Understanding Danley Synergy ?

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Looking at line-array-paper.pdf it states this

Secondly, if the placement of the drivers on the side of the horn is correct, and the crossovers are correct, the apparent source over the entire range will be the apex of the horn! By carefully designing the horn and the crossover, a true phase coherent source is produced. The Synergy Horn™ then has all the elements needed to be a close to ideal loudspeaker with no need for any external processing of any kind. Simply hook up a poweramp channel and you are in business.

In the screenie i've taken from the PDF, i've added coloured lines to depict what i'm "presuming" are the path lengths for each driver. It "appears" that the time alignment between each section, is different. Is electronic delay used in the Xovers to "correct" this, if not, how is time alignment achieved ?

Furthermore, i can see how the horn dimensions would be fine for the Mid/Tops, but for the Bass it seems extremely foreshortened. How does it manage to achieve an f3 of 50Hz ?
 

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@ jeno

Hi, i read the patent, but you know what the're like for gobblygook talk :D in amongst the interesting details !

Thanks for the info :)

I'm surprised the SH-50 is only 100dB @ 2.83V @ 1M. Especially as it's rated @ 4 Ohms !
 
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Hi Zero D
To understand how they work, start with subwoofers. If you take two identical subs and put them side by side, they are not twice as loud but 4 times as loud, 6dB. Take 4 and put them side by side and now they are +12dB or 16 times louder than one. You are putting in 4X more power but get 16X as much sound because they couple acoustically and act as a single larger and more efficient driver.
When drivers are about ¼ wavelength apart or less, they combine like this, into one more efficient source. If the spacing is larger than about 1/3 wavelength, the sources radiate as individual sources and the coupling and acoustic efficiency increase does not occur Two or more sources radiating the same signal from different locations, produces an interference pattern, a series of lobes and nulls as one moves around the loudspeakers radiation space.
The object of the Synergy horn is to combine multiple drivers, covering multiple frequency ranges into one single horn radiation, without any lobes and nulls and in most cases, to eliminate the phase shift the crossovers normally add. A loudspeaker like that SH-50 has constant directivity and you can walk up, even put your head into the horn and there is no trace of anything but one source floating in front of you.
It can reproduce a square wave over a broad band and by measure, by listening, by radiation pattern, it appears to have one crossover less driver.
We aren’t selling these for the home, an SH-50 works fine (I use them) but they are large and not pretty. As much as possible, my general objective is very large scale hifi sound.

The sensitivity is limited to about 100dB because the cabinet is constant directivity and has a wide pattern (50 by 50 degrees) all the way to the top. If the horn narrowed up high, the on axis sensitivity could be higher but then it wouldn’t be CD..

Prosound Network: Danley Sound Labs SH-50 Loudspeaker

If you have headphones, you can hear the difference this “single source” radiation makes in large scale sound where many large concert line arrays in sports stadiums have fallen to be replaced with a relative few Synergy horns.

https://www.youtube.com/watch?v=CWtADec3abc

Penn State Demo.MOV - YouTube

2 boxes replace 44 line cabs

Danley Sound Labs Jericho on Ledreborg 2012 - YouTube

Unlike most loudspeakers, the spectral balance doesn’t change with distance.

Newnan High School, Newnan Georgia - Latest Danley Jerico JH90 Stadium Speaker Technology by Performa Technologies, Inc. on Vimeo

the smallest of the J series synergy horns.

Danley Sound Labs - YouTube

same demo but at 500+ yards

Jericho Horn J3 Debut - YouTube
Enjoy
Tom
 
Tom,

I have seen the 6dB figure explained as 3dB due to the increase in surface + acoustic coupling and 3dB due to the VC in parallel resulting in half the impedance, so double the amplifier power (3dB).

_-_-

Also the OP was asking about the physical distance/offset between the drivers, high, mid, low and how they are maintained in phase, since the woofer (for example) is a good distance in front of the HF driver.
 
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The OP's drawing is based on centers of voice coils, which sometimes works as a crude approximation of difference between acoustic centers, but doesn't indicate the actual acoustic centers even without a horn involved. It's a smart question even if the drawing is wrong, though.

Hey Tom, if I may be so bold, I suggest this is the question the OP needs answered:
Does the device...
1. Physically align the effective acoustic centers of the drivers into a point source right from the get-go? In that case, the crossover can keep them as such, or rotate 360° or whatever, and keep getting great results. The OP might appreciate an explanation of how their drawing should look to accurately reflect the acoustic centers. Or...
2. Physically align the acoustic centers such that while they are not actually equal in path length, it is easy for the crossover to bring them into good phase tracking on axis, and the horn is what manages to keep that working off-axis. In that case, it doesn't matter as much how the OP's drawing is off, only that they are close enough to make it work, which obviously they are. I realize #1 would also rely on the horn in a different extent, but ya know..

I've never really looked into it much to be honest. I just accepted it worked one way or the other, and both sound like a good trick to me, and I'm too lazy to try to figure it out right now but felt like posting anyway :D.
 
Group delay inherent with drivers and crossovers is significantly compensated for by the driver layout, resulting in speaker that does reproduce good approximation of square wave over portions of spectrum. Similar performance has been achieved with more conventional speakers with front baffles tilted back.

More important than the absolute phase performance is constraint of effective acoustic centers of drivers to approximately 1/4 wave separation distance through crossover points. This completely eliminates lobe behavior in both vertical and horizontal plane.

Driver separation on flat baffle with WTW or WMTMW layouts typically fail to get 1/4 wave distance of crossover point as separation of acoustic centers. Simple example: 6" driver and 1" dome tweeter. Discounting driver frames, acoustic centers on flat baffle can be no closer than 3.5"; this is 1/4 wave length for about 964Hz. Use of this as crossover point with typical 1" dome and typical crossover slopes isn't done because it leads to very poor power handling and IMD for tweeter. When 1" dome with magnet and face plate are accounted for, acoustic center spread increases.

Speakers such as Linkwitz Pluto overcome this too, but what Tom has with his design is suitable for PA, cinema, and for home use for those who have the space.
 
Yeah, but the distance between the mid and the compression driver in the Synergy is far more than 1/4 wave at the xover point of the compression driver - no doubt higher than "964Hz", therefore a smaller distance would be required.

The issue isn't so much a good phase relationship between any two drivers around the xover for flat response, as much as it is having them sum properly when looking at an impulse. If they can't do that then they can't "reproduce a square wave". I'm speculating that this may be the key to how the distances were figured out in practice. The xover's phase flip may also play a role in the spacing...

I'm guessing that Tom doesn't really want to comment on this point, since it may be something of a proprietary "secret".

_-_-bear
 
Driver separation on flat baffle with WTW or WMTMW layouts typically fail to get 1/4 wave distance of crossover point as separation of acoustic centers. Simple example: 6" driver and 1" dome tweeter. Discounting driver frames, acoustic centers on flat baffle can be no closer than 3.5"; this is 1/4 wave length for about 964Hz. Use of this as crossover point with typical 1" dome and typical crossover slopes isn't done because it leads to very poor power handling and IMD for tweeter. When 1" dome with magnet and face plate are accounted for, acoustic center spread increases.

The woofer distance in a WTW configuration is even greater, 6.5" with the tweeter in between hence the crossover would need to be even lower which is not feasible.
 
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but the distance between the mid and the compression driver in the Synergy is far more than 1/4 wave at the xover point of the compression driver

You are mixing things up. The 1/4 wavelength rule accounts for drivers of the same type/frequency-range. The distance between drivers of different working range is determined by the group delay of drivers and crossover.

Regards

Charles
 
Except if both drivers are radiating at the same frequency, then the distance between them, including group delay and xover phase flips and time delays, if not properly set will certainly cause lobing, which means variations in the polar response in the axis that is lengthwise between the two drivers... like at the xover region.

As far as WTW systems, they suffer from this very problem, thus the interest in full range and coaxial drivers - an attempt to obviate this issue.

But regardless, take the relationship between the mid and woofer, the question is by exactly what means do the mid and woofer's output sum coherently given their physical offset along the mouth of the conical horn? I'd find it hard to believe that group delay or the delay/phase flips of the xover can account for the differential. The reason I am skeptical is that one does not need or see such an offset when (for example) one stacks a three-way system with individual boxes (permitting physical positioning). So why the difference?

Or stating it the other way, why don't all the drivers enter at or near the throat, as per earlier art?

Is an all-pass delay used in the "passive" Synergy xover??

_-_-

_-_-
 
Hi All
Bear, that is correct, it is the mutual radiation which the drivers share when closely coupled which raises the electroacoustic efficiency of the direct radiator and it is the increase in radiation resistance which causes a horn to have a higher efficiency. For multiple drivers to coherently drive a horn as one source, that spacing must also be recognized.

Dumptruck poses questions;

#1, yes the physical / acoustic spacing MUST be held (that ¼ wl spacing or less) in order for the sources to radiate spatially as one acoustic source. With a larger spacing than about 1/3 wl, then the sources radiate independently, the mutual coupling is gone and what you get, depends on the vector sum of the two sources.
As you move around the speaker, whenever the difference in path length is N X 1/2wl, one has a cancellation notch and null in the polar pattern. In commercial sound while unavoidable using multiple sources, an interference pattern is very bad because the lobes that point out in the wrong directions (not the listening area) excite room sound and the directivity (energy in the right direction compared to energy going everywhere else) directly relates to being able to understand random words etc (and preserving information related to the stereo image in the recording).

#2, in all “normal crossovers” like those with names, once past first order, the summed output has an “all pass” phase response. That is a flat amplitude but phase rotation equal to the number of orders times 90 degrees. This places the upper and lower crossover outputs at two different times (hf first, lf later) and this can be seen looking at the Group delay of any simple crossover. Most crossovers do this and is normal behavior.
For the Synergy horns, part of the design uses the inverse spacing of the low, mid and high sources, conceptually like an FIR filter where passively, the hf is delayed the most, the mids less and lf the least to offset the electrical part.
This will not work with any “named” crossovers even without the magnitude and phase of the individual frequency bands added in. In this case, with all the drivers directly coupled acoustically, like signals through a resistor network, one cannot get away with an error or on gets a whopping big cancellation notch everywhere not just one spot..

This then requires a crossover who’s magnitude and phase is what is required to mate the magnitude and phases of each range and this is never a normal test book shape but one that is adapted to the conditions. How i do that has evolved but is certainly based on careful measurements of the real thing.

The SH-50 referenced that I designed in 2005 will reproduce a square wave from near perfect to fair on an O-scope, from about 250Hz to about 2900 Hz, spanning both crossovers and like most all of them, even the largest 10 feet tall with over 100 drivers, sounds like, acts like, measures like a single crossover-less driver.

A technical idol of mine was Dick Heyser, a person I only met once and didn’t really have the nerve at the time to talk to. I have had his TDS measurement system for over 30 years and the last push to get rid of the crossover phase shift was an effort to reach a goal he had set out in one of his very last papers before his death about 25 years ago.
A friend and co-worker Doug Jones knew Dick and is caretaker of the Heyser library and archives at Columbia College in Chicago where Doug (now professor emeritus) taught acoustics and was department chair.
If I had a magic wand, I would want to show Dick what we have done and took 15 years of my life to finally reach the target he drew.
Then, I would have a list of questions on things he wrote about I am still trying to understand.
The man was just plain brilliant, he saw things a different way than anyone before, maybe since.
Best,
Tom Danley
 
I don't understand why you guys think the path lengths look so different. Like I posted earlier, I don't actually know how the relative phase ends up, but the alignment looks pretty close already to me.

The original drawing posted ignores the actual entrances to the horn. The HF is at the back and the VC is right there at the entrance. The MF is a bit forward in the horn, but its VC is also farther out from its entrance. The LF is farther forward in the horn still, but its VC is even farther from its entrances. Makes sense, no?
 
@ Tom Danley

Hi, Thanks for the info & links in Post # 4 :)

I saw the square wave pics in one of your PDF's, very impressive.

Large and not pretty.

They are as big as they need to be, so no worries there ;) Looks aren't everything, it's how they sound/perform that's the main criteria !

my general objective is very large scale hifi sound

From what i've read/seen you've achieved it.

So using different order Xover slopes for each set of fo's realigns the TD ?

Re sensitivity limited to about 100dB

I see. Obviously with higher dB drivers that would improve. But i imagine you've tested quite a number from various manufactures already ;) Plus i know that there's more to good sound than just dB @ 1 W !

I can envisage the SH-50 producing Extremely convincing stereo images, & all without DSP etc = :)

Next time i visit the USA, don't know when, i'd Love to actually hear the SH-50's + your TH's together.

Originally Posted by bear

Also the OP was asking about the physical distance/offset between the drivers, high, mid, low and how they are maintained in phase, since the woofer (for example) is a good distance in front of the HF driver
.

Indeed i am, Thanks :)

Originally Posted dumptruck

The OP's drawing is based on centers of voice coils,

It was

which sometimes works as a crude approximation of difference between acoustic centers,

I accept my drawn lines were just an estimate.

Thanks for your input :)
 

ra7

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One question I have, and it might be a silly one, is how does drilling tiny holes along the length of the horn allow the drivers to radiate properly? I mean, doesn't the hole, which can be thought of as a small pipe, have an impact on the frequency response? Doesn't it act as a bandpass and limit the max and min frequencies that will be passed... kind of a port in a vented enclosure?
 
Hi
Zero, this might be hard to believe, but that hf driver is already one of the top couple most efficient drivers available at any price. It is the wide dispersion, maintained up high, which forces it down. On a horn which narrowed up high, that driver can deliver over 110dB on axis sensitivity.
Keep in mind, on a CD horn, it is usually the hf drivers sensitivity in the top octave that limits the overall sensitivity.
The holes are another part of the design. You may have noticed that as you drive loudspeakers harder and harder, they get “bright” and eventually harsh sounding. Harmonic distortion starts an octave above the real signal and extends upwards by 2,3,4,5 etc times the input frequency.
While that brightness may not be objectionable, the object here is to be a faithful reproducer and one thing that means the spectral balance should not change with level if possible.
The trapped air volume under the cone and the small holes, form an acoustical 2nd order low pass filter, like an electrical filter but in air. The object being that the harmonic distortion the drivers invariably produce, will be attenuated and not enter the horn. The effect does limit the bandwidth and that is the object of it. The idea is you DO NOT want sound the driver produces on it’s own (not part of the input signal) which is always above the electrical crossover and the short obstruction does not affect the horns radiation resistance.
Best,
Tom
 
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