Acoustic Lens = Karlson etc ?

[Zero D]

Att. freddi et al

Hi, i thought you might find this interesting. I see some similarities between the two.

High frequency power dispersion and amplitude response

1. "The power response should be as flat and smooth as possible relative to the free field frequency response
2. "Strong floor and ceiling reflections should be avoided
3. "Strong reflection off the wall directly behind the loudspeaker should be avoided"[8]

The device that is used to accomplish this is called an “Acoustic Lens.” It is a scalable reflecting device that fits over a conventional treble dome tweeter or mid-range driver, which is facing upwards. It was invented by Manny LaCarrubba of Sausalito Audio Works, and is licensed to Bang & Olufsen

Moulton Laboratories :: A new loudspeaker design

The Acoustic Lens

The effect of the lens is to distribute energy emitted from the driver (which is facing upward) across 180° horizontally and approximately 30° vertically (angled approximately 15° upwards). Other properties of the lens permit the lower crossover point of the driver to be lowered in frequency, extending the effective range of the driver and permitting the relative directivity of the two drivers at the crossover frequency to be evenly matched.

Moulton Laboratories :: A new loudspeaker design

Wonder how they got a patent, "if" it's not actually totally new ?

 

[freddi]

looked at those for years and Paterick Bateman's YouTube videos - another useful lens would be the old slot tweeter type such as the discontinued Selenium ST320 - it was quite even in the horizontal plane http://www.selenium.com.br/sitenovo/admin/Documentos/ST320_p.pdf

 

[Zero D]

@ freddi

That's a slot tweeter, which seems like a different concept ? Fane used to make them, & a bullit version too. I installed a number of them over the years into various systems. The slot was about 110dB & the bullit about 112dB @ 1W. The slot was a bit smoother sounding, but both were good, if xovered correctly & not over driven ! None ever burnt out. Pity they don't make them anymore.

 

[xrk971]

Sausalito Audio Works (SAW) acoustic lens is very different than Karlson aperture. It's for high frequency and acts as both a reflector optic like an off axis parabola and a diffraction lens at same time. K aperture really does provide some amazing wide dispersion. My measurements of polars of a driver behind a K aperture such as in the XKi or the Kazba are truly amazing. However, the K aperture will introduce dips and coloration. However it is not offensive.

http://www.diyaudio.com/forums/full-range/268524-xki-xs-ab-initio-karlson-6th-order-bandpass.html

http://www.diyaudio.com/forums/full-range/271011-rockin-kazba-dipole-k-aperture-z-baffle-dipole.html

 

[Zero D]

@ xrk971

Hi & thanx for posting. I realise the SAW designs are HF & reflectors etc. I just thought that the shape of the openings were similar, & if enlarged & placed over a bigger driver, it would more or less equate to a K type design, in that respect anyway.

 

[freddi]

I've love to try that lens but can't make the shallow 1/4 ellipse cavity in a good way. That cavity's depth is about 1/2 of the diaphragm's diameter - Patrick Bateman's rough mockups sound very good. Here's an old related patent
(reminds me of a urinal )

https://docs.google.com/viewer?url=patentimages.storage.googleapis.com/pdfs/US2643727.pdf

 

[Zero D]

@ freddi

1950 ! Another very old invention that got rediscovered etc

 

[freddi]

the basic idea goes back further - but 1927 is recognizable in function
https://www.google.com/patents/US1786279

 

[Zero D]

@ freddi

Amazing ! That was also reinvented in later years too