Near field versus far field guidance

[johnk]

Hi,
Firstly, thank you to everyone here for sharing your knowledge in this fascinating forum.
I have made excellent progress using REW and a UMIK-1 in improving my small office system, but I am struggling to replicate the same success on my main system. My assumption is that it is easier to make significant improvements in a near field set up in comparison to the complexities of dealing with the more complicated reflections and room modes with the larger room due to the larger distances. Is my intuition correct?
Second question. I have currently been applying the same eq to left and right channels (mainly due to my time constraints). My rooms are both reasonably symmetrical. Is there likely to be a significant benefit in eq'ing left and right separately? Is it something that most people here do?
Thanks,
John

 

[Purité Audio]

Yes, left then right then together, I would only correct the low bass, up to where the plot becomes less wiggly, perhaps 300Hz you will see the transition zone on the plot.
Then if the room is ‘traditionally’ furnished and depending upon loudspeaker choice you should be fine.
Keith

 

[Frgirard]

Hello,

Hi,
My assumption is that it is easier to make significant improvements in a near field set up in comparison to the complexities of dealing with the more complicated reflections and room modes with the larger room due to the larger distances. Is my intuition correct?
John

yes

Second question. I have currently been applying the same eq to left and right channels (mainly due to my time constraints). My rooms are both reasonably symmetrical. Is there likely to be a significant benefit in eq'ing left and right separately? Is it something that most people here do?
Thanks,
John

This way of doing - under 150 Hz - preserved the stereo picture. I tested with separate EQ L / R and EQ identical L / R and never noticed the slightest change on the stereo image. I stayed in separate EQ L / R, there is no good compromise to seek.

 

[dominikz]

I have made excellent progress using REW and a UMIK-1 in improving my small office system, but I am struggling to replicate the same success on my main system. My assumption is that it is easier to make significant improvements in a near field set up in comparison to the complexities of dealing with the more complicated reflections and room modes with the larger room due to the larger distances. Is my intuition correct?

I struggled with similar questions a few months back but found a fairly simple formula that IMHO works pretty well in mid/farfield:

1. Use MMM with periodic pink noise to measure L and R individually, and then L+R together
2. In REW set the EQ target curve to your preferred target (I use either the -0,8dB/octave slope or B&W 1974 target in my main system) and generate cut-only filters for individual L and R channels (set maximum individual and combined boost to 0). Typically I limit the correction to the area below ~300Hz or so (so below the room transition / Schroeder frequency) and I allow high-Q filters here
3. After you apply the filters use MMM again to remeasure L and R individually, and then L+R together to validate your results. With some luck there will be no new notches in the combined L+R response after EQ
4. Listen
5. If the combined L+R response after EQ sounds ands looks more ragged, you can instead use the original L+R measurement to generate the EQ that applies to both channels and repeat steps 3. and 4.

Second question. I have currently been applying the same eq to left and right channels (mainly due to my time constraints). My rooms are both reasonably symmetrical. Is there likely to be a significant benefit in eq'ing left and right separately? Is it something that most people here do?

In my experience both combined and separate L/R EQ can work pretty well, thought strictly speaking each is a bit of a compromise IMHO:

• EQ-ing L and R individually with IIR filters (minimum phase) can cause new peaks and dips in the L+R response due to the introduced phase shift. Though I haven't experienced any issues, I assume it might be audible with recordings that have bass frequencies mixed to mono.
• EQ-ing L+R together will give a smoother mono bass response, but now individual channels might still have some peaks and dips. This might be audible with recordings that have stereo bass content.

If you're interested I've documented my experiences with REW generated EQ and MMM here (the same thread also cover various other DRC tools I tried).

Another note - if your speakers are not neutral in tonality but have good directivity, you can also EQ above the transition frequency based on anechoic listening window (LW) response from measurements such as provided by @amirm or @hardisj. Do note however that there is typically some variability within speaker production runs so depending on production tolerance precise high-Q EQ corrections might or might not apply to your specific unit (even if anechoic measurements are available) so low-Q tonality corrections will likely be more universal. You could also try to measure LW response of your specific loudspeaker units using this guide by @napilopez to be able to generate custom speaker-correction EQ filters in HF - but again note that quasi-anechoic method loses precision in the mid frequencies so you would again be partially limited there.

There are also some arguments that doing full-range EQ corrections (i.e. above transition frequency) directly based on in-room steady state response (such as measured with MMM or single-point measurements with sweeps and gated by FDW) but although it can sound pretty good, so far I can't really see how that approach can avoid introducing new resonances to the loudspeaker direct-sound - it is something I plan to investigate more going forward.

 

[johnk]

Thank you all for your help. I just tried removing all the eq above 300Hz to my small office system and still sounds very good. I am surprised by how big the benefit is without even touching the higher frequencies. That certainly helps to speed up my testing which my family will appreciate.

Another note - if your speakers are not neutral in tonality but have good directivity, you can also EQ above the transition frequency based on anechoic listening window (LW) response from measurements such as provided by @amirm or @hardisj.

The speakers are Wharfedale Diamond 230 floorstanders which have the same tweeter as the 220 which has been reviewed here, but with a pair of larger (6.5") woofers so I am not sure how much use the data in the review will be. At least the 220's had good directivity so I am hoping the 230's are similar.
I think I will focus on improving <300Hz carefully and add a quick shelf filter to bring down the energetic high frequencies above 4k (as per the 220 https://www.audiosciencereview.com/...dale-diamond-220-budget-speaker-review.16752/)
Thanks again, John

 

[dominikz]

Thank you all for your help. I just tried removing all the eq above 300Hz to my small office system and still sounds very good. I am surprised by how big the benefit is without even touching the higher frequencies. That certainly helps to speed up my testing which my family will appreciate.

The speakers are Wharfedale Diamond 230 floorstanders which have the same tweeter as the 220 which has been reviewed here, but with a pair of larger (6.5") woofers so I am not sure how much use the data in the review will be. At least the 220's had good directivity so I am hoping the 230's are similar.
I think I will focus on improving <300Hz carefully and add a quick shelf filter to bring down the energetic high frequencies above 4k (as per the 220 https://www.audiosciencereview.com/...dale-diamond-220-budget-speaker-review.16752/)
Thanks again, John

No worries, glad it was helpful!
You can use MMM to measure your speaker and compare your measured response to the PIR (predicted in room response) from the 220 review - if they reasonably match above ~1kHz it would IMHO be a good indication that similar HF filters can be used.
Good luck!

 

[dominikz]

No worries, glad it was helpful!
You can use MMM to measure your speaker and compare your measured response to the PIR (predicted in room response) from the 220 review - if they reasonably match above ~1kHz it would IMHO be a good indication that similar HF filters can be used.
Good luck!

Just in case you're interested, here's how my Revel M16s measured in-room at listening position with MMM match the PIR from anechoic measurements done by @amirm:

As you can see, there's a pretty close match above ~400Hz (much below the room is in almost full control anyway). You can see my measurements exhibit a bit deeper dip between 1,5-3,5 kHz - I believe this is because my listening position is below the tweeter axis and my room is very reflective (so ceiling and floor reflections affect the response more).
Still, I'm always pretty amazed how much the PIR matches a real room MMM measurement

 

[johnk]

I just wanted to add a follow up to this. I have now spent more time measuring my main room and re-measuring with different speaker positions etc. In summary, I have been able to make significant improvements in my larger room, but it did take more "fiddling" than with the near field set up. I guess intuitively that there are a lot more reflections and such to deal with in a larger space, so that makes sense to me. I also needed to spend more time just learning REW as I was caught out a few times.

Some of my REW mistakes were:
- Setting the target level differently for L and R speakers when generating eq.
- Selecting "Add room curve" as well as having loaded a house curve in the preferences
- Allowing it to create too many filters. This made it difficult to read and see what was going on. I have been tending to limit it to 6 parametric filters per channel.
- I also had issues with my microphone calibration being disabled as the mic popped up as a different device depending on which USB port/hub I was connecting with.

All up I am very happy with my progress