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BioBrian

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About BioBrian

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    TAS
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    Australia
  • First Name
    Brian

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  1. Thanks, lusk. I need to learn more about Qes. Relieved - it sounds like sealed will suit what I want from both new drivers. Using the box to control/suppress bass, but not damping dynamics too much. I'll try to do a set of measurements as you suggest - the cupiness may well be due to the JA8008 going too high into the mid's territory. I haven't spent much time on it, as I'm pretty desperate for them to go back to their proper homes. But I think listening to the mids on their own shows the same uncomfortable sound. I thought it might be because either the 2.6 litres is too small, or there's a reflection off the flat back wall of the mid box. I do have a hard foam shape there to dissipate it, but it did seem a bit crazy to put this Satori driver in a box it only just fits in.
  2. Hi Lusk, and anybody with else with the patience, it's been a long day in the chariot for a recently-dissected specimen (I meant me, but the speakers too). Quite a few changes, quite a few loose ends sorted: The new 3.9 mH C-coils went in, as inductors for the 8" woofer. These have done the job of raising the sensitivity of the upper 3-ways, better matching the bottom 15" woofers. I put the Scanspeak tweeter back in its little L-frame to return for duty as part of my Centre speaker, in the 7.1 system at the house. Fitted the other SB tweeter back in the 3-ways, so they're now symmetrical again. Put the 12 + 15 R = 6.67 R resistor parallel pairs in, as tweeter attenuation. This worked: it sounds more like a proper working system with the symmetry. May need to go back to 6R8 if it stays this bright, but will wait till it's played in a bit more. Fitted new 39 uF Cross Caps to the bottom 4th Order passive LP filter. It had been a bit of a bird's nest with paralleled caps, so is now one level neater. The upper 3-way is still based on Troels' SB 3-way crossover. This remains all 2nd Order, with no HP woofer filter, other than acoustic roll-off by the sealed 40 litre box. Main changes to the design are: - SBA TW29RN tweeter, instead of cheaper SB29RDC-C000-4. - SBA SATORI MW16P-8 mid, instead of smaller SB12MNRX25-4. - Troels Gravesen/SEAS JA8008 woofer (94 dB, as opposed to 88.5 for the original SBA SB23NRXS45-8). - 8" Woofer C-coil has much lower DCR, and nearly double the mH, due to using the JA8008 driver. Also to cut its mid-range output to suit XO to mid. - Mid gets 50% more uF in HP section to lower crossover point to woofer. Also a CR across its LP coil, to tame upper roll-off and XO point. - Attenuation adjustments, and placement of resistors within filters. - And of course addition of the bottom SBA SB42FHC75-6 15" woofer below, in its 240 litre vented box. It has 4th Order passive filter. Today I re-wired the whole caboodle to run as a 4-way passive again, all off Linc's Bel Canto Pre 1 and the Parasound A 21 power amp. (I think the A 21 enjoys having something to do for a change). Sorry, pictures might be a better way of presenting all that, but I'm not skilled in doing hybrid photos with text added. The upshot of all that is a pretty nice speaker system. I ran a few of the usual CDs through - Prokofiev, Stravinsky and Mahler, but look forward to getting the Server plugged in to deliver some Hi-Def files. Just in case there was a good drum track, I played some bits from Abbey Road, but it didn't have what I expected. But quite a shock - I've never heard such separation, such clarity, such a raw '60s sound, and all the lyrics so clear. Just goes to show how attitudes, presumptions, and memory, change over 2 years - I really need to go back to previous speakers to get this in contrast. I've created something pretty different, and I'm getting to accept that it's a big step up from what I've had in the past. The voicing sort of works, with, as I mentioned above, maybe a bit too much brightness from the tweeters. The prototype tweeter 'wings' are still on, which does brighten the treble. What bothers me is a kind of 'cuppy' sound from the mids. I had this complaint with the original 4" mids, but maybe this EBP thing, mentioned in my previous post, might just have the clue. Both drivers are sealed in accordance with WinISD - correct volume for Qtc of 0.707, but both sound wrong to me. I've checked their EBP numbers, and guess what? - they're both about 140, which is what Per said needs vented enclosures! The new AT 8" would be expected to have as little bass as possible, so I can keep the sealed (it would reduce to about 30 litres) box and not have to make an expensive HP filter for it. Another puzzle is that the 15 H 52 06 13 SDKA mids that I'm talking about with Per have an EBP of 130, and he says 4-5 litres sealed would suit them. I have a note here saying "Glasswolf Pages", so I probably need to look that up again and try to work out something. For this mid, Troels uses an aperiodic vent in 4.9 litres, so I can build that in, with some difficulty (vent might have to be out one side). Fitting a vent and doubling the inner box size for the present mids would be a major rebuild. So I'll keep considering the AT drivers, which would need a rebuild, but would be (more?) permanent. Yeah, that sounds good. Give me more of this transparency thing I keep hearing about, please Universe? So @lusk, please spell it out for me simply, if you can advise on EBP - and anything else that comes to mind of course. As usual, I welcome comments or advice from all readers. If you're shy, please PM. It could save a lot of dollars!
  3. Well another little package came from Nigel yesterday: 3.9 mH C-coils, which are to try as ' first entry' to the 3-Way crossovers. That means dropping the DCR to the woofer, which I'm hoping might even up the balance again. The previous inductor was 3.9 mH, with 0.66 Ohm DCR; these drop to 0.08 Ohm. I'll try to get them in today and have another go with just one amp running the lot - it would be great to keep it that simple. For the last couple of days, I've had your Pre 1 and Parasound running the big woofers, and Cyrus on top, which I could balance, power-wise, and gave the clearest sound I've had yet. (Quite pleasing, really). I still have odd tweeters, and have been playing with the balance between them - for some reason the Scanspeak one sounds more out-of-the-way and more dynamic than the SB Acoustics, but this still may be due to attenuation levels. With attenuation, I've found the gap between 4.7 and 6.8 Ohms too big, so have had to calculate resistor pairs, using the formula R1 x R2 over R1 + R2. I tried 10 + 18 = 6.43 Ohms, but will go to 12 + 15 = 6.67 for the SBA tweeter.today. The SSpk one's pretty right on 3R. I had a mail from Per Skaaning last night with more info on the lusted-after drivers. Plan had been to use the (23 cm diameter - 8") 23 I 52 in the 30 litre sealed box, but he said it needs vented, as its EBP is about 140. EBP is Fs over Qes, and I don't come across this as an important design consideration very often. Troels seems to ignore it when doing his 100-200 Hz sealed boxes for tight punchy upper-bass/lower-mid. I'm hoping the EBP thing is only important in getting efficient bass out of a driver, which I don't need, but would like to hear from any readers here, who may throw some light on it.
  4. You totally missed the thrust of Auracle's line. React if it pleases you. I have a very busy sense of humour, but you might want to observe, as I've had to, that when a joke gets no response, it can be assumed that it was not at all appreciated. I'm actually more concerned with future readers who, like me, might get very sick of the crap that invades threads and drains the good energy and direction that they can generate.
  5. May I respectfully suggest you start it yourself, and leave this thread to those who don't need to be yelled at. A closer reading might reveal that Sam, who has been in consultation with me over this build, has more serious intentions in life, as do I.
  6. Hobart GTG late september EOI

    Count me in please.
  7. Well this is looking productive. Perhaps we could continue as PMs, and if any other Tassie Tinhats want to join in, please let us know. GTG with a difference! Let us know what format, venue, and variety of apples, please Sam.
  8. Paper machè horns.

    The front side should be a lot smoother though, shouldn't it? Looks really good to me. If it used to be knickers, it's found a much nobler purpose!
  9. Oh good. Here was me thinking a TT was a round thing with an arm, so a T must be just an armless round thing. I have a whiteboard. Choice of coloured pens. Or maybe you'd prefer in town? Just need to polish up me tinfoil hat (lying - but I'll take building one as nice as yours seriously, if necessary). Thanks; look forward to it.
  10. Hello Auracle, thanks for your reply. Sorry to have caused you to 'agonize' - not my intention, of course! It would seem that in trying to clarify what I meant, discussion of these complex issues might have caused more misunderstanding. Some of your post I understand, some not. "Filter networks usually come in the form of T or TT (pi)" - no idea - I try to avoid jargon until it becomes 2nd nature. Due to others' never-ending quest for mathematical understanding of speakers, I stick with a "do this, and hear/measure what happens" approach. This is safer for me than relying on eg internet calculators, which are a bit of a farce. What I would trust is good software, but at well over $1000, I've left that to the people who are capable of affording, using, and interpreting it. I'm glad you have your calculators, but you also have the knowledge to use them. I can only trust the tools I have, and my fairly strong taste in a satisfactory outcome. The word "quasi" is meaningful to me in other contexts, but I don't know why you've used it here. I am guessing "quasi parallel" refers to all elements parallel to drivers? eg LCRs, LRs and CR (Zobels)? "Peaks/troughs" would refer to variations in the FR curve? By "attenuation" I mean anything resistive in the signal path, eg a resistor, or the DCR of an inductor, in series with a driver. Please say if this is incorrect! (Eg the DCR of an air-core 3.9mH is 0.59, where the same value in C-core is 12 times less, at 0.05 Ohms. I have found differences caused by less than 0.5 Ohms in series to be readily heard). The saturation issue is not something I can have an opinion on, but I hear Jantzen (OK, they make the things ).From their website: "If the stated maximum wattage is not exceeded the core will never saturate. [Rating for my coil is 2000 Watts - Brian] The C-Coil is designed for the bass section of crossovers and for passive Sub-Woofers, available in different core and wire sizes". The Jantzen P-core ones I use for testing also have high saturation, and are recommended for the low frequencies only used by bass drivers. From the Speaker Bug website: "Power handling before saturation is 400 Watts." "Ruler flat frequency responses". I've spent about 5 years, in various projects, getting closer to ruler-straight (as opposed to ruler-flat, on account of needing a gradual fall toward high frequencies - I don't think anyone disputes that this is better for educated ears). This is a goal, not an expectation, for me. Enjoying the thrill of getting closer is something I'm sure I'm not alone in. I have to graciously disagree about the 2 dB thing. The graph I posted on August 1 (p 10) shows the 'improvements' made by changing the tweeter baffle shape. These appear to be less than 2 dB (admittedly 'improving' a rise followed by a dip) but to me are definitely audible, and I'm sure even reasonably elderly ears other than mine would pick it up. Then, I did spend 30 years as a violinist, playing with extremely fine differences in often very strained interpersonal environments, so I can't even guess what other people hear. I presume you would agree with me that sometimes it can takes days, or weeks, of listening to be able to hear not just "2 dB difference", but how that affects all the different recordings we listen to - it'll show up much more on some. Hopefully this has left us slightly less 'out of phase'. I feel it would be much quicker and easier to progress if we got together again some time. and yes - I agree totally that all the above is very much a '1st World Problem'! I'm actually hoping the maniacs give us peace for long enough at least to finish my speakers. Not that I need any more disincentives.
  11. Remote control of JRiver

    Do you use a Streacom case? If so, the agent in Sydney sells a remote/sensor kit. No idea what happens after that. Interested, though.
  12. The Pre 1 is a real pleasure. Especially that huge openness and apparent headroom in the bass. It's set about Vol 68 for most listening, so plenty of abundance there. Not surprised it's a keeper for you. The balanced cables were ordered from Blue Jeans last Wed, and arrived Monday arvo! I enjoyed that slight textured feel as the new plugs slid into virtually-virgin* sockets: lots of contact area, and after a couple of days, I think they allowed more of that awesome bass accuracy. * That's a thing, isn't it?
  13. Hi Sam, good to see you've hit the ground running, and are recovering fairly well from the jet lag . I'm not sure if the post on the 4th order filter made sense - there's always an "assumed understanding" and I'm never quite sure how much detail to go into, for people to make sense of my rabbiting. Firstly, the 4th order filter has less DCR than the previous 2nd order ones, due to the ginormous C-coil, and will drop even more when Nigel (Speaker Bug, @Green Wagon) gets his new C-coils in. So the net result is, that the bottom woofer actually got louder, and the top 3-way therefore relatively quieter. I fiddled a bit with mid attenuation which made a big difference, but still for the top 3-way to be balanced within itself, the sensitivity of its woofer will be critical. Otherwise, I'll have to attenuate the bottom woofer, which is contrary to the whole thrust of this thread. The other issue I've been concerned with is phase shift. When using 2nd order filters through the whole 4-way, I understand that each driver has to be reversed in polarity. compared with the one below it. I've not been doing this. All along, the drivers have been like this: Tweeter + Mid - 8" woofer + 15" woofer + At one point I tried reversing speaker wires, and do remember at one point a sound of unusual clarity and integrity, but as usual, there were too many other variables for me to remember just what made this big improvement. I'm led to understand that there's a phase shift of 90 degrees with each "order", but is this when changing BOTH drivers' filters, or just one? Suppose I could just measure it. But because the phase on the 4th order one was flat in the working range, I presume it's gone the full circle, and is just delayed by one cycle. (But at what frequency? How far do I move the box to correct that?). Whatever, the bottom woofer is having a ball, being slightly dominant at the moment, and with the 4th order filter, as is, it's doing close to 2.5 octaves (crossing about 110 Hz). Running with both vents open, as designed, it has a really open, relaxed presentation. Bass extension seems adequate in the large open room, which now has some reflection control and damping. @Upfront's lovely Bel Canto Pre and the Parasound A-21 power amp are driving the whole 4-way, through new (I feel so grown up) balanced cables, and it's the best I've heard so far. I don't want to waste too much more time fiddling (learning's fine), until I settle on the new drivers.
  14. I've actually been more concerned with pics showing the table the drinks sit on. Shallow reflections admittedly, but an indication of priority nonetheless. I completely agree that our ability to discern fine differences is greatly hampered by alcohol, but also agree that the 'normal' state of listening is an important consideration. There are definitely things to be heard and felt when the seriousness of extreme focus is relaxed, and the mind can make comparisons and associations with past experiences of listening - to either or both music and hifi equipment.
  15. Troels Discovery 18W

    Looks beautiful, Benen - well done! I agree, it's very tempting to do too much before the paint's hardened. (Might be more likely where you are: minus 3.2 degrees here yesterday). But your sofa doesn't seem to mind. Glad the XO and wiring has all worked - looking forward to the full review, and report on Troels' website, of course. Very exciting!
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