Subwoofer connections

July 18, 2021
 by Paul McGowan

For more than three decades I have strongly advocated the high-level connection of subwoofers—where we connect the output of the power amplifier to the input of the subwoofer.

What amazes me is that still to this day, that viewpoint is considered radical.

The vast majority of subwoofer manufacturers would have you connecting their subwoofers through low-level inputs as supplied by your preamplifier. Their reasoning is simple. The output of a preamplifier is cleaner and more direct than what happens after a power amplifier has processed it.

My good friend, John Hunter of REL subs is one of the few subwoofer manufacturers agreeing with me.

And here’s the thing. The majority of subwoofer manufacturers are correct. There’s no argument that the output of the preamplifier is cleaner, purer, and more direct than the output of a power amplifier.

So why the debate?

Because they are missing the point. Subwoofers should not stand out in the system. The whole point of a subwoofer is to augment the performance of the main loudspeakers. We don’t want to hear the subwoofer. We want to pretend as if it were a perfect appendage to the main speakers. To make that happen we need to do whatever we can to get closer to matching the sound of the main speakers—a perfect pairing.

We want the characteristics of the power amp to color the output of our subwoofer in an effort to more closely integrate it.

Hope that helps.

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40 comments on “Subwoofer connections”

  1. The industrialized world has become a very noisy place and like many humans i’m sensitive to noise. My recent comments regarding subwoofers and most digital audio applications ring true from experience.

    I dislike subwoofers for several reasons, primarily the young kids today in our neighborhood who crank the bass up in their $40k-$60k custom automobiles. From a distance of 50 feet away inside our house you hear and feel the resonance of the car chassis. No fundamental note or harmonics just resonating sheet metal noise.

    Most subwoofers are poorly designed and when improperly placed in domestic listening environments they perform similar to auto stereo boom cars. First the enclosure rings when the woofer is turned up and these boxes energize/excite the room creating resonances and standing waves that muddy up the midrange and cause listening fatigue. Further, it’s difficult to integrate these stand alone separate boxes to seamlessly integrate in terms of time and phase with the primary speakers. It’s easy to point to their location and constantly be reminded your hearing a separate speaker, a band aid so-to-speak.

    Growing up during the chaos and turmoil of the late 60s and early 70s the realization of just how lucky i was, old enough for rock n roll, too young for Vietnam. Further acknowledge that i’ve been blessed to stand alongside several great mentors, teachers, friends and associates in this walk of life. Two of those folks were Siegfried Linkwitz and Brian Elliott. Two chums who worked at Hewlett Packard in Palo Alto that discovered their mutual passion for audio spending much of their spare time experimenting, building and measuring loudspeaker designs which primarily focused on dipole radiation patterns.

    Some of the first interesting consumer audio subwoofer designs introduced in the 1990s as compared to the M&K and Velodyne boxes of the day were the Mirage BPS-150/250 a push-pull design in a box, followed shortly thereafter by the Sunfire True Sub with it’s dual driver minimalist enclosure which sonically bettered when compared but easily overdriven and the Celestion SL-6000 system which were true open architecture dipole subwoofers. Push-pull designs excite the box less short of crafting a woofer enclosure out of granite, X material or carbon/aluminum honeycomb.

    It wasn’t until the late 80s when i first heard Brian’s custom built, fully active music system with dipole woofers that i realized just how musically inaccurate subwoofer boxes are. For the first time we could clearly hear the fundamental note, the harmonics and the decay of the low frequency information in musical balance and harmony with the primary speakers. Pitch accuracy, transparency and a purity of sound due to the dipoles open architecture which didn’t excite the room nearly as much or cause my ears to ring. The construction was fairly straightforward – 8 each 12″ woofers mounted in a push pull configuration on a five foot tall open baffle. Visualize four 12″ push pull per side.

    The best commercially made audio system for low frequency performance these ears ever experienced was the Meyer Sound / Ultrasound system that Frank Doris wrote about in The Absolute Sound vol. 18 issue 89 Late Summer 1993.

    ftp://gdead.berkeley.edu/pub/gdead/interviews/absolute-sound

    If you want a reference as to what the ultimate subwoofer design should sound like, go listen to thunder. Especially those lightning strikes in your backyard where you feel the energy and electricity of the lightning followed shortly thereafter by the tight snap, crack, pop, boom and then decay of the thunder. It’s naturally organic, dynamic, exciting and never fatiguing.

    My best advice before you plop down serious money for a boom box, do yourself a favor and first invest in a high quality preamp and power amplifier. In my experience, i’ve consistently found greater musical return investing in high performance separate electronics across the full 10 octave range of music as compared to the sometimes questionable need to focus on the lowest octave delivering so much more musical information and involvement. These are fundamental building blocks in terms of processing the music’s signal path beginning with your recording’s.

    Next up – digital audio listening fatigue. We first started making live digital recordings with the Sony PCM-F1 44/16 digital audio processor in 1983 before the advent of DAT. Those early A/D convertors were horrible sounding but this digital mediums low frequency performance was stunning when compared to our humble Nak and Sony cassette decks. That said, the upper midrange and high frequencies were a sonic mess and it hurt to listen to these recordings at any reasonable volume for any length of time. Over the years digital audio has vastly improved.

    I always find it interesting when folks gather to listen to digital music, they either sit or stand still. Then, when the source changes to LP’s or analog tape they’re up and dancing around the room to the music.

    Humans and the acoustic music we create are analog, digital audio is a representation of sound and a great storage medium but at it’s essence, oftentimes sounds artificial and feels synthetic.

    Why is that? / Go figure / Stay tuned…

    PS -> perhaps if Paul can come up with a competent analog to DSD convertor he might be able to persuade and convert some of us analog dogs to build a digital music library. Then, the real issue becomes how to catalog, manage and deal with the massive storage issues arising from transferring all my analog tape, LP’s and CDs to a completely different digital storage medium when compared to PCM.

  2. That’s exactly why I use a pair of Alpine – ‘SWS BE-45’ bass engines (butt kickers) under my seat.
    All the feelable bass that you could ever want without the offensive BOOM, BOOM, BOOM coming from your car or driving your neighbours crazy in the adjoining apartments,
    AND at a fraction of the price.

    How long since you’ve heard this gem?

    https://www.youtube.com/watch?v=ek4nEGcffmk

    I’ve always loved that mournful solo at the end.

    1. Indeed, it’s been a great while. Not plumbing the abyssal depths, but even over the little speakers on this Dell ChromeBook, the drums have pretty good, sharp transients. It pleasantly surprises me sometimes. I’ll have to stream the album through the stereo. Later. And so to bed.

    2. I was never a purveyor of Carly back in the day, at the time was far more interested in Black Sabbath, Strawbs, Nazareth or similar. I have a new appreciation in recent years for singers like Carly, Kate Wolf, Nanci Griffith and Mary Chapin Carpenter (and the new storytelling Taylor Swift)! Thanks for this link, I will add this to my library and swing by the local record store for a vintage copy when I am out later (unless they were all snapped up yesterday during Record Store Day).

  3. If the inherent or wanted (?) colorations (in the crossover range) of the power amp are that important wouldn’t it be logic and better installing a passive subwoofer driven by an identical power amp. Paul’s recommendation results in adding the colorations of the power amp and those of the power amp integrated in the subwoofer.

  4. I for one agree and endorse what Paul says.
    His advice on subs has helped me enter the digital audiophile World and it has opened my eyes and ears to music i have listened to for decades with outstanding additional detail.

    Thank you.

  5. Zu Audio told me to connect the sub directly to the speakers (or from). in line with what Paul said, it cannot get closer to the speakers than that

  6. Too bad Dr. Goodears is turned off by his personal experience with subwoofers. Those young guns with their oversized subs in their cars are bass heads. They like the ”feeling” of that slam going through their bodies. That’s not music and is a far cry from what I experience in my system. I have a pair of RELs connected to the amplifier’s speaker outputs. Once you have the phase figured out and the cut-off frequency (not too high guys) you’re off for a unique listening experience. Paul has it 100% nailed down.

    1. Turned off? I’m not a sadist!

      Here’s some advice from the website of a gentleman who developed a few original ideas implemented into an original subwoofer design back in the mid 1980s.

      “I have been doing volunteer work for several years with elderly people with severe hearing losses, and I have seen the frustration and anger that are brought on by these losses. We now know that many of these people developed their hearing problems because of exposure to high noise levels when younger.

      Many audio/video systems, as well as home, portable and auto stereo systems are capable of volume levels potentially damaging to your hearing. Please use common sense, and listen to your movies and music at safe levels now so you will still have the ability to hear and enjoy them in the future.”
      – Richard Vandersteen

      Two of the loudest concerts attended were Hot Tuna at the Auditorium Theatre in Chicago 1972 and the Peter Gabriel So Tour Oakland Coliseum 1986. Tony Levin’s low frequency pounding was so intense we had to leave our main floor seats just to escape the intensity of this noise.

      In both instances, my ears rang for several days. Of the 150 + Grateful Dead shows attended over the years i never once walked out due to high SPL or aggressive sonic distortion. They always cared deeply enough to have their own sound engineering crew and high performance PA systems.

      That said, there certainly were a fair percentage of magical performances and clunkers for that matter. (enter smiley face)

      1. Quite true Dr. Goodears, I’ve also experienced some loud concerts in my younger days. I’ll always remember a Who concert at the Montreal Forum in the mid 70’s where we had to leave before the end because our ears couldn’t take it anymore. And the bass was way exaggerated. When we were back out on the streets we could barely hear cars pass by, our ears were in ”shut off” mode. After that whenever I went to a concert I carried ear plugs, just in case. I did use them a few times and it worked great. It permitted me to enjoy the concert instead of cringing at the decibels.

  7. I’ve experimented both ways. In the case of passive subwoofers there is no choice and I agree. In the case of today’s active subwoofers I prefer feeding with a preamp signal and more so with an external crossover where I have control of the slope gain and phase. (Effectively a 2 way crossover with high pass to the mains where their bass roll off becomes apparent)

    One of the reasons go along with what paulsquirrel said above. One of the other reasons has to do with integration. To my way of thinking, really deep going full range speakers effectively have something akin to having a sub built in. (The ability to hit those low bass notes with accuracy) resonances have to be controlled so as not to have an internal effect on the other drivers. With a properly built and matched subs, and the enclosures placed near the speakers, same toe in etc. the results can be very good. I prefer to keep my subs up off the floor 20in or more and extremely well isolated so they are coupled more to the room than the floor. The trick for me was finding subs that matched the speed and articulation of my mains. They roll off quickly below 24Hz, but for the music I primarily listen too that’s plenty deep.

    So like all things audio, there are preferences. Mine, as usual, are probably out in left field somewhere. 😉 ✌️

    1. I am with you on this one. I have also experimented both ways, and depending on certain factors find the speaker level method Paul describes to be slightly better. I do still employ this method on my desktop system (while the sub under the desk gets used as a footrest ha ha).

      But, for me anymore in most parts of the house it is all about aesthetics and convenience. I want the auto room correction of my equipment to analyze everything and set the crossovers and levels. I can tweak a bit with the settings after the analysis if I choose.

      I am long past wanting to scoot around with my ear on the floor finding the best spot for the subs as I’m getting far less finicky as I age in this respect. I also don’t want to see any wires or cables or cords, so they get tucked away out of site and have been downgraded to levels that allow for pliability.

      The speakers also just got an upgrade to aesthetically pleasing current issue Focals with eye appealing grills. All the vintage stuff went to others who can enjoy them instead. I am now all about neat and orderly, but that’s just me.

      1. Hello Larry,
        You missed only one thing as we age, …”neat, orderly” and lift-able. No more 60lb anything. I gave up my treasured Snell Type A II Improved s and Bryston 4B for Maggies and PS M700 monoblocks. Now I can fuss with the system whenever I want, not just when my nephew is in Philadelphia.

        1. YES! I didn’t think of that but surveyed all my equipment and other than the speakers it is all now 37 pounds or less! Even the speakers are only 55. My old vintage ones were 140 each. To me an excellent advantage and actually more fun because I no longer need help just to tinker and tweak!

          1. Neat and orderly only happens when I settle things. Weight hasn’t Been an issue yet. I can still bear hug and move 150 – 200 lbs while keeping my back protected. I do appreciate what you’re saying, but none of that is an issue yet. Maybe in 10 – 20 years it will be.

            If it becomes one, then headphones and a good headphone amp may be the solution. Until then, as long as I don’t need a crane or gang to move stuff the weight factor has very little effect on the equation, just sound I enjoy.

            1. Hmm…the ‘weight lifting maximums’ might be the difference between being in your early sixties as compared to being in your mid seventies…just sayin’ 😉

              Wires & cables are behind my gear & therefore impossible for anyone to trip over, so who gives a….

  8. John Hunter of REL is not a personal friend of mine. And although I did read the manual that comes with every REL sub, I’m not influenced by him or his company. That might help.
    And in audio over the decades I learned (learnt ?) that you only must trust your OWN ears, most of the time not the ears of the “experts”. That helps too.
    So, over the years, I connected my my 2 (REL-) subs in all possible ways to the rest of the audio chain.
    To the power amp, to the (terminals of the) speakers and to the pre amp.
    The subs I own now, REL T9/i, are (after a lot of trial and error) connected to my PRE amp.
    Result : Much better integration and sound than when they were connected to my power amp.
    End of story for me.
    I know, not every expert likes it when you trust your own ears more than you trust them, but USUALLY it’s the best way to go.
    And I’m not talking about technical matters. Then I trust the expert !!
    BTW. : connecting the subs IN PARALLEL to the main speakers gave surprisingly good results (you gotta watch the impedance, do the math before making this connection !).
    I never connected the subs in series to the main speakers and amp.

  9. I have a pare of JBL LSR-310S powered subwoofers.
    They both have balanced and unbalanced inputs on them.
    But I found out the hard way, that these things don’t like unbalanced signals.
    But sense I wanted to sublimit the Avantone Pro CLA-10 studio monitors, I had to do something else.
    And so, I used an unbalanced to balanced converter to rectify that.
    But at the same time, I wanted the sound of my vintage Fisher 800 receiver to hit them as well.
    And so, I took a cupple of small power transformers and put them in the signal path, to brake the speaker level down to line level.
    And then, I went in to the unbalanced to balanced converter.
    I got it all to work.
    Long story short, the whole system sounds grate!

  10. SntbcwS,
    I thought that once you mentioned the Sasha Daw as the speaker your wife chose, but i was wrong.
    Thanks for correcting this.
    The first time I heard (the original version of) the Sabrinas they sounded amazing to me.
    Connected to an Audio Research tube amp. Wonderful sound.
    So they should and surely will satisfy a non audiophile (?) person like you.
    And, not totally unimportant I guess, they save you about 20k in pounds. For almost the same fun as with DAW -:)

    1. Besides the sound, my wife loved the dark titanium colour. Audiophiles can go on about all sorts of stuff, but in my case the sale was largely determined by the colour.

      1. Not only is color important, but the single, unified cabinet of the Sabrina is more elegant and the weight of the Sabrina is a lot more burglar friendly. Fits in the room, rather than dominating it. 😎

    1. Apparently not. New input mains power…. Special windows and Sheetrock. New speakers. New audio immersion system. Optical data transmission where possible. Line conditioner. Extremely respectable vinyl rig. Great electronics to drive / listen to. Dealers coming and going for system set-up. Quote after quote of high end audio manufacturers.

      So when you get serious let us know. 🙂 Or was someone looking over you shoulder when you were writing….

      1. The new mains was first an issue as our car charger stopped working and the existing supply would not power our new kitchen. Audiophile glass is -60db, ours is -40db and recommended for bedrooms and also for my office at the front of 5he house. I concede new mains flex to the consumer unit is shielded – mostly Belden at $11/m. I use CAT6a for audio (AQ Pearl – their cheapest cable) because a local supplier does factory terminations. The fibre is primarily future proofing and for fast video. I was happy with Harbeth, but my wife hated them and she chose Wilson. The spatial system is equally, if not primarily for lighting, plus my son is on the design team. Audiophiles tend to hate Devialet Expert, but my family love it. My wife and I enjoy listening to records, but given my time again I’d buy a Rega P10. The audiophile thing in my system is a Shunyata Hydra Alpha.

        Any dealer should deliver and set up audio equipment, and the ones I know do. When I buy a washing machine or tumble dryer the shop delivers and installs it. Any retailer should look after their customers and if they don’t they should expect their customers to buy elsewhere or online.

        I like products that suit family spaces, which does not include subwoofers. If I had an audio room and lots of money I might make very different choices.

        1. All fair enough. So maybe the choices didn’t revolve around audio as such, but enough to justify. So sit back and enjoy when the opportunity arises. If you don’t think you’re serious then that’s fine, but your writings don’t convey that. If what you mean is your life doesn’t revolve around super high end audio, that’s a little easier to accept.

          Either way, I was joking / poking the hornets nest. Enjoy and thanks for your words.

  11. I have a pair of custom built stereo subwoofers that use 4 – 10 inch long throw subwoofers per channel in individual 3.5 cubic foot enclosures per side that mate to my modified Magneplanar MG20’s. After a couple of years playing around with electronic crossovers, I settled on running the MG20’s full range and crossing the subs over at 48 hz at 24 db/octave slopes. In this system the subs are powered by their own amps on a low level XLR signal from the electronic crossovers. I have enjoyed this system for years now, and it provides great entertainment and wonderful music, without any hint of problems with the bass output or distortion of the rest of the musical spectrum. I believe it is much more likely to obtain great sound today with the higher end powered and digitally controlled subwoofers. If these were available 25 years ago when I had my subwoofers custom built, I would have gone with the modern powered subwoofers available today. I would encourage everyone to give these subs a try, even with small stand mount speakers, because they can be configured to please almost any audiophile. (it may take some experimenting with room location)

    My stereo system consists of: Magneplanar original MG20 speakers with their crossovers and connectors changed to Mundorf silver and copper foil capacitors with Mundorf copper foil inductors. The connection to the speakers are by Furutech. The electronic crossovers are by Pass Labs with Emotiva monoblocks for the subs, AVM Monoblocks for the bass panels, and an updated Sonic Frontiers SFL-2 tube amplifier for the midrange/tweeter panels/ribbons. The preamp is a Sonic Frontiers SFL-2, and I have Synergistic Research cabling throughout. I use a PS Audio P10 power plant to power the preamp and sources, PSA Base plates for vibration isolation, and PS Audio digital sources for stereo, and for part of the amplification for the movie surround system. As you can see, I am probably an obsessed audiophile!

    Enjoy the weekend!

  12. Some of my fondest memories of subwoofers were the first Hsu black cloth wrapped, passive cylindrical tube subs that connected with simple wires by Paul’s method. The bass was pure and well integrated. No fuss. No bloat. No overkill. Now it seems everybody wants a powered sub that brings the roof down.

  13. Haha SntbcwS, who are you kidding ?
    I’m sure you are the only non audiophile person on the planet, no in the solar system, with 22k (euro) Wilson speakers and a Devialet amplifier…. and all the other “things” Mike mentions.
    So, like Mike, I hope you let us know when you finally decide to buy “serious” stuff to replace all these “inferior” components.

  14. I have had three subwoofers, all REL. Today I only use one ( in my video system ), I sold one, and one is for sale. All, when in use, were connected to the power amp. I imagine most folks know this but perhaps it is worth repeating. There is an easy way to tell if your subwoofer is properly dialed-in. If you can tell that your subwoofer is on when you are playing music then it is not properly integrated into your system. If you cannot tell that your subwoofer is on until you turn it off, then you are good to go.

  15. I have 3 subs on 3 different systems all are married to each system to the point most guess have to be told where it is! All 3 when placed correctly cause the music to be more emotional experience to the listeners and all are hooked up to the preamp of amplifiers. I normally break them in away from the wall almost in open air then move them closer after at least 40hrs of play time. All but the large NHT sub sound independent of the mains when played like this the NHT I have used in large auditoriums and it still couples to the closet wall and starts to pressure room up with it.

  16. I understand what you are telling us Paul, however I believe It Is possible to seamlessly integrate a powered sub with the mains through low level inputs (be it full range or a stand monitor)! I know, as that is what I have achieved with a sub pre out. With my pre amp (Emotiva) sub output crossed over at 50Hz low pass and my Sierra 2EX monitors at 50 Hz high pass, they seamlessly portray a dynamic one-voice bass bandwidth that extends deep, tight and fast. Timbre, Tonality, Voicing and Punch sound all equal to the monitors’ neutral character! Actually, I never “hear” my sub at all, even when it is playing the bottom of cathedral pipe organ resonances. It’s output is always centered between the monitors as if They are playing the 20HZ fundamental tone. Never calling attention to itself, it is as stealthy and surprising in its smooth even delivery as I’ve ever heard (even though the sub is located to the left of the left monitor, in the far left corner)!

    Possibly, I’ve lucked out with a Synergistic match between my power amp (Emotiva) and my powered sub (Axiom). Maybe the low 50Hz hand-off allows for a better blend of voicing, keeping the critical deep bass 2nd & 3rd order harmonics located with the much faster Seas 6″ EX woofer?!? Either way, with the genre of acoustical non-amplified music I enjoy listening to, I feel I’m missing Absolutely Nothing in the bottom end…or for that matter, anywhere in the mid to top end!! 🙂

    Ted

        1. Ok, well, I bow to the master, as I’ve only been
          ‘doing it’ for 46 years without any music studies 😉

          But I will say this; that component compatibility
          does not guarantee system synergy.

          1. No need to bow, FR…just send Money!!! 🙂

            You’re right, matching component compatibility does not guarantee System Synergy, but in rare cases, it just might! Been “speaker cable” testing these past 2 months and have been BLOWN AWAY by the performance (and low cost) of the BlueJeans CANARE 4S11 Star Quad 11Ga speaker cables…has transformed my overall sound presentation so much, seems like I have New 3-way speakers (I don’t, just Very Good 2-way monitors+sub)!!!

            Ted

  17. Best bass I ever heard was at Harry Pearson’s playing a set of Scaena speakers with their own sub woofers crossed over electronically around 65Hz. Harry played a movie soundtrack from a CD called Lost World. One track had a real volcano recorded with the music that Harry said went down to below 20 Hz. The concrete floor was shacking and both my friend’s and Harry’s eyes were saucer shaped waiting for flying 18 inch woofers producing tons of super tight sub 20s bass.

    The woofer deign has only been used a few times. The boxes were small so the resonance was around 180 Hz. So a built in equalizer with a powerful amp was used with 12 dB/octave to flatten out the bass that unequalized rolled off from 180 Hz. That was the secret to the bass tightness. Below resonance a woofer doesn’t want to move. It just wants to stop. So the woofer had almost no bass overhang. As soon as the signal stopped the driver did. I only know two other companies that used this technique, McIntosh starting in the 70s and Pipe Dreams later. The important thing is a big amp, simple these days and a woofer that can handle tons of power. Since the driver is run below resonance in the box robustness is a fundamental need.

    The technique should be used more often.

  18. Hi,

    Yes, Paul, you are completely right with your post.

    Just one thing from the practical point of view: when I connected the Stellar S300 amplifier to the REL T9X subwoofer.
    This story turned out to be not so simple. Started from the special case of ground connection (this is clear explained at REL manual) and then another interesting thing: here I quote the kind explanation from REL support: “The S300 is opening the output connections when turned off or into standby. This will present a high impedance to the REL (not unlike plugging in an un-terminated high level cable – This is what is causing the hum and will not allow the REL to go into standby. As this is down to the design of the amplifier when it goes into standby and there is not a fault as such there unfortunately there is no way around this.” Regards, Igor.

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