system/room equalized flat from 20 to 20k cps--is yours?

Spending alone will not get you what you are striving for. Systems with flat performance are non existant. It will take PROFESSIONAL extras, electronics, room measurements and sound treatments to get you there. What have you done besides reading reviews and buying what is purported  to be the best to get the holly grail of sound? 
  Ken Fritz

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Systems equalized flat to 20k will be irritating but flat to 20hz will be exhilarating and response below 20hz will be addictive. My digital rig is flat to 20hz and down 6db at 15hz with a combination of brute servo force of 6 8" woofers and a REL Gibralter G2. The room is generously treated with the new ASC Isotherm tube traps and wall treatments. 

Plumbing the bass depths has some tremendous rewards but also some drawbacks. The rewards include a massive soundstage and musical attack but it also exposes recording/mastering issues that go unnoticed on most other systems. Rush "Moving Pictures" is a great example. Limelight sounds great on a system that is flat to around 40hz but it is not so good with one that has response to 20hz as the bass drum and toms are extremely exaggerated and take away the gestalt of the music.

However, there are other discs that expose just what extended response can benefit the musical event and in these cases, it is all worth it!
Hello to all of you who took the time and trouble to post.  This is a subject that has been very dear to my ears for many decades.  Because I did not want to put the cart before the horse, I began to design the construction of my audio room first.  With the help of many industry experts and the book entitled "Master Handbook of Acoustics," by F. Alton Everest, I was able to construct a room that was then measured by a company that took ETF measurements at various times during the construction and again when it was almost completed.  With their help and that of my local oriental rug dealer, and a furniture company in colonial Williamsburg that specialized in 17th and 18th century furniture, my room was finally complete in a satisfactory manner to my ears. 

To automobile high performance car enthusiasts, Mr. A and Mr. B, each buy the car of their dreams, a McLaren Ford.  Mr. A takes delivery and immediately goes to a test track, where he spent a better part of a day ringing out every last bit of performance that car was capable of. 

Mr. B upon taking delivery of his McLaren, lives in the countryside.  He takes his car to the interstate and illegally runs his car as fast as he could get away with.  He then drives back home on the winding country roads and puts the car through another challenging test.  Unfortunately for him, he was unable to go to a test track but he did the best he could with his high performance car. 

Both Mr. A and Mr. B are happy with their purchase and understand the circumstances under which their cars were able to perform. 

The $330,000 top of the line Wilson Audio system has published specifications of 20 to 30,000 CPS plus or minus 2DB on the top end.  Furthermore, they include the phrase "room dependant performance". 

It is the desire of all top notch loudspeaker manufacturers to select the appropriate drivers and design the appropriate crossover network to get their system to perform as flat as possible from 20 to 20,000 CPS.  The selected drivers are generally measured separately with a 1 meter time base measurement that eliminates room reflections and gives an accurate response curve for that driver.  After all the drivers are chosen for any particular system, it then becomes necessary to incorporate them in a complete system with a crossover network that will integrate them at the best possible frequencies and slopes.  The designer can further tweak the peaks and valeys of each driver in their operating range with additional filters, etc. that will help flatten them out.  Once the drivers are incorporated into a cabinet, the response will further be affected by the internal volume each driver is operating in along with sharp or rolled cabinet edges that may enduce further frequency anomalies to that response curve.  A final test measurement will then be taken in an anechoic chamber that will allow the loudspeaker to produce a frequency band with virtually no reflective interference from a room in which it may be used. 

We have all heard speaker systems costing hundreds of thousands of dollars at audio fests around the country in which the speakers are playing in a room the size of someones kitchen.  The speakers are giants performing in a closet-like atmosphere.  We do not visit these audio shows to hear how good the equipment sounds, but to evaluate its price point and visual aesthetics.  I am sure that many times a person who buys a $300,000 loudspeaker gets it home and tells himself "I wish my room would be a little bit better so that I could bring out every ounce of performance from my new speakers, but unfortunately, I am a married man with a couple kids, ugh, and must live within certain limitations." 

If you live in a home that has a room large enough and with good acoustics to put a smile on your face, you are one of the lucky few. 

Wilson Audio designs their high end system with adjustments that enable you to properly time align all of the drivers to a specific listening spot.  If you happen to be off either the horizontal or vertical axis of the system, such as when you have an audio group over, very few people will be able to hear the system at its best.  Having said that, a couple of beers will equalize things out quite nicely.  If you listen to such a system at an off axis location, things such as rugs on the floor, furniture in the room, human bodies, etc. will tend to absorb some frequencies, the highs more than the lows.  If you are fortunate enough to have a unit such as the Cello Audio Palete or a George Massenberg GML9500, you will probably not be able to roll off the highs at 7, 8, 9, 10K at any desired slope.  In the old days, we had audio preamplifiers that had bass, treble and maybe a presence control to tailor the system to our personal likes. 

Playing back a recording of any musical selection will be compromised from the original by the mastering engineer.  In order to tailor the music to a novices ear that will entice he or she to purchase that particular recording, the following probably takes place:  RIAA equalization when the record is cut, turntable arm and cartridge selection, electronic reproduction equipment feeding a loudspeaker system in one particular room or another.  All of the previous deviations from the live experience is why it is always best to listen to live music, if you can.  The greatest influence on the final sound will be one such as mine; at 79 years of age, I cannot hear a 10K pure tone through my or any system.  I believe my ears begin to roll off at maybe 6 or 7K but its an effect I can do nothing about.    I must rely on the ears and equipment of the mastering engineer to tailor performances I would never have an opportunity to hear live.  While various mastering engineers may accentuate various parts of the mix differently, I do not concern myself with anything but just being happy with what I have. 

The loudspeakers I built make my ears happy as clams.  Before embarking on the construction of these monsters, I conferred with Vance Dickason and Joe D'Appolito at a CES show quite some time ago.  I asked for their opinion on my choices of drivers, crossover points, and system design.  Even with their opinions, I realized that when I was finished, it would not be feasable to make any physical changes in the loudspeakers themselves.  Lucky for me, I picked fantastic drivers and voiced them in the line source that ended up being very pleasing to my ears.  The electronics I chose all come from Krell, whose founder propagated his "one man, one vision" philosophy coincided with my thoughts and, therefore, after selecting Krell equipment, I looked no further. 

When I had both the room and the system finished, I had ETF measurements taken again and employed the services of Carol Miller at Soundstage.  After taking measurements of my system, it was suggested that I include a number of Dolby Lake LM44 A to D to A processors in the electronics chain.  Carol used his equipment and the newly inserted LM44s to adjust the system response in room average positions to be reasonably flat from 20 to 20K hz.  There is a subtle difference when I hit the in circuit/out of circuit button on the Lakes and do not really notice enough of a difference to cause me to worry. 

Some of my audio friends have come over and listen to music familiar to them.  If it is jazz or anything with a good deal of high frequency information, a few of them have said "Ken, sounds a little bright to me."  That may be because I have a 9 foot high row of ribbon tweeters producing everything above 6500 hz.  If all but a few at ear level, when seated, which is where most tweeters are placed, on either a point source or a line array systems are designed, the sound in my system would probably not be so bright.  I chose a line source design knowing full well the difference I would get with that design as compared to what I got out of my Electrovoice Patrician I was using years ago. 

CONCLUSION:  I have always been a person who thinks out everything he could before acting upon my wishes.  I avail myself of as much of the commercially available information pertaining to that situation before I act on any particular project.  If I made mistakes in the past, they were minor and did not really affect my degree of satisfaction with the final outcome.  I look forward to further comments from those of you who were kind enough to post and also look forward to those comments that might be posted in the future. 

Happy listening, Ken
Not me.

But I may play with something like miniDSP at some point when I have time to spare, but things sound great already so no great rush.  I do pay a lot of attention to room acoustics otherwise though  and always strive to  take that into account because that is always a big factor for how things sound.
I've equalized the bass from 20hz to 100hz +-1db.  I eventually decided it sounded too weird and gave up on it.  I built a couple dozen bass traps and all sorts of absorbing panels.  I don't think equalizing the bass to flat is a good idea unless the room is already very good.  It requires too much manipulation of the signal and seems to kill transients.  After a couple of decades of messing around with audio the strongest opinions I have about room problems and eq are that the best main speakers should have big woofers but not a low -3db point.  Let the frequency response drop off naturally instead of trying to get it as low as possible using ports, passive radiators, or any other method.  It is very unlikely that the main speakers will have decent deep bass response at the same place that is ideal for the rest of the frequency spectrum.  Having them flat to 20hz is a terrible idea.  Fill in any deep bass deficiencies with subs.  The other thing is to start with a decent room.  If construction is too solid bass can't escape and it's extremely difficult to deal with.  You're better off with a wood frame house and drywall - typical modern flimsy construction that lets a lot of bass energy escape through the walls.