Flower Baffle - Any Effect?

[jjasniew]

I had the chunks of cut-out from my 18's, so I decided to try a rudimentary flower baffle on an fe103en.

The Edge says I should get a nice null between 1 and 2 k, with a circular baffle. I was hoping the petals would defocus the circular edge effect.

Measuring indoors with REW (using the frequency dependent window option checked), I get much less "sharpness" in the null.
Is this because of the flower shape, or the frequency dependent window analysis preference?

I have it set on a carpeted floor with the mic 1M away, on a cushion (pic for clarity, not distance)

How can I improve my measurement certainty - besides "I should have measured the baffle when it was circular first", which I realize. Thanks!

 

[perceval]

Since you will never have your head stuck on a pillow on your carpeted floor, I'd suggest getting a stand for your mic, and placing the driver at ears height when seated on your favorite chair.

Unless you do enjoy listening to music while laying on the floor...

 

[jjasniew]

I've seen pictures of "ground plane" and hear of someone making "bed plane" measurements here. I thought it was a legit way to measure a speaker when outdoors / anechoic isnt available. I'm most interested in the effects of the jagged circular baffle edge and if it's a useful design.

 

[AllenB]

Yes, but ground plane suggests a hard reflective surface. It might be tempting to make it absorptive.. the reflector could be resonant, the mic might not get close enough to the reflective surface even if it touches it.

Anyway, doing this at half room height should be reasonable at these frequencies if you can gate, which you should anyway for ground plane measurements indoors.

 

[bansuri]

Use the other cutout to mount the speaker offset the center and compare.
The measurement looks awful with the 20dB dip

 

[perceval]

I've seen pictures of "ground plane" and hear of someone making "bed plane" measurements here. I thought it was a legit way to measure a speaker when outdoors / anechoic isnt available. I'm most interested in the effects of the jagged circular baffle edge and if it's a useful design.

So many people can go to great lengths to make sure the data matches their conversation. They try to tweak the parameters of measurements to get the data they are expecting and willing to share.
When it gets translated into real world situations, it is nowhere near the posted data.

Plus, you are looking at the 1-2kHz spot, being dependant of the baffle shape, and not the floor. So, if you want to study the effects of the flower shape, you need it to get away from other surfaces. Otherwise your data is tainted and unrealistic.

 

[Mattes]

Hi Joe,


The reason behind the flower baffle is of course to have different path length from front to back, in order to "smear" the geometrical resonance of a circular baffle, while maintaining symmetrical directivity vertically and horizontally.
Sorry to say that the path difference in your experiment is quite small, so the difference between your flower and a circular baffle might be difficult to measure.

But it´s of course an interesting experiment. I may suggest to have the sharp edges well-rounded as well, and have the difference measured...


All the best


Mattes

 

[scottjoplin]

Or make a torus

 

[jjasniew]

Ok, I put the flower baffle atop a 35" stand and set the mic ~1M away, on a tripod 45" above the floor. In the middle of the room. Using the frequency dependent window option checked. Here's what I got.

There's still the dip as predicted by The Edge. If I were to do over, I'd have offset the driver to help mitigate that.

The ratio of this flower petal baffle to the driver diameter is perhaps excessive; It may work better with a larger speaker. I have 5"s and 8"s to yet model and try.

 

[jjasniew]

>Or make a torus...

Stuff feels nice and soft, certainly malleable, about the right size. Cheap. But I can only imagine the sticky mess...

A quick look at an 8" driver in Edge, with and without an 8 "petal" perturbation around the circular baffle shows me a "meh" 1 db difference. I think I'll stop here.

It's been fun and got my REW setup workin' in the context of at least I know how to connect the cables, setup the DUT, mic - and what buttons to push.

 

[Juhazi]

Interesting thread! Wintertime indoor play. Please take some off-axis measurements too, eg. 30/60/90 deg and backside as well. Post #9 response looks like I imagined to.

 

[scottjoplin]

I've wondered if a torus needs to be round to be effective, in fact square would give more distance variation and still give almost symmetrical radiation. Certainly be a lot easier to construct.