Horn Lens for BMS 4594HE

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NiToNi

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Joined 2004
tommus said:
take a look at bwaslo's clever design for his "small syns." he places the woofers behind bandpass slots at the bottom edge of the horn. the horn mouth overlaps a good portion of the woofers. in terms of vertical directivity, this is the best you will be able to do without cutting holes your precious horn.
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Yeah I know but not sure I want to do that, having so much of the midrange playing through bandpass ports...


Is it a correct analysis of this XDir simulation that two side-by-side drivers spaced 35 cm apart (e.g. 3 x 12" woofers) would have a directivity (-6dB) of about 90-100 degrees at 550Hz, i.e. the same as the SEOS-24?


An externally hosted image should be here but it was not working when we last tested it.
 
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tommus

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Joined 2009
Yes, I didn't think of that... I am not sure how low he crosses the woofers but I'll bet it's lower than 550hz.

Your sims show that it's in the ballpark, but you would have to make some measurements to know for sure. Also, the woofers may not sum coherently at the crossover, they are at 1/2+ wavelength separation. But that might be a minor effect.
 
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NiToNi

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Joined 2004
tommus said:
the woofers may not sum coherently at the crossover, they are at 1/2+ wavelength separation.
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Good point I'll crunch some numbers on that too.


So I can see why one would want side-by-side woofers under a waveguide to get a smooth transition of directivity at crossover but that's horizontally only. If anything, the vertical directivity is much worse, with side-by-side 12" woofers being omni at 550Hz. That just HAS to be audible in the uneven power response, no??


Is the answer another pair of side-by-side woofers above the waveguide, in an MTM configuration? Or would it make the mismatch in vertical dispersion even worse?
 
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tommus

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Joined 2009
I think woofers in an MTM arrangement would probably overshoot the horn's directivity as much as the TM would undershoot.

I've spent a bit of time trying to come up with the best case scenario for exactly this complement of drivers: BMS coax/SEOS 24 and some array of direct radiating woofers.

I've come to the conclusion (and others before me have too) that a 3-way synergy is a better solution: full-range directivity and better mid-bass performance for a lot less $$$. More mental and physical labor, but a lot of the design parameters can be found in bits and pieces around this site if you put in the research time.
 
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cspieker

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Joined 2018
There is another option for matching directivity at the crossover, using a smaller horn right down to its cutoff or a bit lower and using some eq and overlap with the woofer and/or asymmetrical slopes to come close.

It has the disadvantages of much lower power handling (irrelevant for home use with that bms, my 1.75“ diaphragm cd from 500hz even plays very loud).

Also it obviously will have no directivity below the crossover, and polars will never be as impressive as synergy.

It also works best with a horn rather than a constant directivity wg, which means it's a sweet spot speaker with tonal balance changes as you move around the room, not everyone's preference.

The horn polars below are from mine that I cross at 500.
 

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pk

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Joined 2003
Hi Jzagaja,

I was thinking even bigger than the EOS 250:). The upcoming 1.4" B&C DCX464 has an Fs around 250 and may therefore be fine for home use down to 220-250 Hz on a sufficiently large horn/waveguide.

Getting below 300 Hz makes the integration with a woofer much easier!

Best regards
Peter



jzagaja said:
I already made such - AiA Cinema model Black Swan (2" throat, 3deg, 60x40). Alternative is Marcel's work:

hifi.slovanet.sk :: Zobrazi? t?mu - Zvukovody STH - teorie a praxe
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