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JL Audio Fathom v2 Digital Automatic Room Optimization (DARO) Review
by ct_acoustic_frontierJuly 06, 2022
In this article we're going to look at JL Audio's new Fathom v2 series of subwoofers, and in particular the implementation of their new automated room correction algorithm called DARO (Digital Automatic Room Optimization).
An Overview of the Fathom v2 Subwoofers
JL Audio's Fathom subwoofers came out in 2004, and so in 2014 it was about time for a refresh! The Fathoms have been pretty much universally praised, even by the hardcore HT enthusiasts with space to spare for dual 18" subwoofers.
The Fathom lineup remains unchanged in terms of cabinet and driver configurations. There are four models:
F110 v2, a single 10"
F112 v2, a single 12"
F113 v2, a single 13.5"
F212 v2, a dual 12"
So what's new? I'm pretty sure that the driver and cabinets are unchanged (or at least JL don't make a fuss about the changes), so what's new is the amplification and signal processing electronics. Here's a quote from the manual:
"compared to their predecessors, Fathom v2's have been improved with all new digital signal processing and a 20% increase in amplifier power, further enhancing their outstanding dynamic capabilities"Update 1/10/16: apparently there have been tweaks to both the driver and cabinet.
Perhaps the biggest new feature is the Digital Automatic Room Optimization built into the new Fathom v2 platform. This is an easy-to-use system that does not require any computer. Simply plug a mic into the front of the subwoofer and press the CALIBRATE button and in about three minutes up to 18 bands of digital equalization have been applied.
JL Audio are about the only company I can think of who have created an automated equalization process that works with multiple mono subwoofers. You can simply set one Fathom to MASTER and all others (up to 10) to SLAVE and then daisy chain each slave sub with XLR cables from the sub designated the master. When set up in this way all subs are measured and corrected as a single entity.
This is critical because multiple mono subs spread about the room smooth the overall response through room mode cancellation and speaker boundary interference fill. If you measure and correct multiple mono subs individually then you are not doing things right (unfortunately there are a few automated systems that make this mistake including the Dirac Live implementation in the Emotiva XMC-1.
At Acoustic Frontiers we never take manufacturer marketing on face value. We test and evaluate every product we sell to see if it actually does what it says it does and to find its limitations. So we tested out DARO in our showroom and tried to trip it up :).
The following charts show the before and after correction frequency responses for five different positions. All responses are with no smoothing.
A pretty easy test this one. The pre-EQ response has no major dips. DARO has corrected it to a very flat line. It's also applied a pretty substantial boost under 30Hz.
Test two was easy, and DARO passes.
Here the pre-EQ response has a big peak at 30Hz and a dip at 55Hz, followed by another peak at 70-80Hz. Again DARO shows it is up to the task, and again we see that boost to the lowest frequencies.
For test four we threw in a few sharp phase cancellation dips. DARO did a good job and did not try to correct these.
For test five we had a pre-EQ response with a major peak at 30Hz and a significant dip at 50-60Hz, followed by a phase cancellation dip at 95Hz. DARO flattened the peak very effectively, and also boosted the wide dip by about 6dB. It did not try to correct the sharp narrow dip. Again we see the boost applied by DARO to the lowest frequencies.
So how good is DARO?
As an automated correction system I'd have to give DARO a 10/10 for ease of use. It is really simple to use and unlike ARO in the v1 Fathoms seems very robust - simply set the MASTER GAIN at 12'o'clock and hit the CALIBRATE button.
In terms of the results I'd give it a 9/10. It's really done a very good job. It has not tried to correct narrow phase cancellation nulls (which cannot be corrected) but has applied some limited boost to wider dips. It does a really good job equalizing out peaks.
There are a couple of things I would question, the main one being why does DARO always boost the ultra low frequency output? A casual observer might have expected it to correct only to the anechoic response of the subwoofer, which for the F110 is a -3dB point of 25Hz. Instead we see a -3dB point of 17Hz if we examine the average of all five corrected response tests.
[caption id="attachment_3362" align="aligncenter" width="640"] Average of the five post-DARO responses[/caption]
Maybe there is something more sophisticated going on here as I did hear the output of the sub changing through the DARO calibration testing, so it's possible they are also including room gain into their calculations. I'm going to get in touch with JL and ask them for some more information.
One thing missing from DARO is ability to measure multiple locations and from that extract a more averaged response that is then equalized. For a single listening position at subwoofer frequencies I don't think this is a limitation. For home theater use I do think this is a limitation but then in most cases you would be turning off DARO and using the room EQ system in the pre-pro or AVR.
It might also be nice to be able to set custom target curves and boost limits, but this would require a more complex interface and potentially using a piece of PC software or an app for calibration.
There is some flexibility post DARO to change the target curve using the ELF (Extreme Low Frequency) TRIM. However like on the Fathom v1 this seems to influence a very wide frequency range. Here are indicative adjustment ranges:
[caption id="attachment_3363" align="aligncenter" width="640"] ELF TRIM adjustment range. Baseline is DARO ON P4 trace, -- is ELF control rotated to -12dB, ++ is ELF control rotated to +3dB[/caption]
In conclusion given our testing we have no hesitation in recommending the new JL Fathom v2s with DARO.Update 1/10/16: in our listening tests the new v2 has proven to be an even better sub than the v1. It simply disappears, not drawing attention to itself in any way, and provides amazing control, articulation and dynamic capabilities.
Much confusion still exists about what a room correction product does, what problems it can (and cannot) solve and therefore its 'place' in a modern high quality sound reproduction system. Part of the challenge of understanding room correction is that it requires a reasonable level of understanding of sound quality, acoustic science, acoustic measurement and psychoacoustics (how humans perceive sound). The majority of the articles I have read online or in print magazines do not cover the fundamentals in enough depth to allow the curious and committed reader a chance to understand room correction on anything more than a cursory level. By the end of this article I hope that you will have learnt enough to judge for yourself what room correction can and cannot do and how best to apply it in the context of a world class music or home theater system.