Subwoofer calibration for HT is a pointless waste of time (1 Viewer)

[Carl Johnson]

The sub is the one part of my system that i'm not disciplined enough to leave set at the level recommended by Video Essentials and my spl. In that regard i'm not treating my system any differently than the typical adjustments I made from the booth back when I was a projectionist. By the letter of the law the main volume control and the sub level were supposed to be left in a preset position but 95% of the time that wasn't the case. It was an everyday thing to turn down the volume to pacify customers who thought that reference level was too loud and when an action film is playing adjacent to an auditorium featuring a less aggressive soundtrack the sub was turned down to keep the bass from being heard where it wasn't wanted.

 

[ChrisBee]

Carl

This sounds appalling!

It takes me back 25 years to a classical music record recital at a public hall. I was sitting beside the person in charge of changing records and starting and stopping on cue from the person doing the musical introductions at the front.

That amplifier volume control knob must have cost the helper severe repetitive strain injury after a couple of hours! He cranked it up on every quiet moment and back down every time things got a bit exciting.

It was the most boring musical experience of my entire life! Robbed of contrast and vitality the music was utterly meaningless. Yet the people involved in providing this pale reflection of the real thing. Were the most ardent, enthusiastic and deeply knowledgeable classical music enthusiasts I've ever met!

ChrisBee

 

[Mike Keith]

Wow, you really think your local theater has a great sound system compared to a properly set up HT? I'll have to agree with the original poster here, personally I think my system is far more dynamic and has much better, cleaner, deeper and more satisfying bass then any theater I have ever heard. I guess north Texas has a bunch of crappy theaters, glad your local theater is so good. Also the point about a theater system filling large areas is a silly point, if I crammed all that theater equipment into my 14X14 room I bet it wouldn’t sound any better then my system in a large theater would, that’s comparing Apples to Buffalo IMO. Also take a SPL meter to a theater someday I’ll bet the noise floor is the same or worse then your home, after all the theaters hear in Texas at least have air conditioning too. I’ll go out on a limb hear and state that a commercial theater has far more compromises in sound then a typical HT properly set up in a typical room.

 

[Garrett Lundy]

The teenagers ahve to read 90db's easy in a public theater.

 

[Lew Crippen]

Even though the thread title is no doubt intended to arouse passions and cause people to made even more passionate posts in reply, there are a few points in the first post worth considering:

This is only true if you believe that the engineer has no idea of what the filmmakers intended in their soundtrack and that the person at home had a substantive idea of what the filmmaker intended. A good many people watch some movies on DVDs without having seen them in the theater and consequently have no idea at all as to the LFE sound level intended by the filmmakers. And even if the movie had been seen once or twice, I would fully expect that the engineer transferring the movie to the DVD is able to (and does) spend a lot of time listening to specific parts over and over to try to reproduce what is expected.

To be sure, this may be done imperfectly, but to state that an opinion of the proper sound level that is often based on no familiarity of the source material (and even if there is some familiarity, that familiarity would rely on memory) is equally as valid as a skilled technician who has access to the source and can listen to it as much as he likes, is simply not logical. Of course, if any person decides that for him, he likes more or less LFE or more or less surround, they are free to change as they choose.

But ‘preference’ is a far different thing than ‘valid’. What is valid is what the filmmaker intended. That is the base. Changes to the base, even if they provide for a more pleasing reproduction are not valid as to the intent.

The fact that some manufacturers try to provide a more pleasing video reproduction by reproducing reds with a bit more intensity, and that many viewers like the ‘red push’, does not make the ‘redder’ picture more valid. It just means that some people like it more.

 

[Alex-F-V]

This really surprises me that no one ahs directly adressed this issue.

How am I, as a user, supposed to get my "reference level" if I cant get a measureing device that is the same as the engineer's. And all of you people who say you get your speakers to refrence level and then turn your subwoofers 'hot' are hypocrites. You are doing exactly what he is saying. Setting your speakers up 'correctly' and handling the bass on your own, and setting it by your ear.

And if I have diffrenet sources... say rap music, very bass intensive, or am watching Good will hunting, with little to no bass. And what bass there is, is not emphasized. It would only make sense to have different settings for different kinds of things. Set your bass accordingly to your taste.

People always make the point about buying speakers here that a buyer should really listen and buy the ones that sound best to him. But if I set up my speakers according to what the enigineer of the movie thinks sounds best.... Shouldn't I buy the speakers that he thinks sounds best. No that wouldn't make sense.

Set up your speakers in the way that suits you best.

And I find it obnoxious to think that you should set your system up for 'prime' listening position and ignore the rest. For those of you that think this, it would suck to be your friend.

 

[Lew Crippen]

The implication here is that calibrating for the prime listening position means that everyplace else is bad. This is, at least in my room, not correct. There is a sweet spot, to be sure, but the rest of the room sounds pretty good as well.

I’m not sure that it is possible to set everything up to be the same in the whole room—without a lot of money, at least. For example, in most rooms, a person sitting closer to the right side of the room will hear more right channel surround effects and less left channel sound. I am not aware of an easy (or even moderately easy) way to correct for this problem.

In any case, I’d let my friends sit in the prime location. At least as long as they brought the beer.

 

[Brian L]

I would say it is a physical impossibility.

With a lot of time, money, and smarts, you can make sure that several locations do not suck, or maybe even sound OK, but there is one and only one sweet spot.

If you go for the average, you loose the ability to make one single spot as good as it can be.

I am with you Lew, in that, I do set my room for a single sweet spot (its actually a bit of a family joke...Dad has to sit THERE for the best sound in the room), but to non-enthusiasts, defined as everyone I know BUT me, my room sounds just dandy, no matter where they sit.

BGL

 

[Ned]

Pearls before swine as they say

 

[Mark Seaton]

Hi guys,

First, thanks for giving me a great example for installers and customers why education and understanding of how a system works is so important.

The biggest problem appears to lie in people taking the term "calibration" too literally or to the extreme. In simple terms, the "calibration" is nothing more than a gain structure setting to get your system to be the same overall loudness. This gain structure exists in the relation of a recorded level to produce a known C-weighted level. Once you have the gain structure set, with say the center channel, the rest is a matter of matching and integration. This is why we can still get significant improvements with a cheap SPL meter. It only needs to be consistent or precise, not necessarily accurate. As has been pointed out above, if the system response is not extremely well behaved, it is difficult to determine an exact level. The recorded noise signal does give us a better approximation as it's content (in this case 500-2kHz) will tend to average out typical peaks and dips due to room interactions. The standards were created with the intent of mostly flat system response. If this is set as a requirement, the test tones all of the sudden are more relevant and consistent from system to system. Why should a standard be modified for a poorly performing system? Just so everyone can feel better that they are "calibrated?



This is a matter of understanding the measurment method and what they do and do not tell us. The confusion here is entirely surrounding the subwoofer level; and understandably so. I've posted here and elsewhere why simple noise measurements are easily skewed by poor frequency response. If your subwoofer response has a big peak at ~70Hz, the test tones and your meter will read higher than they should for a subwoofer with a smoother response. You will set the sub level lower, and now all of your deeper bass will be much too low. This is why we find ourselves riding the sub level. To compensate, we increase the level to bring up the low end for action sequences, yet then an event with more upper bass comes along and that 70Hz peak becomes annoying.

Just as was the case for the main speakers, unless the subwoofer is in a wonderfully designed room, there will be significant response variations, and the simple test signals will only be a starting point. Those sine waves are very useful for determining general response variations, and even more useful in getting your subwoofer and main speakers to better match at and around the crossover point. It should also be made clear that "flat" response is not always percieved as "flat" in all rooms. The size and decay rate of the space will shift what is percieved as equal bass levels. This is probably the most difficult factor to guage and the toughest to quantify. While you still want a smooth integration to the mains, below 40-50Hz there is definitely some room for variation for things to sound "right."

It is important to have a good set of test methods and tools combined with some understanding of both what the standards are and what the intended purpose is. The hope is that we can more reliably recreate an experience representative of what the recording engineer and director originally concieved.

Hopefully we can get this thread back on track to offering some knowledge to those who hold the belief presented in the title.

 

[Chuck*W]

From Mike:



Right you are. I've been arguing for calibration (of sound, of picture) to recreate, to the best of our ability, the film that the director intended. If people want to modify that to suit their taste (or circumstances), that's their choice. But I think the closest we can come to the intent is the best starting place. Calibration with pink noise and bass tones isn't perfect, but it will get people close and I don't think it should be dismissed out of hand. For people who want more, there is the BFD (among other options).

 

[Mike Keith]

Lets not forget that an important part of calibration is the distance settings, since most older Processors use a physical measurement, they don’t really apply. However, the newer units, (at least a lot of them) have Auto Distance and Auto Level setting modes. This IMO makes a good bit of difference in overall realism, the auto distance on my Halo sets the Sub at 17’ even though its only 7’ away (physical measurement). These newer methods actually measure the acoustic distance of each speaker which is part of the time alignment between the subs and the mains. Also to expound further on what Mark Seaton’s excellent reply said; having your sub equalized and relatively flat in room will in my experience help when doing level settings for the sub. My auto-level was spot on with my subs pre-corrected, I hardly ever feel a need to boost or cut the sub volume level, it’s usually perfect

 

[Mark Seaton]

We should remember that when talking about choices made by the mastering engineer, a DVD soundtrack has the distinct advantage that some marketing mogul isn't insisting the media also sound great through a kitchen clock-radio or a mid-80s OEM auto system!

 

[Ned]

As such, shouldn't any correction/equalization be done before calibrating?

Here's my latest before/after in my tricky room (8'x10'x12.5').



So without equalization, if I calibrated my subs as is, they would only be "right" for the peaks at 20, 50-60, or for the trough from 25-50hz.

 

[Brian L]

Absolutely.

 

[Kevin C Brown]

All a pre/pro or receiver is doing when it sets a distance to the sub as 17 ft or something, is correctly adjusting phase, and hopefully the time alignment as well. (You *can* have a sub in phase but out of time aligment with the mains.) There's nothing magical about it in that you can also do it manually with the right knowledge too.


A good way of putting it.

 

[ChrisBee]

I think Mark hit the nail on the head when he mentioned a flat subwoofer response. (in his earlier post)

Given the average room this must be the most difficult part of achieving balance between the speakers and subwoofer. It's like trying to measure accurately with a piece of string if there isn't a reasonably flat frequency response from subwoofer AND speakers in the calibration region of their frequency response.

It would seem that calibration is an area ripe for further development with ever advancing digital technology. Multiple automatic filters responding to test tones received from a microphone placed at the listening position. Should become an affordable reality for all AV systems before long.

ChrisBee

 

[Chase_Smith]

I calibrate my subwoofer using Avia to set a standard for myself. I know my room has peaks in it, so I make the smallest compromises possible and I'm very happy with the result.

No one is saying we can get the subwoofer "perfect", but we can try and get as close as possible, and there's nothing wrong with that.

As for your "taste", I'm more prone to letting the sound engineers with their much fancier equipment decide the level of bass in soundtracks, and have a neutral system to accept their decisions, rather than try and adjust it to my own standard and have a movie like Underworld come along and shatter my little world.

Also, it's nice to calibrate simply because you're relieved that your subwoofer isn't putting out too much bass, possibly overdriving it. Nice sanity check there.