Does DSP latency matter?

[Gordonj]

While a discussion of minimum phase is way beyond the OP topic, the below article does delve into how a subwoofer interacts in the room, and how the use of EQ can be used to modify the in-room FR and in-room phase response. Naturally the in-room phase response of the subwoofer differs from the quasi-anechoic phase response of the subwoofer - and the two GD plots will of course be different too.

Minimum Phase

Excellent article Ed. Have you seen a negative effect on the overall system response if too much EQ is applied to reduce or counter the room modals? Or, is there a point of diminishing returns when utilizing EQ to counter the room FR both in system FR and minimum phase response of the system?

Gordon

 

[Ed Mullen]

Excellent article Ed. Have you seen a negative effect on the overall system response if too much EQ is applied to reduce or counter the room modals? Or, is there a point of diminishing returns when utilizing EQ to counter the room FR both in system FR and minimum phase response of the system?

Gordon

Anywhere the in-room response deviates greatly from minimum phase, the application of EQ is not advised and doing so will likely result in non-optimal sound. Per the article (toward the end):

The response is no longer completely minimum phase anywhere in the span, as we can see from the excess phase, but it deviates dramatically in the 70-120Hz region. At 110Hz, where there is a sharp dip in the response, there is a sharp peak in the excess group delay. Attempting to EQ the response to flat in this region would be foolish. Regions where the response is far from minimum phase would typically not give the results we might expect and they are best left alone from an EQ perspective. Non-minimum phase regions are also likely to show greater variation with position and to be more affected by changes within the room, as a change that affects any of the signals that sum to the response in the minimum phase region can greatly alter the behaviour there. On the plus side, broadband acoustic treatments in the room are effective regardless of the room's minimum or non-minimum phase behaviour.​

 

[Gordonj]

Anywhere the in-room response deviates greatly from minimum phase, the application of EQ is not advised and doing so will likely result in non-optimal sound. Per the article (toward the end):

The response is no longer completely minimum phase anywhere in the span, as we can see from the excess phase, but it deviates dramatically in the 70-120Hz region. At 110Hz, where there is a sharp dip in the response, there is a sharp peak in the excess group delay. Attempting to EQ the response to flat in this region would be foolish. Regions where the response is far from minimum phase would typically not give the results we might expect and they are best left alone from an EQ perspective. Non-minimum phase regions are also likely to show greater variation with position and to be more affected by changes within the room, as a change that affects any of the signals that sum to the response in the minimum phase region can greatly alter the behaviour there. On the plus side, broadband acoustic treatments in the room are effective regardless of the room's minimum or non-minimum phase behaviour.​

Then, are the "automatic room equalization", programs now being utilized for the HiFi market, intelligent enough to disseminate against the above referenced point of diminishing returns? And since most home users do not have the easy ability to identify those problem modals how can they identify when the tuning program is now being counter productive?

And i realize this question is beyond the scope of the OP but a fun bunny trail never-the-less....

Gordon

 

[Ed Mullen]

Then, are the "automatic room equalization", programs now being utilized for the HiFi market, intelligent enough to disseminate against the above referenced point of diminishing returns? And since most home users do not have the easy ability to identify those problem modals how can they identify when the tuning program is now being counter productive?

And i realize this question is beyond the scope of the OP but a fun bunny trail never-the-less....

Gordon

That would depend on the level of sophistication in the particular auto-set-up program (Audyssey, YPAO, MCACC, ARC, etc.). I would pose that question to the individual brand reps.

On the higher level Audyssey products (XT and XT32), I have certainly seen ample evidence of 'intelligent' decision-making regarding whether or not to employ EQ depending on the severity/bandwidth of a given problematic mode.

My personal approach to addressing room modes in the bass regions when setting up any high-end system is three-tiered: 1) strategically located dual subs (or in some cases quad subs), 2) the use of true bass traps and 3) Audyssey XT or XT32. This usually results in very satisfactory objective results, and subjectively excellent bass sound quality. Not any one tool will ever be completely successful, but employing all three tools has a synergistic effect where the whole is greater than the sum of any individual part.