davewantsmoore Posted November 3, 2019 Share Posted November 3, 2019 Hmm... although goes on to get it wrong re: the bend. Even though it seems like it would ..... It doesn't "hit the wall and then go around the corner" like he infers. Link to comment Share on other sites More sharing options...
BioBrian Posted November 16, 2019 Author Share Posted November 16, 2019 Vents. Warning: the following footage may offend some viewers. For the inner flares, I found the cutouts from my 2012 DTQWT-12 woofers to be just the right diameter and (30 mm) thickness, so am very happy to be able to recycle them in triumph for this honourable exercise. Already having a centre pivot hole and being circles, only left another 6 router circle cuts to go. The sequencing has taken a bit of brain-stretching, but is going to plan OK. The same cuts are being done into the baffles, to let in the 150 mm PVC pipe. The final inner trimming and rounding will happen after the glue cures properly. 9.5 mm rounding to the pipe part, 22.4 mm rounding to the outer and inner flare parts. Pics might explain better - this is one on a pipe, the other upside down, showing the rebate to glue the pipe in: The baffle got the same diameter rebate, but both are let in (baffle is 48 mm, inner flare is 30 mm thick) so the 22.4 mm rounding bit can take just 2 mm of pipe to make a clean curve (yet to happen): Not sure about this Liquid Nails goop - 1st time using - it's certainly strong and convincingly sticking the PVC, but the sample I did a couple of days ago is still a bit soft where it's thick. I used a fine water spray as directed, but not sure how effective that was. Will have to revisit this after a certain "sub - culture" meeting tomorrow, depending on the entertainment/frivolity level... 2 Link to comment Share on other sites More sharing options...
BioBrian Posted November 18, 2019 Author Share Posted November 18, 2019 Spurred on by hearing @deblur's lovely sealed 15" AE subs yesterday, it's good to get another step closer to finishing these (here comes another one) big birthers. The baffle flares worked as well as they could have: The rest of the build will be face-down, so it'll be a while before we see these again: And the SNA-inspired inner flare (it's all been quite a journey): Oh, and admission that a little flutter of joy was had, and thanks given for being alive when these amazing tools are available to us. 5 Link to comment Share on other sites More sharing options...
Upgrayed Posted November 18, 2019 Share Posted November 18, 2019 On 16/11/2019 at 9:48 PM, BioBrian said: Vents. Warning: the following footage may offend some viewers. For the inner flares, I found the cutouts from my 2012 DTQWT-12 woofers to be just the right diameter and (30 mm) thickness, so am very happy to be able to recycle them in triumph for this honourable exercise. Already having a centre pivot hole and being circles, only left another 6 router circle cuts to go. The sequencing has taken a bit of brain-stretching, but is going to plan OK. The same cuts are being done into the baffles, to let in the 150 mm PVC pipe. The final inner trimming and rounding will happen after the glue cures properly. 9.5 mm rounding to the pipe part, 22.4 mm rounding to the outer and inner flare parts. Pics might explain better - this is one on a pipe, the other upside down, showing the rebate to glue the pipe in: The baffle got the same diameter rebate, but both are let in (baffle is 48 mm, inner flare is 30 mm thick) so the 22.4 mm rounding bit can take just 2 mm of pipe to make a clean curve (yet to happen): Not sure about this Liquid Nails goop - 1st time using - it's certainly strong and convincingly sticking the PVC, but the sample I did a couple of days ago is still a bit soft where it's thick. I used a fine water spray as directed, but not sure how effective that was. Will have to revisit this after a certain "sub - culture" meeting tomorrow, depending on the entertainment/frivolity level... Hi-end carpenters use Sikaflex, construction? variant of the stuff used to hold on automative windscreens. $17 a tube. Very impressive Link to comment Share on other sites More sharing options...
BioBrian Posted November 18, 2019 Author Share Posted November 18, 2019 56 minutes ago, deblur said: Hi-end carpenters use Sikaflex I'm an old fan of Sikaflex. But I used Sikaflex Pro to seal my flue, and the creosote melted it, also corroding zincalume and colorbond, dripping poison into my house, so I lost the faith, unreasonably of course. Silicon better there. Should have looked closer, as the Liq. Nails has a lot of bubbles and no substance where it expands out into nothingness. Still spongy after days, not as deadening as the Sika would probably have been, maybe. Whatever; the vents are strongly bonded to the ply, and are acoustically dead. I may add more weight or bracing to the pipes, but doubt it would make a huge difference. Link to comment Share on other sites More sharing options...
Upfront Posted January 4, 2020 Share Posted January 4, 2020 Hows the build going Brian? Or are you too busy fending off fires at the moment? Link to comment Share on other sites More sharing options...
BioBrian Posted January 4, 2020 Author Share Posted January 4, 2020 But I thought this was supposed to be the good-news channel . I went back to the drawing-board, and lived in denial for a few weeks, but just couldn't live with the back of the vent being so close to the back of the cabinet. Originally the thought was to have the vents protruding out of the baffle, and having the option to screw on those very attractive sewer pipe caps. Taste won over practicality in that case, but moving the vents back to be flush with the baffles sort of blinded me to the problem of breathing space at the rear of the vents. Hmm... I tried a couple of other box design options, but they either looked hideous or became impractical. If I did it again, I'd stick the vent out of one end, but the baffles already had the holes cut, so I made the box a little deeper, and have made some 60 mm "prolapses" to extend the vents out the front again. That involved more complex routing than the plain baffle flares seen a couple of posts above - it involved more laminating, and trouble from being deeper than my longest router bit (50 mm). I suppose it was good to confirm the strength of the Liquid Nails Polyurethane glue though - I thought that with a bit of padding and a sledge hammer, I'd be able to break the vent-baffle glue, but this was not going to happen without breaking the pipe. So I cut a large circle in some ply, clamped it onto the front of the baffle, and routed away the end of the pipe, until the glue line was small enough to be broken by reasonable force. I think there was only about 12 mm left before a very determined karate-kick could break the bond. So the new vent flares are prepared, but I won't glue them in now, as the build has to proceed face-down. Fires? I'm better prepared this year than ever before. Hoping this can give me some freedom for chosen activities. Took a few reflective minutes, early on New Year's Day, to make an unintentioned model of my life story (or whatever the observer may see): What I didn't notice until getting down in the river to take the pic, was that the huge base rock (1-2 tonnes?) is getting some support from a tiny compression strut. All support appreciated - thanks Linc, I'll get on with it. Promise! 4 Link to comment Share on other sites More sharing options...
BioBrian Posted January 18, 2020 Author Share Posted January 18, 2020 (edited) Well I've stolen the best hours out of most days since the last post, to peck away at these delicate giants. Everything's just BIG, and so the errors can multiply, eg when joining two 48mm thick panels at 135 degrees, the mating surfaces are something like 52mm wide and 1500mm long, so any cracks would show more than if just using 18mm in a normal box. This one shows a dry-fit of an end, and a spine. The fun part of cutting all the holes has to wait, as each of the 6 pairs of cross-braces will have to breathe in relation to the holes in the spines. There will be 3 pairs of cross-braces, which I'm making whole, then I'll cut 12mm out of their middles, so they can go either side of the spines. (8 cuts, instead of 10 for each - none are easy with the track saw). So, 12 pieces that have to line up with the ends - that's 96 cuts even if I get them right 1st time [edit: not good maths there, but turned out to be more], and that's after trying to cut 4 identical ends out of 30mm BB ply with no split edges, etc etc. Each pair will have different cutouts, eg these are behind the woofers: I've found the biggest challenge is not being able to actually start gluing - nearly all the panels have to be designed and cut first, then the order of joining will be quite tricky too (clamping large, odd angled pieces without being able to move the whole structure, etc). If I have to trim something smaller due to inaccuracy, there's a chain reaction that affects the sizes of everything to follow, so it's been quite a test of concentration. Hoping it can all fall together from here without too much drama. The rest of the build should be a bit more rewarding. Edited January 26, 2020 by BioBrian corrections 2 Link to comment Share on other sites More sharing options...
davewantsmoore Posted January 20, 2020 Share Posted January 20, 2020 On 05/01/2020 at 10:53 AM, BioBrian said: What I didn't notice until getting down in the river to take the pic, was that the huge base rock (1-2 tonnes?) is getting some support from a tiny compression strut. Nice pic. .... and also, wow 1 Link to comment Share on other sites More sharing options...
BioBrian Posted January 20, 2020 Author Share Posted January 20, 2020 Spent a while lining up the 8 cross-pieces in each box, trimming here and there. Fortunately, not too many edges have needed bits glued on and re-trimming. There aren't many holy days around here, and I'll need at least one more. 60 holes in the cross-braces so far; probably another 12 to follow. Each have 5 holes, all different diameters. Then it'll be the "spinal lesions" - I should be good at that . I'm trying to confuse those pesky end-to-end reverbs. Probably futile, but it keeps me off the street. 3 Link to comment Share on other sites More sharing options...
davewantsmoore Posted January 21, 2020 Share Posted January 21, 2020 16 hours ago, BioBrian said: I'm trying to confuse those pesky end-to-end reverbs. That won't work. Their wavelengths are so large, that they flow around your "confusing holes" like the holes are just not even there. What is the box height? If you keep the box to "subwoofer frequencies" then it seems unlikely to occur within the pass band (but box length, and Hz, will tell us). If you do expect a problem (which we need to base off math, not intuition) then the only solution (aside from modifying the box shape, which I appreciate you're not going to do now) is stuffing. This issue is another reason why I've recommending "EQ". So you can (effectively) stop it making high frequencies. Eg. a 24db/octave low pass @ 80Hz. Link to comment Share on other sites More sharing options...
BioBrian Posted January 21, 2020 Author Share Posted January 21, 2020 1 hour ago, davewantsmoore said: Their wavelengths are so large, that they flow around your "confusing holes" like the holes are just not even there. No surprises there. Phew, I can go back on the streets... 1 hour ago, davewantsmoore said: 24db/octave low pass @ 80Hz. This is my target - I think I can make it happen. If not, then there's plenty of room for the lucky person who finds these in the "roadside collection" to screw a nice Hypex on . The boxes are designed to be in the wall-ceiling corners, so their width is I guess what you are asking. Internal (longest) dimension is 1500 minus 2 x 30 mm ends, so 1440 mm. The other dimensions are harder to name, as it's basically triangular, with 2 corners a bit filled in. The question about stuffing in subs - this is still being asked around the forum, and is still unclear to me. With the previous build, 15" woofers in 240 litres vented, we ended up with basically none, as you considered it unnecessary, and possibly a hinderance. Yet every sub build I read about has carpet or eggshell foam or something on the walls, and various other pillows etc inside. But... Some of this would have a dual purpose, one being damping the panels. I'm working on having a very stiff box which won't need this. Fluffy stuffing alters the apparent air viscosity, makes the air behave like it's in a bigger box? My box is big enough not to need this. I can't test the impedance until all is finished, and adding stuffing will be difficult. To reduce resonance, I've gleaned that it would be most effective in the centre compartment of the box, which might be reachable through the driver hole. I remember it helped @acg with his cannons (after exhaustive testing; at least I was exhausted after reading it ). Sorry to bring intuition into it deliberately, but I can't imagine stuffing being much more effective than holy baffles, to affect air behaviour when belting out a bit of Madonna (might happen for demo purposes at some stage). I'd quite like to sort this. Thanks for your compliment on my pic; the river is full of wonderful gifts. Link to comment Share on other sites More sharing options...
acg Posted January 21, 2020 Share Posted January 21, 2020 47 minutes ago, BioBrian said: Fluffy stuffing alters the apparent air viscosity, makes the air behave like it's in a bigger box? My box is big enough not to need this. It does seem to. Fs certainly changed with different stuffing regimes, with more light and fluffy poly being the most effective in my situation. It also reduced the internal 100Hz resonance such that it was no longer measurable (at least not in the setup I was using) and no longer audible. So if you are worried about the dimension induced resonance my advice would be to open a bag of the most lightweight poly wall/ceiling insulation you can find and play a little. I would not bother myself with heavier stuffing, just super light stuff. Nice river shot earlier...I'm jealous that your stream still has water. 1 Link to comment Share on other sites More sharing options...
BioBrian Posted January 21, 2020 Author Share Posted January 21, 2020 I'm struggling with those figures at the moment. If Fs is defined as "free air resonance", I think we are talking about something else, but related. I looked up Fb again, but that's the resonant frequency of a ported box. And it's related to quarter wave-length, which I can't compute for now, remembering that your cannons are 1 m long? I've had experience of the impedance curve wrinkle disappearing with stuffing, but only at higher frequencies. It needed quite a lot - I use wool batts 'coz I'm organic . Yes, the river is very precious. Never dried up in my 40 years of living next to it. And we have some green grass too - 20 mm of rain so far this month makes such a difference. (Only 4.3 last January). Here's me down here unable to work in my shed at 6-8 degrees max for most winter days, and you unable to get into yours for summer! Hoping to see your big horns appear in some pics soon. Link to comment Share on other sites More sharing options...
almikel Posted January 23, 2020 Share Posted January 23, 2020 (edited) Hi Brian, you have 2 separate things going on which may/may not have impact on the room sound. You will always have a resonant frequency of the box, ie Fb - which exists whether sealed or ported, and with sealed is related to the Fs of the driver and the volume of the box... I think you're actually referring to resonances caused by "modes" generated within your box - which obey the same physics as room modes. As @davewantsmooresays, these are very unlikely to cause any issues at the frequencies/wavelengths these boxes will operate at (ie 4th order low pass around 80Hz). The lowest mode supported inside your speaker box is wavelength = longest dimension/2 - so 1440mm/2 = 720mm V (244m/s) = f x wavelength edit speed of sound is 343m/s f = 339Hz - this is the lowest mode that will be generated inside your box.edit 476Hz Clearly not an issue for your boxes if you low pass cross at 80Hz or so with 24dB/octave or so... (edit) by 160Hz you're 24dB down, and by 320Hz you're 48dB down, and a bit further down by 340Hz cheers Mike Edited January 29, 2020 by almikel 1 Link to comment Share on other sites More sharing options...
soundbyte Posted January 24, 2020 Share Posted January 24, 2020 (edited) Called in to @BioBrian 's wonderful listening location on the way back home from a trip to Cygnet. Saw these monsters in person this afternoon. Large, Heavy, Very well made so far. As usual Brian's attention to detail is very much apparent, will have to wait for a little while longer before these start making noise. The enclosures are not far from completion and with another afternoon of gluing today I would say the home stretch is in sight. Thanks for having us visit on such short notice. Russell. Edited January 24, 2020 by soundbyte 1 Link to comment Share on other sites More sharing options...
BioBrian Posted January 24, 2020 Author Share Posted January 24, 2020 1 hour ago, soundbyte said: Called in to @BioBrian 's wonderful listening location Delight to see you both, thanks for dropping in. Thought I'd better update that ancient photo! Managed to glue up the 2nd skeleton after you left. Another 10 pieces of wood fell together without too much drama. Surprisingly, the 1st baffle side piece I tried, fitted without any angle adjustment needed - the 22.5 degree setting on the Festy track saw had been spot on. So I glued it on - this one not so easy, but that's the 1st of 4 done. It's the same 48 mm as the baffle (not needed, but solved a design problem). 2 Link to comment Share on other sites More sharing options...
davewantsmoore Posted January 26, 2020 Share Posted January 26, 2020 On 21/01/2020 at 2:32 PM, BioBrian said: Sorry to bring intuition into it deliberately, but I can't imagine stuffing being much more effective than holy baffles The holes work in a frequency dependant way, in that waves below a certain frequency flow right on through. The stuffing instead works via velocity. Stiffing the centre part of the cabinet won't hurt / could help .... to damp any 'standing waves'. With a small box and low frequency cut off... it's no issue .... with a bigger box and higher frequency, they become more prevalent. Link to comment Share on other sites More sharing options...
davewantsmoore Posted January 26, 2020 Share Posted January 26, 2020 On 22/01/2020 at 10:15 AM, BioBrian said: I'm struggling with those figures at the moment. If Fs is defined as "free air resonance", I think we are talking about something else, but related. He means the resonance frequency of the driver in the box. This is sometimes called Fb ... or Fc.... or just "the resonance frequency" (as the Fs, free air, resonance frequency is long since irrelevant once you have drive mounted in box) Link to comment Share on other sites More sharing options...
BioBrian Posted February 6, 2020 Author Share Posted February 6, 2020 (edited) Well these twins are now officially overdue. "It won't happen until you do it" is the only "music" I've heard for a while. It's been a slow thing, lining up the side panels and back one - mating 4 x 22.5 degree angles, and aligning the 5 cross-pieces on each side. A lot of thin, wedge-shaped shims were sliced and the most suitable ones chosen, glued in and trimmed later, to have a nice even framework for the sides to fit onto, as clamping will be difficult. Then the box was raised and lowered down to glue/clamp the front vent "prolapse", followed by the 2nd and final fitting of the vent. This glue looks pretty disgusting, but it sure holds the plastic/wood bond, and deadens vibration. I've cut a set of struts (one visible, leaning over in the middle) to join baffle and side panels in the middle of their unsupported areas, to halve the size of any resonant surfaces. Pics will make more sense later, after gluing in. Edited February 6, 2020 by BioBrian Forgot pic 2 Link to comment Share on other sites More sharing options...
BioBrian Posted February 7, 2020 Author Share Posted February 7, 2020 Another slow day. The alignment of Box 2 is harder, due to some slight warping of the 30 mm plywood, amongst other things. But the 2nd vent got glued in, and the 8 struts happened for Box 1. 5-min Epoxy is a lovely thing, but the diagonal ones needed 12 minutes of hand-holding, before I was confident that they'd stay in place. This means the panels are ready to glue on, BUT (there's always at least one of those)... I really have to work out the hoisting/supporting bracket thing, as the end panels might need reinforcing - I don't want any air holes to undermine the intensely cerebral design process . Link to comment Share on other sites More sharing options...
BioBrian Posted February 7, 2020 Author Share Posted February 7, 2020 (edited) Looking ahead, I've taken delivery of some more Canare 4S11 quad-core cable for these subs. On reflection, this might not be ideal - it's not as if I need to use low-inductance cables to avoid loss of high frequency. Any thoughts out there? Cable lengths will be about 7 m and 14 m. I have the cable now, but could use 10 AWG OFC fig-8 like I used to. I've been handed more decision time - Toll apparently had a major cyber-attack last Friday, and my plugs/sockets are still out there in the void*. I decided to try Neutrik Speakon plugs/sockets for this project, but they were posted Tuesday, and there's still no sign. Their website's in damage control. [*Edit: the sockets turned up in the letterbox later today. NLT4MP chassis "males". I'm very impressed - silver contacts, very robust, large solder tabs. Hope the "female" line plugs (NLT4FX) match that quality - I might be a convert!] Edited February 7, 2020 by BioBrian Link to comment Share on other sites More sharing options...
BioBrian Posted February 9, 2020 Author Share Posted February 9, 2020 Couldn't get far with design of the brackets to lift and attach the speakers to the ceiling, but decided to reinforce the ends to take the large screws needed for these weights. Ends are now 48 mm thick, same as the baffles. Found this accidentally cute pic from yesterday that shows one of the "audiophile*" struts - this will all be lost after tomorrow... (* secret code that the struts are Golden Ratio - 30 x 49 mm - why not?) So things started to close in today, with the 1st side panel going on. Same as this, but very sticky. 35 cc of each part of the 24-hr epoxy. Lucky it's not the little Araldite tubes. On the home s-t-r-e-t-c-h now. Need to fit in some breathing exercises. 3 Link to comment Share on other sites More sharing options...
almikel Posted February 9, 2020 Share Posted February 9, 2020 Hi Brian, even though it's all internal, and will never be seen, an artist would appreciate what you've done... I'm sure they will sound fantastic... Mike 1 Link to comment Share on other sites More sharing options...
BioBrian Posted February 11, 2020 Author Share Posted February 11, 2020 Glad you saw something too, thanks Mike. At this stage, it's a bit "who cares what they sound like?". The build's had its own intense momentum for me, maybe just something I had to do; my Briological Clock wreaking havoc? Whatever, it seems to have cracked the jinx I put on myself with a certain comment in the previous build. I know not everybody has faith in this "worst of all possible designs", but hey they're only subs. Are they the foundations of good sound, or the sewers? Vinyl users might know what I mean. Recordings are improving though. Hopefully, the difference between this build and a real gestation is that the fun part will happen at the end. 3 Link to comment Share on other sites More sharing options...
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