hehe, yep I prefer the box look as well. Tried a three sided enclosure that can be tucked into a corner. It was big and was really difficult to asseble. Had to build a jig for gluing and another jig for doing measurements. Gluing didn't go well and couldn't trim the edges with a router without another jig 
Big and complex enclosure wasn't fun...
Big and complex enclosure wasn't fun...
As has been pointed by others, rectangular boxes are easier to construct. Rectangular enclosures are able to utilize many of the same well proven woodworking construction techniques of kitchen and furniture cabinetry.
I'v always wondered why we don't see much more frequent use of Sonotube (concrete-footer forms) based cylindrical enclosures. These are ready formed, with little cabinet joinery. Apart from the difficulty of mounting even a minimal flat driver baffle to a curved surface. Which could be problematic enough to be the primary reason cylinder shapes are rarely utilized in commercial loudspeakers.
I'v always wondered why we don't see much more frequent use of Sonotube (concrete-footer forms) based cylindrical enclosures. These are ready formed, with little cabinet joinery. Apart from the difficulty of mounting even a minimal flat driver baffle to a curved surface. Which could be problematic enough to be the primary reason cylinder shapes are rarely utilized in commercial loudspeakers.
If you're considering a line configuration you might be able to get the best of both worlds: rectangular on the outside, triangular on the inside.
The Transmission-Line Loudspeaker Enclosure (Arthur R.Bailey) - [PDF Document]
"New Shimmer is both a floor wax and a dessert topping!"
SNL Transcripts: Elliot Gould: 01/10/76: Shimmer - SNL Transcripts Tonight
The Transmission-Line Loudspeaker Enclosure (Arthur R.Bailey) - [PDF Document]
"New Shimmer is both a floor wax and a dessert topping!"
SNL Transcripts: Elliot Gould: 01/10/76: Shimmer - SNL Transcripts Tonight
The long triangular shaped “Dagger” has been my rear speaker chamber of choice for mid range and full range drivers. Stuffed progressively with polyfill or fiberglass, it has essentially zero resonances detectable on measurement and the resulting frequency response is neutral and flat as if it were mounted in an open baffle. It gives the most uncolored sound for a mid range in my opinion. The triangle has a limited mouth (base diameter) though and I am now taking it one step further to make a pentagonal rear chamber, which also works very well.
These rear chambers are the basis for my 10F/RS225 FAST speakers.
10F/8424 & RS225-8 FAST / WAW Ref Monitor
In a pinch, a cone works well too. It has circular symmetry but that seems to be not an issue with stuffing filled inside. Plastic sports cones for soccer practice are readily available for use as rear driver chambers.
As far as making large speaker cabinets triangular, you can add a diagonal internal divider to make them triangular on the inside. That may be easier than making them triangular on the outside. Albeit, not as interesting looking.
These rear chambers are the basis for my 10F/RS225 FAST speakers.
10F/8424 & RS225-8 FAST / WAW Ref Monitor
In a pinch, a cone works well too. It has circular symmetry but that seems to be not an issue with stuffing filled inside. Plastic sports cones for soccer practice are readily available for use as rear driver chambers.
As far as making large speaker cabinets triangular, you can add a diagonal internal divider to make them triangular on the inside. That may be easier than making them triangular on the outside. Albeit, not as interesting looking.
My gut feeling is that the boxes shown in post #9 aren't sufficiently sloped to act much different to a regular rectangular tower. The internal standing wave along the long dimension will still be the major issue. I think the benefits are mostly negated unless you make something which is closer to an equilateral pyramid than a rectangular prism. The reason why you don't see them are because the compound cuts are difficult to make, they are space inefficient in terms of their footprint and are ugly (imho ).
).I shouldn't talk because I haven't done it but I have done Synergy horn with compound angles. I think the first hard part is getting the angles correct. The way to do that is to draw the box in 3D, e.g. using Sketchup. Once you do that, you can measure the angle and you will have accurate drawings of each piece. Then its "just" a matter of jig for your table saw to cut those angles; details are in BWaslo's famous synergy_calc spreadsheet.
The next hard part is gluing. You will learn tricks for that - one of them is masking tape out the outside of a joint to hold it closed if you can't clamp it adequately.
Of course you are going to have to veneer to cover up the imperfections produced along the way. Veneer goes on easy on the outside of a box, even if its not rectangular, so long as the corners aren't rounded.
If you do go to the trouble of a Sketchup drawing, its an easy path from there to CNC and perfect fit
One possible reason is that external shape at high mid...mid treble is more important than internal shape at LF...mid. Another reason is that longish triangular and pyramid avoid some internal resonances but not all. More difficult to build. Small internal volume compared to max dimensions.
The shape of the TMM shown on my previous post was a result of practicality more than addressing internal standing waves or aesthetics.
After making the driver and vent arrangement on the front baffle (rectangular), and allowing for sufficient "breathing room" behind the vent, the internal box volume would have been too large if making the depth constant up to the top. The slanted back was made primarily to remove enough internal volume to get the right Vb.
An added benefit was that the slanted panel created a non-parallel surface, which was thought to reduce the possibility of standing waves. Poly filling was used to line some of the panels to help reduce internal reflections as well.
While I was at it, an internal U-shaped brace was added between the woofers for additional stiffness.
There were a few angles and other dimensions to work out, but it just took a little more time. As a result, the box is quite strong and light-weight, considering the extra work and time. And the shape seems to work for me.
After making the driver and vent arrangement on the front baffle (rectangular), and allowing for sufficient "breathing room" behind the vent, the internal box volume would have been too large if making the depth constant up to the top. The slanted back was made primarily to remove enough internal volume to get the right Vb.
An added benefit was that the slanted panel created a non-parallel surface, which was thought to reduce the possibility of standing waves. Poly filling was used to line some of the panels to help reduce internal reflections as well.
While I was at it, an internal U-shaped brace was added between the woofers for additional stiffness.
There were a few angles and other dimensions to work out, but it just took a little more time. As a result, the box is quite strong and light-weight, considering the extra work and time. And the shape seems to work for me.
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Here's one of my prior posts on midrange enclosure shapes:
"Jim Moriyasu authored an article in the 7 & 8 2000 issues of Speaker Builder Magazine, "A Study of Midrange Enclosures". He tested 18 different midrange enclosures mounted on an IEC baffle, 1.65m x 1.35m. He measured frequency response and Cumulative Spectrum Decay (CSD) or waterfall plots at a near field 2". He used a Focal 5NV4212 Neoglass midrange with a phase plug, flush mounted on the baffle. Enclosures were tested with and without damping material, Acousta-Stuf at 1 lb/cu. ft."
Cube (2), small (Qtc = 0.7) & large (Qtc = 0.5)
Rectangle, golden ratio (2), small & large
Tube w/ flat end (2), small & larger
Vifa tube with hemispherical end
Pyramid, three sided
Pyramid, four sided (2), small & large
Transmission line, tubular (2), small & large
Transmission line, square
Transmission line, triangular
Anechoic Enclosure, with rigid foam insulation wedges
8" x 8" x 6" Enclosure
Egg
Spherical
So much information is shown in the plots of the articles, with so much for personal interpretation, that paying for the article e:files is worthwhile....
" Summarizing the articles results, hopefully doing the article justice :
Appropriate use of damping material and a sufficient internal volume for a Qtc of 0.5 or less is more important than shape. In general (not always), the larger enclosures performed better than the small enclosures. The damped transmission lines performed well. The undamped and damped cubic enclosures were not as resonant as expected. The undamped flat-backed tube and the undamped Vifa tapered tube were very resonant. While performing well, the justification of using a spherical or egg shaped enclosure for actual improved performance is very questionable. Beveling the rear edge of the baffle midrange opening is important."
"Jim Moriyasu authored an article in the 7 & 8 2000 issues of Speaker Builder Magazine, "A Study of Midrange Enclosures". He tested 18 different midrange enclosures mounted on an IEC baffle, 1.65m x 1.35m. He measured frequency response and Cumulative Spectrum Decay (CSD) or waterfall plots at a near field 2". He used a Focal 5NV4212 Neoglass midrange with a phase plug, flush mounted on the baffle. Enclosures were tested with and without damping material, Acousta-Stuf at 1 lb/cu. ft."
Cube (2), small (Qtc = 0.7) & large (Qtc = 0.5)
Rectangle, golden ratio (2), small & large
Tube w/ flat end (2), small & larger
Vifa tube with hemispherical end
Pyramid, three sided
Pyramid, four sided (2), small & large
Transmission line, tubular (2), small & large
Transmission line, square
Transmission line, triangular
Anechoic Enclosure, with rigid foam insulation wedges
8" x 8" x 6" Enclosure
Egg
Spherical
So much information is shown in the plots of the articles, with so much for personal interpretation, that paying for the article e:files is worthwhile....
" Summarizing the articles results, hopefully doing the article justice :
Appropriate use of damping material and a sufficient internal volume for a Qtc of 0.5 or less is more important than shape. In general (not always), the larger enclosures performed better than the small enclosures. The damped transmission lines performed well. The undamped and damped cubic enclosures were not as resonant as expected. The undamped flat-backed tube and the undamped Vifa tapered tube were very resonant. While performing well, the justification of using a spherical or egg shaped enclosure for actual improved performance is very questionable. Beveling the rear edge of the baffle midrange opening is important."
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I've stuck my entire head into a freshly-built speaker enclosure a few times. It is very revealing what you hear with your head inside the box.
There is always ambient white-noise in our environment these days (air-conditioning, cooling fans, traffic, aircraft flying overhead), and the spectrum of that broad-band noise changes dramatically inside the box. It always sounds incredibly "boxy", to the point where I can understand why some people become so horrified they start building open-baffle speakers (which, unfortunately, have even worse frequency-response problems than enclosed speakers do.)
To my surprise, I've heard people argue over the meaning of "boxy" on forums. Thinking in evolutionary terms, it would be very useful information for our ancestral hominids to know how large the dark cave they just entered is; our brains seem to be able to extract a general sense of this very quickly, i.e. if you're blindfolded and led into an unfamiliar room, you can immediately tell if it's a large space like a typical living-room, or a larger space like an auditorium, or a small space like a bathroom.
When the space around us becomes small enough, "boxy" seems to be the word we've come up with in English to describe the sound; the sound of a long series of resonant frequencies, which colour and shape every sound we hear. In evolutionary terms, that is the sound that says "the space around you is really small, back out now before you get stuck!"
I'm not surprised! Acoustic resonances in tubes strongly colour sound, as anyone can tell immediately by rolling up a magazine and speaking through it. Tubes are so good at modifying sounds that we use the strong resonant frequencies of tubes to produce the characteristic sounds of many wind instruments. Tapered tubes have very strong resonances too, which is why they're used in trumpets, for instance.
Every contemporary "line array" loudspeaker I've heard sounds bad, and part of the reason for that is the characteristic "speaking through a rolled up magazine" sound they all have. Without strenuous efforts to suppress organ-pipe resonances, a long tubular enclosure sounds horrible!
It's very Buddhist: cubical enclosures don't sound great, and neither do long skinny ones. The middle path - enclosures with dimensions that have relatively small ratios, greater than 1:1, less than 1:3 - seem to produce the best sounds.
-Flieslikeabeagle
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