Should I build the wall? Not a Floyd question.

J

jbracing24

Junior Audioholic
To Takeereasy:
Nice drawing, by the way. The realities are that a lot of us don't have bigger rooms to work with. Having a dedicated room is a quest in itself. The idea of the wall should work better than a curtain, simply, to keep your sound in and outside noises out. So, insulate for that reason. Too bad that you couldn't leave the room open and just close off the stairwell from sound going upstairs. Keep the sound scientists out of it, work with what you have and experiment. That's the fun of HT. From a fellow Ontarian.
 
Ethan Winer

Ethan Winer

Full Audioholic
Gene,

> I can send you the white papers <

Great, thanks. The best email address for me is on the Contact page of my company's web site.

> this is technology that is well peer reviewed and has a lot of sharp people involved in it. <

Sure, but understand that I'm a pretty sharp guy too. :cool: I've been deeply involved in all aspects of audio and music for about 40 years. And if you need credentials, you'll find plenty on the Articles and Music pages of my personal web site, as well as on the Articles Page at my company's site.

> Audyssey's fuzzy logic which does 250 coordinate points with phase and distance calculations for each listening position! Then multiplies that times 6 or 8 (points of calibration) and you've got a lot of points of similarity to match up within each small frequency range. <

Fine, but any correction applied is still only an average, no matter how sophisticated the averaging may be. And again, that addresses only the raw low frequency response. Modal ringing, and the inherent narrowness of modal peaks, are at least as important as raw LF response if not more so.

> In small rooms like (12x10) for example, it’s usually not practical for people to throw in bass traps and sound panels. <

I'd be remiss if I didn't mention that ceiling corners are a great place for bass traps in small rooms because they're completely out of the way.

--Ethan
 
B

bpape

Audioholic Chief
1. How are active EQ systems going to deal with nulls and cancellation issues?

2. How are they going to deal with ringing and decay times?

3. Look at the cost difference between something active that will actually work vs. a few well placed passive acoustic treatments.

I'll stay with treating the room thanks.
 
gene

gene

Audioholics Master Chief
Administrator
Ethan;

I emailed you the papers. There is plenty of math in there to keep you entertained. Again this is NOT averaging please read the papers and it will correct for multiple positions at the same time and derive a very accurate transfer function of the room response.

Bpage;

The Audyssey system will help with phasing issues as it will find the best sub/center channel splice for the most seemless transition. This is something you cannot do passively. It will also properly phase multiple subs to prevent them from cancelling if their path differences to the listener are different.

Nobody is saying NOT to use passive treatment, but the technology is now here to do passive and active treatment for a much more complete result. Passive room correction will not do everything this system can, and this system wont do everything passive room treatment can do which is why they compliment each other. If you get a good RT60 time in your room, this system will really shine. Its your call if you want to ignore the benefits of electronic room correction, but someone who is serious about audio reproduction would want to keep a more open mind about new approaches. Up until I heard this system I wasn't a believer of electronic room correction, but I am now!
 
B

bpape

Audioholic Chief
I'm not saying there isn't a place for active - just that the active has it's place, the passive has it's place. I agree that both can coexist. I personally run a 5 band parametric just on my sub with the lowest band being set @ approx 17Hz and the highest being at around 50Hz. It is invaulable for taming a few peaks and adjusting things for my liking as well as slightly extending the response in the room.

I'm still having a hard time understanding how an active device is going to deal with one seat differently than another. I'll do some more reading I guess. The one active system that I heard that did a pretty good job(still did nothing for RT60, little for nulls, etc.) was the Tact. However, when you consider the cost of something like that, I can get another sub to help smooth things, get a basic analog parametric, fully passively treat the room, and have money left over. I'm not saying it's not a good solution but it's certainly not for everyone.

One last thing, if I get a good RT60 passively, have speakers natively having good flat response and place them correctly, have a sub properly placed in a room, crossed over at an appropriate point for smoothest transition, what am I gaining over a standard parametric EQ to deal with bass/room interactions? Sounds to me more like a box to do it FOR me instead of making me experiment.

Like I said, I'm not saying don't use it - I'm just trying to figure out what the benefit is for me if I've taken the time and effort in equipment selection, room treatment, parametric EQ,proper setup etc. already.
 
gene

gene

Audioholics Master Chief
Administrator
Bpage;

Active room correction needs not be expensive. The Audyssey system is integrated into 2 receivers so far and is working its way into more budget receiver and even HTIB systems!

If you really are interested in how they accomplish MultEQ successfully, check out our review of the system. If you want to see the math and phsyics of this, I have white papers I can email you. These papers are very math intensive so you better brush up on multi variable calculus and geometric series :)

BTW, using a single band PEQ will allow you to place the subwoofer(s) in non ideal locations. Its not always practical to put the subs in the positions of the room where they will work best. Using a PEQ really opens up a lot of options.
 
B

bpape

Audioholic Chief
Yes. I'd like to see the papers. I'll see what I can do about my calculus ;) If nothing else, I'll have my kid help me through it!

Like I said, IF they can actually make something like this work for multiple locations, that would be great. I'm still not a believer that it can deal with ringing and cancellation issues differently for different places in the room. I'm willing to read and find out. What specific receivers have this built in?
 
gene

gene

Audioholics Master Chief
Administrator
Unless your kid has a Masters/PHD level education in mathematics, he may have some difficulty as well.

Even passive room treatments have limitations in dealing with nulls. Again, this system isn't meant to replace passive room treatment, but to compliment it and do things that passive room treatment simply cannot do. Email me and I will forward you the papers.
 
Takeereasy

Takeereasy

Audioholic General
Thanks Jbracing. I think they may have lost me a little along the way, but I think their intentions are good. lol. I am just looking at this as a learning experience for when I move into my new place and get to set eveything up in a bigger, more suitable room. Hopefully I'll have a better grasp on what to do then. Always good to hear from a fellow Canuck.
 
J

jbracing24

Junior Audioholic
To understand the basics, I recommend reading articles that speak to the common man. I found a helpful supplement in "Audio/Video Interiors" and followed that to build my HT, from seating to sub placement, screen height to room configurations. But my favourite magazine is "Sound and Vision" which I consider best-in-class. Through their reviews I've got a Denon 2805 on my wish list. The rear speakers are already in place, though not in use. Just need the $CDN.
 

plhart

Audioholic
In following ongoing audio research over my career I'm aware of the many failures the quest for a full-range, active electronic system has engendered. Many have tried and documented their efforts, even in failure. From time to time in other fields, medicine for instance, we've read that a breakthrough on a particular problem has finally taken place because a researcher has looked at a problem from a totally different perspective and it is this totally different perspective that causes the breakthrough.

This is my understanding of how Audyssey came about. Tom Holman, as related in our Audioholics interview, posed the problem, then defined the parameters within which the project would be considered successful. In support of the Audyssey piece I was writing for Audioholics after my interview with Chris and Tom, Chris Kyriakakis sent me the 11 articles which his group have already presented to various peer associations such as IEEE and AES. If Gene has sent you these papers you'll see that Audyssey's multi-faceted mathematical theory was postulated and refined by Sunil Bharitkar, Chris Kyriakakis and Philip Hilmes.

The 11 presentations describe the various innovative approaches these three men took over the five year or so of development it took these to finalize Audyssey which is actually the project name under which a variety of different technologies were perfected. Exactly how and to what degree various turns were taken or decisions made within this basic framework is where "intellectual property" takes over while patents and/or other methods of protection for their work moves forward. This tact is common and intelligent practice for protection of intellectual property.

Next point>>As Tom Holman explains in our interview, THX is a methodology for eliciting the most faithful-to-the-director's-intent recreation of his acoustic vision within the confines of (first) movie theaters and later Home Theaters.

The problem with THX, if you want to label it a problem, is twofold.

a) Until recently, there did not exist a "holistic" program for a home theater to meet all "THX'-intent" criteria because the room acoustics were not taken into consideration.
b) Even now, it is virtually impossible for THX Home Theater certification to be achieved without calibration and sign-off by certified professional installers which means >
c) Cost, as is almost always the case, becomes the main issue.

Audyssey is an attempt to drastically reduce the cost of such performance in a Home theater environment. Given my two limited listening sessions with the product, both of which I reported on for Audioholics, IMHO this technology works exceptionally well and should easily fulfill its promise as a cost effective, legitimate and audible set-up, calibration and room correction solution.

In time of course, the system will be backwards engineered and its inner workings reported on. Buy my point here is that we don't, we can't, in fact know these answers ahead of time. We can only report on results of our listening. I will confess that I've come to a few of my own conclusions just mulling over the facts before us all. But supposition without extended listening is merely guessing. And you know what that's worth.

For now I give the whole Audyssey crew the quiet respect I feel they've earned.
Defining some of the other systems.

R.A.B.O.S. is a product using a 1/20th octave parametric equalizer which has been on the market two years. It works in the 20Hz-100Hz region. Any user who works with this manual system can see the before and after (at the listening position(s)), room curves. My take as to why this system has not been more successful is that most people, even reviewers, are just too darned lazy to take the time to set this system up properly. Once, you do it, and hear the incredible difference this system achieves, you're trained to always listen for this flat, tuneful, realistic bass in every system.

The Lexicon system, just by juggling a couple of numbers that they do publish, would appear to be capable of over 1/300 octave resolution or 0.73dB from 20-250Hz. And it's automatic. So this system would seem to be even more accurate than the R.A.B.O.S. within this specific (and expanded) region. I did hear a short 3 minute demo of this system at CES and it sounded great. The sub/full-range speaker blend the Lexicon/Revel team achieved in their demo room was about as good as I've ever heard. I plan to report more on this system when I interview Dr. James Muller who has graciously already accepted my invitation.

The one active system that I heard that did a pretty good job (still did nothing for RT60, little for nulls, etc.) was the Tact. However, when you consider the cost of something like that, I can get another sub to help smooth things, get a basic analog parametric, fully passively treat the room, and have money left over. I'm not saying it's not a good solution but it's certainly not for everyone.
We bought one of the first Tact 2.0 systems at Alesis back in '96 to use as a loudspeaker development tool. IMHO the Tact was excellent for the purpose I had in mind whith was to chart 9 points in space around a listener's head. This mapping was meant to define the listening window for a mixing engineer using the Point Source D'Apollito studio monitor I was designing at the time. I listened in mono, with the speaker just off the center of in a room with an acoustical tile ceiling. Heavy theater curtains were draped all around the DUT and the mic position.

In the times I attempted to use even a single speaker mic combination without my semi-anechoic atmosphere it immediately became apparent that
a) the room characteristics where intruding on the measurement and
b) that the resultant speaker "equalization" did not sound as good when the theater drapes where again placed around the speaker and listening position.

Tom and Chris made two points during the interview which became more clear to me after I ingested then pondered those 11 papers.
a) To get good sound in several positions requires hundreds of points around each listening position which define a listening window within a room.
b) There is a defined time-window, in this case 200 milliseconds, which will give the best information on direct versus reflected sound.

The last points which I added into my Audioholics Audyssey article are:

a) The room was already passively treated to yield an exact, (down-the-middle of the .2 to .4 millisecond reverb time recommendation window). 0.3 second, Rt60 reverberation time.
b) From my understandning, sound energy, by octave, is re-distributed, to the greatest extent possible, using proprietary techniques. And it is claimed that the signal, at the listening positions, remains minimum phase across the system's entire bandwidth of operation.

Now can we please get back to answering real world questions for our readers who take the time to ask?
 
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Ethan Winer

Ethan Winer

Full Audioholic
Gene,

> I emailed you the papers. There is plenty of math in there to keep you entertained. <

I got them. Thanks very much. I'm not a math guy - not even a little - but I know how to read the "Conclusion" section. :D

I'll be back with some comments after I've had a chance to go through it all. That was a lot of stuff you sent!

--Ethan
 
gene

gene

Audioholics Master Chief
Administrator
No problem Ethan. I hope you enjoy them. I am a math guy, but most of this goes beyond what I consider fun. The algorithms they developed for room mapping makes a trip to the moon seem easy :)
 
Takeereasy

Takeereasy

Audioholic General
My girlfriend actually bought me a subscription for Sound & Vision for Valentines because I like it so much, and I have used their home theater set up dvd. I found it usefull, except, it seemed to want the darkness setting on the TV to be too black. The Denon 2805 would be on my short list of receivers for sure, and I'm jealous. I am more worried about a 5.1 setup for right now because of how woefully short on space I am. 7.1 would be wasted on me. I am still looking to match my fronts and my rears so I am way behind there as well. So much work ahead. Good thing I'm glutton for punishment. ;)

The wall will be built using cunning, know how, cheap labour (did you know you can pay friends in beer?) and a Home Depot reference book.

Thanks jbracing24
 
B

bpape

Audioholic Chief
Sounds like a plan

Good luck on your project. Sorry we got a BIT off topic there ;)

Let us know how things turn out for you.
 
Takeereasy

Takeereasy

Audioholic General
I forgot to say thanks to you too bpape, sorry. And thanks again for wishing me luck. I'm really not too worried about the wall, I've got a little building experience and the friends that will being paid in beer are all buddies making a living in construction that owe a few favours.

By going off topic it just gives me more to think about and excuses to go to to the local audio shops. Although I have to admit much of this topic was over my head when I looked into it (I had a hard time with advanced statistics so this stuff makes my head hurt) I still find it an interesting read.
 
J

jbracing24

Junior Audioholic
I almost forgot the most important tool I use to keep everything in balance especially on the video side, thanks for reminding me. Sound & Vision's Home Theater Tune Up DVD is a great learning for basics. I got it on-line, either at Future Shop.ca or Amazon.com, I can't remember. It's often advertised in the magazine. Yea, it suggests the Movie mode for picture quality, which can be a little dark on some of my DVD's I've made from PBS shows. That's why most TV's give you 4 modes to adjust to the program. But I prefer the Movie mode for almost all viewing and I gasp at friends whose displays are in the Vivid setting. Yikes!! A nice and easy way to shorten the life of your TV.
 
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B

bpape

Audioholic Chief
Takereasy,

Don't worry. It makes everybody's head hurt! Acoustics in general not a simple topic by any stretch. Fortunately, it's one of those things that you can follow along with the basic theory and learn from there. There is no substitute for experience. The other thing is that every room/system is unique. If you want a good primer on the basics, check out Alton Everest's Master Handbook of Acoustics. The plot is a bit slow ;) but the basic information is very good and covers a wide variety of topics.
 
Takeereasy

Takeereasy

Audioholic General
Thanks guys, and I'll give the book a look if I can find it locally. I have hit a little snag though. The basement. actuall flooded this week.. Not bad, but all the sewers around my block are under a foot or more of snow and ice and then we got 2 days of hard rain. Looks like I get more to deal with then I bargined. Oh well.

Thanks again and take it easy guys.
 
Ethan Winer

Ethan Winer

Full Audioholic
Gene,

Thanks, I finally had a chance to look through all of the articles you sent me.

> The algorithms they developed for room mapping makes a trip to the moon seem easy :) <

Indeed!

As best I can tell, all of those articles address only ways to average the EQ applied to help/harm as uniformly as possible for different listener locations. I didn't see any references to resonance, ringing, nulls, or any of the other important acoustic problems that I explained cannot be solved using DSP.

I'll gladly take your word for it that the math in those articles proves there exist clever ways to minimize the damage EQ causes at locations other than the prime seat. But I saw nothing that disputes my claims that DSP is no substitute for bass trapping. None of those articles address modal ringing, the narrow inherent bandwidth of modal peaks, or the importance of avoiding early reflections. To my way of thinking these are the most important room acoustic problems to solve.

I also found the use of 1/3 octave graphs to be naive, since using such a low resolution hides the true extent of the very peaks and nulls they are attempting to improve.

If I'm overlooking something, I'm sure you'll tell me! :D

--Ethan
 
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