Regarding Outlaw's addition of autoEQ to the 990, anyone know if this is still in the works or even a possibility at this point?

If so, will the eq logarithm be active in the time domain as well to reduce ringing or will it only flatten frequency response?

It's pretty hard to say. From merlin's recent posts, it sounds like it is still under consideration and may even be included in the firmware update that's in development. As for the exact mechanics of it, I'm even less sure about that - there's not a lot of info at Sherwood's site about SNAP.

IF the EQ system is anything like SNAP, then it probably doesn't measure in the time domain and do anything about ringing. Like most auto-EQ systems, SNAP attempts to flatten frequency repsonse.

From the Sherwood site: It's measuring how loud the bass is, which will vary from seat to seat, instead of measuring decay time, while will be more consistent across the room. Psychoacoustically, small improvements in decay time have a much more beneficial effect on the overall perception of sound than large improvements in frequency repsonse.

Also, 1/12th octave is too coarse for measuring and correcting, especially when other room correction systems are down to .7 Hz precision.

My P-965 comes in Monday. I'll have it hooked up some time next week and will let you guys know how well the SNAP EQ does or doesn't work. This feature, along with the better remote is why I chose the 965 over the 990, so I really hope it works.

This is what I feared...darn!! If all it does is work to flatten frequency, it will be fairly useless in my book as ringing reduction is more important to me.

I guess it depends on what you want it to do. In my set-up I've got a couple of peaks in the bass region I'm looking to tame. If takes these down and equalized my bass region,then I'll be happy.

Got my processor today, so I'll know by tomorrow if the thing works or not.

True, but ringing is just as important if not more so than simply a flat response. You may have a flat response, but if certain frequencies linger after they are played, you will still loose detail. For this reason, I'd rather have correct time to decay than a flat freq response. Until these processors employ correction in the time domain as well, they are simply a band aid to a problem.

It's also difficult to use EQ for taming peaks because they vary from seat to seat. A frequency that rings between two walls will ring for every seat between those walls. So it's more productive to use EQ for decreasing decay time, because it will be beneficial over a larger area.

Personally, I would use EQ to address some of the ringing and use physical treatments for smoothening out frequency response. Their benefits will overlap at some point.

Still, I would be curious to hear Jack's results with SNAP. If it can provide any benefit, then that's better than none at all.

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You know, I recently discovered this phenomenon as well. I had no idea eq could work in the time domain. You can read more about it here...

http://www.lexicon.com/products/details.asp?ID=15

I believe Auydessy does something similar.

Meridian and Lexicon pre-pros use the same approach, measuring in the time domain and correcting for low frequency ringing. Neither system operates above 250Hz nor do they make any attempt to flatten frequency response.

In receivers, newer Denon models do some similar stuff with the Audyssey system they've licensed; newer H/K units also do the same with their EZset/EQ system designed using some of the research from the audio legends at Harman (Floyd Toole, Todd Welti, Sean Olive).

Wayne, since you post at SMR, I'm surprised you haven't read more about how the Lex EQ system works. You can also read some discussion about this subject here .

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Wayne,

The Lexicon system does not do any averaging of the 4 mic inputs. It's inventor, Dr. James Muller, has made that very clear. If one mic picked up a dip and the other mic picked up a similarly sized peak, averaging the two results may cancel each other out and give the (mistaken) impression that there is no problem. The data correlation being used is more sophisticated than that.

What you're doing with EQ and what Meridain/Lexicon are doing with their EQ systems are completely different. For example: if those systems detected a hump at 70Hz, they would do absolutely nothing about it. They aren't looking for nor correcting anything in the amplitude domain. Instead they measure in the time domain, looking specifically for low frequencies that linger for the longest amount of time, obscuring details of sounds that immediately follow (irrespective of their frequency).

If a frequency matches a room dimension such that it keeps bouncing back and forth between two walls for longer than other frequencies do, then no seat placed between those two walls will be imune to that frequency ringing. So while levels can vary widely from seat to seat, ringing is more consistent in all seats. Reduce its decay time and you'll improve clarity across the entire frequency range, at all seats. Difficult, if not impossible, to get that sort seat-to-seat consistency when correcting for varying amplitude instead of varying decay times.

Keep in mind that it is difficult to measure decay times by looking at amplitude peaks, the way you are. That's because a ringing frequency may not be louder than other frequencies, so it will measure flat in amplitude but still have a long decay time. Other times, a peak is a symptom of a ringing frequency. In those cases, when you fix the problem (long decay time) you end up fixing the symptom (amplitude peak). So, even though they aren't attempting to do so, the Meridian/Lexicon systems can sometimes end up inadvertantly smoothening and flattening some of the frequency response.

Make sense?

BB4TB believes:

Perception is affected by the interaction of many parameters.

Most single corrective measures affect more than one parameter.

The best way to approach a given problem is to deal primarily in that problem's domain, for instance correcting room problems with room treatments.

As a result, there is an order to multiple treatments.

For instance, if a room has a 'ringing' at one or more frequencies to any significant degree, that ringing should first be reduced by room treatment. Because the room treatment for the ringing will also affect the frequency response in that room, one could apply system EQ to bring about a perception of even frequency response after installing room treatments.

If the attributes of the room are not treated, the ringing will add to the 'presence' of 'offending' frequencies. If the ringing frequencies are not electronically 'suppressed' to some degree, those frequencies will initially 'hit' at the 'correct' level and potentially build to too high a room amplitude. Additionally the subsequent decay of the offending frequencies will be prolonged. If one uses the usual types of EQ to suppress the offending frequencies to some degree, these frequencies will initially hit at 'too low' a level then build up and subsequently decay with the idea that this is more acceptable and balanced in the listener's perception. In such a case the blend of lows, mids and highs would be out of balance initially, until the ringing sets in to approximate a better balance.

In order to handle these interactive parameters with only EQ, one would need a heretofore-unknown-to-me type of EQ. An EQ that is continously 'analytical,' programmed, buffers in a 'store and release' fashion and actively adjusts - an EQ that affects each narrow frequency range such that when frequencies that will ring are detected as coming through the 'pipeline,' those frequencies will, for the first few milliseconds, be allowed to pass unsupressed in the correct ratio compared to frequencies that will not 'ring,' then suppression will be applied, increasing and then leveling off at the same rate as the ringing will build in the room and hold steady. After this, the EQ will somehow know how quickly the offending ringing frequencies should decay compared to the non-ringing frequencies and artificially suppress the ringing frequencies in the right amount and sufficiently 'early' such that in the listening environment the ringing and non-ringing frequencies will decay in their original decay ratio. And, oh yes, since each channel's speaker type and placement will provide the room with somewhat differing 'excitement,' make sure that all this frequency handling occurs independently for anywhere from 2.0 to 5.1 to X.Y channel playback.

IMHO, I think what one can do with attention to placement and $500 to $3K worth of room treatment plus potential 'normal' EQ will exceed what one could accomplish with over $10K of additional electronic alteration and no room treatment.

For those that have purist tendencies, adding room treatments in lieu of more and more electronics will also mean having the precious signal less-messed-around-with.

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Wayne, It's not a question at being more adept or doing a better job than you are. It's more a difference in approach.

Frequencies with long decay times may not show up as problematic amplitude peaks. For example, a frequency that's bouncing back and forth between two walls will have a long decay time for every seat between those two walls. However, if you move a microphone between those two walls, you'll find places where that frequency might be softer than others or louder than others. Somewhere between those places will be a location where this frequency is around the same amplitude as other frequencies.

If your seat or your measuring location happens to be at that spot, the amplitude of that frequency will appear to measure flat. However, it will still be ringing and still have the long decay time. In a situation like that, amplitude based correction systems wouldn't detect a problem and wouldn't do any correction. A time-based correction system will see the long delay and calculate an inverse filter.

Likewise, there could be a situation where your speaker and room combine to create a loud hump around 60Hz at your listening seat. An amplitude based correction system will try to correct that, to bring the volume level in line with other frequencies. A time-based correction system will check for unusually long decay time and, if it finds none, will do nothing. You'll still have the amplitude hump.

So it is two different approaches, each of which can sometimes totally miss a problem that the other is addressing. Agreed. Removing energy from a frequency that is bouncing back and forth between two walls in an attempt to lower its decay time can also make it appear quieter (and bring it more in line with other frequencies). But if the the latter were the goal of the Lex/Meridian systems, they wouldn't be going through the added effort of measuring in the time domain. So much easier to simply look for the loudest and most offending peaks and try to bring those down. That's what most of the EQ systems on receivers do. Precision aside, there is nothing magical about the parametric EQ used by Meridian, Lexicon, Audyssey and H/K. They're basically used to remove energy from a particular frequency.

The trick is being able to recognize which peaks correlate to long decay times and which ones don't. The Lex/Meridian systems can not only tell the difference, but they only attempt to correct the ones that correspond to long decay times, leaving the others alone.

Wayne, if you see four peaks between 20Hz and 250Hz, what method do you use to tell which of those has unusually long decay times and which ones don't? What if it is measuring from a location where a certain frequency isn't peaking in amplitude but does have a long decay time? If you believe it is correcting for peaks, then it will apply no correction there. If you believe it is correcting for decay time, then it will apply correction there. Which is it?

BTW, since it can't fix all the problems, it only goes after the most severe ones. For each of the 10 channels it corrects (7 main channels and 3 subs), up to 7 filters can be used. In practice however, Dr. Muller has said that they've never run into a situation that required more than 3 or 4 filters per channel.

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Wayne, What about frequencies with long decay times that don't show up as peaks? The Lex initially ships with 4 SHARC DSP engines. The room EQ feature adds 4 more. That still leaves room in the processor for 8 more SHARCs. Lack of processing power was not holding them back from doing the other "half" of the job. They are firmly against amplitude based correction. Keep in mind that if a peak is not associated with an unusually long decay time then it is left alone. It's not that they can't do something about it; it's that they deliberately don't do anything about it. It matters, because it's the difference between guessing and knowing.

Again, how do you know which specific frequencies have the longest decay time? After correction, how do you verify that that actual decay times have been reduced? What are you using to measure decay time and generate corresponding waterfall plots? No they won't. Meridian, Lexicon, Audyssey and H/K wouldn't have resorted to using time-based measurements if amplitude based measurement would have allowed them deal with long decay times. The H/K system is available on their AVR-435 receiver, which can be had for less than $500. The Audyssey system will soon be available on Denon's AVR-2807, which has a MSRP of $1099 (street prices will be lower). Not unaffordable.

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Can't speak for the others, but my neighbor has a Harman Kardon 635 and I helped him set it up. There is only one mike, but to do the setup you first run a set of tones with the mike in the center of the room and then run a "near field" measurement set with three more settings, one from each of the front L/C/R speakers. Interesting concept and good results.

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Hi Wayne, Please don't take this as rude but can I request a break from the fawning flattery? Only because it feels awkward at another manufacturer's forum and it isn't really relevant to our nuts-n-bolts oriented discussion. Thanx.

BTW, I mentioned the ability to quadruple the processing power only to indicate that their limited approach to room correction is deliberate and not due to lack of resources. I've heard a variety of anecdotal reasons, the main one being to make the most effective use of resources. So they looked at what room problems were best suited to being addressed by electronic means (as opposed to being best addressed by physical treatments). Obvious example: I don't think anyone feels that you can EQ a first reflection away.

Flattening and/or smoothening frequency response is something that can be dealt with using physical treatments or EQ (or, even better, a combination of both). The potential problem with EQ is that an improvement in one seat can result in worse sound at nearby seat, which is rarely the case with physical treatments. So, for this particular problem, it would probably be better start with room treatments and finish off with EQ where treatments aren't as effective (e.g., under 40-60 Hz).

For something like decay time, EQs can be quite effective. Moreso because we're dealing with low frequencies, whose wavelengths are large enough that an improvement at one location will benefit the sound at other locations. And there are other potential advantages: if you have unusually long decay at 37.5 Hz, how do you target that particular frequency with room treatments? So here is a problem where electronic correction can be more effective.

In the thread I linked to earlier, the former chief engineer of Auralex Acoustics said "decreases in LF decay are often more pleasing to the ear than decreases in LF level. Less muddy tends to be more pleasing than less loud, when given the choice". So if you take three things into account (where are EQ systems more likely to trip up and cause more harm than good; where is electronic room correction most effective in providing benefits; which benefits are more psychoacoustically pleasing to our human hearing), then you'll have three reasons why addressing decay time is a better use of (electronic) resources than flattening frequency response.

It's no wonder then that they limited their correction to decay time and limited the frequencies to the bass region. It was the best bang for the buck, had lesser chance of screwing up, and benefited the widest listening area. They weren't interested with correctness as much as they were with perceived improvement. Even if the two improvements are of similar magnitude, decay reduction sounds better than amplitude reduction. Part of it is that. Mainly I think it has to do with the problem they're targeting. If they were trying to flatten out frequency repsonse, they may have ended up using all 7 filters per channel. But since they've limited themselves to addressing ringing, they end up using 3 or 4 filters at most, leaving the rest in reserve (over-engineering, typical of Lexicon's studio/pro roots). No, the others all use a single mic. I don't know if Meridian uses multiple locations for measuring, but Audyssey allows you to position the mic at up to 8 different seats for correlation.

Besides a quicker measuring session, there is another advantage to multiple mics over one mic at multiple locations: reliability. The first thing the MC-12 asks the user to do is group the mics as closely as possible for a mic check. The input from the mics is compared and, if one of them is out of spec (relative to the others), the user is alerted and the results of that mic are discarded. With a single mic system, if the mic was bumped during shipping and sent a little out of whack, how would the user ever know? What are the chances of that happening to all the mics? Four mics may seem like overkill for a consumer system but, again, that's their studio/pro background showing through. I'm not trying to be diplomatic but I think the other EQ systems have their own strengths. For example: the Audyssey system does do some correction above the bass range as well as try to find the crossover point that provides the best blend between your speakers and subwoofers. The other manufacturers might want to look into stuff like that.

H/K does something even more unique. It makes you take 4 measurements: one from your listening seat and one each from the nearfield (literally within two feet) of each front speaker. Measuring from the nearfield allows you to hear what your speaker sounds like without the room's contributions (at least very minimal contributions).

This gives the EQ system three things to compare: the pure tones in the receiver's signal generator, the sound from the speakers, and what the listener is hearing at the sweet spot. So it knows what your speakers sound like because it can see how the original signal was changed. It also knows what the room added, because it heard the speakers with minimal room contributions.

Aside from some of the stuff we've been discussing, the H/K system uses the EQ as a form of tone control, to subtract some of the room's influence so you hear more of what your speakers actually sound like. Think about that for a moment: instead of using some theoretical ideal, it uses your particular speakers (warts and all) as a reference point. They're assuming you bought your speakers because you liked how they sounded. Again, I think the other manufaturers we've discussed should at least look at what H/K is doing. The main reason for using multiple mics or multiple measuring locations is to lessen the likelyhood that you are measuring from the null for a particular frequency and therefore not catching its ringing.

BTW, when the 990 first came out, folks asked about room correction. The Outlaws said something to the effect that they hadn't heard a satisfactory auto-EQ system (I'm guessing they meant within their price range). I can understand why they said that. Unless you are willing to license someone else's technology (Audyssey) or have a large research staff (H/K), most of the auto-EQ systems out there aren't going to make a significant improvement to the sound.

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Wayne, I hear some chirps (probably for time alignment) and some sweeps, but I don't know what the actual test tones consist of. The routine goes through the entire process twice.

BTW, you can always write to Jim Muller, the inventor of Lex's EQ system. It may take a few days to get a response, but he does reply to e-mails.

jmuller@harmanspecialtygroup.com Too bad indeed. However, if you're ever in the Los Angeles area, drop by. You can demo the room correction system to your heart's content.

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I wonder if the chirps are an MLS sequence sorta thing.

OK- newbie here, I'll bite.

How do you determine if your room is in need of treatments, and what those treatments should be?

I'm recalling a picture from very early childhood where my dad had a wall covered with egg cartons...

ALL small rooms are in need of some treatment.

Read my article on the matter....

http://www.sbrjournal.net/currentissue/articles/acoustics/Acoustics.htm

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I smile and salute braidkid. Certainly in any forum one will find differing opinions or dickering about the details, but you get my vote for a ‘practical, within reason, well thought out’ approach. Many of us will now be wishing for dedicated listening spaces and/or significant others with engineering degrees that will understand and allow a multi-purpose space to be ‘arranged and decorated’ with listening as a priority. Hopefully your article will remain available for others to read for quite some time.

Where else in this forum should reference to your article be made? In ‘Tips and Tricks’ there is the DIY Room Treatment topic or braidkid could start another similar topic. I’d post the reference there myself, but I think that should be left to braidkid.

My two cents: after obtaining a reasonably good system of value-for-the-dollar gear, spending some time and multiple $100's in room treatment efforts with limited electronic correction similar to braidkid and Doug917 is a wise choice before spending multiple $1,000's on esoteric cabling, ultra electronics, or dubious tweaks. One could always spend the $1,000's later if the resources are available, but the treatments would still be there and of great benefit.

Thank you very much for the compliments. I will allow the moderators here to post the paper where they wish.