Subwoofer: should we even use them at all?

Lewinski,

I've used several active x-overs and I divide them into 2 groups. The analog models included a tubed Marchand, an NHT x-2, and the internal active x-over in my Theta Casablanca. The Marchand was too noisy for me, but that might be unique to that piece, rather than the model, since I've been told that others had more success. The NHT is an excellent piece (and IMHO a great value), but I ended up pairing it with a Velodyne SMS-1. The resulting performance was excellent, but the set-up was a giant PITA (thanks to the Velodyne) and the multi box/cable arrangement was inelegant. The Theta is a really flexible and good sounding unit, too - and a one box solution.

I moved to an Onkyo 5509 pre-pro after I heard Audyssey xt-32. A lot of A/B testing at a couple of local places led to a loan of an Integra pre-pro which I felt was (much, to my taste) superior to the Theta. The crossover in the Onkyo (like most modern pre-pros) is effected in the digital domain. I ended up buying the Onkyo version because I couldn't hear a difference in sound between it and the Integra version, it was significantly cheaper, and I preferred its appearance.

To the x-over question: It's hard to separate the performance of the digital x-over (vs the analog x-overs) because they were integral (pardon the Onkyo Integra pun) parts of two very different pre-amps/pre-pros. In the end, I like the Audyssey powered one-box solution of a pre-pro for my main 2 channel system and that means a digital x-over comes as part of the deal. Whether it's the digital cross, the room correction, the balance of the preamp circuitry, or any combination of the above, the bottom line is that I found it to be a better mousetrap. Since I had already effectively stopped listening to LPs in favor of a server (and consequently didn't really have to deal with the cognitive dissonance presented by ADC and DAC for my analog LPs) I retired my ARC LS-25 and Joule LA-150 without much indecision. As always, YMMV.

Hope that helps. BTW, I've never heard the Dirac correction package, but I've done a bunch of research on it: There's definitely some interesting software there. If you do pull the trigger on Dirac, I'd be grateful if you posted your take on its performance.

I also use the Onkyo PR-SC5509 with Audyssey Pro.

Above 99% of all people use Audyssey as Audyssey say you should use it. There is a big but......Audyssey does not think from the head of how highend is being used. And how big instruments and voices need to be in proportion.

The other limitation is the lost in dynamics. The first 2 times I did it as they tell people to use it. This was in 2010. I was not satisfied enough.

I had thoughts how it could be better. I developed my own way of measuring. These days we measure at totally different places and Heights.

We also measure the subwoofer differently than they do.

They endresuls are way superior to their quality in endresult. I never will share this information with another person. Even not for money. With this I have an extreme advantage over all my competitors. I never had such a big and convincing advantage in audio before.

The differences are: superior dynamics, speed, blacks integration, sharper focus, resolution and atriculation of voices.

The subwoofer is also a lot more dynamic and controlled than you can achieve with the Audyssey way of Pro.

We modified the microphone stand. The Audyssey stand is fully useless. We measure at mm precision.

The new outcomming Onkyo PR-SC5533 in September will not have Audyssey anymore. I will test it for Onkyo when it comes out. For me it will be far inferior in endresult. I still can sell the old one, The new one is good enough for me to sell. The level is not good enough to be used for myself.

In October 2011 Jeff Hedback (Hd Acoustics) and Nyal Mellor (Acoustic Frontiers LLC) published "Acoustical Measurement Standards For Stereo Listening Rooms." Hd Acoustics clients include Ozzy Osbourne, Lifehouse, and Trevor Horn. Page 19: “To obtain the best possible LF response boundary interference issues can be tougher to address. Varying the fixed distances from ‘speaker to boundary’ and ‘listener to boundary’ will reduce strong cancellations. It is a balancing act as one location that may offer a smoother LF response may not provide the optimal midrange and treble response ” (emphasis added) Page 20, paragraph 2: “ everyone desires a ‘flat’ LF response and no modal ringing. Simply, this is a tough achievement. The absurdly large collection of interrelated variables between two fullrange speakers and the room (speaker design, speaker/listener location, room size/construction and acoustical control within) makes this so. It is up to the individual to determine what their limits are as regards placement and acoustical treatments ” (some emphasis original, some added note the qualifying phrase “absurdly large“)

Let us narrow the discussion to bass reproduction systems (subs or full range speakers) properly tuned with appropriate system Q. Audiophiles wrongly describe such systems as having "fast" or "slow" bass, and such descriptions are misleading or worse. Would you want a low E string on a 6-string guitar to be "faster" than the high E? No, of course not. Low E is 82 Hz, high E is 328 Hz. Obviously, the Low E must be "slower"...two octaves "slower" to be exact.

Guess what? Bass is a slower wavelength vs. mid/treble. Of course it must be slower. Double basses are larger than violins by design.

"Slow" bass more accurately describes a bass mode effect unrelated to the speaker itself. Even though modal effects often result in Frequency Response windows of 15 dB or worse, that is not their worst and most audible effect. The worst and most audible effect is that the mode wavelength is completely outside the diatonic scale and unrelated to the original bass note pitch. After the bass note ends on the program, the modal effect continues bouncing between boundaries. Imagine two bass players, one of them plays perfectly, while the other bass is tuned a quarter tone off (sometimes plus, sometimes minus, depending on the mode), and he holds bass notes about a 32nd note too long. This is the inherent effect modes cause, which results in audiophiles wrongly using terms like "slow." Yes, the note didn't end, but the speaker is not reproducing the note, the boundaries make the note. We're talking about the equivalent of over 100% THD. We're talking about bass notes not on the music program.

There are really only two ideal solutions, neither of which require any EQ nor acoustic treatment for small 3 to 6 dB FR windows, and virtually no timing errors as described above. One is a Distributed Sub Array, the other is a Dual Bass Array. The latter might perform even better than the former, but the latter also costs about twice as much and ideally requires subs built into both front and rear walls.

A properly installed Distributed Array has no integration issues up to about 80 Hz because it solves the bass mode before it occurs. All other solutions are band aids attempting to fix the mode after the fact, including EQ, which can't solve the timing error.

Initially, three or four subs seems like 2 or 3 too many. When you hear the performance level, you'll wish you found out about it earlier and never look back. Even 1cf subs can reach -3 dB @ 20 Hz with enough power for HT or music. That's another benefit: ideal bass works just as well for music as it does for HT.

I, too, dislike the idea of calling bass response "slow" and prefer the term underdamped. I also like the idea of multi-sub arrays and have experimented with variations on the theme pursuant to some great posts by Duke of Audiokinesis, so I agree with a lot of this post, but....

Spkrplus wrote:

A properly installed Distributed Array has no integration issues up to about 80 Hz because it solves the bass mode before it occurs. All other solutions are band aids attempting to fix the mode after the fact, including EQ, which can't solve the timing error.

If "no integration issues" means "no room integration issues", this is an overstatement. You won't remove room effects with four (or more) subs, but you can greatly reduce their impact on direct FR and power response with careful placement. As a side note: EQ fixes the problem before it occurs, too. Once EQ filters are set by room analysis, the subsequent electrical (music) signal is adjusted prior to reaching the driver. Tho the filters are calculated "after the fact", that does not a band-aid make. If you doubt that this approach works, simply do an RTA of the direct and power response in the room (I use white and pink noise) post EQ. The benefits in both graphs are obvious, tho usually more dramatic IME on FR than power response.

The difference in power response improvement is - to me - the primary conceptual benefit of an array vs EQ, but per my own measurements, I wouldn't personally describe that delta as dramatic. My own array experiment - admittedly not ideal, two Velodyne SPL 8s and two 12" Rythmiks optimized for power response - showed power response improvement over the dual Rythmiks, but not wildly different. In fact, the power response and FR performance of that array was clearly improved by the application of Audyssey, too.

Proviso - a different subwoofer array implementation might yield different results, but my attempt was reasonably diligent. Had I gotten more dramatic results, I'd likely own an Audiokinesis array right now. To be clear, I wouldn't bet against me buying one in the future, but I'll still use Audyssey with it.

As for long wavelengths reflecting off boundaries (2 bass players), this happens with distributed subwoofer arrays as well as single subs. As a technical matter, it happens more - reflections for each sub are inevitable (4 or more bass players). Careful placement of the subs relative to the walls can smooth the response anomalies caused by each of these reflections, but they're simply smoothed in aggregation, not removed.

It's also unclear what "timing error" EQ can't solve. If you're talking about decay characteristics of the room, I don't see how a sub array would be helpful there either.

As for in-wall woofer solutions, they do effectively address the issue of reflection off the wall behind them (this is generally the worst IME) but there are still side wall, floor and ceiling issues which are certainly not trivial.

To be clear, I'm not dissing the idea of subwoofer arrays. I actually think it's a great idea. I'm just pointing out that the particular benefits of an array are overstated in this post and the objections to EQ are also overstated. Of course, the bottom line is a listening session. IME, thirty seconds with Audyssey should be adequate to demonstrate the benefits to most people (simply disable it during play). That doesn't mean it's preferable to a well implemented array, it just means that it's a very effective solution for the bulk of the problem. The best practical solution that I know of is an array with Audyssey, but, if you really want to "fix" the issue, an anechoic chamber (or room that effectively behaves as one) is the only solution that I'm aware of.

Audyssey Pro Is far superior in endresult compared to XT32.
The authority is a lot better. You get a different kind of sound in comparison to XT32.

It goes deeper and you have a much better timing and integration.