Experience on 8th orders?

[adam6604]

But people post on forums to get feedback, so when someone answers more then 5 threads a day it's spam?:s I thought that's what forums were for! Haha

[meade916]

But people post on forums to get feedback, so when someone answers more then 5 threads a day it's spam?:s I thought that's what forums were for! Haha

one liner's and basic gibberish to get your post count up is not feedback. We determine what is spam bro, not you. Thanks. Cheers.

[adam6604]

Haha yeah wasn't trying to start anything but personally haven't seen anything wrong with supercharged's posts so thought I'd throw my input out there! Haha sorry meade

[Emmet]

Just back to the 8th orders a sec,

whats the advantages or disadvantages of 8th orders compared to other enclosures?

Hadnt even heard of an 8th order before now

[C-Fizzy]

this look's like a complicated version of ported box( L shape)

uh, an 8th order is just a tad more complicated than that.

[eltortuga94]

So back on topic lol. Does anybody have any experience with them or know any advantages?

[Quiet]

If you've ever seen a Bose Acoustimass Sat/Sub system, the subs they use are one or two 5.25" woofers in an 8th order. Which is like a dual tuned 6th order both firing into a common chamber which is then ported to the outside of the box. Anyway, I came across this document and it has the math on how to calculate an 8th order out. It's the only formula I've ever seen on an 8th order...

The Bose Acoustimass (8^th order Bandpass)

Driver placed between two chambers (#1 and #2), which both vent into a

third (#3) chamber

which vents to "outside".

Design Procedure

1. Pick your favorite 4th order low pass filter function of the form

nfc/(dfc0 + dfc1 s + dfc2 s^2 + dfc3 s^3 + s^4)

for a Butterworth nfc =1, dfc0 = 1, dfc1 = dfc3 = 2.61, dfc2 = 3.41

2. The eighth order response is centered at the driver resonant

frequency

3. The bandwidth is the driver resonant frequency over the product of

dfc3 and the driver

total Q, (Qt)

4. Let alpha1 times the driver resonant frequency be the frequency you

tune chamber 1 and

its vent to.

Let alpha2 times the driver resonant frequency be the frequency

you tune chamber 2

and its vent to.

The third chamber and its vent is tuned to the driver resonant

frequency.

Let beta 2 times Vas of the driver be the volume of chamber #1

Let beta 1 times Vas of the driver be the volume of chamber #2

Let beta 3 times Vas of the driver be the volume of chamber #3

5. Now

alpha1 = 1/alpha2

beta1 = -1/(alpha2^2 * dfc3^3 * Qt^2) *

{-alpha2^2*beta3*dfc1+alpha2^2*beta2*dfc3^3*Qt^2+beta3*dfc3^3*Qt^2

-2*alpha2^2*beta3*dfc3^3*Qt^2+alpha2^4*beta3*dfc3^3*Qt^2}

beta3 = -

(1+alpha2^2)*beta2*dfc3^3*Qt^2/{-(alpha2^2)*dfc1+dfc3^3*Qt^2 -

2*alpha2^2*dfc3^3*Qt^2 + alpha2^4*dfc3^3*Qt^2}

beta2 = (1+alpha2^2)*dfc3^3*Qt^2/{-dfc1+dfc2*dfc3}

alpha2 = 1/Sqrt(2) * Sqrt( {xterm + Sqrt(xterm^2 - 4

dfc3^6*Qt^4*yterm^2)} /

{dfc3^3*Qt^2*yterm} )

where

yterm = dfc1 - dfc2*dfc3

and

xterm = dfc1^2 - dfc1*dfc2*dfc3 + dfc0*dfc3^2 + 2*dfc1*dfc3^3*Qt^2

-

2*dfc2*dfc3^4*Qt^2

Calculate xterm and yterm first and work up the list.

*********************************************

Note: This is not part of the original e-mail Dr Smith sent me but I

thought you would like to know

for 1 dB Chebychev (spelling?) nfc=0.246 dfc0=0.276 dfc1=0.743 dfc2=1.454

dfc3=0.953

for 0.1 dB Chebychev nfc=1.783 dfc0=1.804 dfc1=2.627 dfc2=2.026 dfc3=0.829

for Bessel nfc=105 dfc0=105 dfc1=105 dfc2=45 dfc3=10

That makes a total of four alignments as given to me by Mr. Smith

*********************************************

F3lower and F3upper are obtained from

BW=Fs/(dfc3*Qt)

F3lower=sqrt(Fs^2+(BW/2)^2)-(BW/2)

F3upper=sqrt(Fs^2+(BW/2)^2)+(BW/2)

Now there shouldn't be any problems with calculations, hopefully.

Oscar

EDIT: I found some xls spreadsheets with the calculations built in. If you're interested, PM me and I'll email them to you.

[D-train-13k]

^ oh yeah i get it now!

i would venture to say that their complexity will help get more efficiency.

i mean i have no experience with them but 4th orders are built to gain more efficient output.

4th, 6th and 8th orders may be huge but if they were pointless to make nobody would try to figure it out.

i have read that 6th and 8th orders are stupid difficult but are really nasty setups when done correctly

[Quiet]

^ oh yeah i get it now!

i would venture to say that their complexity will help get more efficiency.

i mean i have no experience with them but 4th orders are built to gain more efficient output.

4th, 6th and 8th orders may be huge but if they were pointless to make nobody would try to figure it out.

i have read that 6th and 8th orders are stupid difficult but are really nasty setups when done correctly

The higher the order you go, the more accurate your math and measurements better be.

[fritosaregood]

^ oh yeah i get it now!

i would venture to say that their complexity will help get more efficiency.

i mean i have no experience with them but 4th orders are built to gain more efficient output.

4th, 6th and 8th orders may be huge but if they were pointless to make nobody would try to figure it out.

i have read that 6th and 8th orders are stupid difficult but are really nasty setups when done correctly

The higher the order you go, the more accurate your math and measurements better be.

and the more group delay. I think thats what its called