Top notch speakers with their own sub

Jax2, in my opinion fairly flat in-room response is the goal in the bass region, and above the bass region, I prefer a gently downward-sloping curve. If I have to choose between too much and too little bass energy, I'll choose too little because that's less likely to be distracting.

Which brings up something else that most rooms do at low frequencies: Boundary reinforcement, sometimes called "room gain". Breifly, as we go down in frequency and the wavelengths become progressively longer relative to the distance to room boundaries, the first reflections become more in-phase rather than random-phase, so the net result is a roughly 3 dB per octave rise in bass energy as we go down below 100 Hz. This of course varies from room to room and with speaker positioning within a room, but since subs are usually placed close to the intersection of at least two room boundaries (on the floor and up against a wall) it's worth taking into account.

Without going off on a long semi-technical tangent, I'll just say that in my opinion a worthy "target curve" for a subwoofer system would be the approximate inverse of this 3-dB-per-octave typical room gain. If the subs are "flat" all by themselves, by the time room gain is factored in they will be bass-heavy. But if we have to err, imho best to err on the side of too much bass rolloff rather than not enough, so I'd rather have 6 dB per octave of rolloff (before room gain) below 100 Hz instead of none at all.

Duke

Jax,

Killing the nodes bewteen 50hz and 150hz makes a HUGE difference IME. Getting flat in-room response in this range is really worth some effort and -IME- it will take some effort. I use bassbusters for the octave above 80hz - which works very well - and active PEQ below. In addition to much improved impact, weight, and "punch", the midrange sounds cleaner. Really flat response in this region also allows a more seamless integration of mains and subs - if you're crossing this high. My rule of thumb, cross where it's flat. The bass will seem to be a natural part of a seamless whole - it won't "stick out" at all. At least, not to me.

Below app 50hz, the whole excersize becomes a lot more subjective - IMHO. Again, weight is impacted as is, to my surprise, soundstaging. I'd heard people make this claim before, but I was doubtful - it wasn't intuitive. As it turns out, getting it right down low allows deep bass notes to "bloom" and expand in a way that feels natural and seems to define a larger space. To my ear, there's a decently broad band around truly "flat" response that achieves this result. I chose to extend flat in-room response to 25hz because it measured well and sounded great. Other folk's MMV.

Marty

BTW I currently use a pair of 12" Rythmik subs which require much less EQ than the 8" Velodynes.

Jax2 writes:
>Hey Duke (or anyone else who cares to comment) - Is a flat response always necessarily an ideal target?

The goal is flat on-axis response with a gradual directivity increase (or decrease in total power response). Your ears take a few cycles to pick up low frequencies so total power response comes into play more there although there seems to be some time domain component with steady-state measurements being an incomplete approximation.

Floyd Toole and Sean Olive at the Harmann Group have done studies on this with blind listening and their computer controlled speaker mover. The preferences hold regardless of listeners preferred musical genre, country of origin, and experience/training in critical listening.

>What I've objected to in some other approaches is that you become very aware of the low end to where it becomes distracting. I don't know whether this is due to overemphasis, room nodes, or some other imbalance.

It's the room and speaker+listener placement. Peaks really over-whelm the music. Placement too close to boundaries increases the whole bass spectrum. In-phase bass signals in the music add +3dB to total power response at high frequencies but +6dB at low enough frequencies. The room has up to 12dB/octave of gain below its fundamental resonance.

Reducing modal problems and room/boundary gain does a lot for natural bass which is like music as opposed to some fast, slow, tubby, or thin approximation that's noticeable and distracting.

In re-reading this thread I may have given something of a wrong impression re: EQ vs distributed subs. I love the idea of distributed subs and wouldn't be at all surprised to eventually own a set. I might very well still utilize room analysis/EQ, but mainly to help optimize placement (room analysis) and fine tune for +/- 1db or so for the 1/2 octave above and below my chosen x-over frequency. I suppose that some additional PEq might prove beneficial if any little anomolies survive the placement excercise, but I suspect that it would be minimal.

Marty

PS Duke - is there pricing info on the Swarm and Planetarium systems? I didn't see any on your web site. Not that I'm thinking.....

Spatine writes:
>Discussion on sub equalization and placement going on today is precisely the reason I hesitate straying from the mainstream speaker establishment. Now I have more plausible theory as to why major speaker manufacturers don't want to package non-integrated subs with their main speakers for music listening just yet. The technology is not sufficiently developed.

The technology is _fine_. Existing implementations are audibly, measurably, and theoretically superior in real rooms. "audiophile" exposure to cheap one-note sub-woofers and poor integration have created marketing prejudice against separate woofer enclosures. Spousal acceptance of additional boxes is an issue especially when placement constraints are taken into account. Some products call for more technical setup procedures and measurements for the maker to tailor transfer functions.

Mainstream speakers sound like speakers not live music due to inherently flawed physics which are addressed in alternative designs. You'll end up with a much more natural sound, better decor match (at the fringes it's small companies with made to order products. Figured woods/veneers, inlays, and finishes can be mixed and matched), and spend less money (you're mostly paying for parts and a furniture maker's time).

Speakers like the B&W Nautilus Prestige (acoustically small drivers+baffles with damped transmission line enclosures) and RAAL Requisite Eternity (uniform horizontal polar response, and I'd guess that the vertical response matches up well around the cross-over frequencies) take some steps to get there, although tighter uniform dispersion interacts less with the room. Bass needs separate enclosures and/or dipoles. Room specific bass filter functions are a good idea.

> Secondly, the idea of having 4 sub is quite intrusive, one way to get into major fight with your wife.

All but one location can use smaller woofers (they don't have to extend below the room's fundamental resonance, so they're not really sub-woofers) in smaller enclosures. AFAIK Earl Geddes is using 6th order band-pass boxes which can be 6dB more efficient for a given cabinet size and low frequency cut-off than a sealed design. In theory they ring more than a sealed or 4th order ported design, but the room dominates time domain behavior. In theory they have more group delay, but you need cycles of audio to pick up bass. Generalizing from small "sub-woofers" sold to the mass-market with a strong resonance to substitute for real bass doesn't apply to good ported designs and shouldn't be applicable to 6th order ones.