Controlled-pattern offset bipole revealed

[audiokinesis]

In the inaugural issue of the new online publication "HFi Zine", I have an article on the controlled-pattern offset bipole loudspeaker configuration. I use this configuration in several of my commercial designs, including one that received a Golden Ear award from The Absolute Sound in 2008. Near the end of the article is a list of suggestions for DIYers.

http://www.hifizine.com/2010/06/the-...e-loudspeaker/

[SunRa]

Thank you for the link! Much appreciated! I long sought to find more about your designs!

[Norris Wilson]

Thanks for the article, very informative.

I can't stop wondering how a sealed three-way design would work in an offset bipole configuation using the crossover between the midrange and midbass to help control some of the wrap around deficiencies.
My thought would be a three-way that is designed to maximize efficiency, quality of the midbass and midrange, while using four distributed sealed subwoofers from 60Hz or so to provide low end bass and control room nodes?

Any thoughts?

Thanks

Norris

[audiokinesis]

Norris, the wrap-around notch pretty much disappears in the reverberant energy, so I don't believe in trying to "fix" it by changing the speaker's frequency response. Sort of like I don't believe in baffle-step compensation in most cases (I don't use it in any of my monopolars), as it solves one problem but introduces another that I think is worse.

My understanding is that, in their first-generation bipolars, Mirage notched the rear-firing woofer's output at the wrap-around frequency. This avoided the cancellation notch, but introduced a dip in the power response. Mirage stopped doing that in their second-generation bipoles, and just relied on their wide, shallow enclosure geometry (which is what I do).

I think that Genesis takes a very interesting approach with their four-way Model 5 series bipolars: The wrap-around notch region is covered by a pair of midwoofers, and the rear-facing one is wired in reverse polarity. This way, ithe rear midwoofer's output is reinforcing rather than cancelling at normal listening positions at the wrap-around frequency, but then there is cancellation to the sides.

Definitive Technology has patented their approach, which is to use a single side-firing woofer and confine the bipolar arrays to frequencies above the wrap-around.

Now there's no reason one cannot do a three-way bipolar; my reason for going with a controlled-pattern two-way is that's what I know and do best.

[Norris Wilson]

Thanks Duke,

Just as I thought something as simple as adding a crossover in the right frequency range to control the wrap around difficiencies would be a fix, life gets complicated.

I guess simple is never truely simple. If it looks too got to be true, it is.

Norris

[otto88]

I just saw this. If i didn't have too may projects already, I'd definitely give this a try.

Superb article, thanks Duke

[badman]

Thinkin' about giving this a try myself. I'm assuming you balance the individual horn/midwoof sections just like you would in a 2 way, but without addressing baffle step (assuming you would have been)

[paulspencer]

A very interesting approach. When I came across this, an idea occured to me. Another thing to try would be to install the front firing speakers into a bass traps which acts like a soffit, flush mounted. Or simply flush mount. Now add a second version instead of the rear drivers, put them on the side wall pointing towards the listening position. Now delay this second "ambience speaker" digitally, rather than doing it via placement out from the walls. I may actually try this at some point, no idea how it would turn out, if it's a good idea or not.

[Saturnus]

Thanks for the article. I hope more people get interested in trying out bipolar designs due to their very real superiority over conventional monopoles and dipoles.

I think my next project will be to try a bipole Karlsson enclosure.

[badman]

Originally Posted by Saturnus

Thanks for the article. I hope more people get interested in trying out bipolar designs due to their very real superiority over conventional monopoles and dipoles.

I think my next project will be to try a bipole Karlsson enclosure.

In what way are they superior to dipoles with appropriate eq and headroom? The dipole pattern seems to distribute modal behavior pretty well, and can exhibit pretty uniform directivity to low frequencies, impossible with anything else except ginormous horns. The Bipoles will always be compromised in terms of power response by the bass peaks to the sides.