Hi Salas
I am familiar with F1, they just replaced a large F1 system at a sports stadium with our full range point source cabinets.
If you have all of the sound (high mid lows etc) come from one source, one can eliminate all of the comb filtering a large array like the one in the link produces. With large arrays, even a small breeze causes audible effects, if you can radiate a single uniform sound field with no lobes or nulls, then even a strong wind has hardly any effect on the sound. With constant directivity and pattern control, one can aim the envelope at the farthest seats and in the case of Troy stadium, only have a 4dB difference in loudness from the closest to farthest seat using a single cabinet..
Notice nearly all of these horns have a constriction at the radiator , some are holes, some are slots but they have no acoustic gain.
In use, it is possible to fill an entire stadium with one box and produce excellent sound 101dBa slow at 700 feet and unlike large arrays, the spectrum doesn’t change with distance other than some hf air absorption. A couple links;
Danley Sound Labs Tagged Articles - Pro Sound Web
ONE DANLEY JERICHO HORN COVERS 30,000 FANS AT TROY UNIVERSITY | The Wire on SVConline
PRO AND COLLEGE SPORTS FACILITIES CHOOSE DANLEY | BriefingRoom on MixOnline
The basic premise "how it works", starts on the middle of page 3;
http://www.danleysoundlabs.com/pdf/danley_tapped.pdf
Best,
Tom
I am familiar with F1, they just replaced a large F1 system at a sports stadium with our full range point source cabinets.
If you have all of the sound (high mid lows etc) come from one source, one can eliminate all of the comb filtering a large array like the one in the link produces. With large arrays, even a small breeze causes audible effects, if you can radiate a single uniform sound field with no lobes or nulls, then even a strong wind has hardly any effect on the sound. With constant directivity and pattern control, one can aim the envelope at the farthest seats and in the case of Troy stadium, only have a 4dB difference in loudness from the closest to farthest seat using a single cabinet..
Notice nearly all of these horns have a constriction at the radiator , some are holes, some are slots but they have no acoustic gain.
In use, it is possible to fill an entire stadium with one box and produce excellent sound 101dBa slow at 700 feet and unlike large arrays, the spectrum doesn’t change with distance other than some hf air absorption. A couple links;
Danley Sound Labs Tagged Articles - Pro Sound Web
ONE DANLEY JERICHO HORN COVERS 30,000 FANS AT TROY UNIVERSITY | The Wire on SVConline
PRO AND COLLEGE SPORTS FACILITIES CHOOSE DANLEY | BriefingRoom on MixOnline
The basic premise "how it works", starts on the middle of page 3;
http://www.danleysoundlabs.com/pdf/danley_tapped.pdf
Best,
Tom
Earlier in the thread, responding to comments that there is no difference
at 2 meters, I performed the following experiment:
I measured the response on axis at 3 m. Then I turned the speaker around
so that the slot was facing the rear and re-measured, overlaying the curves.
The difference in the range between 30 and 100 Hz was about 2.5 dB.
Great, Nelson. But if I understand, what you have done it unfortunately doesn't prove anything about efficiency. What shows is more about relative delays.
I made some simulations:
An externally hosted image should be here but it was not working when we last tested it.
Here the red and green are simulation where the the delays are symmetric and the source strength is equal, red and unequal, green. As you can see, even though the source strength are unequal (green) the amplitude at the front and rear are the same. The effect of unequal source strength is to "fill in" the dipole nulls.
Next, blue and violet show the cases where the delays are asymmetrical for equal (blue) and unequal (violet) source strengths. In this case it is observed that the front is higher SPL then the rear, regardless of whether the source strength is equal or unequal. A null at the rear (cardioid) will be obtained only with equal strength sources and the correct delay asymmetery.
The assumption here is that both sources ultimately generate a spherical wave in the far field which for frequencies between 30 and 100 Hz should not be too much of a stretch.
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Hello Tom,
Yes I have seen about your work for a long time now and it has given the high SPL point source a second life it seems. I mentioned Funktion One (former Turbosound owners and classic era Pink Floyd PA supporters) as general point source proponents, not as coherent point sources.
Regards
Hi John,
You are quite correct.
The efficiency argument, which is separate, comes from Heil's design,
where the ratio of acoustic output vs cone motional energy is improved.
If Heil is wrong, I can live with that.
I was inspired by your simulation enough to go measure the speaker output
at 1 meter in the area where we expect the dipole cancellation. Looking at
the curves for the octave centered around 70 Hz, I get the most cancellation
at exactly 90 degrees, with an 11 dB dip.
From your sim, I would interpret that as symmetric delay but unequal
source strength.
at 1 meter in the area where we expect the dipole cancellation. Looking at
the curves for the octave centered around 70 Hz, I get the most cancellation
at exactly 90 degrees, with an 11 dB dip.
From your sim, I would interpret that as symmetric delay but unequal
source strength.
I was inspired by your simulation enough to go measure the speaker output
at 1 meter in the area where we expect the dipole cancellation. Looking at
the curves for the octave centered around 70 Hz, I get the most cancellation
at exactly 90 degrees, with an 11 dB dip.
From your sim, I would interpret that as symmetric delay but unequal
source strength.
Would seem to suggest that. An 11dB dip would imply about a 1.5dB difference, but would still imply equal 0 and 180 degree amplitude. Your 2 and 3 M results seem to suggest that at least when you are out 2M or more the wave fronts are pretty much fully developed. Certainly, what ever it is, it is. We just haven't figured out what it isn't.
I'm planing on building a scaled down version so I can run a full set of measurements including polar plots. Hopefully what you are seeing isn't unique you your exact configuration. And I think Tom D's suggestion on looking at the effect of slot loading is something I might look at too.
Great to find something interesting to look at. Over here in New England summer is winding down quickly.
Hi, I've pointed that out twice already, but its just ignored, rgds, sreten.
Hi,
I assume you have two woofers, so a force cancelling linkage between the
two might render some minor performance advantages, just a thought ....
But it wouldn't be unanticipated then would it ....
rgds, sreten.
I'd say that the increased radiation resistance from the velocity transform is lost again at the discontinuity at the slot.
John K's intensity considerations are correct IMO. Only a horn would allow us to effectively make use of the improved loading.
That doesn't mean that it is unusable OTOH - which is shown by the practical implementation of course. I'd say the biggest advantage is that one can have a lot of Vd in a physically compact arrangement.
I could also imagine a "dipole" sub that can be placed close to a wall to be constructed with such a slot arrrangement.
Regards
Charles
John K's intensity considerations are correct IMO. Only a horn would allow us to effectively make use of the improved loading.
That doesn't mean that it is unusable OTOH - which is shown by the practical implementation of course. I'd say the biggest advantage is that one can have a lot of Vd in a physically compact arrangement.
I could also imagine a "dipole" sub that can be placed close to a wall to be constructed with such a slot arrrangement.
Regards
Charles
What still puzzles me is the actual front side/back side loading issue. What is the frequency dependency? Certainly it's not the same across the usable spectrum of this configuration. What is it's influence, especially if we consider that it is not horn loading, at least not in any meaningful way?
Dave
I think people like Tom (Mr. BigBass) Danley could answer this in a physically sensible way.
Another question arose: What if this slot is coupled to a horn that is actually too small to be useful as a bass-horn in the usual sense but still oofers some increased coupling to the surrounding air ? If it would just increase the radiated power by a factor of 1.5 or even less it would be quite cool and offer some reasonably sized open-baffle sub implementation. I am not talking of high SPL P.A. bass - just some improvement over the usual dipoles.
Regards
Charles
Another question arose: What if this slot is coupled to a horn that is actually too small to be useful as a bass-horn in the usual sense but still oofers some increased coupling to the surrounding air ? If it would just increase the radiated power by a factor of 1.5 or even less it would be quite cool and offer some reasonably sized open-baffle sub implementation. I am not talking of high SPL P.A. bass - just some improvement over the usual dipoles.
Regards
Charles
Making progress with my scaled model. The baffle is 11" wide by 18 1/3" tall, a scaled version of Nelson's. The slot is designed to have an opening of 1/3 the total driver S and is 3/4" wide by 10 1/2" tall. Drivers will be 4 Vifa MG10 4" woofers. Due to the scaling I should be able to get good anechoic response down to 200 Hz. The dipole peak should occur at 800 Hz so I should have very good measurement capability in the low frequency region.
Slot with side cover off.
Slop with both side cover on.
Completed slot viewed from opening.
Front view of slotted baffle.
Rear view of slot mounted on baffle, ready for driver mounting.
Slot with side cover off.
An externally hosted image should be here but it was not working when we last tested it.
Slop with both side cover on.
An externally hosted image should be here but it was not working when we last tested it.
Completed slot viewed from opening.
An externally hosted image should be here but it was not working when we last tested it.
Front view of slotted baffle.
An externally hosted image should be here but it was not working when we last tested it.
Rear view of slot mounted on baffle, ready for driver mounting.
An externally hosted image should be here but it was not working when we last tested it.
Crossed my mind too. The Fostex & Tangband
3inch crowd is possibly cutting wood already.
Hi,
Well the arrangement has great mechanical (not acoustic) force cancelling,
it remains to be seen what the acoustic consequences are. i.e. how you
match the efficiencies of the FR and bass array and if this is distance
dependent, which it can be be with disparate dispersion profiles.
I have some 24" ribbons mated to 8" bass units, Celestion 5000's.
Never heard anything so listening position critical, due to dispersion.
rgds, sreten.
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