We give up perspective to avoid tone controls

 @ erik squires—Phase matching of subs-to-mains should always be optimized at the applicable crossover frequency, and the measurement point to define the match should be located (precisely) at the intended listening position. When ported speakers are involved, crossover frequency waveform propagation becomes more indistinct, diverse, and increasingly affected by room-induced peaks and nulls that muddy the matching precision. (I use instrumented-means to accurately accomplish phase matching. If interested, request my related white paper. I am at geyer.bryan@gmail.com)

Sustained wide area phase matching is a fantasy, and any expectation that synchronized phase can persist over more than a small part of the home listening room, or beyond the limits of a given test frequency, is misplaced. This reality should not be construed as a significant shortcoming; refer 4.8.1 of Floyd Toole’s epic “Sound Reproduction”, 3rd edition (Routledge, 2018, ISBN 978-1-138-92136-8).

Phase matching of subs-to-mains should always be optimized at the applicable crossover frequency, and the measurement point to define the match should be located (precisely) at the intended listening position.

OK, with you so far...

When ported speakers are involved, crossover frequency waveform propagation becomes more indistinct,

<< cough >> No it doesn’t. The crossover frequency doesn’t move around depending on the sub's cabinet type.

diverse, and increasingly affected by room-induced peaks and nulls that muddy the matching precision.

Which is why you should deal with the sub’s overall response first, and then the crossover matching second.

Peaks and valleys are easily dealt with by use of bass traps and EQ, regardless of whether the sub is sealed or ported. Again, if you like sealed, that’s fine. However, the crossover frequency and how it matches the subs is at the top of the sub’s range, not the bottom, where the room modes are (hopefully) less frequent and severe.

What often confuses listeners is that the same speaker, ported, will go deeper, and therefore is more likely to run afoul of those room modes. The peaks and valleys you mention.

Sustained wide area phase matching is a fantasy, and any expectation that synchronized phase can persist over more than a small part of the home listening room, or beyond the limits of a given test frequency, is misplaced.

Which is weird, because this is the very opposite of what you are attempting to discuss in your first sentence. It’s also a point no one has brought up, but since you have ... this all depends on how co-incident the sub and main speakers are, the measurement area, and the crossover frequency. If the sub is directly underneath the satellites, this is hardly an issue in most listening rooms.

At 80 Hz, 1 wavelength is 14 feet long. A quarter of that is around 4 feet. That’s how much the distance must vary from ideal before you have significant change.  So if you have two subs and satellites are right next to each other, so that in the center of the room, they are equidistant, you'd need to find a place in the room where the sub was 4 feet closer  or further away to you than the satellite.  On the other hand, if you use a single sub, located in the center, then yes, listening directly to the sides is probably this far. 

And like I think you are trying to get to, those peaks and valleys will make a much bigger deal than microsecond phase matching of the sub. However, they are just as hard, or easy to deal with in a ported or sealed speaker which covers the same range. So far it seems to me you are conflating phase/amplitude matching at the crossover frequency with the rest of it, which I don’t really get.

Best,


E

E—Thanks for such comprehensive clarity; I generally concur. But my simple comment (that it's easier to phase-match subwoofers-to-main speakers when all speakers are sealed, not ported) was never intended to apply to idealized environs filled with bass traps and EQ correction. Nor did I intend that phase matching be conflated with time-of-arrival correction. It's generally not possible to accomplish the latter in the average home living room because decor dictates that the subs go into the room corners and the mains go up front, more centered. Given these typical limitations, it will always be easier to synchronize the phasing (at the xover frequency, at the prime listening location) if the speakers are sealed—not ported.

The extent of the phase convergence will be determined by the prevailing acoustics. In my own living room (no bass traps, strict WAF control), measurements indicate that closely matched phase won't prevail beyond a few feet from the prime listening location. Regardless, accurately phase-matching the subs/mains yielded significant audible improvement, and an instrumented means to accomplish the match was lots less tedious than doing tweak-and-listen trials.

I generally don’t feel the need for tone controls in my system. I have a nice sounding room, nice accurate speakers, but my CJ amps and pre-amp add a touch of romance.

But I also sometimes use my old Eico HF-81 14W integrated amp. It has basic treble/volume control and I have no problem using them. I used them to dial in the sound I like for that amp. (But once dialed in, I don’t feel any need to bother touching the tone control again).

I personally don’t care to get in to the mind set of trying to tweak my system to every, or most recordings. That to me is too distracting.

That said, the ONE area in which I wouldn’t mind some tweaking control is in adding subwoofers to my system. I haven’t got them set up anything near perfectly, but I love the effect of full range for lots of tracks, but the occasional tracks I prefer without subs. I’d like a pre-set or two that dialed back the sub, or at least the lowest frequencies, at the touch of a button. (And if I implement the DSpeaker Anti-mode unit that I have, I should have such a control).

prof—I'll try to help. It sounds as if you've got TWO separate subwoofers. Correct? What make/model are these subwoofers? And are these subs self-powered, with their own (independent) internal power amplifiers? If not self-powered, how do feed audio signals to them, and from what source?