Hi tmc
I can't find any refs or websites that give any details as to design of accoustic lenses, I suspect that most of this is proprietry information to the manufacturer, as high end pro audio is a cut throat business. You might want to try patent searches, that might give you some ideas.
However, most accoustic lenses are used to narrow the dispersion of a driver, and as such, have limited uses in a domestic enviroment, where the main intention is to create as wide a sound field as possible.
I also have a sneaking suspicion that some of these beam shaping devices are not really much use, just added by the marketing dept. so their system looks trendy...
I can't find any refs or websites that give any details as to design of accoustic lenses, I suspect that most of this is proprietry information to the manufacturer, as high end pro audio is a cut throat business. You might want to try patent searches, that might give you some ideas.
However, most accoustic lenses are used to narrow the dispersion of a driver, and as such, have limited uses in a domestic enviroment, where the main intention is to create as wide a sound field as possible.
I also have a sneaking suspicion that some of these beam shaping devices are not really much use, just added by the marketing dept. so their system looks trendy...
It is true that an acoustic lens is a design compromise in the design of the horn to provide for a "controlled" dispersion. Some lenses, such as the McCauley's 451?, have a very wide dispersion pattern, while the JBL L91's are only 40X90 degrees. The operative word here is "controlled".
(Not be able to get into the math) In general the slant plate type lens makes select portions of the expanding pressure wave travel farther then other portions of the pressure wave. This tends to "shape" the pressure wave as it is still expanding thereby controlling the dispersion.
Here are two links that may or may not be helpful. One is to JBL's old horn brochure, and the other is a series of references from Tom Dunkers Horn Page http://invalid.ed.unit.no/~dunker/horns.html
http://www.jblpro.com/pub/obsolete/Acoustic_Lens_Family1.pdf
http://invalid.ed.unit.no/~dunker/refs01.html
Hope it helps,
Rodd Yamashita
(Not be able to get into the math) In general the slant plate type lens makes select portions of the expanding pressure wave travel farther then other portions of the pressure wave. This tends to "shape" the pressure wave as it is still expanding thereby controlling the dispersion.
Here are two links that may or may not be helpful. One is to JBL's old horn brochure, and the other is a series of references from Tom Dunkers Horn Page http://invalid.ed.unit.no/~dunker/horns.html
http://www.jblpro.com/pub/obsolete/Acoustic_Lens_Family1.pdf
http://invalid.ed.unit.no/~dunker/refs01.html
Hope it helps,
Rodd Yamashita
NOT IMPRESSED.
Hi,
First of all,the way they work has got nothing to do with optics.
It's called a lens for some (marketing) reason but that's about it.
To my ears this add-on blocks more high frequencies than it actually diperses.
We all know that high frequencies tend to bundle with rising frequency but that lense has never inpressed me.
I tried it about twenty years ago on my Klipshorn clones (with a JBL horn tweeter) and abandoned it.
Strange as it may seem the better the electronics (tube amps) the less the directivity of the speakers bothered me.
Same experience with the Quad ESLs,funny but true.
Maybe these can be of use in P.A. or discos but for audio?
I doubt it.
Cheers,
Hi,
First of all,the way they work has got nothing to do with optics.
It's called a lens for some (marketing) reason but that's about it.
To my ears this add-on blocks more high frequencies than it actually diperses.
We all know that high frequencies tend to bundle with rising frequency but that lense has never inpressed me.
I tried it about twenty years ago on my Klipshorn clones (with a JBL horn tweeter) and abandoned it.
Strange as it may seem the better the electronics (tube amps) the less the directivity of the speakers bothered me.
Same experience with the Quad ESLs,funny but true.
Maybe these can be of use in P.A. or discos but for audio?
I doubt it.
Cheers,
Re: NOT IMPRESSED.
Frank,
Certainly, the use of the term “optics” is an analogy, rough as it may be.
WRT the sound, I’ve used a pair of JBL horn for my upper mid-range for more then 20 years. They can sound bad if implemented without the care an average audiophile gives to any other part of their system. Unfortunately, this has been too often the case. Early experiences and preconceived ideas have often been ingrained into our way of thinking toward horns until, in general, we figure they can never sound much better then they did in the 70’s being powers by one of the early SS amps.
It is true that of the many amps I’ve used to drive my horns (tubes and SS) only 3 were able to make the “horn” sound disappear, but all you need is one. Is it easier to get cones and domes to sound smoother?… Yes. Is it easier to make ribbons or ‘stats to sound more detailed?… Arguably yes. Is it impossible to make horns sound smooth, and detailed, with ambience and depth, and retain the dynamics and impact horns are known for?… No, it’s not impossible, I’ve been there.
WRT horn lenses. These are just used as dispersion controllers. The result of which can have better wide-band results then many cone speakers. Frequencies as high as 10kHz still have wavelengths >30mm, which will be fully affected by the acoustic lens. The lens will have a more predicable affect on the dispersion of the waveform then a 50mm cone speaker running on the edge cone breakup. This is not to say it is better or worse; it’s different, so should be treated differently.
Ranting done for now,
Rodd Yamashita
fdegrove said:First of all,the way they work has got nothing to do with optics.
It's called a lens for some (marketing) reason but that's about it....
Strange as it may seem the better the electronics (tube amps) the less the directivity of the speakers bothered me.
Same experience with the Quad ESLs,funny but true.
Maybe these can be of use in P.A. or discos but for audio?
I doubt it.
Cheers,
Frank,
Certainly, the use of the term “optics” is an analogy, rough as it may be.
WRT the sound, I’ve used a pair of JBL horn for my upper mid-range for more then 20 years. They can sound bad if implemented without the care an average audiophile gives to any other part of their system. Unfortunately, this has been too often the case. Early experiences and preconceived ideas have often been ingrained into our way of thinking toward horns until, in general, we figure they can never sound much better then they did in the 70’s being powers by one of the early SS amps.
It is true that of the many amps I’ve used to drive my horns (tubes and SS) only 3 were able to make the “horn” sound disappear, but all you need is one. Is it easier to get cones and domes to sound smoother?… Yes. Is it easier to make ribbons or ‘stats to sound more detailed?… Arguably yes. Is it impossible to make horns sound smooth, and detailed, with ambience and depth, and retain the dynamics and impact horns are known for?… No, it’s not impossible, I’ve been there.
WRT horn lenses. These are just used as dispersion controllers. The result of which can have better wide-band results then many cone speakers. Frequencies as high as 10kHz still have wavelengths >30mm, which will be fully affected by the acoustic lens. The lens will have a more predicable affect on the dispersion of the waveform then a 50mm cone speaker running on the edge cone breakup. This is not to say it is better or worse; it’s different, so should be treated differently.
Ranting done for now,
Rodd Yamashita
Nexo have been using wavefront shaping and lens type technologies in their new Geo line array.
http://www.nexo-sa.com/_geo/GEOhom.html
It all looks good on paper, although I've heard mixed reviews from people who've actually heard it.
http://www.nexo-sa.com/_geo/GEOhom.html
It all looks good on paper, although I've heard mixed reviews from people who've actually heard it.
HeyTMC,
Please check out this site, there is plenty of helpful members on the Lansing Forum who I am sure will assist.
For my part I have used JBL 2307/2308 with the slant plate lense and the new bi radial devices like the 2344a.
The lense acts as a diffraction device, diffracting the sound from the mouth of the horn and bending the direction of the sound waves, the profile of the lense allows a contour of the dispersion desired.
The power response of these devices is not linear off axis but they have a flat amplitude response on axis.
The bi radial horn has however a linear power response off axis but requires some equ above 3khz for a flat on axis response by design.
The image below is my current JBL monitor using both cone and bi radial horn technology, the horn sound is not all all obvious, in fact the response is very smooth and imaging is outstanding.
If you want to chat more about this topic send me an email
cheers
Ian
http://www.audioheritage.org/
http://www.audioheritage.org/
Please check out this site, there is plenty of helpful members on the Lansing Forum who I am sure will assist.
For my part I have used JBL 2307/2308 with the slant plate lense and the new bi radial devices like the 2344a.
The lense acts as a diffraction device, diffracting the sound from the mouth of the horn and bending the direction of the sound waves, the profile of the lense allows a contour of the dispersion desired.
The power response of these devices is not linear off axis but they have a flat amplitude response on axis.
The bi radial horn has however a linear power response off axis but requires some equ above 3khz for a flat on axis response by design.
The image below is my current JBL monitor using both cone and bi radial horn technology, the horn sound is not all all obvious, in fact the response is very smooth and imaging is outstanding.
If you want to chat more about this topic send me an email
cheers
Ian
http://www.audioheritage.org/
http://www.audioheritage.org/
Attachments
thanx for the response ya'll
1. control of the dispersion pattern is my goal. i am not looking
to build a pair of "transparent cabs" i want to limit and focus
for stage/recording application.....as we all know,control is
vital in these situations, until you get to the mixdownstage.
THEN you need transparent moniters
2. "LAW OF REFLECTION
the angle of Incedence and the angle of Reflection are equal
for all wavelengths and for any pair of media"
the above statement was taken from a standard physics book,
from the chapter dealing with geometric optics ( a branch of
optics which represents waves in terms of rays)
3. Not tryin to start a war here, but! P.A. is Audio, just another
part of a wide,wide field.
thanx for the pointers....
1. control of the dispersion pattern is my goal. i am not looking
to build a pair of "transparent cabs" i want to limit and focus
for stage/recording application.....as we all know,control is
vital in these situations, until you get to the mixdownstage.
THEN you need transparent moniters
2. "LAW OF REFLECTION
the angle of Incedence and the angle of Reflection are equal
for all wavelengths and for any pair of media"
the above statement was taken from a standard physics book,
from the chapter dealing with geometric optics ( a branch of
optics which represents waves in terms of rays)
3. Not tryin to start a war here, but! P.A. is Audio, just another
part of a wide,wide field.
thanx for the pointers....
Ah I see your idea,
You are looking for A WAVE GUIDE with a controlled and well defined tight dispersion pattern.
Have a look at the JBL bia radials and others either from the jbjl site jblpro.com or the Herritage site in the library, the application notes will advise of your application,
cheers
macka
You are looking for A WAVE GUIDE with a controlled and well defined tight dispersion pattern.
Have a look at the JBL bia radials and others either from the jbjl site jblpro.com or the Herritage site in the library, the application notes will advise of your application,
cheers
macka
pinkmouse
actually, what i'm going after is something that could be used for F.O.H. in a smaller bar situation, or on a decent theatre stage, a good side fill/keyboard enclousure ( sometimes line signals just don't cut it)
Makka and roddyama
The jbl/lansing refs were of imediate help and thanx to ya'll for the quick replies and opinions
it should prove intresting and hopefully usefull when these thangs are done
actually, what i'm going after is something that could be used for F.O.H. in a smaller bar situation, or on a decent theatre stage, a good side fill/keyboard enclousure ( sometimes line signals just don't cut it)
Makka and roddyama
The jbl/lansing refs were of imediate help and thanx to ya'll for the quick replies and opinions
it should prove intresting and hopefully usefull when these thangs are done
just wanted to add this,
I am extremely intrested in anything that cuts out the broad assumption that anything to do with playing live music ( or just listening) has to be done by brute force.
i'm not saying i don't enjoy high volume ( c'mon , i got 2 100w combo amps in my guitar rig!!), i do....just can't stand the ineffiecient use of amplification....thus my intrest in horns and lenses.
Sometimes wider is not better.
I am extremely intrested in anything that cuts out the broad assumption that anything to do with playing live music ( or just listening) has to be done by brute force.
i'm not saying i don't enjoy high volume ( c'mon , i got 2 100w combo amps in my guitar rig!!), i do....just can't stand the ineffiecient use of amplification....thus my intrest in horns and lenses.
Sometimes wider is not better.
I remembered this pic in one my books.
The translated text suggests that the working is based on a delayed signal off-axis versus not delayed when on-axis response. The proposed lens should thus perform more dispersion on a narrowed soundfield at high frequencies.
A long time ago it was quite trendy ( ~1983 ?) to have them on (cheap) loudspeaker boxes like "Jamo" in The Netherlands.
The translated text suggests that the working is based on a delayed signal off-axis versus not delayed when on-axis response. The proposed lens should thus perform more dispersion on a narrowed soundfield at high frequencies.
A long time ago it was quite trendy ( ~1983 ?) to have them on (cheap) loudspeaker boxes like "Jamo" in The Netherlands.
Attachments
GOOD THING WE'RE NOT INC.
Hi,
And they are the exact same thing I complained about,eating tweeter output and details.
Naturally,for TMCs' application it may not matter that much.
I think Isophon had a horn tweeter using something simailar as well.
Also on most JBL designs you had a level control to balance for a loss in output on a unit.
It may be more effective in far field monitoring but in room I didn't really hear the benefit of susch a lense.
My
Hi,
And they are the exact same thing I complained about,eating tweeter output and details.
Naturally,for TMCs' application it may not matter that much.
I think Isophon had a horn tweeter using something simailar as well.
Also on most JBL designs you had a level control to balance for a loss in output on a unit.
It may be more effective in far field monitoring but in room I didn't really hear the benefit of susch a lense.
My
tmc,
To be honest, I think you are over complicating things by thinking about acoustic lenses, what you really need is a good efficient 12" and horn tweeter box. I would give you a link, but I have just upgraded my OS, and have not transferred all my links across yet, but do a google search and you should find many references.
What you really need is not cutting edge technology, but a box that will be robust, have good power handling, and is lightweight, take my word for it, at the end of the gig, sound quality comes a distant second to how easy it is to carry down the stairs and put in the van.
To be honest, I think you are over complicating things by thinking about acoustic lenses, what you really need is a good efficient 12" and horn tweeter box. I would give you a link, but I have just upgraded my OS, and have not transferred all my links across yet, but do a google search and you should find many references.
What you really need is not cutting edge technology, but a box that will be robust, have good power handling, and is lightweight, take my word for it, at the end of the gig, sound quality comes a distant second to how easy it is to carry down the stairs and put in the van.
a good point.
And one i know well as i have carried my share of rigs,amps inst. etc, etc. up,down,around,on and under just about every immaginable enviroment over the last 20 years.
Call it self indulgent,call it excessive.... fair enough.
I've got some spare time and material and want to play around with some ideas.....
not out to slam ya pinkmouse....but I am pretty sure about what i'm after.
thanx for your input
and for watching out for my back!!!!!!!!!!!
And one i know well as i have carried my share of rigs,amps inst. etc, etc. up,down,around,on and under just about every immaginable enviroment over the last 20 years.
Call it self indulgent,call it excessive.... fair enough.
I've got some spare time and material and want to play around with some ideas.....
not out to slam ya pinkmouse....but I am pretty sure about what i'm after.
thanx for your input
and for watching out for my back!!!!!!!!!!!
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