# Impulse response???



## mjg100 (Mar 12, 2008)

I took an impulse response of subs only. Four DIY sealed subs. I do not have any spikes before the impulse. My noise floor is kind of high right now and I need to work on that. Here is the response and the frequency measurement. Purple frequency response is with out EQ. Green frequency response is with EQ. Please comment on what I have? What I should do differently? Thank you.


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

My understanding is that impulse is not a good method for measuring low frequency response (maybe John can comment). If that’s the case, I would not do any equalizing based on an impulse reading.

If your sub response graph is based on a traditional measurement method (REW’s sine wave sweep or pink noise), then it looks good.

Regards,
Wayne


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## JohnM (Apr 11, 2006)

Wayne, the impulse response is derived from the measurement, it is just a different way of viewing the response (the impulse response and the frequency/phase response both show the system behaviour, impulse in time domain, frequency/phase response in frequency domain). 

mjg, EQ looks to have worked well, but you might want to see if the notch at around 120Hz can be improved. If you happen to have the sub crossing over at around 120Hz it may just be phase setting, otherwise made need to try adjusting placement of the sub/speakers/listening position to see what effect that has.


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## glaufman (Nov 25, 2007)

Also run the sweep higher up to see for sure how it integrates and relates to the level of the mains.
John, does that IR show some reflections that should be tamed?


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## JohnM (Apr 11, 2006)

glaufman said:


> John, does that IR show some reflections that should be tamed?


Difficult to say, best is to make a full range measurement and look at the impulse response envelope (ETC) to identify reflections.


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## mjg100 (Mar 12, 2008)

Here is a full range frequency response (mains and subs), impulse response mains & subs) and waterfall of mains and subs. The mains are crossed to the subs at 100hz. I have four subs. Two are about 9' (symmetrical in front right and left corners) from listening position and two are about 7' (symmetrical in back right and left corners) from listening position. Would I be ahead to get something like the FBQ2496 so that I can set delays on each pair of subs?

Added
No smoothing.


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## pierreye (May 6, 2010)

I don't think FBQ2496 can set delay for each channel. Correct me if I'm wrong. I think to be able to set delay, the model should be DCX2496.


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## mjg100 (Mar 12, 2008)

pierreye said:


> I don't think FBQ2496 can set delay for each channel. Correct me if I'm wrong. I think to be able to set delay, the model should be DCX2496.


Oh well. I am not interested in spending over $200 just to be able to set delay. Especially since my subs do not vary in distance by a huge amount. I did run a frequency response with just the two front subs and then again with two front and one rear. I compared those two with two front subs and the rear sub with switched polarity. Switched polarity on the rear sub caused a dip. Response was the smoothest with all four subs using the same polarity.


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## glaufman (Nov 25, 2007)

For your waterfall to bemeaningful it needs to show more decay. Reset the vertical axis so it's max is 100dB. That IR is showing some bad distortion.
I can't tell if the hump around 150 Hz is a ring or phase between main and sub, or if the subs are running hot WRT the mains.


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## mjg100 (Mar 12, 2008)

glaufman said:


> For your waterfall to bemeaningful it needs to show more decay. Reset the vertical axis so it's max is 100dB. That IR is showing some bad distortion.
> I can't tell if the hump around 150 Hz is a ring or phase between main and sub, or if the subs are running hot WRT the mains.


The subs are running hot. Here is the waterfall with 100db for the upper limit. I have taken impulse measurements from this same location and they did not look like this. I do not have a mic stand. Right now I am resting the mic on the top of the couch so that the receiving end is in the air at about ear height and pointed forward.


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

mjg100 said:


> Oh well. I am not interested in spending over $200 just to be able to set delay. Especially since my subs do not vary in distance by a huge amount.


If you don’t mind having a used equalizer, the Yamaha YDP2006 digital parametric EQ has delay adjustments. You can get them pretty cheap on eBay these days.

Regards,
Wayne


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