6th order bandpass question

[tinitus]

Hi

I am wondering why low end rolloff on a 6th order bandpass is always rated as equal to driver Fs, or close to, which would make it very attractive with use of pro woofers

Is that fore real ?

To me it doesnt look much different from ordinary BR, but it obviously is

Does anyone have any explanation to this ?

 

[GM]

Oh really?! News to me.

GM

 

[tinitus]

Thanks GM, I was hoping you would turn up

As I expected, its an error with that low rolloff

May be that its the frequency where its 12db down, or something like that
I dont know the standards fore bandpass, apart from having steep rolloff

Nope, it says 3db down at 32hz
driver Fs of 30hz, 0.25Qts, Vas 300 (imaginary woofer)

Rear chamber 174liter, two ports tuned to 30hz, each with ø100mm x 260mm long

Front chamber 60liter, one port tuned to 60hz, ø100mm x 170mm long

 

[tinitus]

Oh really?! News to me.

GM

Ahh, yes I see now...its just the tuning...stupid me

 

[tinitus]

I may be naughty, but in my files I call this a "Tapped Ported Bandpass"

Question is whether there could be phasing issues between the ports ?

 

[GM]

Agreed.

There will be if not properly tuned, same as a TP, TH.

GM

 

[tinitus]

Ok, thanks

1. Will it be better this way ?

2. Or maybe bottom port should face downwards ?

3. Or will port phasing always be a risk/issue ?

4. Any suggestions what to do best ?

 

[GM]

Don't know, they all seem same-same to me, so better to use an 8th order Karlson IMO if not a TP or TH or even a B@$3 WC if a vented rear chamber is used, with bulk Vs output for a given BW being the final arbiter.

GM

 

[tinitus]

I know what a TH means

But the other WC, TP, BW or 8th order Carlson...sorry, dont know what that means

 

[GM]

Bose Wave Cannon, tapped pipe, band-width, Karlson K-15 box alignment, an 8th order band-pass (four tuned resonant cavities).

GM

 

[tinitus]

Bose wave cannon...that would be like a sonotube, I guess

Karlson K-15, built one in my youth and thought it was only fore midbass/low midrange

8th order bandpass looks very tricky

Im not building anything right now, and have a classic 3way "monitor" project fore my bookshelf in the works

And I have a nice 200liter closed matrix box, which I want to put in use, somehow...preferably combined with a Beyma ribbon

I have also emailed Ecologic about their new Afficionado 8", but no reply

So, I really dont know in which direction I am heading



Thanks fore nice clarification

 

[Collo]

Those box specs are close to a 6th-order bandpass sub I've almost finished building. It has.....

A 60 litre chamber with a single 6-inch port tuned to 53hz.
A 200 litre chamber with a pair of 6-inch ports tuned to 25hz
Driver is a Mach5 Audio IXL18

It will be interesting to see how it measures up.

 

[HK26147]

Speaker Builder 6/88 had a detailed background theory on 4th order.
It showed graphically the effects of system tuning. Like any other bandpass filter you can tune for a sharp narrow peak or a flatter wider band.
Alignment Tables included in that article were used to build 4th order subs.
Shortly after SB had articles on 6th order designs, until they were told to cease from B@$3.
( This was prior to the development of PC programs that include bandpass modeling. )

Collo: I built 4th before but not any higher order and be curious as to your outcome.
I have some JBL drivers that I have considered placing in a bandpass, tuned for pro sound use.

 

[freddi]

the Karlson's front shelf deflects a sip in the 250Hz region and somewhat segregates HF from reaching the upper part of the coupler (that first reflection dip could be mitigated with a more shallow baffle angle)- the rear shelf works as lowpass to clean up the port's output and can subjectively do some tuning on transients - - - I"m not sure about the "TH" BP arrangement sketch having much TH effect - looks good - can it be modeled easily?

here's a little BP6B (series) from maybe 12 years ago - I'm not sure if its foam is still intact - - series BP can filter the rear port's noises - - I don't have much experience or knowledge in speakers in general.

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