My First Measurement

**vocalmind** · **07-19-08, 12:34 PM**

Hi guys,

After reading this forum for some time. Finally, this is my first measurement though I still haven't got BFD yet, here is my setup.

1. SB Live External
2. 7.1 input (sub) on the AVR
3. Subwoofer

I guess my room has some issues or is there something wrong on the above setup?

Waterfall

1/3 smooth octave

**thewire** · **07-19-08, 07:35 PM**

Is this is a test of the subwoofer and mains together? What are the crossover or other settings on the system? It looks like your front wall corners could use some broadband absorbtion is my guess by looking at the images.

**brucek** · **07-20-08, 06:30 AM**

Quote:

I guess my room has some issues or is there something wrong on the above setup?

Looks fine.

A few tips:

1- Use LOG mode rather than LIN mode for the waterfall so it won't truncate the plot, and it will match the response plots.
2- Use a horizontal of 15Hz-200Hz graph axis for your response plots.
3- Don't use smoothing on subwoofer plots. It's use should be limited to full range measures where comb filtering may be a problem.
4- Use the AUX or CD input to your receiver with the crossover set as usual and the receiver in stereo mode, with the mains disconnected. This will offer the subwoofer measure a more realistic view through the receivers crossover, that should track the REW target line.
5- Make your measurements at 75dB.

brucek

**vocalmind** · **07-20-08, 09:35 AM**

Quote:

thewire wrote:

Is this is a test of the subwoofer and mains together? What are the crossover or other settings on the system? It looks like your front wall corners could use some broadband absorbtion is my guess by looking at the images.

Hi, it's just a subwoofer test using the SW input in 7.1 mode. i guess ill follow bruce recommendation and run a test again.

**vocalmind** · **07-20-08, 09:38 AM**

Quote:

brucek wrote:

Looks fine.

A few tips:

1- Use LOG mode rather than LIN mode for the waterfall so it won't truncate the plot, and it will match the response plots.
2- Use a horizontal of 15Hz-200Hz graph axis for your response plots.
3- Don't use smoothing on subwoofer plots. It's use should be limited to full range measures where comb filtering may be a problem.
4- Use the AUX or CD input to your receiver with the crossover set as usual and the receiver in stereo mode, with the mains disconnected. This will offer the subwoofer measure a more realistic view through the receivers crossover, that should track the REW target line.
5- Make your measurements at 75dB.

brucek

Thanks Bruce, ill run the test again. You really mean physically disconnect the mains?

**brucek** · **07-20-08, 02:21 PM**

Quote:

You really mean physically disconnect the mains?

Yep, disconnect them with the power off (of course), unless you have separate power amps, there's no other way to do it. It's not a problem - no speaker - no current....

brucek

**vocalmind** · **07-20-08, 11:14 PM**

hi, just measured using bruce suggestion. there is no diff between audessy on or off

audessy eq on

audessy eq on

audessy eq off

**bjs** · **07-21-08, 01:02 AM**

Your waterfall plots aren't displaying correctly so it looks strange. REW has a bug here (in LIN mode). You need to switch to display the waterfall plots in LOG mode to see them correctly.

**vocalmind** · **07-21-08, 02:49 AM**

Quote:

bjs wrote:

Your waterfall plots aren't displaying correctly so it looks strange. REW has a bug here (in LIN mode). You need to switch to display the waterfall plots in LOG mode to see them correctly.

eh, I can't find the LOG mode settings. Is it the one in the House Curve settings?

**JohnM** · **07-21-08, 04:04 AM**

Click the "Freq Axis" button in the toolbar, 3rd from the right. It toggles between linear and logarithmic frequency axis settings for the current graph.

**vocalmind** · **07-21-08, 10:35 PM**

Hi all, I guess i get my REW setup alright now. However, would this response be rectified using BFD? I am getting one when the paycheck comes.

**brucek** · **07-21-08, 11:19 PM**

I am quite surprised at how long the low frequencies persist. That peak at 26Hz looks like it wants to go on forever. Amazing. Could you show us the same waterfall with a 600ms time axis.

Tell us about your room and sub location. It must sound very heavy at the bottom end.

brucek

**vocalmind** · **07-23-08, 10:28 AM**

Bruce, my setup is currently in the living room, please take a look at the layout.

I am still planning to install curtain partition between the dining and living after getting the BFD.

**LarryD** · **07-23-08, 01:37 PM**

Where on the screen does it tell you which mode you are in Lin vs LOG. I see how to toggle, but I am not sure which is which. I would assume when the X Axis changes you are in LOG, true?

**brucek** · **07-23-08, 01:51 PM**

It may be a bit more obvious if you change the horizontal scale to be 15Hz-20,000Hz.

See the difference now in the horizontal divisions?

LOGARITHMIC
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LINEAR
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brucek

**JohnM** · **07-23-08, 01:54 PM**

The image of the grid on the Freq Axis button and the x axis grid spacing on the graph show the current setting, when the vertical lines are evenly spaced the axis is linear, when they are closer together at the right it is logarithmic.

**LarryD** · **07-23-08, 04:24 PM**

Thanks

**vocalmind** · **07-24-08, 08:14 PM**

Quote:

brucek wrote:

I am quite surprised at how long the low frequencies persist. That peak at 26Hz looks like it wants to go on forever. Amazing. Could you show us the same waterfall with a 600ms time axis.

Tell us about your room and sub location. It must sound very heavy at the bottom end.

brucek

Hi, this is the waterfall with 600ms time range. The dips and peaks could be due to the room where there is an open space on the left (dining). I was wondering if this can be minimize with a curtain.

**vocalmind** · **07-25-08, 12:36 AM**

i made some re-arrange

1. place the sub beside the FR.
2. disable audessy EQ - somehow it distorts around 45 to 60 hz
3. manually set the speaker level to 75db and sub to 80 db
4. set the sub to 60hz crossover
5. run test (mains and sub)

6. set PEQ on the subwoofer to cut the 43hz to 57hz peak
7. run test

am i still missing something? i guess the peak on the 20hz to 30hz will be corrected with BFD.

**brucek** · **07-25-08, 06:41 AM**

Quote:

am i still missing something? i guess the peak on the 20hz to 30hz will be corrected with BFD

Looks good. Yeah, just carry on and see what can be accomplished with a BFD...

brucek

**vocalmind** · **07-27-08, 09:23 AM**

Just got a BFD 1124P and playing with the filters.

Just a quick question, why there is no AUTO EQ Filters for the BOOST on the REW?

**brucek** · **07-27-08, 10:51 AM**

Quote:

why there is no AUTO EQ Filters for the BOOST on the REW?

I don't understand the question. Can you rephrase it?

brucek

**vocalmind** · **07-28-08, 08:34 AM**

eh, i found no filter for boost on this pop-up. the filters are meant for peak only.

**JohnM** · **07-28-08, 09:37 AM**

"PK" refers to the type of filter, a parametric biquad often called a "peaking" filter. Whether it has cut or boost is determined by whether the filter's gain is positive or negative. If you assign a filter or two and play with their settings whilst watching the resulting response on the REW graph you will get a feel for what they offer.

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