I'm doing a project with two 3-way boxes (4" and 8") and I want to build the best box possible.
I was thinking about using 10mm marine plywood for the entire box and for the midranger I was thinking about using a fully sealed 7 liter egg-shaped box (But this will be done on a 3d printer).
After finishing the larger box, I would apply 10 coats of rubberized paint to the inner walls of the box (People from my city said it was necessary, why? I didn't really understand).
I'm thinking about putting audiophonic cloth on the front but I'm not sure about that yet.
Does anyone have tips or opinions?
I would like to know what would be the best design for a 3-way box?
I'm also thinking about buying the ingredients too (Speakers, components for the crossover, internal lining and everything). The amplifier will be a 100w 2.0 semi-tube amplifier.
I was thinking about using 10mm marine plywood for the entire box and for the midranger I was thinking about using a fully sealed 7 liter egg-shaped box (But this will be done on a 3d printer).
After finishing the larger box, I would apply 10 coats of rubberized paint to the inner walls of the box (People from my city said it was necessary, why? I didn't really understand).
I'm thinking about putting audiophonic cloth on the front but I'm not sure about that yet.
Does anyone have tips or opinions?
I would like to know what would be the best design for a 3-way box?
I'm also thinking about buying the ingredients too (Speakers, components for the crossover, internal lining and everything). The amplifier will be a 100w 2.0 semi-tube amplifier.
You have to decide on your woofer first as its T/S parameters will determine what type of enclosure (sealed or ported) to use as well as its air volume (and port dimensions if applicable).
P.S. The rubberised paint suppresses (damps) unwanted vibrations of the enclosure walls which can colour the sound.
P.S. The rubberised paint suppresses (damps) unwanted vibrations of the enclosure walls which can colour the sound.
While I'm a big fan of mass loading when required, rigidity can be gained 'quicker' by bracing thin panels to both raise their resonances and cross brace as required to keep it from 'breathing', then experiment with added mass and once it's determined how much is enough to make it stable, add it in the form of a (massive) removable (decorative) top once the cab's Fs is pushed high enough to get it above its pass-band (~2*Fs/effective Qts) via bracing.
What many folks IME can't seem to 'wrap their mind around' is that while rigidity increases at the cube of thickness, bracing (and better yet, starting with a very rigid material) shifts the cab's resonant pass-band up in frequency and since acoustic power rolls off exponentially (1/f), it's increasingly easier for the material's mass to damp it, ergo external damping requirements are reduced also.
Per the above, pretty much any thin material can be used if properly braced, mass loaded; my teen years' cabs were mostly packing crate cardboard with some being huge BLHs with up to 15" woofers, though the larger ones did have some scrap wood, plywood for the heavy drivers with removable scrap brick, concrete blocks, etc., to mass load them.
As a very general rule i think bass enclosures should be stiff (lots of bracing) and may even be light to move panel resonances up, out of the woofer pass band.
Midrange enclosures should be dampened and heavy, to kill resonances or move them down, again out of the pass band.
Midrange enclosures should be dampened and heavy, to kill resonances or move them down, again out of the pass band.
Topic discussed to death so search will find you things 
Not only innards of box and wall material matter, but also what's the size and shape outside. Everything matters so the box, or construct in general, is very big part of speaker sound. Simplest generalization to it is that you don't want the box to have it's own sound, which could be from panels resonating, or standing waves inside, nor bad sounds from a port.
There is lots of variables that matter on these, like panel size, material (stiffness and damping), bracing, aspect ratio of panels, position of transducers regarding panels, how the transducer is mounted and so on, a lot of variables. In short there is two things to dampen, the sound inside the box, and the box itself.
Outside affects overall directivity of the system and edge diffraction which also affects system sound in room.
Not only innards of box and wall material matter, but also what's the size and shape outside. Everything matters so the box, or construct in general, is very big part of speaker sound. Simplest generalization to it is that you don't want the box to have it's own sound, which could be from panels resonating, or standing waves inside, nor bad sounds from a port.
There is lots of variables that matter on these, like panel size, material (stiffness and damping), bracing, aspect ratio of panels, position of transducers regarding panels, how the transducer is mounted and so on, a lot of variables. In short there is two things to dampen, the sound inside the box, and the box itself.
Outside affects overall directivity of the system and edge diffraction which also affects system sound in room.
Uooah! Standing waves in a box...
I never cease to wonder about that...!
Now tell me about the room effect...
I like to read stories like that
Are you critical about standing waves in general or what? just inside speaker boxes and whether they are audible or not?
Room modes = standing waves. Flutter echo = standing waves, both happen inside the box as well, just at higher frequency where wavelength is relative to box size. Mode inside the box can show up as blip in impedance plot, which means it makes force to the cone which means it is potentially audible, after all thats what we listen, (electrical) force making the cone vibrate air molecules. You can take any acoustic simulator and see the stuff in action, so I guess your critique is towards whether standing waves are audible or not? Or do you prefer word mode to standing wave?
Certainly room modes are audible, on small room they would dominate how the bass is perceived. Room modes = modes inside box, room is just bigger than speaker box so the modes are lower in frequency, where wavelength is relative to box size. A speaker box can certainly sound boxy, whether standing waves inside box have anything to do with it beats me, but dampening the walls and insides helps it so I say yeah, they might be audible. Certainly boxy sound is one of worst offenders for good sound in general.
Room modes = standing waves. Flutter echo = standing waves, both happen inside the box as well, just at higher frequency where wavelength is relative to box size. Mode inside the box can show up as blip in impedance plot, which means it makes force to the cone which means it is potentially audible, after all thats what we listen, (electrical) force making the cone vibrate air molecules. You can take any acoustic simulator and see the stuff in action, so I guess your critique is towards whether standing waves are audible or not? Or do you prefer word mode to standing wave?
Certainly room modes are audible, on small room they would dominate how the bass is perceived. Room modes = modes inside box, room is just bigger than speaker box so the modes are lower in frequency, where wavelength is relative to box size. A speaker box can certainly sound boxy, whether standing waves inside box have anything to do with it beats me, but dampening the walls and insides helps it so I say yeah, they might be audible. Certainly boxy sound is one of worst offenders for good sound in general.
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What is elongation here? Wikipedia definition of standing wave, no mention about elongation. It's just simply two waves traveling opposing directions, such as direct sound and a reflection, whose wavelength happens to be such that a standing wave emerges. Superposition of the two (or multiple reflections) makes the result as if it didn't move but oscillates stationary https://en.wikipedia.org/wiki/Standing_wave
Inside a speaker box all wavelengths of passband of the driver exists, thus standing waves could if the box is big enough. Take a 10cm cube would have lowest standing wave of 20cm long, that's about 1715Hz. Given that only 3" driver fits on such a small box, it very likely has the mode on it's passband. A 50cm tall box would have 100cm long lowest mode, 340Hz, likely on passband even for a 3-way system.
Problem with a standing wave, sound resonating between walls inside a box, would have much higher amplitude than the input wave that set it going, which could make frequency response peak or dip outside the box because it could emit through the walls or the cone.
Superposition making constructive and destructive interference is very much core concept in acoustics which has implications in ways that aren't always first in mind. For example, take a perfect stereo system and play some favourite disco beat, kick mixed in the middle. Listening at sweet spot, holy cow it's kicking, but take few steps to side and notice it went away, even listened outside out of room modes influence. Demonstration for power alley in live gigs, or pan law for mixing and so on, sound sources interfere.
Inside a speaker box all wavelengths of passband of the driver exists, thus standing waves could if the box is big enough. Take a 10cm cube would have lowest standing wave of 20cm long, that's about 1715Hz. Given that only 3" driver fits on such a small box, it very likely has the mode on it's passband. A 50cm tall box would have 100cm long lowest mode, 340Hz, likely on passband even for a 3-way system.
Problem with a standing wave, sound resonating between walls inside a box, would have much higher amplitude than the input wave that set it going, which could make frequency response peak or dip outside the box because it could emit through the walls or the cone.
Superposition making constructive and destructive interference is very much core concept in acoustics which has implications in ways that aren't always first in mind. For example, take a perfect stereo system and play some favourite disco beat, kick mixed in the middle. Listening at sweet spot, holy cow it's kicking, but take few steps to side and notice it went away, even listened outside out of room modes influence. Demonstration for power alley in live gigs, or pan law for mixing and so on, sound sources interfere.
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Lambda is usually the wavelength, do you mean wavelength?
Wavelength and frequency relate through speed of sound. Here is harmonic series in frequency for box walls that are 30cm apart, a typical size for bookshelf speaker. If it is a two way bookshelf speaker, there are four modes within pass band of woofer if crossover is around 2.5kHz, and this is for one dimension only. If box is 15cm wide and 20cm deep there is more.
It's easy to approximate whether a sound wave fits inside: speed of sound is roughly 340m/s for easy math, so 100Hz = 3.4m, 1000Hz = 34cm, 10000cm = 3.4cm in wavelength, or in size if you will.
Basically, if one want's no standing waves to fit inside a box, the box needs to be smaller than wavelength at low pass. Actually twice as small because the first mode is half wave. So if there is two way speaker with 2.5kHz xo, that's about 13cm in wavelength. Thus, longest dimension of woofer box must be less than 6.5cm in order no standing waves within pass band fit in. What about the tweeter? It plays up to 20kHz, so it must have smaller cavity behind the dome than ~9mm, or there is a standing wave inside the tweeter, basically standing wave fits within typical tweeter dome ( diameter ~25mm ) so there will always be one or more even with tweeters assuming the back is closed.
With this simple thought experiment and recalling any hifi speaker is larger than 6cm, it basically means all hifi speakers would fit standing wave(s) inside the box except those that do not have a box. Basically only subwoofers make it without modes inside: if low pass is around 80Hz, the box could be 2m long and still no standing wave fits in because 80Hz is over 4m long in wavelength. However, the room is about 2m tall for example, so modes exist now in the room instead.
Sound wavelength is all one needs to figure this stuff out, quite simple calculus. There are more modes than these simple between two walls, but longest dimension of a box x 2 is the most problematic one always as far as I can imagine.
Wavelength and frequency relate through speed of sound. Here is harmonic series in frequency for box walls that are 30cm apart, a typical size for bookshelf speaker. If it is a two way bookshelf speaker, there are four modes within pass band of woofer if crossover is around 2.5kHz, and this is for one dimension only. If box is 15cm wide and 20cm deep there is more.
- 1. 571 Hz
- 2. 1143 Hz
- 3. 1715 Hz
- 4. 2286 Hz
- 5. 2858 Hz
- 6. 3430 Hz
- 7. 4001 Hz
- 8. 4573 Hz
It's easy to approximate whether a sound wave fits inside: speed of sound is roughly 340m/s for easy math, so 100Hz = 3.4m, 1000Hz = 34cm, 10000cm = 3.4cm in wavelength, or in size if you will.
Basically, if one want's no standing waves to fit inside a box, the box needs to be smaller than wavelength at low pass. Actually twice as small because the first mode is half wave. So if there is two way speaker with 2.5kHz xo, that's about 13cm in wavelength. Thus, longest dimension of woofer box must be less than 6.5cm in order no standing waves within pass band fit in. What about the tweeter? It plays up to 20kHz, so it must have smaller cavity behind the dome than ~9mm, or there is a standing wave inside the tweeter, basically standing wave fits within typical tweeter dome ( diameter ~25mm ) so there will always be one or more even with tweeters assuming the back is closed.
With this simple thought experiment and recalling any hifi speaker is larger than 6cm, it basically means all hifi speakers would fit standing wave(s) inside the box except those that do not have a box. Basically only subwoofers make it without modes inside: if low pass is around 80Hz, the box could be 2m long and still no standing wave fits in because 80Hz is over 4m long in wavelength. However, the room is about 2m tall for example, so modes exist now in the room instead.
Sound wavelength is all one needs to figure this stuff out, quite simple calculus. There are more modes than these simple between two walls, but longest dimension of a box x 2 is the most problematic one always as far as I can imagine.
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Just a small remark: depending on the definition of "best box possible" it may take very long time to research, plan, re-plan and build it.
And then you will realize that you could still improve the design and construction.
So why not just reduce the aim to a "reasonably good box" and start right away?
The fun at diy is the process, not the product! At least for me ...
Have a look at @augerpro 's monster box construction methods project!
And this will probably not be the last speaker you build ...
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My friend... You put something in my head that will be difficult for me to take away
My friend... You put something in my head that will be difficult for me to take away
I read the entire article and damn, he really did everything he could.Just a small remark: depending on the definition of "best box possible" it may take very long time to research, plan, re-plan and build it.
And then you will realize that you could still improve the design and construction.
So why not just reduce the aim to a "reasonably good box" and start right away?
The fun at diy is the process, not the product! At least for me ...
Have a look at @augerpro 's monster box construction methods project!
And this will probably not be the last speaker you build ...
But paying attention to everything besides most of the things shown there, I think it would be a very advanced level for me and for me who is a reader on the subject, I noticed that the thickness of the wood doesn't make such a significant difference (they exist of course, everything what you do will make a difference), but from what I've seen the ducts and internal lining are things that make a significantly BRUTAL difference.