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Discussion Starter · #1 ·
I've just stated trying to learn how to use Room EQ Wizard. I've calibrated the sound card and set levels but when I go to measure the sub, graph looks way different than I expected. Please see the attachment.


The sound card is plugged directly into the DSP1124p. What am I doing wrong?

TIA!

Kristi


PS: Largest peak found was 27.7 dB
 

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The measurement looks OK. As you are plugged directly into the sub via the 1124P the effective roll-off will be much higher than if going through a receiver, which is why the output isn't dropping like the target curve. You can try setting the target cutoff frequency to its highest value or use a flat target. Also worth changing the graph scales to the 15..200Hz and 45..105dB defaults. Is your sub next to a wall or in a corner? If not, putting it in a corner should help lift the low end somewhat.
 

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graph looks way different than I expected.
As John says, your graph axis is not correct. Axis can exaggerate and distort a response so it's almost unreadable.

Set vertical to 45dB-105dB and horizontal to 15Hz-200Hz and it will look like you expected. :)

To set the scale, use the Graph Limits icon in the top right hand corner of REW. Once you enter the limits, they will be there the next time you pop up the icon.

brucek
 

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Kristi, I'm not sure if everyone here is familiar with your hardware (it's been a while) - are you still using the 4 -18" Mach-5 mj-18's in an IB and the EP-1500 Berhringer?
 

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Discussion Starter · #5 ·
Thanks for the suggestions, I'll adjust the axis tonight.

Bent was right (thanks Ben!) about my hardware (4 -18" Mach-5 mj-18's in an IB and the EP-1500 Berhringer?) The IB is in-wall, centered below the screen.

I thought that perhaps the reason for the highest peak @ 27.7 dB might be because of the built in filters on the DSP1124? I haven't done anything with the EQ...just plugged it in and set the bottons on the back to -10dB.
 

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I thought that perhaps the reason for the highest peak @ 27.7 dB might be because of the built in filters on the DSP1124?
Press the IN/OUT button on the BFD front panel and the Green LED will go out. This bypasses all filters.
 

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Discussion Starter · #7 ·
Okay, I'll re-run the test when I can and make sure the IN/OUT LED is off. then I'll adjust the axis and repost. Thanks for the suggestions so far! Might have to wait until the weekend tho... stay tooned!:nerd:
 

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Discussion Starter · #8 ·
one more question before I re-run the test. Would it be better to go through the Reciever than connecting the sound card straight to the EQ?
 

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one more question before I re-run the test. Would it be better to go through the Reciever than connecting the sound card straight to the EQ?
Yes, because then you will have the receivers crossover activated. Be sure that the receiver is in the stereo mode with no effects or soundfields on.

Best to disconnconnect the mains and do a sub only measure first. After EQ, add the mains and test for integration of the sub and mains at the crossover area.

brucek
 

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Discussion Starter · #10 ·
After implementing all the suggestions you all made, here is my new measurement. Is this a little more normal?...now I just have to read the help file and figure out the next step.
 

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Discussion Starter · #11 ·
Okay, I'm not really sure how to progress from here. The REW help files tell me how to use the midi interface to program my BFD, but not having a midi interface, what is the next step? I've found the peaks and assigned filters in REW, optimized PK Gain and Adjusted PK Gains. Where are the numbers that I need to program the BFD manually?
 

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Hello, your frequency respomse below 40hz seems problematic to me, considering you have 4x18 inches drivers and a good amp. Is it possible that some of your driver are not well connected ? I meen in phase ? I do not know much about Infinite Baffle so all input from other shackster will be useful.

JP
 

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Discussion Starter · #14 ·
Thomas from Cult of the Infinately Baffled has given me some pointers and here is my latest measurement.


How do I take this data and turn it into filters for the BFD? Is this what "Find Peaks" in REW does?
 

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I'd start at the ugliest peak - 50 Hz, apply a 10dB cut 1/10 octave BW, and re-plot it, just to get a feel for how the BFD affects change. You may miss it entirely, or you may see a marked improvement.
 

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To me that looks like pitiful low end response... no disrespect to your sub, but what sub do you have and where is it located?
 

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Discussion Starter · #19 ·
Its an Infinite Baffle Sub (4 -18" Mach-5 mj-18's, Berhringer EP-1500 amp, DSP1124) The IB is in-wall, centered below the screen.

Does this look better?

Turns out the Amp had a low cut filter I had to turn off.
 

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Yeh ! Much better for the 10 to 30 Hz range!

It seemed very strange to me that you do not have a good output in that range... That's why I asked you is the 4 drivers are in phase.. I did not think about a low pass filter because I do not have one on my amps.

But now your graph is more "normal" and you just have to apply some filters on the big peaks. The 50 - 60Hz zone seems to be the critical zone. You should lower that. I would also try a little "boost" in the 30 - 35 Hz area but remember to not add more than a few dB.

Have fun!

JP
 
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