Klipsch heritage speakers to be raised to ear level?

[egoquaero]

@Chris A

Hi Chris!

How would you comment this video?

 

[glens]

I'm not Chris, do you want to know what I think?

 

That's 5 minutes I'll never get back!

 

A lot of assertions casually made, some of which would have extended the video many-fold were I present when he made it because I'd taken him to task.

[Chris A]

One of the plagues of the 21st century seems to be the "watch the YouTube video and believe what (anyone) says", because it's so easy for anyone to put a video up.  I'd also remind those that use YouTube for their information gathering--that Sturgeon's Law applies to things like YouTube videos (perhaps especially so).  One should always write down the implied, tacit assumptions in any video or article like that one.  Here are a few tacit assumptions that seem to come to mind:

 

1) loudspeakers produce "bad" vibrations

2) loudspeakers have internal resonances inside their bass bins and inside their closed-back drivers, etc.

3) loudspeakers/listening rooms/listening positions within the room suffer from "floor bounce" and that's made worse if the loudspeaker is on the floor.

4) "fields" of low frequency energy exist in the room, and these "fields" are better if their decoupled from the room boundaries.

 

Of these few tacit assumptions that I've enumerated above (out of many more that the presenter was apparently throwing around), only nos. 2 (internal cabinet resonances) and 3 (floor bounce) are issues that are ones that are actually worth talking about. 

 

Loudspeakers don't produce "bad vibrations", and the structure-borne vibrations conducted away from the loudspeaker if it is coupled stiffly to the room boundaries must go somewhere for us to hear them with our ears or to feel tactilely.  If the loudspeaker boxes are vibrating, don't you want to attenuate those vibrations by setting the loudspeakers on the floor to couple to the room boundaries, instead of the resonances building up in the bass box itself to be re-radiated into the air?  Better to rest the loudspeakers on something that absorbs the reaction forces of the bass drivers and moving air inside the boxes. 

 

Where do these "bad vibrations" go? They dissipate into the room boundaries.  In order for them to be conducted away from the loudspeakers and re-radiated into the room for your ears to hear, some form of conduction and re-radiation has to be provided that is extremely efficient so as not to dissipate the structure-borne vibrations back into the air instead into heat (which is where almost all of it goes).  What are those mechanisms that do that?  Almost nothing does that...and any that does is extremely attenuated so as not to be heard above the direct arrival energy from the loudspeakers and the in-air room reflections.

 

What do we do about floor bounce?  Carpet works really well (even though the loudspeakers may be sitting directly on the hard floor itself).  If the acoustic waves in air from the loudspeaker, bouncing off the floor and reaching the listener's ears are not controlled, we get something known as "early reflections".  This is a phenomenon of how we hear (psychoacoustics) that leads us to want to control floor bounce (or early reflections from anything close to the loudspeakers in-room)...not "bad vibrations".  Nothing about the act of setting the loudspeaker on the floor is important to that process.

 

What do we do about internal box resonances?  Answer: better engineering of the loudspeakers to suppress them through stiffness/compliance means, geometry of the box and drivers, and through filling the internals of the box with sound absorption material.  Putting your loudspeakers on the floor doesn't affect what's going on inside the loudspeaker bass bin boxes.  Same thing is true for closed-back drivers.

 

There are no mysterious "fields" of acoustic energy in the room at low frequencies, only low frequency acoustic waves in air whose wavelengths that are longer in air than the room is in length, width, or height.  That means that the geometry of the room boundaries becomes important at some low frequency break point, and the pattern of standing wave intensities vs. frequency is a function of where you put the loudspeakers, the listening position, and the room boundaries--but it's not controlled by "setting your loudspeaker on the floor" (i.e., coupling). The 1/4 wavelength cancellations and 1/2 wavelength resonances in the room are all controlled through geometry--distances, angles of the walls to each other, distance of the drivers from the walls, and "coupling" (a little more involved in terms of its subject matter, but NOT mysterious).

 

I gave up teaching graduate engineering courses a few years ago because the mode of teaching that the university was constrained to use (streamed video capture of lectures after the fact)...ostensibly because of student unwillingness to be present in the same room and the same time as the lecture, and the willingness of companies to pay universities to give their employees as graduate students instead of making the students do what they should be doing, which is showing up in person.  It's just like the YouTube video whereby the students are not able to immediately ask questions and get answers as they view the presentations--but then they don't have to drive and spend the time face-to-face.  That's how one learns from lectures, i.e., being in the room with the instructor--asking questions as they arise, along with demonstrations (which can be extremely difficult to show for many areas of engineering and physics).  It's those two required areas that are so extremely important for useful learning--real learning.    Otherwise, you get the mush that you find in the video--along with lots of confused thinking on what's important and what's not, and what the tacit assumptions are that are being inducted into the discussion.

 

Chris