"Musical" subwoofers? Advice please on comparing JL subs

Northman,

First off, do yourself the best favor you could ever do in this sport, go listen to the Bryston Model T's.   Most likely you will find the standard 'Passive Crossover' version out there; that is what my pair started out life as.  I run tremendous power here with my large space, 2000 watts per channel at 4 ohms and I decided I wanted to upgrade my T's to the 'Signature' version which uses massive, Mil-Spec built (gorgeous circuit boards with huge air core wound inductors) external PX-1 crossovers with triple dedicated inputs on the back of the speakers for each section.  Ian at Axiom wanted me to ship the speakers back to him for the conversion and James Tanner at Bryston supplied me the pair of PX-1's.   I decided to do the conversion myself as I have a nice cabinet shop in my barn with all of the equipment needed and that way I don't have to pack up two massive speakers on a pallet to ship to Canada and risk damage.   It took me about three days of work to complete everything using OEM parts Axiom shipped me.   The difference in performance with the PX-1 is just breathtaking!   Find the Signatures to listen to.

Secondly, you should really look at the Axiom EP500V4 , this is a fabulous Sub; plus the amp is designed with a DSP circuit which will not allow the sub to be over driven or distort, you cannot kill these speakers.  It's all Axiom/Bryston proprietary designs and ALL of the components are made in Canada, no overseas Chinese stuff.  SVS was completely built in China and uses switching power supplies from what I saw (I burnt up six of their subs, both amps and drivers).  JL I don't know much about but I believe from what someone told me that they use some Chinese components.

Thirdly, I think that if you are using properly designed gear, you should not be using any room correction type software to EQ your room.   I have Anthem for my preamp and it's a wonderful piece with powerful ARC software with a fancy Mic.  But after running it and allowing the computers to 'balance' the room, I turned it off and went full flat with just my Model T's and the amps/preamps and 3 subs.   Hands down, no software EQ  at all, flat just beat the hell out of the software.   When I spoke with James at Bryston, he told me that they never use any software room correction in their spaces and Ian at Axiom said the same thing.   Properly designed equipment should not need anything other than your own playing with speaker placement and location and phasing; which is far more fun too.

If you happen to be in Northern New England, you are welcome to stop in for a listen before you do anything.

Fastfreight wrote: "But we do have two stereo main speakers... and there is stereo information in bass information (not talking about LFE or .1 here). Stereo subs SUPPORT the soundstage and imaging. Not sure if Swarmy subs do this all over the room or not. Seems dubious."

The Swarm is normally sold with a single amplifier to drive all four subs, in summed mono configuration. An optional second amplifier can be added, such that the left channel signal goes to the subs on the left side of the room, and likewise for the right side.

Imo true subwoofer-region stereo is rare at best, but the second amplifier can significantly enhance the sense of envelopment even with normal program material: Set the phase controls on the two amps 90 degrees apart, in what’s called "phase quadrature", thereby synthesizing the phase differentials one might experience in a large room. Credit to David Griesinger for this idea.

Obviously this phase-quadrature technique can be used with two conventional subs provided they have continuously-variable phase controls. I’d suggest locating the two subs along the left and right side walls.  

Duke

@northman: And therein lies the problem. While you may think poetry is beautiful, I may think it's just a bunch of rhymes that bore the crap out of me (which it does). So terms that mean different things to different people are not useful when trying to pin down objective answers. That's why those terms should be thrown out. My "musical" is that it reproduces exactly what an instrument sounds like. If someone is a Beats headphone user, their idea of musical might be something completely different.

A pair of Rel S510

@slimpikins5, thank you for all the great advice! I think the Model Ts might be a bit small for my space, and I'm not sure that 2000 watts is enough for my needs. I want my system to make a statement. And ... I am kidding... The room I'm setting up is tiny, 10' x 11', and I'm going with small stand-mounts for near-field listening. Still, maybe some day I could hear your set-up, which sounds incredible. I actually am in northern New England--outside of Burlington, VT. 

Also, I love how accessible the Bryston staff is. I've owned a lot of Bryston gear and I've emailed a few times with James Tanner as well as messaged with him on audiocircle. In fact, I just had an old amp spiffed up at the Bryston "repair center" near Montpelier. Forget a sterile office building; it's an old Victorian schoolhouse that's been converted to office space. It was fun seeing the amps and whatnot all over the place.

I like what you say about DSP. Needless to say, there are many opinions about all this!

@jssmith, it takes all kinds of universes, doesn't it? For me, the fact that terms have multiple meanings is hardly cause to throw them away; in fact, that's what makes them interesting (but not "subjective"). I like that "musical" can mean different things, and in fact that's the pleasure of art. That said, I was not only asking about "musical subwoofers" but also something that should have a clinical answer: at what point in the frequency range can most humans begin to discern notes, melody, tone, ... music? (Also, if you can identify poetry as "a bunch of rhymes" then you are in fact recognizing a genre, a type of expression with complexity and nuance, whether you like it or not.) I'll add that my son got a free pair of Beats when he bought some Apple product a few years ago; OMG, that woofy, vague bass is exactly what I don't want in a sub!

That a boy Northman.... Burlington. My old stomping grounds when I was ski racing on the US pro tour. I was down in town by Sugarbush in Warren and had a place at Stratton. Green mountain had their first shop and roasting facility in the town parking lot on route 100. Spent a fair amount of time on Church Street at the French Bistro in Burlington with my then GF from Montreal. I think you have the movie. Fun!
I am down at the Maine Coast about 3 hours from you. Drop by and have a listen. I am spending what I have on this stuff as they say I cannot take it with me, but actually I have a deal worked out and I am.  No devil sticks 7000 watts

I have the e110 & know it to be an excellent subwoofer. It is accurate; tuneful (standup bass vs electric bass vs baritone clarinet all sound quite different--as they do IRL); goes plenty low for me; and has more than enough power for me.

It lacks the room correction software than the Fathom (I believe) has, but I’m fine not having that.

For the application you describe, the e110 should be more than fine. In fact, it should be exemplary.

Where it would not be more than fine would be:
-- in a huge room
-- where you expect disco SPLs to happen at the lowest frequencies
-- and where you expect the lowest frequencies to be in the mid-to-upper teens (ie, 15 - 18 Hz). Subs that can go that low cost as much as a good used car & are worth the $$...

But for normal music listening, e110 is your friend.

It also has one considerable advantage over the Fathom: a filtered high pass output that goes from the sub to your power amp, carrying the main signal (for main speakers) sans all frequencies below 80 Hz. Believe me, this is an unusual feature. Unless you have a separate electronic crossover, or a receiver that does bass management, you will appreciate this feature.

@northman: " ... at what point in the frequency range can most humans begin to discern notes, melody, tone, ... music"

20Hz

No kidding. Notes are just frequencies. Melodies are just a sequence of notes. Tone is mostly a measure of pitch of a repetitive sequence of notes over a certain time period. And timbre is a combination of frequencies.

If you think someone incorporating the low A key of a piano is music then it starts at 27.5 Hz. If you think music starts by someone plucking the E string on a 4-string electric bass then it starts at 41Hz.

Seriously, if you think this tone can be incorporated into something called music, then it begins at 20Hz.

Personally, I think you're wasting your money with JL. A subwoofer's job is flat response, low extension and as high an output as you need for your application. Beyond that it's all about room placement, EQ and room treatment. It only makes sense to consider JL if unobtrusiveness is of primary concern, but there are still much cheaper options (unobtrusiveness is why I have three Paradigm Seismic 110 in my living room and a Velodyn Microvee in the bedroom). If you check data-bass.com you'll see how JL performs (not good) against cheaper subwoofers. I'd much rather have three SVS than one JL for the same money.

@slimpikins5--NICE! I bet the French bistro was Lunig's. "The Valley"--Warren, Waitsfield, and the Sugarbush region in general--is just beautiful. I live about ten minutes from Smuggs and skied there all the time when my kids were young. By the way, I was skiing (not ever close to your league!) in the mid 70s, when Stowe was still a small town and Okemo had poma lifts.

@desktopguy, thanks. I've heard much the same about the e110. And: I'm not using a big room, I don't need to go below 25hz, and disco sucks. (Yes, I was one of those guys in the 70s; now I love it!)

@jssmith, I appreciate your comments. I really do understand what you're saying: "notes are just frequencies." I'm drawn to the art part more than the physics, so I'll just add that Thelonious Monk, Jerry Garcia, et al were doing something pretty special with those frequencies.

Good Morning,

 Back again with my opinions and findings and report of the crow I had for dessert last night!  Well, after pontificating that most of us can not move our subwoofers around the room, I tried exactly that; 
My Carbon Limiteds (or any sub I tried) lived just inboard from my main speakers, perfectly nestled between speakers and my low center equipment rack / wall mounted TV.  A fairly common set up, and esthetically pleasing.  Well, recall my issue with boominess of bass on certain tracks (certain heavy bass frequencies).  My REL Carbon Limiteds have wireless LongBow, but I was not using it as the sub's location was very close to my amps.  So I reconnected the wireless, and began shifting the subs around a bit. (This is one area that an 80lb subwoofer beats a 110 lb subwoofer hands down!). I ended up with one way over in the right hand corner and one way over in the left hand corner of the room, both facing inwards. 

Low and behold!  The reinforced boom at around 30hz was minimized, and the soundstage and airiness was enhanced!  I could not locate the subs with my eyes closed and everything sounded better!
I listened for hours with a smile on my face!  So old dogs can learn, it just takes patience.  My purist mentality is still preserved (no EQ), and I am loving the REL's, which, as many keep saying, completely disappear
when set up (and located) correctly.  My phase switch setting did change
as well by the way.  Also, perhaps the imaging and soundstage benefit from 'less stuff' between the speakers?
Smiling in Maryland...Ken

Just an observation to report in with. I had an early version V4 sub from Axiom which had the switch type phase control. It only offers two or so options for phase alignment. Axiom redesigned it into a fully variable full range phase control in later version V4 amps. Ian did an experimental design amp for the monster EP800 V4 which had a custom response curve in two switchable curves. A normal ’flat’ response curve and one with a neat boost in the middle bass ranges for some real punch. He spent hours in the anechoic chamber developing the curve. He offered to custom build me a new amp for the EP800V4 with the dual response curves and he even engraved the amp panel with two settings; I asked him to do Bourbon Smooth for the flat position and Gin Gut Punch for the boosted ’party’ setting. He got a kick out of that and its what I have on my amp, nicely laser engraved. Here is one thing he also did, he included the new full range phasing control vs. the original switch setting phase I had. I was able to see the results of the phasing now upon installation of the new amp and I can say that it is amazing! a two position switch doesn’t cut it, its useless. When you get down on the floor and fine tune the phasing, you dial it in with just the slightest turn one direction or the other and there it is!  Keep in mind that where it all syncs up varies with the room, the sub placement, how many subs you have, etc.   If you understand what zero beat is with radios; for example zeroing a receiver frequency exactly with Fort Collins WWV, this is pretty much what you do with a variable phase control. Its fast and easy and the subs are in total sync, there is no boomy out of phase difficulty with the bass, especially in odd locations in the room. I think a variable phase is a must have when it comes to sub woofers and I know that Axiom/Bryston has it now on all new subs they offer... the best single change they made.

When I think back to when I got into 'subs' using the large name subs out there (and I tested a few including the Paradigm super monster with some outlandish power and if I recall a 15 inch driver), none of them did anything right for me.  The bass was always just bass, mucky, bland heavy handed bass, often shaking windows or dishes unnecessarily so.  What I have now is silky smooth, powerful musical, wonderful, perfect, BASS.   You don't feel like the bass needs to be adjusted up or down and changed for each track you listen to.  It all plays exactly like the recording engineer meant it to be played, it's perfect.   I think design is critical in subs.  My most beautiful piece is my Bryston Model T sub, this thing stands around 45 inches tall, 10 inches or so wide and 17 inches deep.  It's a slim, tall sexy looking thing in Black Ash wood veneer with triple 8 inch cool looking drivers.   Due to the smaller driver compliment, it really does the mid and upper range bass super well, but it is big on low end output too as it pushes a lot of air.  The EP800 with the dual stacked 12 inch drivers handles the freight trains very well :).   The single 12 inch Driver EP 500 is my sweet spot go to sub, I just love this thing.   They also make an EP600 which is a larger cabinet version of the EP500 and I'd love to test that one out.  Perhaps when I go to a four sub set up !

@northman

I hear you. My room is 12X11, so I know of what you speak. My near field system has two subs. I chose the REL T/7i over the JL simply because I value Class A/B over Class D in an analogue system. If I were digital I might not mind Class D. They are nearly the same price.
People just don't understand that in a small room there is barely enough room for 2 subs let alone 4. With record storage and equipment there is just enough room to walk.

EQ alone is better than no EQ if it's removing big peaks. This lets the overall sub volume come up.

EQ + optimal placement + bass traps = Glory

I may have mentioned this before, but if your room is rectangular, basic, consider the Room EQ Wizard room simulator as a less back-breaking alternative to locating ideal subwoofer location.

Tuberculin, Class D is not a digital amp. Class D is just one of the next levels of amp design nomenclature. They have Class A, Class B, Class A/b, Class D so on. People always seem to think that Class D means digital, it is not. In fact where Class D really shines in most designs due to some amps not having a lot of very expensive feedback circuit designs is in the lower frequencies. Class D amps can suffer from upper frequency harshness if they do not employ fancy feedback designs. For Subs, Class D is probably the best option which is why most companies use it. It’s very efficient, produces huge power with almost no distortion at low frequencies, very low loss and heat which A and A/b amps make a lot of heat as they are not terribly efficient.
The best of all worlds is to have a good class D amp section coupled with a very nice Linear Power supply, large toroid transformer and a lot of capacitance for reserve head room. If you ask the manufacturers of the subs what type of power supplies they use, most will tell you that they have a switching type supply which has little headroom and therefore runs out of fuel fast.

My apologies, The Velodyne User Interface Manual is no longer coupled with the link I provided.  
https://www.velodyneacoustics.com/pdf/digitaldriveplus/DD+UserInterfaceManual.pdf

@slimpikins

I know what you are saying. The class D is a switching amp, just like a wall wart. I don’t like the sound. SS amps typically sound similar to me.

Series T/i uses the same Class A/B power amplifier sections with large, high current power supplies, precision-wound toroidal transformers and an amazing reliability record that has powered almost 100,000 RELs.

In this case I take exception. The RELs are beyond your expectations. That is why I chose it over the Class D JL.

If you look at the way a Class D operates is chops the signal up similar to digitizing it. Yes they can make them sound pretty good with lots of power, but it don't sound as good to me.

Thank you and have a nice day.

plenty good discussion and advice here

i will add my 2 cents

pair of rel's ... done... :)

   

  If you look at the way a Class D operates is chops the signal up similar to digitizing it. Yes they can make them sound pretty good with lots of power, but it don't sound as good to me.

Was your assessment of both subwoofers compared in the relitivly same position during the same A/B listening session?

Just as an opposing point of view, I'd like to say that I have done a fair amount of comparison evaluation of Class A/Ab and Class D amps.
The switching power supplies are another story all together as I feel they don't cut it with powerful subwoofers.  The heavy toroidal type transformers with a lot of reserve capacitance just has the massive headroom for large dynamic power demands.   Take a look at the Bryston 28B3 monoblock amps (Google image these monsters and you cannot believe the power supply section), They are pumping out around 1800 watts into 4 ohms with what I am told is almost unimaginable dynamic power when under heavy loading.  I have not had the luxury to try these out yet, but I'd love to.
I have a nice Parasound A51 amp which is Class A operation up to around 10 watts output and then migrates into a Class Ab amp when the power goes up as it can do 400 watts per channel into 4 ohms.  It's a great amp, very smooth and musical.  I was sent one of their new design Class D amps to try out and I must say that on the lower end, it was impressive with its 600 watts per channel and gut wrenching bass response.  I did not like it much on the upper mids into upper range as I found it harsh on my ears after a period of time listening.  But it is not an expensive amp and it uses the typical off the shelf Class D power modules which many companies elect to go with.
From there I installed a pair of Anthem Statement M1 monoblock amps which are gorgeous Class D slim pancakes vs. the A51 Parasound A/Ab amp.  The M1's are connected to my main panel via dedicated 240V 15 amp circuits, one for each amp.... and running them on 240V vs. 120 V 20 amp lines made a huge difference in performance.  At  4 ohms, these babies pump at a minimum of 2000 watts per channel and all I can say is that it was a major WOW moment when I turned them on with some music I am very familiar with.  Massive low end, super silky mids and smooth/articulate Upper range.   It was almost too good to be true and I wanted to hear how they were on me after a night of long listening.... just fabulous, absolutely no harshness at all.  These amps have liquid cooled output devices and very proprietary feedback loop design along with an excellent power supply section.  There are no off the shelf Class D modules in the M1's they are all Anthem of Canada design and built in Toronto and expensive at $7K.

Now after a few days of use, I decided to swap out to my trusty Parasound Halo A51 A/Ab amp just to get back into Class A again.  After about 1 hour of use, I removed it from the rack and went back to the heavenly M1 monos.... no contest!   The Class A amp was just blah and lacking in articulation vs. the M1's in Class D.  The M1's are still here, I didn't use the A51 for about a year or so until I decided to use it for a surround system where it is doing duty as the center/surround/rear speakers which it does well for.  But for critical listening on two channel stereo vinyl with my VPI Ares3/SME Series IV tonearm/Ortofon A90 MC, not much will come close to the M1's.   Again I have not had the luxury to try the monster Bryston's, but at $30K for a pair of those monoblocks, I might be waiting.

Getting back to Northman and his original quest for information;  I still think that you should get yourself the Axiom EP500V4 subs at $1500 each in real wood veneer and with the new variable phasing.  A pair of these I believe will outperform most anything you will find under $2500 each.  Plus if you are not happy, they give you a 30 day trial, no questions asked for return; so you cannot hurt yourself.  I think they even pay the return freight.... that's because hardly anyone ever returns their stuff. :)
If I were in your shoes, I'd get a pair of the ones you are interested in and the EP500's and do an in home comparison to make up your mind on suits you best.

@slimpickins5  I don't doubt that there are some very expensive Class D amps that will sound great. They are way out of my budget, mostly for the 5% who make too much money. There are some modestly priced units that sell within my budget, but until recently they weren't very good.

The PS audio product reviewed in Stereophile December 2020 issue are probably good sounding. Especially in the bottom.

They are still PCM or PWM. Pulse Code Modulation or Pulse Width Modulation are sampling techniques that quantify analogue into pulses or bits. Bits are bits. Bits are digital.You can turn a square wave (bits) into a sine wave with filters, the same basic technique used in Class D or PWM amps. I prefer the purity of an analogue signal from start to finish, vinyl to speaker cone.
Also, they use chips to do the work. That's solid state. I choose analogue and tubes.

Well I don't think that you can compare modulation states as bits 1 and 0.  
They are not computer code.  So I don't see the comparison.  Its just a difference in when the solid state device is firing or operational as in using current and making heat.  It is how the analog signal is amplified.  Analog in, analog out.  My vinyl goes in in pure analog state and comes out the same way.   Trust me, it just sounds much more articulate, defined and full with high dynamic range vs. my Class A amp.  Its much better in my opinion.   And I am not degrading the devices with excessive heat or worse yet degrading tubes which really don't do well with heat and other degradation with age, loss of vacuum, etc.   I think that Widows 10 is far better than Windows 95. 

Tubeculin,  I don't know what you consider 5% breadwinner prices for gear is, perhaps a Bryston 28B3 pair of monos?   $30K...?   But if $7K is in your budget, you should play with a pair of the Anthem M1 monoblocks.    I think that is the bargain of the new century.   Very affordable for high end, well designed gear and if you can find a used pair like I did, even better (but good luck finding any, they almost never come up for sale).   And if you were not pleased with them after finding them at a good used price, you'd be able to resell and get all of your money back, maybe more.

Slim, Yeah, I’m not able to pay new car prices for amps. My whole system was the cost of a decent sedan, lock, stock and barrel. I’m more budget/value based. These are in my range. But, I’m not in the equipment revolving door game. It took a few iterations to get where I am and I’m staying. I’m in this for the music, not the joy of playing with new toys every few months.

However, Stereophile was not terribly complementary of the M1s they tested (two sets) although their measurements confirmed the marketing hype. Anthem uses PWM.

The bottom line was that the reviewer would not recommend them, yet. The reviewer did expect the flaws found would be corrected with further voicing perhaps over time. Also, I notice there are a lot of digital components in the circuit (not signal path) that have the potential to add digital noise. I think in a home theater setting they would do well (these amps are out of my price range for TV audio as well). And, they use a PCB not P2P wiring. So overall I probably wouldn’t audition them if I were into an equipment change.

I hope that you continue to enjoy yours. I’m glad they sound so good to you.

FYI: How a Class D "Digital" Amplifier Works

https://www.audioholics.com/audio-amplifier/class-d-digital-amplifier

Tuberculin,
This might be a better read to explain Class D vs. Class A or A/b
https://en.wikipedia.org/wiki/Class-D_amplifier

You can read how Class D is not a ’digital’ amplifier. It’s simply a full on or full off output device vs. a full on all the time device. Theoretically it can achieve 100 percent efficiency, but with the available devices it is not that high obviously, more like 90 plus percent. Class A amps have a theoretical efficiency top of 50% and as the article states often they don’t even hit 20%. But Class A amps make for fabulous winter time axillary home heaters or summer time A/C test appliances. Class D amplifiers using sophisticated feedback design and equally sophisticated power supply design not only deliver incredibly high output power with very little losses going into heat, but they move any distortion (by design) out of audible ranges. This is why a nicely designed Class D audio amp can be so incredibly smooth, powerful and not very warm to the touch with amazingly low power consumption in the idle mode. I think that my 2000 watt per channel M1’s draw only 3 watts in standby and 13 watts when in full on operation at idle.
I tried to get a copy of the schematic of the M1 from Anthem as a buddy of mine who is an excellent ex-Bell Labs electrical design engineer wanted to study what they employed. Anthem told me that they do not supply technical design data on this amp to anyone as it is extremely proprietary. The guy at Anthem told me that they invested over $5 Million dollars in the R/D engineering of the circuits and they don’t wish to share it with any competitors. I suppose I fully understand this. B&O on the other hand developed their Class D ICE modules for general distribution to manufacturers who wanted a quick and easy way to build Class D amps at very reasonable cost. This is why most amps in Class D on the market are using ICE power modules and why they are great for Sub woofers where high frequency harshness is not an issue, but powerful low distortion Bass frequencies work well.
I did have the opportunity to test and evaluate the Parasound Zonemaster Class D amp. They sent me one to try against the A51 and the M1’s. The Zonemaster is a very nice compact, 600 watt per channel amp. It actually plays very well, but for my ears, it had that well known high frequency harshness due to the inexpensive ICE modules. But it only costs $1200 dollars for a 2 channel 600 watt per channel amp! I told the guys at Parasound that as much as I enjoyed playing with the amp, it was not in my opinion well suited for a very high end audio system with high resolution speakers. I said it was absolutely perfect as an entry level amp for people just getting started and on a budget, or for college kids who want a lot of power in their dorm rooms and who have to move around often as its so light and compact/easy to move; or as an amp in a home theater requiring more channels to drive surrounds or rear speakers.  People using lower cost speakers which are not going to be extremely resolving in the upper frequencies might not even hear any harshness. They got a laugh out of that and said I had actually hit it right on the mark in terms of who their intended market was; so they were very pleased that I was in agreement. They never expected it to be competitive against the likes of the M1’s. But the Zonemaster blew away the A51 Halo in lower end, lower/mid grunt, that thing has some balls. It just was not as smooth in the upper mids/upper range as the A51. A $1200 Zonemaster vs. the $5000 A51 did pretty decently overall though. If I was back in college in my dorm room which was set up like a party/disco club, I would have been the place to be hanging out had I owned the Zonemaster back then vs. my old tube amp. But then again the speakers probably would not have made it through a weekend.

When it comes to high end amps, I think from what I am told the Bryston 28B3 monoblocks at $30K are about as good as it gets. I chatted at length with Ian at Axiom about the 28B3’s vs. the M1’s. He has heard both quite a bit and he told me that they are both top of the line, but he likes the massive reserve power of the 28B3’s and those are his go to amps. I of course pointed out that he is talking in terms of money being no object and he agreed. I asked if he was doing a value comparison, that is the $30K 28B3’s vs. the $7K M1’s, what would he do.... he said the M1’s would always be his normal second choice, but when I put it that way, he’d definitely go with M1’s; they are very close in performance. So there you have it; a well designed Class D amp pair against the some of the best in linear high dollar monoblocks is right in the running. And I am not heating the house with it or paying large utility bills.

As far as a sub amp goes (or run up to ~1kHz) the Class D-based Crown K2 is as good as any I've heard. When bridged it's supposedly a fine all-round amp not restricted to subs/lower to central midrange prowess only. 

As great stand-alone all-round amps costing less than a fortune the Crown Studio Reference I/II (now discontinued) and MC² Audio S800/1400 are highly recommended. Money placed where it matters. 

Slim, I read the Wikipedia thing long ago. I have been familiarizing myself with the digital amps for a long time. I wanted to see what all the hype was about. I have a degree in electronics and spent most of my career in digital. No, I'm not an amp designer, but I understood Class A and A/B over half a century ago.You can't convince me bits ain't bits. Nothing you say can sway me. You're talking spending new car money for amps. Sorry, even the cheap ones are off the table. Not class A or A/B.

I really don't care about efficiency, heat or any of the "benefits" of Class D. Full on and full off is bits. Bits are bits. Bits are digital. Plus they have switching power supplies as well. Enjoy your Class D's and spend another 50K to 100K on equipment. If you got it  spend it.
Peace, out.

Ah, but there is where you are wrong, the good ones do not have switching power supplies, that was precisely my entire point.   And the operational state of a solid state device is not a computer bit.  But that's OK, I really like the Class D and others should try them too.

Here's some of my thoughts on rooms and subs.

Right now, I'm figuring out the best location for my system in my room. It's about time. My room is 14.5' x 19.5' x 8' high. I listen across the 14.5" dimension out of necessity. I am using a readily available Room Analyzer package. This hardware/sofware generates audio sweeps, records the sound pressure with a mic, and calculates freq response, reverberation time, room modes, phasing and delay times. I am using a DIY sub. It has a 10" Scanspeak woofer in an acoustic suspension design. The main speakers are B&W 805s on the stands provided by B&W.

With the listening position against the wall opposite the speakers and the sub to the left of the left speaker, I've found several frequencies (40, 62, 125, 175 Hz and others) where there is a peak or null with a long delay time, much longer than other frequencies. Hand calculation of the expected room modes fits this observation. At 40 Hz, the sound wavelength is about 28'. Half wave is 14', which is nearly exactly the length I'm listening across. So room modes are important for an average sized room. The 40Hz peak is +10dB (above mean). the others have similar decay times but are not as strong, although the dip at 63Hz is nearly -10dB.
I moved my listening position (sofa) out  into the room away from the wall. I placed it 1/3 of the length of the room (recommended). New measurements are now quite different. All modes are suppressed to different degrees, but are still there. The software cannot find any modes, although I do have irregularities in freq response.
Listening position is a major factor in suppressing room modes. The explanation is that the new listening position is near a null in the 40Hz room mode. The conclusion is that room modes are important for bass. If you want good sounding bass from 30Hz upward, room modes must be considered.
Now, imagine I were to use the DARO system in my previous listening location. The DARO would call for 10dB suppression at 40Hz, but also for a approx +10dB increase in SPL at 63 Hz. This means that DARO would be calling for 100x more power from the sub amp (see https://geoffthegreygeek.com/amplifier-power/). This is very difficult to do for most amps. The DARO can reduce peaks, but cannot be used effectively to remove dips.

In order to effectively suppress modes, several things are needed prior to using DSP.
.First, get the sub away from the walls and corners. Get it (them) out into the room (unless you want your bass to overpower everything else).

Second, use the recommended listening position.
Third, after the first two are done and characterized, add room treatments that includes corner traps and bass traps for the low frequencies. These absorb the appropriate frequency bands so the standing waves are absorbed, not reflected. Additionally, the long reverberation will be dramatically reduced.
The first two modifications will get you a long way, but room treatment is absolutely needed to suppress the remaining modes, unless you are fortunate or the modes are sufficiently suppressed for your taste.

After the above three things are done, then the DSP (such as DARO) can be used as the peaks and nulls will be of lower amplitude and therefore the amp will not be stressed as severely.
In conclusion, room modes determine the lower frequency response of an audio system. The exact modes depend on the room size and geometry. Room modes cannot be corrected entirely with DSP software, especially nulls (dips). 
The modes are there whether DSP is used or not. Optimal location of the sub(s) and the listening position is vitally important. To avoid excessive use of amplifier power, add room treatments prior to adding DSP.
Please note that there are other considerations if two or more subs are used as they can be placed such that certain room modes can be suppressed. But room modes are still present since these are characteristics of the room only . One person's solution may not work for someone else. Other modes may not be.suppressed. Room modes are always present in a room since these are characteristics of the room only . It doesn't matter what is in the room, the modes still exist. Any item added to the room can only affect the relative amplitudes of the room modes (this goes for treatments also). One person's solution may not work well for someone else.

Even without a room analyzer, one can improve the performance of an audio system. Searches will provide guidelines, such as placing the listening position about 1/3 (actually 0.38) of the distance between the walls behind the speakers and the listener..

Some boilerplate - I am not affiliated with any manufacturer of audio equipment, room treatments or DSP. I have no interest in selling you anything.  I have an MS in Physics and over two decades designing and building optical systems (telescopes for example). Wave phenomena are very familiar to me.
Constructive criticism is always welcomed.

My apologies to everyone. I meant this screed for another topic on this forum. Perhaps it will add to the discussion. If not, feel free to erase it. I'm very new.