Modifying a B2031P

[dantheman]

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:


and the average of the polar:

Vertical polar toward the woofer in 11.25 degree steps:

11.25 degree steps toward the tweeter:


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

Dan

[dantheman]

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!




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:


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

[dantheman]

Yea, Dr. Geddes measurements look more like my first. Could those ports be causing a diffraction problem?


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


Spectrogram comparisons from REW Beta5:




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.


Dan

[454Casull]

Where did you get 4 for $304 shipped?

[dantheman]

Zzounds. Sorry, never saw the reply. Low price guarantee and B&HPhoto had them cheap.

Dan