Is it possible to cover the whole spectrum, high SPL, low distortion with a 2-way?

Do you know any real incarnations of the parabolic horn type?

Only as individual segments in a bass horn, where the segments have two parallel straight sides and two sloping straight sides, resulting in a rectangular cross-section with the cross-sectional area varying linearly with axial length. Parabolic horns are however often used in reverse in transmission line loudspeaker systems, because they are relatively easy to construct.

for sound it's different because of the different velocity. It's a slow propagation phenomenon, different from electromagnetic waves.

That doesn't stop parabolic reflectors from being used with sound though :).
 

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I haven't tackled anything regarding certain components of the enclosure yet, and would like opinions and on best practices, if you would so kindly take the time to reply. <snip>
Opinions vary regarding cab materials, but I'd prefer baltic ply. It's more difficult to carpenter, especially if you want a rounded baffle. Rock wool could be used for dampening. Instead of stuffing the whole cab, you might experiment with (extra) thick layers in a few places. Wool/cotton (PET) felt works too and is cheap, as long as you don't buy it from audio shops.

tessuto-riciclato-1764x700.jpg
 
so now that you know, what do you think?
Mains with 15m, subs running 18H+
15M 17x23x20 3.4cuft sealed
18H+ 31x23x20 6.5cuft ported

Unless I can find a reason why sealed would work for the 18h+

Camplo, I have 4 pcs PB 18+ from AE as separate sealed subs / woofers in my room, mid bass are AE's TD12M for front speakers. PB 18+ is AE's version of TD18H+ with dust cap instead of the usual phase plug. (According John at AE, the dust cap gives a resonance at about 500 Hz, otherwise the same element.)

If you like I can run some measurements in REW with the UMIK1 microphone. One thing which I think hasn't been mentioned is what kind of room the speakers are placed in. Mine is concrete all around, so a lot of the bass is contained within compared to a room with light weight studwalls + drywall. It is fairly long 7,86 m / 25,8 feet so lowest length mode is theoretically at 21,8 Hz. (If I recall correctly the sealed box volume / element is 174 L / 6,1 ft³, I cannot remember calculated box resonance now but I calculated ( =guessed ) I should get some respectable "free" pressure mode gain below 21,8 Hz as the room is a concrete bunker. Hopefully at similar rate as sealed boxes fall off.)
 
Skill Set? Really?

Come on, you should have enjoyed the time and not think of this nonsense again :)

David - noticed ;)

My enjoyment, time management and math skills are all if fine shape.

All parabola in the limit have two solutions that yield parallel lines with slopes of zero (for x-axis orientation). That fact yields a cylinder not a cone in the case of the surfaces of revolution addressed here. The criteria you guys are applying are simply not relevant here.
By inspection of the example I gave, it should be obvious. Plug and chug some numbers to see what is happening. There is absolutely no requirement that a parabolic horn have a limit in which Y < oo, for its sides to be approaching that of a cylinder. This is precisely because it does not have an asymptotic surface in the limit. Note that in both the parabolic and hyperbolic cases the magnitude of Y is unlimited. What becomes limited is slope, and radius of curvature. So, the limit on y criteria, is a bogus argument against the cylindrical limit claim.

WHG
 
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My enjoyment, time management and math skills are all if fine shape.

All parabola in the limit have two solutions that yield parallel lines with slopes of zero (for x-axis orientation). That fact yields a cylinder not a cone in the case of the surfaces of revolution addressed here. The criteria you guys are applying are simply not relevant here.
By inspection of the example I gave, it should be obvious. Plug and chug some numbers to see what is happening. There is absolutely no requirement that a parabolic horn have a limit in which Y < oo, for its sides to be approaching that of a cylinder. This is precisely because it does not have an asymptotic surface in the limit. Note that in both the parabolic and hyperbolic cases the magnitude of Y is unlimited. What becomes limited is slope, and curvature. So, the limit on y criteria, is a bogus argument against the cylindrical limit claim.

WHG

"radius of curvature" corrected to read curvature. The former is unbounded.
WHG
 
Camplo, I have 4 pcs PB 18+ from AE as separate sealed subs / woofers in my room, mid bass are AE's TD12M for front speakers. PB 18+ is AE's version of TD18H+ with dust cap instead of the usual phase plug. (According John at AE, the dust cap gives a resonance at about 500 Hz, otherwise the same element.)

If you like I can run some measurements in REW with the UMIK1 microphone. One thing which I think hasn't been mentioned is what kind of room the speakers are placed in. Mine is concrete all around, so a lot of the bass is contained within compared to a room with light weight studwalls + drywall. It is fairly long 7,86 m / 25,8 feet so lowest length mode is theoretically at 21,8 Hz. (If I recall correctly the sealed box volume / element is 174 L / 6,1 ft³, I cannot remember calculated box resonance now but I calculated ( =guessed ) I should get some respectable "free" pressure mode gain below 21,8 Hz as the room is a concrete bunker. Hopefully at similar rate as sealed boxes fall off.)

lets see some charts! I've decided that the general concensus that the 18H+ is not sub woofer, but rather a woofer, to be true. To reach 115db at 30hz requires 1000watts for the 18H+ plus and 500watts for the 15H. My amps are 1000watts rms at 8ohms so its not a matter of limitations but what am I really doing here? The more watts the more power compression is my thought not too mention the voice coils are 500watts rms.
 
WHG
Double the length, the cross sectional area will also double, and it goes exactly like that for infinity. Does it really resemble a cylinder to you?

All parabola in the limit have two solutions that yield parallel lines with slopes of zero (for x-axis orientation).
I beg my pardon, but they don't, really.

... Note that in both the parabolic and hyperbolic cases the magnitude of Y is unlimited. What becomes limited is slope, and radius of curvature. So, the limit on y criteria, is a bogus argument against the cylindrical limit claim.
To repeat, the difference between hyperbola and parabola is that the hyperbola actualy approches a line. Parabola does not.

Mathematicaly speaking, for a hyperbola the limit of sqrt(x^2 + const) - x equals zero for x->∞. There is no such thing for a parabola, i.e. for (sqrt(x) - const) or (sqrt(x) - x). But it seems I'm out of arguments at this point.
 
@whg and @mabat probably talk of different things?

If we look at the situation of water in a rotating glass then we have the boundary potential of a cylinder like this:

M-60 | Zentripetalkraft: Rotiere... | Vorlesungssammlung Physik

We can see that the water will run over out of the glass at a certain rotational speed and a paraboloid is formed. So, it does not approach a cylinder. But if the potential is infinite (a glass with infinite height, the whole fluid approaches a cylinder for infinite rotational speed. But then we do not have a "simple" paraboloid equation anymore.

The best thing would be that you agree to echother of having talked about different things :D
 
That is the definition of "approaching" to something, it must converge in total. The limit of the rate of change itself is not enough.

As in the attached simple example, which plots the expression y = x / (1 + x). The value of y approaches the asymptotic limit of 1 as x is increased, and y can never exceed 1.

A parabolic curve does not exhibit this limiting behaviour.
 

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Cheers!

Actualy, no. For a cone the area grows much faster, with the square of distance. This is really the parabolic expansion :)

You guys are addressing the obvious increase in y but do not want to address the unintuitive fact that slope and curvature are approaching zero in the limit for a paraboloid. Anyway, we are leaving the casino now, $13,800 richer than when we came. So despite the unpleasant experience I have had here, I can say goodbye with a smile on my face, anyway. WHG :)
 
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