GM said:
Ok I think I've managed to confuse myself!
I've been thinking about this today and I think I was assuming the air in front of the horn to be moving as a 'slab', and totally forgot about its off axis performance.
Interesting as I want to eventually use a stack of 6 labhorns for my stereo - I'm guessing I'll have similar problems crossing them at 80Hz?
Thats why I twice put in a caveat that I'm not great at horn theory btw. - still learning.
Another option could be to go 48dB/oct on the xo ?
Rob.
i do not understand how off-axis performance would be an issue when using waveguides between all drivers?
i also believed that it would behave as a "plate" up to a certain fredquency ...
soo much i do not understand,
GM: maybe you have given me all maths and theory for the planar wave, but it is very hard for me to even discern it and comprehend what it implies and how to use them ...
i also believed that it would behave as a "plate" up to a certain fredquency ...
soo much i do not understand,
GM: maybe you have given me all maths and theory for the planar wave, but it is very hard for me to even discern it and comprehend what it implies and how to use them ...
Understood, I can better try to enlighten if I understand where you're coming from, hence my 'challenge' Q. That, and I'm usually bone tired when I'm reading/responding, so sometimes folks can be correct, but the way they present it appears totally wrong to me at the time, so all I can do is ask for a clarification and give my thoughts.
Anyway, it will be ~planar over some BW defined by whatever the horn's wall angle is at that frequency and since this point is moving towards the throat with increasing frequency and as Tom has noted many times, if the horn isn't expanding fast enough beyond this point it will cause the beam to tighten up even more, so even with a properly designed horn or WG its off axis response will typically be far worse than a point source's.
Yes, anything that gets the output down low enough that you don't notice the collapse of the sound wall (the actual wall all the drivers are mounted on) into audibly distinct points centered at each driver and along its perimeter. This point is considered to be at least -25 dB and ideally > -35 dB and I assume why some famous designer (I forget who) said something to the effect that high fidelity begins at -40 dB.
Anyway, stacking that many Labhorns will in theory shift its usable BW much lower in a typical HIFI/HT app by however much its effective mouth area is and the driver's spacing. In a prosound app the crowd is going to be far enough away that it will appear as one huge wide BW device, but up close its line array spacing will lower its usable high SQ XO point, though as I told Jim I don't know how much you can 'cheat' theory due to all the usual room, etc., caveats. All I know for sure is that when I've tried to with various line and ~planar array experiments it's been like a poorly implemented 901 set-up in that at first the almost live sound-staging overloads the senses that are used to typical speakers and even horns in some cases, but in each case where I veered much from theory the 'honeymoon' was soon over and like with too many personal relationships, 'familiarity breeds contempt' as the little irritating things chipped away at it and I found reasons to increasingly limit critical listening time until finally they had to go.
In a similar vein, FWIW ever since I auditioned TD's three way Unity even a typical high SQ 'full range' driver speaker sounds too phase incoherent for critical listening to suit me
Anyway, it will be ~planar over some BW defined by whatever the horn's wall angle is at that frequency and since this point is moving towards the throat with increasing frequency and as Tom has noted many times, if the horn isn't expanding fast enough beyond this point it will cause the beam to tighten up even more, so even with a properly designed horn or WG its off axis response will typically be far worse than a point source's.
Yes, anything that gets the output down low enough that you don't notice the collapse of the sound wall (the actual wall all the drivers are mounted on) into audibly distinct points centered at each driver and along its perimeter. This point is considered to be at least -25 dB and ideally > -35 dB and I assume why some famous designer (I forget who) said something to the effect that high fidelity begins at -40 dB.
Anyway, stacking that many Labhorns will in theory shift its usable BW much lower in a typical HIFI/HT app by however much its effective mouth area is and the driver's spacing. In a prosound app the crowd is going to be far enough away that it will appear as one huge wide BW device, but up close its line array spacing will lower its usable high SQ XO point, though as I told Jim I don't know how much you can 'cheat' theory due to all the usual room, etc., caveats. All I know for sure is that when I've tried to with various line and ~planar array experiments it's been like a poorly implemented 901 set-up in that at first the almost live sound-staging overloads the senses that are used to typical speakers and even horns in some cases, but in each case where I veered much from theory the 'honeymoon' was soon over and like with too many personal relationships, 'familiarity breeds contempt' as the little irritating things chipped away at it and I found reasons to increasingly limit critical listening time until finally they had to go.
In a similar vein, FWIW ever since I auditioned TD's three way Unity even a typical high SQ 'full range' driver speaker sounds too phase incoherent for critical listening to suit me
it is not easy for me to follow up on what i want to build,
i have many ideas, but most proove to be wrong
because of accoustic laws that i do not know
or understand properly
my idea started with 2 very big sub bass horns
then moved to IB because of the quality of sound IB
yields , then to trying to reduce room modes to have some kind of effect, wich i ain't not even sure is possible to achieve ( planar wave front )
i do not wish to make anyone loose his time on me,
but if no one helps me understand, or teach or direct me to some readings, i will never be able to grow in my knowledge and understanding of accoustics
and its applications to what we all share ...
i have many ideas, but most proove to be wrong
because of accoustic laws that i do not know
or understand properly
my idea started with 2 very big sub bass horns
then moved to IB because of the quality of sound IB
yields , then to trying to reduce room modes to have some kind of effect, wich i ain't not even sure is possible to achieve ( planar wave front )
i do not wish to make anyone loose his time on me,
but if no one helps me understand, or teach or direct me to some readings, i will never be able to grow in my knowledge and understanding of accoustics
and its applications to what we all share ...
I don't mean to be rude, but your ignorance of the subjects required for you to understand my very basic answers to questions to help you realize your audio related projects doesn't constitute a problem at my end of these conversations. Not to single you out specifically since you at least seem willing to learn, but I've pretty much had my fill of folks trying to make me and a few others the 'bad guy' when our answers aren't dumbed down to the lowest common denominator of the knowledge base of the folks that inhabit many of these forums. I wish I had the ability like Tom Danley, MJK and a few others, but apparently I just don't process info the same way they do. That, and I expect folks who ask me for advice/info on advanced subjects I spent considerable time/$$ learning to at least pay me the courtesy of learning the associated 'lingo' and doing a bit of research if need be to understand it just as others expect it of me when I go outside my 'comfort zone' of knowledge.
That said, I just now noticed that English probably isn't your primary language, so anything technically oriented will be more of a challenge all by itself, ergo instead of me probably wasting any more of our time trying to answer your other questions, go through these websites and learn about acoustics in general and decibels in particular and try to find someone technically oriented in your native tongue to help you through the more baffling points (which for me were legion unfortunately due to lack of higher math skills) and if it's English, then post your questions on the Loudspeaker forum where you're likely to get the correct answer quickest:
http://www.engineeringtoolbox.com/acoustics-noise-decibels-t_27.html
http://www.silcom.com/~aludwig/
http://hyperphysics.phy-astr.gsu.edu/hbase/sound/soucon.html#soucon
http://www.acoustics.org/faqs.html
BTW, my previous response was primarily addressing Rob's post, though of course relevant to some of your questions too.
That said, I just now noticed that English probably isn't your primary language, so anything technically oriented will be more of a challenge all by itself, ergo instead of me probably wasting any more of our time trying to answer your other questions, go through these websites and learn about acoustics in general and decibels in particular and try to find someone technically oriented in your native tongue to help you through the more baffling points (which for me were legion unfortunately due to lack of higher math skills) and if it's English, then post your questions on the Loudspeaker forum where you're likely to get the correct answer quickest:
http://www.engineeringtoolbox.com/acoustics-noise-decibels-t_27.html
http://www.silcom.com/~aludwig/
http://hyperphysics.phy-astr.gsu.edu/hbase/sound/soucon.html#soucon
http://www.acoustics.org/faqs.html
BTW, my previous response was primarily addressing Rob's post, though of course relevant to some of your questions too.
I'll work on that Teacher 
and of course english is not my primary language,
but i do understand 99%+ of it.. i just don't have the same ability to type or speak than to read/listen
i'll try and go through my books and all other accoustic basic stuff again before i continue on this quest
but i'll take 1 more question before going back to basics..
is my quest for the planar wave and lots of IB drivers
for my sub-bass of my HT setup worth it ?
is this something that we could call a very good compromise/setup ?
cause if it is not, i will not pursue further than for my basic understanding ...
the more i read this thread, the more i learn though
and of course english is not my primary language,
but i do understand 99%+ of it.. i just don't have the same ability to type or speak than to read/listen
i'll try and go through my books and all other accoustic basic stuff again before i continue on this quest
but i'll take 1 more question before going back to basics..
is my quest for the planar wave and lots of IB drivers
for my sub-bass of my HT setup worth it ?
is this something that we could call a very good compromise/setup ?
cause if it is not, i will not pursue further than for my basic understanding ...
the more i read this thread, the more i learn though
i work very very hard for every pennie i put aside for my house project ...and the better i plan and understand all of this, the better will my hard earned money be invest on all the compromises we have to choose from
"Is the Pope Catholic?"
that' doesn't mean anything to me...sorry to let you down on that one
"'close enough' to having a 77+ ft sub-bass horn attached to the end of your room"
now that is more like what i want to hear
now i'll get to working on my understanding of accoustics before asking anymore silly questions
and i'll probably post some quick sketch soon for you to see if it matches what we have discussed here!
thanks again
"Is the Pope Catholic?"
that' doesn't mean anything to me...sorry to let you down on that one
"'close enough' to having a 77+ ft sub-bass horn attached to the end of your room"
now that is more like what i want to hear
now i'll get to working on my understanding of accoustics before asking anymore silly questions
and i'll probably post some quick sketch soon for you to see if it matches what we have discussed here!
thanks again
JinMTVT said:
"Is the Pope Catholic?"
that' doesn't mean anything to me...sorry to let you down on that one
thanks again
You're welcome!
Interesting, I figured your locale would be predominantly Catholic. Anyway, it's just one of a number of humorous phrases we use to say 'most definitely', etc.:
http://www.urbandictionary.com/define.php?term=is+the+pope+catholic?
just as a continuum while i work on my accoustics...
i guess that there is a rate at wich sound takes expension as with the db and inverse square law ..etc..
What is the curve or angle i would have to respect using those waveguides to be able to not loose regular expension ? square expo curve?
i guess that there is a rate at wich sound takes expension as with the db and inverse square law ..etc..
What is the curve or angle i would have to respect using those waveguides to be able to not loose regular expension ? square expo curve?
is there a volumic expansion curve that we need to restrain horn's mouth or wave guides so that
there is a correct density vs displacement of sound waves at the output of the system ?
example, if i'd have a 10 foot long horn
that gets tooo big tooo fast, would it be bad?
you talked earlier of dispertion at the "end" of the waveguides wich would be a problem
so it must be because there is a maximum expension formula that must be used?
i'll draw it tomorrow
there is a correct density vs displacement of sound waves at the output of the system ?
example, if i'd have a 10 foot long horn
that gets tooo big tooo fast, would it be bad?
you talked earlier of dispertion at the "end" of the waveguides wich would be a problem
so it must be because there is a maximum expension formula that must be used?
i'll draw it tomorrow
how does a wave spreads form the surface of the drivers ???
lets assume a round regular woofer type
what is the actualy shape of the wave when it is created at the edge of the driver?
i'd guess that the coutours are round shaped following the cone of the driver, but the forward/back distribution is the part where i have no clear idea ...
i assume that since the edges of the cone driver are more forward than its center, the sides of the waves would be pushed forward earlier than the center,
so does the actual shape of the wave follows the cone of the driver with its inward center ??
Then, a wave that is created from a cone driver,
has a specific volume/area ?
can a waveguide be specifically made so that the wave
flattens out as it moves forward ? ( using waveguide countour shape .. )
there must be a mathematical formula to find that out ,
but since i am a big zero in advanced maths ...
if i could get the waves of my multi woofer setup,
to flatten out right where all the waveguides would merge into open space, assuming that the volume of the wave guides follows quite nicely the inverse square law for the area of spread of the waves,
would this make a nice plane wave radiation ?
do planar drivers produce completly flat waves right in front of them at the exit ( before spreading ) ??
like a big electrostatic pannel maybe ...
still need to read alot on accoustics ..
that was just a quick thought
lets assume a round regular woofer type
what is the actualy shape of the wave when it is created at the edge of the driver?
i'd guess that the coutours are round shaped following the cone of the driver, but the forward/back distribution is the part where i have no clear idea ...
i assume that since the edges of the cone driver are more forward than its center, the sides of the waves would be pushed forward earlier than the center,
so does the actual shape of the wave follows the cone of the driver with its inward center ??
Then, a wave that is created from a cone driver,
has a specific volume/area ?
can a waveguide be specifically made so that the wave
flattens out as it moves forward ? ( using waveguide countour shape .. )
there must be a mathematical formula to find that out ,
but since i am a big zero in advanced maths ...
if i could get the waves of my multi woofer setup,
to flatten out right where all the waveguides would merge into open space, assuming that the volume of the wave guides follows quite nicely the inverse square law for the area of spread of the waves,
would this make a nice plane wave radiation ?
do planar drivers produce completly flat waves right in front of them at the exit ( before spreading ) ??
like a big electrostatic pannel maybe ...
still need to read alot on accoustics ..
that was just a quick thought
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