SVS SB16 compared to JL Audio F113v2

[Pampero]

Originally Posted by crwilli

The JL Audio subs have an electronic delay in them that requires they be closer to you. However, you can speed up their sound by using the phase adjustment..

I don't believe there is a delay in the JL electronics package. Adjustable phase is not the same as time delay and won't compensate for a time offset. Barry mentions this in his tutorial. You are right in that you are trying to align the wavefronts by using phase control but you will still won't have corrected any time offset. I agree that getting phase and level dialed in using the approach Barry Ober suggests (shooting for the null by reversing polarity) is a simple and accurate way to get phase and level adjusted in one swoop. This is an extremely fiddly adjustment. Extremely fiddly!

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.

[Pampero]

Originally Posted by SAPHANA

I own SB16 and F110. SB16 only wins when it comes to power, so I use it purely for HT. F110s blend in seamlessly when playing music.

One thing I don’t understand is I set the low pass filter frequency and slope the same, but SB16 simply cannot blend in well at all.

I was never able to get an SB16 to give me what I was looking for in my rig. BTW, I'm not sure the knee would necessarily be the same for these two subs.

[Mike-48]

Originally Posted by Pampero

I don't believe there is a delay in the JL electronics package. Adjustable phase is not the same as time delay and won't compensate for a time offset.

A couple of things . . . change in phase and delay are essentially equivalent. By adjusting the phase to match, you are taking care of delays.

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.

[W9TR]

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

[Pampero]

Originally Posted by Mike-48

A couple of things . . . change in phase and delay are essentially equivalent. By adjusting the phase to match, you are taking care of delays.

With respect (*if I recall correctly!) this is not the case once you exceed one wavelength. I'll cheat for simplicity's sake by saying (with apologies to nit pickers) phase is relative, delay is absolute. Varying phase will give you alignment within the scope of a single frequency "cycle," the one you are measuring. That should be enough for correcting phase alignment at crossover in speakers located in our small spaces but cannot compensate for frequencies outside of a narrow band at a small distance. In our typical rooms it is sufficient as a practical matter. Proper phase alignment has proven a boon in my rig but phase and delay are different phenomena even though both are time domain artifacts. Could one say it's a matter of scale? I think so if that helps to explain the differences.

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.

[crwilli]

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?

[Cohibaman]

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

[crwilli]

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.

[Cohibaman]

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).

[Pampero]

Originally Posted by crwilli

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?

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.