It is more true to the facts to say with a big enough sealed box, the resonance will approach as low in frequency as in free air. That's an advantage not a disadvantage. Isn't that exactly what everybody wants?
"Aperiodic" was created as a phony marketing term to disguise a bass-reflex speaker model, not a tech term. It meant that the manufacturer had added damping to the port to reduce the impact of the Helmholtz box resonance which always is present. A BR can never be "without periodicity" as the word "aperiodic" implies because that's how BRs work... just reduced to a degree that buyers like.
B.
But if the response is then 20 dB down at that frequency what good does that do?
And a horn is really a variety of horn. Aperiodic is a very usful term. Indeed what one is doing is adding an R to the vent equation in the model. One of my gurus did some serious research into this, resonance was significantly damped, and further the 1st derivative of the FR curve was less.
Here is a measurement from an aperiodically damped midTL which clearly shows the reduction n resonance magnitude.
dave
I have received comments from other people this forum similar to that of Bentoronto, that is, that the 150-liter box is small for an 18-inch driver. I have even been suggested 500 liters for sealing (tremendously underdamped, Q below 0.5, if I remember correctly)!
I think you're losing your way here.
This driver is designed for BR. If we use it against the recommendation of the manufacturer, (sealed NA dixit) the majority thinks that with DSP, EQ and a lot of power there would be no impediment to reach the first octave, with those "details" they put the signature in the box the form for the supervisor .....
But a few have understood the economic / availability limitations of other more appropriate drivers here in my country.
Waveinform is one of them, to whom I am grateful because he mentioned the most important thing:
"Man has this and with that he has to achieve the best possible result"
That's "the attitude" in a Diy forum, pointing out mistakes is easy, providing solutions is much more complicated.
I leave the link in case Planet10 is interested in going inside, Bentoronto I think it does not need it, it has already contributed its opinions, if I had to summarize its position, I would say that for him, without REW and measurements, I am losing my time and my money, repeating the words of another people forum.
Like a few older ones like me here, or, when I was young I used to listen to The Beatles and every so often I do it again, "Let It Be", what a great theme!
Eminence Delta Pro 18 A in prism sealed 150 liters
(see the latest post)
Freddi has helped me a lot too, I'll test your capacitor's recommendation .
Sorry OP for this OT
I think you're losing your way here.
This driver is designed for BR. If we use it against the recommendation of the manufacturer, (sealed NA dixit) the majority thinks that with DSP, EQ and a lot of power there would be no impediment to reach the first octave, with those "details" they put the signature in the box the form for the supervisor .....
But a few have understood the economic / availability limitations of other more appropriate drivers here in my country.
Waveinform is one of them, to whom I am grateful because he mentioned the most important thing:
"Man has this and with that he has to achieve the best possible result"
That's "the attitude" in a Diy forum, pointing out mistakes is easy, providing solutions is much more complicated.
I leave the link in case Planet10 is interested in going inside, Bentoronto I think it does not need it, it has already contributed its opinions, if I had to summarize its position, I would say that for him, without REW and measurements, I am losing my time and my money, repeating the words of another people forum.
Like a few older ones like me here, or, when I was young I used to listen to The Beatles and every so often I do it again, "Let It Be", what a great theme!
Eminence Delta Pro 18 A in prism sealed 150 liters
(see the latest post)
Freddi has helped me a lot too, I'll test your capacitor's recommendation .
Sorry OP for this OT
It serves to raise 20 db with DSP or similar artifacts ..... there will always be time in case my construction fails.
Anyway, I will have the second octave that is currently not very present with my DTQWTII, also, do not you think that with these drivers of Troels only - without adding a subwoofer - and Inuke with DSP would have avoided all this effort? , well, let me tell you, I'm retired and I have some free time for fun)
We still don’t know what woofer the OP intends to use but academia’s Eminence is a pro woofer, because it is efficient it either needs a really big box or doesn’t go that low.
dave
dave
Here is the Eminence sealed sim. It doesn’t go really low… 30 Hz F10 in a 340 litre/Q=0.5 box. 31 Hz in 215 litres, Q=0.58, you get maybe 2 Hz more out of 500 litres (Q-0.45), but it is a bit droppier than the Q=0.5 box.
I like to design for Q = 0.58 (which when you add damping takes the Q down further) so 215 litre box. Anything larger, is to my mind, a waste of materials and space.
A big advantage is that a smaller box is easier to keep potential resonances above the passband.
But i would also use 2 woofers the next size smaller and mount push-push for automagix reactive force cancelation and a dramatically lower box load.
In 500 litres you could fit 2 DPro 18s, but if you want to go lower, different woofers.
dave
I like to design for Q = 0.58 (which when you add damping takes the Q down further) so 215 litre box. Anything larger, is to my mind, a waste of materials and space.
A big advantage is that a smaller box is easier to keep potential resonances above the passband.
But i would also use 2 woofers the next size smaller and mount push-push for automagix reactive force cancelation and a dramatically lower box load.
In 500 litres you could fit 2 DPro 18s, but if you want to go lower, different woofers.
dave
Attachments
In fact, the efficiency of the my speaker is 96 db / 1w / 1m, but note that between 20 and 40 hz, (the bandwidth that I look for, forget the rest, - I repeated this to the exhaustion -) falls approximately 12 db .
But that's just a speaker and no cabinet.
In my configuration they will be two speakers (sealed), but in a corner format, and there is also good room gain. In the link are the sims but I made an error to simulate with a watt, things change a lot when I apply 250 watts, - the rms power that I have - appears the power compression and the cone excursion is close to the limit Xlim .
This is similar to the story of the man who calls the doctor by phone, tells him that he feels bad, explains what he feels and asks him: Dr., what do I have?
"My impression is that you want to save the consultation, stop by my office, I'll check it and then I'll tell you with certainty" 😀
So you have to wait, the measurements are not everything, and the final result will be seen in the room with the cabinets running....🙂
http://www.eminence.com/pdf/Delta_Pro_18A.pdf
But that's just a speaker and no cabinet.
In my configuration they will be two speakers (sealed), but in a corner format, and there is also good room gain. In the link are the sims but I made an error to simulate with a watt, things change a lot when I apply 250 watts, - the rms power that I have - appears the power compression and the cone excursion is close to the limit Xlim .
This is similar to the story of the man who calls the doctor by phone, tells him that he feels bad, explains what he feels and asks him: Dr., what do I have?
"My impression is that you want to save the consultation, stop by my office, I'll check it and then I'll tell you with certainty" 😀
So you have to wait, the measurements are not everything, and the final result will be seen in the room with the cabinets running....🙂
http://www.eminence.com/pdf/Delta_Pro_18A.pdf
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