Some crossover/filter stuff

billcu

billcu

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Staff member
I know we have beaten this to death on another thread.:D

I thought I'd show some testing that I did with my speaker using a sound level meter, software, and some pink noise, for anyone that might be interested.

The meter was set to measure 1/3 octaves (1 octave = a doubling of frequency).

My speakers have 5 drivers and 2 ports. The subwoofer and it's port are separated from
the rest of the enclosure. There are 3 drivers on the top, a tweeter, midrange and mid bass.
You can see at 315 Hz the sound coming from the top.

The front has the subwoofer, its port, the mid bass port, and another tweeter.

I measured the sound at each of the grid points marked on the speaker with peices of tape.

It would have been better if I used more points, but this was just a quick excersize in mapping.

The software lets you see each 1/3 octave by using the arrows in the graph control. The level is shown by color, red being the highest.

Here's a few screenshots at different frequencies:
 

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Yes, you can map any square or rectangular grid from a room to a neighborhood.:)
 
It's a program that works with our meters that we sell where I work.

Without trying to turn this into an advertisement, the program is called DNA, Data Navigation and Analysis.
 
No thanks Bud, I just posted this to show the crossovers in action.:)

Besides, I don't want to have to ban myself.:D
 
Of course you're right Bud.:)

You're still in our database at work.:D

By the way, we just released the new Audit program, and some of your feature requests were put in it.:wave:
 
There's not a lot to it. The meter and software do most of the work.

The pink noise has equal sound levels at all the 1/3 octave frequencies.

I measured the noise at all the points marked by the tape, the grid points, one point at a time. Each measurement is stored separately, and sorted out by the software.

Each measurement contains the levels of all the 1/3 octave frequency bands at that point. An example would be my subwoofer port is loudest at the lowest frequencies (ports usually reproduce lower frequencies than the front of the speaker that they are porting).

The software lets you look at the sound levels of all the points at once, and you can select the single frequency band that you want to look at. You are looking at the sound levels of a specific 1/3 octave band frequency at all the points together.

The higher levels, shown in red, show you what speaker has the highest output at that frequency band.

The software also "smooths" the differences between the points, creating the curved contours.
 
Sorry Bill, I'm still totally confused. Me have street smarts no book smarts. LOL!

Looking at the second picture, the red is coming from the subwoofer although the hertz says 160 (highs/tweeters?). That's confusing to me because the sub's output should be only low hertz, right? :confused:
 
That is the correct frequency.

I'll have to check for the exact frequency, but the crossover is at around 200 Hz for this system.

I can send anyone all the data and a reader if you want to see all the frequencies (I only did up to 10 KHz).
 
Wirelessly posted (Mozilla/5.0 (iPhone; U; CPU iPhone OS 4_0_1 like Mac OS X; en-us) AppleWebKit/532.9 (KHTML, like Gecko) Version/4.0.5 Mobile/8A306 Safari/6531.22.7)

Gah, WTF is CPS?
 
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