# Please Help! with reflector project...



## Chester (Feb 19, 2007)

Hello, I am planning on making an 'acoustic lens' (reflector) to use on my speakers that will cause an even high frequency response in the horizontal field. Basically I am going to use the shape that Bang & Olufsen use in their speakers:








The technology was developed/licensed from this company http://www.sausalitoaudio.com/, if you check out this whitepaper http://www.sausalitoaudio.com/pdf/SAU_ALMA_WPaper_R1.pdf and scroll down to the last page you can see a graph of the off axis response achieved with a the device. There is also a review of the Beolab 5 here http://theaudiocritic.com/plog/index.php?op=ViewArticle&articleId=34&blogId=1 that has two graphs in it, one showing on axis and one showing 45 degrees offset, the graphs are nearly identical.

The Beolab 5 speakers cost $16,000 per pair, plus they are not DIY (so not as fun  ) so I intend to make some reflectors of my own for my speakers. (initially for the N7r's fullranges http://www.hometheatershack.com/forums/diy-speakers/21448-build-dc-gold-n7r-steel-enclosure.html )

My best idea (to date) to make the shape I need is to have a 3D model printed through the RedEye service http://www.redeyeondemand.com/ and then use that as a mold to make cement reflectors. The service has a $150 minimum so I may make a few different size molds presuming it would be cost effective. If anyone has any ideas, tips, suggestions how you would go about achieving this please let me know (I would like to make the mold myself however I am not sure how I would make an accurate representation of the shape)  I believe concrete would be a good (and inexpensive) material to use however glass is also an option but I would think that would need to be CNC cut or something (I am not familiar with glass production techniques) and would cost more.

Thank you for your suggestions!

-Matt

To be clear, in the picture above: the speaker is the black part at the bottom of the shape which is aiming up at the reflecting apparatus.

EDIT: here is another writeup by one of the guys who developed the Beolab 5 http://www.moultonlabs.com/more/new_loudspeaker_design/P0/


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## Anthony (Oct 5, 2006)

That's interesting, I'll give you that.

As for 3D printing, I have used quickparts.com through my company. Not too expensive, although size and complexity do add to the cost. all you need is a .stl model of the shape you want. Most CAD programs can export this format.

Good luck and keep us posted!


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## lsiberian (Mar 24, 2009)

http://www.parts-express.com/pe/showdetl.cfm?Partnumber=297-401

When that tweeter is unfaced it provides up to a 75 degree off-axis response.

Though it takes about 3 of them to find a good one on average. And they must be crossed at 5khz.


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## Chester (Feb 19, 2007)

Anthony, do you think concrete would be a good material to use? it is slightly porous (as far as I know) so I would probably seal it with an epoxy or something to aid in extremely high frequency reflection...

Isiverian: thanks for the tip with the ribbon tweeter; however I am looking to and already have eliminated the crossover with the full-range speaker... My current setup is already incredible sounding... just at the sweet spot though  Thats why I got interested in the acoustic 'lens' (reflector)... to fix the main 'weak point' in the current setup.

I may build a pair of speakers with acoustic lenses for our tv too since the couches are arranged in a semi-semicircular fashion so there is a pretty wide sweet spot target area


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