Now it is said that the air space between the speakers should be kept as empty as possible, and that the audio components should be placed somewhere else in the room.

That is the ideal set up.

Now, lets say that you do not have a choice, and have to place your components between your speakers, what is the maximum height the component stack can be before they begin to compromise acoustics?

Right now my equipment stacks about 28 inches (711mm) between my speakers.


-Lost81

I put a wall between my speakers. Didn't work that well. Note to self: remove wall.

Now it is said that the air space between the speakers should be kept as empty as possible, and that the audio components should be placed somewhere else in the room.

That is the ideal set up.

Now, lets say that you do not have a choice, and have to place your components between your speakers, what is the maximum height the component stack can be before they begin to compromise acoustics?

Right now my equipment stacks about 28 inches (711mm) between my speakers.


-Lost81

While placing the equipment between the speakers "does" lend itself to some reflected sound issues, it also solves some others.

Long interconnects and or long speaker cables are both negatives to consider which make placing the equipment someplace else a "trade off".

The primary problem with placing the equipment between the speakers is the additional reflections it brings with it.

This can be solved or ameliorated by a few different things.

1) First keeping the equipment stack low, by spreading it out between the speakers can be helpful.  Generally the lower the better and since midrange drivers and tweeters are normally higher, the direct angle of incidence is greater and into the carpet before your ears.

2) The second way to combat this reflection, is to place a (temporary) sheet of acoustic foam in front of the equipment when you are listening seriously.  I would suggest at least 3" Wedge Foam (24" x 48" sheet will stand on its own if shaped in a shallow semicircle)

Or you can simply lean the foam up against the equipment at a slight angle.

3) placing the speakers slightly in front of the equipment (as mentioned earlier) will also help, but will not reduce the reflections as much as "blocking and absorbing" them, but used in conjucntion will help.

What has to be realized is that we have direct and indirect sound hitting the reflective equipment faces.  Direct is that which is coming directly from the drivers or speaker's baffle, while "indirect" may bave bounced around the room many times.

The idea between the speakers is to create a "sonic black hole" or cavern where "little to no" sound is reflected or projected toward you at the listening area.

The more successful you are at accomplishing this, the "blacker" the spaces between the sonic image(s) will be, and the more "depth" your soundstage will have.

28 inches sounds to me like close to the maximum allowable if they are well behind the speakers. I use 15-inch tall Sanus EFAV-II at least three feet behind the plane of the speakers and I also recommend a symmetrical environment (as exact as possible) relative to the three walls around the speakers, speakers well away from walls and with different woofer to side-and woofer to front-wall distances and absorption of the first reflection on both sidewalls.

With all due respect, I strongly disagree with the comment about a huge TV just a feet or so behind the plane of the speakers. The fact that this is a common and WAF-forced placement doesn't make it correct. You haven't experienced your speaker's soundstaging potential if that describes your system.

The above is one of the most solid lessons in my lifelong experience in audio.

Example:

I have a In my little 2.1 HT system (HT is a low priority to me).  It consists of a 9 year old 27 inch Sony TV, factory reconditioned Harmon Kardon stereo receiver, 5 year old unremarkable DVD, Hsu VTF-2 sub, and Ascend Acoustics CBM-170's (these are wonderful 2-ways for $330/pair).  The 170's are wall mounted with the TV inbetween on an enclosed cabinet that holds the other components.

I've heard a xylaphone (sp?) stretched out between the speakers and could follow where the particular bar is struck up and down the scale.  When it hit the TV, the image stopped and then came out the other side.  

This setup is really an extreme example of how to do it wrong from an imaging standpoint, but right in terms of short cabling.

My 2 cents:  keep interconnects short, keep components low, and error a bit on the side of longer/heavier gauge speaker cables to improve imaging.

I must respectfully disagree with John on the use of foam in most circumstances. If you have a carpeted room (which is what I see in at least 90%+ of the music rooms here in the South), the use of SONEX is a no-no in almost every conceivable case  . The carpet is already absorbing too much of the high frequencies and adding SONEX just makes it worse. For these cases, a diffuser is a much better alternative. If you have concrete/tile/wood floors, then John is correct and adding SONEX around the equipment as part of a comprehensive room treatment plan is a great idea.
..

 
Hi Julian,
 
Thanks for the agreement, and disagreement, for it gives me the opportunity to further explain, what I think is a misconception many have about "harvesting" or using "reflected" sound and the value of "reflected HF's.

First I have to preface my remarks by saying "ultimatley" the sound that fits your preferences is "the BEST Sound", and no one can argue with that regarding "one's" system.

I should also mention that "room created" sonics can sound remarkably good, and with some systems "preferential" to more accurate representation to what was recorded.
 
It is important to know that all sonic reflections are not one kind, nor are they interpreted by the ear/brain as individual reflections.
 
It is also important to know, that "diffused" sound is also reflected sound that is reflected in a randomly staggered timing pattern and or sometimes angular radiation to produce less of a specific sonic impact than a direct first or second generation reflection.

The advantage (and less offensive nature) of diffused sound is that it does not have a specific source.  
 
But never the less, it is not sound from the original recording, but room altered sound, added/altered by your surroundings.

Then there is the (IMO) misconception that blocking or absorbing the "shorter" frequencies in the front of the room will make it too "dead".
 
I think the common misconception I'm speaking to is that absorbing reflected sound from the "front" portion of the room will in some way "reduce" HF perception (at least I think that is what is being said - correct me if I'm wrong), when I have found that it is the exact opposite.

I think anyone who has ever seriously listened to headphones, has noticed that the clarity, detail, and resolution is second to none.  This is due primarily to the fact that the room and all its "sonic contribution" is taken out of the equation.

I would suggest that my recomendation to use a blocker/absorber for frontal reflections would, in fact, "increase" the perception of HF and MR detail, resolution and 3-D depth in the sweet seat.
 
I used the example recently, of an automobile approaching you with its bright lights on.  If we let the lights assume the role of some rather low dispersion speakers and this event happens during  daylight when we have "much diffused" light all over, the brightness of the headlamps is perceived as much less, than if it happens at night, where, although the lights are shining with the exact same brightness, the eye/brain perception is that they are "much" brighter.
 
The point being that diffused sound (and light) will actually "soften" detail, and resolution, as well as decreasing the amount of depth and blackness", by adding diffused sonic reflection.  I generally call it A sonic fog, but for those who prefer it you might call it a sonic "mist".

Now the truth is, that if we measured the "brightness" of the two events with a light meter, there would probably be a higher reading during the day, but that would not change "our" perception of when the actual "direct light" was the brightest.

Another good example is watching front projection TV in a room that has highly reflective, light colored, walls and ceilings.  The diffused light from the reflections and dispersion from the projector and screen will "light up" the room and "wash out" the detail and resolution of the image and imaging.

Paint those walls with a light absorbing grey color and material and the clarity, detail, contrast and resolution on the screen will improve.

Now this might lead to a discussion of the (my favorite) LEDE (Live End/Dead End) acoustic principles.  Some might ask then why the "live end" is nessessary at all.

I mean if even diffusion is bad, then why would you want "any" use of room sound to create the sonic illusion?

I would suggest that "if" the Live End's room surfaces are good at creating significant "diffusion" then the "sound" perceived from that "indirect" source is "non-descript, or non-defined.  It is simply "AIR", or more clearly, it will sound spaceous and open, without significant spatial cues of direction, frequency, or boundaries.

If we couple this, with distinct, clear and detailed frontal sound, that is not competing with anything but spatial "air" we have some incredibly clear and clean reproduction.

Now, as I started this post, I mentioned that it is really all about preference.  Some will say that there will not be enough HF/MR energy with this set up.  My experience has told me that it is just the opposite.

Some might also say that the room will sound too dead because it doesn't measure well.  My ears tell me different.  I find the lack of "sonic fog/mist" is what was recorded (if it was a live recording/if studio then its up for grabs depending on the producer and engineer)

BUT,....If that is what you like, then it is the best way for you    

This type of understanding is what makes the pursuit interesting.  

I wrote (tongue lightly in cheek) about my "treated room" snobbery, not to long ago, and not 2 weeks later, heard some of the most beautiful sonics in recent memory in a basically "untreated room".

As Denzel Washington said in in "Training Day"

It's all GOOD!

There could be a bit of misunderstanding here, as SSS's between could be interpreted to mean very close to. Whatever the case is, I insist that the most common problem is represented by doug s' (whose ears I respect, by the way) speakers still not being far enough into the room (which in this case also means far from the equipment) for optimum soundstaging. Not bad at all, but perhaps improvable in what appears to be long-wall placement in a biggish room or short-wall placement in a very big room.

One way of having long interconnects and very short speaker cables is by using monoblock amps, of course.

Val

There could be a bit of misunderstanding here, as SSS's between could be interpreted to mean very close to. Whatever the case is, I insist that the most common problem is represented by doug s' (whose ears I respect, by the way)  speakers still not being far enough into the room (which in this case also means far from the equipment) for optimum soundstaging. Not bad at all, but perhaps improvable in what appears to be long-wall placement in a biggish room or short-wall placement in a very big room....

the setup in that room is speakers on the short wall - at ~26x38, it *is* a big room.  as far as the speakers not being far enuff into the room, after a bit of experimentation, i settled on 6' from the back wall as the best distance.  the equipment *is* quite a bit back from the plane of the drivers, and, as mentioned by others, keeping the gear below the bottom of the monitors is also wery helpful...

doug s., yes, i *am* a bit off my rocker!  

doug, 6 feet is more than enough and it is just the perspective that appears to show quite a bit less than that. Hey, I don't doubt what your ears tell you!

Val

yes, the perspective in the foto *does* make it seem a bit less - thus the clarification...

doug s.

For all that are reading this post, I HIGHLY suggest purchasing your own copy of the "Master Handbook of Acoustics" by F. Alton Everest. It is almost 600 pages but reading it cover to cover will literally save you thousands of dollars in the long-run. Implementing even the most basic suggestions covered in it will probably improve most listening environments more than if you doubled the price of your current components    .  More importantly, it will help you weed out a lot of the incorrect information you find on the Internet.

The Internet is full of "hobbyists" that have the best of intentions but unfortunately have an uneducated and myopic view. In most cases, the person realizes they have a problem, fixes the problem to the best of their abilities and knowledge, and then lets everyone know about their miraculous discovery. Unfortunately, I have seen too many cases where the "surgeon" has cut off the head to stop the nosebleed   .  The problem is that other people with nosebleeds follow their lead and before long cutting off your head becomes "the accepted standard".

While everyone's ears and taste are different, scientists have been studying these differences for well over 2000 years. There has been an enormous amount of work done in the last 50 years specifically around room design and optimization as well as human aural perception (both objective and most recently subjective). Studies of general subjective preferences associated with reflection delay, level, and decay have been well published for many years. An example is that a reflection delay of 10ms and level of -15 dB to -1 dB will be viewed as adding spaciousness to the sound. At that same 10ms delay, -1 dB to 5dB will be viewed as broadening the image. Above 5 dB will be viewed as a discreet echo. The goal of any professional designer is to understand all of this (and much, much more), understand the requirements of their client (i.e., is this for a church, mixing studio, recording studio, home playback environment, etc.), and then implement a compromise solution that best meets these requirements.

Luckily there are a few things that just about any reasonably competent audiophile with a calculator, pencil, paper, and a tape measure can do:

1) Determine the modes of your room. You can use this to get you started:  http://arts.ucsc.edu/EMS/Music/tech_background/TE-02/modes/Modes.html

2) Next, and by far the most important thing you can do is determine the absorption/reverb time in your room by frequency. Here is a fantastic reference that will help you do that:  http://www.me.psu.edu/lamancusa/me458/8_rooms.pdf For those that are mathematically challenged, there are also several Sabin Internet calculators that will do this for you but the ones I have tried were definitely not as accurate as when I do it by hand (most do not go to enough detail).

The trick with item 2) is to get the absorption/reverb time at all levels to be roughly the same. If they are NOT the same, you are NOT hearing what the artist intended for you to hear. Suckouts or peaks in the audible frequency range will cause a coloration of the music by offset harmonics/pitch/etc (if you don't believe me, hit any two keys on a piano at the same time with the same force. Next, hit one key harder than the other and see if the two tests sounded the same). Once you have figured out how to get all the reverb times the same, then you can tune the room to your own personal preference. If all you listen to is organ music and you want your living room to sound like your church, an RT60 time of 1.5 seconds might be OK. If all you listen for is vocals and soundstage/broadened imaging are not that important to you, then an RT60 time of .5 seconds might be more your style. For the rooms I design, I typically shoot for a cross frequency RT60 time of .6 sec to .8 sec and so-far the results have been quite good.  

As for Live End/Dead End Rooms, they were a revolutionary concept in the 1970s for recording studio control rooms. However, the problem they were intended to correct was the issue of "initial time delay gap". As such, the operator would be located nearfield to the Dead End so that the first reflection time was as long as possible. The problem is that people who did not understand the science behind it said "hey, if recording studios are dong it, it must be good" and promptly put their listening position on the Live End which meant the worst of both worlds (loss of soundstage and they did not fix the "initial time delay gap" issue that was meant to be addressed). While there may have been an improvement in direct imaging, the imaging is probably not as good as it could be plus they made needless sacrifices to get it. Due to progress in the science of control room design in the last 30 years, I seriously doubt that you will find any high-end studio still using this concept (but you probably will find it in more than your fair share of low-end studios who just can't afford to do things "right").        

OK, back to topic.... in most cases, long interconnects are a bad, bad, bad, bad thing. They are bad because they present a difficult load to the low quality and low voltage opamps in the output of most sources/preamps. They are bad because they force you to use a shielded design which significantly increases capacitance. They are bad because they have increased capacitance regardless of design. They are bad because the longer they are the more chance they have of crossing something (i.e., a power cord or speaker cable) that will electrically couple to them or picking up some other type of interference.

As for me and what I recommend to my customers, all interconnects should be kept to less than 1 meter. I generally try to keep all speaker cables less than 2.5 meters. Generally speaking, the only way to do this is have the equipment between the speakers.

OK. I have spent way too much time on this topic so this will be my last post here. Needless to say, room design and human auditory perception is a VERY complex subject and my rant above barely pierced the tip of the iceberg. For those individuals in/around Austin Texas (or traveling through Austin), feel free to bring over a good bottle of Irish Mead and I will do my best to provide more information than you ever wanted to know . Best of luck and happy listening.      

Julian
www.sedonaskysound.com
"Sound through Science"