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Post by Boomzilla on Sept 30, 2014 12:10:51 GMT -5
I wish to run a 2.1 system with a subwoofer handling everything under 80 Hz.
When I was using my Oppo BDP-105 as a preamp, setting phase was easy - Set the phase dial on the sub to zero and tell the Oppo how far away from the listening position the sub was located.
Now, however, I plan to use the (full-range only) XLR outputs of the Oppo and let the XSP-1 do bass management. Although the frequency dials on the back of the preamp allow for turnover point selection, they have no adjustment for phase.
Therefore, unless someone has a better idea, here's my plan for phase adjustment:
Pick a crossover point & play a test tone (on repeat) at that frequency.
With an assistant (with a SPL meter) sitting in the listening position, and me at the sub, I'll start at zero and then move the variable phase pot from marker to marker on the dial. The assistant will record the SPL at each dial marker. The point where the SPL is loudest (least phase cancellation) is the correct phase.
Because even small movements of the SPL meter will make large differences in the level, we may have to repeat the sequence four or five times and average the results.
Once the phase is set, it should not change unless the speaker or sub positions change.
If there's an easier way to do this, please educate me...
Thanks - Boomzilla
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Post by audiobill on Sept 30, 2014 12:18:14 GMT -5
Boom, Carver's Sunfire sub manual, available online, has a good setup procedure.
Agree with you-
I find the point at which the spl at my listening position is maximized while adjusting phase, with the thought that less than that is subtracive from mains.
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Post by ansat on Sept 30, 2014 12:24:27 GMT -5
I would think that Max SPL would not be what you would want. I would think that test tone @ 100 and 60 and match the gain on those two frequency (noting the SPL) and then adjust the phase at the X-over point to match the SPL noted previously. Tony
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Post by audiobill on Sept 30, 2014 12:26:39 GMT -5
It's a question of which comes first, I'd get phase right first, then spl.......but I could be wrong.
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Post by ansat on Sept 30, 2014 12:26:51 GMT -5
I thought you had a Mic Boom? Why not run a sweep or use the RTA in REW?
Tony
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Post by Boomzilla on Sept 30, 2014 12:31:57 GMT -5
Hi Tony -
I'm comfortable adjusting the sub level by ear. I've done it many times & the SPL has verified my choices (last time to within 0.5 dB). Whether or not the sub/satellite levels are equal, the phase will still be correct when the SPL is maximized. Any other option means that there is partial "phase cancellation" between the mains and the sub.
That said, note that the sub can NEVER be in perfect phase with the mains unless it (the sub) is centered between the mains and equidistant from the listening position. In other words, were you to draw an arc using the listening position as the hub, both mains and the sub should be in the same arc with the sub centered. In any other position, the sub may be more or less in phase with one of the two main speakers, but will be partially out of phase with the other. Where I place my sub (in a corner) means that any "phasing" is an approximation only.
Cheers - Boom
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Post by Boomzilla on Sept 30, 2014 12:34:32 GMT -5
It's a question of which comes first, I'd get phase right first, then spl.......but I could be wrong. Actually, which comes first is academic. The max SPL at the listening position (at the crossover point) ALWAYS means minimum phase cancellation (i.e. "in phase). The mains to sub balance can be done either before OR after phase set without affecting the phase at all. At least, this is my understanding (and if I'm wrong, it won't be the first time - LOL).
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Post by ansat on Sept 30, 2014 12:42:00 GMT -5
Hi Tony - I'm comfortable adjusting the sub level by ear. I've done it many times & the SPL has verified my choices (last time to within 0.5 dB). Whether or not the sub/satellite levels are equal, the phase will still be correct when the SPL is maximized. Any other option means that there is partial "phase cancellation" between the mains and the sub. That said, note that the sub can NEVER be in perfect phase with the mains unless it (the sub) is centered between the mains and equidistant from the listening position. In other words, were you to draw an arc using the listening position as the hub, both mains and the sub should be in the same arc with the sub centered. In any other position, the sub may be more or less in phase with one of the two main speakers, but will be partially out of phase with the other. Where I place my sub (in a corner) means that any "phasing" is an approximation only. Cheers - Boom I always find it interesting on setup processes by others. I normally do not care about proper phase alignment (I am strictly theater and 7.something setups) and in fact I use phase as one of the tools in how I calibrate and flatten multiple subwoofers at different listening positions. But I am quite reliant on turning audible sounds into something visual and wouldn't attempt to do anything by ear. Please post your results on what ever you decide. Tony
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Post by Boomzilla on Sept 30, 2014 12:50:22 GMT -5
The centered position of the sub between the mains is not a good match for my listening room. Unlike most rooms, my sub measures flatter in the corner (less peaks & dips) than it does centered. That said, my room is a highly unusual one from a bass standpoint, and the "conventional wisdom" doesn't seem to apply.
With most HT rigs, phase is academic because the built in room correction takes care of it. With one microphone measurement from the listening position, a HT source knows the distances to ALL speakers (and to the subs) and automatically calculates the phase.
My Oppo is less sophisticated (no microphone setup), but it will allow me to input the measured distances to each speaker/sub. Once the distances are entered, the phase is automatically adjusted accordingly.
The XSP-1, however, is even less versatile. There is NO adjustment for phase, and it must be done by other means. Fortunately, my subwoofer has a continuously variable phase pot (from zero to 180 degrees), so I can adjust at the sub. Some subs have a 0/180 degree switch with no adjustments in between and other subs lack even that.
One pays their money - one takes their choice...
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Post by audiobill on Sept 30, 2014 14:01:30 GMT -5
My thinking is to get natural, physical correction first, then introduce any electronic correction.
Much less intrusive and more natural, IMO
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Post by Boomzilla on Sept 30, 2014 14:15:17 GMT -5
I've also heard of a method where one uses the LOWEST SPL to find inverse phase & then sets to 180 different. Is there any benefit in one over the other?
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DYohn
Emo VIPs
Posts: 18,351
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Post by DYohn on Sept 30, 2014 14:40:44 GMT -5
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Post by Boomzilla on Sept 30, 2014 14:55:46 GMT -5
It is a good guide, but it assumes you're using an AV front end (that automates much of the process).
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KeithL
Administrator
Posts: 9,945
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Post by KeithL on Sept 30, 2014 15:36:24 GMT -5
I think you've got it right. Start out with the sub and mains set so they are at about the same level at the crossover frequency. (If either dominates things at that frequency too much, you won't be able to tell when the non-dominant one adds or subtracts from the dominant one.) Adjust the phase for the most output at the crossover frequency. Now go back and make sure you have the crossover set so the sub "meets" the mains cleanly, with minimal dip or bump. (This would have been hard to do, and wouldn't work very well, until the phase is more or less right.) Now that the crossover is set right, go back and tweak your sub level (if necessary). I wish to run a 2.1 system with a subwoofer handling everything under 80 Hz. When I was using my Oppo BDP-105 as a preamp, setting phase was easy - Set the phase dial on the sub to zero and tell the Oppo how far away from the listening position the sub was located. Now, however, I plan to use the (full-range only) XLR outputs of the Oppo and let the XSP-1 do bass management. Although the frequency dials on the back of the preamp allow for turnover point selection, they have no adjustment for phase. Therefore, unless someone has a better idea, here's my plan for phase adjustment: Pick a crossover point & play a test tone (on repeat) at that frequency. With an assistant (with a SPL meter) sitting in the listening position, and me at the sub, I'll start at zero and then move the variable phase pot from marker to marker on the dial. The assistant will record the SPL at each dial marker. The point where the SPL is loudest (least phase cancellation) is the correct phase. Because even small movements of the SPL meter will make large differences in the level, we may have to repeat the sequence four or five times and average the results. Once the phase is set, it should not change unless the speaker or sub positions change. If there's an easier way to do this, please educate me... Thanks - Boomzilla
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KeithL
Administrator
Posts: 9,945
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Post by KeithL on Sept 30, 2014 15:52:16 GMT -5
That seems like it should also work. Just remember that you need to start out with the sub and mains operating at very similar levels at the crossover frequency (the one you're measuring). (If one or the other is a few dB louder, you won't notice the effect of the other adding to it or cancelling from it, and you're only going to get a null or any sort if they're at VERY similar levels.) I've also heard of a method where one uses the LOWEST SPL to find inverse phase & then sets to 180 different. Is there any benefit in one over the other?
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Post by pedrocols on Sept 30, 2014 15:55:34 GMT -5
What he said..++1 ^
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Post by pedrocols on Sept 30, 2014 15:57:17 GMT -5
I basically match the sub and the mains at the cut off frequency and like Keith stated, adjust the phase until you get the most spl.
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Post by pedrocols on Sept 30, 2014 15:59:59 GMT -5
Don't ask me how many times I need to go back and forth to adjust the sub level and play the test tone and then go back to my listening position...I have two subwoofers so I have to do it twice and after I match the two subwoofers crossover and spl....fun, fun, fun...
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Post by ansat on Sept 30, 2014 16:04:15 GMT -5
Don't ask me how many times I need to go back and forth to adjust the sub level and play the test tone and then go back to my listening position...I have two subwoofers so I have to do it twice and after I match the two subwoofers crossover and spl....fun, fun, fun... If you have a Radio Shack meter and a way to input into a laptop. Then this becomes much easier to use REW's RTA. (plus you get a bigger screen) Tony
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Post by Boomzilla on Sept 30, 2014 16:53:26 GMT -5
I've got a phone with a SPL app. KeithL's advice to match levels before setting phase makes sense.
Crossover frequency with only the mains running for reference level. Crossover frequency with only the sub running to match. Then set phase.
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