#71
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If you have an SPL meter, center it precisely between the sub and the main speaker closest to it (having reversed polarity to the main as CR suggested). I think it's more accurate than listening for the null, which can be tricky in some circumstances, especially if the sub is fairly close to the main. Last edited by Pampero; 04-01-2018 at 02:48 PM. |
#72
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#73
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I know that Barry recommends measuring between the sub and speaker to measure phase, but I think that is wrong. You want phase to match at the listening position, not halfway between the sub and speaker. So use the method he says (listening for or measuring for a null), but do it at your listening chair. |
#74
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SVS SB16 compared to JL Audio F113v2
Any sub with digital room equalization will have delay. In the case of my Gotham, it is 12 milliseconds per JL Audio. Since each millisecond equals one foot, you have to compensate for this delay either by moving the sub forward or the mains back. Or you use a pre/pro or external crossover and offset the distances correctly in the setup menu.
The sub’s phase control does not compensate for these large 10 - 12 mSec time delays. A change in phase and delay are not the same thing. The sub’s phase control operates as a fine tuning adjustment at the crossover frequency, allowing you to easily find the null. BTW, even if you don’t properly compensate for the overall delay, you will still get a null using the sub’s phase control - it’s just that the timing of your sub and mains will now be off by 10-12 mSec off due to the delay in your sub. Some people even like this effect as it increases the apparent bass. Any sub that uses speaker level connections will suffer from this issue as you can’t properly adjust the delay without an external crossover. Tom
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Main System: Amati Futura Mains Amati Homage VOX Center, Proac Response 1sc Rears, Three MC2301's for L,C,R MC 602 for the rears C 1100, MX 151, MCD 1100, MR 80 Nottingham Dais with Wave Mechanic Sumiko Palo Santos Presentation SurfacePro 3, RPi 4, ROON, WW Starlight Platinum USB, Schiit Yggdrasil, Benchmark DAC3 HGC MX 151, OppO BDP-95, JVC RS-500 DILA projector, 106" diagonal Stewart Luxus Screenwall Deluxe with Studiotek 130 G3 material. Lake House: Ohm F, MC 275V, C2300, MR 77, Rega P3 OnDeck: McIntosh MAC 4300v |
#75
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The reason I find it easiest to center the meter between the speakers rather than at the LP is that I can adjust the controls without requiring my presence in two different locations at the same time. There's no other benefit but it works well enough for me. This further suggests why phase and delay are not the same. In practice, you are adjusting "phase" to a single frequency which should arrive properly aligned in varying locations. Depending on your speakers' phase characteristics, perfect time coincidence might not be achieved everywhere (or anywhere) else in the spectrum. If you are adjusting at the crossover frequency (as Barry suggests...between sub and main) there should be no real differences in arrival (at that frequency) regardless of position. Could I hear that? I'm sure I could across 100 feet but less likely across ten. Perhaps all one needs to do to show that phase and delay are not the same is to attempt to adjust/align remote speakers in a large scale system using just rotatable phase controls. As respects the spec of the Gotham, I believe (dangerously assume, actually) that's a spec for propagation (or group?) delay through the system. Obligatory wiki cribbed cut and paste: In signal processing, group delay is the time delay of the amplitude envelopes of the various sinusoidal components of a signal through a device under test, and is a function of frequency for each component. Phase delay, in contrast, is the time delay of the phase as opposed to the time delay of the amplitude envelope. Last edited by Pampero; 05-08-2018 at 09:20 PM. |
#76
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Understand the phase / delay subtlety but with the JL Audio subs, I always wonder what frequency to use to adjust the phase.
80 Hz seems a popular choice as that is a default recommendation for the crossover point. But, what if you use a different crossover frequency? Do you in general, adjust the phase at that?
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Main Equipment: Kharma Elegance dB11-S, JL Audio F113v2 X 2, Block Audio Line & Mono SE Amplification, Bricasti M21 DAC, Antipodes Kala K-50 Server, Clearaudio Performance SE. Satisfy tonearm & Maestro Wood MM cartridge. Power: Shunyata Everest 8000, Sigma XC v2, Sigma NR v2, Block Audio PCs, Defender, ADDPowr Wizard Grounding: Shunyata Altaira CGS - 4 X Alpha CGS cables, Network : Supra Cat 8+, Twin (Nenon) Modified Buffalo GS2016 Switches, Keces P3 LPSU, Cables: Wireworld Platinum 8 USB, Wireworld Platinum Eclipse 8 Speaker cables, 6M & 1M Tubulus Concentus ICs, Other:Two PSI Audio AVAA C20, Multiple GIK products, Stillpoint Apertures, Stillpoint Minis and Ultra SS, Three 20 Amp lines, Furutech GTX - Gold outlets, Adona Rack |
#77
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The crossover point or frequency, depends a lot on your main speaker’s ability. In many cases, 90Hz is usually a good starting point and winds up being the final frequency. If you have a crossover, it will push anything higher than 90Hz to your main speakers and anything lower than 90Hz to the sub. This has no bearing on the phase adjustment whatsoever. Frequency and phase are independent of each other.
Once you select the crossover frequency, you adjust the phase so the mains and the subs are in “phase” with each other at the chosen frequency. These are examples of the mains and subs 90° and 180° out of phase: IMG_9641.JPG IMG_9642.JPG When adjusted “in phase”, both waveforms are in lock-step with other (the peaks and valleys are in phase). The waveform will look like this: IMG_9640.JPG Phase adjust makes the two waves’ peaks and valleys coincide, however, the problem as others mention above, being in “phase” doesn’t necessarily mean in “time” with the mains. Think of it as a NASCAR race… If all of the cars except for one start at the same time and make it around the track one whole lap, all of those cars are in phase with each other. If the lone car now pulls out of the pits and joins the others, he is one whole lap behind. If you weren’t watching the beginning of the race, you would never know that he was behind one whole lap. http://www.soundoctor.com/whitepapers/subs.htm Last edited by Cohibaman; 05-08-2018 at 01:51 PM. |
#78
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Good post Mike. I was thinking more about what test signal I use. If I remember correctly, Barry suggests using the 80 Hz tone from his disc. My question is if I am using a 100hz crossover, should I use the 100hz test tone.
Sounds like it doesn’t matter.
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Main Equipment: Kharma Elegance dB11-S, JL Audio F113v2 X 2, Block Audio Line & Mono SE Amplification, Bricasti M21 DAC, Antipodes Kala K-50 Server, Clearaudio Performance SE. Satisfy tonearm & Maestro Wood MM cartridge. Power: Shunyata Everest 8000, Sigma XC v2, Sigma NR v2, Block Audio PCs, Defender, ADDPowr Wizard Grounding: Shunyata Altaira CGS - 4 X Alpha CGS cables, Network : Supra Cat 8+, Twin (Nenon) Modified Buffalo GS2016 Switches, Keces P3 LPSU, Cables: Wireworld Platinum 8 USB, Wireworld Platinum Eclipse 8 Speaker cables, 6M & 1M Tubulus Concentus ICs, Other:Two PSI Audio AVAA C20, Multiple GIK products, Stillpoint Apertures, Stillpoint Minis and Ultra SS, Three 20 Amp lines, Furutech GTX - Gold outlets, Adona Rack |
#79
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Yup, use a test tone at the same frequency as your crossover point. That way the handoff from satellites to subs is seamless (from a phase standpoint).
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#80
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One should adjust phase and level whenever changing the crossover point using the same test frequency as you selected for your crossover point. The phase control on our JLs is probably an all pass network which is how it's often done. Phase angle and (output) level vary with frequency in dynamic loudspeakers but that isn't important since what you're looking to do is find the deepest null as has already been discussed here. It will be a specific combination/setting of phase angle and level that is easiest to find if you reverse polarity of the main speakers relative to the sub and adjust the controls until you find the deepest notch. That will always be a bit different for any change in crossover frequency. Where the crossover points are close (say changing from 80 Hz to 90 Hz) the differences may be small, but they will be there. The factors may appear complex, but the solution is easy to implement. Last edited by Pampero; 05-08-2018 at 09:32 PM. |
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