Baffle step compinsation for a sphere?

GuyPanico · 24th July 2007, 12:43 AM

How do you go about making baffle step for a sphere? I've been kicking around the idea of making a 5" sphere for a 3" driver. I know for a flat baffle you could use "the edge".

TerryO · 24th July 2007, 01:22 AM

I'm not sure you would have any real "baffle-step" at all. It may be that below whatever frequency your 3 inch driver starts to beam (wave length the diameter of the cone?) would be the corner of something like baffle step. It's a good question, it'll be interesting to see the variety of answers.

Best Regards,
TerryO

ronc · 24th July 2007, 01:29 AM

I truly dont understand the question. At what frequency do you want the baffle effect to roll in? If electronic compensation is required then its an adjustabale variable.

ron

A 5" dia sphere will roll in at around 860 hz.

pooge · 24th July 2007, 01:40 AM

If you are referring to baffle step compensation, all baffles have a baffle loss frequency, in which the baffle no longer loads the driver as a half-space. A sphere unloads faster as you go down in frequency, since it dissappears in all directions equally.

However, whether or not you need to compensate for this depends on what your lower crossover frequency is for the particular driver. If the crossover frequency is above the baffle loss frequency, then you shouldn't need to compensate for it.

Driver directivity also comes into play. If the driver is not radiating at 90 degrees off axis, then the baffle is not acoustically loading the driver. However, at the lower crossover frequency, the driver is usually radiating fairly widely.

It also depends if more than one driver is operating in the same frequency range, and they are "acoustically close" together. Each driver can provide a load to the other driver similar to a baffle.

You need to do the math. One cannot do that with the limited info you've given.

GuyPanico · 24th July 2007, 02:20 AM

Sorry for being too vague. The driver is a full range with a 150hz LR4 highpass (hivi b3n to be exact). Of course a subwoofer is incorporated for <150hz output.

As a whole, I have a weak grasp of filters and the math involved with them. Much beyond a simple cap and coil crossover is a confusing web of components to me

. However, i'm always trying to learn more.

I figured a sphere would be the easiest to create BSC for.

pooge · 24th July 2007, 05:26 AM

If you want to run these down to 150Hz then the baffle step definitely comes into play. I don't know if the frequency calculation above was for a flat baffle of 5 in size or not. If it was, I'd say a spherical baffle would cause loss above that frequency.
Think about it, the five inch width of a sphere is behind the driver.

Google baffle step and you should find the info you need. It may be easy to shelve down the high frequencies rather than boost the lower ones. Whatever you do, don't believe you have to equalize the step on axis. Baffle loss is a loss of acoustic load, which lowers the power output. I won't get into the math, but if you equalize on axis, the power output will be too high, because equalizing doen't change the load lost by the baffle. Baffle loss will cause a 6 db loss on axis. If you boost the bass up 3 db on axis, you may find this to have a flatter power response, and sound more correct.

To mitigate baffle loss, you may want to consider something other than a sphere. If you place the driver in the side of a vertical cylinder, and put a hemisphere on the top, you can get better baffle support to a lower frequency than a sphere, while pretty much keeping it pretty rigid, with the diffraction almost as low as a sphere, while making it easier to build and mount.

woody · 24th July 2007, 06:54 AM

The best article I have seen on baffel step was http://www.trueaudio.com/st_diff1.htm The
math was simple realy simple.

Svante · 24th July 2007, 06:59 PM

Quote:

Originally posted by woody
The best article I have seen on baffel step was http://www.trueaudio.com/st_diff1.htm The
math was simple realy simple.

Yes, in this particular case that page is good. The page referrs to a classical paper by Olson that actually measured the baffle step of a sphere.

What is bad about the page is that it generalises the findings from the sphere to a formula (yes it is simple, but not very accurate) based on the baffle width only.

As can be seen in the Olson images on the page a sphere has a rather smooth baffle step, which is easy to compensate for.

Resonances inside a spherical cabinet are problematic, however. But that was not the question here.

24th July 2007, 12:43 AM	#1
GuyPanico diyAudio Member Join Date: Mar 2005 Location: Euless, TX	Baffle step compinsation for a sphere? How do you go about making baffle step for a sphere? I've been kicking around the idea of making a 5" sphere for a 3" driver. I know for a flat baffle you could use "the edge".

24th July 2007, 01:22 AM	#2
TerryO diyAudio Member Join Date: Nov 2002 Location: Seattle,Wash.	I'm not sure you would have any real "baffle-step" at all. It may be that below whatever frequency your 3 inch driver starts to beam (wave length the diameter of the cone?) would be the corner of something like baffle step. It's a good question, it'll be interesting to see the variety of answers. Best Regards, TerryO __________________ "If you have to ask why, then you're probably on the right track." quote from Terry Olson's DIYaudio Forum application

Thread Tools	Search this Thread
Show Printable Version Email this Page	Search this Thread: Advanced Search

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Does open baffle suffer from baffle step?	454Casull	Multi-Way	15	19th May 2012 03:12 PM
Baffle Step Compensation	Khron	Multi-Way	4	16th April 2006 08:23 PM
baffle Step	rgrayton	Full Range	33	4th December 2004 11:16 PM
Baffle Step + Sub	Aural Dan	Multi-Way	7	9th October 2004 08:23 PM
baffle step help.	AudioGeek	Multi-Way	3	10th February 2004 11:02 AM

New To Site?	Need Help?
Register to Participate Search Privacy Statement Contact Us	Frequently Asked Questions Did you forget your password? Mark Forums Read


	Please consider donating to help us continue to serve you. Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving

24th July 2007, 01:29 AM	#3
ronc diyAudio Member Join Date: Mar 2003	I truly dont understand the question. At what frequency do you want the baffle effect to roll in? If electronic compensation is required then its an adjustabale variable. ron A 5" dia sphere will roll in at around 860 hz.

24th July 2007, 01:40 AM	#4
pooge diyAudio Member Join Date: May 2003 Location: Northern Va.	If you are referring to baffle step compensation, all baffles have a baffle loss frequency, in which the baffle no longer loads the driver as a half-space. A sphere unloads faster as you go down in frequency, since it dissappears in all directions equally. However, whether or not you need to compensate for this depends on what your lower crossover frequency is for the particular driver. If the crossover frequency is above the baffle loss frequency, then you shouldn't need to compensate for it. Driver directivity also comes into play. If the driver is not radiating at 90 degrees off axis, then the baffle is not acoustically loading the driver. However, at the lower crossover frequency, the driver is usually radiating fairly widely. It also depends if more than one driver is operating in the same frequency range, and they are "acoustically close" together. Each driver can provide a load to the other driver similar to a baffle. You need to do the math. One cannot do that with the limited info you've given.

24th July 2007, 02:20 AM	#5
GuyPanico diyAudio Member Join Date: Mar 2005 Location: Euless, TX	Sorry for being too vague. The driver is a full range with a 150hz LR4 highpass (hivi b3n to be exact). Of course a subwoofer is incorporated for <150hz output. As a whole, I have a weak grasp of filters and the math involved with them. Much beyond a simple cap and coil crossover is a confusing web of components to me . However, i'm always trying to learn more. I figured a sphere would be the easiest to create BSC for.

24th July 2007, 05:26 AM	#6
pooge diyAudio Member Join Date: May 2003 Location: Northern Va.	If you want to run these down to 150Hz then the baffle step definitely comes into play. I don't know if the frequency calculation above was for a flat baffle of 5 in size or not. If it was, I'd say a spherical baffle would cause loss above that frequency. Think about it, the five inch width of a sphere is behind the driver. Google baffle step and you should find the info you need. It may be easy to shelve down the high frequencies rather than boost the lower ones. Whatever you do, don't believe you have to equalize the step on axis. Baffle loss is a loss of acoustic load, which lowers the power output. I won't get into the math, but if you equalize on axis, the power output will be too high, because equalizing doen't change the load lost by the baffle. Baffle loss will cause a 6 db loss on axis. If you boost the bass up 3 db on axis, you may find this to have a flatter power response, and sound more correct. To mitigate baffle loss, you may want to consider something other than a sphere. If you place the driver in the side of a vertical cylinder, and put a hemisphere on the top, you can get better baffle support to a lower frequency than a sphere, while pretty much keeping it pretty rigid, with the diffraction almost as low as a sphere, while making it easier to build and mount.

24th July 2007, 06:54 AM	#7
woody diyAudio Member Join Date: Jan 2002 Location: Tyrone Ga. U.S.A.	The best article I have seen on baffel step was http://www.trueaudio.com/st_diff1.htm The math was simple realy simple.

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)