I am a total novice, so please do not injure youself falling on the floor with laughter... 
I am, obviously not looking for audiophile perfection, just something that sounds nice at low to moderate volumes for everything from Italian Opera to Sunn O))) and whatever TV and movies happen to get played. I did not include a cross since I was going to play with different butterworth frequencies digitally to see what sounded good. Since it is an open box, I figured that 1/2" MDF would be sufficient, though experience would be welcome.
Thanks!
For those who cannot see links, I've attached the PDF below. [Note that the links have been tested with Chrome and Firefox on Linux. IE will probably cause problems.]
there is a PDF version here: https://www.justinzane.com/static/misc/sub.pdf
I am, obviously not looking for audiophile perfection, just something that sounds nice at low to moderate volumes for everything from Italian Opera to Sunn O))) and whatever TV and movies happen to get played. I did not include a cross since I was going to play with different butterworth frequencies digitally to see what sounded good. Since it is an open box, I figured that 1/2" MDF would be sufficient, though experience would be welcome.
Thanks!
For those who cannot see links, I've attached the PDF below. [Note that the links have been tested with Chrome and Firefox on Linux. IE will probably cause problems.]
An externally hosted image should be here but it was not working when we last tested it.
there is a PDF version here: https://www.justinzane.com/static/misc/sub.pdf
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No luck on your picture, so I don't know exactly what you have in mind, but guessing from your text:
Open box is not a viable approach unless you have an old 24 inch Heartely and the box is about 10 feet square. ( This becomes an IB. Not something for a first time build )
The box and the driver have to work as a system. You have a quite reasonable goal. There are many many well published designs that are great for a newbie project. I recommend you start there. One of my all time favorites is the Linkwitz sub. I prefer low Q sealed subs. Others like the extra boom from a ported enclosure. In any case, you need a full cabinet as it works with the driver to be a , ready.... hold on..... loudspeaker system.
Two of my subs are probably close to what you are looking at. One a Dayton Titanic III 10 inch, the other a Dayton RS series 10 inch. Both in sealed boxes of 18mm plywood from Lowes just glued together. Sealed is very forgiving; these speakers both work fine between about 50 and 80 Liters. Stuff firmly with plain old fiberglass insulation. They are driven by the small O Audio plates. My other two are a bit more exotic based on Peerless drivers.
Open box is not a viable approach unless you have an old 24 inch Heartely and the box is about 10 feet square. ( This becomes an IB. Not something for a first time build )
The box and the driver have to work as a system. You have a quite reasonable goal. There are many many well published designs that are great for a newbie project. I recommend you start there. One of my all time favorites is the Linkwitz sub. I prefer low Q sealed subs. Others like the extra boom from a ported enclosure. In any case, you need a full cabinet as it works with the driver to be a , ready.... hold on..... loudspeaker system.
Two of my subs are probably close to what you are looking at. One a Dayton Titanic III 10 inch, the other a Dayton RS series 10 inch. Both in sealed boxes of 18mm plywood from Lowes just glued together. Sealed is very forgiving; these speakers both work fine between about 50 and 80 Liters. Stuff firmly with plain old fiberglass insulation. They are driven by the small O Audio plates. My other two are a bit more exotic based on Peerless drivers.
Right.
I can say for a kick-off that it isn't an open box, as its aspect ratio is large enough for it to exhibit quarter-wave behaviour. The pressure in those (at times) will be higher than that of a sealed box.
Have you simulated your design?
It can be difficult to get such designs right at the best of times, but with no simulations to guide you, it might be great, or it might be awful (guess which is more likely).
IMHO, the woofer you've chosen won't be fantastic either. The (very) high Qts indicates a weak motor.
One of these would likely be better. There are many designs (some very bonkers) that use this woofer, but for a start try it in a ~30L cabinet tuned ~30Hz (you'll need WinISD Pro for this).
HTH
Chris
I can say for a kick-off that it isn't an open box, as its aspect ratio is large enough for it to exhibit quarter-wave behaviour. The pressure in those (at times) will be higher than that of a sealed box.
Have you simulated your design?
It can be difficult to get such designs right at the best of times, but with no simulations to guide you, it might be great, or it might be awful (guess which is more likely).
IMHO, the woofer you've chosen won't be fantastic either. The (very) high Qts indicates a weak motor.
One of these would likely be better. There are many designs (some very bonkers) that use this woofer, but for a start try it in a ~30L cabinet tuned ~30Hz (you'll need WinISD Pro for this).
HTH
Chris
@chris661: I've tried a couple different ways of modelling using online tools and have gotten mixed results. I use a Debian approved free software (open source, not free like beer) stack and therefore can't use WinISD or any of the other proprietary tools. I have written about creating an open alternative here: http://www.diyaudio.com/forums/software-tools/226835-writing-cross-platform-free-software-modeling-tool-ts-parameter-db.html.
As far as the driver goes, it is a cheap driver for a first attempt and was picked based on a number of "models" as the most likely to be useful. I do very much like your suggestion, though. I just might get one for the next project.
As far as the driver goes, it is a cheap driver for a first attempt and was picked based on a number of "models" as the most likely to be useful. I do very much like your suggestion, though. I just might get one for the next project.
Ah, PDF is OK. Large TL. Not the easiest cabinet to get right. There is so much to get right in the back chamber and TL throat.
I recommend starting sealed to understand measuring, simulation, and the plethora of box issues. . Move on to ported and then TL. I have to admit, I just plain don't get the fondness for TL for subs. Just too darn large. When I was in my 20's I had a living room with a 14 foot ceiling and played with a really big TL. ( 20') My small sealed worked better.
I recommend starting sealed to understand measuring, simulation, and the plethora of box issues. . Move on to ported and then TL. I have to admit, I just plain don't get the fondness for TL for subs. Just too darn large. When I was in my 20's I had a living room with a 14 foot ceiling and played with a really big TL. ( 20') My small sealed worked better.
I wish I could find more about what to get right. The majority of stuff I've stumbled across regarding TL design leads to M. J. King and I've had trouble getting an intuitive grasp of his work. I've also had no luck on getting advice on porting his MathCAD sheets to something FOSS.
I'm going to do a few simultaneous things. I've got a long length of Sonotube with a repositionable plug to test various sealed capacities with the given driver. I'm currently lacking a decent measurement microphone, so my measurements will not be useful in comparison to anything but themselves. Even so, they will provide feedback about the basic performance of various enclosure volumes. I've also got a 3" driver and a boatload of 3" and 2" ABS DVW pipe to do some basic tests on various TLs.
For me, the appeal of TLs is the simplicity of the concept. Short of an IB, it "feels" logically clean. Plus, the size of TLs forces a visual design change from the ubiquitous little black boxes (or white for kitchens and Apple junkies) that seems to be everywhere. I am not super creative, but I love the funky TL creations I have seen.
They often are far cruder than traditional multiway builds or sealed/ported subs, but they have a visual impact far greater. Some of the typical sealed designs I have seen here are stunning examples of fine woodcraft, but they are little differentiated from other small art objects. TLs command attention.
As far as measuring and testing go, I am quite used to doing valid and reliable studies on an array of subjects from data networks to chemicals to humans. Speakers are rather simple, so I am only limited by my [lack] of equipment.
And, finally, regarding simulation, please see the post in my sig. Thanks.
An inverse tapered TL is best for a low Qt driver where its specs dictate a very long vent to get a low vent mach, so try simming an expanding, mass loaded [vented] one similar to MJK's original ML-TQWT if you want a low tuning, otherwise a simple [straight] TL tuned to Fs/Qts to get a maximally flat impedance alignment.
GM
GM
No clue what you're referring to, but you can download MathCad's demo 8 freeware on MJK's site to run his software, you just can't save the results except by copy/pasting into WORD or similar AFAIK, but I'm mostly computer illiterate, so might want to ask about other options on his forum.
WRT using his software, it's beyond simple for basic simming as all you need to do is input the driver specs and the cab's various dimensions by highlighting each one and typing in the new. He also has a tutorial: http://www.quarter-wave.com/Back_Door/Worksheet_Tutorial_7_03_09.pdf
Even easier is using Hornresp's Loudspeaker Wizard to 'slide' your way to a design that looks promising, then inputting the results into MJK's to see how damping will affect its response.
GM
WRT using his software, it's beyond simple for basic simming as all you need to do is input the driver specs and the cab's various dimensions by highlighting each one and typing in the new. He also has a tutorial: http://www.quarter-wave.com/Back_Door/Worksheet_Tutorial_7_03_09.pdf
Even easier is using Hornresp's Loudspeaker Wizard to 'slide' your way to a design that looks promising, then inputting the results into MJK's to see how damping will affect its response.
GM
This kinda sounds like you already have the driver. Do you?
Here's some graphs. The Goldwood driver is in 3 cubic metres volume, sealed. The MCM woofer is in 30L ported tuned to 28Hz, with a small amount of series resistance to raise Qts to ~0.3.
The -3dB point is similar, but the Goldwood (even in the massive enclosure) has a peaky output due to the >0.7 Qts.
With adequate power, the MCM woofer will do >6dB more SPL than the Goldwood, with a flatter frequency response, in a cabinet 1/100th the size.
Given cabinets the same size, the Goldwood will stand more power to hit Xmax, but, as you can see, its no use as a subwoofer.
I could fire up Hornresp and simulate something more exotic, but I suspect the outcome will be similar.
Chris
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@GM: I do not use proprietary software, by choice. I value freedom greatly, and, for the same reason I love this forum -- the free exchange of ideas and opinions between interested people -- I use free software. The link in my signature gives a good explanation of what this means. The other link in my sig is to a discussion here about creating truly free acoustics tools.
Since I almost exclusively use free software, Flash Player and nVidia's binary driver to watch Hulu with my wife being the only exceptions, I do not have any Windows licenses nor is it worth it, to me, to purchase or pirate a copy simply for speaker design tools that are also closed source.
I hope I did not sound critical of you, as I am not. I just wanted to let you know, in more detail, why I can't use MJK's stuff as is. I'd really love it if someone could show me how to port MathCAD to something open.
Since I almost exclusively use free software, Flash Player and nVidia's binary driver to watch Hulu with my wife being the only exceptions, I do not have any Windows licenses nor is it worth it, to me, to purchase or pirate a copy simply for speaker design tools that are also closed source.
I hope I did not sound critical of you, as I am not. I just wanted to let you know, in more detail, why I can't use MJK's stuff as is. I'd really love it if someone could show me how to port MathCAD to something open.
@chris661: I've put the driver you suggested into gspeakers and got similar results. I'm pretty sure I'll order one soon. For now, I'll experiment with the GW-212-4 and see what box and role it sounds best in. One of the reasons that I picked it was because it was cheap enough that I'll have no regrets even if it thoroughly sucks. After all, it cost about as much as 3 "indestructible" chew toys that our little pit-mix destroys in a day.
I really appreciate the thoughtful advice and guidance!
I really appreciate the thoughtful advice and guidance!
I value freedom also, but it's my understanding that the MC demo is in effect very old freeware, so are you saying it's not?
Anyway, if I'm understanding you, seems like you could find out from MC's owner how to port it plus would have to buy a relatively expensive licensed copy, otherwise you would be pirating MC. In my ignorance of such things, your repeated request to get help for this is how it seems to me.
Specific to MJK's software, his underlying math is proprietary and not available at all AFAIK, though of course that hasn't stopped some folks from trying to hack it.
WRT Hornresp, IIRC it can be run in a Widoze emulator for mac owners, so does this help?
What about these early DOS programs? Bullock and White's Home Page
GM
@chris661: I've put the driver you suggested into gspeakers and got similar results. I'm pretty sure I'll order one soon. For now, I'll experiment with the GW-212-4 and see what box and role it sounds best in. One of the reasons that I picked it was because it was cheap enough that I'll have no regrets even if it thoroughly sucks. After all, it cost about as much as 3 "indestructible" chew toys that our little pit-mix destroys in a day.
I really appreciate the thoughtful advice and guidance!
You're welcome.
Give the Goldwood a try in a really simple H-frame (or U-frame) dipole system.
It won't go very loud, but the dipole cancellation will flatten out the peaky response, which might give you something usable.
Take lots of pictures whatever you build - they're always appreciated.
Chris
It is free only with respect to price. Free software is something different. Please read the first link in my signature to get a better description that I could write.
I have no interest in MathCAD. There are numerous very capable math and engineering programs that are free and open. What I am hoping for is that someone who is more familiar with these types of simulation than I am can suggest which one to use and perhaps how to do so with respect to this specific problem set.
His math cannot be proprietary, at least in the USA:
That being the case, it is perfectly appropriate to ask for help in applying the algorithms that he has developed and published. What M. J. King can patent are his designs that he has developed using those algorithms. He can copyright software that implements the algorithms, but he cannot copyright formulas and equations.
http://users.hal-pc.org/~bwhitejr/
You can do pretty well with the DIY Panasonic capsule mic. See Linkwitz for details. Most of use have a Behringer calibrated mic. Pretty cheap.
There were a lot of TL papers in Speaker Builder in the old days.
I fully applaud designing away from the box, however the engineer side of me reminds me that a box works pretty darn well. Most of my speakers are painted, none of them black or white. My main subs look like Chinese chests.
Speakers are simple? Ah Grasshopper, soon you shall have the truth laid before you. In time you will find we don't actually know what to measure and the kind of repeatability you may be accustomed to is just not possible. Even the moment to moment changes in air pressure exceed basic test equipment. Mode, measure, think, then realize why we all do final voicing by ear. The TL is almost as miss-understood as the horn. Simple in concept, very complex in execution. You'll see.
There were a lot of TL papers in Speaker Builder in the old days.
I fully applaud designing away from the box, however the engineer side of me reminds me that a box works pretty darn well. Most of my speakers are painted, none of them black or white. My main subs look like Chinese chests.
Speakers are simple? Ah Grasshopper, soon you shall have the truth laid before you. In time you will find we don't actually know what to measure and the kind of repeatability you may be accustomed to is just not possible. Even the moment to moment changes in air pressure exceed basic test equipment. Mode, measure, think, then realize why we all do final voicing by ear. The TL is almost as miss-understood as the horn. Simple in concept, very complex in execution. You'll see.
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