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In Reply to: RE: Why Kill Valuable Musical Information/ Dynamics of Sound-Waves at the First-Reflection Point? posted by Dryginger2 on June 21, 2015 at 17:14:56
These reflections create comb filtering, thereby coloring the sound. With some training and practice one can learn to hear the reflections and how the sound changes when the reflections are removed. Some people, especially blind people, can "hear" the walls. They are listening to the sonic reflections of the sound of their feet.
If you are hearing the walls of your room, then you won't be perceiving a potential sound stage that's larger than your room, thereby missing out on some of the magic when playing great recordings on a well set up system.
Tony Lauck
"Diversity is the law of nature; no two entities in this universe are uniform." - P.R. Sarkar
Follow Ups:
Tony,
It's interesting how the almost immediate reflection of off-axis sound-waves from these panels on either side causes their arrival at the listening position with insufficient delay to cause 'comb-filtering'. This is proved by the marked increase in the purity of sound and, of course, all the other improvements flow from the additional volume of musical information. My next project is to reflect sound-waves coming from speaker-ports away from the walls behind as a preliminary test indicate that this also likely leads to sound improvement. So I agree about walls.
DG
> > It's interesting how the almost immediate reflection of off-axis sound-waves from these panels on either side causes their arrival at the listening position with insufficient delay to cause 'comb-filtering'. This is proved by the marked increase in the purity of sound and, of course, all the other improvements flow from the additional volume of musical information.
Comb filtering will occur when delayed versions of the sound waves interfere (constructively and destructively) with the original wave.
The wavelengths of audible sound range from about 17 meters (20Hz) to 17mm (20kHz)
Unless I am very much mistaken, the distance between your reflective boards is within that range, so comb filtering will occur, despite the "proof" that you provide.
In fact, the distance from the speakers to the panels I would guess to be say 50cm, meaning that you get comb filtering around about 700Hz which is right in the middle of the midrange.
Beautox,
You are absolutely right and I was clearly misled by the remarkable increase in improvement already achieved. Have turned a pair of panels upside down and placed each right next to either side of one speaker on its maple block and that doubled the amplification of its music again. Difficult to tell how that will translate in terms of total sound quality improvement until listening after having doing the job permanently to both speakers. Will report back then. Many thanks for your thoughtful input!
DG
That would tend to make speakers sound impressive, and I suspect that is what is going on.
regards,
reub
Reuben,
Obviously the Vienna Acoustic Mozart Grands in question are 'coil' rather than 'horn' speakers with which you entitled your response. The principle adjective that I would use to describe music with complete musical information and dynamics is 'engaging' of which we never tire rather than 'impressive' which quickly loses its allure to stylized tedium and ultimately fatigue. It's the three dimensionality, energy and small sound details that take us to the recording event in my view and using (rather than discarding) the extra musical information + dynamics from off-axis sound-waves provides a critical edge in capturing this realism. The logic of fast-reflection over absorption is compelling and hearing the revealing sound improvement settles the matter...
DG
Maybe you just like your midrange comb-filtered?
Beautox,
Regrettably the music with panels in immediate proximity to the speakers does not sound as natural to my ears as when they are mounted on rounds at treble the reflecting distance. Despite the expense of now putting them back the way they were, am grateful to have tested this variant.
Certainly do have a preference for the quality improvements from using all the musical information and dynamics available from the speakers at what sounds to me to be such a marginal loss of tone from frequency cancellation that I cannot audibly detect it when making a direct comparison. However do accept it must be present on some level for the technical reasons that you have provided. We are fortunate to have the benefit of your technical expertise.
DG
Beautox,
At a reflection distance of 4" I suspect the sacrifice in tone will shrink close to inaudible as the improvements in sound quality attributable to including ~40% more musical information and dynamics expand even further. Perfect tone with much diminished content will be perfect for television/ poor recordings while enhanced content and stronger dynamics will be best to reveal good recordings at very little tonal cost. Will see. Am grateful to you for your advice.
DG
I abhor front ported speakers. While you may not be aware, the air moving out of the port id moving diametrically opposite oy the woofe, and it affects not the bass but the transitional area between the woofer and the driver above in frequency.
On some speakers like a Harbeth I simply place a large post'em not over the port.
For the larger bass outputs the paper will flap open and close for the smaller amplitude signal. Cheap and effective and you hear a increase in midrange detail.
I guess I should get off my butt and make something out of felt, it'll probably look and perform better.
I've actually cut up paper towel cardboard cores at, say, a 45 degree angle to guide the air coming out of the port to the out board sides of the speaker. Works well, too, although grills become impossible. I guess if you are good with your hands you could build a set of louver, like those JBL tweeters and make a more imposing air wave guide. For woofers, down and out is the key to performance, at least for front firing porrt. On the other hand,for rear firing ports, aiming the port's output stright up seems to extend the bass response...
FWIW and YMMV
"I abhor front ported speakers."
Me too Stu, so I don't use them...
For me ported speakers are a poor compromise compared with "acoustic suspension" styles for home use.
No ports is good ports!
Rick
Stu,
Tried downwards sloping felt over the woofer ports to shield the mid-range port outflow and unfortunately heard sound-quality degradation with my particular speakers. Thank you for the interesting tweak suggestion.
DG
If you don't mind could you tell me more about what you heard?
I have no experience with the Mozarts, so I am simply guessing, but that leads to many issues. I need data.....
Also, Please don't feel I am stalking you you or anything like that. I want to encourage AA readers to experiment on thier own, to exercise their intellect and you and others have juped on the bandwagon rather enthusiastically.
I firmly believe that a pool of knowledge and experiences advances the audio scene much more effectively than the efforts of any one individual.
You certainly exemplify that.
Thank you
Stu
Stu,
A good attorney always ask a question to which they already know the answer:-)
Cupping panels in the immediate vicinity of speakers leads to muffled sound with little clarity and bad tone. Why? I suspect this is because the exiting direct sound-waves crash into those off-axis sound waves just reflected off the nearby panels to create and maintain a large area of turbulence something like 9" in front of the speakers that completely disrupts the correct timing of all their arrival at the listening position. The resulting muddle substantially reduces the clarity and the timing-delays seriously degrade the tone through heavy frequency-cancellation under the renowned 'comb-filtering' effect. In short cupping panels around speakers is like locating an off-axis hub airport and a direct major airport in immediate geographic proximity to each other so that the exiting flights of neither have a turbulent-free departure. Really dumb idea but am glad to have had the opportunity to learn it from costly first-hand testing experience!
Placing downward-sloping felt over the woofer ports to protect the mid-range port outflow diminished the dynamics so that the music sounded noticeably dull.
If more discover the rewards of testing and sharing tweaks, then any single individual would attract less attention because the fun from my perspective is in the cross-fertilization of ideas between us all.
DG
Stu,
Many thanks for the easily-implemented suggestion. My felt woofer-port flaps are now taped in place for testing tomorrow morning. Knew that re-directing the airflow back there was producing an improvement but had as yet done little testing to discover precisely why and how to optimize.
A pair of panels per speaker brings three times the benefit of a single panel on the inside perhaps because two, not only double the dynamics/ musical information but also, supply the added synergy of balanced sound.
DG
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