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That ROAR12 design has a net volume of 180 litres.
B&C recommends an enclosure volume of 40 litres tuned to 43 Hz for the 12TBX100.
A pair of those drivers in straight offset-driver TL of 68 litres net will get you over just over 125 dB @ 40 Hz before Xmax is exceeded in the passband.
Of course, more power is required and no-one is going to give you the extra driver, but power is cheap these days - IMO the main reason why BR boxes are so much more acceptable now than they used to be, as I previously said.
Why two drivers? I think it might be difficult to squeeze the 12TBX100 into a single-driver ODTL, based on its parameters 🙂
B&C recommends an enclosure volume of 40 litres tuned to 43 Hz for the 12TBX100.
A pair of those drivers in straight offset-driver TL of 68 litres net will get you over just over 125 dB @ 40 Hz before Xmax is exceeded in the passband.
Of course, more power is required and no-one is going to give you the extra driver, but power is cheap these days - IMO the main reason why BR boxes are so much more acceptable now than they used to be, as I previously said.
Why two drivers? I think it might be difficult to squeeze the 12TBX100 into a single-driver ODTL, based on its parameters 🙂
The diversity available outside of trying to be ‘Fair’ in ‘comparison’ is a struggle.
If 50 liters fits where it's going, im not gonna contemplate if, im
Lolking in sim for where it'll work best. in a paraflex another driver is not even a remote need but its fun to use a few ideas it provides in aesthetics or even ‘offset basket distance to an entry or exit of a ported VTC. L12 is 0.1cm. But two qw pipes is a strange thing. Its risr vs oarafkex and a siniksr result
Apples to apples NOBODY is gonna help the OP unless they are trying . but fart bass at a vent is a variety of indigestion issues and noises at pressures we sphincter out. Qw landscape is a large canvas of opportunity. if you like OD TL or similar, them i give you an extra 50 liters if you need it, because if you do, youll show us the result and we will all love it. The world still is at 8.6 hz regardless?? It doesnt care if we prefer more vent or less, even if we think its a better sound or way better. we agree, but that doesnt help unless we make it true. and the ROAR sounds amazingly stupid. But thats not ‘bad’ , its a STUPID amount of exciting and impressive if wanted to feel/hear.
Nobody is going to hear anything . We are too busy nickel and diming little details to see big changes. We shoot out own foot(s)...
You're looking at the wrong bit.
What's the air velocity in the narrow part of the cabinet?
It's no surprise that the air velocity at the mouth is low. What I'm concerned about is compression caused by trying to shove a lot of air through a long and narrow tunnel, with a few bends.
Chris
The OP's question was about the vast majority of PA subs being of the vented variety. IMO the reason why is because of the availability of cheap power. Which allows you to get more output from smaller, easier to transport systems.
The ODTL addresses one of the main issues of BR systems (power compression of the vent output), without significantly increasing box size requirements and impacting the midbass response.
BR systems do have another disadvantage (the extra heat that has to be dissipated from the driver when driven at the same SPL levels as higher-order systems), but the drivers available these days tend to have much higher power ratings than older drivers anyway. It's almost like they're designed to be used in smaller boxes at higher power levels 😉
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I want to tell you anything thst helps. but theres a lot of solutions if im solving a problem. The thing is, im not(iMo), i am trying to to solve one for you while not telling you whats in my garage or suv thats even smaller if bracing is accounted but cone area isnt. A lot of things can be done to oblige your legitamite concerns, especially if itll promote the idea this HOqW stuff might be a thing youd enjoy to hear or might like? thst woyld ne perfec😀t!
It's a good question. I don't think it would have as much distortion as high air velocity in a narrow pipe that opens out to open air (due to turbulence at the end of the pipe), but it should still be there.
There is unfortunately a significant absence of extensive testing results of the ROAR and Paraflex designs, so it's all guesswork at the moment.
I dont think anyone needs to know these things, its all too true. i think we need to flip the darwin and evolve beyond stuff thats no longer needed as a species that uses negative lymbic functions to survive in a world of denying things as woukda coulda shoulda risked with no more saber tooth tigers and bears to eat us😀 ?? gamble on the funny looking speaker or knowbody will. Sheerp die in a wolfs den? Its a real trait and a human problem. Big boobs are easy too, but do we love those and mary them? No! theres gotta be MORE to her then that alone. and speakers might need to be accepted as more is potentially ‘more’, not easier is more of nothing tried...
We can change that or leave it alone. Either way it's still true right Now. lets go build speakers and the more THAMs and ODTLs the better!! Bass reflex😀 is a crime 🙂 (jk
Doesnt have to be. just needs a workbook and its promotes the cause (again) and certainly an ambassador to the idea of anything is potentially great to anyones neefs or ears.
Also, there are Huge fans of both of those that are on this forum and also have the means to provide exactly that, Brian(testing)?? What would we ask if they offered or were willing?. It might happen??
An 18ds115 in a type C, and also in a RoaR that was up for observation not public comparison. That ship sailed, its time to embrace all as wonderful or take a back seat to new and improved anything at any level. they don't exist without eachother. in fact they cant. The mystery is only a few car audio trophies into reality for the most part. One ROAR one Parafkex. its likely turbulent. But you'd be surprised if assuming its a disaster . The funnest parts are the bragging rights to the song played that follows the burp that one spl.. then is great listening shared as well.
(Pic) this is stupid!! But tell me how you dont want to have a few moments ro experience it? This is only possible because of PA, THAM, progress, etc
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The one thing I'd want to see from the testing is power sweeps through the passband at different levels until the driver's Pmax is exceeded or 10% in the passband is recorded. Overlaying those results will show if any dynamic power compression of any significance is happening.
I want to add Brian's point about power becoming cheap, which is not only correct but also, I believe, a big part of the answer, I want to recall hearing a similar statement from Tony Andrew's on this topic.
However true that might be, I struggling to put it down in bullit form in their favor as per below, it's more more of a disadvantage but one that we now can compensate for without breaking the bank, but even so there is still the need for twice the driver complement in order to achieve what it does.
I write fairly compact seeing as modern low tuned 218's is a fair bit larger than they used to be, mainly concerning the depth, a typical rough set of dimensions would be something like H:1200, W:600, D:900.
So far we have concluded that Bass reflex is presently the most common offering in the <~100Hz range for professional applications because it is:
Flexible. (multipurpose -> economics)
Scalable. (no need for application specific designs -> economics)
Familiar. (you know what to expect -> convenience/economics)
Compact. (for it's output and range, logistics -> economics)
Light. (for it's output and tuning, logistics -> economics)
Popular. (nothing succeeds like success -> convinience/economics)
Simple. (easy to get right, cheap to build -> economics)
And I have to agree concerning the state of the technical documentation for the ROAR and paraflex designs, it is not on par with what is available for the more common design principles, and because of that credibility suffers when we try to convey our impressions, this does not mean we are wrong, it just means we have not proved it yet.
However true that might be, I struggling to put it down in bullit form in their favor as per below, it's more more of a disadvantage but one that we now can compensate for without breaking the bank, but even so there is still the need for twice the driver complement in order to achieve what it does.
I write fairly compact seeing as modern low tuned 218's is a fair bit larger than they used to be, mainly concerning the depth, a typical rough set of dimensions would be something like H:1200, W:600, D:900.
So far we have concluded that Bass reflex is presently the most common offering in the <~100Hz range for professional applications because it is:
Flexible. (multipurpose -> economics)
Scalable. (no need for application specific designs -> economics)
Familiar. (you know what to expect -> convenience/economics)
Compact. (for it's output and range, logistics -> economics)
Light. (for it's output and tuning, logistics -> economics)
Popular. (nothing succeeds like success -> convinience/economics)
Simple. (easy to get right, cheap to build -> economics)
And I have to agree concerning the state of the technical documentation for the ROAR and paraflex designs, it is not on par with what is available for the more common design principles, and because of that credibility suffers when we try to convey our impressions, this does not mean we are wrong, it just means we have not proved it yet.
I have to say that in my experience the fact that the 218 BR is the standard weapon of choise is a bit curious, in these days having a sustainable and environmental approach as a core part of your business is a given, this tends to mean that the most efficient solution is getting the most focus.
In the automotive industry it is long recognized that each of the approx. 15.000 parts that makes up the vehicle has an environmental impact since all these parts needs to be manufactured, transported, and eventually recycled, this should be considered in any high volume production.
In that light how can it be a good idea to have set on a solution that requires roughly twice the power and twice the amount unorganic material to do the job?
In the automotive industry it is long recognized that each of the approx. 15.000 parts that makes up the vehicle has an environmental impact since all these parts needs to be manufactured, transported, and eventually recycled, this should be considered in any high volume production.
In that light how can it be a good idea to have set on a solution that requires roughly twice the power and twice the amount unorganic material to do the job?
This should be done with transient signals too.
A steady state sine with slowly increasing frequency will excite the helmholtz resonance slow enough to bypass the slow ramp up of the resonance - often a few wavelengths or so.
In my 8th order BP build we did bottom out the cheap car bass driver with only a few hundred watts and transient signals. It could easily take the full 400 watts from the amp (clip indicator blinking once in a while) with steady state signals or low dynamic range music. We never saw the clip indicator even once with the transient signals - despite hearing the hard knock of the driver voice coil bottoming out.
I pushed my ROAR12 with a 2000 watt amp all the way to amp clipping without any high pass filter and the driver never came close to xmax. The voice coil got very hot really fast though...
Agreed, double 18"s can get pretty big, epecially to achieve low tuning of say 30Hz and below.
And I'll say again, imo getting down that low is still easier with a BR than any other design I've seen.
Another point worth mentioning i think...is a BR is an easy box to design acoustically. Not too many hours work.
All the hard design work comes from making it integrate with existing product lines, in terms or rigging together with mains, either ground stacked or flown, for large scale systems. And also being useable for the small scale operator in standalone fashion.
There's also the major design issue of transport.
Correct truck pack size is paramount.
I remember when the Prosound forum and Tom Danley started the Labhorn project, the first clear criteria was that it be made to fit US semi-truck pack size...45"x45"x22.5" was the result.
Prosubs have to consider this for whatever their local trucking sizes...along with dollys, crates if needed, etc.
Bottom line i think, is given the ease and flexibility in the acoustic design of a BR, it allows the freedom to address the ergonomic build considerations.
Much more difficult to meet rigging and transport ergonomics with other types i think.
I have found this to work well in smaller tangband w5 1138 big mouth but not long offset driner entry point qw pipes. No sweep, slow and methodical finds and narrows in on things almost glazed over or ‘smoothed’ essentially. Im sure Brian probably used similar to find ‘dog food duct’ and its area of concern/resolve. (Great read btw).
Josh Ricci´s test recommend using the CEA-2010 short burst test.
This is the exact problem. The CEA-2010 short burst test allows for the Helmholtz resonance to gradually increase and build up before applying full power. A true transient will push the driver in a BR out of its linear travel and it will not have a chance to normalize around the zero crossing again until the main part of the energy from a drum strike has passed. This is quite evident just by watching a 218 BR box at high power at a live venue.
It is also quite evident why a horn, TH or high order QW BP will sound soo much better at transient content like drums, and the CEA-2010 short burst test will "hide" this problem with BR boxes.
I have found this to work well in smaller tangband w5 1138 big mouth but not long offset driner entry point qw pipes. No sweep, slow and methodical finds and narrows in on things almost glazed over or ‘smoothed’ essentially. Im sure Brian probably used similar to find ‘dog food duct’ and its area of concern/resolve. (Great read btw).
Paraflex 12 single, 160 liter: 38 hz
Using the sim As a ‘guide’ i test toned my way (sloppy hobby geek and not a professional) thorough things such as ‘efficiency’ impedance’ and ‘excursion’ and in a very tight’ boundary that might favor 48, 96, or 192” waves(?) (too many things are suspect and reoccurring) Theres a LOT of things to see on the cone of a paraflex that NOT on a ODTL. but in all of that , there is an observable interesting ‘issue’(even heavily stuffed versions as ‘transflex’ dont quite seem to handle) of transient activity on a cone thats sometimes looks like an epileptic flash in a person if ‘music’.
the things that cone has to deal and maybe helpful in the tornado of transients? are the reasons i hesitate to jump and widen as the CSa at throat and out area Chris refers to for this ? Or, It might WANT to consider a throat area of ‘surge tank’ because of what hes saying is the reason to consider and its possible repercussions? High pressure on both sides or low on both sides is steady state signals, nice and oscillating happy....controlled, but music is not necessarily so pressure -differential- steady state? And is the cone offset by pressure bias too!’?? BL as flux or as inductance issues changing? how quick and then at the distance from the VAS sensation(cone) is it felt? And then fought (Qes) in order to maintain a proper quality of whats being listened to? Its akward to think i could comment and be fair. slo mo camera is nit the answer unfirtunately , it has cycles too🙁
Double acoustic suspension / then ZERO (on one side or the other and twice if pushed?) thats a lot of heavy air to push and shove and react! Friction in surface area? I want small and long, not wide and longer. I think, but im Guessing, All in an instant ? Cone shaped like taco, drivers beware, of the rage inside the machine! Thats no jazz bar! Its helter skelter in there.
Sd 506.7
Qes .32, ((.64 )re 3.9, Le 4-4.2)
Vas22-23
Fs 37-38.4
Xmax15
Pmax 1000.
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