Glenn - re your post #52 - yes, the "fonken" style of high aspect ratio slot ports could be best described as a hybrid -closer to an aperiodic than standard bass reflex
As for Fonken for the F120A - http://p10hifi.net/FAL/downloads/Fonken-steen-0v81-140808-plans.pdf
Somewhere I think I have pictures of a pair made for Jim Rebman - black cones with red EnABL dots, enclosures in Macassar Ebony veneer - quite the visual statement actually. I only ever heard them driven by lower powered tube amps - Bottlehead Paramour 2A3 monoblocks, Decware ZenC, etc. so while very luscious in the midrange with a bit more impact in the bottom than the FE108EZ, it's hard to say just how much more they could do driven with a with a bit more torque.
As for Fonken for the F120A - http://p10hifi.net/FAL/downloads/Fonken-steen-0v81-140808-plans.pdf
Somewhere I think I have pictures of a pair made for Jim Rebman - black cones with red EnABL dots, enclosures in Macassar Ebony veneer - quite the visual statement actually. I only ever heard them driven by lower powered tube amps - Bottlehead Paramour 2A3 monoblocks, Decware ZenC, etc. so while very luscious in the midrange with a bit more impact in the bottom than the FE108EZ, it's hard to say just how much more they could do driven with a with a bit more torque.
Not much to elaborate on as it's mostly done empirically either by ear or measurement, though maybe AkAbak can sim it 'close enough'.
FWIW, I used 'close enough' same gap top and bottom IIRC and the panels wound up being around 30 deg relative to the corners to get the right toe in, plus tilted the baffle back to deal with 'slap echo' reflections to minimize damping required [learned from studying studio, theater room design], but this was almost 49 yrs ago when I did virtually all my major testing of concepts based on patents, published designs and a lot of info from a trip to the Altec factory, so virtually everything I tried was ancient history with me doing them for educational purposes, then materials reconfigured for the next one. Needed to do something to stay busy while the wife was pregnant.........
In short, there's no rules I'm aware of, so gaps become whatever works in your room, etc.. Wish I still had the patent number as it had some other interesting variations on a theme with some extra internal baffling.
GM
My first thought is that it might be possible to use a normal sized closed enclosure, then use a supersized aperoidic style venting system with high sound absorption material.
It's kind of a weird idea for me to explain. Imagine you take a sealed enclosure... then use a hole saw to take away as much of the enclosure on the rear and sides as possible without running into structural integrity problems. Then line the inside of he enclosure with a sound absorption material. The 3.5" version of Ultratouch Denim home insulation has a 1.15 NRC; which pretty much means it absorbs almost everything 125hz and above.
http://bondedlogic.com/pdf/denim-insulation/UltraTouch-Denim-Spec-Sheet.pdf
Even if the material can't pass that much air, I imagine that it might "virtually" expand volume the way polyfill does in a sealed enclosure.
It's kind of a weird idea for me to explain. Imagine you take a sealed enclosure... then use a hole saw to take away as much of the enclosure on the rear and sides as possible without running into structural integrity problems. Then line the inside of he enclosure with a sound absorption material. The 3.5" version of Ultratouch Denim home insulation has a 1.15 NRC; which pretty much means it absorbs almost everything 125hz and above.
http://bondedlogic.com/pdf/denim-insulation/UltraTouch-Denim-Spec-Sheet.pdf
Even if the material can't pass that much air, I imagine that it might "virtually" expand volume the way polyfill does in a sealed enclosure.
Thanks GM, simple enough to play around with, my room's relatively small so could be worth pursuing for my OB.
Xaborus.. along these sort of lines.. http://kimmosaunisto.net/CardSub/CARDSUB.html#Resistanssikotelo_2 ?
Xaborus.. along these sort of lines.. http://kimmosaunisto.net/CardSub/CARDSUB.html#Resistanssikotelo_2 ?
Yes, these are definitely good ideas. The density of the stuffing seems to be the tricky part there.
I'm learning a bit more about this, and thanks to you guys it's finally sunk in for me that there's more at play in an infinite baffle than just lowering the Qtc. Yes, you want to allow the driver to move freely, but you also need to kill the back wave so it doesn't reflect back and hit the driver. XRK971's Nautaloss that Jim linked to here on the forum is a great effort towards that end (as is, obviously the B&W Nautilus it was named after).
I'm currently leaning towards a long TL design with progressive stuffing. The problem is figuring out how to scatter or diffuse the back wave directly behind the driver so it has a chance to disappear into the "black hole" of the stuffing rather than just bouncing straight off the back wall of the box. That's where the Nautaloss shines with it's spiral construction. Unfortunately, the one dimension I don't have a lot of is depth.
I'll leave it for the back of my brain to ponder for awhile. Maybe something will shake out.
I'm learning a bit more about this, and thanks to you guys it's finally sunk in for me that there's more at play in an infinite baffle than just lowering the Qtc. Yes, you want to allow the driver to move freely, but you also need to kill the back wave so it doesn't reflect back and hit the driver. XRK971's Nautaloss that Jim linked to here on the forum is a great effort towards that end (as is, obviously the B&W Nautilus it was named after).
I'm currently leaning towards a long TL design with progressive stuffing. The problem is figuring out how to scatter or diffuse the back wave directly behind the driver so it has a chance to disappear into the "black hole" of the stuffing rather than just bouncing straight off the back wall of the box. That's where the Nautaloss shines with it's spiral construction. Unfortunately, the one dimension I don't have a lot of is depth.
I'll leave it for the back of my brain to ponder for awhile. Maybe something will shake out.
My Jordan VTL is a very shallow box, 70mm internal. There is acoustic foam behind the driver only. Also because it is such a short distance the frequency of the standing waves is very high. There's a good explanation in the Q&A section on their website
Yes, the pioneers developed numerous variations of aperiodic venting, which of course can be taken to the extreme by using chicken wire/whatever stretched over a frame [been there, done that and have periodically recommended it when appropriate], then only your imagination, material options limiting the myriad ways to create the desired composite damping membrane.
Another [once?] popular way is to apply one or more layers of [differing] materials mildly stretched over the rear of the driver to quickly get close, then fine tune it with cab lining, loose fill. Cheese cloth is the first layer to do double duty as damper and protect the driver from any loose fibers, etc., ergo recommended anytime there's there's potential for loose fibers, etc., circulating in the cab.
WRT acoustically 'expanding' a closed cab there's a point where the damping begins acting like a solid: Sub Box Polyester Fiberfill
GM
Already solved by the pioneers, i.e., the cheesecloth, etc., 'system' previously posted. 😉 All others are just variations on a theme that for the most part wound up just being marketing hype, but if going the TL route and not using the Nautilus tapered shell, then a 1/2 WL plane wave tube [PWT] is the goal.
GM
Well, a tapered shell is realistically not going to happen, given that my carpentry skills barely allow for the creation of a box. 🙂
Sadly my lack of skills and tools beyond hand tools will be a big factor in whatever I eventually decide to do. Complex designs are out due to my inability to accurately produce angles. My lack of a table saw precludes ripping to specific dimensions, so for large components I'm limited to standard board widths. This is part of why I decided on a sealed design in the first place - they're the most forgiving in terms of dimensions. (I also prefer their better transient response, and group delay characteristics.) I'm currently under the impression that a long transmission line designed entirely to eliminate the back wave would be somewhat forgiving as far as dimensions are concerned, with the stuffing being the most crucial factor. Is that correct, or have I misled myself?
Sadly my lack of skills and tools beyond hand tools will be a big factor in whatever I eventually decide to do. Complex designs are out due to my inability to accurately produce angles. My lack of a table saw precludes ripping to specific dimensions, so for large components I'm limited to standard board widths. This is part of why I decided on a sealed design in the first place - they're the most forgiving in terms of dimensions. (I also prefer their better transient response, and group delay characteristics.) I'm currently under the impression that a long transmission line designed entirely to eliminate the back wave would be somewhat forgiving as far as dimensions are concerned, with the stuffing being the most crucial factor. Is that correct, or have I misled myself?
You can easily make a ripping guide and what I used for the majority of my active speaker building 'career' and still do for long cuts since it's much more convenient to do them outside, ditto pretty much any type of jig is available in DIY form for the price of an on-line search nowadays: https://www.google.com/search?q=diy...ved=0ahUKEwihy87Yu73SAhXBxlQKHQKVDPkQ_AUICCgD
Anyway, yes; within reason, when going ~aperiodic, net cab volume [Vb] can be pretty far off and of much more importance is the driver's Fs, Qts' to get the desired response.
IME, George Augspurger's, Rick Shultz's Alpha TL design routine finds the tuning, minimum net Vb close enough and published many years ago in AudioXpress, but couldn't find it on-line and don't have mine loaded, so all I can tell you is that the pipe's Fp is Fs/Qts' with Vb and physical cut length is a function of whether polyfil or acoustic fiberglass insulation is used, with the latter being somewhat smaller.
Qts' = Qts + and series resistance: mh-audio.nl - Home
GM
Anyway, yes; within reason, when going ~aperiodic, net cab volume [Vb] can be pretty far off and of much more importance is the driver's Fs, Qts' to get the desired response.
IME, George Augspurger's, Rick Shultz's Alpha TL design routine finds the tuning, minimum net Vb close enough and published many years ago in AudioXpress, but couldn't find it on-line and don't have mine loaded, so all I can tell you is that the pipe's Fp is Fs/Qts' with Vb and physical cut length is a function of whether polyfil or acoustic fiberglass insulation is used, with the latter being somewhat smaller.
Qts' = Qts + and series resistance: mh-audio.nl - Home
GM
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I've looked at ripping guides in the past, but they were all so small and flimsy and had so much play in them that they were way more trouble than they were worth, so I gave up on the idea. When I searched just now, though, I found a couple on Amazon that have good reviews and actually look like they might be workable. Thanks for that tip. It could open up some more design possibilities for me. I might even be able to have a go at the Fonkens if I can manage the 45 degree angles on the front (Thanks for posting those plans, btw, Chris.)
I still like the transmission line idea for right now, though.
I did a search for plane wave tubes and found this thread: http://www.diyaudio.com/forums/multi-way/210557-poor-mans-plane-wave-tube.html which makes it seem surprisingly complicated, but they were discussing making something for critical measurements, whereas I'm just trying to make a speaker with nice sounding mids.
While reading that, I had the idea that I might use PVC drain pipe (as others have done), and with a couple of right angle joints run it up through the drop ceiling, where it could be just about any length I wanted. The length could be tuned quite easily in sections with simple junctions. I could hold it together with duct tape while I got it sorted out, then glue it when it was right. The only space I would lose in my office would be the pipes coming out of the ceiling, and if I didn't like the way they looked, I could always build a box around them. I'm sure there's something I'm not thinking of here.
I still like the transmission line idea for right now, though.
I did a search for plane wave tubes and found this thread: http://www.diyaudio.com/forums/multi-way/210557-poor-mans-plane-wave-tube.html which makes it seem surprisingly complicated, but they were discussing making something for critical measurements, whereas I'm just trying to make a speaker with nice sounding mids.
While reading that, I had the idea that I might use PVC drain pipe (as others have done), and with a couple of right angle joints run it up through the drop ceiling, where it could be just about any length I wanted. The length could be tuned quite easily in sections with simple junctions. I could hold it together with duct tape while I got it sorted out, then glue it when it was right. The only space I would lose in my office would be the pipes coming out of the ceiling, and if I didn't like the way they looked, I could always build a box around them. I'm sure there's something I'm not thinking of here.
Yeah, there is, unless you can get yer hands on some PINE tubes
That's easy . . . I'll just bore out the centre of a tree. 😀
You're welcome!
The vent cut angles might be a bit too much tedium without the proper tools, but are near enough strictly cosmetic, so can be box'd like the cabs they otherwise mimic in looks: https://www.google.com/search?q=onk...KHc6gClUQ_AUIBigB#tbm=isch&q=onken+speakers&*
Yeah, after I posted I realized that you probably wouldn't be able to 'see the forest for the trees', so of course wouldn't know how to best adapt it to your needs.
Basically it's just a 1/2 WL long closed tube with the driver normally at one end, but to minimize stuffing density we can offset the driver at 1/5th where one of the measurement mikes would normally be.
For the F120A it ideally would be ~264.96 cm [~104.32"] long except with the driver offset at ~52.99 cm [~20.86"] and WxD = ~496.07 cm^2 [~76.89"^2] to keep stuffing density low or heavily stuffed at ~142.92 cm^2 [~23.24"^2] recommended minimum, so in nearest round pipe sizes either an 8" or 6" dia. pipe.
Due to the driver's tiny linear travel [Xmax], low distortion power is limited to ~1 W/200 Hz/90 dB/2pi [up against a wall], but you'll get the flattest phase response, lowest group delay short of a huge reactance annulled compression horn in theory, which would also limit usable BW to ~300 Hz as the trade-off, so completely impractical in reality.
Fudging an Alpha TL in Hornresp would be ~58.3 cm [~22.96"] long with the driver offset at ~20.34 cm [~8"] and WxD = ~1345.48 cm^2 [~208.55"^2], so in nearest round pipe sizes at least 16" dia..
Same power rating applies, can't fool Mother Nature.
Damp to 'taste' 😉.
GM
Thank you so much for figuring that out for me. It would have taken me months to learn and understand enough to do that on my own, if I ever managed it. I'm still going to try to acquire the knowledge because I like to know why something works, but this will allow me to move ahead with building something.
Hopefully the weather will warm up a bit here soon so I can work on things outside. My shed is currently filled with the partially completed build of an old engine that I don't want to get full of sawdust or PVC particles, so it's outdoors only for the carpentry. The PVC pipe should be fairly easy to work with, though, if that's the route I decide to go. I could pretty much do that in place with a hacksaw, once I work out a means of mounting the drivers.
Your help has been greatly appreciated, GM. And thanks to everyone else who has contributed to my understanding here. 🙂
Hopefully the weather will warm up a bit here soon so I can work on things outside. My shed is currently filled with the partially completed build of an old engine that I don't want to get full of sawdust or PVC particles, so it's outdoors only for the carpentry. The PVC pipe should be fairly easy to work with, though, if that's the route I decide to go. I could pretty much do that in place with a hacksaw, once I work out a means of mounting the drivers.
Your help has been greatly appreciated, GM. And thanks to everyone else who has contributed to my understanding here. 🙂
Linkwitz Pluto speaker uses PVC pipe, you might get ideas for mounting driver there. What is the temperature where you are?
I had forgotten about the Linkwitz pipe speakers. They're pretty well regarded, from what I read. If my PVC pipe speakers don't sound good, I won't be able to blame the materials.
A wood disk seems to be the favoured method of attachment. I found one site that used a toilet flange to facilitate attaching the wood: Pipe_Dreams I'll have to see how the f120a matches up size-wise. They have very large magnets, which could complicate things. I've considered making a small box to mount the driver in, with a toilet flange on either end mounted on the inside to give a nice clean attachment and a funnel type entrance into the pipe. The box might allow for a bit more space to make arrangements, like the cheese cloth and stuffing to disperse the initial back wave.
The temperature here is currently -1 Celsius, so it's turning into nice day. I'm in a small town called Strathroy-Caradoc, about 20 minutes west of London, Ontario. We've had some odd weather this year, with relatively warm temperatures. With the Great Lakes not being frozen, we've had more precipitation because more moisture comes off the water. We get an odd phenomenon this time of year called "streamers" which are narrow snow storms that come off the lakes, usually southward from Lake Huron. They're often only 10 or 20 km wide, so it can be a total blizzard in one area, but perfectly clear a short distance away. We've had some of those the past few days, but they've hit on opposite sides of us, so we only have a dusting of snow on the ground right now. This has been good news for my back, because I have to clear paths in the yard for my short-legs dog, whose ancestors hailed from your part of the world. Corgis don't do well in deep snow. 🙂
A wood disk seems to be the favoured method of attachment. I found one site that used a toilet flange to facilitate attaching the wood: Pipe_Dreams I'll have to see how the f120a matches up size-wise. They have very large magnets, which could complicate things. I've considered making a small box to mount the driver in, with a toilet flange on either end mounted on the inside to give a nice clean attachment and a funnel type entrance into the pipe. The box might allow for a bit more space to make arrangements, like the cheese cloth and stuffing to disperse the initial back wave.
The temperature here is currently -1 Celsius, so it's turning into nice day. I'm in a small town called Strathroy-Caradoc, about 20 minutes west of London, Ontario. We've had some odd weather this year, with relatively warm temperatures. With the Great Lakes not being frozen, we've had more precipitation because more moisture comes off the water. We get an odd phenomenon this time of year called "streamers" which are narrow snow storms that come off the lakes, usually southward from Lake Huron. They're often only 10 or 20 km wide, so it can be a total blizzard in one area, but perfectly clear a short distance away. We've had some of those the past few days, but they've hit on opposite sides of us, so we only have a dusting of snow on the ground right now. This has been good news for my back, because I have to clear paths in the yard for my short-legs dog, whose ancestors hailed from your part of the world. Corgis don't do well in deep snow. 🙂
I wondered, after I mentioned the Pluto, whether you might be tempted at all by that design as it's very compact and suited to nearfield listening. But as an omnidirectional it might not be what you're after as regards imaging. Mounting in a small box would solve the mounting problem and allow more flexibility.
I looked on googlemaps to see where London is and went for a wander around on street view. Looks a lovely area, so much space. Here is very different, I'm between the mountains on one side and the sea on the other and find it strangely comforting in a way, they feel like a protection. The weather is very different too, we can go a whole winter without any frost, but it is very wet, there's no denying that!
I looked on googlemaps to see where London is and went for a wander around on street view. Looks a lovely area, so much space. Here is very different, I'm between the mountains on one side and the sea on the other and find it strangely comforting in a way, they feel like a protection. The weather is very different too, we can go a whole winter without any frost, but it is very wet, there's no denying that!
Mr. Pine
What exactly do you want to learn about speaker or enclosure design? I can distill the basics pretty easily.
There is also a simple guide I can link you to for WinISD, which is freeware to design sealed and ported boxes. It seems complicated at first, but ends up being extremely simple once you're used to it.
What exactly do you want to learn about speaker or enclosure design? I can distill the basics pretty easily.
There is also a simple guide I can link you to for WinISD, which is freeware to design sealed and ported boxes. It seems complicated at first, but ends up being extremely simple once you're used to it.
Much appreciated. I may have to get back to you on that offer, though. I'm afraid I'm going to have to learn at bit more to know what I don't know. 😱
I have WinISD, actually. I played around with it for many hours before I made the sealed boxes and subwoofer I currently have. It's quite interesting to see how the basic parameters interact. I'm currently running it under WINE on my Mac. I have HornResp working with WINE too, but I'm not to the point of understanding it very well, I'm afraid.
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