8th order BP bandwidth

[Brian Steele]

I had an old Bose AM7 Series II 8th order BP bass module by me a few weeks ago, and I performed some FR measurements. I suspect that the FR is affected a bit by the age and condition of the bass drivers, but still, it looks like a pretty wide passband for a bandpass system. Has anyone here built an 8th order BP system, and if so, were you able to achieve a similar wide bandwidth?

Of course the wide bandwidth does not come without a penalty - GD for the module peaked at 23ms at around 53 Hz, but still...

 

[GM]

Yes, in the form of building a Karlson K15 [2+ octaves], though had no clue how it worked as the pictorial description at the time was nonsensical to me and wasn't till Freddy showed me many decades later PWK's response to him that it became obvious.

GM

 

[freddi]

not built one but interested - would you say that's a good two octaves ? my old series BP from years ago with 1.2 CF per chamber did pretty well and was used passively to augment some Control I mini. Outdoors and a meter or so away, the graph looked more :"sway backed" than this near port graph

GM - if front chamber depth of K15 were reduced , the how around 250 would probably look more like like
that of my K18. Karlson used a front deflecting shelf in K15 which helped but didn't put that feature into
any of his small "couplers"

here's a beat K15 with the 1954 40.5 sq.in. port outdoors vs a reflex the size of its back chamber - both ~
on cabinet center axis. K15 on sine loaded well to 37Hz (why? - its tuned more like 47)


I imagine PWK used a K33 for the graph of his K15. K33 is an anemic sounding
driver in K15 vs an Altec 421. K33 has a lot of xmax - not needed for K15

 

[Brian Steele]

That's a pretty impressive passband response, Freddi. Was that a Madisound driver? The model # seems familiar, and a 2.5 cu.ft. box for 10" driver that can do 30 Hz is pretty decent...

 

[DonVK]

Yes, but in fairness it was not the sturdiest design. It was only for fun at the time Dayton PC83-8 (3") test results

I was impressed at what I could get from a couple of small full ranges. It was lumpy, and very tricky to adjust tuning. I would build another if/when I get chance, only it would be a serious attempt.

 

[freddi]

yeah Brian - - a 10" DVC model 1052 DVC from Madisound

 

[Circlomanen]

An adventure with 8th order BP

I have built several 8th order bandpass boxes.

Here with both simulation and measurements.