Room matters

More clarification:

If you wander through these threads, you will find a fair bit of evidence that the purist signal path to which I referred in my post is a "primary point" of the hobby for a fair number of 'philes. I understand the rewards of that philosophy, too, even if optimal in-room FR performance isn't among them.

My reference to the "purists" was all by way of responding to the post which posed the question (cynically?) "So room correction technology from TacT/Lyngdorf technology will improve...?"

Note that I answered "Yes!" and then attributed DRC's lack of popularity with the A'gon crowd to the "purist" conflict. I do believe that this is the commercial reality behind (judging by the virtual systems listed here) the low acceptance of DRC among 'gon members. High tech solutions just don't seem to be entirely satisfying to many 'goners.

My current "mix 'n match" approach allows me to put one foot in each camp. I enjoy the benefits of high tech DRC where I find it critical to my enjoyment of music (i.e. the bass range) and use a more typical 'phile approach where I find that those tech solutions are less important. My trend line, however, has been one of (grudging) incremental adaptation. Dark side, here I come...

Whew! Hope that 'splains my position.

Marty

B:

Shadorne wrote: ".......... in theory there is no "purity" reason that DRC cannot be used throughout, however, from an acoustics perspective the ultra LF frequencies (below about 100 Hz) is the only area where DRC can effectively correct specific frequency related room modal effects. "

Agreed except for the frequency. From measurements, the upper limit of useful correction of standing waves and modes was defined by Schroeder as the point where still higher frequencies began to interact on a purely statistical basis. Above this threshold, one can best use a wider band "tone" control if room acoustics are poor. Of course, it is in this upper band that room treatments are practical, both physically and economically, for all serious listeners.

This creates a problem for us since applying correction only to the subwoofer (usually crossed over in the sub-100Hz range) leaves the bottom 2-3 octaves of the main speakers uncorrected and, imho, the problems here are more audible than those in the subwoofer range. Meridian's use of correction in the sub-300Hz range on all channels (optional and modifiable) is a great solution and one that should be an option on all other room EQ systems.

Kal

Meridian's use of correction in the sub-300Hz range on all channels (optional and modifiable) is a great solution and one that should be an option on all other room EQ systems.

My choice of 100 Hz may be a bit low and as you correctly point out - a lot of problems occur between 100 Hz and 300 Hz and, I might add, even further on up as far as about 600 Hz, as the sound goes from omnidirectional (bass) to directional (Lower midrange) and during this transistion the sound is affected at various frequencies by floor and ceiling and side walls until the sound becomes mostly of a forward direction (and the room becomes much less of a problem).

Roy Allison and many others are well aware of this problem with virtualy every free-standing speaker. However, this well known fact is hardly mentioned by the majority of speaker manufacturers these days...despite the fact that professional acousticans continue to take into account these very real acoustical problems in pro studio designs.

I decided to find out what was going on with loudspeakers and room interaction. I'd had a hint of it while doing some papers at AR. There was an unexplained phenomenon—nobody could tell me why it happened: a suckout in the middle bass range in almost every loudspeaker, almost every room transmission curve that we measured. That got my curiosity aroused. I wanted to find out what was causing it.

This transition zone from 100 to 600 Hz is often the most problematic. This is why studios tend to either

1) Use small monitors in near field close to the listener and away from walls/boundaries.
2) Use large main monitors that are built into a wall - a soffit mount

"My choice of 100 Hz may be a bit low and as you correctly point out - a lot of problems occur between 100 Hz and 300 Hz and, I might add, even further on up as far as about 600 Hz, as the sound goes from omnidirectional (bass) to directional (Lower midrange) and during this transistion the sound is affected at various frequencies by floor and ceiling and side walls until the sound becomes mostly of a forward direction (and the room becomes much less of a problem). "

I do not think this is true as stated. As the frequencies rise and pass through multiple reflections, their interaction becomes evenly distributed in space and their latency allows the listener to distinguish them from the direct sound. However, they still affect the soundfield and the decay of sounds but, fortunately, they are relatively easy to deal with. Acoustical treatments, absorption and diffusion, will do.

It is only below the critical frequency that spatial issues dominate.

Kal

Kal,

I may not have been clear enough or I oversimplified things too much but I can confirm we are in complete agreement.

It is only below the critical frequency that spatial issues dominate.

I very much agree with that and for the sake of a "critical frequency" Meridian's choice of 300 Hz is fair enough as a ball park number.

Here is an article which is based on Olsen's work that shows how a mere "baffle" can have some interesting effects. From this is follows that the effect of baffles and therefore room boundary surfaces can actually affect response over a "range" of critical frequencies - depending on the specific situation - leading to suckouts or peaks in what are sometimes broad frequency ranges.