TOPIC:

At least one user claims that un-checking the sub check box produces a flatter response. I keep thinking that the check box does something on the sub channel that is desirable, but don't know for sure. Can someone explain exactly what the check box does?

Hi Jerry, devteam said (probably in the long DDRC thread) that Dirac Live uses a different method to calculate the impulse response if the box is checked. So I'd assume that the delay that is put on that channel will be different. Could you be more specific about "un-checking the sub check box produces a flatter response"?

Doing a 15-300Hz REW sweep is flatter if the calibration was done with the box unchecked.

C'mon Jerry, I'm trying to help. This is just the sub? .... Do you mean with bass management on?

Sorry, I wasn't trying to be difficult.

- Two calibrations, one with sub box checked, one with sub bios unchecked.
- REW frequency sweeps 15-300Hz, including subs and one main speaker (e.g. Left channel)
- Bass management turned on in the AVR
- Crossovers at 80Hz
- REW sweeps through the AVR (not directly on the 88A)

Does this provide the information you were looking for?

Hello Jerry,

This is indeed odd. I don't believe that we've seen this before. We could investigate later to see what's the issue. We only have limited information (or can only publicly publish) as to what Dirac is doing with their filter optimization besides what we explained earlier so once we get such reports, we'd typically need to get that info back to Dirac HQ for investigation.

If we have a specific project sent to us which does showing these symptoms, it's always easier since it will tell us more on how for this specific set of measurements, Dirac Live decided to invert the phase..

DevTeam

I suspect that Dirac Live will invert the channel if it detects the impulse peak to be negative-going.

Another factor here may be the bass management. If Dirac Live uses a different method to detect the impulse response peak of the sub with the box checked, then it might be assigning a different delay. That will certainly change the combined response with bass management applied. That's what you would expect, actually. The only real question is whether it is the correct delay.

Neither of the above theories confirmed by measurement. It think it would be helpful if DLCT offered the end user more visibility into what the algorithm does i.e. delays and levels.

I don't think this warrants any further work. I was not me who experienced a flatter response with the sub box unchecked, it was someone else. My purpose of opening this thread was to confirm that if there is a sub on a channel, there is a valid reason that the box should be checked.

minidsp admin should check out the thread in avsforum, post 1654 & 1655:
www.avsforum.com/forum/90-receivers-amps...56.html#post31403129