Not to be a party pooper, but fixing a sub’s response for any one listening point in the room doesn’t “fix” the whole room.

Let’s suppose that at point “A” standing waves in the room provide a +6db constructive boost at 48Hz while at 32Hz providing destructive canceling by about -6db at that same point “A.” At point “B,” about 2 meters away at another seating position, the opposite occurs boosting 32Hz and suppressing 48Hz. Now using some form of detection at point “A” the user determines automatically or manually that some portion of the electronics should reduce the signal by -6db at 48Hz and boost the signal by +6db at 32Hz. A listener at point “A” now hears a “flatter, more even” response but the situation at listening point “B” is now twice as bad as it was before the measuring and adjusting.

Even the most perfect sub or system EQ done from only one measurement point means that the listener must plug one ear and locate the other at precisely the point the measurements were made to really hear every bit of the improvement. If the same frequencies are either over or under represented by the nearly the same amount at all listening points in the room, a simple one point EQ measuring and adjustment would be great.

Yes, but at least you'll have it adjusted for where you sit to enjoy your HT. At least you'll have a "sweet spot". May not be perfect for other sitting positions, but then again, my friends didn't donate any money towards the purchae of this expensive stuff, so they can shut their pie holes.

That's why they build in room EQ systems for receivers. We do the best we can until they come out with a "brain plugin"

I think that there are at least two reasons that go into including any feature in some equipment, the first is actual benefit, the second is marketing. I think marketing is the larger reason by a factor of 3 or 4 to 1. Whether or not a feature is actually beneficial is irrelevant: if consumers think some feature is a real benefit then when comparing brand A with the feature to brand B without it, the majority of consumers will pick brand A. This being the case, what company wants to be brand B is this scenario? Therefore, within six months of a company including some readily copied feature X in their mass-market models, most other companies will have their own version of feature X in their latest models. The fact that several manufacturers are including simplistic EQ in their receivers lends no real support to the dubious benefits of such a feature.

If you want room EQ to be generally beneficial in your room, you’ll need to sample about two dozen points within the listening areas of the room, toss out any oddball anomalies from the results and average the rest. After this make moderate adjustments.

A practical demonstration of why I think single-point sampling is nearly worthless:

If your computer is connected to your sound system, or can be, download a free sine wave generator. If your system-to-subwoofer crossover point is 80Hz, generate a tone of about 60Hz and play it back at a moderate volume. If you have an SPL meter, walk slowly from place to place in your room watching the readings. In my room with a steady tone I see at least a 10db swing from highest to lowest reading. Now do the same with 50Hz. Were the peaks and valleys in the same places as with 60Hz? Try again with 40Hz. After this series, try one for your other speakers by generating 120Hz and above. Even if you don’t have an SPL meter, you can plug one ear and move the other ear slowly about the room moving both horizontally and vertically. Likely you will find spots where a particular tone grows louder and other spots where the tone seems to disappear altogether.

Someone is going to say, “But the EQ systems don’t use sustained sine waves for testing.” That’s right. But consider this: every complex wave can be reduced to the sum of multiple changing sine waves. And this: musical notes are generally held long enough for some of their frequency components to establish standing waves in your room, at least momentarily. As a result, I consider the sustained sine wave example above a valid one as far as a worst-case scenario in order to point out the foibles of single-point EQ setups.

Bestbang4thebuck,

I personally, like to tune my sub to remove some of the room modes that are present no matter where you are in the room. ie a window rattles. Is that present everywhere in the room? yes..

Secondly, trying to reduce some of the boomy frequencies from my couch potato spot. This involves using the equipment I have (including a FBD) and generating a larger set of frequency tests that the amount you listed above. Then additional listening to a number of movies that I know cause problems at critical areas like Perl Harbour, LOTR, K-19, etc.

Really, we tweak these to our taste and thats the best we can ask for given room dynamics and our taste in hearing. Someone else given the same tools will come up with something different..

I am not attempting to come up with an average for the whole room. This is not a commercial theater, this is my theater and in my theater, you only have a few places to sit... By design..

Think of it as being a giant set of headphones that can hold 3 to 6 people in a 3600 cubic foot room...

I have tested most of the auto room setup equipment that comes with like the Yamaha RX2500, Denon 3805, etc. and they do a decent job of setting up a "giant headphone" for people that know zero about surround sound and like it that way.. Maybe in my books its not good enough, but I don't think its all marketing..

If you are the party type that has 50 people over, nothing will work as the room changes just by adding the warm bodies...

We all have our preferences on how to set these toys up. I am just voicing mine incase someone else finds it of interest.

Do what you like, if that involves standing on your head, kudos..

I didn’t mean to give the impression that I’m against all forms of EQ. I only meant to say that people who place a single microphone in the middle of a room and hit Auto EQ on a $600 receiver aren’t necessarily getting what they think they’re getting out of that process. I’m also saying that, because of consumer perception, receivers with such circuitry are going to be favored over those without.

Having a window with sympathetic vibration at say 42Hz is not necessarily indicative that 42Hz has ‘even strength’ everywhere in the room. On the other hand, just as a timpani ‘system,’ consisting of a variable tension drum head, a given volume of air contained below that and a ‘tuned port’ of sorts, has a natural resonance frequency, so can a room. I installed a pair of subwoofers in one room where, no matter how I placed the subs, there was a boominess if the music material ever strayed low. If I reduced the subwoofers’ overall level until that boomy frequency came into line, so much of the rest of the under 80Hz material seemed to disappear. Out came the SPL meter and signal generator. Turns out the room, with it’s fixed volume and openings, has a natural resonance about 34Hz. As a result, I had to adjust the overall sub level and placement to work well while ignoring data in the 32Hz to 36Hz range. However, while the overall tendency of 34Hz to ‘boom’ too loud still existed and an EQ suppression of 34Hz would have been helpful as far as not exciting the room’s natural resonance so much, even without EQ to reduce 34Hz, I was still able to find spots in the room where 34Hz almost disappeared. Bottom line: the behavior of standing waves is not tamed by EQ.

Which brings me back to a principle I would like to follow even if I can’t always apply it practically: deal with the source of the problem, don’t just put a Band-Aid on it. If the room (or a window) has a natural resonance because of it’s physical properties, I try to do what I can in the physical world before resorting to an electronic correction.

In the end, however, each of us does what we can, within limits, to achieve the sound we hope for. If your methods differ from mine, I have no problem with that. If the results you achieve are generally pleasing, then I offer my hearty congratulations!

May we all find the best ‘giant headphones!’