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About almikel

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  1. almikel

    Catman's Analog Musings

    room acoustics contribute significantly to the "in room" sound - way more than any other component. Larger rooms will have modal support lower in frequency than smaller rooms. The lowest mode supported in the room will be wavelength/2 equals the longest dimension in the room. This assumes rigid walls. Modal behaviour becomes unpredictable with lightly constructed boundaries. cheers Mike
  2. almikel

    Azura Bass Horns

    I'm the same - I run PSE144 horns 350Hz up, sealed 18" bass below that down to 60Hz, and a tapped horn sub 20-60Hz. My PSE + sealed 18 "stack" - the 18" is an Acoustic Elegance TD18 My T20 tapped horn sub - runs twin 12" Rythmik drivers and amps Takes up more room than I'd like, and I've been too lazy to mount it outside the room, which was the original plan I've never heard horn bass - I should seek some local systems out! My bass is not horns, but my sealed TD18"s barely move even with the wick turned up - and the clean bass brings a smile to my face constantly. I agree that a key is the low distortion, but in my case also the absorption in the room cleaning up 120 - 500Hz, and a leaky room helping reduce resonances below that. The sub bass from the tapped horn is clean and effortless also. Very nice build - well done! My DIY skills don't extend to anything curved, and I envy all those who can drive Hornresp well... ...and where would we be without the people who develop these amazing free tools such as Hornresp, REW, QRDude, WinISD etc - huge kudos to them! cheers Mike ps 1st time I've heard of an "Onkens" design? had to google it
  3. almikel

    Option for Ceiling Insualtion

    Any fibreglass or poly batts are fine Thermal properties equate well with acoustic Mike
  4. The roller shutter will have minimal/no impact on isolation, and potentially add rattles Double glazing is a well established solution to assist with isolation - more typically applied to houses suffering from road noise or houses under an aircraft flight path - it's a respected solution that works. With respect to @cdave, the statement , "I read somewhere that thicker glass was more effective in blocking sound transmission than double glazing" lacks some provenance. In my interweb surfing I've found lots of glazing sites that show sound transmission ratings for different glass combinations - given thicker glass adds mass (one contributor to isolation) it will change sound transmission, but whether it's "better" than double glazing for isolation would be easy to find with Google. It all comes down to how isolated you need/want your room to end up. Are you under a flight path or have external noise sources to block coming into the room? Do you care about sound leakage out of the room to annoy the neighbours/other household members? If you're going to a large amount of effort for the rest of the room, I don't get why you wouldn't plug that window as per PtG's recommendation - it will be a flanking path for sound (in and out) if you don't... ...as I said above, I have a leaky room and tolerant family/neighbours - the cops haven't showed up - yet! Achieving decent isolation is a good target to have on a new construction - but knowing you're building in flanking paths is not a good start...why bother with the considerable expense of the rest of the room? Just build a normal room (leaky) without isolation and annoy the family/neighbours...hence PtG "all or nothing" statement. Leaky rooms are much easier to get the bass right - but you'll never get close to 20dB SPL ambient noise. cheers Mike
  5. almikel

    Option for Ceiling Insualtion

    try here: https://buybuildingsupplies.com.au/insulation-c-1923.html as per @Irek I prefer poly to fiberglass - but both work fine - I just don't like working with the itchy stuff (fiberglass). cheers Mike
  6. PtG's suggestion won't affect resale - you can just remove it, patch and paint. +1 Here's a more direct link that specifically looks at ceilings https://www.soundproofingcompany.com/soundproofing101/building-a-room-within-a-room/ scroll down to "How about that ceiling framing?" As PtG says, likely the cheapest option the elephant in the room is "Flanking Noise" Again from the same site https://www.soundproofingcompany.com/soundproofing101/flanking-and-indirect-sound-leaks/ PtG has much more experience than I do in building rooms for isolation - I've built 1 room (not my own) - a home recording studio - with multi layers of Fyrecheck with GG between, offset studs (not double studs), resilient clips on the ceiling - the isolation is OK, not great - the timber floor is likely the weak point and is common across the studio and the rest of the house - a difficult flanking path to avoid with timber floors - concrete slab is much better in this respect. Floor to ceiling 600mm wide traps in all 4 wall/wall corners will help clean up 125-500Hz nicely. This will change the spectral balance of your sidewall first reflections compared to the direct sound from the speakers - you'll absorb lots of treble and no bass - so the direct sound will be full range, and the sidewall reflections will have less treble. Plenty of smart people - Toole, Geddes, etc consider this a bad thing - but only if the "off axis" response of your speakers is nice and smooth. Try it and see if you like it...as I said above, my focus for treatment is on the bass frequencies first, so sidewall reflections is not something I would treat first. Great idea - damping ceiling reflections (different from lateral sidewall reflections) is good. concentrate on straddling corners for bass traps if using absorption (remember lots of options with corners). Diffusion has some compromises - the key one being you can't sit too close - if you have a decent distance between the diffuser and the listening position then they're great. This is just my opinion - but I stand by it - get the bass right (not easy), and IME other treatments are "icing on the cake". My stereo room is a lightly constructed spare room downstairs and leaks bass like a sieve - all living areas are upstairs. It has loads of absorption, no diffusion, and no isolation. The bass is fantastic, but the rest of the family and the neighbourhood hears when my wife or I crank the stereo, and the ambient noise in the room never gets below 30-35dB SPL. Well isolated rooms can get to 20dB SPL ambient noise - a massive difference. cheers Mike
  7. so isolation clips and multiple layers of gyprock with green glue? there are 20 corners in a rectangular room to consider for treatment: 8 tri corners 4 wall/wall corners 4 wall/floor corners 4 wall/ceiling corners Note that at the boundaries, pressure is maximum, but velocity is minimum Absorption works on velocity, so the absorption further away from the boundary is doing most of the work for lower frequencies (max velocity is wavelength/4 from the boundary). I would regard 600mm wide the absolute minimum width for corner straddling absorption expected to operate at lower frequencies. 1000mm or 1200mm wide is better. why? that stops sound energy getting to the top and bottom of the absorption. Build whatever frame you want to hold the absorption in place, but leave as much absorption as possible exposed (covered in fabric as required) to absorb sound. Ultratel and any other fibreglass insulation product will work fine I gave up using fibreglass a long time ago. Poly works nearly as well, only needs covering for aesthetics, isn't horrible itchy stuff, but is harder to cut than fibreglass. Bang for buck, the fluffy density works well, but you need more. The popular product is Polymax XHD (48kg/m^3), but expensive Mike
  8. almikel

    Catman's Analog Musings

    of course - but only when the SNR dips below an acceptable level - for many the the snap/crackle/pop of vinyl is intrusive - does that make vinyl unacceptable?
  9. I would look at room design/construction first - building acoustic panels comes much later once you know what acoustic issues require treating in the room. Is isolation/sound proofing a requirement? If it is (and it should be), then this can only be addressed during construction - you can't change isolation/sound proofing significantly once the room is built. Read every bit of info on this site: https://www.soundproofingcompany.com/soundproofing101/ Any dedicated HT room should be constructed along the guidelines in the link above. Unfortunately isolation/sound proofing tends to work against achieving good bass inside the room, as isolation/sound proofing keeps bass in the room rather than letting it out. IMHO every room benefits from treatment targeting the lower frequencies, but rooms achieving good isolation/sound proofing may require additional treatment in the lower frequencies as low bass can't "leak" out so remains bouncing around inside the room. Paul Spencer's Bass Integration Guides are useful - part 1 linked below https://www.hifizine.com/2011/06/bass-integration-guide-part-1/ As you've said, to trap bass with absorption, they need to be large - Superchunk or soffit will both work Too much absorption chops out the top end (absorbs too much treble). IMHO, target room treatment at absorbing lower frequencies to get the bass right as the first priority (absorption straddling corners or soffit traps) - minimal treble will be absorbed using this approach. Once you've got the bass under control, if you've killed the treble you can bring it back with slats or builders plastic over the absorption worry about that later - diffusion is fine tuning - IMHO getting the bass right is way more important. If you've managed to get the bass right without killing the treble then IMHO you can stop there. Once you hear a setup with clean/tight/dry bass - you're hooked - and most other setups sound boomy/bloated in the bottom end. cheers Mike
  10. almikel

    Catman's Analog Musings

    all resistors contribute "thermal noise" to a circuit, and the higher resistance, the higher the noise. That said, distortion is more objectionable than noise, assuming an acceptable SNR is achieved at the output. Hence why in the digital realm "dithering" is employed to convert quantisation distortion to noise. mike
  11. almikel

    Push Pull Subwoofer Build?

    which thread? the VPR thread?
  12. almikel

    Push Pull Subwoofer Build?

    OK - I had misunderstood. Placing a driver on the front and rear of a box where both drivers move out at the same time is 2 monopoles, which as Dave says, based on the small distances between the drivers (compared to the wavelengths being generated) will operate as a single monopole. You won't get the figure 8 cancellation at the baffle edges you get with a dipole. As Dave says, dipoles excite room modes differently because of the figure 8 pattern. If the sub doesn't excite a particular mode - whatever type of sub - then you won't have reverberant energy in the room from that mode from that sub (other subs may still excite that mode). Toole had some good papers on this - by deliberately placing a sub in a null for a particular mode, the sub won't excite that mode. This will be room related - and the more rigid the room, the bigger the issue. When you say "nearly flat", try lopping off remaining peaks with EQ - this should also reduce reverberation times for those peaks. Once you've done all you can with sub/s position and EQ, then treatment is the only thing that can reduce the reverberation times - but you need to target the treatment on the problem areas - a different discussion. As Dave says, the "type" of sub will have a very small impact on the result compared to position/EQ/using multiple subs I agree... and keep it as simple as possible - I would recommend sealed box monopoles with 1 driver per box. You have relatively modest SPL requirements. 2 subs with the Dayton RSS390HO-4 driver should be ample. Go with as large a box as you can get away with to reduce the EQ you'll need to push the driver to 20Hz. cheers Mike
  13. almikel

    Push Pull Subwoofer Build?

    My interpretation of what PK is saying is that he's proposing a sealed box with a driver on the front and the rear wired so they move in the same direction, ie front driver moves out, rear driver moves in. I would regard this as a dipole - I may have completely misunderstood PK's intention... Maybe I misunderstood what you said (see above) If I'm correct in my understanding you're proposing a box with front and rear drivers that move "forwards and backwards" in synch, like a dipole. Based on my limited understanding of acoustics, once you're below the modal range in your room (ie in the "pressure zone") to make bass you need to increase/decrease pressure. If when you say "2 drivers moving in the same acoustical direction" you mean "moving out" at the same time, then that increases pressure in the room. One driver moving out and 1 driver moving in makes no net change to room pressure (same as a dipole). I've not experimented with dipole subs, but I struggle to see how they work lower than the lowest mode if they don't change net pressure in the room...could easily be one of those "well dipole subs can create any frequency in 4 pi space, so why does a room change anything?" sort of discussions... cheers Mike
  14. almikel

    Push Pull Subwoofer Build?

    and as a lazy DIYer, dipole bass is too hard to get right - so I'll stay with monopoles for subs - much easier Mike
  15. almikel

    Push Pull Subwoofer Build?

    subs usually need to cope with higher SPLs - especially with HT http://www.acousticfrontiers.com/2013314thx-reference-level/ Mike