Originally Posted by cannga
1. Roger, trying to follow your discussion with Dan. Essentially Dan is not using automated room correction for all the subwoofers and you are asking "why not"?
No. The question is about treating the bass non-uniformly. Some of it (LFE) goes to certain subs. Other goes to other subs. The subs themselves are not of the same type, number or capability.
In my opinion, all bass is equally important. All of it should be heard, and if possible heard consistently in every seat.
In small rooms, like mine, the modal problems extend higher than larger rooms, so that drives me to dismiss notions of "stereo bass" and go for multi-sub cancellation, at least up to 80 Hz. OTOH, the lowest mode is 35 Hz, so below that it is not necessary to use a multi-sub solution for mode control. I imagine most home theaters have similar characteristics.
Since flexible crossovers are available, I was wondering why a system like Dan describes would not first perform global bass management (collect all bass <80 Hz from all channels incl LFE); split that signal with a crossover around 30 Hz; drive the several 12" midbass subs (positioned for effective mode cancellation) with the 30-80 Hz signal and tune them as a group with one channel of EQ; and drive the 22" ULF subs with the <30 Hz signal and another channel of EQ.
Other questions please:
2. Do all these devices with automated room correction (Trinnov, Dirac, JBL) by definition have a built in manual PEQ?
Yes for TEQ and JBL (Harman Synthesis) but there is no PEQ as part Dirac, per se. Datasat included a few bands for subwoofer tuning.
Is that what everyone means when they talk about "modifying the target curves"?
No. The target curve editor allows the user to set a handle on the target line and pull it up/down. Doing so alters the EQ indirectly because the correction algorithm tracks that curve. The big problem that poses for me is that you cannot hear what you are doing in real time. So it is an iterative process.
Users would have a choice of whether to use automated EQ, or manual EQ?
Yes, I believe all the systems offer some form of manual EQ, but the Datasat uses 1/3 octave graphic as a result of its theatrical heritage. While manual adjustment of the target alters the EQ, it is not the same as performing manual EQ.
3. Comments on my guess please: most likely Dirac in Theta would be in digital domain, immediately following the decoding chip, and before the DA conversion step?
EQ has to follow decoding, but it can also follow other things like surround processing and bass management.
It would stay in signal path whether or not you are using room correction?
The beauty of digital is that when it is turned off, it is fully out of the signal path.