trying my new cm140

[al bundy]

Here is a graph I made with my new cm-140. I used a test tone CD going from 15 to 120 Hz.



Just curious how this looks and if you think I will need to get a BFD or not? Are the bumps in the 30-40 Hz range and around 80-85 Hz going to make it boomy? I will try REW once I get my cables/connectors in the mail on Wednesday. I just had to play with my new toy!

[Wayne A. Pflughaupt]

al bundy wrote:

Just curious how this looks and if you think I will need to get a BFD or not? Are the bumps in the 30-40 Hz range and around 80-85 Hz going to make it boomy?

Well, between 75 Hz and 83 Hz, response rises about 14 dB. Response at 35 Hz is about 10 dB higher than on either side of it (25 and 55 Hz). I’d say that’s significant enough that EQ could make an audible difference. Then there is the house curve issue. Definitely will need EQ to accomplish that...

Regards,
Wayne

[brucek]

curious how this looks

Your scaling needs some work. You have changed scale part way through the horizontal axis and your vertical scale is too large.

Go to the download page and get the CM-140 calibration file and use the values to correct your readings. (open the cal file with notepad to reveal the text values).

Then take a look at the graphs in this manual measurement excel file for a Radio Shack meter. Use the same values for your graph scaling. The scaling is in octaves (how we hear) and it will be a better representation of how you hear your subwoofer.

brucek

[al bundy]

Thanks for the links. Not sure if this is correct, but here is my last effort before I try REW sometime tomorrow ... disregard below 16 hz and above 120 hz . First graph must have been way off.

[brucek]

Yeah, you have a peak at 40Hz for sure, but wait until you get REW running before doing anything drastic.....

Read and become familiar with the REW HELP files and the REW Cabling and Connections Basics.

Also note the REW information Index and the Download Page.



brucek

[al bundy]

Quick question ... Do I use the A or C on the 140, and do I check the C weighted in REW?

thanks

[JohnM]

Use C weighting, and do check the C weighted SPL meter box.

[al bundy]

Ok, got REW going finally. Here is one of my measurements



No matter where I move the meter, there is always the peak at 40 Hz, and there is a null at around 75 that gets worse the farther I move away from the left side of the couch. The right side of the couch will drop down to 46 dB around 75 Hz even if I move the crossover to 150. I will try and move the sub tomorrow (only 2 other places it can go).

Btw, should there be any smoothing applied when posting? I didn't with these.

[al bundy]

Here is an example with the meter at the right side of couch with the BIG dip at 70 Hz. I even bumped the crossover to 100 Hz.

[brucek]

there is always the peak at 40 Hz, and there is a null at around 75

Not uncommon for a peak (such as the one at 40Hz) to be persistent through the room. It requires a parametric equalizer to remove it. I wouldn't worry about the 75Hz dip until I added my mains and take a look to see if they correct the dip. I would leave the crossover at 80Hz and add the mains and do a measure. Then use the phase control on the sub to smooth the crossover area.

Post graphs with a horizontal scale of 15Hz-200Hz.

brucek