Open backed boxes ? Anyone ?

[REC1]

Yep!

It would be a simple build or at least no more complicated than a normal BVR with the advantage of a singular mouth that would be horn(a bit)/waveguide loaded. All of the produced energy would eminate from a singular point or area.(the mouth)

The additional internal deflector would distribute the frequencies at a given point which would help eliminate the beaming at HF.
Figure if the second deflector(internal in the mouth) was at 45 degree angles and around 2" width the "spreading" of the wave front would occur at around 6Khz and >. With the energies being distributed over a greater area the rising response would be lowered and possibly not need BSC(filter) on low Qts drivers such as the 206.

ron

[GM]

Originally posted by MJK

Wings that are folded back will impact the sound of the OB system due to the geometry, however I do not believe they impact the sound due to resonances between the panels.

Yeah, as long as there's enough of an angle for the slap echo to decay off the backside (> 1 in 12 slope), then the only loss is the one going from 2pi to 4 pi space, but then there's two 'mouth' end corrections that will tend to offset it somewhat, so for a typical HIFI app you have to fold them back to a steep angle before the bass goes away, at least that's my dim memory when I fooled with them, so if I were to make them again it would be a driver width baffle with the biggest hinged wings the space allowed.

Ultimately, while we found them wanting without a boxed woofer system for the < ~500 Hz BW, backed up to near a wall with some HF reflections damping and the wings folded forward as required worked best overall in the few medium size apartment living rooms we tried them in.

As always though, YMMV.

GM

[Godzilla]

That horizontal half chang looks very interesting. I wonder how the sound will be different compared to a forward facing driver? I also wonder if there will be an increase in efficiency? But i do worry there may be a boxy coloration as the sound emanates from the top.

[REC1]

But i do worry there may be a boxy coloration as the sound emanates from the top.


Nope. Its a very short expansion and more of a waveguide than a horn. There will be less side wall reflections, If a helper tweet is needed then mount on the vertical short section at the rear of the enclosure( and do away with the second deflector in the mouth). I guess time wise this will allow for some of the 90 degree phase shift, but i havent crunched the numbers.

ron

Just thinking aloud here, this would make a good 2 way with a 3" driver in the tweet position. BVR/WB.

[GM]

It's acting as a 6 th order mini horn (BP) with a high cut-off, so can be modeled in Hornresp for the basic system, though its predicted combined response would be too far off to be of much (any?) use AFAIK.

My SWAG is that as is, it would boost the BW that already needs attenuation, though I imagine that once you get the box design dialed in for more mid-bass boost it would damp it down somewhat along with its HF response, similar to a simple two chamber Karlson.

GM

[Scottmoose]

Be interesting to find out... I might stick a couple of test boxes together.

[planet10]

Originally posted by nosmok
Hartley "boffle" concept here

I have an article on it, haven't had a chance to turn it into a pdf yet...

dave

[planet10]

Originally posted by REC1
Dave, i havent forgotten about you.

Me? you been poking in my brain

I was thinking of you and the black 166s today.

dave