A good example, plywood and overkill bracing.
Most manufactures use MDF because it is cheap to buy, to work, and to finish. And you pay th eshipping so that doesn’t really concern them as much.
The mantra of cheap has been so effective that even good designers believe that it is a good speaker builing material.
dave
I want the build to be as clean as possible, would it be worth getting some sort of anti-vibration mount to install the crossovers on.
With the Selah Audio Tempesta's not much guidance is given when building the cabinet.
Internal volume must be 1ft^3 (28.32L)
Here is also the provided baffle diagram. Tempesta Baffle Front Port.pdf - Google Drive
The dimensions I have so far in autodesk are:
w=192.6mm, H=522.8mm, D=305mm, these are the internal dimensions with 25mm front baffle and 18mm sides.
Outer dimensions are: H=558.8mm (22in), W=228.6mm (9in) and 348mm deep.
Front baffle dimensions provided by Selah Audio are 22in x 9in
Here are is the cabinet with the baffles shown at another angle.
Screenshot (58).png - Google Drive
Screenshot (59).png - Google Drive
I don't think I have the resources and experience needed to do something like the B&W Matrix brace.
My woodworking skill is minimal, A friend will be helping me but I can cannibalise to much of his time with a super complicated brace. I prefer the KISS method, but at the same time don't want to compromise to much.
I also most likely don't have the resources/money and time to build experimental/multiple cabinets, I would rather spend the extra time refining/improving the cabinet design I have now.
With the Selah Audio Tempesta's not much guidance is given when building the cabinet.
Internal volume must be 1ft^3 (28.32L)
Here is also the provided baffle diagram. Tempesta Baffle Front Port.pdf - Google Drive
The dimensions I have so far in autodesk are:
w=192.6mm, H=522.8mm, D=305mm, these are the internal dimensions with 25mm front baffle and 18mm sides.
Outer dimensions are: H=558.8mm (22in), W=228.6mm (9in) and 348mm deep.
Front baffle dimensions provided by Selah Audio are 22in x 9in
Here are is the cabinet with the baffles shown at another angle.
Screenshot (58).png - Google Drive
Screenshot (59).png - Google Drive
I don't think I have the resources and experience needed to do something like the B&W Matrix brace.
My woodworking skill is minimal, A friend will be helping me but I can cannibalise to much of his time with a super complicated brace. I prefer the KISS method, but at the same time don't want to compromise to much.
I also most likely don't have the resources/money and time to build experimental/multiple cabinets, I would rather spend the extra time refining/improving the cabinet design I have now.
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At least round the dimensions up to the nearest mm… you are in a country not held back by using the imperial system. I’d push the baffle width a bit. 12mm will have next to no effect on any baffle step (the point of specifiying the baffle)he has built into the XO, but is enuff to make a difference wrt early side reflections.
Note that good 15mm ply is better than 18mm MDF and 18mm ply will cover off 25mm MDF — especially if you add a driver brace -- (Selah uses MDF i believe). In terms of keeping material all the same just use 18mm.
dave
Note that good 15mm ply is better than 18mm MDF and 18mm ply will cover off 25mm MDF — especially if you add a driver brace -- (Selah uses MDF i believe). In terms of keeping material all the same just use 18mm.
dave
I have increased the baffle width to 240mm up from 228.6mm.
Baffle Height has remained the same.
How would you recommend I mount the crossovers inside. I would prefer to mount them on the middle baffle as that is how Rick Craig over at Selah Audio built them for me.
What other changes should I make to my design then, is the bracing shown in post #22 good enough.
Baffle Height has remained the same.
How would you recommend I mount the crossovers inside. I would prefer to mount them on the middle baffle as that is how Rick Craig over at Selah Audio built them for me.
What other changes should I make to my design then, is the bracing shown in post #22 good enough.
Ok thanks for that, I'll try and figure something out. I'll probably email Rick over at Selah Audio about some of the suggestions being made.
Besides the placement of the crossover, are there any other glaring issues with the cabinet and the bracing or am I right to proceed with the building of it.
Will probably use either marine or birch 13ply, plywood for the cabinet.
Besides the placement of the crossover, are there any other glaring issues with the cabinet and the bracing or am I right to proceed with the building of it.
Will probably use either marine or birch 13ply, plywood for the cabinet.
is this good enough.
Transparent V1 - Google Drive
What kind of glue/adhesive do you recommend using to make sure that the speaker stuffing i have stays in place.
This is the speaker stuffing I have
650gsm Acrylic Speaker Dampening Material | Jaycar Electronics
I also found some pink fibreglass batting sheets in the attic of my families farmhouse, would that be more suitable than the jaycar stuff. It has been there for nearly 6 years though, but still seems to be in alright shape.
Transparent V1 - Google Drive
What kind of glue/adhesive do you recommend using to make sure that the speaker stuffing i have stays in place.
This is the speaker stuffing I have
650gsm Acrylic Speaker Dampening Material | Jaycar Electronics
I also found some pink fibreglass batting sheets in the attic of my families farmhouse, would that be more suitable than the jaycar stuff. It has been there for nearly 6 years though, but still seems to be in alright shape.
The pictures on your google drive have been coming up, but now it wants me to update my browser — it is completely up to date.
Either post the URL of the picture so it can be seen in the forum or better yet attach it to the forum database.
Is the box a bass reflex or sealed. If a BR probably not the right kind of damping — it looks awfully thick for the walls of a reflex (i’d say 25mm would be about right, fiberglass would need to be about the same, but i’d by new, who knows what has been into the attic stuff). For a reflex i prefer to use 12mm cotton or wool felt. If the box is sealed then by the time you fluff it up it will hold itself in place.
Above is similar to the jaycar stuff before & after fluffing out.
dave
Either post the URL of the picture so it can be seen in the forum or better yet attach it to the forum database.
Is the box a bass reflex or sealed. If a BR probably not the right kind of damping — it looks awfully thick for the walls of a reflex (i’d say 25mm would be about right, fiberglass would need to be about the same, but i’d by new, who knows what has been into the attic stuff). For a reflex i prefer to use 12mm cotton or wool felt. If the box is sealed then by the time you fluff it up it will hold itself in place.
Above is similar to the jaycar stuff before & after fluffing out.
dave
As is often the case on the web you are getting a bit of conflicting advice. To add to it...
Although most speaker DIYers seem to believe a stiffer cabinet is a quieter cabinet this is not supported by physics or measurements. A stiffer cabinet will move the the frequency of the lowest resonances higher but they tend to be just as loud and possibly easier to perceive. If you consider the motion of a woofer and a tweeter that are equally loud it is clear that at a higher frequency a cabinet wall would need to deflect a smaller amount to be equally loud as the same motion at a lower frequency. In addition, experiments have shown the ear to be less able to hear cabinet vibration at frequencies of a few hundred Hz compared to frequencies approaching 1 kHz which is typical for the frequency of the lowest mode in many speaker cabinets.
A subwoofer cabinet is made stiff in order to move the frequency of the lowest resonance above the passband of the driver. The stiffness then determines the size of the cabinet deflection when it is vibrating. This is relatively easy to achieve because the frequency of the low pass for a subwoofer is low.
It is possible to to take the same approach with some woofer cabinets but it is a more difficult challenge because the low pass frequency is higher. To address it successfully one might need to approach it like an engineer and look at the motion of the lowest modes, add bracing to oppose them, look at what is now the lowest modes, add bracing to oppose them, and repeat until the frequency of the lowest mode is high enough. In your case the tiny midrange is going to require the woofer to cross at a pretty high frequency and I presume you cannot simulate your CAD models? I don't think a subwoofer approach to cabinet construction is going to work well in your case.
At a resonance the forces due to stiffness and inertia cancel (same size and 180 degrees out of phase) leaving only the weak force due to damping to oppose the cabinet vibration. So if you have resonances within the passband of a driver what will make a cabinet quieter is primarily increasing the damping not the stiffness. Both MDF and plywood have small amounts of internal damping leading to high Q resonances in the cabinet. Although extensional damping (damping pads glued to inside of cabinet) is not a particularly efficient approach, it is simple and the modest amount of additional damping will significantly lower the peaks of high Q resonances.
I would be wary of changing the baffle width because this will shift in frequency how the speaker changes from beaming forward at higher frequencies to radiating equally in all directions at lower frequencies. Often called "baffle step correction" by DIY folk. In addition it will also change the strength of the diffraction off the edge of the baffle which may be taken into account in the design of more sophisticated crossovers.
Although most speaker DIYers seem to believe a stiffer cabinet is a quieter cabinet this is not supported by physics or measurements. A stiffer cabinet will move the the frequency of the lowest resonances higher but they tend to be just as loud and possibly easier to perceive. If you consider the motion of a woofer and a tweeter that are equally loud it is clear that at a higher frequency a cabinet wall would need to deflect a smaller amount to be equally loud as the same motion at a lower frequency. In addition, experiments have shown the ear to be less able to hear cabinet vibration at frequencies of a few hundred Hz compared to frequencies approaching 1 kHz which is typical for the frequency of the lowest mode in many speaker cabinets.
A subwoofer cabinet is made stiff in order to move the frequency of the lowest resonance above the passband of the driver. The stiffness then determines the size of the cabinet deflection when it is vibrating. This is relatively easy to achieve because the frequency of the low pass for a subwoofer is low.
It is possible to to take the same approach with some woofer cabinets but it is a more difficult challenge because the low pass frequency is higher. To address it successfully one might need to approach it like an engineer and look at the motion of the lowest modes, add bracing to oppose them, look at what is now the lowest modes, add bracing to oppose them, and repeat until the frequency of the lowest mode is high enough. In your case the tiny midrange is going to require the woofer to cross at a pretty high frequency and I presume you cannot simulate your CAD models? I don't think a subwoofer approach to cabinet construction is going to work well in your case.
At a resonance the forces due to stiffness and inertia cancel (same size and 180 degrees out of phase) leaving only the weak force due to damping to oppose the cabinet vibration. So if you have resonances within the passband of a driver what will make a cabinet quieter is primarily increasing the damping not the stiffness. Both MDF and plywood have small amounts of internal damping leading to high Q resonances in the cabinet. Although extensional damping (damping pads glued to inside of cabinet) is not a particularly efficient approach, it is simple and the modest amount of additional damping will significantly lower the peaks of high Q resonances.
I would be wary of changing the baffle width because this will shift in frequency how the speaker changes from beaming forward at higher frequencies to radiating equally in all directions at lower frequencies. Often called "baffle step correction" by DIY folk. In addition it will also change the strength of the diffraction off the edge of the baffle which may be taken into account in the design of more sophisticated crossovers.
If the driver motion requires less energy at high frequency to be equally loud as at low frequency then so will the cabinet motion (tweeter vs woofer again). The work done by the driver on the cabinet is the product of force and velocity. This is linear and doesn't change with frequency. So whatever is needed to move the cone at high frequencies goes into the cabinet just the same as at low frequencies.
Wrong way round. The force putting work into a high Q resonance experiences a lower damping resistance than a low Q resonance. It may take longer for the maximum amplitude of a high Q resonance to be reached because it may be a lot larger but a high Q resonance will get to a given displacement quicker than a low Q resonance because there is less damping force opposing it.
Toole discussed the Q of resonances applied to the signal. Cabinet resonances are applied to distortion not the signal. They are like the out of band resonances in a cone. Compare how unpleasant the high Q resonance of a metal cone sounds that is say 20 dB down compared to a soft damped cone. The high Q resonance persists and the ear picks it up in the way a fast disappearing low Q resonance is not. We want to damp that resonance so it is reduced in magnitude by 10-20 dB further below the signal. (Toole's resonances were above the signal in level).
It depends on the damping material and approach. Possibly yes if one splashes on some inefficient soft gloop as extensional damping material on the inside of the walls but generally not if one opts for a well designed system with an appropriate viscoelastic material and something like constrained layer damping. The high damping viscoelastic materials tend to have properties that vary strongly with frequency (and temperature) and so if they are chosen to have their maximum performance in the range of the lowest modes there isn't much to choose.
Higher order modes bend the cabinet more than lower order modes and so a higher mode at a particular frequency will damp more strongly than a low order mode at the same frequency. So having the lowest modes at a low frequency (a floppy cabinet) will mean the more easily perceived midrange frequencies are better damped. This comes at the price of a worse performance at the less easily perceived lower frequencies. So a design that seeks to shift the lowest resonances down in frequency in order to get better damping performance in the midrange frequencies needs to be careful the lowest resonance doesn't become audible. If reviewers are to be believed one or two commercial speakers that follow the "BBC approach" fail in this respect.
Increasing damping will always make a cabinet quieter. If the resonances are driven (i.e. lie within the passband of bolted on driver) then increasing stiffness tends to make little difference to the amount of sound radiated by the lowest resonances for reasons mentioned earlier. It doesn't make things worse but it doesn't make things better either.
I don't want to spend to much on materials, just what I can get hold of locally.
That leaves, MDF, Marine and Birch Ply as the options.
The baffle dimensions given by Selah Audio are 228.6mm (9in) x 558.8m (22in).
Volume most be 1ft^3 (28.32L).
I admittedly am still a bit confused over just what to do and whether the current design of my cabinet is good enough. At this stage I think I'll settle on 18mm sides and 25mm thick front. Most likely from ply.
Can anyone located in Australia, point me towards some good damping materials to use.
I already have some speaker stuffing from jaycar.
That leaves, MDF, Marine and Birch Ply as the options.
The baffle dimensions given by Selah Audio are 228.6mm (9in) x 558.8m (22in).
Volume most be 1ft^3 (28.32L).
I admittedly am still a bit confused over just what to do and whether the current design of my cabinet is good enough. At this stage I think I'll settle on 18mm sides and 25mm thick front. Most likely from ply.
Can anyone located in Australia, point me towards some good damping materials to use.
I already have some speaker stuffing from jaycar.
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