are approx 600 x 1250mm and the depth is around 170mm. Two panels. Given the air gap these should provide broadband absorption that works lower than most. Photos:
  8. Further information: This is a prototype enclosure one of my clients built as a practise run. I designed the sub for Rythmik parts (12" driver with plate amp) but it would suit other 12" drivers of similar size. Net volume is around 55L. Last I checked, the cabinets developed a crack - MDF does not like being left unsealed with machined edges stacked like this. So they need a little extra work. Photos:
  9. In terms of SPL capability, it will be similar to a sealed 12" sub with around 12mm xmax and a 500W amp. The Elac will likely have more midbass output due to greater piston area but in the bottom octave, a 12" with higher excursion can provide greater output where output is excursion limited. The dual opposed mounting of the Elac helps with cabinet vibrations but having drivers firing up and down also reduces the effective excursion slightly over time. The 3D cut away model of the Elac shows the voice coil overhang, which gives us some idea of xmax. For comparison, here is the Peerless XLS, which has an xmax of 12mm. This is a fairly crude guesstimate but this should give a reasonable idea of what you could likely expect. The xmax of a sub driver is the one way excursion, from rest to the out or in position. It can vary from 4 - 32mm + but most are 12 - 22mm. A 15" sub has a clear advantage over both, assuming all else is equal. The 15" needs to be bigger to actually deliver on its potential and also keep in mind that it will also generally be more expensive. Keeping in mind also that some big subs are like power tools - impressive on paper in terms of how much air you can move for the price but not always impressive in terms of getting clean and accurate bass. This is the other aspect of performance.
  10. DEQX have been doing this for a long time. At one stage you had to pay for it but last I heard they offer this as backup support. We've been doing it for around 6 years although more people ask about room analysis and bass integration. I know this urge very well! As I see it, there are two basic categories here: A: Fundemental things you want to get right the first time - set and forget B: Things you can fiddle with forever without messing up the fundamentals If you engage someone then you might have them to do A and then tinker with B. There are many ways you can do that, without having to get them back over and over. If you have a way to tweak the overall shape of the response, that's probably the best thing to adjust to your own taste. I will often show clients how to do this on their own in a way that would mean there is no need for me to come back.
  11. You can do it, but should you? Do you switch between music and home theatre? In many cases, inexpensive subs are designed as ported to meet a certain price point. You can then use a cheaper driver that has limited excursion and power handling - essential a driver more like a woofer. It might only have a 100W amp and tuning around 30 - 40 Hz. Let's suppose you have 35 Hz extension. Block the port and you move this up one octave - to around 70 Hz. In a small room with strong modal midbass resonances, this might actually sound better than the ported version that is able to put more energy into those modes. In some cases, this might actually work, but you are giving up headroom in the process. Now let's suppose you have a more substantial sub that is tuned to 20 Hz. This is quite different. With music, the port will see limited action and in the midbass, the output is coming from the driver, so in this example, the difference is less than you might expect. Seal the ports and this sub now has 40 Hz extension. This is enough to engage the same modes in the midbass as the ported version. If you have a bass problem, plugging the port is usually not the best solution. The tools that work best are position (sub and listening position), bass traps, EQ and filtering.
  12. It sounds like you are talking about two problems: 1. Excessive bass 2. A wall that appears to be vibrating Where you have plasterboard vibrating enough that you can hear it, plaster against framing, bass traps won't help. If you have too much bass for your taste, bass traps typically also won't help. Generally bass traps in the front corners won't sufficiently change the frequency response enough that you would reduce excessive bass. From your description you most likely have some peaks caused by room modes. When you treat a room with bass traps with full range absorption, you get three changes: 1. Bass becomes tighter, with improved decay characteristics 2. The low midrange region becomes cleaner - less muddy 3. The overall reflection levels in the room are reduced - the brighter the room, the most obvious the change Acoustic panels on the front wall can have an impact on the sound stage, especially with regards to depth. It's fairly safe to add bass traps to any room. It's virtually always beneficial, the exceptions being only rooms that are already too dead. However, with full range acoustic panels, not every step is in the forwards direction.
  13. From a sub design perspective, it doesn't matter much, as Dave pointed out. From an integration and aesthetics perspective, it can make a bigger difference than you might think. Moving a driver by as little as 300mm can make a difference. So the position of the driver on the baffle matters as much as it prevents or allows you to get the optimal position. When a sub gets larger, this starts to matter more.
  14. Thanks for the mention Mike. This may surprise you but I'd say of those who call on the phone about acoustics, very few are tyre kickers. I measured a room recently where the entire ceiling had been treated. In this particular case, it was actually too much, resulting in a room that measured more like a studio, but this does show that you can do a lot to tame overall reverberation levels in a room with just the ceiling. Very often the ceiling is neglected in room treatment. It's odd in one sense that so many people consider carpet important, yet don't think at all about the huge untreated ceiling above. The downside with ceiling treatments is that it adds installation challenges. The upside is that you have a very large area that you can treat, usually with fewer obstacles. Going back to your first post where you mentioned speakers, here is something people that often happens in these types of rooms: the speakers often are very close to the wall, either side of a large entertainment cabinet. If you can move the speakers out from the wall behind them, and sometimes the couch a little further forward, this adjusts the ratio of direct to reflected sound. This is a ratio that you can adjust with both treatment and speaker placement. Yes, I know this involves SAF challenges but in rooms like this there is always a conversation in which we try to find the sweet spot. Very often in these rooms you will end up with a more reflective room that the ideal. In many cases we can get a significant improvement with this one adjustment alone. In some cases, you may find you can get a similar result that may have taken twice as much treatment. With this in mind, isn't it worth seeing how far you can push your luck with speaker placement? Now keeping this in mind, you might also think about having speakers that are not too easily toppled over! Before you make any decisions about how to treat a room like this, you need to consider: 1. What specific problems are you aiming to solve? Hint: it's not as simple as reducing reflections. 2. What bass challenges do you have? Some problems you can solve with trial and error - it's not ideal to do it that way but with bass, you really can't. 3. Aesthetics - do you want panels that blend, like say white panels on the ceiling and upper parts of the walls. Do you want panels that could pass as decoration? In a room like this, you might think about both. In some rooms, you can set up bass capable floorstanders and get great bass. In others, there is no feasible speaker placement that will work well for bass. This is where a specific number of subs in specific locations can become the only effective tool to make great bass possible. Here is an example: The black line is how some very large floorstanders measured in a room very much like this one. You can see the speakers still have some low bass output but in terms of tonal balance, the room is out of whack. The blue curve shows the best sub position I found in this room, with EQ applied - yes I know, that's cheating. The sub is tiny compared to the floorstanders but is has the advantage of being able to go in the ideal bass position. This solves the bass problem, but you may also notice, the low midrange is missing. What this suggests is that very often these kinds of acoustic challenges require solutions that go beyond traditional approaches.
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