Hello Gents,
I would like to build a metronome style cabinet for Alpair 10.3m and 12p ( I already have a pair of each). After much digging around on this forum and other places, I haven't found specific dimensions for alpair drivers. I have been to frugal horn's metronome page and checked out the table, but I don't understand how to calculate specific dimensions for the alpairs. Is it as simple as matching similar size driver for example: build the cabinet for Fostex 207 and mount the alpair 12p or are there enough differences in drivers that the dimensions of the cabinet need to be specifically matched to each driver? If the later, how do I calculate this (bear in mind my math knowledge is about algebra 2 level with a touch of geometry and no trig and 15 years rusty).
I've already built a super pensil 12, and will probably do a quick and dirty sp 10, and maybe a frugal horn too for comparison. If the sound of either of those is significantly better than the metronome, I may stick with the sp/fh, but the WAF of the metronome is huge. To quote the wife when I showed her a bunch of pics of some gorgeous pensil style cabs and a simple metronome: "Those just look like speakers. The metronome looks like a nice piece of furniture."
I would like to build a metronome style cabinet for Alpair 10.3m and 12p ( I already have a pair of each). After much digging around on this forum and other places, I haven't found specific dimensions for alpair drivers. I have been to frugal horn's metronome page and checked out the table, but I don't understand how to calculate specific dimensions for the alpairs. Is it as simple as matching similar size driver for example: build the cabinet for Fostex 207 and mount the alpair 12p or are there enough differences in drivers that the dimensions of the cabinet need to be specifically matched to each driver? If the later, how do I calculate this (bear in mind my math knowledge is about algebra 2 level with a touch of geometry and no trig and 15 years rusty).
I've already built a super pensil 12, and will probably do a quick and dirty sp 10, and maybe a frugal horn too for comparison. If the sound of either of those is significantly better than the metronome, I may stick with the sp/fh, but the WAF of the metronome is huge. To quote the wife when I showed her a bunch of pics of some gorgeous pensil style cabs and a simple metronome: "Those just look like speakers. The metronome looks like a nice piece of furniture."
Interesting thing, that WAF - after more than a few ungainly / exotics in my first dozen or so years in this hobby ( ESL57, Tangent RS8, DQ10, Acoustat 2, DIY open baffles with Viston B200, even the rather plain Ditton 66), she's much more amenable to as small a floorstander as possible. We've had a succession of the little Castle Microtowers fitted with different drivers in the upstairs living room with which she's been happy. Even something only slightly larger and needing more floor space such as the FH3 are granted temporary visitation rites in her space.
Downstairs video system has more freedom, but with furnishings and an awkward floorplan, it's still a tight squeeze when you start looking at 7.1 channels
As for the Metronome, I've never built a pair, and only heard a small one - maybe 10? yrs ago, but it is my understanding that there is "math" required for new models not listed on the tables posted at http://www.frugal-horn.com/metronome-table.html
There are a few members here quite familiar with the design topology who may be able to offer advice, and there may already exist plans for such an enclosure. Based on my experience with the 12P, I'd imagine the requisite size might surpass even the most accepting wife -factor.
Downstairs video system has more freedom, but with furnishings and an awkward floorplan, it's still a tight squeeze when you start looking at 7.1 channels
As for the Metronome, I've never built a pair, and only heard a small one - maybe 10? yrs ago, but it is my understanding that there is "math" required for new models not listed on the tables posted at http://www.frugal-horn.com/metronome-table.html
There are a few members here quite familiar with the design topology who may be able to offer advice, and there may already exist plans for such an enclosure. Based on my experience with the 12P, I'd imagine the requisite size might surpass even the most accepting wife -factor.
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yea..... my wife would repeat her quote if I showed her those exotic monsters... that is, if she were feeling in a polite mood 
I have some freedom yet. one pair will end up in my music studio where I teach lessons, the other in our living room. She really liked the "cute" OB I made for her (see here). To bad it was the worst design I could have done acoustically. My musician's ear wouldn't allow for the sound, so I did a single quick and dirty SP (out of nice maple ply but unfinished) for comparison which promptly got shoved in a corner out of sight while the two OB ones are displayed on top of our upright piano (one with a driver, the other without). Every time I walk by and listen to them they keep tormenting me with what should have been.... Once I finish the other woodworking project (hopefully before summer), I can get back to the speakers. Meantime, I'm doing my research.
I have some freedom yet. one pair will end up in my music studio where I teach lessons, the other in our living room. She really liked the "cute" OB I made for her (see here). To bad it was the worst design I could have done acoustically. My musician's ear wouldn't allow for the sound, so I did a single quick and dirty SP (out of nice maple ply but unfinished) for comparison which promptly got shoved in a corner out of sight while the two OB ones are displayed on top of our upright piano (one with a driver, the other without). Every time I walk by and listen to them they keep tormenting me with what should have been.... Once I finish the other woodworking project (hopefully before summer), I can get back to the speakers. Meantime, I'm doing my research.
Metronomes can be modelled in Hornresp. Make sure L12 and L23 sections are conical.
Input your driver parameters and then...
Offset driver,
S1=0.1
S2=area at the driver
S3=area at bottom
S4=port area
S5=port area
L12=Vertical distance from top to driver
L23=Vertical distance driver to bottom
L34=0.1
L45=port length
Note that the port is often close to the floor, so the area under the cabinet can contribute to the port length. Add half the cabinet with to L45 to get an idea of what might happen.
Chris
Input your driver parameters and then...
Offset driver,
S1=0.1
S2=area at the driver
S3=area at bottom
S4=port area
S5=port area
L12=Vertical distance from top to driver
L23=Vertical distance driver to bottom
L34=0.1
L45=port length
Note that the port is often close to the floor, so the area under the cabinet can contribute to the port length. Add half the cabinet with to L45 to get an idea of what might happen.
Chris
thanks, I just downloaded the program. Looking forward to reading the manual and figuring out the program. Real quick, can the program calculate the ideal dimensions of the enclosure or is it more a matter of trying a bunch of different dimensions out, the program shows you the theoretical results and you pick the "best" one?
No, only certain horn profiles. Note too that due to its 'pure' programming, a good performing sim typically looks pretty rough compared to one done using MJK's MathCad software [no longer available AFAIK] or even LA's somewhat easier to use/better looking sims, once all are damped: Leonard Audio | Audio Engineering Resources
For instance, save the below file in HR's IMPORT folder, then click on it to install as a Record to view, save, modify, etc.. It's what I call a [ML] horn, though could be built as a Metronome by double clicking on the PAR [parabolic] expansion and change it to CON [conical].
Notice it's raw, beyond horrible, response Vs the much more smooth/'organic' one that displays in the LOUDSPEAKER WIZARD, though still will be a bit rough compared to MJK's, with LA's being somewhere in between the two.
GM
For instance, save the below file in HR's IMPORT folder, then click on it to install as a Record to view, save, modify, etc.. It's what I call a [ML] horn, though could be built as a Metronome by double clicking on the PAR [parabolic] expansion and change it to CON [conical].
Notice it's raw, beyond horrible, response Vs the much more smooth/'organic' one that displays in the LOUDSPEAKER WIZARD, though still will be a bit rough compared to MJK's, with LA's being somewhere in between the two.
GM
Thanks for the leads. I'll be reporting back with questions once I have a chance to digest and learn/play with this software a bit.
Meantime, here's a story/picture show: Back in the 60s/70s my grandfather wanted to build a nice set of speakers and went to his brother inlaw for advice on what to get/build. My uncle was an engineer and exec at GM at the time where he helped develop stereo audio for cars and as a side hobby designed and built hollywood level movie theaters and sound systems for execs' homes in the Detroit area. This was their solution to WAF:
Meantime, here's a story/picture show: Back in the 60s/70s my grandfather wanted to build a nice set of speakers and went to his brother inlaw for advice on what to get/build. My uncle was an engineer and exec at GM at the time where he helped develop stereo audio for cars and as a side hobby designed and built hollywood level movie theaters and sound systems for execs' homes in the Detroit area. This was their solution to WAF:
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Here's pics from the inside of the other one. For some reason he went with a different driver the 601-8D. Both cabinets were clearly designed for the 605. Unfortunately my grandfather died before I had a chance to ask him why the mis-matched drivers. My suspicion is it was an availability/money thing. But I don't know. The top of the cabinet is ~1" thick solid slate. The last pic is an old one for size comparison. The bookshelf speaker on top is a Jamo classic 4.
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Thanks. Worked great. Now if I wanted to build the tqwt, I would need 4 boards with an inner dimension of the following:
3.75" x 50 9/64" x 9" x 50 9/64"
outer dimensions would be larger to accommodate for the thickness of the plywood. This would give an open base (smaller end) of 3.75" x 3.75" or ~14"^2. The top (larger end) would be ~9" x 9" (actually slightly smaller)and closed. Center of the speaker would go 16 3/4" from the top (larger end). I threw the two ends into sketchup (3.75"x2 and 9" x2). Then, separated them by 50". Then, made sure to align the centers. Finally, drew lines from corner to corner. I've attached a png file with a crude not to scale drawing of a single board marking the angle of each corner. Am I on the right track? Also, wondering if I could turn the speaker upside down--large end on the bottom--in order to have something that looked sort of like the metrome shape. I know it would put the driver awfully low to the floor. Just theorizing.
3.75" x 50 9/64" x 9" x 50 9/64"
outer dimensions would be larger to accommodate for the thickness of the plywood. This would give an open base (smaller end) of 3.75" x 3.75" or ~14"^2. The top (larger end) would be ~9" x 9" (actually slightly smaller)and closed. Center of the speaker would go 16 3/4" from the top (larger end). I threw the two ends into sketchup (3.75"x2 and 9" x2). Then, separated them by 50". Then, made sure to align the centers. Finally, drew lines from corner to corner. I've attached a png file with a crude not to scale drawing of a single board marking the angle of each corner. Am I on the right track? Also, wondering if I could turn the speaker upside down--large end on the bottom--in order to have something that looked sort of like the metrome shape. I know it would put the driver awfully low to the floor. Just theorizing.
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You're welcome!
Well, don't know about the angles, but you can calculate them here: Polar - Rectangular Coordinate Conversion Calculator
As to low mounting the driver, this is very room, speaker/listening position layout, etc., dependent and one should take floor bounce into effect if other than a wide range woofer: https://mehlau.net/audio/floorbounce/
Easy enough to get a clue though, just prop the driver up at the approximate angle on some open cell foam or similar on top of a chair, box[es], whatever to see if you can get past the dominant desire to hear it where you see it.
GM
Well, don't know about the angles, but you can calculate them here: Polar - Rectangular Coordinate Conversion Calculator
As to low mounting the driver, this is very room, speaker/listening position layout, etc., dependent and one should take floor bounce into effect if other than a wide range woofer: https://mehlau.net/audio/floorbounce/
Easy enough to get a clue though, just prop the driver up at the approximate angle on some open cell foam or similar on top of a chair, box[es], whatever to see if you can get past the dominant desire to hear it where you see it.
GM
I got the angle by measuring in sketchup. It's a pretty awesome program if you haven't tried it. Free for personal use.
So to continue with the idea of turning the box upside down, if I put the enclosure on a stand roughly 20" high, that would put the driver about 4ft off the ground. Of course the whole thing would be ~6ft tall, and there would be a large unused space under the speaker. In that light, I'll explore using that space as part of the enclosure first. Maybe it'll work out.... maybe not. We'll see what LATL says....
So to continue with the idea of turning the box upside down, if I put the enclosure on a stand roughly 20" high, that would put the driver about 4ft off the ground. Of course the whole thing would be ~6ft tall, and there would be a large unused space under the speaker. In that light, I'll explore using that space as part of the enclosure first. Maybe it'll work out.... maybe not. We'll see what LATL says....
Here's a metronome draft. Summary:
Start Area: 36" (6x6)
End Area: 155" (12.5x12.5)
Total Volume: 90.75 L
Length: 72"
Driver Pos: 24" (48" off floor)
Stuffed: 0.3lb/ft3
ML: 6x6x4 PVC Y attached to a 4-6" length of 4" PVC pipe, or I may build something out of wood, not sure yet.
Am I on the right track?
Start Area: 36" (6x6)
End Area: 155" (12.5x12.5)
Total Volume: 90.75 L
Length: 72"
Driver Pos: 24" (48" off floor)
Stuffed: 0.3lb/ft3
ML: 6x6x4 PVC Y attached to a 4-6" length of 4" PVC pipe, or I may build something out of wood, not sure yet.
Am I on the right track?
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Thanks, known about it since it came out ages ago and even have a subscription to all its updates, etc., but personally haven't had any use to justify the steep learning curve, preferring to [hopefully] use my time more productively on the various forums.
Yeah, if you're going to space it up, might as well use it to make more [mid]bass.
GM
6x6x4 pvc y to 4" pvc straight pipe.
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It's a bit crazy, but an existing piece, inside the enclosure so out of sight. I calculated the openings of the 2, 6" pipes at the end of the y for the total area of that element end.
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Thanks, known about it since it came out ages ago and even have a subscription to all its updates, etc., but personally haven't had any use to justify the steep learning curve, preferring to [hopefully] use my time more productively on the various forums.
Yeah, if you're going to space it up, might as well use it to make more [mid]bass.
GM
I started w/sketchup for wood working, basically modelling standard size boards and then assembling. The learning curve wasn't to bad. At least for basic shapes. Complex curves/shapes is trickier but not so much if you assemble piece.
One model I played with had the low spike at or below 20hz
Speaking of the spike, I'm concerned about that -3db+ dip in the low range before the spike at ~30hz as well as the drop off above 10k. Compared to that MLTL which is nearly flat from ~40hz up, will this curve likely be annoying or still ok?
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