Seen any driver beaming studies?

cuibono · 03:15 PM

I'd like to be able to see where different size drivers start beaming, and at what point it becomes 'severe'. I've noticed that it starts gradually, but then changes more rapidly, hence my wanting to see actual data. My ideal set of info would show me a 10" driver, an 8", 6" and 4", at angles up to 90deg off axis (all done by the same person). Sometimes mfrg datasheets show a couple of angles, but that isn't enough to do a good comparison.

I'd like to cut a hole in the side of my house, and do it myself, but I don't think that would be 'allowed'. Maybe the roof?

EDIT: maybe it needs stating - measurements should be on an 'infinite' baffle

Robh3606 · 20th November 2009, 04:06 PM

There are old nomographs for the -6db point based in driver diameter. You can also do simulations in some software as well. The first attachement is an old JBL graph the second an 8" JBL 2118 directivity graph generated in LEAP

Rob

Pano · 20th November 2009, 06:35 PM

Thanks for the nomographs, Rob. There was also an Altec paper from the 70s (IIRC) that talked about this. Can't find it tho...

cuibono · 20th November 2009, 07:13 PM

Yeah, thanks, that is useful. I wonder to what degree it is accurate?

Saturnus · 20th November 2009, 07:17 PM

Robh, I think the nomograph along with many other studies is NDA from JBLs development department.

Robh3606 · 20th November 2009, 08:20 PM

Quote:

Rob. There was also an Altec paper from the 70s (IIRC)

Not sure if this is the same one, thanks for reminding me. I have several of these I downloaded a couple of years ago.

Rob

Directivity - Lansing Heritage Forums

Ron E · 20th November 2009, 10:21 PM

Google for ARPE - Asymmetrical Response Pattern Estimator

cuibono · 20th November 2009, 11:23 PM

Lots of good info, thanks! I've realized SoundEasy also does polar pattern prediction.

Pano · 20th November 2009, 11:29 PM

Yes Rob, that's the one. Altec Technical Letter no. 237.
Thanks for finding it!

J.R.Freeman · 21st November 2009, 12:12 AM

A bit off topic, but what are the reasons for avoiding 'beaming'?

When I first started here, I asked about a 2 way design with an 8 inch midbass, and beaming was sighted as a possible issue. I've heard mention of off-axis response suffering from this phenomenon, and that can erode imaging, is that correct?

I'm confused as some call 12 inch drivers as 'mid-bass' and sight the narrowed dispersion as a positive. Is this a case of two different system goals and two schools of thought?

Jim

20th November 2009, 03:09 PM	#1
cuibono diyAudio Member Join Date: May 2006 Location: City of Angles	Seen any driver beaming studies? I'd like to be able to see where different size drivers start beaming, and at what point it becomes 'severe'. I've noticed that it starts gradually, but then changes more rapidly, hence my wanting to see actual data. My ideal set of info would show me a 10" driver, an 8", 6" and 4", at angles up to 90deg off axis (all done by the same person). Sometimes mfrg datasheets show a couple of angles, but that isn't enough to do a good comparison. I'd like to cut a hole in the side of my house, and do it myself, but I don't think that would be 'allowed'. Maybe the roof? EDIT: maybe it needs stating - measurements should be on an 'infinite' baffle __________________ double complete rainbow all the way!! Last edited by cuibono; 20th November 2009 at 03:15 PM.

20th November 2009, 07:13 PM	#4
cuibono diyAudio Member Join Date: May 2006 Location: City of Angles	Yeah, thanks, that is useful. I wonder to what degree it is accurate? __________________ double complete rainbow all the way!!

20th November 2009, 10:21 PM	#7
Ron E diyAudio Member Join Date: Jun 2002 Location: USA, MN	Google for ARPE - Asymmetrical Response Pattern Estimator __________________ Our species needs, and deserves, a citizenry with minds wide awake and a basic understanding of how the world works. --Carl Sagan Science is a way of thinking much more than it is a body of knowledge. --Carl Sagan

20th November 2009, 11:23 PM	#8
cuibono diyAudio Member Join Date: May 2006 Location: City of Angles	Lots of good info, thanks! I've realized SoundEasy also does polar pattern prediction. __________________ double complete rainbow all the way!!

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20th November 2009, 06:35 PM	#3
Pano diyAudio Moderator Join Date: Oct 2004 Location: North Carolina Blog Entries: 4	Thanks for the nomographs, Rob. There was also an Altec paper from the 70s (IIRC) that talked about this. Can't find it tho...

20th November 2009, 07:17 PM	#5
Saturnus diyAudio Member Join Date: Jun 2005 Location: Copenhagen, Denmark	Robh, I think the nomograph along with many other studies is NDA from JBLs development department.

20th November 2009, 11:29 PM	#9
Pano diyAudio Moderator Join Date: Oct 2004 Location: North Carolina Blog Entries: 4	Yes Rob, that's the one. Altec Technical Letter no. 237. Thanks for finding it!

21st November 2009, 12:12 AM	#10
J.R.Freeman diyAudio Member Join Date: Aug 2008	A bit off topic, but what are the reasons for avoiding 'beaming'? When I first started here, I asked about a 2 way design with an 8 inch midbass, and beaming was sighted as a possible issue. I've heard mention of off-axis response suffering from this phenomenon, and that can erode imaging, is that correct? I'm confused as some call 12 inch drivers as 'mid-bass' and sight the narrowed dispersion as a positive. Is this a case of two different system goals and two schools of thought? Jim

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