Roomfit cut only mode B&K vs Flat

[slartibartfast]

I've been listening to my Amp with Roomfit 20Hz-600Hz, B&K target, individual channel, cut only mode and it sounds fine. I thought I would try the flat target instead of B&K and the results look almost exactly the same to me. Anyone else tried the comparison. I have always seen and heard a difference when comparing the targets before.

 

[slartibartfast]

I've been listening to my Amp with Roomfit 20Hz-600Hz, B&K target, individual channel, cut only mode and it sounds fine. I thought I would try the flat target instead of B&K and the results look almost exactly the same to me. Anyone else tried the comparison. I have always seen and heard a difference when comparing the targets before.

Just me then? Has nobody else found that changing the target from B&K to flat makes virtually no difference to the results in cut only mode with individual channels?

 

[Frans]

Just me then? Has nobody else found that changing the target from B&K to flat makes virtually no difference to the results in cut only mode with individual channels?

No, I did the same and it makes no any difference

 

[slartibartfast]

No, I did the same and it makes no any difference

I sent a ticket. Let's see how WiiM respond.

 

[slartibartfast]

I got this reply which doesn't explain it at all.

"We recommend adjusting the subwoofer sublevel after completing room correction, perhaps by reducing it by about 1-2dB. This variation is mainly due to the separate calibration of the left/right channels and the subwoofer. During actual verification, using both stereo and subwoofer calibrations may reveal slight discrepancies, which can result in the subwoofer level being about 3 dB higher than the main speakers. This is normal."

 

[harkpabst]

Have you tried a full range correction (just for the fun of it) with both target curves? I wonder if there might simply be too little of a difference in the results between 20 Hz and 600 Hz?

 

[dominikz]

Have you tried a full range correction (just for the fun of it) with both target curves? I wonder if there might simply be too little of a difference in the results between 20 Hz and 600 Hz?

I suspect the same!

 

[slartibartfast]

Have you tried a full range correction (just for the fun of it) with both target curves? I wonder if there might simply be too little of a difference in the results between 20 Hz and 600 Hz?

1. Flat 20-600Hz


2. B&K 20-600Hz


3. Flat 20-20000Hz


4. B&K 20-20000Hz

 

[harkpabst]

These look like expected results to me.

 

[slartibartfast]

These look like expected results to me.

To me it looks like the target for Flat 20-600Hz is higher than the target for Flat 20-20000Hz even though no correction takes place above 2000Hz.

 

[slartibartfast]

These look like expected results to me.

I tried again with a frequency range of 20-4000Hz. You can see that the B&K target is about 3dB higher than the flat target below 100Hz so it seems to be OK. Choosing a wider range probably makes it easier for the algorithm to choose a target level that works over the full range. The extra 3dB achieved by the individual channel room correction at low frequencies actually makes the flat target usable for me.

 

[Frans]

I did the same and indeed a wider range makes the difference.. thanks

 

[telecastermds`]

I tried again with a frequency range of 20-4000Hz. You can see that the B&K target is about 3dB higher than the flat target below 100Hz so it seems to be OK. Choosing a wider range probably makes it easier for the algorithm to choose a target level that works over the full range. The extra 3dB achieved by the individual channel room correction at low frequencies actually makes the flat target usable for me.

View attachment 25451

View attachment 25452

I wonder how it would sound if you added a boost for that big hole between 150 and 500hz.

 

[slartibartfast]

I wonder how it would sound if you added a boost for that big hole between 150 and 500hz.

I left the RoomFit profile as it was and used REW to generate correction filters from 110Hz to 450Hz. I added these filters manually to PEQ so I effectively had 20 filters for room correction and compared the results. The difference is noticeable, the downside being I had to drop the Volume Limit to 79%. Yet the accepted wisdom is to not boost dips.

 

[dominikz]

I left the RoomFit profile as it was and used REW to generate correction filters from 110Hz to 450Hz. I added these filters manually to PEQ so I effectively had 20 filters for room correction and compared the results. The difference is noticeable, the downside being I had to drop the Volume Limit to 79%. Yet the accepted wisdom is to not boost dips.

View attachment 25677

In general it is indeed technically possible to fix some dips with positive gain EQ, but there's several reasons why it is usually advised not to do it:

• Dips are in general less audible than peaks, and narrow dips especially so.
• There's a danger of digital clipping if pre-gain (or volume limit) is not reduced by the amount equaling total EQ boost.
• Reducing pre-gain reduces overall maximum level (and therefore reduces system headroom).
• You can only optimize EQ for a single listening position. Adding a boost by EQ might fix a dip there, but it will result in a peak/resonance elsewhere in the room. This can especially be a problem if you have multiple secondary listening positions.
• True acoustic cancellations can never be fully fixed by EQ boosts. I suspect the very narrow dip around 180Hz is still quite visible if you display your response in e.g. 1/24 smoothing. Maybe the same with the one at around 220Hz.
• Peaks and dips in a response can shift slightly as a result of external factors (see here for one example). Boosting a very narrow dip could give you a very narrow resonance in case the dip shifts in frequency due to a change in the room. As I mentioned above, an equivalent peak is more audible than a dip.

So it is in general simply better practice to try and avoid response dips altogether with careful placement of speakers and subs, and only use EQ after that to knock down the peaks/resonances.

If placement cannot be further optimized and we still have significant bass suck-outs, then adding some EQ boosts can indeed be beneficial; but I'd advise caution when applying it. Personally I'd only use low-Q boost filters (not higher than Q=3), and try to limit the total amount of boost (definitely less than 6dB total).

 

[slartibartfast]

In general it is indeed technically possible to fix some dips with positive gain EQ, but there's several reasons why it is usually advised not to do it:

• Dips are in general less audible than peaks, and narrow dips especially so.
• There's a danger of digital clipping if pre-gain (or volume limit) is not reduced by the amount equaling total EQ boost.
• Reducing pre-gain reduces overall maximum level (and therefore reduces system headroom).
• You can only optimize EQ for a single listening position. Adding a boost by EQ might fix a dip there, but it will result in a peak/resonance elsewhere in the room. This can especially be a problem if you have multiple secondary listening positions.
• True acoustic cancellations can never be fully fixed by EQ boosts. I suspect the very narrow dip around 180Hz is still quite visible if you display your response in e.g. 1/24 smoothing. Maybe the same with the one at around 220Hz.
• Peaks and dips in a response can shift slightly as a result of external factors (see here for one example). Boosting a very narrow dip could give you a very narrow resonance in case the dip shifts in frequency due to a change in the room. As I mentioned above, an equivalent peak is more audible than a dip.

So it is in general simply better practice to try and avoid response dips altogether with careful placement of speakers and subs, and only use EQ after that to knock down the peaks/resonances.

If placement cannot be further optimized and we still have significant bass suck-outs, then adding some EQ boosts can indeed be beneficial; but I'd advise caution when applying it. Personally I'd only use low-Q boost filters (not higher than Q=3), and try to limit the total amount of boost (definitely less than 6dB total).

This is how it looks with 1/24 smoothing. I don't like doing it and was hoping it wouldn't sound obviously better but it surprised me. I still haven't pinned down what causes the dips and can't easily move the speakers far from the current position.

 

[dominikz]

Is this a single speaker response, or both speakers playing at the same time?

 

[slartibartfast]

Is this a single speaker response, or both speakers playing at the same time?

Both speakers

 

[dominikz]

In that case the dips could be a result of either SBIR (interference of a loudspeaker direct sound with sound reflected of walls) or interference between the two loudspeakers. I'd suggest to first try to optimize individual channel responses - ideally with placement.

Then you can compare the differences in individual channel and summed channel responses (which will always exist to some extent).

Note that if you optimize for a smooth combined channel response by boosting dips that are exclusive to it, you will introduce new peaks/resonances to individual channel responses. In other words optimizing for the combined channel response in some frequency range will favor center-panned (or mono) content, at the expense of hard-panned (stereo) content. The opposite is true as well.

However, given that we're less sensitive to dips than the peaks, I'd personally rather have some dips in the summed response with no peaks in the individual channel responses.

But in the end, if you prefer the sound with this new EQ that is of course perfectly OK!

 

[harkpabst]

I'd probably just check if the combined response is still reasonably flat when measured in a reasonable area around the MLP. Maybe like +/-40 cm in multiple directions.