SLOB: Nelson Pass's Slot-Loaded Open Baffle system

[sfdoddsy]

Whilst the acronym has a certain appeal, I'm also looking for a way to reduce the height of the woofer section in my next OB project without losing output.

Has anyone tried, or does anyone have an opinion on, Nelson Pass's Slot-Loaded OB woofer system?

http://www.enjoythemusic.com/diy/0911/slot_loaded_open_baffle_speaker.htm

[Face]

Looks similar to a ripole in response, but easier to build and more difficult to place in a room.

[cjd]

I'll be loading the bottom end of my slowly happening dipole unevenly like he outlines, but it'll be a W baffle. I'm not sure how high in frequency something like this remains good sounding but it has me pondering alternatives where I am still undecided driver-wise (between 60hz and 250-400...)

[Paul W]

I'm contemplating a Z baffle with the bottom edges of the woofer and magnet on a single horizontal line, top edge of the woofer tilted back. Reduces overall height a few inches.

John K provided interesting comments regarding SLOB on DIYaudio.

[sfdoddsy]

I'm also intrigued by the potential for force cancellation. Any thoughts there?

[gainphile]

I think a vertically-stacked w-frame would yield the lowest woofer height.

The tradeoff is complexity of construction.

[sfdoddsy]

Thanks Andi. I'm not a big fan of the complexity of a W-Frame.

The height of the woofers doesn't have to be an absolute minimum for what I'm thinking, just lower than two woofers in an H or V frame.

Force cancellation is real plus so I can directly mount it to the mid section.

[gainphile]

Indeed it's really hard to make all pieces squared in W-Frame. Even harder than a simple box! This is because there are pieces in the middle which you can't simply 'route away'..

When I did mine (and this will be the last W-Frame I will build!), I can make 0.5mm precision cuts with circular saw and cutting jig. This was fine, but I reckon a 1mm 'miss' will ruin everything. It took me a week to build a pair.

But when all is done, it's quite amusing to watch furiously pumping woofers... yet no vibrations !!

H-frame gets my vote for simplicity and performance. Half-a day job and you are almost guaranteed to have a square (or square-looking) product

[Deward Hastings]

H-frame gets my vote for simplicity and performance.

Mine too . . . although the V-frame that SL introduces in the LX521 is if anything simpler, and lets the box be a little bit shorter, too. The force cancellation of the W-frame is nice, but the cavity resonances force the crossover down further than I like.

[gainphile]

I was worried about excessive cavity resonance. But that turned out not to be the case.

Here they are even at 120hz!

[Deward Hastings]

I was worried about excessive cavity resonance. But that turned out not to be the case.

It's there . . . but I agree that it's hard to get very exercised about it given the relatively low magnitude. I expect it would get lost in "room effects". It leaves me at a loss to understand why SL lowered the W/M crossover for ORION 3.4/4 . . . the disadvantages would seem to outweigh any benefit . . .

Have you taken similar measurements of a "H" frame (where the cavity resonance should be significantly higher in frequency, and even less an issue)?