I'm considering building this offset TL, which is slightly big for the 12" driver I'm planning to use with it (an Eminence Kappalite 12" 4 ohm driver). The predicted output looks like it's going to be better than a TL that I built using the same driver, for a slightly larger cabinet. 120dB all the way down to 40 Hz, with 40V input, and not exceeding Xmax. I want to test a little "theory" of mine - that ensuring that the vent is the same or larger CSA than the driver's Sd produces audibly better results than a simple vented box where the vent's CSA is significantly less than Sd.
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Looks good, should be less noise and compresion at full output compared the BR, box size is not massive.
I was going to say. Brian, it is big, but big, big? A fraction of the size of the first TLs we built in the mid70s. 40 Hz is not that low.
dave
Maybe for a pro audio driver, but not low. An A10p In FHXL reaches lower.
You’ll need a subwoofer below those. A big, big TL?
dave
You’ll need a subwoofer below those. A big, big TL?
dave
Not to open a can of worms but IMHO The general consensus is divided in 2 categories , PA cabinets and HT cabinets, Iron law included, as I learned over here you do not really need below 40Hz response for PA duties , for HT you need extension to at least 20hz and some like to go as low as 15 or even 10, anyway I am not reinventing the wheel here.
You are proving a point with your port design and it is matter of see of it performs in real life on a working prototype.
And btw that 12 driver hitting 40 cleanly is impressive.
love your design Brian
Hope I can make one soon.
You are proving a point with your port design and it is matter of see of it performs in real life on a working prototype.
And btw that 12 driver hitting 40 cleanly is impressive.
love your design Brian
Hope I can make one soon.
It's a bit of a balancing act. Pro audio drivers tend to have an Xmax that's lower than drivers designed for real subwoofer duty. Put them in a box that's tuned too low, and you're going to run into excursion problems in the passband when the system is driven at higher voltage levels and overall output will be reduced. Put them in a box that's tuned to high and you reduce output at low frequencies and you narrow the usable bandwidth of the system.
In this particular case, the Kappalite's Xmax is rated at 9.1 mm, and its RMS power handling is 450W. Eminence's largest recommended box size for it is around 90 liters tuned to 41 Hz, with power limited to 300W (likely due to what I mentioned above). I'm going even bigger than that, primarily to get a bit of extra output at 40 Hz. Hornresp does suggest that my design is going to stay within Xmax with a 40V signal however. Given it's a 4 0hm driver, that suggests RMS power limit of 400W.
In this particular case, the Kappalite's Xmax is rated at 9.1 mm, and its RMS power handling is 450W. Eminence's largest recommended box size for it is around 90 liters tuned to 41 Hz, with power limited to 300W (likely due to what I mentioned above). I'm going even bigger than that, primarily to get a bit of extra output at 40 Hz. Hornresp does suggest that my design is going to stay within Xmax with a 40V signal however. Given it's a 4 0hm driver, that suggests RMS power limit of 400W.
What’s the connection between Sd and the CSA? I thought sizing up the qw pipe was to dampen/tame the Qes and keep Vas satisfied? NEver notice Sd being related in anyway with respect to this (but certainly don’t want high ‘port’ velocity). This foam sure seems to be the bees kneez ?? Swapping between dayton umax 18 and b/c 18ds115 here…(ignore output level)
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Well Sd is pretty much irelevant in a TL. So any relation with CSA is non-existent.
dave
That was my assumption (assuming damped to not have the peaks/ringing at the resonant areas of bandwidth. (1,3 or 5 x the 1/4 wave fundametal as Brian and I seem to always use (~0.349x ‘pipe’ length as driver entry) )
But in a subwoofer this is often a compromise in output (?). Stuffing away those peaks in an ‘ oversized TL‘ looses output if not careful/strategic and yet if not used to flatten the response a one or two note wonder subwoofer exists and isnt any fun to listen to either.
Brian,
Let us know when you finish your calculations as I want to build one of those in 2023
I like the corkscrew like folding.
Wonder how it pans out as a bunch of pseudo-series resonators or just blends into the bandwidth undisturbed/ unoticed.
Wonder how it pans out as a bunch of pseudo-series resonators or just blends into the bandwidth undisturbed/ unoticed.
ok so now that the SKAR DDX12 D2 is very popular as 12 driver i patched in on hornresp to see how it behave with Brian design, and i think is not not good
what you guys think ?
what you guys think ?
Which at the frequencies involved not even seen. So it has no impact beyond the extra little LP filters that the extra volume at each corner make.
dave
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That driver does not have the right efficiency for this type of alignment, hence the peak around the resonance frequency and the droop in the passband.
Now, if you put TWO of them in that box and wire them in parallel, the results may look a bit better. But there will still be a bit of a peak at 40 Hz and a larger response discontinuity at around 120 Hz because the effective center of the drivers would have shifted away from the optimum position in the TL to null out the 3rd harmonic.
Hey Brian,
i do not care above 100HZ or even 80Hz as it will be filtered out with DSP
the tops take care of any above thath
i do not want to hijack this thread but just as a side note
i saw that Skar 12 driver on the below design so i thought i can use just one on your enclosure
but looks like is a no go 🙁
i do not care above 100HZ or even 80Hz as it will be filtered out with DSP
the tops take care of any above thath
i do not want to hijack this thread but just as a side note
i saw that Skar 12 driver on the below design so i thought i can use just one on your enclosure
but looks like is a no go 🙁
This matters if you listen side by side undamped and observed. To what extent is up to the listener/observer but it’s very interesting when you’re not merely acknowledging only the 1/4 harmonic in these. Apples to apples is kinda tricky as driver/vent position consistency is difficult as well ….(you know all this, but it’s these details that matter ultimately ). Folded on the 3 x 1/4 harmonic parts or ignoring it and just folding at random)
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Try Brian’s design sized for the ddx12. I think you might enjoy the sound more than the high order approach’s akward , further misaligned resonators (?) nobody(Robert Moon) seems to wanna build things to hear this and compare or hear the issues in a boundary condition. They just wanna sim And draw pics all day and confuse us all😝
that paraflex box isnt aligned to an odd harmoinc and has a far greater discontinuity/pressure phase quirk then the OD MLTL Brian presented has in 3 simple folds (or the corkscrew mayve) it seems. Sim this to observe the discontinuity potential . it is quite simple
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