JL Audio Fathom f110v2 powered subwoofer Page 2

I started out in multichannel, feeding the subs—either one or three—from the Sub/LFE (low-frequency effects) channel of my multichannel server. In that arrangement, the main speakers are running full-range while the sub gets only the LFE channel on tracks that have one. Post calibration, the results were rewarding, even though on music the LFE channel mostly tracks the low-frequency content of the front channels and contains little unique information. On a recent recording of Jean Guillou's organ transcription of Mussorgsky's Pictures at an Exhibition, performed by Zuzana Ferjencíková on Jean Guillou: Organ Works (SACD, MDG 9062089), I didn't hear any new notes, but I did perceive more solidity and definition in the pedal tones, whether I used a single f110v2 or three. As I turned up the volume, the balance between those low notes (so essential to this transcription) and the rest of the spectrum tracked more naturally than without the sub. On their own, the Revels (five of them for this test) could handle the load at any tolerable level, but the addition of the subs expanded the scale for which Guillou's original stereo recording of this repertoire (CD, DOR-99117) is revered.

All that is fine for a discrete multichannel system with a 5.1 system with large, full-range loudspeakers. But what about systems with smaller speakers, or with a prepro or AVR? With such systems, some form of bass management is required. The f110v2 subs do not offer a high-pass–filter option to roll off the bass from the main channel. Such full bass management is, of course, built into all prepros and AVRs and, with experimentation and effort, I could implement it in JRiver or Roon.

However, JL Audio offers an easier solution: the CR-1 Active Subwoofer Crossover (footnote 2). I inserted one between the L and R output of my preamp and the Left and Right inputs of the power amps and the subs.

D.A.R.O. cannot adjust the CR-1's settings; the CR-1 must be adjusted by the user independently of D.A.R.O. The CR-1 manual recommends making all the CR-1 adjustments before running the D.A.R.O. processor, but to me that seems illogical: Any settings in the CR-1 depend on what is downstream, and those settings will be compromised if the subs are EQ-ed post hoc (footnote 3).

720jl.2

The CR-1 has adjustments for crossover slope and frequency, sub/sat balance and damping in the crossover region, and JL provides excellent instructions for setting them by ear. I followed those instructions, but I also found it helpful to observe the OmniMic V2's live display of in-room frequency response during the process. The settings were unremarkable—except for my choice of 90Hz for the crossover, which is higher than I would normally choose, and high enough that at the top end, the bass can become directional; JL Audio recommends a high crossover point, so that more of the bass is provided by bass-specialist subwoofers—and more is equalized.

JL Audio also recommends stuffing ports and raising the crossover above the range where the port operates so that all low bass is from nonresonant, sealed woofers. I declined to stuff the ports, but with the ports' output down 20dB at 90Hz (footnote 4) and a 24dB/octave crossover slope in the CR-1, the ports should not be audible in this setup.

Deep listening
How do you audition a subwoofer? The obvious answer is to haul out the bass-buster recordings you use to show off your system. So that's what I did, in both stereo and multichannel. Since the CR-1 has a bypass button, I could instantly switch between my main speakers (stereo or 5.0) run full-range and the same set with one or three f110v2s taking over the bass.

With my stereo bass chestnuts, Béla Fleck and the Flecktones' The Flight of the Cosmic Hippo (CD, Warner Bros. 9 26562-2, CD) and Mendelssohn's Organ Sonata for No.1 in F, with Thomas Murray (CD, Raven 390, originally from LP, Sheffield Town Hall S-13), the bass was tight, deep, and full. Both of these recordings are endowed with powerful lows, which even a single f110v2 delivered in spades while delineating individual tones clearly enough to reveal the harmonic progression of the music.

From there, I went on to other old favorites such as the Telarc bass drum on the final march of the classic recording of Holst's First Suite for Military Band by the Cleveland Symphonic Winds (SACD, Telarc 60639); I relished its physical impact. In the same league but in multichannel, there's the final exclamation point (with bass drum) concluding Holst's ballet music from The Perfect Fool (SACD, Reference Recordings RR-146). No problemo, in stereo or multichannel, with either one f110v2 or three. That's what a good subwoofer can do when you are listening for bass and not paying a lot of attention to the music.

I moved on to a performance with a solo guitar where the music usually distracts me from the excellent sound: Tárrega's "Capricho árabe" from La Guitarra de Torres, played by Stefano Grondona (CD, Divox CDX 29701). The guitar's range extends below the 90Hz crossover of this setup, but this did not pose a challenge for decent speakers or a well-integrated sub. Grondona was recorded up close in a reverberant acoustic that endows his guitar with great warmth and weight. I have loved this recording for decades and carried it with me to many hi-fi shows, but it never sounded this good before. Replacing the excellent low end of the Studio2s with the tautly controlled f110v2 more completely disambiguated the sound of the guitar's lowest strings from that of the wood, without diminishing the warmth and weight of either.

Buster Williams's acoustic bass fiddle on Griot Liberté (SACD, High Note HCD 7123) goes down further below that 90Hz crossover; with the bass managed by JL subs, both the plucked and bowed tones are better defined in tonal character and space than with the Revels running full range.

To my surprise, the newfound clarity extended above the crossover and into the lower midrange. "I Heard It Through the Grapevine," the stereo original of the classic Marvin Gaye performance, on The Marvin Gaye Collection (SACD, Motown B0003502-36), is an anemic recording; even switching in the JL f110v2 couldn't add lipstick. With the multichannel remix, which is much better mastered, the addition of one or three JL subs cleaned up the bass and rounded and projected Gaye's voice. Creedence Clearwater Revival, on Cosmo's Factory (SACD, Analogue Productions, CAPP 8402), in stereo, benefitted both from improved bass definition and from enhanced vocal clarity.

720jl.grill

I had to try my go-to recording of Finzi's Come Away, Death (SACD, 2L 2L-064-SACD). From the first note of the piano, I felt the presence of the instrument and that strange, detailed illusion of a large instrument on legs with space around it. Kielland's voice seemed more rounded, yet lighter. Stereo with one f110v2 or multichannel with three were equally ravishing, save for the ingratiating ambience of multichannel. I thought I really knew this recording, but the JL Audio subs and the CR-1 have enhanced my respect for it and my joy.

Instead of continuing with an extended list of striking moments (footnote 5), let's jump ahead to an orchestra-and-chorus extravaganza: Prokofiev's cantata Alexander Nevsky in a magnificent recording by Thierry Fischer and the Utah Choirs and SO (SACD, Reference Recordings "fresh" FR-735). From the opening chord, there was satisfying weight and texture in the lower strings; in the "Song About Alexander Nevsky," it was easy to hear the inner structure of the instruments and chorus. With the opening of the apocalyptic " Battle on the Ice," the double basses and the low brass growled with menace, and the timpani and bass drum made the ice-breaking tactile and almost visual.

Having accepted that the addition of the f110v2 and associated stuff suited me, I played a new 2L recording, Ole Bull - Stages of Life (SACD+Blu-ray, 2L 2L-159-SABD), which includes music for violin, pianos, and orchestra by the 19th century Norwegian virtuoso, often called "the Nordic Paganini." I loved an earlier recording of Bull's Violin Concerti (SACD+Blu-Ray, 2L 2L-067-SABD) from the same crew, so I had high expectations of both the music and the sound.

I was charmed and lulled by the sweet, sedate beginning of "Largo posato e Rondï capriccioso"; it put the image of the soloist and orchestra in my mind. Then, about 5 minutes in, a sforzando tutti hits with the impact of a small bomb. There's the timpani, right there on the front left, to the back of the orchestra (confirmed by the instrument map in the brochure); despite its apparent distance, it has weight and shape and specificity. Switch off the JL subs and, yeah, it's a nice tutti but nothing special.

Conclusions
I have learned that despite my abiding predilection, crossing over from main speakers to subwoofers at the lowest possible frequency is not a global solution. If the main speakers are placed for balance and imaging and not for optimum bass, and if one is using high-performance subwoofers with capable room EQ, such as the JL Audio f110v2 with D.A.R.O., a higher crossover point means that the optimized subwoofer is effective over more of a frequency range where room modes are important.

A corollary benefit of bass management with equalized subwoofers is that the lower midrange becomes clearer and more transparent. This is apparent on human voices and many instruments.

I found that this bass management is subjectively more satisfying than simply having a subwoofer playing the LFE channel on multichannel music recordings.

The JL f110v2 is a mighty mite of a sub, conceding little to its larger brothers. Placing it up front in a stereo system, crossed over to the main speakers and, most crucially, matched to the room with D.A.R.O., it can extend and clarify the bass response of your system. For a large room and/or a multichannel system, the f110v2 can be daisy-chained to additional f110v2s (or e110s) to increase the amount of bass power available, to reduce the influence of room modes and let D.A.R.O. finish the job.


Footnote 2: See Larry Greenhill's review of the big brother f212v2 and the CR-1 for more details on the latter.

Footnote 3: I exchanged comments with JL Audio about this. They said that they would reconsider their recommendations.

Footnote 4: See fig.2 here.

Footnote 5: Here are three. The sprung-from-a-bow opening of Britten's Variations on a Theme of Frank Bridge (2L Records 2L125, SACD), the deep, plush bass ballast of Handel's Concerto grosso in G Major (Pentatone PTC 5186737, SACD), and the ripe bass and guitar that drive Keve Wilson's rendition of "Alone" (Pure Imagination, Composers Concordance Records COMCON002, CD).

COMPANY INFO
JL Audio
10369 N. Commerce Parkway
Miramar, FL 33025-3921
(954) 443-1100
ARTICLE CONTENTS

COMMENTS
Bogolu Haranath's picture

I understand that, KR his going to be reviewing the new NAD M33 for a future issue of Stereophile ..... May be KR could use the built-in Dirac Live of M33, and give us his opinion about, whether that Dirac Live can modify/extend/enhance the bass frequencies of his Revel Studio2s, without the assistance of the separate subwoofers :-) .......

Kal Rubinson's picture

Wait for it..........................

Bogolu Haranath's picture

Fantastic ..... Looking forward to reading that review :-) ......

Ortofan's picture

... eliminate the two-sub setup from consideration?

Did you ever consider trying two subs, with each placed midway along the side walls?
Or, two subs, with one in the front and one in the rear, in diagonally opposite corners?

https://www.aperionaudio.com/blogs/aperion-audio-blog/dual-subwoofer-placement-for-your-home

Jack L's picture
Jack L's picture

...... along the side walls?" quoted Ortofan.

Take it easy. This is no rocket science.

I've installed 3 active subs for my stereo tube amp system at home years back: L, R & L+R. They work like a chime as they bring back so so much (mid-bass, DEEP deep bass) music missed from the original recordings, which I would have never known without those subs.

So why 3 subs: L, R & L+R channels? Simply most concert halls are equipped with mim 3 overhead microphones: L, R & L+R to capture the overall acoustic perspectives of the performances.

My L sub is seated 2 feet behind the L standspeakers, about 6 inches from the back wall, likewise for my R sub. The L+R sub is placed exactly midway bewtween my L & R front speakers.

I hooked up the 3 subs direct to my design/built tube phono-pramp WIHOUT any costly complex cross-over electronics, using the low-cut network already built in each sub.

Simplicity provide better music.

Room acoustic 'compensation' electronics? I don't need it.

Trust my ears-on & hands-on experience on subs.

Listening is believing

Jack L

Bogolu Haranath's picture

Jack, you are describing 2-channel system ..... KR is talking about multi-channel system in an odd shaped listening room with non-moveable furniture :-) .......

Jack L's picture

..... listening room with non-moveable furniture" quoted B Haranath.

Hi

First off, I am NO movie fan but stereo audio only lover. So multi-channel sound systems for movies is not my cup of tea (again, no coffee for me as well).

IMO, multi-channel sonics is a huge MESS of synthesized sound, often ear deafening, failing to produce the right soudstaging & imaging, even without any subwoofers. So why worry about precision placement of subs ??????

I would NOT waste time & my hard-earned cash on unreal synthesized sounds!!!!!

Jack L

Bogolu Haranath's picture

KR listens to surround sound audio for music, not home theater sound effects :-) .......

Kal Rubinson's picture
Quote:

I would NOT waste time & my hard-earned cash on unreal synthesized sounds!!!!!

Nor would I! My sources are discrete multichannel recordings wherein the various channels reproduce the sound of the performers and the performance space in a way that stereo cannot. If it is not recorded this way, I revert to good stereo recordings played in stereo which better than not bad. This is not HT as there is no display and no video. (I guess you don't read what I write, so.......................?)

Jack L's picture

Hi

I would be interested in how "discrete" are the signals picked up by various channel microphones are processed. Mix-down & then regeneration is not longer 'discrete' at all !!!

Jack L

Kal Rubinson's picture

I have many which are simply 5 mics into a 5.0 package. In fact, I particularly relish the ones that are direct mic feeds prior to any mastering. Of course, there are others which use "spot" microphones and those are subtly mixed into the main 5 channels.

Jack L's picture

Hi

So the positioning of the 5-channel playback loudspeakers would be very very critical. Otherwise, it is hard to reproduce correcly the spatial ambiance of the original recording venue.

Jack L

Bogolu Haranath's picture

Jack, you are also taking about 2-channel mix down of 'Decca Tree' 3-microphone placement :-) .......

Kal Rubinson's picture

Why did you eliminate the two-sub setup from consideration?

I tried the two possibilities for 2 subs in this room and both were unsatisfactory.

Did you ever consider trying two subs, with each placed midway along the side walls?

Not possible as there is a couch on one side wall and a large cabinet on the other.

Or, two subs, with one in the front and one in the rear, in diagonally opposite corners?

The one diagonal where this was possible (note this room is one leg of an L-shaped space) resulted in an audibly unbalanced performance without and with EQ.

Deandome's picture

I know it's gonna take some time, but we really need to weed out the word 'slave' in discussions about audio components (and flash photography, industrial controls,etc.).

I include myself in this 'we', BTW. This isn't a criticism of KR or JLA; these usages have been around a long time...though I've long thought it a bit jarring as whenever I've seen it.

I don't think this merits much debate or discussion; I'm not here to start a flame war.

It's not political...it's just time.

Jim Austin's picture

The proper use of "master" and "slave" in the context of audio will continue to be allowed here, with posters being encouraged to be courteous of the feelings of others--not only those offended by the term but also those of good character and liberal views (in the broader sense, not the political one) who innocently use long-accepted technical terminology. Perhaps we can all work on making this adjustment--I intend to do so in the magazine--but no one should be condemned for the occasional slip.

While it probably does merit discussion and debate, this is neither the time nor the place.

Jim Austin, Editor
Stereophile

Deandome's picture

Thanks. I hoped to better emphasize this is/was a general point, not a condemnation of Kal or this publication*, which I have silently cherished for decades (*in my mind, it's still a curiously-sized, perfect-bound joy!).

Jim Austin's picture
I understood, and did not intend my response as a criticism. However, I thought it appropriate to set and express a policy for Stereophile. Best Wishes, Jim Austin, Editor Stereophile
supamark's picture

we take a cue from biology and use mother/daughter (like in cellular biology) or the more generic parent/child. It shows a hierarchical relationship, would be understood as well as current terminology, and is much less offensive to pretty much every rational person. It has the added bonus (to me at least) of being rooted in scientific terminology.

Jim Austin's picture

A lot of people have been working on replacing "master/slave". There are some good alternatives.

Jim Austin, Editor
Stereophile

Kal Rubinson's picture

I think parent/child is not a good analogy in the present case since the master and slave subs are fundamentally co-equal but are distinguished by one acting as the controller while the other is the controlled. We need other and better, I think.

Jim Austin's picture
Editor-Writer? :-)
Bogolu Haranath's picture

Primary - Secondary ? :-) ........

Bogolu Haranath's picture

Husband and wife or, wife and husband ........ Depending upon whoever is the controller and, whoever is the controlled :-) .......

Bogolu Haranath's picture

Gladys Knight & the Pips .....
Echo & the Bunnymen :-) ......

nirodha's picture

The only one that has the right to have an issue with the term "slave" is the sub itself.

Ortofan's picture

... master and grasshopper to be less objectionable?

dcolak's picture

Let's also stop calling killers killers, dictators dictators, rapists rapists etc.

New-speak is popular these days.

tonykaz's picture

it's not critical, is it?

A person could live a happy life with no more capability than a pair of LS3/5a and a NAD 3020 original ( the latest Digital version is not so dam good ).

Properly pressurizing a full Large Room of 4,000 cubic feet requires engineering, measurement tools and unique gear. Who has access to that kind of thing? i.e. Bob Katz writes about setting up his latest Florida Mastering DynAudio System and B&O seem to accomplish it with their latest BIG fully digitized Class D Masterpiece Loudspeaker system.

I've experienced seamless Full Range Systems using Subwoofers, turn off the AC Power to the Sub and the magic is gone, Poof ! A person can't quite notice the Sub while its in the system doing it's work.

But...

Subs not set properly cause problems.

My Sennheiser HD 600 series headphones and Schiit Amplifiers reproduce the ultra low frequency parts of the Bombay Dub Orchestra recordings, most loudspeakers ( that I've ever heard ) can't do so. ( vinyl can't go low enough either, its a digital capability ). Bob Katz can hear it with his engineered gear and incredible Mastering System.

Deep bass capability is worth owning and worth the commitment, it's one of the last steps in being an Audiophile.

Prepare for complaints from family and neighbors. ( maybe even a call from your wife's Attorney ( a fellow audiophile, in my case ).

Tony in Venice

Ortofan's picture

... for LS3/5a users.

https://www.grahamaudio.co.uk/products/sub3/

https://www.hifi-advice.com/blog/review/loudspeaker-reviews/loudspeakers-passive-reviews/graham-audio-ls3-5-and-ls3-5a-with-sub3-part2/

tonykaz's picture

Hmm, this speaks to JA2 say'n how big our Audiophile Tent is.

LS3/5a to Diavelet and Beolab.

I'd be calling for Scotty to beam us up but we're already well into the 21st Century of advancements and I don't know what more we could be asking for.

Tony in Venice

Bogolu Haranath's picture

LS3/5a + subwoofer makes it the 'Voice of the Universe' (VOTU) :-) ........

Kal Rubinson's picture

"it's not critical, is it?"

It is to me because the music I listen to most requires it in order that it have a natural balance. Can't have an orchestra without the double basses.

tonykaz's picture

And this little Sub is only a $4 Grand addition.

Any decent Phono Cartridge ( that probably struggles with Basses ) will cost two or three times as much yet have a lifespan of 6 months or less.

Are your neighbours complaining?

Is your frequency response graph only showing 50ish SPL?

What the hell, $4,000 seems cheap for filling out the System's performance envelope of usefulness.

Tony in Venice

ps. Now, with the new Subwooofer, is your home system the equal of Carnage Hall. ?

Kal Rubinson's picture

Are your neighbours complaining?

They have not complained in many years and, then, the only complaint was when I pushed a (now nameless) speaker that was lacking in the bass in a fruitless effort to get some kick out of it.

I generally try to be a good neighbor.

Bogolu Haranath's picture

JL Audio makes Gotham subwoofers ...... Four or more of those could make the listening room equal to the rocket launch pad at the Kennedy Space Center :-) .....

krahbeknudsen's picture

This is an interesting subject. When I sit in a symphony hall often I hear very little deep bass compared to recordings.
Indeed, the Helmholtz (lowest)resonance (A0) of a typical double bass body is 65 Hz, while a low E (deepest string) is around 42 Hz. This is true for the whole violin family. The sound of deepest string is the result of psychoacoustics because the instrument has no resonance there. We think we hear deep bass but it is not there.

Kal Rubinson's picture

Indeed, it is not so much frequency extension since the main speakers can go low enough for me. The major issue is that the main speakers are situated and oriented for soundstage/imaging but not for optimal bass. Adding one or more subs at room boundaries and with EQ serves to make the entire <100Hz range cleaner and more effortless.

tonykaz's picture

Right there is the essence of your entire review. ( I think )

Pro people doing live gigs would call it bass reinforcement, done with bass bins which are horns about 3 feet wide x 4 feet tall x 3 feet deep capable of staggering SPLs and controllable by the sound guy running the boards.

Powered Subs make life easier for the system's amplification.

I've fallen in love with the Meridian Actives since the mid 1980s when I was importing them. Now, Active loudspeakers are the only things that make sense. Maybe I'm not a tweaky Audiophile

Tony in Venice

Bogolu Haranath's picture

DSP controlled active speakers like the D&D 8c, reviewed by KR and JA1, are the future ..... In the near future they will also incorporate larger diameter or multiple woofers :-) .......

Bogolu Haranath's picture

It is possible that, the Dirac Live could do that, below 100 Hz, cleaner and more effortless from the main speakers, without the help from separate subwoofers :-) ........

Kal Rubinson's picture

Not so far. The constraint is that, currently, DL only EQ's each speaker independently. DL3 with its advanced "Bass Control" option, not available for the M33 at the time of the review, will enable the use of each of the 5 full-range speakers as "virtual" speakers + subs with the low ends integrated.

Bogolu Haranath's picture

You (KR) could do a follow-up review of DL3, when it becomes available :-) ......

Bogolu Haranath's picture

A total of four 8" woofers in the Studio2s is almost equivalent to a single 15" woofer in bass output ..... A total of six 8" woofers in Salon2s or F328Bes is almost equivalent to a single 18" woofer :-) .......

Kal Rubinson's picture

That presumes:
1. That they are tuned and equipotent in the sub range.
2. That they are placed where a sub will do the most good.

Bogolu Haranath's picture

When reviewing the Devialet Expert Pro, JA2 said that, the Revel Salon2 woofers made his windows rattle more than 20 feet away :-) ........

Kal Rubinson's picture

Rattle is easy. Music is hard.

Bogolu Haranath's picture

You (KR) may be familiar with this, TJN wrote a review of the NAD M17 V2 surround sound pre-amp processor with built-in Dirac Live for S&V magazine :-) ......

Kal Rubinson's picture

I did, too.
https://www.stereophile.com/content/music-round-95-wolf-nad-page-2

Bogolu Haranath's picture

So, I presume you (KR) bought a new plasma display :-) .......

Kal Rubinson's picture

OLED

Bogolu Haranath's picture

Hope it is 8K, Dolby Vision, HDR, IMAX Enhanced :-) .....

dc_bruce's picture

I think they have two purposes. One is to achieve in-room bass response down to 20 Hz; and the other is to provide bass power at higher than 20 hz bass frequencies. While many so-called "full range" speakers claim bass response to 40 or even 30 Hz, their ability to do so at higher than modest output levels without significant harmonic distortion is limited. Even a fairly modest subwoofer can deliver a robust, largely undistorted output at the lowest musical bass fundamental of 42 Hz. (Yes, I know pipe organs and synthesizers can, and do, go lower.)

One thing, you didn't mention in your review Kal is whether these subs provide the sense of "spaciousness" or "hall sound" that others report from larger subs that feature robust 20 Hz extension. I recall one review of a smaller sub that, in so many words, said that the sub under test provided nominal 20 Hz extension in a "yes, but" sort of way that failed to give that sense of spaciousness yielded by larger subs that also provided 20 Hz extension.

Your graphs of the degree of room correction provided by multiple subs was very enlightening and certainly an incentive for people to consider 2 or 3 smaller, cheaper subs as opposed to one behemoth. It also shows (as if this needs to be proved any more) that a good parametric equalizer is essential if the sub is to provide a net sonic benefit to the system rather than be just a boomer.

Fishman1234's picture
Glotz's picture

And with smart placement (which took 5 minutes!), they (REL T-5i's) integrate beautifully into MG-1.7i's with stereo coherence, smoothness and grace.

At $1200, the pair provides stereo bass support, maintains the original sound of my amp, increases the back-hall depth perspective, image stability and widens the stage perspective without bloat or over-push. John Hunter of REL has some salient things to say about stereo sub operation over single sub output referring to this increase in back-hall detail recovery.

It also keeps the investment rational for more audiophiles, as the investment is half that of my main speakers. For apartment dwellers, it also provides excellent extension to 30Hz (but no deeper really) and this keeps the neighbors at bay, even with highish SPL's at night.

At almost $2000 for pair of REL T-7i's, they are probably even a better value, but they also have forward-firing woofers which may complicate (any) speaker integration attempt, or over-power smaller rooms with the addition of larger passive radiators.

I don't mean to take anything away from JL Audio. I always enjoy Kal's writing. This is just another way to skin a cat and it might be helpful to others to add that 2nd, mirrored sub or investigate REL's different approach.

MFK's picture

If you have the space and don't have to worry about neighbours, at least one subwoofer is a no-brainer. Why not? I don't own Harbeth and am not advocating for Alan Shaw's approach but his ideas are always interesting. Check out the sound samples with various brickwall filters.
https://www.harbeth.co.uk/usergroup/threads/bass-response-how-deep-should-my-speakers-go-for-a-lifelike-sound-at-home.1659/

drh3b's picture

I think it would be interesting if you would audition Rythmik or other ID subwoofers. I know you are aware of these brands as you are on AVSforum. :)

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