Do a 6th order filter ...
Quote:
Originally Posted by
Lee in Montreal
BTW The intent of the project is to be flat fro 30Hz to 800Hz.
... and end up at 22 Hz. You need an electronic xover which can give You the missing two orders: 4 orders come from the box, and two from electronic filtering.
See the Thiele papers.
Ruediger
It's easier than You may think.
Quote:
Originally Posted by
Lee in Montreal
Hi Ruediger. You lost me here ;-) How will the 12db electronic crossover affect the lower end? Do you mean a small "bump" down there?
General Audio Discussions -> Technical References Thread -> Thiele Papers Part I -> Page 6 resp. 186: "Sixth-Order Butterworth Response". See also Figure 6 on page 8 resp. 188.
A filter of any order can be achieved by chaining filters of order one and two. Four orders will be supplied by the box, and two by the electronics.
You even have three choices, which two of the six orders You handle by electronics, and which four by the box. Not all of these choices will always lead to a good design.
There is a good design in the tables of that paper.
May I say "EV DX-38" again?
Ruediger
You should read a text read about well-defined filters ...
Quote:
Originally Posted by
Robh3606
That's the point I was making. It took you what 5 minutes if that to find the answer you were looking for.
Rob:)
... such as Bessel, Butterworth, Cauer, Chebyshew and others.
These filters do have well defined properties and thus a predictable behaviour.
If You build *any* filter it will have *any* properties and *any* behaviour.
It is the merit of Mr. Thiele that he has made the design process rational. And You guys go back to the days when the punchcards were made from wood :)
Once You are used to the table in the Thiele paper it will take You less than a minute to understand what is possible with a certain drver, and what not.
Ruediger
It does not have any influences of the diver(in the box) impedance.
grumpy I'm not sure what this has to do with a 2245 or about
a suitable cabinet... nor the purpose of the question
that appears to be more of a statement. Perhaps start
a new, direct thread.
I was just reading the last entry about "diver (in the box) impedance"
and that horn/cone imped. diff. thing ...popped .up in my head...?!!
What if I increased cabinet size to 12cft?
Quote:
Originally Posted by
Ian Mackenzie
What if I increased cabinet size to 12cft?
If You pick a larger cabinet size Vb then the following formulas apply.
f3 = fs * sqrt( Vas/Vb)
fb = fs (Vas/Vb)**0.32
You will have a "ripple" (deviation from flat response):
R = 20 * log10(2.6 * Qts * (Vas/Vb)**0.35)
There is a missunderstanding about fb and the box resonant frequency, fb *IS* the box resonant frequency, this is when the system of air mass in the ports together with the air "spring" in the box does resonate.
If You build a passive xover then the Qt of Your speaker will change because of the DC resistance of the series coil in the xover. This has been explained several times here, and it is explained in the Thiele paper. See the technical references thread.
Ruediger
There are more alignments than just one...
Quote:
Originally Posted by
kartsmart
I see going larger than 10 cu ft but what happens when going smaller to the 8 cu ft box ? like what jbl has sold. what would be the trade off for 30 HZ to 340 HZ
... see the Thiele paper. Many well-defined filters are possible, Butterworth of order 4 is just one possible choice, and even that only when the driver fits.
You may as well apply the formula given in my last response. The response will have a positive ripple, the response will be peaked somewhat. The corner frequency will be higher. In too small a box a smaller driver may be better than a larger one.
Ruediger