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aechmea

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About aechmea

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    Aechmea recurvata

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    Hunter Valley
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    Australia
  1. Subwoofer Placement & Integration

    The DEQX measures each item individually, so the peaks and troughs are not due to L sub interacting with R sub. The traces for L sub and R sub are essentially identical, so both subs are suffering the same 'problem' for the same reason. My strong suspicion is that 2 bass sources at one end of the room are creating one large reflection off the rear wall (behind the head) which when combined with the direct sound is causing the reinforcements and cancellations = SBIR As Pie suggested earlier, I think that you are going to have to move one sub, and that would be to move it to the other end of the room such that the path differences from walls to 'chair' are quite different for each. Effectively one sub fills in the gaps in the other's response. That's what I had to do.
  2. He was the producer (or something) of a couple (one?) of Steeleye Span albums in the early 80s. About "Rocket Cottage" time. [I could look it up if desired] I have "Tarot Suite" on CD (first release or close too). The 1979 vinyl of "Tarot" and 1980 "Waves" are up in the garage. Yeah, I don't do vinyl at all.
  3. Commonwealth 12

    Welcome Steve. Please join in the conversations too. May also be an idea not to publish your email address so publicly. Once you are a real member people can send and receive "personal messages" which are hidden.
  4. Panels vs Dynamic (cone) Speakers

    From p38 snip ... significant addition to the work of Schroeder and Ando on the importance of minimizing inter-aural ... snip Hey, @Ando, an acknowledgement of your excellent work.
  5. I see Mike Oldfield is taken so I will submit another of my desert island disks. 1. Faces: A nods as good as a wink 2. Radiohead : Kid A 3. Jodi James :Things I leave behind 4. Dire Straits: Brothers in Arms 5. Depeche Mode - Exciter 6. 801 - 801 Live ( album ) 7. Gorillaz: Humanz 8. Tangerine Dream - LOGOS 9. Robert Fripp - Exposure 10. Midnight Oil - Bird Noises 11. The Alan Parsons Project - Eye in the Sky 12. Miles Davis - Kind Of Blue 13. Beck - Sea Change 14. Bruce Springsteen - Born To Run 15. Van Morrison: Astral Weeks 16. Queensryche: Silent Lucidity 17. Roger Waters: Amused to death 18. Robag Wruhme - Thora Vukk 19.Eagles - Hotel California 20. Mike Oldfield-Ommadawn 21. Malia & Boris Blank - Convergence 22. Smashing Pumpkins - Siamese Dream 23. Justin Bieber - My World 24. Nitin Sawhney - Beyond Skin 25. Queen - Innuendo (LP) 26. Phideaux - Doomsday Afternoon
  6. Making muy own acoustic panels

    I didn't built a box/frame at all. I just got Mrs. A to make covers from a linen/hessian material for the full (2400 x 1200 x 100) and half sheets of 32kg and 64kg fibreglass. They are rigid enough to be self supporting (propped up against something) and I can place them wherever I want. One covers a doorway! and at one time I had 2 in a teepee formation out in the room. No walls were drilled/damaged and the lot can be thrown away at any time with no lasting effect. I have a lot of fibreglass. 5 full sheets and 2 half sheet plus 10 DIY tube traps made from sectional pipe insulation (= pre-formed round tubes). This is effective down to about 80Hz or maybe a bit less, but doesn't help much below that. Positioning is the best solution at those freqs. The number 1 thing that fixed my initial problem with the world's largest suck-out from 30 - 50Hz, was to move a sub from the front of the room to the back wall where it did not suffer from SBIR at those particular frequencies. You have to be a bit adventurous with sub positioning to get the desired result; neat, tidy and out-of-the-way is unlikely to work.
  7. $7.7k or whatever is not the sort of money that I would consider spending on power. A few hundred bucks on a dedicated circuit with a surge thingo in the fuse box would be about right. Then you have $7k left to spend on a better room, better speakers or better source material. $7k is a lot of CDs or LPs or downloads or ... room correction or ... TT or ... [Yes I do have a power device simply because in the olden days the voltage here used to fluctuate wildly from 230 to 213. These days it sits at 253 so I still prefer that to be cut back somewhat. I do not however get any audible improvement. The power amps are plugged into the wall as recommended by the designer, so there is no 'throttling'.]
  8. Speaker Position Problems Magnepan 20.7's

    I haven't given up hope for you yet Bill. Forget the 150 and 180 for the time being; lets look at the big suck at 70Hz Time to get the subs out of the far corners and trial them along the side and back walls. Behind the chair worked for me as did one sub out in the room away from walls, but that proved to be an annoyance for walking. This little gem can give some ideas. http://www.hunecke.de/en/calculators/loudspeakers.html It won't work for planars due to the reverse polarity backwave but will for the subs. So just use it to trial some possible sub positions. I have this ATM, which has doorways, furniture etc. taken into account. Not really to scale, but close enough. [Remarkably similar rooms, by the way.] Yes, the left sub is in the back right of the room. ------------------------------- When I measure close to and with my (leather) chair in situ then I get all sorts of funnies, mainly in the mid range. Might be worth trying without the chairs to see whether some lumps and bumps disappear. I doubt it, but one never knows. ------------------------------- Hmmmmm. A speaker (sub) 1.2m away from a wall will have a null at 70Hz when the direct wave and primary reflection combine. Since both subs are the same distance from the front wall and about 1m-ish away, both are producing a 70Hz null. The Maggies look to be 2m-ish from the front wall. The backwave has to travel an extra 5m-ish, a wavelength which is equivalent to a freq of 70Hz. Because the backwave and directwave are reversed polarity, when they combine, this gives another null. So all 4 speakers (2 maggies and 2 subs) are producing a null at about 70ishHz. Worth investigating. Time to get the subs on the move.
  9. Speaker Position Problems Magnepan 20.7's

    Well, yes and no. It helped considerably in my case. Despite the attention given to room modes in the literature and internet chatter, modes were not the cause of the peaks and troughs I had in the low freqs in my room with my speakers. Instead my 'problems' were actually comb filtering (aka SBIR) rather than the standing waves of modes. In short SBIR is the interaction of the direct wave with a strong reflection. If it is half a wavelength (or odd multiple thereof) out of phase there is a cancellation at that frequency. Planar speakers have an equal amplitude and opposite polarity backwave, so when that interacts with the direct wave after a bounce or two off the front and back walls then a typical comb filtering response might be seen. The typical comb response graph can be obscured by other reflections from floor, ceiling and side walls. I used an Excel spreadsheet, room dimensions and some trigonometry to calculate path differences from speaker to chair via various wall reflection paths. These calculated path differences matched pretty well with many of the peaks and suck-outs. So I moved both subs to unusual places around the room. The sub that I placed at the wall behind the chair (rear wall) filled in the suck-out that was caused be the Maggies bouncing off the rear wall back to the chair. Rear wall to chair = 2.5m ==> path difference = 5m ==> frequency of that as half wavelength (cancellation) = 35Hz-ish. I place the mains and chair for the best soundstage, imaging, clarity and that sort of thing then place sub(s) to fill in the bass 'holes'. Sub positioning is never anywhere near where the mains are, but maybe that is just my room's geometry. My use of subs has nothing to do with bass reinforcement as such which seems to be the HT approach, rather a way to even out the bass in support of the room geometry and mains. ---------------- @Bilbo Hi Bill I would think that your suck-outs at 150Hz and 180HZ would almost certainly be room geometry/positioning/reflection/SBIR. But what exactly is the culprit. 180Hz is approx a path difference of 0.95m. 150Hz is a bit longer at 1.14m. So the reflection from what surface/object is able to give a 1m-ish path difference. Unlikely to be floor bounce. Floor bounce for a 3m listening position 1m off the floor is about 300Hz and higher freq for seats further away. Ceiling bounce is a possibility but only if the ceiling is 2.3m or less and even then planars don't have anything much off-axis to contribute to floor or ceiling bounce. Planars have a natural null at 90º and 270º so normally side walls don't matter much either, if at all. Its really all about the directwave and the reverse polarity backwave. Hmm, so I would be looking at something roughly 500mm from the speaker or the mic that the positive direct wave might be reflecting from or something 1m away that the reverse polarity backwave can reflect off. [how far from the front wall are the bass panels?] --------- On a different tack but all effectively changing the direction of the first reflection of the backwave and the directwave. 1. You might try crossing the speaker axis in front of your chair. This has the effect of angling the back wave in a different direction and maybe reflecting off an entirely different set of walls. 2. Point them directly down the length of the room. Same reason. 3. Somewhere in between. 4. I tilt mine downward significantly, so that the top and bottom of the speaker are equidistant from the ears. Somewhat disconcerting to look at. They are very tall and my ears would be below half way were the speakers upright. However it's unlikely that such a small path difference between top and bottom would be anywhere near 180Hz. But it does change the path of the backwave and directwave. 5. I have the ribbon on the outside. Effectively the bass panels are close together and the backwave bounces off the front wall first and then off to the side, rather than the side wall first and back to the middle. 6. Unless the absorption is quite thick and plentiful it won't have much affect in the freqs that we are considering. Similarly dispersion is a mid-high freq thing unless the 'skylines' are enormously huge blocks. 7. Have you tried absorption immediately at the back of the speaker to kill the backwave as best you can to see if the cancellations are due to the backwave or not. ------------------ Having said all of that I am not sure that the 2 major suck-outs would be audible. There is a shallow dip from 60Hz to 200Hz, then a low hill from 200 to 1000Hz. I guess that this would give a mid range prominence to the sound, which is sort of what you describe. The overall look is not unlike mine but in my system I could hit that with a bit of gentle EQ. Maybe if you reduce 200 -1000Hz by a dB that will make 80 - 200 more wholesome. One of those supplied ceramic-resistor-things across the mid range panel might help. Are they meant for the mid range panel, I don't know; the sockets are there. Tis all I can think of for now. A plan view of the room and positioning as suggested by Frank will help.
  10. OK, I'll fess up. I have been playing Cds since they first came out; couldn't relegate records to the garage fast enough. I have no reason to change to anything else. I don't play vinyl, I don't download, I don't stream, and I don't listen to radio. Its just me and my CDs. As far as new music is concerned, I take an occasional hint from Amazon (who says "you might like this, based on previous purchases") and from the 'prog' thread. My system can be turned off for weeks on end, such is my love of music (ha ha a bit of self deprecation there, but true nevertheless). One should never assume that your version of the hobby is the same as anyone else's.
  11. DEQX Owners Thread

    Yes indeed .... I would have to pick the time very carefully to avoid weather, wildlife and freeway and aircraft noise. All too hard really which is why it's still just a thought bubble.
  12. DEQX Owners Thread

    I measure my tall wide speakers (2m x .75m) at 3m. ie. about 1.5 times the largest dimension. It just seems right in an effort to get some sound from the top, bottom and sides of the speakers. Whether it makes any difference or not I don't know. I seem to recall Alan saying that it doesn't matter much. The current manual says something along the lines of, measure further away with large speakers. One day I will do an almikel and measure outside, off the ground for the best pseudo-anechoic measurement. The logistics of such an exercise though is a bit impenetrable. Currently I have passive XO speakers and they are amplitude and time corrected as well as anything. Active enables you to do your own XOs, but if that is done sufficiently well by the manufacturer with their passive ones then nothing gained nor lost, IMO. I have never been able to detect the presence of any XO and its anomalies either by ear or by graph, but that's just me. Even though I once did active bi-amping, I am happy being passive. Room reflections in the low frequencies (modes and SBIR) , integrating the sub(s) with mains, and room positioning in general is the most difficult aspect to get right.
  13. Sound quality of old rock CD's

    The CD layer on the Brothers in Arms SACD is a great example of the damage that can be inflicted by mastering engineers re dynamic range compression. The CD layer on this is also HDCD encoded but they didn't use "peak extend" which is the whole point of HDCD. What were they thinking. Like everything else in life - it depends. There are always, from any era, good/bad recordings, good/bad mixing, good/ bad mastering, good/bad pressings, good/bad replay equipment/environment. The trick is to get them all right. As far as CDs are concerned, I tend to buy the ones with a good DR value. Stuff with a bit of contrast is preferable (for me) than dull and loud ones which tend to sit in the rack unplayed and unloved. I can always correct bass/treble imbalances with thoughtful use of EQ.
  14. Sound quality of old rock CD's

    The info in the Rhino link is misleading. The release that they are talking about is a second version of the 40th Anniversary release. It is not a 45th anniversary release. Chrysalis is the publisher of mine, not Rhino, so I don't know what that is about. Released in 2016. Book format + 2 x CDs and 2 X DVDs. The mixing was done by Steve Wilson - exceptionally as always. However there are 2 releases of this 40th anniversary set. The first is the Wilson mix, mastered by some bloke that essentially stuffed it up. The details of the stuff-up are well documented. Disappointed, Wilson then decided to do the mastering himself. This resulted in the second release which is called Jethro Tull Aqualung 40th Anniversary Adapted Edition Remixed and Mastered by Steven Wilson Mine has a bar code: 0825646487080 Ensure that you get this version, because the poor release and the good release look very similar.
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