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rosey

meh question

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hi all, I'm wondering if a jbl 2385a horn is too small to integrated well as a center meh with jubilee mains. thx much rosey

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You'll wind up with a separate bass bin of some sort to cross to, at ~500 Hz, which will make the size of the entire MEH/bass bin about the same size as a K-402 horn, Belle, or slightly less deep: a Cornwall.  I've used all three, and the K-402-MEH wins, hands down. 

 

I think you'll find that any distortion in a center loudspeaker will dominate over the front left/right Jubilees, and that you'll notice a detectable hole in the front soundstage on either side of the center while walking across the width of the room (depending on the width of your listening room).  See the following for a JuBelle (using approximately the same sized HF horn that you're considering: 

 

gallery_26262_6_1571719.jpg

 

...and the K-402-MEH thread that discusses the differences in sound stage and sound quality comparing a JuBelle and K-402-MEH:

 

 

YMMV.

 

Chris

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Perhaps a short explanation of "why"...The basic MEH (horn) mouth must be large enough to hold the horizontal wave at the lowest frequency that the horn can contain before losing all directivity control (i.e., the horizontal beamwidth goes beyond 180 degrees)--and that dimension is a half wavelength of sound at that lowest frequency.  Here is a horizontal polar spectrogram of a similar-sized and shaped horn of the JBL horn that you identified:

 

K-510 with K-69-A horizontal polar sonogram.jpg

 

and the vertical direction of that same horn:

 

K-510 with K-69-A vertical polar sonogram.jpg

 

Note the loss of output below ~500 Hz due to the loss of directivity, first in the vertical direction (the smaller mouth dimension) and then in the horizontal direction. This is the point that the horn no longer will support lower frequencies--the "cutoff" point. 

 

So there is a minimum size of the horn mouth that will support horn loading.  For a 200 Hz loss of horizontal directivity, that's 34 inches (minimum).  The K-402 with its 38" of horizontal mouth size begins to lose horizontal directivity below ~170 Hz (half-space loading), and loses it completely at 100 Hz, whereupon the frequency is low enough that room boundary loading can take over in half space using MEH loading of woofers from ports off the central axis of the horn (the  "off-axis ports"). The horn loads even better in quarter space (wall/floor, wall/wall, wall/ceiling) and in eighth space (wall/wall/floor, wall/wall/ceiling), thus increasing its low frequency extension rather dramatically. 

 

The K-402-MEH was sized to  be able to support full-range operation as a center loudspeaker in half-space operation, and it does that job very well.  I've been able to get good response down to 16 Hz (-3 dB) via DSP crossover EQ, while still retaining good sound quality without significant increase in harmonic distortion.  But that response depends on half-space loading (or 1/4, 1/8). 

 

I found that the lack of low frequency extension to match the front left-right loudspeakers is a very large "dissatisfier" in use, and I could never get the center JuBelle to cover the 30-60 Hz band well, due to the Belle bass bin's cutoff at 60-70 Hz in quasi-quarter space against the front wall and situated with a full/solid riser below it all the way to the floor.

 

Chris

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thx chris, I knew youdshow me the light. there's 1 on ebay with a 4592nd coax on it but saw how small the mouth was . thankyou for the conformation

also the 535b jobs arrive tomorrow.  pray they going to show up in 1 piece. I mentioned earlier that I had bms 4592s. didn't realize until you mentioned it, that the 2way would need a coax version. didn't know there was one! so I'm thinking of robbing the bms from my volti klipschorns for the mids, and also using the beyma cp 25 for the HD but think it's a 1"  product. what say you? thx much. rosey.

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