Why do you guys pursue a flat frequency response when you buy a subwoofer?

Why do you guys pursue a flat frequency response when you buy a subwoofer?

Because it’s the base line with what you can judge other subs by, if they all conform to it, then being compared in the same room you can draw a conclusion.
If you didn’t have this base line of flat in an anechoic chamber they there’d be no use to a/ any of them as they would all sound very different.

Cheers George

Hi OP,
I am not sure you are in the right place to throw these aspersions. In all of my reading of how A’goners are using and misusing subwoofers I can’t recall a single instance when one asked for a flat subwoofer.

Every post about purchasing a sub here that I can recall (and my memory is not photographic) was about the most musical, followed by the deepest response.

Posts about fixing subwoofer issues certainly involves a lot of discussion about room acoustics and EQ. My thoughts on buying or not buying a subwoofer at all are here:

https://speakermakersjourney.blogspot.com/2020/04/how-to-not-buy-subwoofer.html

I argue that the most important thing to know before buying a sub is how you are going to integrated it well into your system and the room. That's where so much goes wrong.

Best,E

Deep_333 wrote:  "Why do you guys pursue a flat response when you buy a subwoofer?... The minute you put that flat sub in your room and take some measurements, it is anything but flat (it's a rollercoaster with all kinds of peaks/nulls etc, EQ to the rescue)..." 

Deep, I come at this situation from the other side of the fence; I make subwoofers. 

At the risk of overgeneralizing, I see the room as typically doing two things to the response of a subwoofer: 

First, the usually room imparts a gently rising trend to the subwoofer's output as we go down in frequency.  This is because as we go lower and lower in frequency, the room's surfaces become closer and closer to the sub in terms of wavelengths.  So we get progressively more and more approximately in-phase reinforcement from the room surfaces as we go down in frequency.  This trend has been called "room gain" (which may or may not be technically correct), and 3 dB per octave below about 80 Hz is an approximation which has been suggested by a couple of different researchers (Martin Colloms and a woofer designer whose name slips my mind at the moment)... the exact figure of course depending on the room's acoustics as well as the subwoofer and listener locations within the room. 

The second thing that happens is, room interaction imposes that roller-coaster peak-and-dip pattern you mentioned.  The specifics of how the subwoofer's output is altered by the room once again depend on the room's acoustics, as well as the subwoofer and listener locations within the room. 

Imo the first issue can be addressed by designing the subwoofer to have a native frequency response which slopes gently downwards by the approximate inverse of "typical" room gain, or 3 about dB per octave.  I'm not saying this is the only way of addressing this issue, but imo it results in a reasonably good starting point. 

The second issue (rollercoaster in-room response) presents an interesting challenge.  Opinions vary on how to address it. 

I think "flat frequency response" is a reasonable target for a subwoofer system, as long as we're talking about the ACTUAL IN-ROOM response.  I do not think a "flat" frequency response which ignores the room's effects is the ideal starting point. 

Duke

Why do you ask?

Why buy a sub from a manufacturer who can't even get a flat frequency response when so many can?  Of course there are room issues that need attention but you might as well start with a good fundamental frequency response.  

The minute you put that flat sub in your room and take some measurements, it is anything but flat (it's a rollercoaster with all kinds of peaks/nulls etc, EQ to the rescue).....So, why do you dudes continue to look for the flat line?

Good question. This dude used to think like that, until he started reading the other guy, aka Duke, aka Audiokinesis, and that guy led the dude to reading some other guys, none of whom think like most dudes but instead actually studied the problem. All this reading led to actually for the first time understanding the problem, which yes most dudes do get wrong but this guy now does not.

What the real sub guys know that the dudes do not is what Duke alludes to above as "an interesting challenge".

You are right deep, put one sub in a room and you get peaks and valleys all over the place. Move the sub, peaks and valleys move but are all still there. You move the one sub around endlessly. Been there. Done that.

So, to review, one sub no matter where you put it produces lumpy bass. Moving the sub only moves the lumps, but never gets rid of them. The solution, which you can only shake your head at the brilliant simplicity of it all, is more subs.

With more subs each sub has to put out much less volume. So the lumps get smaller- and there are more of them. Which when you get enough small lumps turns out the result is pretty smooth. This brilliant idea of using lots of bass sources distributed around the room is called a distributed bass array or DBA.

Duke the speaker guy makes em. He calls his version the Swarm. Mine is based on his. https://systems.audiogon.com/systems/8367  Notice there's three different types of subs- 2 ported, 2 sealed, 1 isobaric. There's other guys here with DIY DBA, and other guys using the Swarm. The one thing all us guys have in common is we love our smooth, articulate, deep and totally awesome bass.

That and, we wish more guys knew about it, and we could all be less like the other dudes.

" Imo the first issue can be addressed by designing the subwoofer to have a native frequency response which slopes gently downwards by the approximate inverse of "typical" room gain, or 3 about dB per octave. I'm not saying this is the only way of addressing this issue, but imo it results in a reasonably good starting point.

The second issue (rollercoaster in-room response) presents an interesting challenge. Opinions vary on how to address it."

Duke, 
Can you name the popular opinions among sub manufacturers on how they think it should be addressed? Of course, more subs a.k.a an array of 4, 8 or 16 is great for business. But, are there other opinions out there?

I currently have Rythmiks (room1) and HSUs (room2) at home and a BIC PL 200 II in my shop. The BIC is not flat and i saw some clowns arguing in a forum that the BIC is very very bad because of the peak in its spec! However, this budget BIC actually sounds pretty freaking good to me and i use it largely for music in my shop. As far as the manufacturers coming up with a flat response (Rythmiks, HSUs, SVS, etc), Is it just a "statement" that they are competent enough to come up with a flat response? (though it means jack sht after it goes in the room) 

A careful look at the dimensions of your various rooms may tell you quite a bit about why the shop sounds so good.

obviously Danny at Rhythmic , Duke at AudioKenisis, and others know what they are doing relative to room nodes, room gain, and designing for flat response, some w adjustable phase. My favorite designer is Vandersteen’s with 11 bands of EQ below 120 HZ, variable count our, EQ centers on common room nodes. Contrary to Miller’s myth, many sub designers are very aware of Earl Geddes seminal work on multiple subs to cancel out constructive and destructive interference ( Duke you really should look at the wave photo I emailed you long ago ), I will post it in my virtual system page... perfect example of constructive/destructive interference), Many ( but thankful not all ) customers don’t want a forest of subwoofers in the room. RV power factor corrects his supplied amp which also has feed forward control - others use servos, etc. point is there are some fantastic subs out there.
one way to quickly judge sub integration with mains and response and pitch definition is by listening to well recorded scaling acoustic bass - Ray Brown Soular energy is fantastic for this :-)
enjoy your BIC and other subs OP, enjoy the music !!!!

I think most people use multiple subwoofers when possible and PEQ regardless of the number of subwoofers used, in order to flatten out the actual in-room frequency response. Sometimes with a slight curve providing bass emphasis as a personal preference.

Contrary to Miller’s myth many sub designers are very aware of Earl Geddes seminal work on multiple subs

What myth? Hello! Tomic601! What myth??? Where did I ever say many sub designers are not aware? There’s a function, cut and paste. Please use it to substantiate your insult or withdraw it. Thank you!

OP you have three subs. Thus this thing is a whole lot easier for you than most. Simply put all three in one room and find out for yourself what happens.

tomic601 not letting you off the hook. I know perfectly well the last thing I ever do is promulgate a myth. Serious insult buddy. Prove it, or apologize, or be forever branded a liar. I think we all know which one it is, but I’m giving you the opportunity to pretend you read me wrong.

@tomic601 , I agree on the forest of subwoofers issue in the house.... If the number rises above 2 in a room, i fear my wife will take a flamethrower to all of them. But, yeah i love Danny and his contributions. My dual Rythmiks are the model with Danny’s driver.

At this point, i’m thinking if
a) DIY might be the route to take....This requires the user to do a lot of research, is competent and has the time to take the DIY route.
or
b) If guys like Danny from GR research may tailor something for ya if you gave him a comprehensive set of measurements for the specific room with your subs.... But, i guess it may be impractical considering how busy guys like Danny are. It may be nice if some manufacturers could explore this business model.

This got me thinking to my times in motion picture sound and looking at big sub cabinets and drivers by JBL and others.

A sub at home typically only covers 2 octaves, 20-80 Hz. It is actually very difficult to produce a speaker which is anechoically flat through 2 octaves with steep roll off after.

Most subs I’ve ever seen have a natural response which is rather hump-shaped. It is the integration with the speaker and the room which provides the smooth and expansive bass people are looking for.

Miller - who made you King with a branding iron ? You think there are dudes who know and those who don’t. Nowhere do you differentiate between users and designers. If you paint with a broad brush “ dude’s” you have people like me who fill in the details. I am guessing you have yet to actually hear a Danny R or Richard Vandersteen sub ... as I recall your last post about DR’s product utube video focused on the drape of curtains...
so... flail away Charlie

For the OP I am sure a conversation with Danny would go well. A floor stander with built in subs ( better w high pass amp for mid bass and up ) and dedicated sub amp, AND your two rhythmic subs = 4 which with carefully placing them gets you to Swarm. The Vandersteen way is all analog, if you prefer DSP there are other roads.
of course factually knowing what your room is doing is important- vandertones is a free download of warbletone test frequencies common to typical room nodes, that and a relatively inexpensive RS analog SPL meter and you will understand what is happening. In normal non COVID-19 times I would loan you the meter - I have three - all stuck in Seattle- finally what are the dimensions of workshop, I can run need/modes calculator...
have fun, enjoy the music
jim

Deep_333 wrote, " Duke, Can you name the popular opinions among sub manufacturers on how they think it should be addressed? Of course, more subs a.k.a an array of 4, 8 or 16 is great for business. But, are there other opinions out there?"

Setting the controls on the subwoofer amp correctly matters a lot. If you’re doing it by ear, first set the level, then the frequency, then the phase. Then cycle back through again a few times. This order is progressing from "makes the most difference" to "makes the least difference."

(Setting the level correctly is particularly time-consuming. Equal loudness curves indicate that a 2 dB difference at 40 Hz is subjectively comparable to a 4 dB difference at 1 kHz, so precision in setting the level really is called for. This also explains why smoothing the bass response pays unexpectedly large subjective dividends, as the ear is arguably doubly sensitive to peaks in the bass region.)

Careful positioning of the subwoofer and/or listening location is beneficial. One particularly effective technique is the "subwoofer crawl". Put your subwoofer in the listening chair and crawl around the room until you find the location where the bass sounds the best. Place your subwoofer there.

Bass trapping or other methods of low-frequency damping improves the bass smoothness everywhere in the room by reducing the magnitude of peaks and dips.

EQ on its own is most suited to smoothing the bass in a small listening area. This is because that roller-coaster pattern you mentioned typically changes significantly for different listening locations around the room. Of course bass trapping and EQ can be combined with other techniques.

A distributed multi-sub system, or distributed bass array, smooths the bass throughout the room by reducing the magnitude of peaks and dips.

A planar bass array consists of a rectangular array of four subwoofers on or in the front wall, with a similar array on or in the rear wall. The symmetrical rectangular configuration minimizes reflections in the horizontal and vertical directions. The subs in the rear wall are delayed such that they cancel the output of the front subs when it arrives at the rear wall, so there is theoretically no reflection in the front-to-back direction. I have no actual experience with this approach.

"Of course, more subs a.k.a an array of 4, 8 or 16 is great for business."

I’d probably make a lot more money selling a single big sub for the same price, as the labor cost to build four small subs is roughly four times the labor cost to build one big sub. I went with four small subs (credit to Earl Geddes) after spending many years trying to develop a single subwoofer "fast enough" to keep up with Maggies and Quads. The solution was to focus on room interaction, because (imo) that’s the biggest problem.

" As far as the manufacturers coming up with a flat response (Rythmiks, HSUs, SVS, etc), Is it just a "statement" that they are competent enough to come up with a flat response? "

I am sure those designers and others have worked just as hard at solving the problems they believe matter most as I have. And they are probably better at hitting their target(s) than I am at hitting mine: You mentioned 4, 8, or 16 subs, and my 4-sub system would be outperformed by 8 or 16 sub systems.

Regarding the "forest of subwoofers" issue, often at audio shows nobody even notices the four small subs sprinkled around the room until they are pointed out. In many cases as the number of subs goes up the size of each sub can correspondingly go down, and in some rooms it is practical to place small subs atop bookcases or on shelves.

Tomic601 wrote: "Duke you really should look at the wave photo I emailed you long ago"

I vaguely recall it, but couldn’t find it when I looked again just now.

Duke

tomic601:

Miller - flail away Charlie

So you choose liar. If the shoe fits, wear it.
Just remember it was you who tied the laces.

Gr8 post Duke ! The only thing I would add is Management of the critical crossover frequency to the mains and the slope and energy of the subs above 100 HZ, assuming the dude , “ any major dude “ cares about imaging....

Duke - I will resend you the hi-rez photo at your AK business email. I put a medium
rez in my virtual system page : Poverty Bay Sound. That is viewable by all.

" Duke - I will resend you the hi-rez photo at your AK business email." 

Got it - THANK YOU!  Very interesting pattern of waves on the lake!! 

How were the patterns moving? 

Duke

Millercarbon to tomic601: " So you choose liar. "

Miller, just for the record, I’m not comfortable with what you did there.

In a now-deleted post you called for tomic to do such-and-such or else he was (in your words) a liar, and when he didn’t, you now say he chooses to be a liar. Without overly dissecting it, I’ll just say that seems pretty aggressive to me.

Miller, is there a different way you could have replied to tomic601’s earlier post, one that extended the benefit of the doubt and would therefore likely have resulted in the clearing up any misperceptions?

Duke

Duke - waves ( actually a powerful wake ) with decent amplitude and low frequency bounced at almost a perfect 90 off bulkhead.... the holes and flat truncated peaks illustrate in a “ simple physical situation what is more complex in a room. The classic two slit model without the on the side amplitude translator.

And in the spirit of good will Duke, because you are indeed a gentleman- I would change “ myth “ to vague assertion.

best to you in these crazy times....

There's always a different way to reply. Could be he was so enamored with the alliteration and proud of coming up with Miller's myth he just had to use it even though it had nothing to do with anything I'd said. Could have asked about that a lot of different ways. I'm not comfortable having people, since you don't like lie let's say make things up about me. That's a misperception he had the opportunity to correct, and he chose to double down on the insults. Not exactly comfortable with that either. Mainly though I'm far from thinking it had anything to do with misperception. I think he perceived what I said just fine. But rather than dealing with the substance of what I actually said he thought it better to belittle it as myth. That's my perception. If its wrong, he's free to clear it up. I'm certainly open to that.

Ahh... Well there was nothing vague. And the assertion was never made. But "in the spirit of goodwill" it'll do.

@tomic601 , @audiokinesis @erik_squires

A lot of stuff you guys mention are steps i’ve already gone through over the ages. Both my rooms are treated with bass traps, absorption (ceiling, FR) and diffusion panels.
Room 1 has 5.2 Elac Adante speakers and HSU subs powered by a Yamaha RX-A3080 (active bass management and all the frills on this Yamaha’s flagship made it easier for me) Preouts go to a Jungson 80W/ch class A chifi amp. I’ve gone the full 9 yards with REW, subcrawls, positioning, treatments and EQ to get fairly flat curves. I have a 2nd pair of Tekton Moab speakers as a standalone 2.0 system with the Jungson amp in this room (No subs, so it leaves the discussion). I listen to music 95% in either 4.2 or 5.2 and movies 5% in this setup. It works really well for me when i’m listening to surround mixes, movie/game composers (a genre i really like with orchestral elements tied to electronica), electronica, house, trance, etc

Room2 was a nightmare that lasted months of tinkering. It is a 2.2 music setup with no bass management. 2 Yamaha Ns-F901s and Rythmik subs powered by a Yamaha A-S2100 integrated amp and Denafrips venus DAC. I use this room for several other genres of music. It took me a while to get these subs "blended in" as best as i could. I did the phase matching with the sub’s continuous phase adjustment feature with knowledge of both the sub and the speaker’s phase response (i measured it) at the crossover point. I crawled all over the place and the subs had to be located in a non-aesthetically pleasing position to sound right. I listen to many different genres of music a.k.a i’m not listening to 1 track over and over. They are not all recorded the same. If a recording’s off from a band i like, i am back to tweak OCD again.

My perception is that subs are made to cater mainly to the Hometheater market (set the crossover on the receiver and the movie explosions go boom boom boom all day long!! easy as pie!). But, it seems to be much harder if you’re a music aficionado. My perception is that these manufacturers leave dudes who are music aficionados out in the cold. A competent speaker designer like..say Andrew Jones, for instance, has so many variables available to him when he’s designing drivers, cabinet, crossovers, blending them, etc. He comes out with a wholesome design in the end.

Now, when subs are being integrated with these speakers, the sub appears to be an afterthought. A end user like myself who’s not a speaker designer or professional audio engineer, is somehow being asked by sub manufacturers to make it all work together/figure it out somehow. They release a flat curve to make themselves look good and sell a product. At the end, its a customer like myself who has to go to enormous lengths and months of tinkering and treatment to make it all work right. I may have very few variables to work with actually (than what a speaker designer may have available when he’s designing something from the ground up). Let’s see, a sub volume control and a crossover if my amp doesn’t have bass management, that’s it. To my knowledge, only Rythmik even offers a phase control that’s more than just a 0-180 flip switch. The rest is...crawl around, throw a bass trap, etc and make it work somehow...

Is my perception right or wrong gentlemen?

I don't. It may be easier to start with a speaker that is reasonably flat but a speaker that is flat will sound bright and bass shy under most circumstances. Most people have no idea what their system is doing and their opinion is based on assumptions that are usually dead wrong.
My system is measured and graphed on a computer. Filters are generated that make the systems performance perfectly flat as a starting point. Then response curves of my design are overlaid to make the system do what I want. The basic curve is boosted 6 dB at 20 Hz and down 12 dB at 20 kHz. On top of this there is dynamic loudness compensation which follows the Fletcher Munson curves based on volume. This assures that the tonal balance I like in my room is the same regardless of volume. After this is the subwoofer crossover which I can modify on the fly if I desire. 
The problem is that the right tonal balance changes with volume. In a standard set up each record or file has a "right" volume. A record that was mastered for high volume will sound dull and bassless at low levels prompting the listener to think it was a bad recording. Records that were mastered for lower volumes will be shrill at higher volumes making all the women in the room extremely angry. Tone controls help a little. But they and standard loudness compensation are just not l flexible enough on top of the fact that the listener really has no idea what is going on. When you see what your system is doing on the computer and integrate that to what you are hearing you learn pretty quick what making specific changes will do. This is an aid of immeasurable benefit. This alone justifies digital audio to the point where I gladly digitize my phono amp so it can play on the same ball field. 
I have measured several systems. The reason Wilson's are so... comfortable is that they are engineered with a notch at about 3 kHz which takes the sting out of female voices and violins. I suspect other companies do this as well.     

Deep_333 wrote: " Now, when subs are being integrated with these speakers, the sub appears to be an afterthought. An end user like myself who’s not a speaker designer or professional audio engineer, is somehow being asked by sub manufacturers to make it all work together somehow."

Given that there is an enormous variation in what kind of main speakers a subwoofer may be paired with, not to mention the enormous variation in room acoustic situations, a one-size-fits-all, plug-n-play solution is not possible. Even if the subwoofer(s) and mains have been designed as a package, low-frequency room acoustics still varies enough that some adjustments may be required during set-up.

You might consider working with the dealer or manufacturer who sold your main speakers, or maybe buy your subs through a dealer who is willing to do the setup.

Deep_333 wrote: "They release a flat curve to make themselves look good and sell a product."

Imo whether or not a flat curve earns a person’s business is their choice. I assume that subwoofer manufacturers who went to the trouble to achieve a flat curve sincerely believe in its merit.

"At the end, its a customer like myself who has to go to enormous lengths and months of tinkering and treatment to make it all work right."

To me, this statement implies that there may be room for improvement over whatever it was you tried.

"I may have very few variables to work with actually... Let’s see, a sub volume control and a crossover if my amp doesn’t have bass management, that’s it. To my knowledge, only Rythmik even offers a phase control that’s more than just a 0-180 flip switch. The rest is...crawl around, throw a bass trap, etc and make it work somehow."

Some subwoofer systems offer more degrees of freedom than others. For the record, Rythmik is not the only one who offers a phase control which is more than just a 0-180 flip switch. (Also just for the record, while I mentioned the crawl and bass traps in a previous post, neither are tools which I rely on.)

"Is my perception right or wrong gentlemen?"

It sounds to me like you are disappointed in your experience with subwoofers, and hold subwoofer manufacturers accountable. Is that correct? If not, can you clarify?

Duke

Is my perception right or wrong gentlemen?

I think you are more or less right, though I come at it differently in my blog post. You almost tie it all together like I have and state that a subwoofer is like another driver in a speaker system, and that to integrate it well to the speaker is as complicated as making a multi-way speaker system.

And this is why my usual advice is to think about exactly what steps you'll need to get to "done."  The easiest answers are preamps and processors with automatic subwoofer configuration, usually a component of room correction, along with appropriate room treatment.

I do believe that the difficulty in integrating a subwoofer is usually under-sold.

You are also perceptive about how big the gap is between home theater and 2 channel in this regard. While 2 channel systems vary greatly, THX specified waaaaay back in the early days of Dolby Pro-Logic, sealed, 80 Hz cabinets for small satellites specifically to address part of this problem. 

Subwoofers are marvelous, glorious tools, but getting to done for the average music lover is just a lot harder than consumers and probably many salespeople realize.  OTOH, let's face it, 90% of those who buy subs aren't actually trained listeners.  They may be perfectly happy with poorly set up subs.  I know I tried to be for a long time with my first M&K V1.

Best,

E

If you wan5 fast responses check out the Svs 3000 or ultra 16 
they have 52 bit processors built in and monitor any variations 
in milliseconds and are superb with split shaft voice coils Great app and a bunch of other things including free shipping 
and 45 day satisfaction or full money back . I hav3 the SB 3000
for $995 or 2 for $1900 delivered. It best my $1700 JL audio sub 
and beat any Rel it is the only great sub with an app the split pole voice coil works only 5he inner part at low volume which is very tunefull, when more power is needed uses the larger outer part 
of the voice coil and goes down to a true 18 HZ.

@audiokinesis , Many hardcore audiophiles i know stick with 2 channel music systems, a.k.a, their high end turntables, DACs, integrated amps/monoblocks, etc with no bass management. These guys try subs and abandon them because they can't get it to integrate right. Many of them buy RELs because it is "supposed to" integrate better (tribal hearsay). But, when they realize that the RELs were hype but lame on delivery, they abandoned them as well.  I sure would not want to add another adc/dac into the chain with a subpar DAC on something like miniDSP for bass management (when i have a Denafrips DAC in my 2 channel setup). Guys i know have waaaay more expensive speakers, DACs, monoblocks, etc on their 2 channel music setups than i do. They are probably not gonna do that either. It's almost like there's a huge disconnect here.

But, of course, once you taste the ecstasy of a well-integrated sub, it's really hard to go back to music without one.  I often find myself listening more in my room1 with active bass management (on my Yam A3080 receiver with the Jungson Class A preouts) than in my 2.2 room2 setup. There may be room for improvement or i may never get there with the tools I have in hand for room2. 

This might be a gross assumption. But, i think some of these 2 channel guys have waaay more cash to throw at a sub manufacturer than the average guy buying a sub for his hometheater. So, It may be a loaded market chunk which is out there i.e., if a manufacturer chooses to tap into it and cater to their systems better (monopoly for sure). More DOFs or.... whatever the R&D/solution may be to better integrate them...you would know better. 

I understand, I still have my original M&K Volkswoofer and Satellites. They still play in my office. I had the Volkswoofer amplifier and driver surrounds renewed last
year. They sound as good as I first remember them and bought in 1983.
I will say though, they don’t shine a light on my primary system.

Deep_333 wrote: "Many hardcore audiophiles i know stick with 2 channel music systems, a.k.a, their high end turntables, DACs, integrated amps/monoblocks, etc with no bass management. These guys try subs and abandon them because they can’t get it to integrate right."

Very interesting. To the best of my knowledge I have yet to have a subwoofer system customer fail to get satisfactory integration with his mains. In most cases they run their mains fullrange and then blend the subs in. Therefore I must give credit to the off-the-shelf Dayton Audio amplifier I use, and to whoever designed it:

https://www.parts-express.com/dayton-audio-sa1000-subwoofer-amplifier-rack-mountable--300-811

Deep: "I sure would not want to add another adc/dac into the chain with a subpar DAC on something like miniDSP for bass management (when i have a Denafrips DAC in my 2 channel setup). Guys i know have waaaay more expensive speakers, DACs, monoblocks, etc on their 2 channel music setups than i do. They are probably not gonna do that either. "

You bring up an excellent point: How do we roll off the bottom end of the mains without any undesirable side effects? Not sure there is a totally transparent solution.

Therefore when I design main speakers with subwoofers in mind, my mains do not need a protective highpass filter unless extremely high SPLs are desired. Their inherent bottom-end rolloffs are intended to blend well with the variable 4th order lowpass filter of that Dayton amp.

Deep: "It may be a loaded market chunk which is out there i.e., if a manufacturer chooses to tap into it and cater to their systems better (monopoly for sure). More DOFs or.... whatever the R&D/solution may be to better integrate them..."

I hadn’t really thought about it in terms of degrees of freedom until this thread. I think there may well be a correlation between (useful) degrees of freedom and good integration with the mains. Lacking the financial resources to develop my own subwoofer amplifier, I count myself lucky Dayton makes an amp with a parametric EQ and a fully adjustable phase control.  My individual passive subs have some adjustability as well.

Duke

Charlie!
 Dude, your gonna make the list now.

Terra Mar? 4-6 foot South Westerly a few years ago. Nice left
Sad loss here yesterday. 

M

For those looking for music subs that aren't like cheaper HT oriented subs, I wonder if the home studio sub category would be a solution.  Sweetwater has a ton of options.

Deep pondering your post... what does REW run result look like for in room ? The frustration in room 2 seems to be more with recording variations? Can you post a frustrating track title and the SPL where troubles begin or end... Also you can high pass the mains with a 6 db per octave filter available from Vandersteen which is part of his systems engineering approach to powered bass integration- not advocating a switch in your speakers. Traveling today,

@m-db  yes that is Terra Mar :-) red tide going.... on top of reopening...

On the subject subs. Too much over thinking I have 4 15 inch woofers in my 4 way speakers total of 60 inches of woof, you can feel your rib cage vibrate at just the right volume problem solved enough said have a nice evening.

I gave this bit of thought on the airplane trip today - IF ya get Soular Energy sounding “ right “
then everything else is recording variability...

OP I sent you a PM offering help gratis but I see you have taken many many steps to better sound...

@audiokinesis --

Deep: "I sure would not want to add another adc/dac into the chain with a subpar DAC on something like miniDSP for bass management (when i have a Denafrips DAC in my 2 channel setup). Guys i know have waaaay more expensive speakers, DACs, monoblocks, etc on their 2 channel music setups than i do. They are probably not gonna do that either. "

You bring up an excellent point: How do we roll off the bottom end of the mains without any undesirable side effects? Not sure there is a totally transparent solution.

Unless your speaker platform is all-active to begin with, in which case (expectedly quality) digital filtering is already a vital part of the configuration - sans passive cross-over parts that would otherwise be regarded the bottleneck. There are pro vendor, excellent digital cross-overs out there that doesn't cost a fortune, like the ones from Xilica, but even with passively configured main speakers - the primary focus in this context, it would seem - I find they're nigh on fully transparent being implemented into the chain. I'm stressing 'nigh on' despite my not being able to detect a sonic degradation with a Xilica unit put into the signal chain that ends with passive speakers (based on my experience with my previous, passive speaker set-up), because I wouldn't want to presume its total transparency in more academic or theoretical terms.

Forest for the trees, as they say; with passive speakers in mind, what does the outcome of putting a quality digital cross-over/DSP into the signal chain potentially bring with it advantageously, high-passing the main speakers instead of letting them run full-range, compared to the (mostly theorized?) audible influence the added component itself will have? That's certainly up to debate, but I find high-passing passive main speakers with a quality digital DSP for subs augmentation to be worthwhile, and with an all-active configuration like I'm using now it's a naturally integrated option. High-passing mains to me is all about relieving them and the amp(s) driving them, rather that protection per se. 

@tomic601 , here are some tracks i use when i'm tinkering with it and listening for things (non compressed FLAC versions of these, 24bit 96khz when possible). Overall SPL levels are relatively high (farmhouse/no neighbors).

Hans Zimmer - Mombasa
https://www.youtube.com/watch?v=CPgPxGX6nNo

Rom Di Prisco - Caverns of  Suursonnabu
https://www.youtube.com/watch?v=EqKyS8WES7Y

Jesper Kyd - Approaching Target 3 
 about 2.35 onwards
https://www.youtube.com/watch?v=NipZFlauZ8E

Yaeji - After that
https://www.youtube.com/watch?v=tAtkZ9iVEwc 

Strappin young lad - love
https://www.youtube.com/watch?v=mL9Aohgd79I

John Peasano - First Contact Protocol
 https://www.youtube.com/watch?v=ZJO6i2b5pH8

Deep thanks I might have the Zimmer on my server, will look this eve. I am out mending fence
i could use a desolate farmhouse!!!

Only able to speak for myself. I have a pair of MC275 in bridged mode, a pair Sonus Faber Olympica Nova V speakers, a pair of SVS PC-4000 subs, and to deal with sonic inequities in the room, a McIntosh MEN220.

The MEN220 requires some set-up where you enter information like the distance between your listening position and the speakers. Then the distance between the subs and you. There are outputs to the speakers and subs, each separate. you set the crossover in the MEN220 & I have no crossover set to the speakers, I do have the subs set to engage at the lowest frequency of the Sonus Fabers.

There are several other parameters to set in the unit. Then you use the provided mic to first measure exactly where your head is going to be when you listen & it runs through an information gathering sequence. Then you place the mic in various places around the room & let it collect that data as it generates complex sounds. It tells you when it’s done. You have it analyze the data and it adjusts the equalization for the room. The remote offers many options depending on the future listening audience including bypass. Once you use the MEN220, you never use the bypass option, the 220 is a magnificent device.

With that, when I’m listening to anything containing 35 Hz down, the subs handle that and there is an objective difference depending of what is being played. Listening to a movie, you feel the explosions, the subaudible crashes so often in the soundtrack thanks to the subs. Part of this is because the 1200 watt subs are vertical and the sound wave hits the wooden floors & the subaudible vibrations are obvious in my chair.

The subs, often play little part in most of the music I listen to, the speakers do a fine job of that, but, the subs do play a part and I’m glad they’re here..

@ka1j   What DAC are you using (DAC output going into the MEN220)?

Have you done a sonic comparison from your DAC output to the MC275 on your 2 main speakers (without subs) to the inclusion of the MEN220 in the chain and listening on the mains only? (without subs)

I use the DAC in the C2600.
Yes, the MEN220 is a new inclusion as is the 2nd MC275. I like to experiment and have tried the different connections, also settling on bi-wiring to the speakers.

The SF are absolutely stellar speakers and with no subwoofers, are beyond impressive. Running directly from the C2600 to 275 to the speakers insults the speakers in this listening room, is not a good choice, it is the room’s sonic problems, not the speakers, but is what it is. I can’t change rooms, I have to deal with what is here.

I wanted to see what the SF sounded like minus the subs and it is like being inside a piano but with an excess "resonance" for lack of a better word because of the room acoustics. Running the speakers alone through the MEN220 cleared up all of that. Adding the subs again, only adds to the lowest of frequencies, many of them subaudible & to the sound for dynamic effect. For example, listen to non synthesized music with just the subs triggering at 35 Hz and down to the 9 Hz these reproduce, you make out no words, can’t follow the music & really, I couldn’t tell what was playing. However, in Attack of the Clones, when the spacecraft is landing, with just the subs only, the house rumbles and the explosion when the ship explodes is like an earthquake, low sound and you feel it completely. Now add the speakers and play it back and you get the full experience. With just the speakers, you do not get the 9 HZ impulse or feel that vibration.

The subs have a purpose, they do not detract from the SF speakers in any way I can tell but they do provide an ultra low frequency dynamic. The MEN220 rounds it all to a beautiful balance that if I had a perfectly set-up listening room, I wouldn’t need it.
Your question asked about subs & I explained why I love mine, but also what helps that to be. I believe the MEN220 ties the ribbon onto balance between speakers and subs. Here’s a good review that explains the MEN220 better than I can.

https://www.tonepublications.com/review/mcintosh-men-220/

A subwoofer?   I am not on the subwoofer bandwagon yet.  I built my own speakers and I am not an audio engineer by any stretch of the imagination.  I am very picky about my sound but never had the money to buy the speaker sound I like.  My 8" towers when compared to klipsch towers where much more smooth, not as harsh in the highs  and gave deep lows.  Low enough I not only feel the punch of a low kick drum but dynamics that get ones attention and make me smile.  A properly designed set of speakers do not need a subwoofer.  If you have small speakers that cannot get those lows, or not the room for large speakers then I can see having one.  Subs in my opinion are great for home theater rumble, but I prefer a more balance less boomy approach.  I am sure many of the more expensive subs have smoother response on the low end, but I have no need at this time.  I personally am happy with out one.

I don't look for such a flat response spec, I look for indicators of good tone, fast, tight response. With Roon providing parametric eq options and many subs now offering similar via mobile apps its super easy to tune the sub to either your tastes or your room- both by eliminating boom, peaks, dips etc. 

Interesting question because:  When we insist on a flat frequency response, then mess with it with the cheap crossovers most subs have, we are at least starting with a sub that does not add or subtract info from a poor design.  Personally, I use a pair of subs powered by a dual mono stereo amp, allowing manipulation of the volume without changing the frequancy response.