Can REW Provide EQ Curves Based on Two Speakers' Interaction?

[tamtam]

My usual workflow is to measure each monitor separately and apply the EQ curves suggested by the software. Today, I noticed that when the signals are combined, new problems or solutions appear. For example, one of the speakers had a dip around 60Hz, but the second speaker had a bump in this area, which resolved the issue. Another example is a bump around the same frequency in both speakers: while each speaker on its own is 3dB below the target, when combined, they exceed the target.

This basically means I need to perform manual corrections for the combined signal. I'm curious if REW has an automatic solution for this.

Thanks!

 

[Purité Audio]

Yes you can measure left or right and left and right together.
Keith

 

[tamtam]

Yes you can measure left or right and left and right together.
Keith

Of course I can, that's what I have described above
My question was about EQ curves per speaker, based on 3 measurements, one for every speaker and one combined.

 

[staticV3]

I'm curious if REW has an automatic solution for this.

There's no automatic solution for this built into REW.

loudspeakers.audio can do it, but it only outputs .WAV convolution files.

 

[tamtam]

There's no automatic solution for this built into REW.

loudspeakers.audio can do it, but it only outputs .WAV convolution files.

Thanks.

 

[Keith_W]

1. Measure both speakers at the same time (as Keith suggested)
2. Measure left and right, then Trace Arithmetic A + B. Not as good as measuring both, but adding the two curves gives a reasonable prediction of the outcome.

REW's help page mentions minimum phase cascades very briefly, but here is a summary:

A crossover filter and a single speaker driver, are each minimum phase. If these two are connected in series, the outcome is a convolution (multiplication) operation. In REW, A * B. Because a zero value multiplied by a non-zero value remains zero, the outcome will remain minimum phase.

Two speaker drivers, or two loudspeakers, or a speaker and a subwoofer (etc) are each minimum phase. If they play simultaneously, the outcome is an addition (REW A + B) operation. Because a zero value added to a non-zero value will be non-zero, the outcome is not guaranteed to be minimum phase.

 

[basscleaner]

To explain this phenomena you need to get knowledge about Low Frequencies field behavior in room. First of all, there you couldn't use two low frequencies sources measurement result like a sum of each other due to LF modes in any room. The second, due to wall reflections. Third, because of dependence between LF sources coordinates for LF centers of these ones and measurement results. An every thesis demands explanations. But there is fourth point of view, maybe even more important, but more understandable for you. Look, any room is the resonant camera for your sound sources. Therefore, dimensions, shapes and furniture have the direct influence at your listening point in sound pressure and timbre. Maybe you should be ready to change your room dimensions by a little bit, to get the best sound quality in the listening point?

 

[Digital_Thor]

Divide your frequency response roughly in two groups. Above 500Hz is direct sound, and below is - as you go towards 20Hz - more and more dominated by the rooms reflections.
At 60 Hz you can just combine your speakers and measure them together, as there's no stereo information down there.
Just send them the same signal, and also independently, so you know where to add EQ.
The speaker with a dip at 60Hz, is a cancellation of reflection's. You can't EQ that. You have to move that speaker, change the room (hard at low frequencies) or fill in the dip with another speaker/subwoofer, which is placed somewhere else, and therefore does not have that dip

 

[diablo]

I find that I need to move the speakers around (with rough room correction) until the combined left and right give me something that looks okay in REW. Then do the proper setup.

If your speakers are in fixed positions then, yes, EQ the result - but it isn't the best solution.

 

[Digital_Thor]

I find that I need to move the speakers around (with rough room correction) until the combined left and right give me something that looks okay in REW. Then do the proper setup.

If your speakers are in fixed positions then, yes, EQ the result - but it isn't the best solution.

Good addition. Yes - always start with the best possible position for the speakers and listening position - then EQ.
This is also why the use of speakers with a more constant directivity and added subwoofers, are increasingly popular, because you have added freedom in the total setup - simply a bit more independent of the room - though never fully.... that simply is not going to happen. Room rules