cruzmisl

Hi Mark, I finally got around to taking a measurement of my SubMersive1 with REW. I think I did it right but I took it bypassing the QSC30 because I don't know how to work it. Anyway, what do you think it looks like? Does it look correct? Any tips on the QSC would be really appreciated.
Thanks Mark.
Joe




PS I took this measurement with the 850's and Submersive going through my MMC-1. I unhooked the speakers and got a similar response. I then changed the crossover freq. to 160Hz and still got a similar dip at 80Hz.......weird. 
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Mark_Seaton
Hi Joe,

The response you see does look plausable.  The SubMersive is in a somewhat similar location front to back as the main speakers, so the common dip is possible.

I would suggest moving the microphone significantly, and then maybe right in front of one of the SubMersive's drivers.  You should see the response change with location if you are getting useful measurements.  Also simple things like raising and lowering level by a known amount on your receiver or the subwoofer will give you more points to insure you are measuring what you think you are measuring.  Always a good thing!

For reading the graphs, personally I like to see the increments at ~5dB/division instead of the default 8dB/division, but the same info is there.

I'll post a "starter" DSP-30 file here which you can download and modify as needed.
Mark Seaton
Seaton Sound, Inc.
sales@seatonsound.net
773-290-8436
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Mark_Seaton
Attached is the DSP-30 Config file I mentioned above.

Starter File for DSP-30

More later...
Mark Seaton
Seaton Sound, Inc.
sales@seatonsound.net
773-290-8436
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cruzmisl
Thanks Mark! Looking at the file it's clear I have no idea what I'm doing. Anyway, here is a curve with the mains and subwoofer with the polarity (-). Smoothed out the 80Hz dip quite a bit.


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Mark_Seaton
Hi Joe,

For a quick overview, the basics of the filter settings are as follows:

Start by double clicking on the EQ block.  This will pull up a window for entering the parameters for each filter.  One "EQ" block can hold up to 8 parametric filters.  I have already added all 8 filters to the block in the starter file as there is plenty of DSP power to spare. 

While it is not a very detailed display, if you click "Show Response" at the bottom of the parameter window you will see a graphic representation of what you are doing to the response with the filters.  This display is more useful as a guide and indicator of what you are doing than an exact design read out.  You want to be looking at the "Magnitude" tab for the most part.

At the top of this window you will see tabs for the first of the 8 filters simply labeled "EQ" with 2-8 being numbered.  Each filter is controlled separately.  Once you enter some filters that cut or boost (+ or -dB gain), the response window to the right will show both a yellow curve and a blue curve.  The yellow curve indicates the filter currently have selected which will be controlled by the input values on the left.  The blue curve is the combined response of all active filters.

There are two "BYPASS" buttons.  The lower "BYPASS all EQ's" button bypasses all of the filters in this block (filters 1-8).  It does not affect other blocks or controls that will come up in separate control windows.  The "BYPASS" button below the Q Factor box only bypasses the filter currently showing in the tabs at the top.  These different bypass buttons are useful in allowing you to turn on and off filters to measure the response before and after, insuring that the filters are doing what you expect them to.

Freq, Gain & Q Factor:

Freq defintes the center frequency of the filter.  This is the peak of the cut or boost.

Gain defines if the filter raises or lowers the level and by how much at the center frequency.  Play around a little and this will make more sense as you watch the response window to the right.

Q Factor defines the width of the filter, or how broad or narrow the Gain is in frequency.  Low Q = wide & broad.  High Q = very narrow or sharp.

As an exercise, with the response window open on the right, set filter 1 and filter 2  at a frequency of 100Hz.  Now set both filters to a gain of -10dB.  As explained in my notes on the screen, when you first enter numbers, they will show up RED.  Until you press ENTER (Return), they will not be effective, and clicking another window before pressing enter looses the entry.  Now that you have this entered, set filter 1 to a Q Factor of 1, and set filter 2 to a Q Factor of 10.  Observe the shape of each. 

Now change the Gain of each filter to -3dB and see how the shapes change for the same Q Factor.

I haven't used Room EQ Wizard in a while, so I'll have to see how it specifies filters.  There should be some mode that gives you recommended filters in "Q" instead of the fractional octaves that Behringer uses.  The RDES filters are somewhat similar in entry form, but the DSP-30 allows many more filters plus some others.

One recommendation is to not do your measuring in stereo mode.  Use a Dolby ProLogic or ProLogic II movie mode.  If you have a stereo signal to send your pre-processor, in this mode the same signal to L & R inputs results in sound coming out of the center channel and subwoofer.  You can then separately test the left & right speakers by disconnecting one or the other input.  You will avoid odd noises if you keep one connector always connected.

That should help you get on your way, and I think you will find some useful results between help here and at Home Theater Shack.

Enjoy!
Mark Seaton
Seaton Sound, Inc.
sales@seatonsound.net
773-290-8436
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