I've done some googling a long time ago and ended up with conflicting answers...
On a midbass horn I'm looking at having the smallest ctc spacing to the midrange horn. Does offsetting the midbass driver to the top of the cab move it's acoustic centre upwards ?
My intuition says no but hopefully I'm wrong ?
Dodgy pic to show the difference, viewed from the side..
On a midbass horn I'm looking at having the smallest ctc spacing to the midrange horn. Does offsetting the midbass driver to the top of the cab move it's acoustic centre upwards ?
My intuition says no but hopefully I'm wrong ?
Dodgy pic to show the difference, viewed from the side..
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I was thinking about the same question. My take on this is that what matters in this case --having such a long, long acoustical distance between the bass and mid drivers (all the way down through bass-horn and back) even with them being physically next to each other-- is to be acoustically aligned for the listener in front of them. So, I think these two situations are equivalent, no better or worse, they don't change directivity of the speaker.
3730 | JBL Professional Loudspeakers
HF MF from 3730, seems to tilt down nicely from 3meters.
HF MF from 3730, seems to tilt down nicely from 3meters.
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I was just talking about shape being similar to my waveguide.
Sure it does change vertical directivity and if your midbass is meter high you get floor bounce which might have bad effect to FR.
i dont know how big midbass horn you´re up to.
I have only get involved meter long 135hz inlow which start to fall from 200hz 4pi.
on the floor against the wall 1pi it went straight to 130hz usable.
Sure it does change vertical directivity and if your midbass is meter high you get floor bounce which might have bad effect to FR.
i dont know how big midbass horn you´re up to.
I have only get involved meter long 135hz inlow which start to fall from 200hz 4pi.
on the floor against the wall 1pi it went straight to 130hz usable.
Oh, it definitely moves it upward, though IME it's not noticeable until a piano or similar 'runs the scales' fast and its performance shoots upward. This was the main test that removed any lingering doubt I'd ever be able to accept any large multi-way that wasn't time/phase coherent. Guess all those early years only listening to live music or through single or co-ax drivers spoiled me.
Pretty cool though for Disney's Fantasia soundtrack. 😉
All that said, if a [super] tweeter is placed in the mid-range or even a wide range system in the mid bass it's often enough to 'fool' our brains into sufficient coherency if one doesn't sit inside the near-field, even if not time and/or phase corrected! [dual 15", 511E horns for reference]:
GM
Thanks for the replies folks.
Where I'm at right now is running a (build in progress) 60x40 2 way MEH 'top' above my 80Hz horns, with my 80Hz horns flipped on their side to match the width of the top cab.
Midbass horns are EV EVM 15L drivers on ~26" long 24" x 18" mouth horn, approx. 9" sq throat.
The midbass is flat 100 / 500Hz. I'll be crossing around 250 / 300Hz.
Centre to centre spacing will be 19.5" which is almost double the 1/4 wavelength rule (guideline?) at 300Hz, fairly close at 250Hz.
I built these midbass horns really well and wouldn't like to lose them, but was wondering if it was worth a new build to get the ctc spacing within 1/4 WL.
Thanks,
Rob.
Where I'm at right now is running a (build in progress) 60x40 2 way MEH 'top' above my 80Hz horns, with my 80Hz horns flipped on their side to match the width of the top cab.
Midbass horns are EV EVM 15L drivers on ~26" long 24" x 18" mouth horn, approx. 9" sq throat.
The midbass is flat 100 / 500Hz. I'll be crossing around 250 / 300Hz.
Centre to centre spacing will be 19.5" which is almost double the 1/4 wavelength rule (guideline?) at 300Hz, fairly close at 250Hz.
I built these midbass horns really well and wouldn't like to lose them, but was wondering if it was worth a new build to get the ctc spacing within 1/4 WL.
Thanks,
Rob.
You're welcome!
This apparently came from playing back a 1935 recording of an Eleanor Powell tap dancing scene that had an obvious echo due to the 8 ft path length difference between the LF and HF horn's drivers [mouth aligned], but found that once the motors were in vertical alignment no one could detect any echo in the 300 - 800 Hz XO range [3 ms max] and since they used 1st order XOs, the alignment was ~90 deg out of phase, so over time it apparently became known as the '1/4 WL rule' since I've seen nothing WRT its origin.
GM