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almikel

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About almikel

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  1. Hi @andyr, This is all a bit off topic for the thread so apologies to @Peter the Greek... I've had no experience with Maggies, or any other dipole speaker. I haven't seen him here for a long time, but @gainphile has a lot of experience in dipoles, as does @aechmea , who runs Maggies also. I would agree that diffusion provides the most benefit above the transition zone in a room. Below the transition zone where modal behaviour takes over, you need to deal with the modes - however that may be. In your case I think running some diffusion behind the speakers would assist getting your sound stage depth back, but I can't really comment on how low they need to diffuse, and hence how deep the diffusers need to be in your specific case of getting your sound stage back with your Maggies. Sound Stage Depth (IMO) is something pretty rare these days with the usual approach of close miking everything during the recording process - to me Sound Stage Depth is the ability to place instruments and vocalists on a stage - singer at the front, drums at the back etc - very much captured in the recording (and not many of them due to close miking, and artificial pan-potting) - are we talking the same thing? Given you're considering diffusion behind the speakers, and a lower diffusion point of say 500Hz, then provided the LP is >2m from the front wall, diffusion artifacts shouldn't be an issue (> 3 wavelengths away). The "minimum seating distance >3 wavelengths of the lowest frequency diffused" guideline comes from Cox and D'Antonio - these guys know diffusion - but it specifically applies to "old school" 1D and 2D QRD diffusers. Note that "new school" diffusion, such as the Metasurface diffuser, will reduce the depth of the diffuser (a good thing), but not change the "minimum seating distance". Cox and D'Antonio also invented the Binary Amplitude Diffuser (BAD) - both 1D and 2D. BAD diffusers don't generate the "quality" of diffusion that a QRD does, but because of that, the minimum seating distance is not as stringent. 1D BAD diffusers particularly interest me, as they're easily implemented as just slats/gaps over absorption in a random (eg an MLS sequence) pattern - but I've been too lazy to build one yet. If you wanted to try "higher quality" diffusion behind your Maggies I'd recommend a 1D QRD panel behind each - expensive to purchase and relatively hard to DIY. QRDude is an amazing free design tool for 1D and 2D QRD diffusers. http://www.subwoofer-builder.com/qrdude.htm This is "old school" diffusion - the Metasurface diffuser that's the topic of this thread is "new school" diffusion. Given you heard a significant improvement in your old room with the DIY Room Tunes device, you could try a simple 1D BAD panel approach behind the speakers - more diffusion than Room Tunes, but less than QRDs - BAD panels are also "old school" diffusion, but newer than QRDs. How wide you need to go depends on the rear radiation pattern of the Maggies - but given 1D BAD panels don't diffuse as well as 1D QRDs, I would go wider with BAD panels. The full width of the front wall in an MLS sequence BAD panel would look very cool, but I'd experiment with some smaller panels first. cheers Mike
  2. IMO any absorption targeted at lower frequencies is beneficial - so yes half height is better than no height yes, straddling means across the corner Absorption works best where the air velocity is highest - at a boundary (wall) this is theoretically zero (but pressure is maximum). Air velocity is at a maximum at 1/4 wavelength from a wall/boundary - at 100Hz, 1/4 wavelength is 0.86m (velocity = frequency x wavelength, where the velocity of sound is 344m/s). The bad news is that to trap down to 100Hz needs large traps. The good news is that you don't need the air velocity to be maximum for absorption to work (86cm away from the wall for 100Hz), but some air gap behind the absorption will help it absorb lower in frequency (hence straddle corners). Why straddle corners if targeting lower frequencies with absorption? Below 300Hz or so in your room, room modes dominate the sound - not your speakers. Every room mode terminates at a boundary/wall - you get a pressure maximum and a velocity minimum at every boundary. Take the front wall and the floor boundary as an example - you get the floor to ceiling modes and the front to rear wall modes terminating at this corner. Take the front wall/floor/left wall boundary tri corner as an example - you get the floor to ceiling/front to rear wall/left to right wall modes terminating in this tri-corner - all with zero air velocity and maximum pressure. This is why people say "bass collects in corners" - it does - but the corner has maximum pressure and minimum velocity - not ideal for absorption, which works on velocity not pressure. Your ears work on pressure - which is why the bass is always loudest at a wall - shove your head into a tri-corner for maximum effect! The key with straddling corners with absorption is that away from the boundary, velocity is >0, and you target multiple modes - floor to ceiling absorption in the front corners covers 4 tri-corners and 2 wall/wall corners of the total of 24 corners in a room. Half height absorption straddling traps in the front corners still covers 2 tri-corners and 2 wall/wall corners. If you can get away with the same in the rear corners, you will have achieved the same result as going full height in the front corners. IME when targeting lower frequencies with absorption, it doesn't matter which corner you straddle. Mounting is more difficult, but wall/ceiling boundaries are good options Dead areas behind couches straddling floor/walls also if you can get away with couches off walls. How much absorption is required to get your bass under control is room dependant and needs a measurement rig. Issues below 100Hz or so IME are best dealt with using EQ rather than absorption - absorption simply gets too large to manage below 100Hz - "pressure" traps rather than absorption can work here, but I've never found the need in my "lightly" constructed room, where really low bass just passes through my walls. @125dBmonster has experience in achieving the best room response I've ever seen in a room with "rigid" walls. Getting the "bass right first" is a process I firmly agree with, and something I've learnt from others on this forum, primarily @Paul Spencer Paul's "Bass Integration Guide" parts 1, 2 and 3 are essential reading IMO - part 1 linked here: http://www.hifizine.com/2011/06/bass-integration-guide-part-1/ Having followed Paul's guidelines "mostly", I'm very happy with the sound in my room - bass is tight and clean - I often tweak the treble down on some tracks, even with a lot of absorption in my room, I don't find my room "too" dead - refer the pictures below - IME even with a lot of absorption I still tweak the treble down often. My room has bass "reasonably" under control - it's lightly constructed after all - and I often tweak the bass up, as good clean bass becomes a bit addictive. I listen in other spaces (cinemas, live venues, friend's rooms, cars etc) and I'd like to turn the bass down! I have a dedicated room, and aesthetically it's very ugly, but it sounds damn fine - and my wife agrees that the sound in the room is amazing - fortunately I had a 2 week period where I removed all treatment from the room (sold it off) and had the room "naked" - in her opinion the room was "unlistenable" without treatment and hurry up and put the treatment back! At the time, I had already purchased new bags of Acoustisorb 3, and they were sitting in the garage waiting to make "proper" bass traps - in a few minutes we dragged the bags of Acoustisorb 3 into the room and transformed the "in room" sound - it's remained pretty much the same since - ugly but effective. For reference - a "bag" of Acoustisorb 3 is 3 sheets of 1200 x 2400mm x 75mm poly insulation - I bought 4 bags they all went into the room, which looks pretty much like this That's my sub against the left wall (a large tapped horn) with 2 sheets of Acoustisorb 3 leaning against it. The absorption works well down to 100Hz or so, and below that EQ works fine in my "lightly" constructed room. The mid bass especially (say 80 - 250Hz) is clean and punchy - you feel that hit in the chest with the right track - no bass overhang or bass "bloom". Due to a leaky room (bass wise), add some EQ below 100Hz based on room measurements and great bass is achieved! Difficult to tell from the attached photo, but I run a horn top end (PSE 144's) with Acoustic Elegance TD18s as mid bass underneath plus the tapped horn sub - EQ is via DEQX. It all integrates pretty well into the room, but I don't need to grapple with a shared space. In summary: target treatment at fixing bass 1st - you may not bother with other treatment afterwards below 100Hz use EQ not treatment a measurement rig is a great tool for making decisions regarding treatment cheers Mike
  3. this is not correct - the smart guys on this forum were cutting me some slack... Below the transition zone/Schroeder frequency in a room modal behaviour dominates down to the lowest room mode (longest room dimension = 1/2 wavelength), and you get peaks and troughs in sound pressure within the room based on the room dimensions - imagine dropping a pebble into a fish tank and after a few seconds you see all the reflections off the sides combining - this is how the sound behaves in the room in the modal zone. Theoretically putting a diffuser designed to work that low into the room should have an effect, and may be beneficial for room modes, but I expect the usual guidelines suggested by Cox and D'Antonio of minimum seating distance from a diffuser would apply (>3 wavelengths for the lowest frequency diffused) to avoid hearing "artifacts". This would be difficult to achieve in typical "small" rooms. On the plus side though, assuming you were targeting modal frequencies, if you could get them far enough away from the LP to avoid the "artifacts", you would have flexible placement options, as other than "distance from the LP", it shouldn't matter much where in the room they went. You need to drop below the lowest mode in the room to enter the pressure zone, where there is no direction in the sound wave, and the speakers are pressurising and de-pressurising the room. just not factually correct - apologies! Demonstrably not! cheers Mike
  4. sorry - no I use DEQX for EQ cheers Mike
  5. rugs and thick drapes will further assist at the higher frequencies - too much absorption in this area can make a room "too" dead - but I don't think you'll get to that point with rugs and drapes. The window between the speakers will act like a bass trap - that's good - a thick drape will make it better. Beyond that my suggestions would be unlikely to get approval - as my approach with treatment starts with treating the bottom end - and absorption gets large at those frequencies, and I've never attempted to make absorption "look good". The 2 rear corners behind the speakers are crying out for floor to ceiling Polymax XHD 100mm deep (200mm better) straddling the corners (say 600mm wide) with a nice printed fabric covering them That would make a big difference to bass response down to 100-120Hz or so...with a printed design fabric covering could you get that approved?....unlikely I have a dedicated room that's seriously ugly, but the wife loves the sound in the room - no way would she put up with it in the lounge room, but she completely understands the effect the treatment has. Making treatment look good in shared spaces is a challenge. Getting the bass right in a room is the path to audio bliss. A measurement rig would assist in adding treatment in stages up to the limit that SWMBO (wifey) will allow. cheers Mike
  6. you've suggested similar in other posts - what are you adding to the discussion other than flogging your products? Was Schroeder working for BBC back then? Schroeder invented the QRD. The BBC did lots of cool stuff but to my knowledge didn't invent the QRD diffuser. There's no point diffusing below what's termed the "Schroeder" or "transition" frequency in your room. as below the "Schroeder/transition" frequency, modal behaviour takes over. Where that transition frequency is depends on your room dimensions - in typical small rooms this is around 200 - 300Hz. Definitely not - room behaviour below the "transition" zone cannot be helped with diffusion... Simply put "diffusion" works where sound frequencies act like light rays - travelling in straight lines and bouncing off surfaces in geometric ways - this happens at higher frequencies. Below the "Transition Zone" in a room, there is no "direction" in a sound wave, and it pressurises or de- pressurises the room. - Standing waves still require consideration - how you choose to deal with them has multiple solutions. cheers Mike
  7. Great that speech intelligibility has improved for you - interestingly if you want to make further improvements in this frequency range it's not too hard with modest room treatments (things the "wifey" "may" let you get away with) - something many restaurants with too many hard surfaces would benefit from. Room treatment in shared rooms is always a struggle, but IMO room treatment is the best "bang for buck" upgrade you can make. Acquiring a measurement rig will assist in making the right decisions if heading down this path. cheers Mike
  8. unless you're annoying neighbours or others in the house, it doesn't matter if elsewhere in the room the sound was super bassy - that's expected - your song selection was appropriate Bass response changes massively around a room (the more rigid the room boundaries, the bigger the difference) - focus on getting the bass right at the listening position. cheers Mike
  9. nice work - well done
  10. room boom is awful, and at other people's places, if they let me, I'll tweak the bass down, or just leave the room. Much more difficult as a passenger in other's cars - we're you're just itching to tweak the bass down to remove that "bloom" - especially on tracks I like - tweak the bass down and turn the volume up! Unlikely to help much at 60Hz unfortunately Below 100Hz my treatment is not doing much - and I have a lot of it! But EQ works very well in this region - lop the peaks off with EQ and things get much better - it's definitely not "un-addressable". I EQ my system relatively flat then add a room curve that shelves the FR starting around 80-100hz dropping slowly to 20kHz - around 6-12dB drop across the range. I tweak the EQ from there on the remote control bass and treble buttons. Treble on the remote is often backed off a bit, depending on the track - bass often the reverse. I find good, clean, articulate bass (no bloom) a bit addictive, so it's turned up quite often cheers Mike
  11. Hi Slim, Earthing and earth loops is a little off topic, but I suspect @joz won't mind in a 10 year old thread... "Star Earthing" is deployed within the chassis of a single component, and is definitely recommended if DIYing a bit of kit. You don't "star earth" across multiple components, other than say having a dedicated power circuit for all your stereo gear, where each earth pin on each bit of gear is as close to the same voltage as possible. IME, when mixing and matching purchased gear (and DIY gear), it can be a mixed bag with earth loops - they're extraordinarily hard to track down and eradicate, compounded with active systems and many more amps. I've come to the realisation that they only matter if you can hear them from the listening position. I use a laptop as my music source. For some reason I always get an earth loop if the laptop supply has an earth pin. I've used other laptop power supplies that don't have an earth pin and the earth loop disappears. Never delete an earth pin from any gear - it's there to protect you! There are some excellent online sources for earthing: http://sound.whsites.net/earthing.htm http://www.rane.com/note151.html http://www.rane.com/note110.html whether the Dayton amp is underpowered or not will completely depend on how much EQ you apply to achieve your target "in room" response with the driver/box - you have a capable sub (Velodyne DD18), and the Dayton amp "should" be fine in "most" rooms. I run Acoustic Elegance TD18's as my mid bass (40 - 350Hz), and only a pair of "puny" 12 inch drivers in my tapped horn sub. IMO every stereo benefits from 18's in the system somewhere cheers Mike
  12. Just found this link https://news.ncsu.edu/2017/06/thinner-sound-diffuser-2017/ and the PDF can be downloaded here https://journals.aps.org/prx/abstract/10.1103/PhysRevX.7.021034 an order of magnitude reduction in the depth of diffusion. DIY looks tricky, but home 3D printing could change all that. cheers Mike
  13. did you attach the wrong picture? - that's a Helmholtz pressure trap, not a Schroeder diffuser?
  14. 2 Subwoofers

    I'm Ok with this - sure bass can be directional. Not that I've ever been there, but I'm sure if you walk 500m from Niagara Falls (or even 2km) you can still work out directionally where the noise is coming from. But listening within a room is different scenario - at low frequencies (let's say below 80Hz), the ear/brain takes a few cycles to recognise and interpret the signal, and by that time the room has got involved. In my room I've only just got my single sub working again after nearly 12 months or so. I spent a bunch of time last weekend dialing in the sub again. You can't "locate" my sub by ear - the brain just thinks the sound is coming from the main speakers, even though I know it's not. I quite often put my head down next to the mouth of the tapped horn to check it's running - you get used to the extended bass in the room but no way can you tell where it comes from. cheers Mike
  15. any would be fine for bass - the bass won't see it. some treble may be reflected - not necessarily bad No - bass will just pass through - a brick wall is a bass reflector, not a thin layer of plastic - Rocky is trying to keep treble in the room and not absorb it - hence the plastic. get a panel made - if you can blow through it then it's still absorbing treble - if you want that all good, if you don't want that then put plastic underneath. Mike
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