Maybe it was the vibrating backplate that absorbed all the energy. I don´t know. So I started to believe that the distance was critical, just like the length of a port.
Do you think that the length of the indirectly created tunnel around the inner enclosure has any effect ? I can change the geometri as long as the midtone is enclosed (with either 2,5 or 4 liter when using 32x32")
Do you think that the length of the indirectly created tunnel around the inner enclosure has any effect ? I can change the geometri as long as the midtone is enclosed (with either 2,5 or 4 liter when using 32x32")
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I think your tunnel around the inner enclosure will be OK. The air inside should behave like a single spring as long as there's not an extreme restriction anywhere.
If the geometry got necked down a lot, then flow and internal resonances between cavities may come into play. I haven't seen anything yet in your plan where that seems likely, but your design is skinnier than typical, so I'm guess a bit.
Interference from the vibrating back plate could definitely have been part of the problem in your previous test.
If the geometry got necked down a lot, then flow and internal resonances between cavities may come into play. I haven't seen anything yet in your plan where that seems likely, but your design is skinnier than typical, so I'm guess a bit.
Interference from the vibrating back plate could definitely have been part of the problem in your previous test.
Using 1/3" holed ribs, I would suggest stiffening the construction like this ?
Please remember that the front- and backplate is now 9mm - 1/3". Inner depth is 27mm - 1"
I think I will go with 24x24" untill I get it to work, before moving to 32x32". If nothing else then to save cost of materials.
Please remember that the front- and backplate is now 9mm - 1/3". Inner depth is 27mm - 1"
I think I will go with 24x24" untill I get it to work, before moving to 32x32". If nothing else then to save cost of materials.
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1/4" thickness may be sufficient in MDF, as long as you and your router are gentle. MDF is pretty strong in compression/tension, but is weak in bending resistance with small cross sections. You may want to run a couple small test pieces with various hole sizes and spacings to see how things behave for you.
1/8" rib thickness is probably OK if you use high quality plywood. This will decrease the gluing area, but with CNC cut parts the fit should be very good, so that helps. Plywood tends to resist bending better, so the parts won't be as fragile if you want to increase hole size.
I think I'd add a short vertical rib or two in the upper section, just because it's a pretty large span (even though it's relatively narrow).
How much does the thickness of the side frames mean ? It is currently 16mm - 2/3". Could it be thinner or should it be thicker ?
The Shapeoko CNC got stuck yesterday with the belt on one of the fasteners and made a deep cut into the 9mm MDF plate, so I have to start over :-(
I also have to fix the z-axis slider because the screws got a bit loose from the pressure (terrible noise).
I think I will use screws as fasteners next time.
What is the secrect to good bass from passive radiators - is it just volume and weight ? Hows does Tang Band get away with small volume ?
I also have to fix the z-axis slider because the screws got a bit loose from the pressure (terrible noise).
I think I will use screws as fasteners next time.
What is the secrect to good bass from passive radiators - is it just volume and weight ? Hows does Tang Band get away with small volume ?
I think you're asking about the short side walls of the enclosure here? Thinner would be OK for them because they're only about an inch tall. 1/4" thick material should be adequate there.
Tang Band usually trades quite a bit of sensitivity for the ability to get good bass in small enclosures with small drivers. To get the resonance of a small driver low, you typically need high mass, which reduces sensitivity. It's a trade-off. The driven speaker is the main factor here, not the passive radiator, but the passive radiator does have its own set of parameters that have to be considered. It's not just the passive's mass driving final response.
Beyond that, ported or passive radiator enclosures work best in a relatively small range of tunings/enclosure sizes for a particular set of driver parameters. You can step outside those, but it's always at a cost (transient ability, power handling, rapidity of roll-off, sensitivity, etc.). Some basic software is very useful when looking at these interactions. Unibox is one free Excel-based tool to design enclosures.
Hi Mattstat. I am really enjoying your help. Wish there was something I could do in return ?
But why should passive radiators not work for big volumes ? And what is small and what is big ?
But why should passive radiators not work for big volumes ? And what is small and what is big ?
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I found the following article Passive radiator speaker design - Box calculation example
but my woofers Qts of 0.64 is not even in the chart (so it is a bit difficult to do this scientifically, also with the shallow volume)
fs – 62.6 Hz
Qts – 0.64
Vas – 3.49 liters
Sd – 91.6 cm²
Vd – 36.6 cm³
δ (delta) – acoustic compliance PR / compliance enclosure = ?
However the article does note that if the radiator is made more compliant than the active speaker, higher Qts alignments will be more acceptable and are similar to the bass-reflex conterparts, with acceptable transient response.
I will check Unibox
but my woofers Qts of 0.64 is not even in the chart (so it is a bit difficult to do this scientifically, also with the shallow volume)
fs – 62.6 Hz
Qts – 0.64
Vas – 3.49 liters
Sd – 91.6 cm²
Vd – 36.6 cm³
δ (delta) – acoustic compliance PR / compliance enclosure = ?
However the article does note that if the radiator is made more compliant than the active speaker, higher Qts alignments will be more acceptable and are similar to the bass-reflex conterparts, with acceptable transient response.
I will check Unibox
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I'm glad I can help.
Passive radiators can work in large volumes. Klipsch (Forte III), Polk (the older SDA series), and Thiel have all used them in larger speakers (as have others, those were just the first that came to mind).
One of the main reasons people use passive radiators in small enclosures is that they don't take hardly any volume away from the enclosure. Trying to tune to a very low frequency in a very small enclosure typically yields a port whose volume is larger than that of the enclosure. Or the ports can get very long and skinny, which leads to turbulence/port noise. A passive radiator avoids that also.
Small and large obviously have two different meanings when it comes to an enclosure. A box may be physically large for your tastes, but quite small for what the speaker wants.
Passive radiators can work in large volumes. Klipsch (Forte III), Polk (the older SDA series), and Thiel have all used them in larger speakers (as have others, those were just the first that came to mind).
One of the main reasons people use passive radiators in small enclosures is that they don't take hardly any volume away from the enclosure. Trying to tune to a very low frequency in a very small enclosure typically yields a port whose volume is larger than that of the enclosure. Or the ports can get very long and skinny, which leads to turbulence/port noise. A passive radiator avoids that also.
Small and large obviously have two different meanings when it comes to an enclosure. A box may be physically large for your tastes, but quite small for what the speaker wants.
What woofer and passive radiators are you planning on using? Not all drivers are happy in a ported/passive radiator box. That's one of the reasons that chart stops where it does.
That doesn't mean it's impossible, but it may be suboptimal.
That doesn't mean it's impossible, but it may be suboptimal.
Dayton Audio LW150-4 was the only one that had the right formfactor. The params above are for that. It is acceptable up to 700-900 hz. 2 x standard 5" radiator pistons (20g)
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Morel woofers came close, but have a bit of a "tunnel-like" sound I don't like and they are much more expensive.
So the whole exercise is about getting as much bass as possible from the LW150-4 in 5 or 10 liter.
The midtone and tweeter in 2,5 or 4 liter already produce excellent voice reproduction.
I guess the Tang Band woofers has a low Qts
So the whole exercise is about getting as much bass as possible from the LW150-4 in 5 or 10 liter.
The midtone and tweeter in 2,5 or 4 liter already produce excellent voice reproduction.
I guess the Tang Band woofers has a low Qts
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I'm not sure what you mean by "standard 5" radiator pistons". I understand what you're implying, but passive radiators have their own set of measurements that need to be put into the model. For Unibox, that's Fs, Mms, Qms, Sd, and Xmax. It uses slightly different abbreviations to differentiate them from those of the driven unit, so for the passive radiator they're Fsp, Mmp, Qmp, Sdp, and Xpmax peak in the interface.
I honestly don´t know. This is what I got
5/6/8"inch Bass radiator Passive Speaker Woofer vibrating plate Diaphragm | eBay
and
2Pcs Woofer Speaker Passive Radiator 5/6.5/8" Sponge Edge Diaphragm Auxiliary|Speaker Accessories| - AliExpress
and
1pcs 5"/6"/8" inch Audio Woofer Speaker Passive Radiator Auxiliary Booster Bass | eBay
They are 5" weigh 20g. but I have no idea about the rest or what they were originally made for.
I can send you some if that helps ?
5/6/8"inch Bass radiator Passive Speaker Woofer vibrating plate Diaphragm | eBay
and
2Pcs Woofer Speaker Passive Radiator 5/6.5/8" Sponge Edge Diaphragm Auxiliary|Speaker Accessories| - AliExpress
and
1pcs 5"/6"/8" inch Audio Woofer Speaker Passive Radiator Auxiliary Booster Bass | eBay
They are 5" weigh 20g. but I have no idea about the rest or what they were originally made for.
I can send you some if that helps ?
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Are you open to using a different passive radiator? That's honestly what I'd do if I were prototyping a new design. The uncertainty and time involved in figuring out the other radiators' parameters would discourage me, but each person has different motivations, and I realize you may not have access to the same resources.
Also, did you run across this driver? It's shallow, but has some front protrusion, which may or may not matter to you. I like its sound overall, but I auditioned it infinite baffle for use in a friend's car.
Peerless GBS-135F25AL02-04
Peerless GBS-135F25AL02-04 5-1/4" Aluminum Cone Woofer 4 Ohm
Also, did you run across this driver? It's shallow, but has some front protrusion, which may or may not matter to you. I like its sound overall, but I auditioned it infinite baffle for use in a friend's car.
Peerless GBS-135F25AL02-04
Peerless GBS-135F25AL02-04 5-1/4" Aluminum Cone Woofer 4 Ohm
I am totally open to a different passive radiator, but would like to keep cost low.
Also I found it hard finding any 5" radiators at all. What would you suggest ?
I have already considered the Peerless woofer, but the front protrusion is a problem, because I want to mount a speaker front fabric directly on the frontpanel. Both the woofer and the radiators already have to be recessed about 5mm to achieve that (I don´t know if that generates any acoustic problems ?)
I also considered the Visaton WF 130 ND, but the protrusion (on the back) of up to 8mm. was a problem. I have to keep everything under 45mm - 1 3/4" including the backpanel.
Also I found it hard finding any 5" radiators at all. What would you suggest ?
I have already considered the Peerless woofer, but the front protrusion is a problem, because I want to mount a speaker front fabric directly on the frontpanel. Both the woofer and the radiators already have to be recessed about 5mm to achieve that (I don´t know if that generates any acoustic problems ?)
I also considered the Visaton WF 130 ND, but the protrusion (on the back) of up to 8mm. was a problem. I have to keep everything under 45mm - 1 3/4" including the backpanel.
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