Modifying a B2031P

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The Behringer B2031P, as I've measured it, looks great on paper. A friend from work kept telling me this speaker really sounded accurate. I honestly thought that by accurate he was talking about a typical monitor speaker. He's mentioned this about 5 times or so at work so I finally went to his house for a listen after seeing Dr. Geddes measurements of a Behringer monitor on his Preview Data Program. After listening I brought the speaker home for some measurements. Set the mic for midway between the MW and tweeter and got this:
behringer2031ppolar.jpg

behringer2031pimp.jpg

and the average of the polar:
behringer2031pavg.jpg

Vertical polar toward the woofer in 11.25 degree steps:
4vw.jpg

11.25 degree steps toward the tweeter:
b2031polarstweet.jpg


Looked good so far. I returned the speaker satisfied by the results.

Dan
 
Impressed I returned to work confirming his ear. Another friend wanted some small HT speakers and I wanted a pair as well, se we ordered 4 for $304 shipped!
4polar.jpg

3polar.jpg

2polar.jpg

1polar.jpg

The top 2 were 1 pair and the bottom 2 another. This time I had the mic height in the center of the tweeter. The typical impulse looked like this:
1imp.jpg


The pairs matched each other well, but both the impulse and polar graph looked worse than what I measured from my buddy's even though the speaker sounded the same to my ear.😕

I returned to the Preview Data Program......

Dan
 
Yea, Dr. Geddes measurements look more like my first. Could those ports be causing a diffraction problem?
An externally hosted image should be here but it was not working when we last tested it.


Well. I went to the wife's make up drawer and nabbed some cotton balls and stuffed those ports closed. Here's what happened:
cottonpolar.jpg

cottonimp.jpg

Spectrogram comparisons from REW Beta5:
90spectronocotton.jpg

90withcottonspectro.jpg

onaxiswithcottonspectro.jpg

spectronoctnonaxis.jpg

Sorry about the extra noise in the spectrogram with the cotton balls stuffed in the ports. You can see in the impulse that the first reflection is a touch earlier and thus the contamination of the graph--well technically all graphs. Well I'm starting my own cotton ball product called "Diffraction B Gone"(that's a joke).

Well, what happened to the bass after that?
I took this 2 ft from the speaker both ways. The one with the slightly less bass has the cotton balls in it. Buy subs people.
2ftcottonvsprted.jpg


Dan
 
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