- May 22, 2017
- Arizona, USA
My AV System
- Preamp, Processor or Receiver
- Marantz AV7705 Pre/Pro
- Main Amp
- Rotel RMB-1066 6 chnl P-amp x 2
- Additional Amp
- Behringer DCX2496 x 2
- Universal / Blu-ray / CD Player
- OPPO BDP-103 Universal Player
- Front Speakers
- DIY SEAS H1456/H1212 Spkr x 5
- DIY JBL 2235H 15" SW x 2
- Video Display Device
- JVC DLA-X790R
- Da-Lite Da-Snap 39105V - 92"
The sound quality is primarily the result of a smooth SPL response. Phase irregularity is much less important. Phase is a very helpful indicator of why the SPL is behaving as it does. Phase analysis assists in helping to choose the XO frequency and timing that supports a smooth SPL using a minimal amount of EQ. We expect that EQ will be needed in most all cases to optimize the SPL smoothness up to the transition frequency; about 200Hz for small rooms.One point - would the timing not sound better if they were in phase at crossover and if the crossover is set low do we need to worry about the EQ being flat up to 180 or just up to a point just above the Xover?
Use the option that best meets the objective stated above: Provides a smooth SPL with minimal EQ up to 200 Hz. The 40 Hz XO with the the distributed SW locations does not look as promising as the earlier options if I recall correctly. Dirac may still successfully EQ it however.I have limited choices really in my room:-
1. Stack the two subs in the position of sub 1 which gives me a 6db increase in headroom. Dirac loves the position of Sub1 and seems to give a fairly flat response on its own down very low. I can bump up the curve at low frequencies and it allows the adjustments to the curve. Loads of output! You only have to time one sub position.
2. Use Sub1 and Sub2 in their different locations see diagram below. Sub 1 is located exact middle of my right hand wall pointing in to the room. Sub2 is located to the left rear of my sofa. See attached Room Sim. This spreads the bass more in the room but it seems at the expense of some cancellation and SPL. Dirac struggles with the Sub2 trace with big dips at about 25hz and it can't be eliminated by tweaking that curve.
1. Based on the technical results only which option is best?
I would not think that would be an improvement on the options already found. The SWs would be out of phase over most of their range.2. The simulation indicates gains could be made by inverting Sub2 - is that worth exploring? I presume a new Dirac run would be needed after Sub2 is set as inverted. I measured the output at 40hz sine but it did not seem to increase when it was inverted.
40 Hz is okay if Dirac can successfully EQ it. I personally would not use the 40 Hz XO. I think a 60, 80 or 100 Hz XO would be more appropriate. Are the Dirac predictions of Post-14 realized in actual REW measurements or was there a problem?3. Would you still personally go for a 80hz Xover with the two subs and the JBLs? From what you say 40hz seems to be Ok?
There is likely nothing significant to be gained with a 3rd SW given where it can be located.4. Would stacking two subs in Sub 1 position + adding a third in Sub2 position be worthwhile?
I may be missing the concerns you are having. My take on this setup is that Dirac BM successfully mitigated a major L vs R phase issue that cannot be corrected using standard PEQ filters. Thus Dirac is the logical choice to use. I would tend to follow its recommended settings or maybe also try 60 or 80 Hz XO as well as the 100 Hz XO to see which one results in the best REW measurements. If the measurements look good and there is still a sound quality issue, I suggest that adjustments to the house curve in Dirac would be the first thing to try. The Post-14 Dirac settings do not call for any of the normal house curve rolloff for the higher frequencies, but it looks like you can easily adjust it as needed to suit your preference.Could you kindly please explain the procedure for EQing the two subs and calculating the filters in REW if I want to try this manually. There is a Storm format output option so the .txt EQ filter files can be exported from REW and imported into the Storm by individual sub/speaker but I am not sure whether I would need to create one filter per sub or combine them in REW somehow and put the same filter on both.............. and if so how?!