Er, yes. EBP is a simplistic, rapid rule of thumb guideline for what type of box load a given drive unit may suit. Its main use was to save time, when we had to manually calculate & plot out alignments on graph paper. With the widespread availability of modelling software it has little real value now, and if taken as anything more than the quick & dirty approximation it was meant to be, can prevent people from considering perfectly viable options. Or, on occasion, lead them straight up the garden path.
As an aside: in your post above you happened to select the lowest voltage drive for your EBP calculation, and made your assumptions on that, despite the OP noting they were using the highest for design purposes, which almost halves Qt, even with some series R added for wire, connection losses etc. 😉
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I knew, and it may be useful to readers starting out on their speaker building journey to know, that EBP stands for "Efficiency Bandwidth Product" and is calculated thus: EBP = fs/Qes
In my beginner's notebook, I have this written down: Bass reflex if EBP > 80 and Sealed if EBP < 60.
This obviously leaves a grey area between 80 and 60 where a driver may suit either type of enclosure and, as Scottmoose implies, some drivers totally defy such 'rules'.
Nonetheless, EBP is a WAF (Worthwhile Amateur Formula)! 😀
It's still usefull as a first sight info on what could works, but it's boundaries are not as absolute as some think. It just indicate what to expect. And like Scott says, you can manipulate a driver to behave different with added resistance and so so don't see EBP as an absolute factor.
When I added this driver to WinISD and brought it up to calculate the box volume, it showed a very strong preference for a vented box.
It would do, if you used the high voltage (listed as 'vented') Q values that the OP stated he was using, as you evidently have. With a Qt in the mid 0.4 region, a Vas lurking around 150 litres & an Fs of 37Hz, its fairly typical for vented box loads, or sealed if you want outright power-handling rather than LF extension.
Here's an example of how useful EBP can be on occasion.
Real driver: EBP = 156.1. Suited to vented box loading, according to the basic values assigned to EBP. Must be fine, yes? No, actually. The driver in question has a Qt of 0.84 before any series R for wire loop & connections is accounted for, a Vas of 0.7 litres, and an Fs of 165Hz. Whatever its other merits may (or may not) be: there are no good vented alignments possible with that driver. So in good-natured spirit to what I infer was a good-natured comment: yes. People here know very well what EBP is. They even know it is highly limited, circumstance dependent, and not worth a great deal.
Here's an example of how useful EBP can be on occasion.
Real driver: EBP = 156.1. Suited to vented box loading, according to the basic values assigned to EBP. Must be fine, yes? No, actually. The driver in question has a Qt of 0.84 before any series R for wire loop & connections is accounted for, a Vas of 0.7 litres, and an Fs of 165Hz. Whatever its other merits may (or may not) be: there are no good vented alignments possible with that driver. So in good-natured spirit to what I infer was a good-natured comment: yes. People here know very well what EBP is. They even know it is highly limited, circumstance dependent, and not worth a great deal.
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So many of my designs over the decades are/were somewhat contrary to EDP, so don't even think about it, much less recommend it and frankly, glad I was spared knowing about it till it was mentioned sometime after joining the WWW DIY audio community.
I decided to build the 6.6 cu ft cabinet with a trap door so I can change the volume with bricks and measure and listen to the difference.
Well, looking at the specs., that seems a trifle excessive. 
Mechanical damping at Fs (& nominally relevant to mass corner Fhm) Qms = (2pi*Fs*Mms)/Rms. Or rewritten Qms = (1/Rms)*(Sqrt (Mms/Cms)). As a field-coil, rated mechanical damping per Small's derivation varies depending on voltage drive level, as you can see from the various values given. At the highest voltage drive, which the OP says he is using / intends to use (and is the appropriate value for vented box loading), Qm is around 4.7, which while not a particularly high level of mechanical damping, is certainly not excessively low -it's roughly akin to an Altec 755C, and lower than many drivers from manufacturers like SB Acoustics. So I'm not certain describing it as having 'almost no mechanical damping' is entirely accurate.
Mechanical damping at Fs (& nominally relevant to mass corner Fhm) Qms = (2pi*Fs*Mms)/Rms. Or rewritten Qms = (1/Rms)*(Sqrt (Mms/Cms)). As a field-coil, rated mechanical damping per Small's derivation varies depending on voltage drive level, as you can see from the various values given. At the highest voltage drive, which the OP says he is using / intends to use (and is the appropriate value for vented box loading), Qm is around 4.7, which while not a particularly high level of mechanical damping, is certainly not excessively low -it's roughly akin to an Altec 755C, and lower than many drivers from manufacturers like SB Acoustics. So I'm not certain describing it as having 'almost no mechanical damping' is entirely accurate.
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Hi Scott. I'm a builder and not really versed in all you wrote. How does all that relate to the proper sized cabinet? When I first entered in all the data into WinISD the default cabinet volume was 5.3 cu ft. is that a good value?Well, looking at the specs., that seems a trifle excessive.
Mechanical damping at Fs (& nominally relevant to mass corner Fhm) Qms = (2pi*Fs*Mms)/Rms. Or rewritten Qms = (1/Rms)*(Sqrt (Mms/Cms)). As a field-coil, rated mechanical damping per Small's derivation varies depending on voltage drive level, as you can see from the various values given. At the highest voltage drive, which the OP says he is using / intends to use (and is the appropriate value for vented box loading), Qm is around 4.7, which while not a particularly high level of mechanical damping, is certainly not excessively low -it is in fact roughly akin to an Altec 755C, and lower than many drivers from manufacturers like SB Acoustics. So I'm not certain describing it as having 'almost no mechanical damping' is entirely accurate.
P.S., thanks to all you for your help.
Assuming the highest voltage drive (i.e. what's listed in the 4th data set as 'vented') & a little series resistance for speaker wire & connections, then your 5.3ft^3 can provide a more or less maximally-flat alignment.
Depending on what your goals for the speaker are in terms of bass extension & power-handling (which is basically a question of progamme material & taste) that's not bad at all, although I'd either keep it away from room boundaries, tune a few Hz lower or damp the vent to avoid excessive bass gain. Power handling is a bit limited though, so if you're running EQ, which I believe was mentioned above, I would probably be inclined toward just over 106 litres, tuned to Fs, which is what GM & I were discussing the other day, & is technically the optimum as far as that goes. It's a touch underdamped an octave above Fb, but only about 1/2dB, is better damped low down & gives a bit of extra headroom for EQ if desired.
Depending on what your goals for the speaker are in terms of bass extension & power-handling (which is basically a question of progamme material & taste) that's not bad at all, although I'd either keep it away from room boundaries, tune a few Hz lower or damp the vent to avoid excessive bass gain. Power handling is a bit limited though, so if you're running EQ, which I believe was mentioned above, I would probably be inclined toward just over 106 litres, tuned to Fs, which is what GM & I were discussing the other day, & is technically the optimum as far as that goes. It's a touch underdamped an octave above Fb, but only about 1/2dB, is better damped low down & gives a bit of extra headroom for EQ if desired.
I do hope you'll post pictures of these wonders when they're done! Always wanted to try field coils...
I certainly will. As soon as I figure out the right size of the cabs and test, I'll build nice cabs for them.
Well, it depends A LOT on the form factor, If you build for instance a cube of 163 liters you can get very nice response (see picture), going that low will limit max SPL a bit, but that might not be a huge issue for you.
The short of it: The more you squash the boundaries together towards classic tower structure, the more resonances will become troublesome.
A huge cube or even better: sphere, is a much better starting point towards battling resonances than the classic tower.
Personally I'd rather make a 2way, but if you're chasing rainbow material then a Borg Hive might be a possible solution if you prefer the darker path, the brighter path would be a coloured orb.
The short of it: The more you squash the boundaries together towards classic tower structure, the more resonances will become troublesome.
A huge cube or even better: sphere, is a much better starting point towards battling resonances than the classic tower.
Personally I'd rather make a 2way, but if you're chasing rainbow material then a Borg Hive might be a possible solution if you prefer the darker path, the brighter path would be a coloured orb.
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I'd be careful of a cube (internally); unless you can break up the dimensions a little, you end up with identical eigenmodes between all surfaces & panels: same on the vertical, same on the laterals. A sphere has a similar issue, except (driver apart) there there is a continuous internal face so you get a single, powerful standing wave on the centre that can be difficult to absorb. This is why for Helmholtz based designs or sealed boxes many prefer proportions based on irrational numbers / an acoustic ratio, with golden being aesthetically popular. It spreads them out somewhat, so less internal damping is needed. For regular vented / sealed boxes (QW / TL variations are somewhat different for obvious reasons) an efficient design is generally one that has the fewest such issues & requires the least amount of damping material. Stretching one dimension relative significantly relative to the others also can have issues as you note, unless done deliberately with any longitudinal eignmode generated being a functional part of the alignment, or significant attention given to damping it out.
Indeed, nothing is perfect, looking away from the topic of internal structure for a bit, when you squash the surfaces of the cube because a tower is a more fitting format, you actually get more modes, some longer and others are shorter, and it can become even more work to weed out the resonances. This is the main reason I prefer 2way designs, because the resonances of the larger bass section will not interfere as much with the potential of a wideband/fullrange driver, another benefit would be reducing other forms of distortion.
A closed box is not perfect either, a bit wasted potential (IMO) down low but you do get a bit less trouble with resonances because of it. Something like the sealed Nautilus is very resonance free but that also comes at a cost.
Most quarter wave designs have a lot of resonances, but it's a sacrifice many are willing to forgive, there are a lot of benefits for those who dare.
A closed box is not perfect either, a bit wasted potential (IMO) down low but you do get a bit less trouble with resonances because of it. Something like the sealed Nautilus is very resonance free but that also comes at a cost.
Most quarter wave designs have a lot of resonances, but it's a sacrifice many are willing to forgive, there are a lot of benefits for those who dare.
Yes and no. Distributing modes results in a lower overall amplitude (except in cases where you're actively using the longitudinal, i.e. a quarter-wave variation), so generally speaking they're easier to damp out with less material. Where matters can get problematic is when you have a stretched dimension which results in eigenmodes which are not either considered in advance or used as a part of the alignment; under those conditions you can get wasteful use of material, but you have that by default with a cube or sphere.
I'm not sure I understand your connection between cabinet eigenmodes & whether a speaker enclosure is a single-driver type, 2-way, 3-way or > though. A quality enclosure design accounts for proportions, internal standing waves, & as relevant acoustic isolation of midrange or other units from LF drivers etc., as well as external effects such as diffraction, minimising audible panel modes &c., so there shouldn't be any problematic modes, period, irrespective of type. If a midrange unit is not isolated from an LF driver in a cabinet design, with very few exceptions, it's better disregarded. I even use blanking plates behind tweeters in some multiway designs in order to reduce possible vibration (providing heat-dissipation is OK).
Sealed boxes or sealed LF TLs are fine & have plenty of advantages, but it depends where your priorities lie; assuming you want good extension you ideally need a driver designed for the purpose, with a low Fs & mass-corner. Unfortunately, due to typical 'modern' size constraints, most current production units are not optimised for that role, so are somewhat constrained in usable LF gain / extension as a result. On the other hand, a well-designed example automatically removes the effects of the rear radiation & offers the potential for better GD & transients low down, albeit that is usually compromised by the room to some extent or other, so I generally favour a well-damped vented, particularly in QW variations. A point to keep in mind about the latter is that while we may say 'they have a lot of resonances', they don't necessarily have many (or any) more than a lot of boxes where the alignment was created under pure Helmholtz assumptions, but actually have plenty of modes themselves without significant internal damping, as is the case with a cube or most regular boxes. It depends on exactly what sort of QW; in the case of an untapered MLQW (MLTL) they 'just' have different distribution; potentially some more depending on what your comparative baseline is, but not a vast number. Which also raises the point about 'sacrifice'. Assuming a well-designed enclosure, where you are deliberately generating & using the eigenmodes, there is no 'sacrifice', and therefore nothing to 'forgive'; they don't typically require any more damping than most regular boxes do (unless designed to use more for other purposes): it just needs to be properly designed and accounted for. Which should be the case irrespective of cabinet type.
I'm not sure I understand your connection between cabinet eigenmodes & whether a speaker enclosure is a single-driver type, 2-way, 3-way or > though. A quality enclosure design accounts for proportions, internal standing waves, & as relevant acoustic isolation of midrange or other units from LF drivers etc., as well as external effects such as diffraction, minimising audible panel modes &c., so there shouldn't be any problematic modes, period, irrespective of type. If a midrange unit is not isolated from an LF driver in a cabinet design, with very few exceptions, it's better disregarded. I even use blanking plates behind tweeters in some multiway designs in order to reduce possible vibration (providing heat-dissipation is OK).
Sealed boxes or sealed LF TLs are fine & have plenty of advantages, but it depends where your priorities lie; assuming you want good extension you ideally need a driver designed for the purpose, with a low Fs & mass-corner. Unfortunately, due to typical 'modern' size constraints, most current production units are not optimised for that role, so are somewhat constrained in usable LF gain / extension as a result. On the other hand, a well-designed example automatically removes the effects of the rear radiation & offers the potential for better GD & transients low down, albeit that is usually compromised by the room to some extent or other, so I generally favour a well-damped vented, particularly in QW variations. A point to keep in mind about the latter is that while we may say 'they have a lot of resonances', they don't necessarily have many (or any) more than a lot of boxes where the alignment was created under pure Helmholtz assumptions, but actually have plenty of modes themselves without significant internal damping, as is the case with a cube or most regular boxes. It depends on exactly what sort of QW; in the case of an untapered MLQW (MLTL) they 'just' have different distribution; potentially some more depending on what your comparative baseline is, but not a vast number. Which also raises the point about 'sacrifice'. Assuming a well-designed enclosure, where you are deliberately generating & using the eigenmodes, there is no 'sacrifice', and therefore nothing to 'forgive'; they don't typically require any more damping than most regular boxes do (unless designed to use more for other purposes): it just needs to be properly designed and accounted for. Which should be the case irrespective of cabinet type.
In general we agree.
Bass = space
IE to make a design that is more efficient for low frequencies you need more box volume, with increased box volume comes increased distance between internal surfaces, which again cause the internal resonance to shift lower and at a stronger amplitude.
I very much agree that any and all designs have their modes and resonances that need to be adressed.
My statement regarding cubes vs spheres stands, I was knowingly avoiding the topic of bracing and breaking up the internal structure because those points are equally valid for any form or design.
We are currently discussing this topic in the Fullrange section, and I personally prefer to have a bigger volume for the bass that does not negatively impact performance in that region, offloading the lower frequencies have benefits for a driver with limited xmax and power handling as you know, and at the same time having a fullrange driver in a smaller volume more optimalized towards reduced internal reflections makes a lot of sense to me, because with a smaller volume with shorter distance between parallel surfaces you shift the modes correspondingly higher up, and they are also weaker in amplitude given the same materials making them both easier to deal with and less pronounced.
However, it would be absolutely amazing to have this driver in my hands and make a big box that would be able to play every single frequency from about 25hz (would definitely use a high pass for this particular driver) up to above my limit of hearing. That would be absolutely incredible. Truly a fullrange driver.
Which is more common in floorstanding designs. Simplified: The longest internal distance produce the strongest modes.
Because:
Bass = space
IE to make a design that is more efficient for low frequencies you need more box volume, with increased box volume comes increased distance between internal surfaces, which again cause the internal resonance to shift lower and at a stronger amplitude.
I very much agree that any and all designs have their modes and resonances that need to be adressed.
My statement regarding cubes vs spheres stands, I was knowingly avoiding the topic of bracing and breaking up the internal structure because those points are equally valid for any form or design.
We are currently discussing this topic in the Fullrange section, and I personally prefer to have a bigger volume for the bass that does not negatively impact performance in that region, offloading the lower frequencies have benefits for a driver with limited xmax and power handling as you know, and at the same time having a fullrange driver in a smaller volume more optimalized towards reduced internal reflections makes a lot of sense to me, because with a smaller volume with shorter distance between parallel surfaces you shift the modes correspondingly higher up, and they are also weaker in amplitude given the same materials making them both easier to deal with and less pronounced.
However, it would be absolutely amazing to have this driver in my hands and make a big box that would be able to play every single frequency from about 25hz (would definitely use a high pass for this particular driver) up to above my limit of hearing. That would be absolutely incredible. Truly a fullrange driver.
My kind of poison too. The benefits easily outweigh the downsides with a bit of care.