Go Back   Home > Forums > >
Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Planars & Exotics ESL's, planars, and alternative technologies

Horns for ESLs?
Horns for ESLs?
Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 16th April 2018, 10:37 PM   #21
Patrick Bateman is offline Patrick Bateman  United States
diyAudio Member
 
Patrick Bateman's Avatar
 
Join Date: Oct 2006
Location: San Diego
Quote:
Originally Posted by Discopete View Post
Just wondering if this would help beaming issues. I'm thinking an equally spaced, progressively outward angled array of reflectors maybe an inch apart and a few inches wide extending from top to bottom on a typical flat panel such as an Acoustat. Could dispersion be 'tuned' this way by setting the angles just right like window blinds? Logically it seems a better solution than a curved panel since there aren't any/or less phase anomalies.
I've built a lot of horns and waveguides. What you're describing, it sounds like a multicell horn. And multicell horns have quite a few problems, which is why you never see them any more.

There are a couple of ways to control directivity:

1) put a radiator on a waveguide

or

2) Change the shape of the radiator to control the directivity.

For instance, the reason that many planar is curved is because the curvature widens the horizontal directivity. If you wanted to control the vertical and horizontal directivity, you could make the planar convex. (That would be difficult to build)

Another option is to make the planar in rings, which is what Quad does. Basically each ring plays a different frequency band, and the crossover slope and shape can dictated the wavefront shape. This is because crossovers introduce delay, so you can curve the wavefront by having the high frequencies "lead" the midrange and low frequencies. (via the delay introduced in the xover.)
  Reply With Quote
Old 17th April 2018, 05:24 AM   #22
Discopete is online now Discopete  Canada
diyAudio Member
 
Join Date: Nov 2009
Quote:
Originally Posted by Patrick Bateman View Post
I've built a lot of horns and waveguides. What you're describing, it sounds like a multicell horn. And multicell horns have quite a few problems, which is why you never see them any more.

There are a couple of ways to control directivity:

1) put a radiator on a waveguide

or

2) Change the shape of the radiator to control the directivity.

For instance, the reason that many planar is curved is because the curvature widens the horizontal directivity. If you wanted to control the vertical and horizontal directivity, you could make the planar convex. (That would be difficult to build)

Another option is to make the planar in rings, which is what Quad does. Basically each ring plays a different frequency band, and the crossover slope and shape can dictated the wavefront shape. This is because crossovers introduce delay, so you can curve the wavefront by having the high frequencies "lead" the midrange and low frequencies. (via the delay introduced in the xover.)
There's a thread here somewhere about a build in the shape of a dynamic driver cone. I just don't get how curving the radiating surface 'away' from the listening position is an over all solution. With this thinking it would be better to flip dynamic drivers around on the baffle. I have not heard a curved ESL panel but it seems that although a flat paneled one narrows dispersion, it also images better. I think I will conduct an experiment and turn my Monitor 3 around so the outer panels face inward just to see how that differs




l
  Reply With Quote
Old 17th April 2018, 06:32 AM   #23
Patrick Bateman is offline Patrick Bateman  United States
diyAudio Member
 
Patrick Bateman's Avatar
 
Join Date: Oct 2006
Location: San Diego
Quote:
Originally Posted by Discopete View Post
There's a thread here somewhere about a build in the shape of a dynamic driver cone. I just don't get how curving the radiating surface 'away' from the listening position is an over all solution.
Click the image to open in full size.

The shape of the wavefront is defined by the shape of the loudspeaker. If you want a diverging (convex) wavefront, then you want a convex speaker. If you want a converging (concave) wavefront, then you want a concave speaker. If you want a flat wavefront, then you want a flat speaker.

Keep in mind that the curvature can be accomplished by physically curving the speaker, or by curving the speaker electronically. The latter solution is typically what most designers do; in a two-way or three-way speaker it's fairly simply to curve the wavefront using delay.

Quote:
Originally Posted by Discopete View Post
With this thinking it would be better to flip dynamic drivers around on the baffle. I have not heard a curved ESL panel but it seems that although a flat paneled one narrows dispersion, it also images better. I think I will conduct an experiment and turn my Monitor 3 around so the outer panels face inward just to see how that differs
Depends on the wavelength. For instance, 5000Hz is 6.8cm long. So if you're listening to a 2.5cm tweeter, the wavelengths are so long, the tweeter dome imposes no directivity. (Because the wavelengths are longer than the tweeter itself.)

But when we're talking about planars, where the planar is bigger than the wavefront it's playing, the shape of the diaphragm plays a big role.
  Reply With Quote
Old 17th April 2018, 09:27 PM   #24
Discopete is online now Discopete  Canada
diyAudio Member
 
Join Date: Nov 2009
Quote:
Originally Posted by Patrick Bateman View Post
Click the image to open in full size.

The shape of the wavefront is defined by the shape of the loudspeaker. If you want a diverging (convex) wavefront, then you want a convex speaker. If you want a converging (concave) wavefront, then you want a concave speaker. If you want a flat wavefront, then you want a flat speaker.

Keep in mind that the curvature can be accomplished by physically curving the speaker, or by curving the speaker electronically. The latter solution is typically what most designers do; in a two-way or three-way speaker it's fairly simply to curve the wavefront using delay.



Depends on the wavelength. For instance, 5000Hz is 6.8cm long. So if you're listening to a 2.5cm tweeter, the wavelengths are so long, the tweeter dome imposes no directivity. (Because the wavelengths are longer than the tweeter itself.)

But when we're talking about planars, where the planar is bigger than the wavefront it's playing, the shape of the diaphragm plays a big role.
Okay, I'm not quite following you here. If curvature has to do with dispersion, how does delay accomplish this? I understand about time alignment as such which in the case of speakers like B&W 801, or Kef 105, it's accomplished by physically time-aligning the drivers. But what does dispersion have to do with that? I'm referring to your statement about curving the speaker electronically.
  Reply With Quote
Old 20th April 2018, 08:29 PM   #25
bentoronto is offline bentoronto  Canada
diyAudio Member
 
Join Date: Jan 2008
Location: Toronto and Delray Beach, FL
Horns for ESLs?
Quote:
Originally Posted by Discopete View Post
Okay, I'm not quite following you here. If curvature has to do with dispersion, how does delay accomplish this?
I think it's like Doppler and train horns.

B.
__________________
HiFi aspirations since 1957. Currently working on motional feedback again... the final frontier in audio (also, see recent post with data on a 17-foot labyrinth sub)
  Reply With Quote
Old 21st April 2018, 07:31 PM   #26
Patrick Bateman is offline Patrick Bateman  United States
diyAudio Member
 
Patrick Bateman's Avatar
 
Join Date: Oct 2006
Location: San Diego
Quote:
Originally Posted by Discopete View Post
Okay, I'm not quite following you here. If curvature has to do with dispersion, how does delay accomplish this? I understand about time alignment as such which in the case of speakers like B&W 801, or Kef 105, it's accomplished by physically time-aligning the drivers. But what does dispersion have to do with that? I'm referring to your statement about curving the speaker electronically.
You can physically curve a loudspeaker to get a specific wavefront, or you can electronically curve it.

Horns for ESLs?

For instance, this Martin Logan is curved horizontally so that the beamwidth is somewhere around 45 degrees. If the panel was flat, the beamwidth would be zero degrees, and then it would have an exceptionally narrow sweet spot.

With a loudspeaker array, you can curve the wavefront electronically using delay. This requires a LOT of DSP and amplification channels, but it's routinely done for prosound apps. As amplification and DSP gets cheaper you'll start to see it done at home. The Beolab 90 has something like 30 channels of DSP and amplification and it can vary it's beamwidth electronically.

As for the actuall practive of beamforming, it's exactly what you think it is; you change the wavefront with delay. For instance, an array that is physically flat can be electronically curved by progressively delaying the elements on the top and the bottom. You can also curve an array asymmetrically, for instance you can make the wavefront point UP or DOWN.
  Reply With Quote
Old 21st April 2018, 09:04 PM   #27
golfnut is offline golfnut  New Zealand
diyAudio Member
 
golfnut's Avatar
 
Join Date: Jul 2010
Location: Lower Hutt, NZ
Hi

The electronic constructions and techniques used for controlling dispersion are collectively known as phased arrays (see wikipedia).

Yes, the most sophisticated versions do require a lot of DSP, however there are two cases where very useful improvements in the dispersion characteristics of ESLs can be achieved with passive networks.

The Quad ESL 63 and subsequent models uses an array of circular/annular segments in a flat ESL panel. Each segment behaves electrically like a capacitor (C), and is coupled to its neighbour with an inductor (L) to form an LC transmission line. This has the effect of introducing a small delay between the acoustic radiations from each segment. This is used to construct an acoustic radiation pattern that looks as though it comes from a point source - expanding spherical wavefronts. In theory, with an infinite number of such segments, it would yield a perfect 360 degree dipole dispersion - i.e. a perfect figure 8 polar response ay all frequencies. In practice, the inductors have to be quite large so Quad use only 7 segments, so the polar response is not perfect - but is a substantial improvement. Have a look at the polar plots in the Quad ESL datasheets.

The second possibility is the segmented line source in which a tall (ideally floor-to-ceiling) ESL panel is segmented as a couple of dozen vertical strips all coupled to neighbouring strips by resistors. When driven at the centre strip, this yields a cylindrical wavefront and a dispersion pattern that is near perfect up to frequencies of a couple of kilohertz, and very smooth roll-off at frequencies above that giving a perfect listening zone about 20 degrees wide (instead of 1 degree wide). Quite a number of DIYers have built them here - it is very simple compared to the quad solution and makes a very nice loudspeaker. See
Another segmented ESL . There is also an Excel spreadsheet around here to help.

Hopefully others here who collect the links can tell you were to find other links on this design.

Curved ESLs, like the martin logins, are a partial solution the the dispersion problem - they make a useful improvement to the dispersion but at the expense of audible distortion due to the asymmetry between forward and backward movements of the membrane. Still sound better than conventional speaker though
__________________
“Nothing is more practical than a good theory.”
– Ludwig Boltzmann
  Reply With Quote
Old 21st April 2018, 11:29 PM   #28
Discopete is online now Discopete  Canada
diyAudio Member
 
Join Date: Nov 2009
As I've already mentioned, dispersion with my Monitor 3 Acoustats is not a problem...at the listening position. I would not want to compromise what they do well. I sit 12' away, they are 8' apart, 4' to the front wall, 4' to the back, toed in to my ears....exactly to the millimeter. Placement geometry is perfect. I found that precise placement yields a sweet spot comparable to any other speaker I've heard. There's no head in a vice issue. But when I get up and walk away, that fabulous linearity is gone.
  Reply With Quote
Old 23rd April 2018, 10:55 PM   #29
bolserst is offline bolserst  United States
diyAudio Member
 
bolserst's Avatar
 
Join Date: Jun 2005
Location: Fort Worth, Texas
Quote:
Originally Posted by Discopete View Post
As I've already mentioned, dispersion with my Monitor 3 Acoustats is not a problem...at the listening position…But when I get up and walk away, that fabulous linearity is gone.
This is a power response problem; total acoustic energy radiated into the room has significantly different spectral balance than acoustic response at listening position. The designs with more uniform dispersion characteristics that golfnut mentioned would solve your problem. But, it sounds like you are happy with your current speakers and just looking for a way to improve things outside the listening area.

Is it more the “getting up” or the “walking away” that kills the spectral balance?
The Monitor3s are short speakers with essentially zero dispersion of highs in the vertical direction. It is possible that simply tipping the speakers back an additional 10 degrees or so might improve things to your liking when you are not in the sweet spot.

Martin Logan and JansZen both addressed this issue on their designs with shorter panels by adding a dome tweeter that can be adjusted as needed for HF ambience. ML calls this feature “NAC” (Natural Ambience Compensation)...JansZen settled on the slightly less descriptive name “Airlayer”. In either case, the goal is to add back some of the mids and highs that are missing from the room response for non-critical listening (aka party mode) or listening from another room (aka kitchen mode). You may even find, as several reviewers did, that it improves your experience in the listening area as well.
  Reply With Quote
Old 24th April 2018, 01:56 AM   #30
Discopete is online now Discopete  Canada
diyAudio Member
 
Join Date: Nov 2009
Quote:
Originally Posted by bolserst View Post
This is a power response problem; total acoustic energy radiated into the room has significantly different spectral balance than acoustic response at listening position. The designs with more uniform dispersion characteristics that golfnut mentioned would solve your problem. But, it sounds like you are happy with your current speakers and just looking for a way to improve things outside the listening area.

Is it more the “getting up” or the “walking away” that kills the spectral balance?
The Monitor3s are short speakers with essentially zero dispersion of highs in the vertical direction. It is possible that simply tipping the speakers back an additional 10 degrees or so might improve things to your liking when you are not in the sweet spot.

Martin Logan and JansZen both addressed this issue on their designs with shorter panels by adding a dome tweeter that can be adjusted as needed for HF ambience. ML calls this feature “NAC” (Natural Ambience Compensation)...JansZen settled on the slightly less descriptive name “Airlayer”. In either case, the goal is to add back some of the mids and highs that are missing from the room response for non-critical listening (aka party mode) or listening from another room (aka kitchen mode). You may even find, as several reviewers did, that it improves your experience in the listening area as well.
I have them leaning back 3deg. right now which is perpendicular to my ears at 12 ft away. They sound perfect like that. However I do have the HF adjustment up a notch on the OTLs, I'm 61 If I stand up, there's not much difference. It's when I'm no longer directly in front of them that things fall apart. Depth perspective of HF is superb which I take it is attributable to the ESL's resolution. I would definitely not want to change that. I just want to hear the same thing when I'm over in the kitchen. I guess I can't have everything, eh? Mind you I'm not complaining. If I turn them up LOUD, there's no lack of anything anywhere.
  Reply With Quote

Reply


Horns for ESLs?Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Domes on Horns vs Compression Drivers on Horns Patrick Bateman Multi-Way 75 29th November 2017 06:02 AM
smith horns and using compression horns for a Karlson party speaker project bikehorn Multi-Way 14 30th January 2013 06:20 PM
[ Group horns buy from hORNS - join for free shipping and 10% off ] gregdee Group Buys 0 28th October 2012 02:21 PM
Horns inside of horns open foe discussion oilcanracer Multi-Way 3 15th February 2010 04:42 AM
Horns: Vibrations and resonances in metal horns Rocky Multi-Way 10 28th July 2004 02:38 AM


New To Site? Need Help?

All times are GMT. The time now is 08:44 PM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 14.29%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Copyright ©1999-2018 diyAudio
Wiki