Eh hem!...Subwoofers... What do ya know?


Subwoofers are a thing.  A thing to love.  A thing to avoid.  A misunderstood thing.  

What are your opinions on subwoofers?  What did you learn and how did you learn it? 


jbhiller

If subs aren't the most misunderstood thing in audio, I sure don't want to know what is!

Take me. Been into audio since the early 70's. Built my first amp in high school. My first speaker was a transmission line in 1978. Thought I knew all about sound and even so never could get really good bass. Thought it was physically impossible.

Until about this time last year, when quite by accident came across some posts about the Audiokinesis Swarm and started reading articles on the physics and psycho-acoustics of low bass and something called a distributed bass array.

This sounded promising and so after reading a ton of both technical theory type articles as well as feedback from experienced users I decided to take the plunge and built my own distributed bass array.

Based on the same Dayton amp and 10" drivers and cabs similar to the Audiokinesis Swarm this has turned out to be probably the most revelatory improvement ever. 

Combining reading and theory with a lot of hands-on experience this is why I say its so misunderstood. Almost don't know where to begin.

The problem of integrating bass isn't in which sub is used. Its in how many. Every sub no matter how good or how crap has the problem of room modes: some areas too loud, some too quiet. Most try to solve this with more power, or EQ, neither of which does anything but make the fundamental problem- which is physics- even worse.

With lots of subs (I run five) no one individual sub has to put out much power. So they all produce modes, but different modes in different areas because the subs are all over the place. All these small modes average out and the result is impressively smooth, fast, articulate and deep bass.

Integrating or matching with speakers is a non-issue. Read the reviews, the bass is so fast its a match for electrostatic speakers.

Low bass is non-localizable. But read that carefully. That means only you cannot tell where the subs are located. It is as if they don't even exist. It does not mean the bass they produce is unfocused. Quite the contrary, the sense of 3D location of bass is even more focused than anything else I've ever heard.

Location with one sub is everything. You can spend a lifetime moving here and there trying in vain to find the magic location with smooth bass. Placement with a DBA is trivial. You can go the Full Monty if you want. You might even notice an improvement. Or you could just plop them down one near each wall, bothering only to not have them be symmetrical, and congratulate yourself on your expert placement. Either way, state of the art bass.

Almost everything people "know" about bass is wrong. Take timing. Experiments show we cannot even hear low bass at anything other than a full wavelength. That means a 20 Hz wave has to last 0.05 seconds or you won't hear it- at all! Midrange though you can hear in a tiny fraction of that. The same timing that is crucial to imaging and midrange on up simply does not apply at all to sub frequencies.

I could go on and on. Which I tend to do, both because this is so important as well as its really hard to understand. Took me a few weeks of research to really be sure myself. Sure enough to invest $2k anyway. Which is a stone bargain. Nowhere else in audio can you blow away so much expensive gear so easily for so little. Provided only that you actually understand what it is that you're doing.
(1) One sub is not enough, for reasons given by @millercarbon. (2) Subs can be used to extend LF, but the most important use in many systems will be to fill nulls unavoidably caused by main speaker placement and room geometry. (3) It’s easier to get them right if you have measurement capability. (4) I prefer to have a high-pass filter on the mains and a low-pass filter on the subs. (5) If you know when the subs kick in, you've done something wrong.

@millercarbon - do you run your array in mono? Just curious.
@millercarbon - do you run your array in mono? Just curious.


The smart-alecky answer would be yeah, because all low bass is mono. Seriously. It is.

Which I know from Duke reporting on what's his name Floyd O-Toole? Or the other one? Whatever, the car audio engineer who analyzed a couple hundred recordings and they were all mono so he called it good and designed for mono bass.

Me, having 2 Dayton amps allowed trying stereo, 2 on each side, and two per amp. Also tried mono. Tried mono connecting all 4 to one amp, mono 2/2. These were all different. But not because of stereo/mono. Because, all low bass is mono. Oh there may be an exception out there somewhere. He only tested a couple hundred, after all. So if anyone reading this finds one send it along, as nobody who's looked into it has found any, they will think its cool. 

What does make a difference though is impedance. Wired 4 ohms the bass is just a bit tubby to my ears. Wired 8 ohms the bass is not so tubby. Wired 16 ohms the bass is tight, taut, articulate, like way better than anything I ever heard anywhere else. Not lean. Plenty full. But fast. Clean. Maybe even a tad more dynamic.

Technically you do trade off some peak power, so if those last few dB of volume really matter and you like really full round bass then wire for 4 ohms. 16 to me is so much more articulate and tuneful, and I like that enough to put up with the occasional clipping when the movie effects go boom.

In terms of stereo/mono though one of the more amazing parts of the whole DBA thing is the way such low bass, which we really cannot localize, nevertheless somehow manages to image so well. I can only guess that what happens is when the low bass is this good then when we get the location from the midrange it blends seamlessly into one whole and so it seems the bass is as much grounded in a real place as everything else in the sound stage.

This is a whole different thing from the way midrange on up works. Anything much above 120, 200, somewhere in there, if its mono its gonna be between the speakers. Where exactly, not my thing. Duke would know. Duke knows everything! (Seriously.)

For those who haven't heard this (DBA) I don't want to give the wrong impression. Its not like the bass is always imaged the way everything else is. Sometimes the bass is completely enveloping in a diffuse, this is just the size of the room kind of way. This I think is one way really good bass improves imaging, by extending it to the point you are enveloped in it. But its also something that is very recording dependent. If its not on the recording you aren't going to hear it no matter how many subs or what kind. Sometimes when listening its like man are my subs even on? When it is there on the recording though, wow!
What are your opinions on subwoofers?


Hard to integrate well. Glorious when done right.

What did you learn and how did you learn it?

That’s a really good question. I started off with an M&K satellite/subwoofer system. Bought into the hype, used a passive 2nd order crossover (yeah, enormous toroids) and a couple of different RTAs to attempt to get the two to play well. Honestly they never did. The best I was able to do was use a little room math to damp the peaks.


The rest of my answer is a little long, but the short version: I integrate subs as if I’m building a speaker.



Here’s the long answer:


The V1B subwoofer eventually fell apart and I parted it out on Ebay, sold the S-1Bs.

Years later I was in San Francisco and got into upgrading speakers, and that led, very rapidly to learning speaker analysis and making my own. Now mind you, I have some professional background in analog and I was lucky enough to audit classes at Georgia Tech when I was too young for the math. Point is, I didn’t just jump into speaker design from zero.


One thing that changed a lot in my favor was the availability of cheap test and simulation tools. DATS, OminiMic and XSim made everything I wanted to do a lot easier, but none of them were useful without having a background already. The other thing that was new was miniDSP having a number of affordable and very high feature active crossovers.


Even with this background I made a couple of choices that really made everything a lot easier:

  1. Stick to 2-way designs
  2. Measure the bass response in place.
  3. Use OmniMic instead of REW, just because for my needs OmniMic held my hand a lot more.


Had I not done that, I would have made plenty of mistakes in analyzing the mid-bass response, or gotten overwhelmed with the quasi-anechoic requirements of a 3-way (this is short-hand, please don’t jump on this sentence).

Anyway, after this I returned to wanting a sub. Based on reviews including those at:

data-bass.com

I went with a Hsu. They were out of the model I wanted, but for a couple of hundred I could get the next larger unit. What arrived was the size of a small refrigerator, and me in a small apartment!! Hahahaha.


Anyway, I tried a number of ways to integrate the sub, bought a pair of GIK Acoustic soffit traps, and the miniDSP HD balanced. What finally worked for me was this:

Treat the sub exactly as if I was adding a 3rd driver to my speakers.

Which meant measuring the acoustic distance, putting in the response of the satellites and subwoofer into XSim, phase/time matching them and then using OmniMic to simulate EQ’s.

Pant flapping glorious.