I am going to have some cabinets made out of Baltic birch plywood to house the Tang band 1808. The size will be about 12"x12"x40". A few questions:
-If I have the sides mitered to 45 degrees, glued, and braced with something like a 2"x2" where the sides meet, is that enough to get by?
-Will the wood look good sanded and oiled?
-should the driver be mounted a certain distance from the top?
-Is it necessary to use a premade PE port tube or can I just use 4" abs?
Thanks!,
v
-If I have the sides mitered to 45 degrees, glued, and braced with something like a 2"x2" where the sides meet, is that enough to get by?
-Will the wood look good sanded and oiled?
-should the driver be mounted a certain distance from the top?
-Is it necessary to use a premade PE port tube or can I just use 4" abs?
Thanks!,
v
Hi.
You could probably do with more bracing but you will have to increase the volume of the cabs to compensate for the volume that was/should have been calculated. Are you following any formula or is it guess work?
Baltic Birch is a lovely wood and will only be enhanced if sanded and oiled/sealed.
The drivers distance needs to be calculated as it will affect the response. It needs to be calculated for baffle step.
Bass unit/port frequency/resonance frequency are calculated by a formula to give the port dimensions. You cannot just put any port with any speaker in any box.
You could probably do with more bracing but you will have to increase the volume of the cabs to compensate for the volume that was/should have been calculated. Are you following any formula or is it guess work?
Baltic Birch is a lovely wood and will only be enhanced if sanded and oiled/sealed.
The drivers distance needs to be calculated as it will affect the response. It needs to be calculated for baffle step.
Bass unit/port frequency/resonance frequency are calculated by a formula to give the port dimensions. You cannot just put any port with any speaker in any box.
Because your cabinet will have a high aspect ratio, height versus width, it may tend to behave as a mltl enclosure rather than a pure bass reflex enclosure.
I actually built a mltl enclosure for my w8-1808's. I used Martin King's mathcad worksheets which are no longer available unfortunately. I get very good bass performance. In fact I ended up not using any baffle step compensation at all. I only use a .5 mh coil and a 16 ohm lpad as a variable brightness control per Bruce Rosenblit's Transcendent Sound web site. Full Range
The internal dimensions of my mltl box is 9.75" by 11.25" by 46.5". I use a 4 by 4 port centered about 4" from the bottom. I put my port on the front of the cabinet but you get a little smoother bass if you put it on the back.
I think window pane braces are a very effective way to brace an enclosure. I used two in mine and probably should have used three.
I actually built a mltl enclosure for my w8-1808's. I used Martin King's mathcad worksheets which are no longer available unfortunately. I get very good bass performance. In fact I ended up not using any baffle step compensation at all. I only use a .5 mh coil and a 16 ohm lpad as a variable brightness control per Bruce Rosenblit's Transcendent Sound web site. Full Range
The internal dimensions of my mltl box is 9.75" by 11.25" by 46.5". I use a 4 by 4 port centered about 4" from the bottom. I put my port on the front of the cabinet but you get a little smoother bass if you put it on the back.
I think window pane braces are a very effective way to brace an enclosure. I used two in mine and probably should have used three.
Every cabinet shape has resonances. An MLTL cabinet alignment is tall and narrow in order to extend the bass with the energy from a quarter-wave resonant tuned transmission line that exits into a bottom port. This is a "use the resonant force" design. Read up at:
Quarter Wavelength Loudspeaker Design
The Tang Band W8-1808 performs very nicely in a MLTL alignment, and it is worth your time to study the size options. One medium 3.3cuft volume MLTL design:
MLTL -- internal 48"H x10"W x12"D mount driver center 12" down from the top and use a 4"dia x2" long port 5" up from bottom. The stuffing specified is 0.5 pounds. Optional baffle step compensation(when away from wall) 2.5 mh coil and a 10 ohm resister in parallel.
There is also a well reviewed 4cuft MLTL box which has deeper bass(~35Hz), with slightly "lighter" midbass.
Quarter Wavelength Loudspeaker Design
The Tang Band W8-1808 performs very nicely in a MLTL alignment, and it is worth your time to study the size options. One medium 3.3cuft volume MLTL design:
MLTL -- internal 48"H x10"W x12"D mount driver center 12" down from the top and use a 4"dia x2" long port 5" up from bottom. The stuffing specified is 0.5 pounds. Optional baffle step compensation(when away from wall) 2.5 mh coil and a 10 ohm resister in parallel.
There is also a well reviewed 4cuft MLTL box which has deeper bass(~35Hz), with slightly "lighter" midbass.
I am interested in the specs of the 4 ft^3 box. I will correct frequency response with DRC for serious listening.
I would prefer to glue polyfil quilt batting to all sides as opposed to stuffing the cabinet. Does that mean I need a larger box? At the moment I have no way to simulate it.
They will be fairly close to the wall so I guess no Thiele.
I would prefer to glue polyfil quilt batting to all sides as opposed to stuffing the cabinet. Does that mean I need a larger box? At the moment I have no way to simulate it.
They will be fairly close to the wall so I guess no Thiele.
For a mltl encosure you would fill the top half of the line with polyfill type material. Martin King suggests using .25 pounds per square foot. That is about what I used. As a previous poster suggested quarter-wave.com has good information on mltl and other designs.
For bass reflex design batting glued to walls would work. There are some who advocate no damping in a bass reflex box.
For bass reflex design batting glued to walls would work. There are some who advocate no damping in a bass reflex box.
I don't usually stuff an ML-TL unless a high Q driver is used. As the 1808 is sort of low/middle-ish Q, probably lining with batting will be fine, if you are rather generous with it. I'd suggest you leave some sort of provision for adjusting as needed though.
Likewise don't glue in the ports until you try the speakers out in their positions in the room. If they are boomy you will need to go longer with them. Since they will be against the wall, there's a good chance of this. I've always had to deviate slightly from what looked good in sims.
BTW, ABS pipe is just fine. Flared fancy ports are nice, but not strictly necessary.
Likewise don't glue in the ports until you try the speakers out in their positions in the room. If they are boomy you will need to go longer with them. Since they will be against the wall, there's a good chance of this. I've always had to deviate slightly from what looked good in sims.
BTW, ABS pipe is just fine. Flared fancy ports are nice, but not strictly necessary.
Cheesecloth,pet screen wire or similar or even the open weave bags that onions or similar is packed in to block off the cab and some folks just suspend a bag full.
GM
OK, how tall, big and how close to a wall, corner and average seated ear height assuming you don't want to mess with the angles of a sloped baffle?
For example, regardless of location, I prefer the 'effortless' presentation a large cab tuned low offers and accept less peak power handling [~30 W], so for me the cab would be a ~7 ft^3 MLTL tuned to as low as ~32 Hz to take advantage of whatever room gain is available and rely on critically damping the vent to get the desired 'tightness' required for excellent transient response down to the lowest note of a grand piano and most pipe organs.
Since a cab is a little room with a doorway, its closed pipe ¼ WL eigenmodes with its odd order harmonics sets the driver, vent location, ergo the driver would ideally be down somewhere around 1/3rd - 2/5ths to get good pipe damping and the vent down around 4/5ths - 6/7ths, so cab height would be a function of ear height or how high/low from this point you prefer. Width would then be a function of the minimum practical depth.
For max pipe damping at the expense of overall response smoothness that may require substantial stuffing, place the driver, vent at the two ends.
For max peak power handling [the full 60 W rating] at the expense of no significant low bass below ~Fs, a ~2.16 ft^3/tuned to Fs suffices.
GM
For example, regardless of location, I prefer the 'effortless' presentation a large cab tuned low offers and accept less peak power handling [~30 W], so for me the cab would be a ~7 ft^3 MLTL tuned to as low as ~32 Hz to take advantage of whatever room gain is available and rely on critically damping the vent to get the desired 'tightness' required for excellent transient response down to the lowest note of a grand piano and most pipe organs.
Since a cab is a little room with a doorway, its closed pipe ¼ WL eigenmodes with its odd order harmonics sets the driver, vent location, ergo the driver would ideally be down somewhere around 1/3rd - 2/5ths to get good pipe damping and the vent down around 4/5ths - 6/7ths, so cab height would be a function of ear height or how high/low from this point you prefer. Width would then be a function of the minimum practical depth.
For max pipe damping at the expense of overall response smoothness that may require substantial stuffing, place the driver, vent at the two ends.
For max peak power handling [the full 60 W rating] at the expense of no significant low bass below ~Fs, a ~2.16 ft^3/tuned to Fs suffices.
GM
Height has no limit but the listening position is around 42". They will be about 2 feet from the wall. One is 4 feet from a corner. The other is 5" to some shelves and 30" to the corner, partially blocked by stuff on the shelves.
I think I can get by with 30W. Since I don't think I will ever get a sub good bass extension would be nice.
I think I can get by with 30W. Since I don't think I will ever get a sub good bass extension would be nice.
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