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Running Dirac on 2 channel stereo system (without a subwoofer)?

Symphoniac

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I am interested in the NAD C658, despite the unflattering measurements Amir observed, as it seems to have a really nice feature set, including Dirac room EQ. One question I have is, when running Dirac for stereo listening, how does it deal with nulls in the bass region (<100hz)? I know that one must be very careful about boosting bass as it can lead to the power amp clipping and/or distortion in the woofers. I've read that Dirac starts with a -10db adjustment to make extra headroom, and perhaps this will mitigate concerns about clipping as long as you don't jack up the volume too high; but, isn't it still possible for the woofers to distort with upwards of 10db EQ boost (depending on speaker ability of course)? Or is Dirac smart enough to not make such drastic adjustments or possible to set it so that it only cuts and doesn't boost? I suspect this is not a big concern if you have a sub and are able to high pass the main speakers at an appropriate frequency (e.g., 90hz), which would protect your speakers from over-exertion, hence the question about applying Dirac to a 2 channel setup without subs. Curious what this looks like in practice.
 
It will look like just like with a sub. Even with a sub you can't boost bass infinitely. It will be fine.

Edit: I meant "looks the same" literally. Dirac measures mains and sub(s) and after this you can disable the sub but still have corrected bass. It doesn't do anything totally chaotic and destroy the mains with or without sub. :)
 
Have you looked at the measured curve without a Dirac filter?

I doubt there are serious nulls if the speakers have been set up optimally and some attention is given to furnishings. I'm sure that Dirac has a limit on it's boosting for the reasons you suggest. As far as Dirac starting with a 10dB attenuation in order to take care of boosting certain frequencies, I don't think it does. When I run Dirac on my NAD amp, I'm getting only a very slight drop in overall volume with the filter engaged, so it may be that it will only apply this 10 dB cut if the system has large nulls that would cause problems if corrected without the cut. My system seems to sound better without Dirac engaged anyway, so I guess it's well set up already.

It's also odd that (despite Dirac not ADJUSTING frequencies above 500 Hz) there is a slight loss in top end sparkle when Dirac is engaged. I've concluded that this is because the ENTIRE FREQUENCY RANGE signal has to pass through this digital processor (where a single full-range is used) and it does the top end no favours having to endure this unnecessary processor. Have other Dirac users found this with high end speakers?
 
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It will look like just like with a sub. Even with a sub you can't boost bass infinitely. It will be fine.

Edit: I meant "looks the same" literally. Dirac measures mains and sub(s) and after this you can disable the sub but still have corrected bass. It doesn't do anything totally chaotic and destroy the mains with or without sub. :)
Good to know! But assuming Dirac applies a moderate bass boost, isn't it still more likely you'll start to hear woofer distortion at a lower volume level compared to when listening without EQ? For example, let's say you have two settings, with Dirac, which applies +6db boost at 60hz (highly simplified for sake of this thought experiment), and without Dirac, i.e. flat/no EQ. You want to compare the two by starting at the same volume, let's say -40db, and switching back and forth between Dirac on and off. You gradually turn the volume up by 3db increments... in this thought experiment, is it more likely that you'll hear woofer distortion for when Dirac is on at -25db compared to -19db for when Dirac is off? If so, is it fair to say you can't listen as loud with Dirac compared to without Dirac? Has anyone had this experience?
 
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Have you looked at the measured curve without a Dirac filter?

I doubt there are serious nulls if the speakers have been set up optimally and some attention is given to furnishings. I'm sure that Dirac has a limit on it's boosting for the reasons you suggest. As far as Dirac starting with a 10dB attenuation in order to take care of boosting certain frequencies, I don't think it does. When I run Dirac on my NAD amp, I'm getting only a very slight drop in overall volume with the filter engaged, so it may be that it will only apply this 10 dB cut if the system has large nulls that would cause problems if corrected without the cut. My system seems to sound better without Dirac engaged anyway, so I guess it's well set up already.
I do think I have something like a null in my room at 80hz. I have measured 4 different speakers placed approximately in the same position (not at the same time of course) and all graphs have a suck-out around 80hz. How deep the suck-out is varies depending on the bass output of the speaker, so the less bass the speaker has, the bigger the suckout. Unfortuantely, I am not able to move the speakers or add/move furnishings to alleviate this as this is a common/shared living room situation. I'm actually not all that worried about remedying this null with my current tower speakers because they are not as affected by the null (compared to the 3 other speakers I tested with lower bass output). My concern is that when I apply a target filter in Dirac, which will be beneficial for knocking down some of the bass peaks, it will also try to fill that null and cause the woofers to over-exert. Maybe I'm overthinking this and just need to order the NAD and try it.

It's also odd that (despite Dirac not ADJUSTING frequencies above 500 Hz) there is a slight loss in top end sparkle when Dirac is engaged. I've concluded that this is because the ENTIRE FREQUENCY RANGE signal has to pass through this digital processor (where a single full-range is used) and it does the top end no favours having to endure this unnecessary processor. Have other Dirac users found this with high end speakers?
Is this possibly a psychoacoustic thing where you are percieving less top-end sparkle because Dirac is filling in the bottom-end?
 
It's also odd that (despite Dirac not ADJUSTING frequencies above 500 Hz) there is a slight loss in top end sparkle when Dirac is engaged. I've concluded that this is because the ENTIRE FREQUENCY RANGE signal has to pass through this digital processor (where a single full-range is used) and it does the top end no favours having to endure this unnecessary processor. Have other Dirac users found this with high end speakers?
Going through a process is not harmful in itself.
If you adjust treble level does this sparkle return or is it different? There is absolutely no reason bass adjustment would touch the highs in this sense. More likely 1) the overall level is just lower now and 2) everything is more in balance so the top end is not so clearly present subjectively while it is the same as always. Does the sparkle return with more volume?
 
By balance I mean that the HF components belong with certain instrument that has a presence and main tone lower. Perhaps exess bass masked part of this and you heard the high part as disjointed, which may sound nice even though it is not supposed to sound like that.
 
If you are interested, the new node (2024) and node icon have the possibility to have dirac (optional).
 
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