I spend considerable time early on worrying about standing waves between the cabinet walls. I finally decided that as long as the cabinet walls are well damped, it doesn't make any difference. I have a couple of designs that are dead square in cross section. I can't find any evidence of standing waves. While it is intuitive that the width and depth have to be some nonintegral ratio, a bit of fiberglass erases the concern. My cabinets are lined with 5/8"-1" of acoustic fiberglass mats.
I am not suggesting that a cube is a particularly great design goal, but if handled with proper regard to the consequences, there are situations where a cube would be fine. An example of an acceptable design would be a subwoofer in a 1 foot cube completely filled with fiberglass.
Bob
I am not suggesting that a cube is a particularly great design goal, but if handled with proper regard to the consequences, there are situations where a cube would be fine. An example of an acceptable design would be a subwoofer in a 1 foot cube completely filled with fiberglass.
Bob
Cool. Good to know.
I was planning to get some 12mm thick F13 soft felt from McMaster-Carr and line the insides of the pipe with that. Then add some Acousta-Stuff where a higher stuffing density is needed.
~Tom
I was planning to get some 12mm thick F13 soft felt from McMaster-Carr and line the insides of the pipe with that. Then add some Acousta-Stuff where a higher stuffing density is needed.
~Tom
dunno if I made it plain but that was a Druid style pipe with bottom exit at the floor (perhaps the APT80 lens looks like a port) - the gap to floor has some effects - -btw Imageshack sucks - they've lost probably a hundred of my pix
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Hi,
Just like horn loaded speakers lining the walls in a MLTL is not a good idea.
Concentrating the damping where it is needed, behind the driver and in a bulk
space that damps the unwanted modes most compared to the wanted mode.
Of course in that area you can line the walls, but general lining is misleading.
rgds, sreten.
Just like horn loaded speakers lining the walls in a MLTL is not a good idea.
Concentrating the damping where it is needed, behind the driver and in a bulk
space that damps the unwanted modes most compared to the wanted mode.
Of course in that area you can line the walls, but general lining is misleading.
rgds, sreten.
agreed - - do you think some front loaded horns' back chambers benefit significantly from stuffing? my front horn experience is limited what I have (K-horns, Edgarhorn Monolith and 100Hz midbass, EV Sentry midbass and PV FH1)
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They do when they are TLs, otherwise there's not enough room to add enough stuffing. They should have at least a felt lining though if it doesn't have a loading cap.
GM
GM
I do not agree, stuffing can be any variation from only behind the driver to the entire line with various density, depending on geometry of the enclosure, driver properties, your listening room and your personal taste.
MJK´s models gives you a pretty good starting point of density and distribution of the stuffing.
Hi
Bjørn
Great thread. Concerned about port velocity for fairly large drivers - seems a compromise has to be made, larger diameter ports aren't good for MLTL's according to a post on this thread
Jeff Bagby used a slot port for his well received Morel MLTL design https://www.parts-express.com/pedocs/manuals/300-708 Solstice Kit Assembly Guide.pdf
Jeff Bagby used a slot port for his well received Morel MLTL design https://www.parts-express.com/pedocs/manuals/300-708 Solstice Kit Assembly Guide.pdf
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Hmm, missed this till just now, but FWIW, I was doing column/tower (MLTL) speakers beginning in the mid '60s with the pioneer's Av = Sd vent size with no problems, but the key is to have the driver, vent at odd harmonics, though wouldn't learn that till later as I was just lucky since not knowing any better, early on I always had the driver at the top and vent at the bottom, so 1st harmonic/fundamental, strongest pipe action = best vent damping.
High aspect ratio slots are great for big vents as they can be made somewhat aperiodic as I learned experimenting with Altec's choice for this small cinema behind screen A8 'pancake' speaker that otherwise would be a 'boombox' with a typical reflex vent of the times.
"The cross sectional area was 4*Sd. I started with the driver at 0.2*L."
"The problem is not port velocity, it is the unwanted harmonics. With little damping in the pipe, there is a decided bump in the FR plot. Yes, you can stuff the problem away, but I like to use as little stuffing as possible. so I do what I can. Using the correct port position and reducing the size of the port serves that goal. As an aside, this is also why I do not use slot ports and the bottom of the pipe."
" Port position 4", 5", 6" from bottom. I prefer 5". I need less stuffing "
" I changed the port size from 4" to 3" for 8" driver and it is cleaner sound now. "
" We have gotten very good results with high ratio slot vents in the miniOnkens, Dr. Moose's ML-TLs and a variation on Bob's A10.2 ML-TL.
The "R" added to the vent makes it more tolerent of dynamic changes in T/S parameters and keeps the box in the tuning range to a greater extent."
"The problem is not port velocity, it is the unwanted harmonics. With little damping in the pipe, there is a decided bump in the FR plot. Yes, you can stuff the problem away, but I like to use as little stuffing as possible. so I do what I can. Using the correct port position and reducing the size of the port serves that goal. As an aside, this is also why I do not use slot ports and the bottom of the pipe."
" Port position 4", 5", 6" from bottom. I prefer 5". I need less stuffing "
" I changed the port size from 4" to 3" for 8" driver and it is cleaner sound now. "
" We have gotten very good results with high ratio slot vents in the miniOnkens, Dr. Moose's ML-TLs and a variation on Bob's A10.2 ML-TL.
The "R" added to the vent makes it more tolerent of dynamic changes in T/S parameters and keeps the box in the tuning range to a greater extent."
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What about use 3 small ports in straight TL (example 1 meter). Position driver at 0.2L, first port on 0,33L, second port on 0,6L and 3rd on 0.8L
A bit closer 😉, though requires AkAbak or similar AFAIK to accurately sim it unless one of HR's new multiple pipe Wizards can work well enough: Z = (L)x ~ 0 (top), 0.217, 0.349, 0.424, 0.561 0.651, 0.714, 0.848, 0 (bottom)
Any experience with such alignment 0.217-driver, 0.349- small port, 0.651 small port, 0.848. Is it worth to try with straight TL, like MLTL but with different position of small port.
Nope, never occurred to me to try multiple staggered vents down a high aspect ratio BR or TL, AKA (ML) TL since I knew that with a vent high up close to the driver as the pioneer's dictated, it created an extended vent output into the mid bass, ending in a big notch (audible according to my young female critic's more acute hearing), so also combined with learning that the vent at the bottom did it better/smoother with no notch and not being one to 'fix what ain't broke'........