# bang and olufsen tweeter lens idea



## req

So i do not know what the mathmatics involved in this are - its something to do with a parabola and the focus point of the sound, im assuming it has to do with the disatnace from the diaphram of the tweeter to the focal point of the parabola to meet the inverse arc - and all that has to do with the diameter of the diaphram and such.

but getting some of these made would be sweet - but the cost of the part would be astronomical. building a pair of these in any sort of accuracy would be next to impossible without precision machine tools too.

but i really like the way that they are going with this design and i think it is extremly fitting for the enviornment of the car audio world.

patrick? any comments? mic wallace?

i just threw this design together using the vifa NE19VTS-04 3\4" silk dome tweeter as a base for dimensioning purposes. im sure there are other tweeters that could benefit, and it would be very easy to integrate into may cars - depending on the depth of the tweeter to be used.

i just cant figure out how these could be made for any acceptable cost, even if they were made in large batches.


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## IBcivic

This comes to mind 
3D Printer - YouTube


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## jowens500

I actually have an Audi A8L W12 with the B&O system in the shop right now.

















Rear tweeter.


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## Niebur3

What would be cool is to even make something life that out of MDF and fiberglass and use it to snap on over the tweeter for critical listening sessions or competition, even if it is not for everyday use.


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## Eric Stevens

Not hard or expensive. 

A simple silicone mold made off of a master and you can cast them out of epoxy or urethane.

You could hand form the master or use SLA or 3D printer as mentioned above.

Eric


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## Niebur3

Eric Stevens said:


> Not hard or expensive.
> 
> A simple silicone mold made off of a master and you can cast them out of epoxy or urethane.
> 
> You could hand form the master or use SLA or 3D printer as mentioned above.
> 
> Eric


Up for a new project Eric???


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## JJAZ

One critical parameter is the distance the dome sits from the parabola, get that wrong and the whole purpose of the lens is destroyed.

Hmm.. I have a presentation on it somewhere, including some nice simulations. Let me see if I can find it..


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## Huey

A similar design to the B&O tweeter lens is the Mirage Omnipolar design. Ever since I saw these speakers, I thought about how they would sound in a dash corner placement. I have the bookshelf speakers at home and I love them. Huge soundstage that make the walls disappear. I'm sure it may not work quite as well in an auto environment, but I can't see it being any worst then a direct radiating speaker. I think a small mid/tweeter up firing into an omniguide at the dash, with a dedicated midbass in the doors would be pretty amazing for soundstage in a car.


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## Wesayso

I like this idea, I allready used 3D printing for a tweeter cup. Would love to get some info on the dimensions and shapes needed. 
Jowens500, how does that Audi sound? 



req said:


> i just cant figure out how these could be made for any acceptable cost, even if they were made in large batches.


If you want to know what the cost is, get an account at: Shapeways | Passionate about creating and upload your model. Choose your material and you have your figure...


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## JJAZ

Hmm... The presentation I have is in danish, but I have uploaded it to my site, here:
http://www.jjaz.dk/privat/b&o.rar

Have a look at it.. I will try and explain any questions you may have, but I am by no means an expert on the "acoustic lens subject".


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## 60ndown

i could make one out of some plastic yogurt cups and a hot melt glue gun in 5 minutes.


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## turbo5upra

60ndown said:


> i could make one out of some plastic yogurt cups and a hot melt glue gun in 5 minutes.


:surprised: burn yer car DOWN iN60 seconds? lol


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## turbo5upra

oh... and I just downed two yogurts... need to containers?


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## Wesayso

Have you seen this thread:
Cloning a $3200 Speaker for $400 - diyAudio

It seems Patrick gave up on it. 3D modeling and printing would be safer 
It's a shame I don't see how I could incorporate this in my car. I'd love to try it.


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## HondAudio

Wesayso said:


> Have you seen this thread:
> Cloning a $3200 Speaker for $400 - diyAudio
> 
> It seems Patrick gave up on it. 3D modeling and printing would be safer
> It's a shame I don't see how I could incorporate this in my car. I'd love to try it.


Patrick gave up on a project? If *he* gives up on something, that's when you truly know it's beyond the realm of what you can do at home


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## req

i dunno, i think if i knew the algorithm i could make it. i would most likely make it out of clay, then make a mould from silicone, then cast copies from resin...

but i dont have the time to mess with it


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## highly

See my original build thread. It was the patent from this that drove the experimentation of the tweeter lens that I was playing with at the time. Though my design differed from theirs, their patent helped mold the shape of some of what I was doing then. My results were positive in that it was clear this was a path that could produce results, but I found that I could get further by selecting speakers with favorable directivity patterns and careful aiming in less time. Finding the Beo5 and the patent online as I started researching what I was doing made me realize that it had already been done and that I was following a path that already had a solution, so my time wasn't being spent coming up with something new. 

It always comes back to time...

-T


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## highly

jowens500 said:


> I actually have an Audi A8L W12 with the B&O system in the shop right now.
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> Rear tweeter.


Looks a lot like what I used for a base in my experiments...


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## Patrick Bateman

HondAudio said:


> Patrick gave up on a project? If *he* gives up on something, that's when you truly know it's beyond the realm of what you can do at home


I nearly cut my thumb off on that project :O

I should post the pics on my forum, they're disgusting

Walked into the supermarket with half my thumb hanging off and a trail of blood behind me

_(real DIYers don't go to the hospital, right?)_

My right thumb has been tingling for three years now because of that stupid project

But it IS a neat idea isn't it?

It's tough to build though. The dimensions are really tight, and I was using power tools, and they're not forgiving...


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## Wesayso

3D printing would be a much safer way to try it 
It's not that hard to produce a 3D drawing if you know what you want. Upload it and you get your model. Materials are still a bit limited but more are getting available in time.


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## Patrick Bateman

JJAZ said:


> Hmm... The presentation I have is in danish, but I have uploaded it to my site, here:
> http://www.jjaz.dk/privat/b&o.rar
> 
> Have a look at it.. I will try and explain any questions you may have, but I am by no means an expert on the "acoustic lens subject".












Check out the patents... They're VERY detailed. Just google under "Sausalito Audio Works."

The lens isn't all that complex. IIRC, the disc needs to be the same size as the low frequency cutoff of your driver. For instance, if you're using a 3/4" dome and you want to cross it over at 2khz, you'll need a disc that's just 2.15" in diameter.

That's one of the cool things about the design - it doesn't need a lot of space.

I am guessing that you could use a bigger disc if you wanted directivity below the crossover point, for instance you might opt for a 4.3" disc to control things below the cutoff.

In the patent, S.A.W. demonstrates that the technology works with compression drivers, and compression drivers also simplify the lens. (Because the wavefront of a compression driver is a flat disc - you don't have to bend the wavefront the way you do with a dome.)


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## cvjoint

signed in


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## The A Train

sub'ed


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## WLDock

I read on the net that the tweeter used is a version of the XBL Ceradome...I don't know if it is true or not? However, now that the Creative Sound Solutions LD25X XBL tweeter is available...some have said that it would make a nice tweeter for horn use as it is avalable without a face plate, has very low distortion, flat response, and can go low. Sounds like the perfect tweeter for a project using a Acoustic Lens.


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## goodstuff

meetoo subscribbles.


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## BigRed

has anybody heard this arrangement in the vehicle? I have talked to one respected person who said it was less than desirable. I have personally not heard it.


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## turbo5upra

I will say this... I was rather pleased to get back in my car after test driving a new s4 with the b&o system. Not these tweeters but it was underwhelming to put it nicely. Wouldn't mind listing for grins tho.


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## cbrunhaver

The inventor of this tech is Manny Lacarruba at Sausalito Audio Works. My understanding that it was then licensed to B&O for use in the Beolab5 et al.

The measurements of it in some custom studio monitors that he had made used to be posed on his website at sawonline.com, which is now gone. The measurements showed near 180 degree dispersion. The new company website is sausalitoaudio.com but it is sparse on details. 

You might consider getting some quotes from somebody with e Z-corp printer or makerbot, as they are considerably cheaper than a normal SLA and can be infused with stuff to make them quite sturdy. With some quick googling, you can submit an STL out of solidworks and see what it will cost you. 

Here is one place that has an online quote process.
Zcorp Rapid Prototyping


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## Notloudenuf

cbrunhaver said:


> The inventor of this tech is Manny Lacarruba at Sausalito Audio Works. My understanding that it was then licensed to B&O for use in the Beolab5 et al.
> 
> The measurements of it in some custom studio monitors that he had made used to be posed on his website at sawonline.com, which is now gone. The measurements showed near 180 degree dispersion. The new company website is sausalitoaudio.com but it is sparse on details.
> 
> You might consider getting some quotes from somebody with e Z-corp printer or makerbot, as they are considerably cheaper than a normal SLA and can be infused with stuff to make them quite sturdy. With some quick googling, you can submit an STL out of solidworks and see what it will cost you.
> 
> Here is one place that has an online quote process.
> Zcorp Rapid Prototyping


Sausalito Audio has those white papers (or at least what I think you are referring to) on their website now. They are over my head but 'seem' to have a lot of useful info for recreating this technique.


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## req

ive read all of the whitepapers and i did make some prototypes with clay and paper mache, but the added width of more traditionaly install techniques is more effective and much more transparent than having a huge directivity lens on the dash. when i get my computer set up after i finish moving in a few weeks ill get some pictures working to show you guys what i tried =)


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## Cooluser23

So what's the status of this? Did anyone ever attempt this?


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## req

yup.

i made one out of epoxy resin, and one out of some kind of pulp paper stuff. i first made the shape i wanted out of non hardening modeling clay, and then after i was satisfied i took some weird powder that when i added water it turns to some crazy jello type stuff as long as it stays moist. the problem with this kind of mould is that over time it shrinks as it looses water.

so i poured the pulp paper stuff in, and it took like 3 days to dry. then i put the epoxy resin in, and it didnt cure all the way, so when it came out it was still very tacky. after everything dried up, i was able to sand them both down and fix any imperfections.

i bought two dayton (or morel, whatever youd like to call them) tweeters because the flange is held on by screws, and i made a small aluminum plate that screwed into the bottom of the lens, and the tweeter mounted to the plate. 

it did give me directivity - i didnt have any measuring equipment, but i couldnt say weather the off axis dispersion control was as strong as i wanted it to be. the problem with them on the dash was that they were too "inboard". the stage was not as wide even though the off axis control was there. 

the tweeters i have now are ring radiators, and they have exelent off axis control for just being a traditional type speaker - and they are mounted about five inches "outboard" in each direction than i could have fit the lenses unless i cut them up, cut up the pillars, and what not - even if i did all that, it would have gotten me maybe 2 or 3 inches - so the way my tweeters are set up now are still wider and offer a similar off axis response.

its mostly about size, if i could get these to be smaller - maybe using a 1\2 inch tweeter instead of a 1 inch tweeter, they could possibly fit in the sail panels... but its kind of a moot point when a speaker will do a similar thing without a lens at all [ring radiator].

ill get some pictures of them when i get home to put up here for your eyeballs to enjoy


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## Patrick Bateman

Cooluser23 said:


> So what's the status of this? Did anyone ever attempt this?




















Here's mine. They're pretty crude, but they get the job done. Took about five minutes to assemble.

I intentionally used two lenses, because the Neo8 diaphragm isn't symmetrical. (IE, if it was square or round I would use one, not two.)

Also, if I'm not mistaken, you likely need to use some EQ to bring up the top end. This is because the lens widens the directivity. And since the directivity is widened, the SPL level will be lower.

Horns and waveguides do the same thing. For instance, if you have a 1" tweeter and you put it in a waveguide, the on-axis SPL will be higher. But that's a tradeoff; the energy which was normally radiated to the sides is focused to the front.

This is one of the odd things about horns. You'd think that they raise the SPL level, but this is only partially true. It *does* raise the on-axis SPL, but at the cost of off-axis SPL.

And the reverse holds true too; if you take the energy and spread it wider via waveguide or lens, at a frequency where it's beaming, the on-axis SPL will be *lower* not higher.

Anyways, long story short, you might want to tip up the SPL at the frequency that the lens is tuned. 

The NEO8 is already rising on-axis, so that helps.

a


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## req

Thanks for chiming in Patrick. 

I forgot to post pictures, I promise I'll try to remember tonight.


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## req

this was made with a clay model, then a rubber like mold, and a paper-pulp concrete type stuff. there were some pinholes that i fixed with CA glue and i sanded it all down.

it was just too big on the dash to work. if i wanted to cut up my A pillars to sink these into them, then it would have been more practical.


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## Cooluser23

cbrunhaver said:


> The inventor of this tech is Manny Lacarruba at Sausalito Audio Works. My understanding that it was then licensed to B&O for use in the Beolab5 et al.
> 
> The measurements of it in some custom studio monitors that he had made used to be posed on his website at sawonline.com, which is now gone. The measurements showed near 180 degree dispersion. The new company website is sausalitoaudio.com but it is sparse on details.
> 
> You might consider getting some quotes from somebody with e Z-corp printer or makerbot, as they are considerably cheaper than a normal SLA and can be infused with stuff to make them quite sturdy. With some quick googling, you can submit an STL out of solidworks and see what it will cost you.
> 
> Here is one place that has an online quote process.
> Zcorp Rapid Prototyping


Internet Archive: Digital Library of Free Books, Movies, Music & Wayback Machine 
Luckily nothing on the internet can ever be deleted.  Do you remember the exact old website?


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## Patrick Bateman

req said:


> this was made with a clay model, then a rubber like mold, and a paper-pulp concrete type stuff. there were some pinholes that i fixed with CA glue and i sanded it all down.
> 
> it was just too big on the dash to work. if i wanted to cut up my A pillars to sink these into them, then it would have been more practical.


That's awesome.

One cool thing about these reflectors is that they're not super-sensitive to driver parameters.

IE, as long as the shape and size of the reflector is similar to what B&O is using, it should work fine. (Since all of this is based on geometry; it's not particularly sensitive to the thiele-small parameters.)


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## req

i totally forgot about this project until today because i moved from NY to VA and now i moved into my house.

i have this waveguide here. patrick, if you want it to play with, i can send it to you.


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## quietfly

i'm glad you brought this up or i never would have seen it!!! looks pretty cool, how did it compare to your current set up?


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## req

well truth be told, i never got the second waveguide built because of time and moving constraints. the mould i made fell apart. the material i used for the mold was a powder like torn up paper and dust you mix with water and then it expands and turns to a weird gel\rubber type crap and solidifies, then when it dries out it crumbles. so i only got one of them made. i also didnt have my RTA at the time, so no real numbers or anything came out of it.

maybe ill see if bikinpunk wants to play with it?

its in the closet somewhere and i think that maybe somone would like to see if it actually does anything.


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## Patrick Bateman

Now that I'm starting to figure out how the reflectors should be shaped (as documented in "smoke and mirrors" thread) I should be able to post some designs that are a little easier to build.

For instance, the Sausalito Audio Works patent on the B&O tweeter lens shows that a compression driver can be used. But they never explain what the lens should look like.

If I'm not mistaken, a compression driver actually simplifies the lens, because the wavefront is flat instead of curved.

But all of this is a bit tricky, because these dimensions are so small. You really have to do these things in CAD, because even an error of a single centimeter will make a difference.


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## quietfly

this is again the perfect project for a 3d printer....


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## HondAudio

Yes, but how does a Huey Lewis album sound with wave-guided tweeters?


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## quietfly

HondAudio said:


> Yes, but how does a Huey Lewis album sound with wave-guided tweeters?


I'd hazard a guess and say he still sounds like he wants a new drug....


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## req

well, as you can see in my first post - i am fairly handy with CAD - and there are several places online that can make a 3D printed thing come to life for a fair cost.

assuming the diaphragm is 1 inch \ 25mm - i could just send my design out and have them print one. then when i get it in the mail i could send it to quietfly and he could make an archival mold from silicon and then we could make quite a few of them.

these are just some ideas- and pat, if you are interested to shoot me some sketches or ideas i could model them up pretty quickly.

it is a very interesting approach - and if we got them made from a mold, you could theoretically shave down the thing so it fits snug to the A pillar on each side, or sticks out of the A pillar and aims right at the listening position and there would be very minimal reflections.

just some ideas i guess.


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## quietfly

req said:


> well, as you can see in my first post - i am fairly handy with CAD - and there are several places online that can make a 3D printed thing come to life for a fair cost.
> 
> assuming the diaphragm is 1 inch \ 25mm - i could just send my design out and have them print one. then when i get it in the mail i could send it to quietfly and he could make an archival mold from silicon and then we could make quite a few of them.
> 
> these are just some ideas- and pat, if you are interested to shoot me some sketches or ideas i could model them up pretty quickly.
> 
> it is a very interesting approach - and if we got them made from a mold, you could theoretically shave down the thing so it fits snug to the A pillar on each side, or sticks out of the A pillar and aims right at the listening position and there would be very minimal reflections.
> 
> just some ideas i guess.



i'm totally up for this!


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## quietfly

Is there a specific type of tweeter that benefits this type of wave guide


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## req

Any 1inch or 25mm dome that you want to surface mount and have a 90* off axis angle and controlled dispersion. Basically a home brew bang and oulfsen tweeter lens.


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## Patrick Bateman

req said:


> Any 1inch or 25mm dome that you want to surface mount and have a 90* off axis angle and controlled dispersion. Basically a home brew bang and oulfsen tweeter lens.


If I'm not mistaken, the shape of the radiator makes a difference.
I'm still sorting out the details, and I'll post that in my 'smoke and mirrors' thread as I sort it out.

But I believe the following (tentatively)









1) If the radiator is a flat disc, then a simple 45 degree reflector will redirect the sound 90 degrees. For instance, with a disc shaped diaphragm that's firing straight up, it'll hit a 45 degree reflector and "mirror" the sound 90 degrees from the origin









2) If the radiator is a dome, then the reflector has to compensate for that. I think this is why the reflector in the B&O is concave









3) If the radiator is an inverted dome, like the Focal, then you'd want a convex reflector

Not 100% sure on these, and everything is complicated by the fact that the shape of the reflector doesn't just change the dispersion it also changes the pathlength.


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## Patrick Bateman

cajunner said:


> so, the radial EMIT tweeter *should* have a flat top, or linear waveform, making this more simple?


Compression driver would be the easiest by far.

Anything 'flattish' would work pretty decent too, like these:


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## stochastic

Patrick Bateman said:


> If I'm not mistaken, the shape of the radiator makes a difference.
> I'm still sorting out the details, and I'll post that in my 'smoke and mirrors' thread as I sort it out.
> 
> But I believe the following (tentatively)
> 
> 1) If the radiator is a flat disc, then a simple 45 degree reflector will redirect the sound 90 degrees. For instance, with a disc shaped diaphragm that's firing straight up, it'll hit a 45 degree reflector and "mirror" the sound 90 degrees from the origin
> 
> 2) If the radiator is a dome, then the reflector has to compensate for that. I think this is why the reflector in the B&O is concave
> 
> 3) If the radiator is an inverted dome, like the Focal, then you'd want a convex reflector
> 
> Not 100% sure on these, and everything is complicated by the fact that the shape of the reflector doesn't just change the dispersion it also changes the pathlength.



No, this is not accurate. A dome, or a cone, or a concave/inverted dome or a flat piston tweeter will all move up/down and thus radiate a typical pattern outward. If it was a tweeter pulsating spherically rather than a pistonic dome, then a different radiation pattern would occur. Exact shape of the diaphragm effects the resonances and cone breakup modes of the diaphragm, as well as internal clearance of the central pole piece, internal cavity resonances, diaphragm stiffness, and diaphragm weight - NOT radiation pattern.

This is taken from Newell P. Holland's Loudpseakers for Music Recording and Reproduction (2007, focal press) page 42.

Edit: though ring-radiators are an exception. Their gap in the middle of the diaphragm creates interference patterns and thus intricate radiation patterns depending on exact design.


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## quietfly

cajunner said:


> sooner or later, somebody was going to make a Plasma tweeter for the car, a necessary exercise...


lol
nice


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## ppsieradzki

I actually have a 3D printer. I know this thread is SUPER old, but I would actually be willing to trade a free 3D print in exchange for the files? 

I'd really like to see how this looks in real life! 



req said:


> So i do not know what the mathmatics involved in this are - its something to do with a parabola and the focus point of the sound, im assuming it has to do with the disatnace from the diaphram of the tweeter to the focal point of the parabola to meet the inverse arc - and all that has to do with the diameter of the diaphram and such.
> 
> but getting some of these made would be sweet - but the cost of the part would be astronomical. building a pair of these in any sort of accuracy would be next to impossible without precision machine tools too.
> 
> but i really like the way that they are going with this design and i think it is extremly fitting for the enviornment of the car audio world.
> 
> patrick? any comments? mic wallace?
> 
> i just threw this design together using the vifa NE19VTS-04 3\4" silk dome tweeter as a base for dimensioning purposes. im sure there are other tweeters that could benefit, and it would be very easy to integrate into may cars - depending on the depth of the tweeter to be used.
> 
> i just cant figure out how these could be made for any acceptable cost, even if they were made in large batches.


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## req

sounds good to me heheh.

let me dig them up. on top of that though, i can make new designs for specific model tweeters too.


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## Patrick Bateman

stochastic said:


> No, this is not accurate. A dome, or a cone, or a concave/inverted dome or a flat piston tweeter will all move up/down and thus radiate a typical pattern outward. If it was a tweeter pulsating spherically rather than a pistonic dome, then a different radiation pattern would occur. Exact shape of the diaphragm effects the resonances and cone breakup modes of the diaphragm, as well as internal clearance of the central pole piece, internal cavity resonances, diaphragm stiffness, and diaphragm weight - NOT radiation pattern.
> 
> This is taken from Newell P. Holland's Loudpseakers for Music Recording and Reproduction (2007, focal press) page 42.
> 
> Edit: though ring-radiators are an exception. Their gap in the middle of the diaphragm creates interference patterns and thus intricate radiation patterns depending on exact design.



I disagree. The shape of the diaphragm influences the *frequency response* and that influences the radiation pattern. Basically you have to look at the phase plug and the radiator as a unit. *And the SAW lens is a phase plug. So is the Paraline, and it's easier to understand these devices once you understand they're both doing the same thing.*










The whole reason that a compression driver has this complex phase plug is to make the distance to the throat equidistant. IE, if the radiator in a compression driver was flat, you wouldn't need a phase plug.









In the Celestion compression drivers the diaphragm is nearly flat, because the phase plug is much simpler than the TAD. IE, Celestion can "get away with" a much simpler phase plug because the diaphragm is smaller and flatter. The diaphragm isn't perfectly flat, because that wouldn't be strong, but it's much flatter than a half dome. JBL does something similar in their waveguides that are driven by a dome tweeter, the "dome" is almost flat.


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## cajunner

the geometry of phase plug design, is a mathematics exercise.

this Sausalito thing, to me, is taking directivity and efficiency together, and producing a dome tweeter's output with more reflection control and greater output capability.

if that's not true, then why are we discussing it?

What would a compression driver's attachment to the Sausalito top-hat, look like if the wave-front is flat at the exit of the driver's opening?

that's not immediately obvious, maybe a mathematician, or rocket scientist can get their vectors and venturi modeling textbooks out and produce a sample....


lol...

really, it would be nice to put some big 4" voice coil, flat pack 7" round, compression drivers sunk into the dash about 2" and have Sausalito plexi-glass top waveguides control the windshield bounce...


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## Patrick Bateman

cajunner said:


> the geometry of phase plug design, is a mathematics exercise.
> 
> this Sausalito thing, to me, is taking directivity and efficiency together, and producing a dome tweeter's output with more reflection control and greater output capability.
> 
> if that's not true, then why are we discussing it?
> 
> What would a compression driver's attachment to the Sausalito top-hat, look like if the wave-front is flat at the exit of the driver's opening?


You can use a compression driver with the SAW lens.
In fact, it seems to work better. I tried it with compression drivers and with domes.

Having said that, you could tweak the shape a little bit to make it a better match for a dome.









But if it were me, I would just use the 'standard' shape, which is a Fibonacci spiral, and drive it with a flat wavefront. Either a compression driver or a ring radiator are good candidates.



cajunner said:


> that's not immediately obvious, maybe a mathematician, or rocket scientist can get their vectors and venturi modeling textbooks out and produce a sample....
> 
> 
> lol...
> 
> really, it would be nice to put some big 4" voice coil, flat pack 7" round, compression drivers sunk into the dash about 2" and have Sausalito plexi-glass top waveguides control the windshield bounce...


Unfortunately, this won't work. Here's why:

Directivity is based on size. For instance, a 15" waveguide controls directivity down to 900hz, but a 7.5" waveguide only works down to 1800hz. Every time you halve the size, you lose an octave.

The entrance to the SAW lens is about 4cm in diameter. Due to that, the SAW lens works it's magic from about 8500hz and up. Here's the maths:

(speed of sound / size ) =
=(34,000 cm per second / 4)
=8500hz

Now if you double the size, it will start working at 4,250hz. But you'll also need to use a radiator that's double the size. And at that point, you're really struggling to get to 20khz.

















Here's a picture and the frequency response of a Fostex 3" that I put into a SAW lens. You can see from the measurement that it needs about 30dB of EQ at 20khz to make it flat. So that means that if I give it ten watts at 1khz I have to give it a thousand at 20khz!


IMHO, B&O has the right idea. Here's B&O's recipe:

First, you get a small tweeter and you put it in the lens. The smaller the better, because a small tweeter is omnidirectional to a higher frequency. For instance, a 3/4" dome is omnidirectional all the way to 18khz. *So the SAW lens isn't having a huge effect; it's basically allowing us to flip the tweeter and face it straight up.*

The next part of the recipe is a small midrange, basically small enough that you can 'hand off' to the small tweeter. If you used a 5" or a 6.5" midrange the polar response wouldn't match at the crossover point.


















IMHO, the reason that B&O used *two* SAW lenses in their first effort, but now only use one in *all* the new designs, is because of this design philosophy. Basically the SAW lens looks cool, but it's only working over a very narrow bandwidth, about one octave.

In fact, I think the platters and the shape of the baffle is having a larger effect. Because size matters with directivity, the platters are working over a wider bandwidth then the lens is.

Also, it's possible that the new speakers are using a vertical array of small woofers, because that would also get you the narrow pattern that the SAW lens does. (Odd as it seems, a *tall* speaker has narrow vertical directivity while a *short* speaker has wide vertical directivity. And Sausalito Audio Works is all about narrow vertical directivity, it's right there in the patent, they are of the opinion that wide horizontal directivity and narrow vertical directivity is the ticket.)


----------



## cajunner

they use two 4" drivers in that 18.

I would suggest using the windshield as the top platter, and having a chunk of plexy meet it, shaped suspiciously like a Sausalito fibonacci, sideways spiral, haha...

fibonacci, I always wanted one of those.


----------



## Patrick Bateman

cajunner said:


> they use two 4" drivers in that 18.
> 
> I would suggest using the windshield as the top platter, and having a chunk of plexy meet it, shaped suspiciously like a Sausalito fibonacci, sideways spiral, haha...
> 
> fibonacci, I always wanted one of those.


yep, that'll work. Basically the dash and the windshield constrain the vertical directivity.

Because I don't want to tear up my dash I would mount the whole thing upside down. Basically tweeter at the top, firing down.


----------



## cajunner

Patrick Bateman said:


> yep, that'll work. Basically the dash and the windshield constrain the vertical directivity.
> 
> Because I don't want to tear up my dash I would mount the whole thing upside down. Basically tweeter at the top, firing down.



okay, now if I do sink a 2447 with 1.5" exit into my dash, how tall do these chunks need to extend from the dash top...

hey, using just one of these, as a center channel, wouldn't that go down to 500 hz since the waveguide is essentially 4 feet wide?

that would be crazy!

and on the back side, I could put a couple of cop lights like the firemen use, for the misdirection.

maybe even build it into a pod...

and stage height?

no problem, badda bing...


----------



## Patrick Bateman

cajunner said:


> okay, now if I do sink a 2447 with 1.5" exit into my dash, how tall do these chunks need to extend from the dash top...
> 
> hey, using just one of these, as a center channel, wouldn't that go down to 500 hz since the waveguide is essentially 4 feet wide?
> 
> that would be crazy!
> 
> and on the back side, I could put a couple of cop lights like the firemen use, for the misdirection.
> 
> maybe even build it into a pod...
> 
> and stage height?
> 
> no problem, badda bing...




















Height of the lens is equal to twice the width of the lens "throat".
Note that this isn't necessarily the same size as the radiator. For instance, the lenses with 3/4" tweeters have a throat that's about 1" in diameter.
And you can also go the other way; I used a throat that was about 2.5" with a 3" woofer. I did this because I figured a smaller lens would go higher than a larger lens.

If I were to do this I would use the smallest ring radiator I could find, or I would use a compression driver. I tried it with some ribbons but they're too big and the response was ****ty. (I tried it with both NEO8 and NEO3.)


----------



## cajunner

so are you saying I need 3" tall of plexi lens, to go with the 1.5" diameter exit on my JBL CD driver?

I guess I could form it out of lexan tube, using some heat...

I'd want it to be camouflaged, with some sort of "in the window" light box that made the chunk on the dash less conspicuous.

the CD driver will have to be flushed, I guess I could make a "dash mat" that was really an escutcheon panel for the bottom of the guide...


maybe I could even 'fix' some of the HOM that result, using absorption leaves in the design, we're talking dash-wide output at >100 db/watt sensitivity, 500-12K, right?

that's a long tall Sally right there... maybe smoke, Lexan smoked, fibonacci curls. Impress the judges with that one, hah!


----------



## Patrick Bateman

cajunner said:


> so are you saying I need 3" tall of plexi lens, to go with the 1.5" diameter exit on my JBL CD driver?
> 
> I guess I could form it out of lexan tube, using some heat...
> 
> I'd want it to be camouflaged, with some sort of "in the window" light box that made the chunk on the dash less conspicuous.
> 
> the CD driver will have to be flushed, I guess I could make a "dash mat" that was really an escutcheon panel for the bottom of the guide...
> 
> 
> maybe I could even 'fix' some of the HOM that result, using absorption leaves in the design, we're talking dash-wide output at >100 db/watt sensitivity, 500-12K, right?
> 
> that's a long tall Sally right there... maybe smoke, Lexan smoked, fibonacci curls. Impress the judges with that one, hah!












^^ Here's a pic from the Paraline patent. You can see that it's possible to use a lens that's shorter or taller than what B&O uses. The key is that the vertical coverage will change. Basically the taller the lens is, the wider the vertical coverage, and vice versa.









Even with a 3/4" tweeter the B&O lens sits a fraction of an inch from the windshield. The main reason I abandoned trying to put these in my car is that the height gets quite tall in a hurry. So I couldn't find a way to mount them up high without taking over the whole dash. Obviously, putting the driver *in* the dash helps, but I don't want to chop up my dash.

There's nothing stopping anyone from putting these other places too. I believe there's a Mercedes that uses them in the A pillars. They would also work under the dash, where the narrow vertical directivity would reduce reflections off the floor and the underside of the dash.


----------



## cajunner

Patrick Bateman said:


> ^^ Here's a pic from the Paraline patent. You can see that it's possible to use a lens that's shorter or taller than what B&O uses. The key is that the vertical coverage will change. Basically the taller the lens is, the wider the vertical coverage, and vice versa.
> 
> 
> 
> 
> 
> 
> 
> 
> 
> Even with a 3/4" tweeter the B&O lens sits a fraction of an inch from the windshield. The main reason I abandoned trying to put these in my car is that the height gets quite tall in a hurry. So I couldn't find a way to mount them up high without taking over the whole dash. Obviously, putting the driver *in* the dash helps, but I don't want to chop up my dash.
> 
> There's nothing stopping anyone from putting these other places too. I believe there's a Mercedes that uses them in the A pillars. They would also work under the dash, where the narrow vertical directivity would reduce reflections off the floor and the underside of the dash.


is the air, to either side necessary?

can you just transverse-section the whole apparatus, so that there is a flat wall to either side, the way you can do with a Linaeum, and if so, is the 360 Sausalito also possible, for the "depth" of stage everyone wants?

That might make it possible to extend these out to the dash edge, and incorporate them into a panel where they aren't so obtrusive.


What I like about them is they have directivity control without the use of a traditional wave-guide, I don't really need the extra gain of a horn implementation if I can control the reflection quotient, and if I am starting with CD-type sensitivity.

I would imagine that you could design a neo CD driver specifically for this implementation, that would reduce the thickness to under an inch of motor, and the dash could be "scooped out" for the guide, leaving little promontory excess, or blocking the driver's field of vision.


----------



## quietfly

what about hiding it in the a pillars?


----------



## Patrick Bateman

cajunner said:


> is the air, to either side necessary?
> 
> can you just transverse-section the whole apparatus, so that there is a flat wall to either side, the way you can do with a Linaeum, and if so, is the 360 Sausalito also possible, for the "depth" of stage everyone wants?


Yep. That was one of the things that blew my ****ing mind about the lens. It basically works like a cardioid; the signal sent *backwards* is very similar to the signal sent *forwards*, but it's attenuated.

This is kinda the Holy Grail when it comes to directivity; the idea that the sound off-axis has the same shape as the sound ON axis. (There's a thread on diyaudio that's a few hundred pages long on what the "ideal" directivity is, but IMHO cardioid is about as good as it gets.)

*So, long story short, YES you want air to the left, to the right, and even behind the speaker. This is part of the magic.*

















Here's a couple measurements.
The top measurement is on one of these SAW lenses that I built, using a Celestion CDX1-1425.
The bottom measurement is an oblate spheroidal waveguide, driven by a compression driver.

If you look at the two measurements, you can see that the response shape is relatively similar. Mine looks a lot rougher, but my scale is only 50dB, whereas the scale of the other measurement is 90dB. Basically mine is 'zoomed in' which exaggerates the peaks and dips. *Both devices need EQ, you can see the mass rolloff begin about 4khz.* So they're going to need CD EQ to offset that.

*IIRC, the yellow curve is on-axis, the orange curve is 22.5 degrees off axis, and the red curve is 45 degrees off axis.* The grey curve is a whopping 180 degrees off axis.

The crazy thing about the Sausalito lens is that the response is basically identical whether you're on axis or off axis. Over a four octave span from 1khz to 20khz, the level on axis is within three decibels of the level off axis. Even weirder, if you're *behind* the speaker the shape is similar, just quieter.

These results are pretty consistent with the measurements of the 'real' Beolab by the way.

If you look at the measurement of the oblate spheroidal waveguide, you can see that the output *shape* is consistent, but it's definitely "hotter" on axis. By the time you're 45 degrees off axis, the output level has fallen by 10dB. As someone who owns a set of Gedlee Summas and who's built a Beolab lens, I can tell you that they sound very very different. The Beolab lens sounds much more 'diffuse.' Due to the diffuse nature of the sound, the speaker location isn't as critical, and aiming the speaker is virtually pointless, since the angle of the speaker doesn't change the sound very much, until you reach really wide angles, like 180 degrees off axis. It *does* like to be away from boundaries, so I'd keep it away from the side windows if possible. It might work well *under* the dash, since the windows are a lot more reflective than the carpet in a car. To find out for sure you'd simply have to build one and listen.




cajunner said:


> That might make it possible to extend these out to the dash edge, and incorporate them into a panel where they aren't so obtrusive.
> 
> 
> What I like about them is they have directivity control without the use of a traditional wave-guide, I don't really need the extra gain of a horn implementation if I can control the reflection quotient, and if I am starting with CD-type sensitivity.
> 
> I would imagine that you could design a neo CD driver specifically for this implementation, that would reduce the thickness to under an inch of motor, and the dash could be "scooped out" for the guide, leaving little promontory excess, or blocking the driver's field of vision.


Note that you *do* get some gain from these devices. They're significantly louder than an omnipolar speaker, because their energy is focused into a narrow vertical lobe. B&O uses a plain ol' dome tweeter and their speaker gets crazy loud.

I really think that just flipping it upside down works pretty good. It certainly makes it bulky and it's not pretty but you can hide a neo tweeter pretty easily.


----------



## Patrick Bateman

quietfly said:


> what about hiding it in the a pillars?


My main concern would be that it might make the stage sound narrow.
It kind of likes to be pulled away from reflective surfaces.
Admittedly, the windshield is pretty darn reflective, but the device has narrow vertical directivity so it doesn't "see" the windshield very much.

Although it likes to be away from reflective surfaces, a certain amount of reflections seem to add some 'bloom' to the sound. This is a lot different than waveguide speakers, because the horizontal directivity of the device is exceptionally wide. If you look at the polars I posted, you can see that the horizontal directivity of the SAW lens is even wider than a 3/4" dome tweeter, all the way to 20khz.


----------



## cajunner

Patrick Bateman said:


> Yep. That was one of the things that blew my ****ing mind about the lens. It basically works like a cardioid; the signal sent *backwards* is very similar to the signal sent *forwards*, but it's attenuated.
> 
> This is kinda the Holy Grail when it comes to directivity; the idea that the sound off-axis has the same shape as the sound ON axis. (There's a thread on diyaudio that's a few hundred pages long on what the "ideal" directivity is, but IMHO cardioid is about as good as it gets.)
> 
> *So, long story short, YES you want air to the left, to the right, and even behind the speaker. This is part of the magic.*
> 
> Here's a couple measurements.
> The top measurement is on one of these SAW lenses that I built, using a Celestion CDX1-1425.
> The bottom measurement is an oblate spheroidal waveguide, driven by a compression driver.
> 
> If you look at the two measurements, you can see that the response shape is relatively similar. Mine looks a lot rougher, but my scale is only 50dB, whereas the scale of the other measurement is 90dB. Basically mine is 'zoomed in' which exaggerates the peaks and dips. *Both devices need EQ, you can see the mass rolloff begin about 4khz.* So they're going to need CD EQ to offset that.
> 
> *IIRC, the yellow curve is on-axis, the orange curve is 22.5 degrees off axis, and the red curve is 45 degrees off axis.* The grey curve is a whopping 180 degrees off axis.
> 
> The crazy thing about the Sausalito lens is that the response is basically identical whether you're on axis or off axis. Over a four octave span from 1khz to 20khz, the level on axis is within three decibels of the level off axis. Even weirder, if you're *behind* the speaker the shape is similar, just quieter.
> 
> These results are pretty consistent with the measurements of the 'real' Beolab by the way.
> 
> If you look at the measurement of the oblate spheroidal waveguide, you can see that the output *shape* is consistent, but it's definitely "hotter" on axis. By the time you're 45 degrees off axis, the output level has fallen by 10dB. As someone who owns a set of Gedlee Summas and who's built a Beolab lens, I can tell you that they sound very very different. The Beolab lens sounds much more 'diffuse.' Due to the diffuse nature of the sound, the speaker location isn't as critical, and aiming the speaker is virtually pointless, since the angle of the speaker doesn't change the sound very much, until you reach really wide angles, like 180 degrees off axis. It *does* like to be away from boundaries, so I'd keep it away from the side windows if possible. It might work well *under* the dash, since the windows are a lot more reflective than the carpet in a car. To find out for sure you'd simply have to build one and listen.
> 
> 
> 
> 
> Note that you *do* get some gain from these devices. They're significantly louder than an omnipolar speaker, because their energy is focused into a narrow vertical lobe. B&O uses a plain ol' dome tweeter and their speaker gets crazy loud.
> 
> I really think that just flipping it upside down works pretty good. It certainly makes it bulky and it's not pretty but you can hide a neo tweeter pretty easily.


this is great success!

now, I'm thinking of what this, hanging off the bottom of an underdash ID horn's diffraction quarter round, would sound like, you know.. for the "super-tweeter" effect.

would it be cohesive, would it clash? 

I can't picture it upside down for some reason, I thought the focal point of the bottom "platter" was specific to the output, even more-so than the top platter?

I would like to know if it would be able to use the natural horn of the windshield/dash juncture as a boundary or not, I understand that the theoretical optimum is parallel surfaces for the platters, but going next best scenario, what about 2pi, or in-wall mounting? I know planar magnetics like the dipole config but they also do well with a closed rear, maybe there hasn't been anyone who has attempted to slice a Sausalito sausage into the half-pipe?

I'm getting a picture of the Karlson parabolic opening, mated to the Sausalito using a true ribbon, and it's on a 2 dimensional plane... now if we could just bring it up from the paper and give it wings... Linaeum wings... haha...

too much coffee...

:blush:


----------



## req

well guys - all i need is some direction on what speaker to model this with, and some specifics on the design, and we can get it 3d printed. then, we can make a mould using some silicon rubber, and then cast it with clear craft-grade resin. then it will be basically invisible. a clear lens.

thoughts?


----------



## cajunner

req said:


> well guys - all i need is some direction on what speaker to model this with, and some specifics on the design, and we can get it 3d printed. then, we can make a mould using some silicon rubber, and then cast it with clear craft-grade resin. then it will be basically invisible. a clear lens.
> 
> thoughts?


first, we gather the die. Then we strike the forge. then we mint the coin.

haha..

I think I'd like to see what the limits of the technology allow, so I'd want to make a lens at least 3" tall, platter to platter.

either it rises out of the dash like the Audi, or it tilts into place over the driver from a hinged access panel forward in the dash.

the reason I think this works is people want strong center channel output, they want it clean and relatively free of comb filtering from the dash/WS bounce, and they want it able to keep up and surpass the dynamics of the A-pillar tweets firing on-axis. We also want it to be usable while driving but that might have to take a back seat at first.

If I understand correctly, we can adjust the angle by the lens height, but wavelength itself is demonstrated by the ability of the driver, at frequency lengths that are below the curve, so to speak. So the natural gain of the windshield will support the frequencies below 1.25Khz, and the 3" of lens will create directional support for what comes in the reflective sized wavelengths.


getting these two acoustic levers to play nice, seems like the bubba in the deal, it's going to take an actual experiment and hypothesis confirmation, we're going to have to test it for proof of concept.


so, let's give the curve 5 inches, while we're dreaming.

that would make approximately 6.5" of lens, from platter to platter. How low is the lowest frequency to have gain from a lens this size, and how obtrusive is a roughly baseball cap sized chunk on the dash going to look, haha...

anyways, let's hear some ideas.


----------



## cajunner

so I've been mulling this over about 30 minutes now, and I think the expectation that I'll be able to use a compression driver's output below the lens' effective limit, is dependent on how I am able to put air around the body of the lens, and at the same time, constrain the lower frequency wavelengths coming from the CD to be uniform and expand with a rate that doesn't have much variation in the wavefront.

A dash that's symmetric across the width, a windshield that gives a lot of rake, and a place for a huge motor buried in the center channel position on most dash mounted surround sound designs, closes in our selection list to a few vehicles.

so, what about piezo?

the piezo driver is able to be fashioned in a shallow form factor, and part of the beauty of it is it's so cheap to make.

if lens height only exists to promote angle of coverage vertically, then a short lens is fine even if the driver has really good lower frequency abilities.

Maybe a CSS XBL tweeter would be a good candidate, if the lens also acts like a compression chamber, since it is basically cutting off half of the area above the diaphragm? A light compression, maybe 1.5:1 or something? This would facilitate an even lower crossover than can be had with normal mounting, making it possible to get more lower treble into the stage up top, where normally a 3" mid would have to come in, somewhere in the range of 1.5 to 1.9 Khz.

with a piezo compression driver, you can create a tiny aperture, and just use the lens like the ones in the Audi, or for that upper treble foci that helps steer logic channels to their farthest ends.


----------



## HondAudio

So... is this feasible at all with a small wideband driver, or would the lens need to be bigger than a dinner plate?


----------



## Patrick Bateman

I think I've failed to explain how the lens works in a clear way. *Let me take another crack at this.*









^^ Here's a polar response curve of a 1" tweeter.*
Note that *the tweeter is omnipolar below 6000hz.*

This is really important. When you look at the lens, you might assume that the lens is reflecting a wide bandwidth, but IT'S NOT. It is only working over a narrow bandwidth, about one octave.



















If you look at the pic above, the *lens* is the part in the very center.
There is also a baffle in the pic above.

So... *What's the baffle doing?*
The baffle is there to prevent the sound from going *backwards*. It's about 13cm wide. So the baffle will keep the sound from going *backwards* until the sound is bigger than the baffle. So, let's do the math:
(speed of sound / size) =
(34,000 cm per second / 13cm) =
2615hz.

So that 13cm baffle, *behind* the tweeter isn't just for looks... It keeps the sound from going backwards. Is the 5" width by accident? NO. I personally believe it's width is *just* wide enough to cover the tweeters bandwidth. We don't know the crossover point, but I'm willing to bet it's close to 2615hz.


















If you look at these two pics, you can see that the shape of the baffle has evolved. Eight years ago, when the lenses first appeared in the car, the baffle was bigger. As time evolved, the baffle nearly disappeared. My hypothesis is that B&O probably figured out that the windshield of the car can serve the same purpose as the baffle did. But there's a catch here; if you intend to do the same thing you'll have to get your tweeters almost flush with the windshield. If you make a lens and you put it a foot from the windshield it's not going to work.


----------



## Patrick Bateman

HondAudio said:


> So... is this feasible at all with a small wideband driver, or would the lens need to be bigger than a dinner plate?


Remember, the lens is good for about one octave. (See my previous posts, particularly my post from fifteen minutes ago.)


















Here's the response curve for a 2.5" Peerless woofer.
*See how the driver starts to beam about 4000hz?*
So a properly sized lens will be able to reflect about one octave of output.

So...

If you build a lens for this 2.5" driver, and you're able to reflect that octave from 4000hz to 8000hz, then what will you do about the last octave? IE, how are you going to cover the octave and a half from 8khz to 20khz?









This is the one I built for a 3" Fostex









Here's the response curve of the Fostex in the lens, at 0, 45, and 90(!) degrees off axis. You can see that there's a sloooow rolloff that can be corrected with EQ, and you can see the lens is making it so that the sound that's 45 degrees off axis is nearly the same as the sound that's *on* axis.

But correcting that rolloff is going to be a *****, because the Fostex is down by 30dB once you get to 20khz. That means that if you give it ten watts at 500hz you'll have to give it TEN THOUSAND watts at 20khz to get it flat.

Now if you limited the Fostex to 10khz, it wouldn't be so bad. You'd need 10dB of EQ to offset the rolloff, and that means 10 watts at 500hz and 100 watts at 10khz.

TLDR: No, you're not going to get a 3" driver to 20khz using a SAW lens. Yes, you can get it to 10khz. So pick your poison: Either use a smaller driver on the lens, like B&O does, or use multiple lenses.

If you're really adventurous you might be able to get 500hz to 20khz using a compression driver. This is because their efficiency is so high. You'll still need a ton of EQ to bring the top octave up, you can't escape that. But a compression driver has so much efficiency, you have more room to add EQ.


----------



## quietfly

AH that explanation actually clicked for me....


----------



## cajunner

I believe the emphasis in later iterations is on the forward, or cardioid dispersion and less heed is paid to the ambience, or rear wave. This is probably due to testing where there was little benefit to a wide baffle, and the crossover frequency is probably upwards of 3.5K or more.

shrinking that footprint is probably most important, considering how distracting something that large in your sightlines can be.

luckily for us, we can develop a separate set of goals, and driveability of the design can come in second to the audio.


what I see is the original attempts in the home, use larger lens in the midrange.


this larger lens makes sense, if you have to direct output below the baffle's cut-off, and it would be best if it could come cardioid instead of omni, but making that transition might be a problem.

the use of a reverse filter, or high-pass on the compression driver would allow the balancing of that downward response shift, and it would bring you closer to not needing so much equalization up top.

if bigger equals lower frequency coverage, then it'll have to be bigger, I would imagine up to the point where there is little cardioid in the polar, left.


----------



## HondAudio

So... the baffle prevents sound *below* a certain frequency from going backwards? Everything from 2615 Hz and up is going forwards?


----------



## Patrick Bateman

quietfly said:


> AH that explanation actually clicked for me....


Thanks!

Let's see if the forum supports animation, maybe I'll make a cartoon.


----------



## Patrick Bateman

okay, cool, the forum supports animation.
One cartoon, coming up...


----------



## Patrick Bateman

OK, I made an animation to illustrate how the SAW lens works.


















The top tweeter in the pic is radiating on a flat baffle.
The bottom tweeter is radiating in a Sausalito Audio Works lens, aka a B&O lens, aka a Beolab.
What you see is that the sound begins to radiate spherically, and then the curvature of the lens bends the sound into a flat wavefront.

I actually learned something from this exercise, which is that the radiation of the SAW lens is quite close to the radiation of a ribbon. (A ribbon radiates a flat wavefront because the radiator is flat.)

Let me know if this animation doesn't make sense.

If you want to study this some more, check out my threads named 'square pegs' and 'sunshine' on diyaudio. They're about the Danley Paraline, but the concepts are 100% identical.

Danley even made a video summarizing how it works :

Danley Sound Labs SBH10 - YouTube


----------



## cajunner

how low do the midrange lens go in frequency, and is it possible to fit a similar sized lens into a car?


is the lower limit defined by the lens at all, or is it that going any lower has no benefit based on standard drivers being better able to produce a polar response that is directional and not omnipolar by virtue of being placed on the front of the box, instead of the top of the box?


----------



## fcarpio

I have listened to their Beolab 5 and I was NOT impressed, at all. As a matter of fact, I disliked them very much. The bass was boomy, the highs were muted and the mids, forget the mids. It was a disappointment. They do look nice though.


----------



## Patrick Bateman

Yeah I've heard a few people say that.
The bass in the Beolab 5 is automatically adjusted, similar to what the JBL MS-8 does.
If you look at the MS-8 thread, you'll see about a zillion people complaining that the automatic adjustments don't work the way they'd like it to.

IMHO it's not possible to get good bass when measuring from a single point in the room.

As for the highs, the problem with the highs is simple:
*Once you've grown accustomed to conventional tweeters, constant directivity sounds weird. It sounds dull.*

My home speakers are constant directivity (Gedlee Summas) so I'm accustomed to the sound.

But, yes, it definitely sounds dull at first. Once you grow accustomed to it, regular tweeters sound too hot.


----------



## HondAudio

Did somebody say "motorized pop-up center channel"?


----------



## Patrick Bateman

Patrick Bateman said:


> OK, I made an animation to illustrate how the SAW lens works.
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> The top tweeter in the pic is radiating on a flat baffle.
> The bottom tweeter is radiating in a Sausalito Audio Works lens, aka a B&O lens, aka a Beolab.
> What you see is that the sound begins to radiate spherically, and then the curvature of the lens bends the sound into a flat wavefront.
> 
> I actually learned something from this exercise, which is that the radiation of the SAW lens is quite close to the radiation of a ribbon. (A ribbon radiates a flat wavefront because the radiator is flat.)
> 
> Let me know if this animation doesn't make sense.
> 
> If you want to study this some more, check out my threads named 'square pegs' and 'sunshine' on diyaudio. They're about the Danley Paraline, but the concepts are 100% identical.
> 
> Danley even made a video summarizing how it works :
> 
> Danley Sound Labs SBH10 - YouTube


My illustrations of the Beolab lens illustrated something that wasn't immediately obvious to me:

The wavefront of the Beolab lens is a LOT like a ribbon.

I'd always known that the lens had narrow vertical directivity, but it never dawned on me that it's not just narrow; *it's flat.*

























This might sound like a subtle thing, but it's actually kind of a big deal. For instance, if you're listening to a ribbon at a distance of ten centimeters, the "size" of the high frequencies is about ten centimeters tall.
If you're listening to a ribbon at a distance of a meter, the "size" of the high frequencies is *still* ten centimeters tall.

The best example of this that I could find was in this measurement of the Adam A5X studio monitor. If you look at the high frequencies, you can see they drop off REALLY fast, particularly in the vertical plot. My interpretation of the measurements is that the ribbon is very directional, particularly when the waveguide isn't reshaping the wavefront. The waveguide on the ribbon is horizontal, and that's part of the reason that it's so directional in the vertical polar response measurements. (The other reason is simply pathlength differences; all two-way speakers measure worse on the vertical axis than the horizontal because the pathlength from the mic to the speaker doesn't change when you rotate it horizontally, but it *does* change when you rotate the speaker vertically.)


















Based on my realization that the SAW lens makes a flattish wavefront, I did the obvious next step, which was to investigate whether a plain ol' ribbon is easier or better. Or a plain ol' waveguide.

The animation above is the result of my investigation. It's basically a followup to the animation that I did yesterday. The one from yesterday shows how the lens takes the radial wavefront and bends it into a flat wavefront. (Again, a lot like the Danley Paraline.)

But yesterday's animation didn't show the effect of PHASE, and this one does. So this one gives us an idea of how destructive the reflections are, and is more accurate than what I could do in Xara*.

In the animation above, you can see that the lens is more directional at 16khz than it is at 8khz. But at 16khz the wavefront has lobes in it. That's the dark vertical lines that extend out from the origin. Basically it means that at 16khz you have to be careful how you aim the SAW lens. *Luckily, this isn't a problem with the horizontal polars.* The inventor of the lens might argues that this is a feature; basically there are nulls that are aimed at the ceiling and at the floor.

But be careful where you sit! Move the lens too high or too low and it's not going to work.



* I did these animations using Hornresp. The dimensions are based on the Beolab lens with the 3/4" tweeter. The entrance into the lens is 1" in diameter and the height of the lens is 2". The platter above and below the tweeter is 5" in diameter. You can see from the sims that making either platter larger in diameter will change the wave shape and on-axis efficiency. IE, when you put it on the dash of your car it's going to be more efficient and have a narrower vertical beam than if you put it on a 5" platter like the Beolab 9 speaker.


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## 94VG30DE

has anyone tried the beolab lens on a 2" full range, something like a NSW2 Whisper? I'm looking for something to 3D print and play with over the holidays, and this B&O lens has me thinking...


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## Patrick Bateman

yeah I've built variations of this for everything from a 3/4" tweeter to a 3" midrange.

Most of them were documented in the "28 weeks later" thread


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## Wesayso

I'm still waiting for you to bring the Beolab 90 technical accomplishments to the car environment, Patrick .


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## Patrick Bateman

Wesayso said:


> I'm still waiting for you to bring the Beolab 90 technical accomplishments to the car environment, Patrick .


Too many channels. Although the Beolab 90 is the best speaker I've ever heard, the Danley SH-50 is no slouch and it's a lot simpler. (It's pretty frightening to consider a Synergy Horn "simple" lol)

To me, the only real flaw with the SH-50 is the size and the high frequency response. And I think Bill Waslo's Synergy Horn addresses both of those shortcomings.

That's why a lot of my recent projects resemble Bill's Synergy Horn. It's really REALLY good.


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## Wesayso

Is the speaker you're referring to his Cosines or his recent Synergy build with only one mid.

I was kidding about the Beolab of course... I'd love to hear it one day.


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## Patrick Bateman

Both are great, but I think the smaller one is a real achievement. Amazing sound in a small package.


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## Orion525iT

Patrick Bateman said:


> Both are great, but I think the smaller one is a real achievement. Amazing sound in a small package.


Do you have a link top this? Likely on diyAudio somewhere, but digging through those mega threads to get to the good stuff can be mind numbing. 

I am trying to decide what to do with my mids/tweeter after I get done with my midbass bandpass boxes which should cover 150-450hz easily after eq to bring down the peak. Thought about a little synergy.


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## Patrick Bateman

Orion525iT said:


> Do you have a link top this? Likely on diyAudio somewhere, but digging through those mega threads to get to the good stuff can be mind numbing.
> 
> I am trying to decide what to do with my mids/tweeter after I get done with my midbass bandpass boxes which should cover 150-450hz easily after eq to bring down the peak. Thought about a little synergy.


Sure!

New Diy Synergy type horn in natural oak - diyAudio
This is Bill Waslo's first set of Synergy Horns. AKA "cosyne"

Small Syns - diyAudio
This is his second set of Synergy Horns, aka "Small Syns"

Bill Waslo is the owner of Liberty Instruments, and author of their loudspeaker measurement software, their crossover simulation programs, and some other cool stuff. I've heard both speakers, they're great.


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## whoever

Patrick Im in the process of building the SmallSyns, I've been in conversation with Bill, I'm looking forward to hearing the results.


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