Sibilance how do I get rid of it?

I am currently experincing a problem with sibilance in my system,I must admit I know that unless I set up a overly dampened ( lack of Hi's ) set up, I'm almost always going to have some degree of siblance,I listen to mass produced commercial cd's so I know that this is atleast 40% of my problem , and my listening room 26'x14'x8' is relatively live,,lanolium dampening,,etc,,
But somewhere in the back of my mind I hear "you need to do careful system matching,
My system consisits of:
Cal Aria MkIII CDP
Conrad Johnson Pv10a Pre
& Conrad Johnson PV 14L Pre
Llano A100 SS Amplifier
Dynaudio Contour 1.3 2 way's "GLORIOUS Midrange and Presence"
JPS Labs superconductor FX Ic's
Tara labs Time and Space with TFA Return speaker cables
Transparent Power Plus Power cord &
MIT run of the mil powercord on the Llano power amp
I have no power conditioning whatsoever except some hospital grade junction boxes in which I have the CDP & Pre's hooked up-AMp straight to the wall.
Now I have experimented with various IC's and speaker cable Discovery,Cardas,Transparent..etc
I don't want to address this problem thru cable choice
I have changed the tubes in the CDP as well as the PreAmps
the Jps labs provides me with the transparency speed and extended Hi frequencies,,and resolution, but with noticable
sibilance could it be the Ac line conditioning or lack of it that is introducing the stridency and graininess to the sound? if so where can I start?
What brand power cables offfer the best shielding or get's the GRUNGE out? I've heard good things about coincident
I knwo that I should ( and AM in the process of)addressing the room itself carpet is in order and some accoustic paneling to kill the early reflections,should I do this first? then get the ac conditioning? has anyone had any experience with Marigo Powercords, shuyanta, Coincident etc.
Please offer me your suggestions
I was told years ago that the Marigo cords are a musical cord and should help with your problem. Your CD player is also a problem and should be addressed. I feel that sibilance is increased with slow or restrictive interconnects and speaker cords, and this should also be looked at. Jeff
i assume you have already do so, but speaker positioning heighth wise and direction in which they are pointed can be critical. i solved a similar problem by crossing the axis of the speakers in front of the listening position - it eliminated sideway reflections. vertical tilt can also have an effect. good luck.....
"I knwo that I should ( and AM in the process of)addressing the room itself carpet is in order and some accoustic paneling to kill the early reflections,should I do this first?"

You've got the acoustics of a grade-school cafeteria --linoleum floors? To answer your question--YES. Go buy some very good acoustic treatments, foam will be fine, a nice Turkish rug for the floors would look great if you want some styling, otherwise just get any carpet in there. I would straight to Istanbul to get the best prices for the Turkish rugs. Get back to us once that's done.

"I have changed the tubes in the CDP as well as the PreAmps
the Jps labs provides me with the transparency speed and extended Hi frequencies,,and resolution, but with noticable
sibilance could it be the Ac line conditioning or lack of it that is introducing the stridency and graininess to the sound? if so where can I start?
What brand power cables offfer the best shielding or get's the GRUNGE out?"

The room is probably so bad--I don't see how you could even hear if those are really your problems.

Speaker/room interaction is still the most important. Hit the sidewall first reflection points first, the center wall between the speakers, and then the wall behind the listener. Search previous threads on room acoustics and maybe get a good book on the subject "Audio Cyclopedia" or "The Master Handbook of Acoustics." (don't recommend these guys as much)
My experience: switch ALL solid state rectifiers (CJ eqpt. & CD player - especially CD player) to Hexfred or UF diodes. If space and budget permit, change all PS (especially CD player) and cathode bypass caps to Black Gate or Cerafine type. If you can't do the mods yourself, find someone who can - it will save you hundreds if not thousands in component and cable upgrades. IMO -an easy and inexpensive ($300.00)solution is the Welborne Labs Gatekeeper or similar (Chang?) non-active power line filter/conditioner. Shunyata is nice (I own one in addition to the WL unit mentioned above)but expensive - the Welborne will get you 90% of the way there for a lot less $$.

Best of luck -
The 3 times I have heard Dynaudio Speakers they allways struck me as Sibilant. SS amps do not help matters.
Dynaudio are ruthlessly revealing speakers,I don't think they are bright, if you hear sibilance from them the problem is either the room or your upstream components, cables included.

In your case it sounds like your power is really the culprit followed by your room.
As far as I know every system has a problem with sibilants to one degree or another. But obviously some much, much worse than others.

I am confused a bit as you attempt to include your room acoustics and demensions into the equation. Having an extremely live room adds reverb/echoing affects but should never change an 's' sound to a 'shhh' sound. At least as far as I can tell. I just don't see the connection.

Of course, electrically noisy neighborhoods, inferior recordings, IC and speaker cables, and components could inject all sorts of junk into the signal leading to sibilants and other ill effects.

Assuming that your neighborhood, recordings, and equipment are not contributing to the problems, I believe sibilants has everything to do with the purity of AC power.

With that said, I would recommend the following tweaks:

1. Well, I can't really recommend this one from a safety perspective but it is a fact that grounding your AC outlets introduces much noise into the AC. Removing the ground has the opposite affect. Isolated grounds are better that common grounds. No grounding produces the best results.

2. Install a minimum of three dedicated circuits/lines. One for the amp, another for your digital source, and yet another for your pre. You are probably aware that digital adds much noise to the circuit it is connected to. Therefore, any other equipment sharing that circuit will also pick up much of that noise and eventually will amplify it. At the very least get the amp and pre onto it's own dedicated circuit/line, and put the ditigal on an undedicated line. Assuming your equipment is of a certain caliber, you should notice a tremendous improvement with this relatively cheap tweak if you stop right here.

3. For your dedicated circuits/lines, use an upgraded romex wire, not just the cheap 12 gauge available at Home Depot. I'm using 10ga. 99.95% OFC romex which is still very cheap compared to any other tweaks you may do. Do not allow for any breaks (junction boxes) between the service panel and the outlet.

4. Some will say that one phase or leg of the service panel can make your system sound better than the opposing phase or leg. I don't doubt it. If you have alot of motors and/or dimmers on one phase at the service panel, then it is entirely possible your dedicated audio circuits will produce cleaner AC if they are on the opposite phase.

5. Install some audio grade wall outlets such as FIM at $60 an outlet.

6. Eqaully important is a first rate AC power conditioner. I happen to be using Foundation Research LC-1's in-line power conditioners for digital and pre and an LC-2 for my amp. These are not cheap by any means but since these take the place of a power cord and an active power conditioner they could be considered somewhat of a bargain. Two Foundation Research LC-1's and one LC-2 will set you back about $2000. Considering that good active power conditioners are quite expensive and you still need aftermarket power cords, $2000 is a pretty good price.

The Foundation Research LC's work directly on the sibilants problem and you would immediately notice a very serious improvement here. Not to mention a much lowered noise floor in general and greater imaging and dimensionality.

7. If you've bought into anything I've said thus far, then you could even entertain a few more extreme tweaks. For example:

o A second AC line to the house dedicated to your audio equipment. It's as close to the outside power transformer as you're going to get.
o A beefed up silver or high purity copper industrial grade service panel and circuit breakers. A friend bought one for over $1k but then later found an even better one for about $250.
o Converting some or all of your gear to 230volts and run 230 volts (balanced power) straight from the service panel. Audio equipment connected to each other but connected to opposing phases/legs at the service panel can introduce noice into the AC.
o Install the new service panel as close to your system as possible.

I've performed suggestions 1 thru 6 above and noticed very obvious improvements with each tweak made. I no longer perceive sibilants to be an issue in my system. They've made such tremendous improvements at the micro- and macro-dynamic levels that I fully intend to one day perform most/all of step 7 just to see what additional benefits may be gained.

Again I'm assuming that your neighborhood electrical, your equipment, and your recordings played are not serious contributing to the sibilants problems you may be experiencing. If this is true and you do the above, sibilants will no longer be an issue to you. But getting to bed at a decent hour will be.

As far as I know, there is no other remedy to actually resolve or seriously deminish your issues with sibilants. Somebody correct me if I am wrong.

One last note: if you should decide to purchase any kind of power conditioner (active or passive), just like any other component, there are good ones and bad ones. Of course even the bad ones can receive good reviews. And there are some popular ones out there that are even worse than not having any power conditioner at all.

Try this first as I have similar floors. Buy a nice area rug you like and lay it as close to the speakers and as far out into the room as it will run. Then listen to the sibilance. Any difference? Now what are you components sitting on? Try this as it won't cost much and lets you hear what the sibilance is doing. Take one maple butcher block and place it under the cd. The take one Dr scholls' foot rub cut into three cubes. Place two under the front of your player and one on the rear of it, not under its listen again. Is your sibilance decreasing? Let me know how you do. You want to locate the problem without throwing money at it. Good luck....
I will second everything Stehno said. I think AC power is the primary source of sibilance, followed by interconnects and cables. Some seem to be better and worse than others. I just changed interconnects and the remaining sibilance that is not "recording related" completely disappeared.

Another tweak that will help considerably is to suspend your cables off of the floor. Made a huge difference in my system. I don't know what the dielectric of Linoleum is, but I believe it contains a lot of PVC (and who knows what else), so I suspect the dielectric of the floor is not helping the problem either.
In my case source components were always the biggest offenders. Swap your CDP with another one see if that helps. I am not familiar with your CDP, but rest of the system looks fine, so you may have to spend some $$ for the CDP to be up to the rest?
With a checkbook.
Stehno did a remarkable job of describing how to fix an AC problem, if it does exist--and can often be the culprit. However, in your case, you need to concentrate first on the weakest link, and then work towards other areas. You may need to do some work on the AC, but you absolutely need to do some work on the room. With a very live room you will have reverberation times that are very long (RT-60), and you perceive them as separate distinct tones from the original recording--thus sibilance. All our company does is small room acoustics (by small I mean residential, not theaters or studios). You can try by just starting to get some absorbing material in the room, and you will immediately notice a difference (carpet, drapes have been suggested). If you really want to get the most out of your system--the performance that the equipment is really capable of, you might consider hiring an acoustical engineering firm that focuses on residential listening rooms(don't get a studio engineer to design a home listening area--it usually does not work out well--there are of course exceptions).
I recently treated all connectors (power cords, rcas, xlrs, spades, bananas) in my system with deoxit and progold. I believe that it reduced the sibilance in my system. This is a quick and inexpensive 1st step to try.
thanx for your many responses,I will try these and see what becomes of it,Mbhcid,could you tell me more about these upgrades? I vaguely remember someone talking about this before, what is wrong with the current rectifier's in the CDP? and the Pre?, do you say change Ps ? (power supply?)
please follow up ,,, in short I guess the best way to explain it is it sounds almost like the amp is showing (allowing me to hear) too much resolution in the 3k-15k region this is the only way I can explain it...which translates into Grainy hash what do these powercords do in effect,,,clean the AC and inturn,,allow more resolution?....please help me understand this
thanx in advance
Upgrade the power cord to your CD player if possible. A PS Audio Lab II for instance. It makes all the difference. Also, set your CD, pre, and amps on vibration isolation feet/stands. Also as suggested upgrade your AC outlets to audio grade, cheap at $50 bucks each from PS Audio.
I have to agree with the respondants above that mention room treatments. Yes, AC problems will contribute to sibilance, but before you take any really elaborate electrical measures, you really should get a big carpet. Also, try putting some kind of material on the wall behind the speakers and between them to dampen reflections. These don't necessarily have to be audiophile wall treatments, sometimes a wall hanging tapestry or something like that will work. Experiment with speaker placement too. Those contours have tweeters with excellent dispersion and should be fine pointed straight ahead (no toe in) this will also reduce sibilance. Try experiment ing with different listening positions as well (higher lower, forwards backwards.) If this does not solve your problem, you should start working on AC problems and experiment with cable.
This is a tough one to solve. Nothing in your system can I point a finger at except possibly the solid state amp and the silibant and harshness from your software. A switch to vinyl front end would definitely help.
Ezmerelda, Rives, and Esun are correct. You have a good system in a terrible room. Nothing you do to the system will be correctly quantifiable or justifiable before you address the room. A $200,000 system would probably exhibit the same problem in that room. Do a simple experiment: With a helper or two, try to carry on an intelligible conversation across your listening room for a while, separated by a distance about equal to your listening distance. Then relocate to your living room and try it again. Then ask yourself whether you may have experienced a reduction in effort and an increase in comprehension once you and your party moved out of the basement. Nothing in your whole system, other than the source material, has a greater influence on what you hear than the room. Start there, and you'll likely end there. Best of luck, keep us apprised!

Let me tell you my friend. Your're problem is mainly- beyond the shadow of a doubt related to the quality of your electric mains. Phase anamolies between your tweeter and mid range driver have some effect. But just leave all as is. It's due to your local electric company.I can only listen mid September thru April. After that you might as
well spend your time with Budweiser. The above A/C remedy may help but best to leave it off. I do however have one consolation. If in a house. Place a ferite clamp on the incoming lead of your panel lead. do use cation.
AC line conditioning can go a long way toward allevieting sibilance issues in my experience. I use the Chang Lighspeed products, a 2500 for source components & a 9900 amp for (guess what) the amps. A 6400 ISO or a 9600 can do it all for you since you're not running large watts. Yes I also use upgrade AC cords & a dedicated AC line.
So if testing the system at midnight shows no reduction in sibilants from the daytime, then it is not the A/C power. Power conditioning would not be needed. From what is being said here.
I don't agree with the timeclock theory. Noisy power is due to many possible reasons, not necessarily load-related. The only way to determine if line conditioning will help is to try it, using *decent* equipment (not the lowest budget cheapest thing that you can find).
I have a pair of the Dynaudio 70's. I found using a pair of the Ah! LS Noise Killers on the speaker terminals really helped to smooth out the top end. They're only $50/pr. from Upscale Audio and they are easy to use. I don't know if this will help you but it might be a cheap fix.
I could be off base, but all the suggestions about electric quality, while good, won't help you with your problem. I think the sibilance is endemic to your source material. If you are listening to recently produced pop/rock material, then you will hear a good deal of sibilance. An unsophisticated/untrained vocalist singing into a condenser micropohone only an inch or two from his/her mouth (as is typical in an isolation booth) can produce tons of sibilance. Frequency keyed compression (de-essing) can lessen the problem, but compressing only a portion of the vocal range introduces its own set of problems and can sound somewhat unnatural. Additionally the current trend of applying massive amounts of compression to the final mix further accentuates sibilance. If the sibilance is embedded in your source music, then there's not much you can do about it. The above suggestions about room treatments, electricity and tubes can help with your system not adding siblilance to the music.
Correct me if I'm wrong but I would suggest that those who poo-poo the idea that AC is the main culprit for sibilance have probably never experimented with or altered their AC. Or they may have experimented with AC a bit but because of their equipment, did not notice any difference.

Last night, I tried something I've been wanting to do for some time.

I have three in-line power conditioners and three dedicated circuits/lines for amp, pre, and source.

I removed my Foundation Research LC-2 from the outlet to the amp and installed a cryo dipped Hubbell 20 amp IEC to ends of my dedicated 10ga. OFC romex and plugged it directly into the back of the amp. No outlet, no breaks, etc., just straight from the service panel to the back of the amp.

Although I noticed a tad better dynamic headroom, which was expected since the LC-2 is a bit enemic for my amp, the most noticeable degradation was the enhanced sibilance on female vocalists and cymbals. The difference was fairly substantial.

I put the LC-2 in-line power conditioner back in and sibilance is once again essentially gone.

And I know for a fact that if I were to remove all 3 in-line power conditioners, the sibilance would be greater still.

Cleaning up the electrical undoubtedly enhances numerous aspects of a decent or better system. In my experience, sibilance is at the top of those enhancements.
I must agree 150% with Stehno's experiences above; very nicely described as well. Certainly I experienced the very same things when I performed essentially the same experiments several years ago, but with different equipment.
Stehno, are you saying that improving the quality of electricity will actually lessen the sibilance already embedded in the recordings, or will it simply prevent your system from adding any more sibilance to that which already exists. If the music signal contains sibilant effects, then your system should accurately reproduce this recording artifact. My earlier post argues that modern recording techniques will produce a good deal of sibilance within the recording. Improving the electric quality can't hurt, but it will do little to eliminate what is part of the music signal.
No,Onhwy61, I am not saying that at all. As I already indicated in my earliest post I am already assuming that recordings and equipment are of a certain caliber.

And by that I am implying sibilance is not embedded in the recording to any appreciable degree.
Dont waste time with AC. Its the last thing you do and you do it when you have all the right gear. Dont spend money there unless you have the best source you can afford.
If you need to spend 1 K + on AC spend it on a better source insted.
Garbage in Garbage out.

Yes AC make a difference. But is should be addressed last or if fortunate enough first.

And yes the source material can kill you if its bad. New pop recordings are horrible.
that guy has absolutely NO idea what he's talking about---
but certainly we ALL know that by now
Bob B., please explain exactly where you disagree with Natalie's statements. Natalie may be blunt, but I don't see where anything he's said above warrants such an outright dismissal.
Dedicated circuits for cleaner power are a farce, in my opinion. Here is why I think so.
My living room light comes on with the timer tonight. The light bulb blows instantaneously while I'm listening to the stereo and my speakers go "phlam!" Not pop, even bigger than that.
My setup is a dedicated circuit on the opposite side of the circuit breaker box than the living room circuit. Furthermore I have a Tripp-Lite Isotel surge protector. The bulb blowing was probably too low to trip the Isotel.
Obviously all the circuits in the house are interconnected so I think this "dedicated circuit" is a farce. If somone can explain otherwise I am open to that.
The only reason I can se for dedicated circuits is so you don't get a voltage drop when the A/C, etc. comes on.
Cdc, simply calling something a farce does not make it so.

The lights in any given room in my home dim for a moment whenever the air conditioner comes on. Even though the AirC is on it's own seperate circuit from the lights. AirC compressors/fans require substantial current. As does my 18amp tablesaw motor which is also known to dim lights.

I don't know much about electrical, but I believe each of the two phases/legs in your service panel has a copper bus in which all circuit leads are connected to. All the circuits on one leg are out of phase from the opposing leg. The opposing phases/legs are completely seperated thus far. But you still have half of your circuits sharing one phase. But in addition it is likely that your neutral bus is shared by both phases/legs and perhaps some to most or all of your ground.

The point being that there's an awful lot of sharing going on in the service panel even for so-called dedicated circuits.

The dedicated circuit is primarily for two reasons:
1. to maximize current draw for an amplifier as some amps require every bit of power it can get, not to mention an amplifier's anything but constant current draw from taking constant current away from your other compoents. For example: Some time ago, I took my pre/pro off the dedicated 20amp line where my 600 wpc@4ohm amplifier is hooked up. The pre only draws 36 watts of power. No big deal right? Putting the pre on it's own dedicated line caused the dynamic headroom of my amp to just blossom. And this was noticeable at fairly low volumes.

2. To minimize grunge and noise that other appliances, dimmers, blenders, microwaves, and digital sources inject into other runs off the same circuit spreading to your audio equipment which if there is any to be found and there always is will be amplified to some degree.

In summary, a dedicated circuit is not a complete isolator from whatever other junk may be running in the house. But it's as close as most can reasonably get. The only complete isolating strategy would be to have all audio equipment running from a second service panel which itself is connected to the transformer at utility pole outside your home.

Natalie, Perhaps the best response I could provide would be to paraphrase Scot Markwell of The Absolute Sound after they dramatically altered the wiring, circuit breakers, etc. in room 3 at Sea Cliff about a year ago. Scot said something like: "Until now we have never been able to fully evaluate or review a product based on it's true potential. A statement both humbling and frightful."

And if you do the work yourself, your looking at a couple of hundred dollars to install dedicated lines, audio grede outlets, and circuit breakers.

Pretty cheap tweaks, don't you think? If only line conditioners and powercords would be so cheap.

I will throw my hat into the ring here to agree with Stehno, Bob Bundus and the other posters here advocating a look at power. Over the past two years, I have bought absolutely no new equipment, concentrating strictly on isolation/support and power tweaks (primarily power cords and receptacles-I already had what I consider to be a very good line conditioner in terms of the overall configuration of my system.) Even with very low cost equipment, the benefits derived from addressing these power issues are IMMENSE,leading to a tremendous reduction in sibilance and stridency and numerous other benefits in my system, and as Stehno has pointed out, very cost effective in the overall scheme of things. I do not have dedicated lines, but do utilize floated grounds in my system, decent (but not outrageously expensive power cords) and high quality receptacles-absolutely the biggest bang for the $$$ in my opinion). I will say that, unequivocally, you are not hearing what your system, regardless of cost, can do unless you address these issues.

As for Natalie, well, if I can't say anything nice about him, perhaps I should say nothing at all.
People you miss my point. In this persons case. Power is the least of his problems.
Yes if you can put dedicated lines in they are big help.
If you have your system to a high Level and new gear is not going to help much power is important.
But when you have possibly the worst source on the planet nothing the power can do to help.

With the Denon he has he could bhave a dedicated line all the way bck to the power plant and it would not help.

Guys and Girls you are all trying to fix the roof when the foundation is crumbling.
Hey Natalie: There's no mention of Denon in his post. And we're missing you're point? My experience with a very cheap (and I mean VERY cheap) digital source is that it benefits greatly from power tweaks. Here's a thought for you: Power is the true source.
My error.
There is no denying that improved electric quality will improve system induced sibilance, but there is no evidence whatsoever that such upgrades will have any effect upon the sibilance that is already embedded in recordings. Please note that Braab8's listens to "mass produced commercial cd's" which he readily acknowledges is a major part of the problem.
Onhwy61, I do not believe anybody here, especially me, has given any indication whatsoever that improving the electrical would actually remove sibilance previously embedded into a recording.

It's odd that you would insinuate someone would issue a silly statement like that. Especially when several posts above clearly address that exact issue.

BTW, nice system you have there.
Stehno I did not just "simply calling something a farce does not make it so". I gave a reason for my statement.

Further, just look at a circuit panel and you will see there is no electrical isolation between circuits. Or your neighbors refrigerator. The only benefit I can see is distance. Maybe 100 feet from the neighbor helps. But 12 inches between circuit? I doubt it. Any ideas on what an electrician would say?
Does a dedicated circuit reduce power contamination? Probably. But by how much? A couple of percent?
You seem to agree that there is a lot of sharing on the circuit panel. So how much can a dedicated circuit really isolate? Everything is connected together. I don't get it.
Hi Chuck I was skeptical too.
But having read so much here about the benefit I had to try it & they are SO right.
Not completely understanding something doesn't make it worthless; very few of us would even be driving automobiles if that were the case.
Cdc, okay, after you emphatically stated that cleaning the electrical for sonic improvements is a farce, you did state your one reason why.

However, I believe the reason you provided was poor in that 1. it was an abnormal occurance (when something like a light bulb blows) and 2. You spoke only hypothetically even though your light bulb may really have blown. You did not cite one practical experience where cleaning up the electrical would have any positive or negative affects on the sonics of your system.

Correct me if I'm wrong but was it not too long ago and yet even today, some to many claim that audio cables are all the same and make no sonic difference. Some say that about amplifiers too. All amplifiers simply amplify. With your stance on the above I must assume that you are in these camps as well. So are most electricians.

Your stance reminds me of the scientist proving that a bumble bee cannot fly theory. But that's all it is, a theory. Well, the bumble bees are flying and obviously some to many audio enthusiasts are experiencing greater pleasure with their systems than you are with yours.

As for asking an electrician anything along these lines? Unless it's Glen, I'd rather ask the kid at the drive-thru window at McDonald's.

An electrician is not an electrical engineer. And of course neither am I. But I play one in my house and here on audiogon.

I don't get it. 40+ odd posts later, and you guys are still going at it over the AC issue. Don't get me wrong, I do believe, based on experience, that cleaner power can = cleaner transients. And of course, no one can get rid of sibilance embedded in a recording. BUT THIS POOR FELLOW IS LISTENING IN A 26' X 14' UNCARPETED BASEMENT. HE HAS A SEVERE AFFLICTION OF FLUTTER ECHO, A PHENOMENON WHICH ANY PRO SOUND REINFORCEMENT OR STUDIO PROFESSIONAL CAN TELL YOU IS GREATLY EXCITED BY SIBILANTS, MAKING THEM SOUND WILDLY EXAGERATED. Attending to the AC or whatever else is all well and fine, AFTER TAKING CARE OF THE ROOM, FOR THE EMINENTLY SIMPLE REASON THAT HE WON'T BE ABLE TO FULLY BENEFIT FROM, OR MAYBE EVEN HEAR AT ALL, THESE OTHER IMPROVEMENTS IN HIS ROOM AS IT IS. Debate it all you like, but that's the honest truth, Ruth. (IMHO, natch! :-)
Way to go Zaikes!!!!
Funny, I've had conversations with others in large and very live rooms before, unfinished homes, empty cafeterias and church bldg's (well near empty) many times bigger than the 24 x 16 room mentioned above. And I've yet to hear anybody's pronunciation of the 's' sound turn to mush simply because of excited reverb, flutter echo, etc..

I don't know about wildly excited but all audio info becomes somewhat 'excited' in a acoustically untreated live room. Not just the portion resulting in sibilance. Our ears easily make the distinction as to which type of room we're in. The original source information does not change one iota. Only the reverb info. But again our ears most always can easily make that distinction between the original source and the ensuing echo.

I'd be curious to know the names of the 'Pro Sound Reinforcers' and 'Studio Professionals' that Zaikesman consulted regarding this matter.
Stenho, the larger the room past a certain point, the more the delayed soundfield is percieved as a pleasant reverb (in circumstances such as a choir in cathedral), or possibly a discrete echo. It's the delay timing and the number of repeats, among other things, that determines how the soundfield will be perceived, so it isn't a necessarily case of the bigger the room, the worse the effect, at least as far as sibilants go. I don't claim to be an expert (although we have already heard in this thread from one who presumably is - Rives), but I am a musician who has played live in many different spaces and logged a fair amount of studio time, both as a player and a producer, so I have had regular contact with the professionals I mention, in addition to having read books that touch on this subject. The flutter echo will be set up in a room not too large, with parallel hard surfaces and little damping. The short delay time will tend to fold the perceived effect into the initial event, and not be perceived as separate unless one was to stop the music short. You are correct that it will affect all the sounds, not just sibilants, but sibilants are by definition loud transients (which is why they will distort a mic preamp before throat tones, causing pops or hisses which are indicative of clipping), and these will appear to the listener to 'jump out' and smear more noticeably than non-transient sounds. Another factor is that in a typical, more damped environment, it's the higher frequency sounds that are most absorbed, recreating the intended balance of the sound mix, which was made in a damped mixing studio. When replayed in an undamped space, the parts of the music containing proportionally larger HF content (such as transients) will become exagerated in balance. As far as the example of unfurnished homes goes (which of course may contain the right sized rooms to compare with Braab8's problem), I am in these frequently as part of my work, and I have to disagree - I find conversational intelligibility to be greatly affected by such an environment. [I'll even give you a recorded musical example analogous to what I'm talking about: Play (if you have it) the The Beatles' version of Carl Perkins' "Everybody's Tryin' To Be My Baby"; an artificial tape-delay flutter echo has been applied to George Harrison's vocal track, and listen to what happens to the sibilant 'T's and 'S's as he sings the title line in the choruses.] Again, I stress that I am not trying to cast doubt on anything said above in this thread, but just to point out that in all probability those other potential culprits will be having a lot of their possible effects swamped by that of this room in its current state. In other words, had Braab8's system been set up in a carpeted furnished living room instead, we probably wouldn't be having this debate right now.
Where to begin?? Well first I don't think anyone would argue that siblance can be caused from poor (on sometimes purposely done--as Zaikesman points out) source material. What can you do about this--nothing. Siblance can also be caused by poor source components (or D/A conversion). Siblance can be caused by poor power that affects one or more of your components. However, in this case, it seems clear that the majority of the problem and the first place to attack it is the room. After that, you may begin to attack the other areas, but it's not going to do much good until you get the big problem fixed first.

Stehno makes an interesting point about how we perceive sound. We have done a lot of research in psycho acoustics and it's a very interesting topic. Not many do this type of work and it's not often published since there is little funding on it. We are exploring new avenues in this area and are finding that perception is dominant in listening environments over steady state measurements, but fortunately the 2 do correlate.

As Stehno states, we know when we are in a church or empty space and compensate for that. That is psychoacoustics, and he is right. The human ear has the ability to distiguish reflected tones past 35 milliseconds or so as separate from the original tone. When the reflection arrives at the ear within 35 milliseconds we can not distinguish it (for the most part) and integrate it as part of the original tone. These short time reflections add to ambiance and general spaciousness of the soundstage. The longer the reverberation times the larger the space. The louder the reverberation the emptier the space. People could walk into a space blindfolded and have someone talk to them and could give a rough estimate of the size of the space and whether it was empty with hard surfaces or not.

Now, that being said, our hearing compensation is that to tune out those later reflections past 35 milliseconds (and much longer in large spaces) and we attribute that to the noise floor. Peter D'Antonio of RPG has done a very interesting auralization of this. He has done it for many buildings, but for one it was an entry way into an office building or hotel I believe. The auralization has several voices speaking in the background and then one that is louder--speaking to you. Without room treatment the intelligibility of that speaker is very poor as it is masked by all the other voices reverberation around you, but once the room is treated the intelligibility goes way up. This might seem very obvious, but it makes an important point. Long time reflections must be attenuated or they impede on the intelligibility of the original sounds being produced. This directly translates to music, but is even more important, because we are listening critically to details including very low level and short timing cues. When reverberations of other sounds are lasting too long, they are masking those details. The reverberations longer than say 50 to 60 milliseconds will come across as sibilance.
While its true that the human ear can percieve/distinguish between the original and reflected energy the two become interrelated in different ways. A sound wave will bounce around a room an average 60 times (RT-60) before becoming inaudible (as Rives said). HIS ROOM (Braab8) is probably more like 70 to 90 times before becoming inaudible. These reverbrant sound waves bouncing around the room will do two hideous things 1) it places a certain amount of "strain" on the brain trying to decipher between the original and reflected signal(a lessening enjoyment of the musical experience) and 2) the sound waves can then crash into each other, reflected waves crashing into the original waves. This can cancel detail so that the original signal doesn't make it from the speaker to your ears unaltered. This is the summation/peaks and cancellations/nulls called Phase distortion as it pertains to room acoustics.
"Long time reflections must be attenuated or they impede on the intelligibility of the original sounds being produced" (Rives)
It happens in more deceptive ways in the higher frequencies since its not simply a matter of calculating room nodes which pertain to the lower frequencies (e.g. their wavelengths being of direct significant proportion to the room). To throw on a 3) point--regardless of how flat the speakers freq. response may be, the reflected envergy can easily become colored/unbalanced based on how the room absorbs certain freq. and reflects others and its overall dimensions. High frequencies get colored up too. I know I'm regurgitating a little now. (Lastly, I find AC conditioning to be junk in most respects. There's some foundation to it, but not enough to deserve anywhere near the level of attention it gets in the marketplace--especially compared to room treatment products.)
Correction on RT=reverberation time