# My first attempt at REW EQ ( post Audyssey EQ XT)



## sportflyer (May 2, 2010)

Here is my first attempt at Subwoofer EQ with REW . This was done after I have used Audyssey EQ XT. 
The filter values were entered Manually into the BFD. Its actually quite easy to do after some practice.

The first chart is the Freq response BFD in Bypass mode









The second is Freq Resp after applying 4 filters between 20 hz and 70hz









The following two charts are the waterfall charts ( before and after applying filters)



















I think I made some progress , not perfect. However bass is definitely more controlled and tighter .

Now I dont need to offset Audyssey by 10 db to eliminate the overly bloated bass. 

Any comments would be much appreciated.

Tks


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## Wayne A. Pflughaupt (Apr 13, 2006)

Looks good. :T

Regards,
Wayne


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## sportflyer (May 2, 2010)

Wayne A. Pflughaupt said:


> Looks good. :T
> 
> Regards,
> Wayne


Wayne, Should I do anything about the response in the 80 to 150hz region? I left it out thinking that Audyssey will take care of it. Maybe I should to a freq resp chart with the main speakers connected . Is the RS SPL meter accurate enough to say 1Khz? 

Why is it that my Sub response does not roll off that much beyond the xover point? Obviously I can increase the Target level to about 80db. 

When I tried to do this , ie change it manually to 80db , then click of the set target button, it returns a Target level of 75.2 db? I don't understand this .

Tks


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## sportflyer (May 2, 2010)

I am confused about equalizing around Target Levels . 

What is the difference between adjusting the filters to match the 75db default Target curve vs setting the Target Curve level first to best match the raw measured freq response then adjusting filters. In my case this is around 80db Target not 75db ( see fig 1)

Does the EQ hold for all playing volumes or it best matches the measured curve only when playing at the Target volume ?


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## JohnM (Apr 11, 2006)

The target level should be adjusted to match as far as possible with the measured response, otherwise you would end up trying to use filters as volume controls. The EQ is valid for any volume setting.

How are you feeding the test signal to your sub? there does not appear to be any crossover in the path (or a main speaker was also playing), in either case you should change the target shape to Full Range to get a flat line, rather than Subwoofer which shows the response of a crossover filter.


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## Wayne A. Pflughaupt (Apr 13, 2006)

> Why is it that my Sub response does not roll off that much beyond the xover point?


Good question, it appears you don’t have any kind of crossover on the sub. It’s something you should look in to. Check your receiver’s bass management menu settings. We’ve seen in the past that some receivers only engage the sub crossover with Dolby Digital programming.




> What is the difference between adjusting the filters to match the 75db default Target curve vs setting the Target Curve level first to best match the raw measured freq response then adjusting filters. In my case this is around 80db Target not 75db ( see fig 1)


As John noted, if the response curve is too far above the Target, the program will “over-equalize” beyond eliminating peaks, to bringing the overall level down to the Target. So, the equalizer is functioning as a level-adjustment device in addition to smoothing response. 

Regards,
Wayne


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## laser188139 (Sep 19, 2009)

sportflyer said:


> ... Why is it that my Sub response does not roll off that much beyond the xover point? Obviously I can increase the Target level to about 80db.
> 
> When I tried to do this , ie change it manually to 80db , then click of the set target button, it returns a Target level of 75.2 db? I don't understand this ...


My guess is that you were driving your front speakers at the same time as your sub, and your graph is the overall combined response. So naturally it does not fall off. This would also explain some of the elevation in the sub region, from the two channels adding together there. Some receivers have a convenient Front A/Front B switch, and if you select Front B instead of A, without any B speakers connected, this conveniently disables the front speakers so you can graph the sub alone, with its rolloff. If yours doesn't have this, you may need to unplug the front speakers either at the receiver or the speakers themselves to measure the sub alone. 

Once you remove the front speakers from the graph, you may find that REW calculates a different average target level when you click Set target level on the sub graph alone. You can coerce the target level yourself by changing its value manually, but the choice calculated by REW through Set Target Level is probably the better starting point. 

Bill


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## sportflyer (May 2, 2010)

Heres how I am feeding the system.

The UCA202 output is connected to right channel of analog CD input and only stereo is used ( so no center and surrounds are engaged) . I disconnected the main speakers at the receiver outputs so only the sub is working. I had to increase the sweep output to -4 db from the std -12db to get the correct levels within range at the check levels stage.Could this be the problem of a very high measured response vs the 75 db target curve? 

How to change shape of Target level to flat? 

BTW Audyssey dynamic EQ is engaged during the measurements. Is this a problem?


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## laser188139 (Sep 19, 2009)

sportflyer said:


> ... BTW Audyssey dynamic EQ is engaged during the measurements. Is this a problem?


Yes, that would be an issue, too. You want to calibrate Audyssey and the BFD to flat without DynEQ, then enable DynEQ later during listening to adjust the response to maintain the perceived levels at lower volume levels. 

Or, if you wanted to leave DynEQ off all the time, you could use the BFD to equalize to your own house curve. That would be a totally different approach. I've been satisfied with how DynEQ works. 

Either way, you want it off during your REW measurements, unless you are studying the effects of DynEQ itself. 

DynEQ explains the elevation at the low end, but doesn't explain how flat your response is at the high end. If, as you say, the main speakers were disconnected, then perhaps the crossover in the receiver is set very high. There's nothing wrong with that, you can equalize the sub to as high a frequency as you like, but you do want to set the crossover frequency in REW to match the crossover frequency setting in the receiver. If you are running in Stereo mode, you may have set a stereo-only configuration different from your multichannel configuration, with its own crossover setting. 

Bill


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## sportflyer (May 2, 2010)

I found that in stereo mode, even the front and surrounds were active because the receiver was in all ch stereo . I changed it to pure stereo audio so no more output except from the subwoofer. I then made another measurement . It looked a bit better but low end was still high due to Dynamic EQ was on as suggested above. I will shut it off and try again. 

BTW all Xovers were set at 80 hz .

I now encounter a new problem , the generate waterfall function seems to hang up on me with the new curves. It says processing then it does not progress. Did I do something wrong in the measurements to cause this ?


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## JohnM (Apr 11, 2006)

Try setting the waterfall frequency axis to log (it is linear in the plots above).


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## sportflyer (May 2, 2010)

JohnM said:


> Try setting the waterfall frequency axis to log (it is linear in the plots above).


You are correct I can easily toggle freq axis to log .


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## sportflyer (May 2, 2010)

OK guys , I found the problem with my response curves. 

a) Dynamic EQ was on 
b) The most important factor was that I cannot use stereo mode. I have to use all Channel Stereo and disconnect F. L . C, SR, SL speakers and only leave the Sub output connected.


















Now it looks more like what you guys show 

I will post waterfall charts later


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## sportflyer (May 2, 2010)

I have started to play with Beta 5 version . Took me a while to find the appropriate controls. EQ program is very nice. I have two questions:

a) Individual max boost ...is this the max allowed +gain for each filter 

b) Overall max boot ......is this the max aggregate boost allowed for all the filters used ?

Is it safe to allow +12 db max gain for individual filters ( default value) ? I thought it might lead to sub overload and distortion? 

Tks


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## JohnM (Apr 11, 2006)

sportflyer said:


> a) Individual max boost ...is this the max allowed +gain for each filter


Yes



> b) Overall max boot ......is this the max aggregate boost allowed for all the filters used ?


Yes, though depending on the particular combination of filters there are circumstances where the figure could be exceeded.



> Is it safe to allow +12 db max gain for individual filters ( default value) ? I thought it might lead to sub overload and distortion?


Yes, it is safe, subject to the overall gain limit. The sub does not see the effect of any individual filter, only the combined effect of all the filters. As long as overall gain is not excessive there are no headroom issues, you can use the "Filters" plot to see the overall effect.


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## sportflyer (May 2, 2010)

Thanks. Now I feel safer to use the new filters generated by V5. The V5 fillter optimization algorithmis very good. TKs for a great program . 

Is is it OK to use the measurement data from Ver4 and derive the filters using Ver 5? It saves me from rehooking up the laptop, mic etc again to make another measurement .


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## JohnM (Apr 11, 2006)

sportflyer said:


> Is is it OK to use the measurement data from Ver4 and derive the filters using Ver 5?


Absolutely. Best to load up the same cal files in V5 before you open the measurement, otherwise you will get a prompt that the cal files are needed. If you save the measurement from V5 (after loading the cal files) they get included in the measurement file.


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## sportflyer (May 2, 2010)

Thanks. I already loaded the .cal files before opening anything with Ver 5.

In any case I still have to make another measurement after I apply the new filters from ver 5 to get the Freq resp and waterfall charts . 

I will use a separate Filter bank in BFD so I can do a listening test to compare the REW filter schemes between Ver 4 vs Ver 5 .

BTW is it really necessary to to go beyond 80HZ ( xover point) for the filter optimization ? The slope rolls of fairly rapidly after the Xover point . Less feel less filters are better , no? 

Tks


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## JohnM (Apr 11, 2006)

Filtering up to the crossover is fine unless there is a large peak in the sub response just past it. In that region the problem is more related to what the combination of mains plus sub delivers.


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