Subwoofer speed is in the room, not the box

@sfgak wrote:

Hadn't hear of Xilica before. Looks very interesting. Which model(s) do you have? 

The XP-3060. It's controlled wirelessly via my laptop, which makes setting filter values for every driver section on the fly from the listening position a very straight forward approach. Neat. 

@tomic601 wrote:

Sure bass horn loading is a different case…. i’m flat to 20 in a regular room without resorting to cutting down every tree in the mythical forest… Enjoy the music ;-) 

I was going to say reaching 20Hz is the easy part, but making that last audible octave and a half matter (say, down to 15-ish Hz) is no small feat. For it to really matter you need prodigious cone/air displacement area, ample power and/or high efficiency, proper flooring and overall room construction, etc. Numbers are easy; how they're real-world applied and experienced is quite another thing. 

Not saying what you've achieved with your subs setup is this, that or the other (obviously, I don't know), but all things being more or less equal (and that's the tricky part) the larger and more efficient subs setup will reproduce the lower octaves more effortlessly, relaxed and viscerally. Whether 20, 30 or more Hz at play here is at first secondary vs. how these frequencies are reproduced.

That horn sub variants need to be indeed very large just to reach 20Hz is another matter, not least with non-truncated Front Loaded Horns (I mean, for all practical intents and purposes in anything other than houses: forget it), but here I've found tapped horns to be the best option and overall compromise. For what they do at their size (20 cubic feet per cab with a 23Hz tune) with low distortion, high SPL output there's really no equal to my mind. 

@clio09 Then I will say it. John Hunter is wrong. He is interested in selling as many subwoofers as he can and not in designing the best possible subwoofer.

@tomic601 ​​@erik_squires @phusis This is not all that complicated. Most of you are right, you just need to be able to explain it better.

The speed a woofer cone travels is a sinewave function. The average speed to produce a note at a given loudness is a function of size. The smaller woofer has to travel farther to displace the amount of air required to produce the note at that volume so it has to travel faster. The speed is not an issue but "farther" certainly is. Dynamic speaker suspensions are linear only for a very short distance. At some point, depending on the suspension's design, the suspension becomes progressively stiffer until it can not move any farther without ripping it apart. Because of this non linearity distortion increases logarithmically with excursion distance. This is why larger drivers or multiples of smaller drivers have lower distortion levels. They do not have to move as far so they do not have to travel as fast. Bigger is always better, not worse!

Boominess has two causes, the subwoofer running into the midrange and a resonant, shaky enclosure. To keep the sub out of the midrange people historically lowered the crossover point. This is a problem for a number of reasons. Much of the impact or dynamic factor comes at higher frequencies in the 80 to 100 Hz range. You want the sub running certainly up to 80 Hz and I will go no lower than 100 Hz. The solution to this problem is running steeper filters, not lowering the crossover point. The problem here is analog filters are terrible at this. You have to have a digital crossover then 8th order and higher is no problem. Running that high a high pass filter for the mains is mandatory or you will have a hot mess. This is advantageous anyway from a distortion and headroom perspective. 

Making an enclosure that does not shake or resonate is a very hard problem to solve. The easiest part is using a balanced force design. You put a driver in opposite ends of the enclosure running in phase. The Newtonian forces then cancel out. Making an enclosure that does not resonate is much tougher and very expensive, more expensive than most commercial manufacturers will tolerate because they have to remain competitive. This is the reason I make my own. You can see a picture of the final versions before finishing. I plan on doing a full pictorial of their construction  so others can copy them if they are inclined. These will be high gloss black. The walls are 1 7/16" thick. Plywood was used instead of MDF because it is stiffer. The individual sections are only 4" wide. The subs sit on the floor horizontally on two spikes right up against the wall. They lean on a special pad. Because they do not vibrate at all nothing will get transferred directly to the wall. Small sealed enclosures are always best with subwoofers but you have to have a lot of power and high resolution digital EQ. Then you can make any sub run flat as a carpenters dream. 

The last problem is time alignment and this is best done with a digital crossover and room control which is really speaker control. 

With subs running up to 100 Hz and cut off at 48 dB/oct or higher, if you want more impact just turn the sub volume up a little and you can have it without affecting the midrange or treble. I run mine hot by about 6 dB which gives the music a "live" feel at less than ear shattering levels. A great subwoofer system is more felt than heard. In reality, the faster a subwoofer cone has to move the worse will be it's performance. 

@gdaddy1 

“Using my ears (crazy isn't it?) I concluded that if your main speakers produce good bass down to 50hz why restrict them? Why? Because it sounded better, fuller, more glorious. Plugging ports and making a sealed cabinet restricts cone movement. Makes the main speaker sound thin and anemic. IMO... if you want a sealed main speaker then it should be properly designed to work that way. Sealing ports and restricting quality speakers as an after thought is a mistake.”

I can rationalize that statement as I feel the same way. I was not sure if the original post is specific to home theater or two channel audio. 
 

My use of subs with my current speakers is only to exaggerate bass from old rock albums. Something like Back in the Saddle by Aerosmith or any glam rock bands of the 80s where double kick drum was predominant in the music. Def Leopard and Aldo Nova come to mind as well. During those sessions I rock out and am not really interested in the audiophile aspect per se, since the music is loud. When listing to more settled music such as jazz, or easy listening, say Eagles or Fleetwood Mac, I find myself turning the subs down or off..unless of course I want to feel that added bass because we are partying. 

I love the overall sound of my speakers as is, Classic Audio Field Coil Loudspeakers T. 1-5 Reference with 18” downward bass and 15” front mid bass, horn loaded with Fostex beryllium tweeter. 

I have been using the Velodyne SMS-1 bass EQ with great success to tackle optimization of 4 SVS 3000 13” subs..well, at my last room. My new room is much larger and I have a pair of 18” Rhtymicaudio subs coming soon for parties. Otherwise, I use the subs when I feel that I might  need extra bass which is occasionally and when experimenting. 

What Erik Squires mentioned about bass being omnipresent in way that feels as if it’s an event is usually realized when the subs are playing louder and providing that emphasis, or the main speakers have been castrated and a portion of the bass region output has been shifted to the subs. It’s definitely a feeling and sometimes more is more and maybe better. I just don’t see me adding another layer of crossover complexity to my straight audio chain since the designers of very capable speakers meant for their speakers to be driven with their designed crossovers to give the best sound for their speaker.,

I hate taking the time to see if this piece of music sounds better with that added feeling, when before, it sounded great as is, especially with big big extra large speakers that can play thunderously loud with pronounced bass depth when required. So, for me, bass augmentation is used sparingly. I am long past the crawl method, injuries  prevent that, but situating subs in good locations as a starting point and measuring away goes a long way. Check phase, and don’t be afraid to aim subs in directions that are not typical. Also, to add more complexity, what about Speaker Boundary Interference Response (SBIR)? This will surely come into play when setting up subwoofers. 

Using my ears (crazy isn’t it?) I concluded that if your main speakers produce good bass down to 50hz why restrict them? Why? Because it sounded better, fuller, more glorious. Plugging ports and making a sealed cabinet restricts cone movement. Makes the main speaker sound thin and anemic.

@audioquest4life

I think what you are missing from the original thesis is that how a speaker performs once placed in a room is very different from the measurements. Sometimes in good ways sometimes in terrible ways.

Your experiences are going to be very room dependent. In your room and with your speakers plugging those ports may sound "thin and anemic" which in another situation might sound less boomy and better balanced. I’ve heard from one A’goner that they found the perfect balance by plugging 1 speaker but not the other.

Nowhere do I universally suggest you should plug all main speakers, but that if you are adding a subwoofer it may be a good option to make it easier to integrate a subwoofer. What matters is the in-room bass response and which option causes fewer headaches to deal with in equalizing the entire system.

@audioquest4life  If subwoofers and main speakers are integrated correctly there is no reason to turn the subs up or down with any genre of music. A system that is tuned correctly does not care what genre you are playing. When I use the term , system I include the room in that category. 

Most audiophiles are ball parking it with their ears which are extremely poor calibration devices. There is no substitute for measurement.