Speakerplans.com Homepage
Forum Home Forum Home > General > General Forum
  New Posts New Posts RSS Feed - extremely high efficiency
  FAQ FAQ  Forum Search   Events   Register Register  Login Login

extremely high efficiency

 Post Reply Post Reply Page  <1234>
Author
Message
Racks&Stacks View Drop Down
Registered User
Registered User


Joined: 10 February 2006
Location: Germany
Status: Offline
Points: 204
Post Options Post Options   Thanks (0) Thanks(0)   Quote Racks&Stacks Quote  Post ReplyReply Direct Link To This Post Posted: 12 May 2023 at 10:55am
Originally posted by doller doller wrote:

Sorry to keep going on. Those 60mtr dance floors will be serviced by delay hangs won't they? Will they really put one 153db stack at the front and hope half of the audience wears ear plugs. 
I think my point was how many of us would really benefit from a 153db speaker box i.e. the common man. How many on here have installed a stadium? 
I think for most a poultry 130db is fine. Just my thinking.

Nobody ever said a rig had to be run flat out. Headroom is always good for system longevity and keeping distortion down. Yes, most of the 60m dance floor gigs will have budgets for delay towers, but not all.

but 130dB? That doesn't fly.
Back to Top
kipman725 View Drop Down
Registered User
Registered User


Joined: 02 September 2020
Location: Warrington
Status: Offline
Points: 231
Post Options Post Options   Thanks (0) Thanks(0)   Quote kipman725 Quote  Post ReplyReply Direct Link To This Post Posted: 12 May 2023 at 11:45am

worth a read.  There are lots of confusing aspects to using voltage sensitivity as a proxy for efficiency such as:
Solid angle radiated into
Impedance of the speaker (both magnitude and phase)

further some people are con-inflating the speakers electro acoustic conversion efficiency with broader aspects of operating it like the number of amplifiers channels required and the capacity of those amplifier channels. 

A speaker like the J8 is designed to be flown which reduces the SPL variation over the crowd by moving the speaker further away from the closest listeners.  As SPL is -6dB each doubling in distance we can do something like having the closest listener at 15m and the furthermost at 60m and only have 12dB level difference.  Rather than having the closest at  1m and the furtherest at 59m which results in ~36dB level difference.
Back to Top
snowflake View Drop Down
Old Croc
Old Croc


Joined: 29 December 2004
Location: Bristol
Status: Offline
Points: 3118
Post Options Post Options   Thanks (0) Thanks(0)   Quote snowflake Quote  Post ReplyReply Direct Link To This Post Posted: 12 May 2023 at 12:22pm
Originally posted by kipman725 kipman725 wrote:


worth a read.  There are lots of confusing aspects to using voltage sensitivity as a proxy for efficiency such as:
Solid angle radiated into
Impedance of the speaker (both magnitude and phase)

further some people are con-inflating the speakers electro acoustic conversion efficiency with broader aspects of operating it like the number of amplifiers channels required and the capacity of those amplifier channels. 

A speaker like the J8 is designed to be flown which reduces the SPL variation over the crowd by moving the speaker further away from the closest listeners.  As SPL is -6dB each doubling in distance we can do something like having the closest listener at 15m and the furthermost at 60m and only have 12dB level difference.  Rather than having the closest at  1m and the furtherest at 59m which results in ~36dB level difference.


many of the danley boxes have the dispersion tailored so that there is negligible difference between front and back.
Back to Top
fatfreddiescat View Drop Down
Young Croc
Young Croc
Avatar

Joined: 15 October 2010
Location: N.E.Wales
Status: Offline
Points: 1081
Post Options Post Options   Thanks (0) Thanks(0)   Quote fatfreddiescat Quote  Post ReplyReply Direct Link To This Post Posted: 12 May 2023 at 12:43pm
Originally posted by fudge22 fudge22 wrote:


 If you intend to go down the “pack as many drive units as you can get in the box” route, to get insanely high output levels, it might also be worth reading chapter 15 of the book The Physics of Vibration and Waves, which covers non-linear effects in acoustic waves. The linearity of the longitudinal acoustic waves assumes air has constant bulk modulus. At high sound pressure levels this is no longer true.

 



It would be interesting to know how audible this is with modern designs such as line array waveguides and the Danley boxes.
Back to Top
snowflake View Drop Down
Old Croc
Old Croc


Joined: 29 December 2004
Location: Bristol
Status: Offline
Points: 3118
Post Options Post Options   Thanks (0) Thanks(0)   Quote snowflake Quote  Post ReplyReply Direct Link To This Post Posted: 12 May 2023 at 12:48pm
Originally posted by fatfreddiescat fatfreddiescat wrote:

Originally posted by fudge22 fudge22 wrote:


 If you intend to go down the “pack as many drive units as you can get in the box” route, to get insanely high output levels, it might also be worth reading chapter 15 of the book The Physics of Vibration and Waves, which covers non-linear effects in acoustic waves. The linearity of the longitudinal acoustic waves assumes air has constant bulk modulus. At high sound pressure levels this is no longer true.

 






It would be interesting to know how audible this is with modern designs such as line array waveguides and the Danley boxes.


on an exponential horn throat distortion does become audible at high drive levels, which is one of the reasons for using a conical horn and multiple drive units - the other being constant directivity.
Back to Top
fatfreddiescat View Drop Down
Young Croc
Young Croc
Avatar

Joined: 15 October 2010
Location: N.E.Wales
Status: Offline
Points: 1081
Post Options Post Options   Thanks (0) Thanks(0)   Quote fatfreddiescat Quote  Post ReplyReply Direct Link To This Post Posted: 12 May 2023 at 12:59pm
Originally posted by snowflake snowflake wrote:

Originally posted by fatfreddiescat fatfreddiescat wrote:

Originally posted by fudge22 fudge22 wrote:


 If you intend to go down the “pack as many drive units as you can get in the box” route, to get insanely high output levels, it might also be worth reading chapter 15 of the book The Physics of Vibration and Waves, which covers non-linear effects in acoustic waves. The linearity of the longitudinal acoustic waves assumes air has constant bulk modulus. At high sound pressure levels this is no longer true.

 



I agree, the chapter referenced above looks at another effect that is different to purely rarefaction and compression introducing an asymmetrical waveform, ie second harmonic distortion but looks at how the wave front itself bunches up do to the change in density of the air and hence the speed of sound through it changes, effectively the high frequencies travel faster when the fundamental is at or near maximum pressure.


It would be interesting to know how audible this is with modern designs such as line array waveguides and the Danley boxes.


on an exponential horn throat distortion does become audible at high drive levels, which is one of the reasons for using a conical horn and multiple drive units - the other being constant directivity.
Back to Top
fudge22 View Drop Down
Registered User
Registered User


Joined: 26 July 2022
Location: UK
Status: Offline
Points: 65
Post Options Post Options   Thanks (0) Thanks(0)   Quote fudge22 Quote  Post ReplyReply Direct Link To This Post Posted: 14 May 2023 at 10:46pm

Quote but 130dB? That doesn't fly

If I have understood you correctly, I presume that you are unconcerned about hearing loss or tinnitus.

Quote many of the danley boxes have the dispersion tailored so that there is negligible difference between front and back.

There was a thread (years ago) on prosound forum where, after someone called bull on one of their claims, it was concluded that the Danley design worked because of magic. I assume that this works using the same voodoo. As Kipman said the technique the rest of us use to reduce variation between front and back is to position the speakers (usually by flying them) to reduce the path length variation.

The distortion caused in horns is covered in Beranek’s book Acoustics, or the more recently published Acoustics: Sound Fields and Transducers.

The distortion goes up as the frequency increases above the cut-off frequency and as the sound intensity increases at the throat.

Intensity = sound pressure squared / air density x speed of sound in Watts/square metre

Sound pressure can be determined from sound pressure level.  Note that usually in acoustics any value with level in its name is a logarithmic ratio compared to a reference value. So sound pressure level is dBs and sound pressure is bar or Newton/metre squared.

If you know the spl at 1m (153 in the J8 case), then knowing the mouth area and the dispersion angle you can calculate the intensity in W/m^2, multiply it by the area covered and find the total acoustic Watts needed. Assuming no losses, the same acoustic Watts must come from the drive units, so knowing the number of compression drivers and their throat area you can calculate the intensity at the throat.

The reason conical horns produce less distortion than exponential ones is that the cross-sectional area increases more rapidly near to the throat, so the pressure drops off more quickly. The downside is that there is very little acoustic loading and the flare acts more as a waveguide.

Most loudspeakers only have constant directivity over a limited frequency range. The J8 has a 90-degree horizontal dispersion between 700HZ and 4KHz and a 40-degree vertical above 1.6KHz. Based on the drawings it is likely that the flare of the J8 is seen as a simple discontinuity below about 400Hz.

Back to Top
snowflake View Drop Down
Old Croc
Old Croc


Joined: 29 December 2004
Location: Bristol
Status: Offline
Points: 3118
Post Options Post Options   Thanks (0) Thanks(0)   Quote snowflake Quote  Post ReplyReply Direct Link To This Post Posted: 14 May 2023 at 11:20pm
I'd be very interested if you can find a link to that prosound forum thread as in twenty years of being aware of him I've never known Tom Danley to claim anything that isn't backed up by theory and measurement.
Back to Top
Racks&Stacks View Drop Down
Registered User
Registered User


Joined: 10 February 2006
Location: Germany
Status: Offline
Points: 204
Post Options Post Options   Thanks (0) Thanks(0)   Quote Racks&Stacks Quote  Post ReplyReply Direct Link To This Post Posted: 15 May 2023 at 10:14am
Originally posted by snowflake snowflake wrote:


many of the danley boxes have the dispersion tailored so that there is negligible difference between front and back.
just the genesys horns do that, due to a tapered hf exit. the horns spread out energy differnetly than simply tilting the horn.

all he others function the same as an other horn: hang high and aim the energy where you need it


Edited by Racks&Stacks - 15 May 2023 at 10:17am
Back to Top
toastyghost View Drop Down
The 10,000 Points Club
The 10,000 Points Club
Avatar

Joined: 09 January 2007
Location: Manchester
Status: Offline
Points: 10920
Post Options Post Options   Thanks (3) Thanks(3)   Quote toastyghost Quote  Post ReplyReply Direct Link To This Post Posted: 16 May 2023 at 5:08am
Coming out of retirement despite myself because the bullshit around here has piled up so high that I can smell it from my cosy little hideaway.


I'll try and work through in order, but I'm old and tired so sorry if I've missed anyone out.

Originally posted by doller doller wrote:

Yes fudge all calculated I expect.

Danley are one of the few manufacturers that publishes measured data with the parameters of the measurement and graphing choices.

I might not agree with their choices on every occasion - and frankly I think the J8-94 is a bit of an odd duck - but the data is clearly there if you care to look:


So that's a measured maximum SPL and oh look, they included a repeatable measurement standard too! Yes, the M-Noise test method is an AES standard. AES75-2023: AES standard for acoustics — Measuring loudspeaker maximum linear sound levels using noise. How about folks start citing their sources on this forum? Wouldn't that be nice!
https://www.aes.org/publications/standards/search.cfm?docID=116
https://meyersound.com/news/aes75/

Originally posted by fudge22 fudge22 wrote:

<p ="Msonormal">The thread starter was asking about efficient loudspeaker
designs. The synergy horn was brought up as a possible solution. However, the
figures of the product linked to, don’t support the notion of it being very
efficient, unless by efficient you mean highest output from smallest box.


Sounds like a pretty good measure of overall efficiency to me. If you can cover the audience with a box that occupies a tenth of the truck pack volume, uses a third of the number of amplifier channels, and in half the weight of the equivalent 12-deep hang of a mid-format line array system, is that not a more efficient way to do the gig?

Although yes, as has been rightly mentioned by kipman725 and yourself, electroacoustic efficiency is not electroacoustic sensitivity. It is sadly all too common that the two are confused, although I have to say that Keele's paper comparing horns and direct radiators is very old and could do with being revisited.

Originally posted by fudge22 fudge22 wrote:

Most loudspeakers only have constant directivity over a
limited frequency range. The J8 has a 90-degree horizontal dispersion between
700HZ and 4KHz and a 40-degree vertical above 1.6KHz. Based on the drawings it
is likely that the flare of the J8 is seen as a simple discontinuity below
about 400Hz.


This is correct, but the same rules of physics apply elsewhere too. The original VDOSC manual was quite thorough in ensuring that users of the system were aware that the stated horn/waveguide coverage angles were only achieved from 700 Hz to 12 kHz. That was excised in the later, less dense revisions, but is still there if you care to check the software or GLL data.

Originally posted by fudge22 fudge22 wrote:

As Kipman said the technique the rest of us use to reduce variation
between front and back is to position the speakers (usually by flying them) to
reduce the path length variation.


Likewise, Danley Jericho boxes are designed to be flown. Ideally, every show would have speakers flown at an appropriate trim height to ensure even front-to-back coverage. Since pictures speak a thousand words, lets have a bloody goosey gander at some eh?

I whacked a rough audience area into SketchUp and placed meatbags at the typical Near (7m), Mid (30m) and Far (60m) positions that correlate to 'front row megafans', 'FOH lordship' and 'kinda wanna go home' elements of a typical outdoor event crowd. Context is king, so I added a 20m stage mockup from a festival in Wien, pilfered from someone's production design (kindly shared on 3D Warehouse https://3dwarehouse.sketchup.com/model/54b056a6-9da3-4813-b2eb-d3fec0b9accc/20m-Layher-Wien-stage).



In front of this, we have an audience area of 50 metres wide by 60 metres deep. How many punters is that? Well, the UK Green Guide to Safety at Sports Grounds suggests 4.7 people per square metre for a standing audience. That looks a bit like this:
taken from https://www.gkstill.com/Support/crowd-density/CrowdDensity-1.html

So officially, we have room for 3000 people here. 4000 if it's extra rammo because the band is the new hot thing on the tubes.

I like to play fair, so let's start with the industry standard - a system using the big boys' toys to compare against. So 12 a side d&b KSL.


740kg a side. 8x D80 amplifiers and 24 boxes of preemo touring array.

That gives this result:

Note how I've made sure to include the scale and parameters used to generate the plot. 6 dB per colour step, same as the coloured polar maps on the Danley spec sheet. Pink noise stimulus, A-weighted.

Looks like we have 108 dBA SPL average at FOH 30m back, and 102 dBA average for the people behind the mixing tent. Looks good enough for rock and roll to me.

Now let's try a Danley approach. Same pick points, same aim point of just past the farthest pair of ears. First up, and not my first choice, the J8:


218kg and 2x DNA20K amplifiers a side to drive this. The blue mic readout is at the 30m position and it looks like we hit 108 dBA at FOH, 103 dBA at the back here too. What isn't so pretty is the virtual microphone plot on the right - sadly something you can't see easily in ArrayCalc.

However, d&b ArrayProcessing shows you a sampling of evenly spaced virtual mics across the audience plane, on-axis to the array as a before and after kinda thing.

Nice improvements, but the bottom plot would require the customer to pay for another 4x D80 so that each box has it's own amplifier channel pair. For posterity, here's the improvement on the heatmap:


I did my best to match the scales, and placed virtual mics every 5 metres on-axis to a J8 in Danley's Direct to get an equivalent plot for comparison:


No fancy FIR, and still just 2x amps a side.

Now here's a funny thing. I'd pick an even smaller box, J7-95 over the J8 for this gig personally. Less than half the weight & volume, and half the amp channels. That gets us:


Okay we've lost 6 dBA average SPL at FOH, but in reality we probably can't touch those levels during the show anyway due to noise limits. See how the near, mid and far virtual mic curves show less variance than with the J8? That suggests more folks getting more consistent sound than before. Democracy for listeners, I think they call that? Let's check the spaced mic plot for this one:


Add a pinch of PEQ around 3-4 kHz and it looks like we hit nearly as good consistency front-to-back as the fully ArrayProcessed d&b KSL by my eyes. Let's compare some stats & to make it really fun, I'll include a rough cost of the hangs with amps, frames, carts and cables at latest price points:
| System       | Total # Cabs | Total # Drivers | Total Weight | Total # Amps | Max Watts     | Ballpark List Price |
| ------------ | ------------ | --------------- | ------------ | ------------ | ------------- | ------------------- |
| d&b KSL      | 24           | 168             | 1,480kg      | 12           | 192,000       | £500,000            |
| Danley J8-94 | 2            | 92              | 520kg        | 4            | 83,200        | £145,000            |
| Danley J7-95 | 2            | 36              | 300kg        | 2            | 41,600        | £67,500             |


And it looks like this:


Were we talking about efficiencies?

I'd take a J3-94 if I could though, and would love one that has an asymmetrical vertical coverage so that two can be stacked together for one mega horn on bigger gigs. I have ideas in this area but alas, they are just one more thing on my mountain of unfinished projects.

I am concerned about the non-linearity of air at the throat of a horn myself, but also wonder why this hasn't been an issue as yet with all the waveguides squishing sound into cylinders for 20 odd years. Surprisingly little full-fat research into how audible that is just yet, although I saw some promising stuff from a Polish university a couple years back. I might be no spring chicken these days, but after 7 years odd of spanking these things to kingdom come around the planet, I haven't heard particularly unpleasant nastiness of the kind I'd attribute to severe air non-linearity just yet... the neighbours seem to complain before we get anywhere close anyway

On the subject of flying things, it's worth noting that all of the array modelling is built on the basis of there not being a reflective/absorptive ground plane and audience, aka free-field conditions. If you simulate an array that's too low to the ground, it won't behave like the maths suggests. Not only are you pasting the poor bastards in the front row with brute force SPL while the people at the back can barely hear the vocals, you're going to cause more off-site noise issues more quickly like this. Hard to discuss the finer details of this approach on a site when the noise police just need you to STFU before Doris calls the council, of course.

Anyway, back to yer bickering.

Edited by toastyghost - 16 May 2023 at 9:44am
Back to Top
Tedski View Drop Down
Registered User
Registered User


Joined: 15 December 2006
Location: Netherlands
Status: Offline
Points: 402
Post Options Post Options   Thanks (0) Thanks(0)   Quote Tedski Quote  Post ReplyReply Direct Link To This Post Posted: 16 May 2023 at 5:22pm
Excellent post, well done toasty.
Back to Top
kipman725 View Drop Down
Registered User
Registered User


Joined: 02 September 2020
Location: Warrington
Status: Offline
Points: 231
Post Options Post Options   Thanks (0) Thanks(0)   Quote kipman725 Quote  Post ReplyReply Direct Link To This Post Posted: 16 May 2023 at 6:38pm
good work
Back to Top
 Post Reply Post Reply Page  <1234>

Forum Jump Forum Permissions View Drop Down

Forum Software by Web Wiz Forums® version 12.06
Copyright ©2001-2023 Web Wiz Ltd.

This page was generated in 0.094 seconds.