2024 'Janus One' EQ adjustment

The basics have now basically been done for the current EQ and level (and phase this time) adjustments.  And I've given it a name to leave a milestone here, "Janus One."

It's sounding wonderful, a huge upgrade, even though I thought it was incredibly good (and basically better than anything else I've heard in a while) before.

I've eliminated the "Boost" aka "Listening Position" EQ.  Now it's called Normal and used for everything except movies--which have guests and use peripheral seating where there is maximum room gain.  Normal sounds way over the top at those positions, however audiophiles might find it ok at a meeting.

I've been able to eliminate Boost because the new EQ is so well tuned.  It isn't "sloppy" like the old Listening Position EQ, which featured boosts on top of boosts in some cases.

It's much smoother overall for many reasons.  A big part of it is the deliberate choice to NEVER use Graphic EQ's (GEQ).  GEQ's tend to increase roughness because they aren't precisely dialed in over existing depressions, and therefore often amplify peaks--and peaks amplify with gusto.

Each way and channel uses only 10 or fewer Programmable EQ's (PEQ), mostly as notches, but with a few highly tuned boosts also where they appeared to be needed.

They were all tuned using an oscillator, frequency counter, and chairside Digital Equalizer (DEQ) with all the critical listening being done in the listening chair.  Measurements were done with 1/6 octave 16k bin 'Analyzer' app, for the first time held in the center head (or sometimes ear) position with a microphone stand and new phone mount.   These are big improvements over previous tunings, where I often sat on the floor in front of the front DEQ's while tuning in the frequencies and deciding on their need for attenuation, usually using the DEQ itself to figure out what the critical frequencies were.

In the process, I discovered that it worked substantially better in both channels to invert the polarity of both subs compared to their previous positions (which in one case had been "inverted" and is now moved back to Normal).  The sub markings are in question, as I perhaps installed both replacement plate amplifiers correctly, but they somewhat agree with the ambiguous Speaker Pop app which becomes very unreliable with subs, which is no surprise because I originally set them up using Speaker Pop.

Anyway, in recap, I think it's good to go over what the change has been.

When I started, the listening position response was very bass shy UNLESS I engaged the "Boost" EQ.  That added a bunch of GEQ boosts to the normal set of PEQ cut used in all settings.  With that selected, I got a pretty rough and tumble bass response in the Right Channel:

Right Channel, Boost EQ, July 13

When I finished Janus One, there was no longer any Boost EQ as I had designed the NORMAL eq to have sufficient bass at the listening position without using any GEQ boosts (but using some very small PEQ boosts).  When I finally got the sub phase correctly set, I measured this:

Right Channel, Normal EQ, September 12

Wow!  Very smooth overall (especially from 20-400 Hz) and closely fitting what I think is the correct room curve.  No need for a Boost curve and not too bad elsewhere in room or house (just a tad too much bass elsewhere which often works like a pleasant loudness curve for background listening).  In one intermediate adjustment I had the bass completely flat with the midrange, but I decided the bass was far too weak sounding, so I raised it by increasing the sub level.

The left channel had been looking much better than the right channel, I originally thought, but by the time I'd finished the right it was clearly no match anymore.  (Now I wonder why I ever thought this was good.)

Left Channel, Boost EQ, August 1

The finished Left Channel Normal EQ isn't quite as smooth as the right is still, but much nicer for the most part.

Left Channel, Normal EQ, September 12

The bass from 20 Hz to 300 is very smooth, but above that there's some roughness.  The only way to fix 400 Hz is with a boost near there, I thought the region around 1kHz looked smoother in some previous measurements.  I try to avoid boosts and they need to be done very carefully, so not done yet.  Careful listening tests might be warranted too.  This includes "PB1" the current latest Panel EQ, which only has one boost in the left channel (but looks like it might need 2 or 3, I think now.)

Looking at it now, I think this could use some more work asap, it's still no where near as perfected as the Right channel.  I was bogged down for a week with the phasing issues so I couldn't quite see that.

While doing this EQ I learned at least one lesson for sure.  Always try inverting the phase between subs and panels, even if you think you have the correct phase.  And take a good measurement to compare them.

And many others I've noted along the way.

One part of identifying this milestone is to write down ALL the details so it's not lost later.

Details:

XLR polarity inverter on Left sub channel

Right Sub set to "Normal"

Left Sub level: -7

Right Sub level: -10

Sub DAC: -6.5

Panel DAC: +9.5

Panel DEQ Gain Compensation: +3.0

Tact Levels:

R 0

L -2.0

Panel DEQ Delays

L: 10.0 ms (design default)

R: 10.0 ms

Sub DEQ Delays

L: 8.72 ms

R: 8.40 ms

(Honestly these delays don't look small enough compared to the panels, there should be more delay differenceI think, but these were dialed in years ago after some testing and thinking then.)

NO GEQ's whatsoever!  (Except in Movie mode presently)

Left DEQ's, sub on top

I see now that there are actually 3 boosts in the left panel, and the upper frequency ones aren't doing very well.  The chairside PB1 memory is identical.  This looks like a mistake perhaps, did PB1 get overwritten by PB3 by mistake???  Looks like a week or two of rework is needed on left to banish the remaining lumpiness, not just a new boost or two.  But I've decided my knees need to rest from kneeling so I'm not going to do it now.  That's going to be "Janus 1.1".  And also asap I should start measuring with my calibrated microphone and ARTA.  I believe my iPhone 8S and Analyzer app is accurate enough for most purposes, especially when supported in my new microphone stand mount, but super fine tuning around 1kHz and above might benefit from something even better.  The beauty of using the phone analyzer is that it's so fast I can just whip off measurement after measurement, only a fraction of which have been displayed here, which is invaluable for mass EQ tuning.  You've got to test every little change because actually it's all virtually unpredictable.  (Some supercomputer with a description of every object in the room in precise detail would be the minimum requirement.)  Cut and try is the only hope.  Once you've more or less zoned in on the correct notch and boost frequencies, you can take the time for more exacting but time consuming measurements and even finer tuning.

I notice now that there are cuts near the 400 Hz depression, which I thought I had eliminated...

The better tuned Right channel does have only one boost in the panels (and it's just the low one at 133 Hz).

Right DEQ's, sub on top

The Movie presets simply add a set of GEQ's to an earlier set of PEQ's with no boosts.  (The PEQ's are not very critical, but the sub version should not have any boosts which may go awry in the far field.  It would be better to re-do the PEQ's for the back seating position from scratch so they don't need GEQ's, but that's another big project for later, heck I'm not even done with the Normal yet I realize now.

Left Movie GEQ

Right Movie GEQ

The subs also have Dynamic EQ (dEQ), a form of limiting.  It rolls off the deepest bass (to prevent overexcursion) when the level is too high.  SVS probably already has such a thing built in to their plate amplifiers to keep their speakers from blowing up, but it's not as limiting and protective as mine.  I investigated this a few years back, and determined I got the best results with two identical dEQ's in sequence, that way it can compress the maximum amount fast enough when needed.  And I eliminated the standard compression DYN because it isn't needed on the subs and I don't think it sounds good.  3 dEQ's was too much so I only use 2.  The only thing that may be out of adjustment now is the Threshold level, which depends on sub DAC and sub amp levels.  It can be re-tuned by watching the indicators when playing a bass test track.  On most recordings it should not trigger at all.

Sub Dynamic EQ page 2

Sub DEQ page 3

**** Wait!

I thought I had remembered much better looking Left channel response.  And indeed I had a stunningly good measurement on August 29 in an earlier post.  This was made using the chairside DEQ (shown in photo) so it automatically had the polarity changing adapter I added later (though I added it to the sub not the panel, the effect on response should be the same).

Left Channel, August 28

Left Panel peq's, August 28

The only difference I see here is that I subsequently added at boost at 182 Hz, replacing a 0dB filter at 824 Hz.  It's hard to believe that would cause a depression at 400 Hz, or 1kHz depressed compared with 900 Hz.  Perhaps the Chairside was not showing the EQ that was actually operating because it needed rebooting.

Running through all the published spectra and adjustments shows nothing inexplicable.  I had a mound around 1khz when I had a wide filter at 1013.  There was consistently a depression at 900 Hz before I moved the boost there instead of 1013.  Fine tuning that nearly leveled the whole region.  All looked believable, it didn't seem there was any hangup.

Stuff in the room may have been moved around a bit, but not that much I would think.  It still looks like the point where everything goes south is when the 182 Hz boost was added, which doesn't make any sense, but seems worth trying.  Tiny time delays might have been involved (I found the front panel DEQ's had 0.1ms greater latency, don't recall if that was with or without optical connections though the optical connections made no more difference than that, if at all).

Anyway, that's a wrap for the Janus 1.0 summary.  We can start to imagine Janus 1.1 now.