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About BioBrian

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  • Birthday 06/11/1954

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  1. Hi Mike, that's a surprise - it means everyone up the East of Oz can suffer these little charmers? Surprised you don't attract huge mutant bees to those horns, but I don't suppose you store pollen in them. Swallows can be really cheeky when I leave the door open - and a bit more control over their 'cheeks' would be a good thing. Rodents: I went to a lot of trouble to fit screens to the bottoms of my DTQWT-12 (5' high) horns. Makes XO alterations quite a pain ( - no don't say it!!) Somewhere in the fine print above I mentioned that these vents are actually 150 mm pipe. I've seen that Aust study into flaring vents - they certainly went to a lot of trouble, but if the vents are big enough in the first place, choofing can't be an issue. I'm very sure that's covered here. WinISD gives me a length that nicely fits without curves, or poking it 14" outside the box, like in one sub I built. On the lighter side, there may be an adaptation of some of your electronica that emits ultrasonic noises to repel the 4-legged home-lovers, when your gear's in standby? It'd need to work better than the one I bought to keep next to my equipment in the Barn. As a precaution I set a rat trap right next to it, and caught one the first night. Blood spray on my server to prove it - yum. But having a super-tweeter nosing out of your tapped horn sub might turn a few heads.
  2. Some would probably amuse themselves, thinking sewer pipe might be appropriate for the sound that it produces. Not we enlightened folk, though 😋. It's the right size (no danger of choofing), acoustically dead, thick and heavy, and routing the hole for this would be much easier than doing wooden ones. The circle gives the least surface area for the vent, for the same cross-section. Not sure about the appeal of the cap, if visible from the room - I got away with that idea with the 'Bel Gizas' because they face the wall. Damn, those caps are expensive (not possum/merino, either). I think if I rout the hole from the rear of the baffle and stop 12 mm before the face, I can glue the pipe in, and use a rounding-off bit with depth bearing to whizz around and make a nice flare, in about 3 seconds flat. I worry about the mud-wasps, though. I'd like to have some fly-wire mesh at the rear of the vent, or some easily-removable mesh at the face. I've never heard of anyone else in the world with this problem, but the little buggers are very persistent here, and very destructive. Love to build their nests of mud and half-dead spiders in shapes like roll-surrounds, and circular holes. They make a terrible cutting, high-pitched sound while doing it, and it's almost impossible to tell the direction it's coming from. Especially if it's inside a box. This is one reason I've 'put a cap on' (sorry) the max vent size at 150 mm diameter, as it would allow for a bit of extra flow without causing compression or hissing, or whatever. Anyway, I have no shame (that's gotta be obvious by now) left about the looks - I could still keep them protruding, and paint them black or silver, to keep the discussion unresolved forever 😊. Don't nobody say pink...
  3. Thanks, SS, If I'd known, I might have gone this way. The one I got is E-size though, which means it'll take longer to run out in the middle of a job, but... It's hard to find a good option - down here I've watched 2 competing companies vie for our dollars. The one I chose had cheaper rental, the other one cheaper refill price. Now the low-rental one has risen to the same as the other, and the other's gas price risen to the same as mine. It's hard not to get bitter about the rubbery figures out there in building - I'll try not to get too heated for now. (Am I conspiracy theorist when I note that the gas line I was sold with the welder about 5 years ago had cracked open and was leaking at both ends??)
  4. Well big bonky boxes need large panels. Laminating large panels needs flat surfaces. Flat around here is like finding odourless wombat droppings. Here we go. The 'old' bench, though pretty flat, had too much deflection when taking weight, so I stiffened it by doubling the rails (rafters). So, 4x stiffer. Now there's a new one on the way, which might even better that. 100 x 50 x 3 mm RHS rails, which I'm finally getting off the floor - bought decades ago for a trailer project that never happened. So balancing a recycling frenzy with an absolutely appalling rip-off (getting "my own" MIG bottle for a mere $500), this project is slowly emerging from dreamland. My floor unfortunately wasn't made by Italians, so I needed the 2 long beams, propped and leveled within microns (well, good try) to do it all on. After some convincing with tack-welded braces and other encouragement, it all started getting square enough to add the vital top bits. I've been searching around for suitable flat tops, and the best I've found so far is some 40 mm solid wood doors, sheathed in Masonite, from Bunnos. (Any suggestions welcome. They need to be around 2040 x 750 mm, thick as possible). Whatever, there are 18 holes drilled ready, and a bunch of 75 x 8 mm coach screws to hold the tops down and prevent any warping they might feel inclined to do under my influence. Need some painting weather as well. Back on the knees - not, but hoping. Spring is better than winter. Even if it blows your MIG away and makes metal bubbles, grr...
  5. But coming from a Salami Pundit, it goes without saying that they'd be tasteful and above board?
  6. I thought this was interesting. Troels built this 300 litre monster which includes 18" woofer and 10" "midrange", a horn, and separate tweet on top. He called it "The Loudspeaker", and thought it would only have novelty value, but has become quite a hit. One variation of it has a Hypex DSP thingy to driver the bottom woofer, but if interested, have a look here, where a guy tried this, but ended up preferring the full passive version. http://www.troelsgravesen.dk/speakertalk.htm then scroll down to 17th of April 2019. There's a link to Bjorne's page which mentions his 500 W (per side) Gryphon power amp.
  7. Hi Mike, I'm glad you understand the situation. The top 3 drivers have been padded down, and I'm quite happy with the balance now. The only thing reducing the 15'' drivers' sensitivity is the 2 C-coils in the passive 4th Order LP filter. This amounts to well less than 1 Ohm, from memory. But as I said a few pages back, I'd like to measure the system sensitivity in a meaningful way, just to know. As full-range speakers, these 4-ways have produced what I wanted, and they do it really well. Going back to my 3-ways, with their 10" woofers in 100 litres, it's like "hullo, is anyone home?". I've taken on all the comments about the "subs" part surely being in the wrong part of the room, blah blah, and am beginning the hole-filling pleasure of bass mode correction using dedicated subs - this on my other thread "Gestating..." But the bottom end of these guys is delivering all I could have dreamed of in the beginning. I think on the first page I had them just sitting on the floor with not even any baffles, and suddenly I was getting that magic. Well now it's much more, in a huge room, and delivering some awesome effortless power to the lower chakra. It's highlighted problems in some recordings - sadly, two of me playing with the Tas Symphony Chamber Players, which we recorded at Government House. It wasn't until I played these CDs through these speakers that I could hear the very low rumble of traffic trundling its way toward the Tasman Bridge, about 1 km away. Another one is a searing recent performance of Tchaikovsky 6 with Currentzis at the helm ("hi-res"!). The last movement, even in quiet passages, has these 15" drivers flapping ridiculously - it's unlistenable (and should never have been released). The biggest surprise so far was when I put on the CD single that came with Madonna's "Sex" coffee-table book. It's the sort of noise they would play in a strip joint - extreme heavy bass. In previous attempts to tolerate it on other systems through the years, that's all I've heard - driver-destroying, ear-destroying bass. But in this system, suddenly it became more like music - I could understand the lyrics (both of them) and hear other instruments, right through the spectrum. Quite an eye-opener (but would a strip-joint have speakers good enough??). So going back to painting myself, I've read your point of view often, and while that way of doing things no doubt works and satisfies a lot of enthusiasts, my design has totally different goals, and I believe has succeeded. I think a lot of opinion about vented boxes comes from theory and not practice. If you push anything past its design limits (amplifiers clipping, cars cornering, etc), you can expect problems. I operate way below those limits, and can enjoy that special sound of relatively unpadded woofers, especially at low volume. To me, putting woofers in little boxes and using SMPS and DSP is like finding a beautiful woman, giving her a double mastectomy, then plumping her out with silicon implants. "Same outcome"? Yes - measure it!
  8. @davewantsmoore Oh and I just noticed that your driver entry is for the model in the other thread - with the L in the name. Not very different, but may need re-doing for this thread.
  9. I should also have said that my question of amplifier requirement refers to this driver in the 4-way system (that you heard a version of). I presume the other drivers would shy away from 300W, but that's a question, and the reason I put in the impedance graph from DATS. I've never had the system anywhere near using the full power of the A 21 (250 into 8). In fact, Just using bi-amped Cyrus at 70 per side there's no audible sign of strain, but the Parasound and Holton had increased bass Authority. And Authority with Clarity from the Holton 500 Supreme (300 into 8). I so wish you'd been able to hear it.
  10. Thanks heaps, Dave. Sorry, I've been out doing stuff and wasn't able to to correct the situation. It seems you are (deja vu!) referring to the problems in my other thread - the "Gestation" one, where we were designing boxes for the subwoofer version of these drivers. The ones in this thread are already built. They are in 240 litre boxes (you saw and heard them), and are vented, but I can close the vents for "study purposes" (and a cleaner bass, if the recorded material is too bloated, and/or if the door is closed). Now that you've entered the driver info for yourself, it might save a lot of time if you whizz the 240 litre box size in, and open the pages most meaningful for power requirement, etc. But I'll post mine again here to show size and tuning. It has twin 103 mm diameter vents, tuned to 22.6 Hz, 331.4 mm long. LP filter (by design only! 😉) is down ~3dB @ 100 Hz. I still don't really understand this one. If you feel up to commenting on this, it would be very much appreciated.
  11. The 15" driver is the same as in the 1st post - SB42FHC75-6. The Audio Technology drivers (8" and 5") specs can't be found on the 'net, as they are made to order, but sensitivities are ~93 and 89 dB. The tweeter is SS D2908/714000 Be. The passive crossovers are... (add descriptors of choice)... I put the question out, as the demands on an amplifier are a lot more complex than a WinISD plot of one woofer playing one sine wave can indicate. People talk of certain speakers being a 'dog' or a 'pig' to drive, especially Maggies in combo with woofers. My perception is that this creature of mine is the opposite, but I have no proof. I want to set up a test so that I can say "these speakers are such-and-such sensitivity". I'm not sure of the standard test for this, but I can have a go. I thought the impedance plot could be used to indicate the amplifier power required (of the whole speaker), but maybe that's not correct. I have a neighbour who's a skilled sound reinforcement guy - he said that whatever the woofer's rated at, use an amp of double that power (so I'd need a 600W amp). But in my 4-ways?? And then there's the real-world thing. Whatever WinISD says about power and displacement, it's only looking at a single clean sine-wave. What about complex music? I have an organ track (opening of Kalevi Aho's 3rd Interlude) that sounds like the organist is leaning on the keys with both forearms (and pedals, to boot), so literally dozens of pipes are playing fortissimo at the same time - this goes for maybe 15 seconds. It's truly cringe-worthy. You can almost see the wall shrink, the amp's sucking so much power from it. This would seem to me to be beyond simple calculation. So a simple example - would a Luxman M-900u drive my speakers fully in a large room? It's rated 150W into 8, doubling to 300W at 4 Ohms, and I think doubling again down to 2. For those trying to read my impedance plot on a walkie-talkie, it drops to about 3.2 Ohms at around 150 Hz (above 1st crossover frequency).
  12. I'll try to do it with Omnimic. A lot of my most enjoyable musical moments are from quiet music, but as mentioned in the "A Holton Experience" thread, the Mahler 4 climax is a good test for what I need volume/distortion-wise. With Anthony's amp, I was almost embarrassed; this climax was just like a cup of tea with biscuits, not the smoke-and-sparks fears of the last 50 years of my hifi life.
  13. Fascinating, @Wozza_Lee, thanks for your input. It gives wildly different results, depending on speaker sensitivity, and on expected playback level, which is not known to me. Funny that the 1st result, using off-the-cuff approximations, said I need 32 Watts! I need to test the speakers' sensitivity properly. Presuming at 1 metre, 1 speaker at a time, amplifier terminal output 2.83V. Will have a go.
  14. Chilling to see that this thread has been out of action for over 13 months. The snowfall the other day represents part of the reason, but life, other than real life, does get in the way awfully. I've had a lot of pleasure from these speakers, and have had good feedback from you hardy characters brave enough to come down and have a listen (thanks!). The SS Be tweeter backings are still unfinished, but very listenable. The workshop keeps getting reorganized for other events and jobs. Good thing I built the wheeled trolley things. Still no heating, so it's sort of 5 degrees on a lot of winter days. A beany definitely takes the edge off hi-def. The big Holton day threw a large spanner in the works, so one of the things I'm wondering about ATM is "What would be the ideal amplifier for these speakers?" My Parasound A 21 has never been remotely challenged by them - I'm convinced 250W/channel is enough. But Anthony's beautiful "Holton 500 Supreme" just made them sound so effortlessly powerful and clean and detailed. Why? Maybe a transformer of twice the size did it (from 1 to 2 KVA), but maybe it's more in the harmonic profile. Amplifiers do have a character. I've recently watched a youtube of Nelson Pass talking about manipulating eg 2nd harmonic, and finding people had a preference for it when phase-reversed. And amps have "objective" characteristics, as can be measured, and/or predicted by their specs, or build qualities/componentry. I would like to get more understanding of what my particular speakers need, to do their best. Seems to me that the power requirement is dictated by the amount of displacement needed at my expected 20-ish Hz. This was mentioned on Page 1: F3 at 24 Hz, I think; these ended up being in 240 litre boxes. I'm not sure just how relevant a tiny signal just coming from the USB of a computer can be, but I recently did an impedance curve of the whole 4-way, and it looked like this: So is it possible to know from this how many Watts they need from a power amp?
  15. I'm told that St Johns in Launny has 64' pipes - longer than the Hobart lot. Is your innards wobble a good thing, I wasn't sure? I'm trying to build speakers that do, without wrecking my tympanic membranes. (And hoping I like it). The 'ugly' thing is different - too many speakers out there designed for looks (how on Earth can they please people from both Mars and Venus?), and obviously compromising in the matter of ideal air movement. One thing that SNA has highlighted for me is that measurements need to be clearly labelled, and interpreted by people with a lot of understanding. In speaker marketing there are so many issues jostling for prominence (or stuffed under the rug) that just about anyone can be fooled, with or without measurements.
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