The Hurricanes- A multi-woofer open baffle 3-way tower

[jhollander]

There's a slot resonance that can be modeled in horn response. The idea is to move the resonance peak below the pass band.

[DaveFred]

How did you calculate the opening size for woofer slots?

Are the bottom and top woofers "unbalanced" compared to the other six with regards to loading due to their different chamber sizes?

[shrub0]

Are you able to generate any distortion tests? With so many woofers in push pull I imagine it to be low.

[DanP]

Re: The Hurricanes- A multi-woofer open baffle 3-way tower

I haven't generated any spatially averaged curves yet, but I was so blown away by the smoothness of the initial ungated measurement, that I immediately began to move the mic and speaker about the room to see if it was a fluke. It wasn't. So you're right - an average monopole measurement in my room is worthless below 300Hz with +/- 20dB swings at random intervals depending on exact placement of mic and speaker. The Hurricanes exhibit a very flat measured response curve with +/- 3 dB swings. These deviations also move as the mic and speaker position move, but it's very obvious where the actual response of the speaker lies when the position dependent anomalies are so small.

Dan

[Pallas]

The Hurricanes- A multi-woofer open baffle 3-way tower

Very innovative riff on OB!

Have you taken any spatially averaged measurements at your listening position? I'm curious to see the upper bass performance in room. I would not be surprised if the native response smoothness below 300 Hz or so is substantially better than monopoles in the same placement.

[DanP]

Re: The Hurricanes- A multi-woofer open baffle 3-way tower

Very nice- now you're going to have to rotate all the woofers every year to prevent cone sag ;)

Slot-loading can be very helpful- I downfire the slots in my sub (similar push-pull mounting, 2 pairs) and the drivers go from inherent 25hz and 0.55 Qts to 20Hz and 0.8 Qtc- similar proportional shifts to your own. Very handy!

Have you found their output limits yet? With the octet of the woofers and a pretty decent front-to-rear distance I'd expect these to have a pretty capable bass with the tweeter being the more likely limiter on most content.

I have not tested the limits yet. I've only had a 75 w/ch amp hooked up to them, which got them to a decent listening level and on reasonably bass heavy tracks, the woofers were barely moving. I'll get a good listening session soon with my 300 w/ch QSC GX3 and see what they can do. I think you're right though that the woofers won't be the limiting factor.

Dan

[Wolf]

Re: The Hurricanes- A multi-woofer open baffle 3-way tower

Thanks for the responses Wolf and Dan. Really wish I was going to the DIY event so I could hear these.

Well- you have about 3.5 months to arrange something....
Wolf

[badman]

Re: The Hurricanes- A multi-woofer open baffle 3-way tower

Very nice- now you're going to have to rotate all the woofers every year to prevent cone sag ;)

Slot-loading can be very helpful- I downfire the slots in my sub (similar push-pull mounting, 2 pairs) and the drivers go from inherent 25hz and 0.55 Qts to 20Hz and 0.8 Qtc- similar proportional shifts to your own. Very handy!

Have you found their output limits yet? With the octet of the woofers and a pretty decent front-to-rear distance I'd expect these to have a pretty capable bass with the tweeter being the more likely limiter on most content.

[philthien]

Re: The Hurricanes- A multi-woofer open baffle 3-way tower

Thanks for the responses Wolf and Dan. Really wish I was going to the DIY event so I could hear these.

[DanP]

Re: The Hurricanes- A multi-woofer open baffle 3-way tower

Very impressive design work.

Where does the sensitivity end-up for eight woofers running OB? Is enough output lost to cancellation that your mid and tweeter don't have to be amazingly sensitive?

Wolf is right, but the 8SW-4 is already a few dB more efficient than the DA175, so my plan was to pick a reasonable F3 for the woofers and tilt the response down from there to match the DA175. This assumed my measurement would look like a ramp starting "very low" at 20Hz and rising to "very high" around the dipole peak with not much of a plateau in between. When I took the in-room measurements of the woofers though, my plan went out the window. Remarkably, the unfiltered, ungated 8 woofer measurement @ 1m on the tweeter axis was +/- 3dB from 40Hz to 300Hz with a 10dB peak at 400Hz before rolling off. The level of this nice 3 octave plateau was serendipitously similar to the DA175 in-room response level.

I was shocked and I'm still not sure of all the variables that contributed to this happenstance. As I do more open baffle projects and observe the similarities and differences in the measurements, I'm sure it will become more clear. I'm assuming that room gain (perhaps a more stable contributor with the open baffle format?) and the high Q bump flattened the response out down low, but just how flat it was is still impressing me. I'm not ashamed to say I think there was a fair amount of luck in that aspect of the design.

Dan

[JasonP]

Re: The Hurricanes- A multi-woofer open baffle 3-way tower

These look terrific, and the write-up in the project gallery is well done. Can't wait to hear them at InDIY.

[Wolf]

Re: The Hurricanes- A multi-woofer open baffle 3-way tower

My guess is that since 4 are in series, and then the quads in parallel, he only gained +6dB. This is good for BSC.

Later,
Wolf

[philthien]

Re: The Hurricanes- A multi-woofer open baffle 3-way tower

Very impressive design work.

Where does the sensitivity end-up for eight woofers running OB? Is enough output lost to cancellation that your mid and tweeter don't have to be amazingly sensitive?

[Mike220]

Re: The Hurricanes- A multi-woofer open baffle 3-way tower

Very cool design. That's an awesome way to stuff as many woofers as possible into the smallest space possible. I wish it had less woofers.....said no one ever.

[greywarden]

Re: The Hurricanes- A multi-woofer open baffle 3-way tower

That's awesome, I have a handful of those 8s, too and I've considered something like that with them before.