How to build an "acoustic lens", like B&O does?

[fjhuerta]

Hey all!

I'm having a crazy idea about what to build next.

I'm in love with OB, but I'm not sure if that's because of the baffle-less design or the bipolar sound. I do not like the OB's compromises, though (limited FR, and difficult to integrate).

So, this came to mind.

http://www.bang-olufsen.com/sound-co...cture=Acoustic lens

I think dlneubec already tried something similar, with good results. I think it would be interesting to learn something new. The thing is:

How do you build an "Acoustic Lens"?

I have no clue. I pretty much suck at machining and don't have much available (other than a router and a table saw). It seems plastic should be used, anyway (I suppose metal would ring and be unusable).

any ideas on how to build the lens?

[Generic George]

Well Vacuum forming as mentioned in this thread is certainly one way.

http://www.htguide.com/forum/showthread.php4?t=37697

Thing is, setups like that are typically designed to work with the characteristics of the specific drivers employed. So to make it work properly, you'd need some way of determining what the curve and size of the lens should be for your drivers.

I don't think metal "ringing" is really going to be much of an issue assuming it's a solid piece of metal. I think you need something hollow for that to really happen.

You could conceivably make one on a lathe out of wood as well.

I'd check with places that can do CNC milling, that's another option I'd think.

[AdelaaR]

"If you want to develop the best loudspeakers in the world it's no good thinking along conventional lines, or blindly following what everyone else in the industry does. Thankfully, Bang & Olufsen's acoustic engineers could never dream of doing that. They know that real breakthroughs - ones that truly make a difference - can only be achieved by thinking beyond the boundaries of what is possible today."

Hahaha ... these guys at B&O truly are great at selling things to juppies.
The B&O televisions ... I encounter them sometimes in my work and they truly are pieces of shit with crappy image ... put in a "nice looking" (not my taste at all) box.
Same goes for their speakers and music systems I guess.

Has B&O ever made any "real breakthroughs"?

About the acoustic lens: I don't think an actually wellperforming acoustic lens can be made with simple tools and would require special plastics and a specially controlled environment to make.
You could make a horn yourself and horns are something like an acoustic lens, right?

[jmik26]

Old records glued together?

[numberoneoppa]

Old records glued together?

Any time I see records used for something besides music playback, I die a little inside.

[fjhuerta]

"If you want to develop the best loudspeakers in the world it's no good thinking along conventional lines, or blindly following what everyone else in the industry does. Thankfully, Bang & Olufsen's acoustic engineers could never dream of doing that. They know that real breakthroughs - ones that truly make a difference - can only be achieved by thinking beyond the boundaries of what is possible today."

Hahaha ... these guys at B&O truly are great at selling things to juppies.
The B&O televisions ... I encounter them sometimes in my work and they truly are pieces of shit with crappy image ... put in a "nice looking" (not my taste at all) box.
Same goes for their speakers and music systems I guess.

Has B&O ever made any "real breakthroughs"?

About the acoustic lens: I don't think an actually wellperforming acoustic lens can be made with simple tools and would require special plastics and a specially controlled environment to make.
You could make a horn yourself and horns are something like an acoustic lens, right?

I don't know. I listened to the BeoLab 5 at the local B&O and they sound really, really good...

[AdelaaR]

I don't know. I listened to the BeoLab 5 at the local B&O and they sound really, really good...

I haven't heard them yet but for $16000 they'd better sound really, really good

[ultrakaz]

Hello, Dan is the man to consult regarding omni style speakers. I read on another forum that he is making a diy version of a RAAL design that is omni-esque.

Decades ago the earliest omni speaker I've heard was the Bose (gasp) 901. I recall the demo quite vividly and I have to confess I was impressed. Later, were the Shahanians, I forget which model. Now, compared to todays speakers designed with computer modeling, these omni's sound "diffused", lacking precision in the soundfield. However, and I am not totally comfortable using this term, they sound more natural as in how music sounds live where all the sounds are bouncing all over the place yet is engaging.

I don't know how one would actually design an omni, other than empirically through trial and error. Perhaps, studying the early designs and reading the propaganda would be a start. And since you already have some speaker sound accumen you could come up with something original. Yeah, original speaker designs seem to be sorely lacking.

Please keep us posted on your progress.

[sfdoddsy]

Hey all!

I'm having a crazy idea about what to build next.

I'm in love with OB, but I'm not sure if that's because of the baffle-less design or the bipolar sound. I do not like the OB's compromises, though (limited FR, and difficult to integrate).

So, this came to mind.

http://www.bang-olufsen.com/sound-co...cture=Acoustic lens

I think dlneubec already tried something similar, with good results. I think it would be interesting to learn something new. The thing is:

How do you build an "Acoustic Lens"?

I have no clue. I pretty much suck at machining and don't have much available (other than a router and a table saw). It seems plastic should be used, anyway (I suppose metal would ring and be unusable).

any ideas on how to build the lens?

Looking at speakers I suspect the building (in terms of materials) would be pretty easy

Much as you can do a test OB baffle with bits of cardboard, you could do the same with various circular planes. This appears to be the 'hat' part. Likewise the surround above the upfiring driver is easy to do and tweak.

The trick would be (IMHO) in the measuring. What are you measuring for, and how do you know when you have it?

Of course, this could just be a variation of well proven 'omni' designs like the Linkwitz Pluto, Mirage OMD series and a few interesting DIYs here which all use physical means to direct the sound of a traditional driver.

Their description of what they are trying to achieve (cardiod?) also sounds a lot like what the guys at Gradient are aiming for with the Revolution and especially the Helsinki.

I quite like the omni-esque speakers I've heard, and I use Mirage OMDs as surrounds with my OB mains, but I'd love to hear a true omni like the MBL.

[Paul W]

I believe B&O licensed the design from Sausalito Sound. The Moulton whitepapers at the attached link might help you with the design.

Whitepapers

[domwilson]

Aren't these similar in design to the old BIC Soundspan speakers?

[fjhuerta]

I dunno. I think I could work something out via trial and error, but the thing is.. how do I make the lens?

I have a silly idea - go to a department store, look at the kitchen stuff, and maybe I'll find something there. I always find stuff I can use there

Otherwise, how can I create something that works like a lens?

[ruseriousclark]

Aren't these similar in design to the old BIC Soundspan speakers?

I think the Soundspan is more of an omni-directional, but I don't know. Accoustic lenses are new to me.

[SpeakerGuy]

Make the shape roughly out of MDF, or some softwood like pine, then us something like a Microplane to shape it and smooth it? (then once you have the shape a hard coating such as liquid epoxy or such?)

Or, paper mache?

Clay (ceramic)?

I don't know. I listened to the BeoLab 5 at the local B&O and they sound really, really good...

I wasn't impressed, except for the bass. Maybe they were setup poorly where I heard them?

The salesman at the store seemed fairly rude also - might have skewed my opinion of them.

[fjhuerta]

Make the shape roughly out of MDF, or some softwood like pine, then us something like a Microplane to shape it and smooth it? (then once you have the shape a hard coating such as liquid epoxy or such?)

Or, paper mache?

Clay (ceramic)?





I wasn't impressed, except for the bass. Maybe they were setup poorly where I heard them?

The salesman at the store seemed fairly rude also - might have skewed my opinion of them.

I loved their soundstaging. It was wiiiide and deeeep. Bass also helped, though. I'm sure their omni concept is something that could work properly on a DIY speaker.

[atm98]

If its a part you can turn in a lathe then it might not be that difficult or expensive. There are plenty of machine shops around. However you might want to keep the geometry as simple as possible to keep the cost down.