# Using EQ to flatten LF of main speakers?



## NimaBeamer (Jan 15, 2009)

Hello,

I am using two Klipsch Epic CF3 in a treated room (absorbers in the corners, ceiling and the side walls) and two Klipsch THX KW120 subwoofers. The integration of sub and mains (80Hz double bass for stereo and 60Hz sub alone for HT) is good and I love it with both 2Ch and HT. I am using an AntiMode 8033 to process the subs. 

But since we all strive for perfection I noticed while measuring my main speakers that my LF was a little bit low. Would a parametric EQ help? I am bi-amping the speakers so I could insert an AntiMode or a PEQ before the LF amp.

Would it do anything good? Waste of time? Would the integration with the subs be better, smoother?

Thanks,
N.


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## dougc (Dec 19, 2009)

Are your mains set to large and full range? How are they located in relation to walls, corners, each other?


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## NimaBeamer (Jan 15, 2009)

Hi Doug,

for 2 Channel use (which this graph represents) I use a Parasound 2100 preamp which has a full range pre-out where the Klipsch speakers are connected and a sub out with an analog bass management (set to 80 Hz).

Here is a picture of the setup. Both corners are filled to the roof with fluffy fibre glass wool under the screen there are 30 cm fluffy stuff absorbers (> 5 kPa*s/m²). And the sides have absorbers which are a combination of the fluffy stuff and a first layer of more rigid acoustic fibre glass wool (> 11 kPa*s/m²) , ceiling is treated as well. RT60 is around 0,2-0,3s. 
I put the main speakers on the stands (filled with sand) to raise them to ear level.


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## dougc (Dec 19, 2009)

It doesn't look like you have much wiggle room for positioning of your mains for a better response. REW has a nice feature that builds a custom filter for you from your measurements, and then can be uploaded to the miniDSP. I have not done this yet for my subs, but plan to. I imagine it could have similar use for your mains. Hopefully someone with first-hand experience can educate us.


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## NimaBeamer (Jan 15, 2009)

I was thinking about a Anti Mode Dual Core or a OpenDRC MiniDSP. FIR vs PEQ. Which is better? :innocent:


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

NimaBeamer said:


> But since we all strive for perfection I noticed while measuring my main speakers that my LF was a little bit low. Would a parametric EQ help?


 “Low?” Not sure what you mean by that. And which graph are you referring to?

Regards, 
Wayne


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## NimaBeamer (Jan 15, 2009)

Hey Wayne,

sorry low was probably the wrong choice of word. I mean the blue graph and I am bothered by the response my main speakers are showing up to 200Hz. Am I am too critical? Would EQ do any good or would it be just money thrown out of the window? 

Thanks,
N.


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

I don’t see anything in the blue graph in the 200 Hz range that I’d be concerned about. I’d be more concerned about the wholesale 8-10 dB drop your sub has above 50 Hz. Parametric EQ could do some improvement there.

Regards, 
Wayne


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## NimaBeamer (Jan 15, 2009)

Thank you Wayne. This results from Lift35 having been activated on my AntiMode 8033. 

I deactivated all lift functions and recalibrated. I think it looks good now.


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

Well, the bass definitely looks better, but now everything above 500 Hz looks worse.

I just noticed, you should re-scale your graphs. The 200 dB vertical scaling you’re using is very coarse and will make any graph look great.

Getting Graphs Ready to Post

Regards, 
Wayne


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## NimaBeamer (Jan 15, 2009)

OK here are new graphs with new calibration using the AntiMode 8033 with Lift25 in place. 

I have resized the graphs according to the FAQ.

1. Pic Subs after calibration with AntiMode

2. Main speakers

3. Both together

4. Waterfall of them together

What I do not understand is the dip between 40-80Hz and the spike at 1200Hz. I have so much absorbers in place what else could I do or what did I do wrong? :dontknow:

The HF was attenuated (I bi-amp the main speakes) with the amp level controls. 

Looking forward to hearing some input.

Thanks,
N.


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## jtalden (Mar 12, 2009)

If "double bass" was on for these measurements that is probably the explanation. The double bass feature can work just fine, but it requires the SW and main woofers to be reasonably phase aligned over the entire overlap frequencies. It is sometimes recommended to not use this feature for that reason. 

Phase alignment is often a problem at the XO frequencies even for a normal XO. It is generally easier to get reasonable alignment for a normal narrow overlap region than it is for a wide double bass XO region.

The phase alignment is just the SW and main speaker drivers working together rather than fighting each other. This is normally adjusted by changing the SW distance setting in the AVR/PrePro. 

Things you could easily try:
> Turn off double bass and see if at least some of that 40-80 Hz region improves. [This will just help to confirm that phase alignment is an issue.]
> Use the RTA feature in REW to provide a continuously updated SPL response while you adjust the SW distance setting in the AVR. Find the distance setting that provides the greatest output in that overlap region.

[If all your main speaker and SWs are all set initially to the actual tape measured distances then normally you should expect to find a better SW distance setting by increasing the SW distance setting. Hopefully you will find a setting that is significantly better. If the distances were set with Audyssey or other automated system these are usually pretty good, but they are not infallible.]

If you don't want to do the RTA testing and would like to post a measurement file, I would be able to tell you if a distance adjustment would be beneficial and what that new setting should be. The file (*.mdat) of sweep measurements must be made with REWs loopback feature activated and it should use 15-20k Hz sweeps for the 5 test conditions below:

1. SWs (both SWs together)
2. FL (Front Left Main alone)
3. FR (Front Right Main alone)
4. SWs + FL (together)
5. SWs + FR (together)


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

NimaBeamer said:


> What I do not understand is the dip between 40-80Hz and the spike at 1200Hz. I have so much absorbers in place what else could I do or what did I do wrong? :dontknow:


 Absorbers merely make the room more “dead” by reducing reflections. They do nothing for eliminating anomalies in frequency response that might be present. That requires equalization.

Regards, 
Wayne


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