Squeezing the most performance out of your Home Theater (part 1) (1 Viewer)

[Mike Knapp]

I have been working on this essay for many months. Putting it away when I didnt feel like dealing with it and then after the events in September I put it on a kind of hiatus. I decided it would be good for me to finish it up and post it now, in the spirit of helping others get what they can from their systems. There are three parts...Audio, Video and Accessories. Look for the other two parts soon, they are still being worked on. I really hope this helps some of you derive the same pleasure I get from this hobby,
Mike Knapp
After being involved in this hobby for many years I have come up with quite a few tweaks that you can perform on your system to get the maximum performance from it. Many of them are just common sense and many of them are free or so cheap they may as well be.
Some of them will cost some money and you may need to decide if the benefits warrant the expenditure in your situation. So here goes….How to squeeze the best performance from your Home Theater System.
First lets look at the audio portion. In order to have a good surround sound field you must first have a good two-channel sound-field. If your two-channel front sound-field is flat sounding, so will be your film sound-field. Developing a good stereo sound is not an easy task, but the benefits of your labor will bear sweet fruit even in home theater use.
TIPS: Basic Speaker placement
1) Keep your speakers as far away from other surfaces as possible. Don’t place them right next to the wall or the TV or right beside a sofa. Let them have their space. The space behind the speaker is almost as important as the space in front of it. Keep your speakers off the back wall as much as you can get away with and make sure the fronts of the speakers are well in front of the display device. (disregard for FPTV’s with perf screens)
2) NEVER place your speakers inside an entertainment center cabinet. This is a common occurrence, especially with the center channel speaker. Avoid this at all costs. If you absolutely must do this be sure to treat the cavity in which the speaker rests with acoustic materials such as foam or fiber-fill.
3) If your center channel speaker sits atop your TV (very common) be sure it is angled down toward the seating position and make sure the front of the speaker is beyond the front of the TV as far as possible. To achieve the proper angle you might use a rubber wedge shaped doorstop and some blu-tac (sticky rubber sold at art supply stores) to make sure the speaker stays in place or there are some commercially available stands to aid you in this.
4) Make sure your speakers match. They should all be identical but that is often not possible. If you cant use the exact same speakers for your surround system, try getting them all from the same manufacturer with the same drivers in them.
5) Eliminate first order reflections as best you can. Sit in your listening position and have a friend walk down the side-walls of your room with a mirror against the wall at your eye level. When you can see your speaker, that is the place on the wall that needs to be treated to reduce first order reflections.
TIPS: Sub-woofers
1) There will be some contention in this area but what I will describe is what I have used and what has worked for me. First thing is to make sure the sub is the same db level as the other speakers. This will yield you the most accurate results. You may prefer more bass than this will afford you but try this first for a while before goosing the LFE. A well-balanced sound system will sound smoother and more natural.
2) Placement…this is a can of worms to say the least. What has worked for me is the “reverse engineering” method. Place the sub-woofer in your seating position (remove the chair/couch) and put on a thumping soundtrack of some kind or play a sub-woofer test tone loop. Walk around the room and place your head at about the same height it will be when you are listening to your system. When the bass sounds the smoothest you have found the best location for the sub in your room. It may not be where you can actually put the sub though so you may need to compromise, but you now know where it should go. If this position is not feasible, try the front room corners.
3) I would suggest a separate sub for the LFE and the other speakers. This is a controversial position. I have found that a single sub, handling all the channels (including the LFE) simply does not sound as good. I run three subs in my system. One for the LFE, one for the mains and one for the surrounds…I do route the center bass to the LFE sub. This gives me smooth articulate bass and allows me to have a more boom oriented sub (ported) on my LFE where it is needed and keep the boom out of my mains where it messes with my music. Your results may vary.
4) EQ that thing. Your room can make a great sub sound terrible. Certain frequencies can be boosted as much as 20db by your room! You can tame some of this with an EQ (equalizer). The room is still going to effect the bass but you can lessen the impact with a well-adjusted equalizer on the sub-woofer.
Balance…that is the key to natural sound. Too much treble and your head will hurt, too much low end and you may feel nauseous. Use an SPL (sound pressure level) meter to properly balance your speaker levels. Follow the instructions on the tone disc or use the internal tone generator in your electronics. Either way, it is critical that all your speakers (including the sub) run at the same SPL for you to realize a properly balanced sound-field.
TIPS: Rounding out the sound
The golden triangle…seating position.
There are many equations for this. I will tell you of the one I found gave me the best results. Measure the distance between the left and right main speakers. Place a piece of masking tape on the floor in the center of that measurement. Now measure out from that piece of tape the distance you measured between the speakers…that is where you should sit. If your seating position is fixed, do this in reverse to find the optimum speaker locations. You can get great results in other locations as well and this is not the ONLY way to do this, it is just a way that works for me.
Place your speakers on an arc centered on the seating position. Take a string and have a friend hold it to his forehead while he sits in your listening position. Extend the string to your left speaker front. Now walk across the front of the room with the string and you will find where the other speakers should be placed. Often, it is not possible to place a speaker in its optimum place, then we must use the time delay settings on our equipment to compensate for speakers that are closer to us or farther away. What you will find though is that if you start at the center speaker sitting atop the TV with the string, that the left and right speakers will indeed be in front of the display. This is great ammunition to use with the spouse that insists that the speakers be flush with the TV.
Place tweeters at ear height. If this is not an option be sure to get it as close as possible or angle the speaker toward ear height at the listening position. The surrounds may be the exception to this rule. Check with the speaker manufacturer to discern the suggested position for the surround speakers.
You can aim your speakers by using a simple laser pointer available at K-Mart and other stores. Affix the laser to the top of your speaker using Blu-Tac. Make sure it is centered on your tweeter and parallel to the sides of the speaker cabinet. Sit a piece of cardboard in your listening position with a circle drawn on it so that the circle represents your head (height is important here). You could also use a friend but be sure he closes his eyes before turning the laser on. Now turn on the laser and point the light outside the circle on the side that the speaker is on (left of the circle for the right speaker etc). Repeat for the other speaker and know that the center speaker should hit the circle dead center. The three lasers should converge about 2’ behind your sitting position at ear height. This method works great for me.
Isolate your speakers. If they are on the floor, use some spikes or rubber feet. If they are on stands use some blu-tac between the speaker and the stand and between the stand and the floor. Rubber padding will help this as well. Isolating the speaker from what it sits on will do some wonders for the sound.
Wiring:
I will make this brief. I have found that wires (all wires, including power cords) will indeed make a difference in the sound of your system. Spend what you feel comfortable with and buy products with a liberal return policy in case you don’t realize any improvement.
Next, we will look at the video!
Mike

 

[Joe Cole]

Mike,
Great essay!
I am still trying to implement some of these suggestions my self. Most notable the center channel set up. I have the same TV as you do and am using a Martin Logan Logos center speaker. I do have it pointed at the listening area but am nervous about hanging it over the TV since it weights in at 65lbs or so. I am looking for a stand to raise it off of the TV some. Have you seen any that might work?
Because of my room shape problems I am still experimenting in a limited way the placement of my rears. They are OK right now sitting behind the sitting area facing the TV.
The subs(3) are another source of anxiety. I have not tried the method you and others suggest yet. I don't have the crossovers to run the subs as you are. All 3 are off the .1 out.
Would the new ICBM help in this area? More money for interconnects and I use balanced for l/r.
This is truly a hobby, constantly challenging and fun.

I have even made my own powercords. I would like to build a DIY sub like yours or similar.
Happy listening/viewing.

 

[Mike Knapp]

I hung my center over the TV in its proper configuration (vertical) and it weighs about 40-50 lbs. As long as you hit a ceiling joist with your mount system you should be fine.

I don't have the crossovers to run the subs as you are.

Sure you do. All you need are three subs. You run the speaker wires from the amps into the sub and then out to the speakers. Then you use the x-over in the sub to determine what frequencies the speakers get. (most commercial subs will allow this to be done) Easy as pie! Be sure to set the speakers to LARGE after you are done. Repeat the process for the rears. Leave the center in the "small" mode so its bass is routed to the LFE sub.
Mike

 

[KrisK]

Mike, Do you have all 3 subs in the same location?

Thx, Kris

 

[Mike Knapp]

No I dont. The sub for the mains and the sub for the LFE are very close to one another. The sub for the surrounds is in the back corner of the room. I have a large room, 30X28 feet, which allows me to get the rear sub far away from the others. Most people wont be able to do this. I would suggest that you need to experiment with placement. You may find the need to place them all in the same location.

Mike

 

[John Garcia]

How about isolating the speaker from whatever it is sitting on? In particular, floor standing speakers should be isolated from the floor, and bookshelf speakers from stands or whatever supports them, even if the stands are also isolated from the floor. Unwanted vibration transfer can color speaker response. I have my sub sitting on foam feet, isolating it from direct contact with the floor.

I don't agree about speakers being pointed directly at the listening position, on an "arc". This varies depending on the roomm and to each their own.

 

[Mike Knapp]

John,

Thanks for the reminder...I added that one to my original post.

Using the arc was to get all the speakers the same distance from the listener. I toe mine in but many people do not. If they are placed on the arc, they will be the same distance from the listener. Toe in is optional...but it works for me.

Mike

 

[Todd Hochard]

Excellent stuff, Mike. Except maybe the wire bit.

Isolate your speakers. If they are on the floor, use some spikes or rubber feet. If they are on stands use some blu-tac between the speaker and the stand and between the stand and the floor. Rubber padding will help this as well. Isolating the speaker from what it sits on will do some wonders for the sound.

The spikes are a good idea, but it's not about isolating. In fact, they have the opposite effect- the spikes physically couple the speaker box to whatever it sits on.
This is a good thing. Imagine the most obvious scenario- a front-firing subwoofer. Every time the sub fires, the cone excursion places an equal and opposite force on the basket, which of course, is connected to the box. Therefore, the box will tend to move in the opposite direction of the cone. The spikes allow the box to be firmly attached to the floor. This, in turn, substantially increases the "effective mass" of the enclosure. As such, the cone must now generate a substantially larger force to get the box to move.
The net effect is that more of the energy is used to push air (the whole point of a speaker), and less pushing/vibrating the cabinet.
Thus, the more effectively you can couple the speaker box to the floor, the better the speaker can do its job. Spikes are much better than rubber feet. Highly flexible foam defeats the purpose, as it will absorb the vibrational energy, which can (will) dampen the output. If you must use rubber, use high durometer (stiff) stuff. Additionally, placing weight on the speaker cabinet (not in, as changes to internal volume are generally not good) can have a beneficial effect.
Todd
P.S. I also find the arc/toe-in thing works best for me.

 

[Mike Knapp]

Thanks for the clarification Todd.

When are you gonna get over to Tampa for dinner and a movie?

Mike

 

[Sean Conklin]

I also use the arc/2 ft.convergence toe-in/golden triangle method. I also built a stand for the center speaker, it sits just below and in front of the TV, and is angled precisely at the sweet spot.

In my small HT room (12x12)I have found that the 2 ft. convergence toe in to have the best imaging and soundfield.

And because the square room is not a subwoofers best friend, I have found that 2/5 placement just to the right of the Left Main and 6 inches from the front wall, with the port facing the wall yields the flattest response.(bottom firing).

And for the surrounds I went with the DD 5.1 suggestion of mounting them about 3 ft. above and pointed directly at the listener. I have read for 5.1 you want them pointed directly at you(because they are discreet), and for Pro Logic, you want them pointed at each other(because they are mono).

I believe Mike is right on with these guidelines.

Thanks Mike!

 

[NickSo]

Wow, great tips Mike. I will try some of them that dont require alot of moving, since my HT is also my dad's office and he wont let me move much stuff... And also i dont have the $ for some of the tweaks... but great tweaks though. Get a mod to archive this. I dont wanna save it as ill probably delete it by mistake. :p

 

[John Garcia]

I consider a well built speaker to have little cabinet resonance. When I built my last sub, I added an extra piece of wood to make the panel where the sub was mounted thicker than the rest of the cabinet. Even I was impressed.

Most of the spikes I've seen, appear to isolate, not transmit. They are also called "isolation" or "dampers" right on the packaging. My stands all have spikes, and the speakers are fixed to the tops via something similar to blu-tac. Todd's explaination sounds reasonable enough though, as most of the commercially available "feet" I've seen are high durometer rubber. I don't think the idea is to have the resonance transmitted though.

I have carpet in the livingroom, and after much adjustment of my sub, I found it to sound best when not directly contacting the floor.

I feel experimentation with all of Mike's recommendations are most definitely a great way to find out what works for a given situation. Every room and setup is different.

(I use a slight toe for my mains, but not for my surrounds also.)

 

[Brian OK]

Very good job with your tutorial about setup.

I'm sure you could have elaborated more, but opted for a concise read. You may receive adaptations, corrections and "to take it a step further", but you hit it right on the head as it is.

I'm sure this 3 part series will be a benefit to all.

Thanks, Mike.

BOK

 

[Howard_S]

Thanks for the post. This should be a sticky so all newbies can read.
Got a few questions and comments.
You mentioned giving speakers some room. Does this apply to the sides of speakers as well? So you shouldn't have the speaker backed up to a wall but you shouldn't have a wall right beside your front speakers right?
Fronts infront of TV. How much? If you place your center on top of your tv then your fronts won't be beside the center speaker. Is that okay?
Subs. Should all subs be the same thing? I have a Paradigm PS1200 and thinking of getting the Servo 15. Should I hook up the PS1200 to the mains and the Servo 15 to the receiver output?
For those who have their HT in a place that was not designed for a home theatre. Open space w/o doors and without drywalls or soundproofing What can they do? If the fronts and TVs are backed up against the walls should one hang up rugs or something? Renovation is obviously not an option for most so should one try installing a door? Hang up stuff on the walls?
Coaches. Are coaches that are in an L shape formation bad? As the back of the sofa may block off sound from one of the surrounds?
I suppose you'll be talking about surrounds in Part 2? dipole rear centers? Sorry so many questions.

 

[Brett DiMichele]

Mike,
Good thread..
I also use the triangle in my setup. My mains are toed
in 40 degrees each and toed up at an angle (higher in the
front) so that the dispesion of the tweeter meets with your
ears at the sweet spot. The Center Channel which is almost
6' off the ground (what can I say, it's a HUGE TV) is also
toed down 30 degrees. All of these angles have been checked
via the trusty laser method and all speaker dispersion hits
right where it should. The only speakers I have not accurately
aimed are my L/R Surround. They sit at celing level and I
use a pair of B-Tech Swivel/Tilt brackets and depending on
what I am listening to (movies or music) I some times go
over and reposition them to either direct radiate or bounce
off the side walls (reflecting)
John,
I would like to think that my mains are "good" speakers..
The cabinents weigh in at 65 pounds each. And the build in
10" subs push nearly 100 decibels at 32Hz. I find that using
a good pair of spikes is critical. I have a fairly thick
pile carpet and when the cabinents sat directly on the carpet
not only were they dangerously unstable but the low frequency
also seemed to suffer (muddy) as the carpet was absorbing
much of the energy that the subs produce to push the air.
I added a pair of billet aluminum NHT spikes and made sure
that they fully pierced the carpet (applied weight on top of
the speaker cabinents for weeks) and now they are to the
point where they are definatly piercing the plywood floor
substrate. And the bass is better than it ever was when they
just floated on the carpet's surface. Low Freq's need to
travel through solids.. Imapairing that is defeating the
purpose of the sub IMHO. It would be like mounting a pair
of tactile transducers under your sofa with bengee cords.
The whole point is to get the sound AND the vibration
Again this is a great thread.. I am sure much useful info
will come from this.. (well with exception to the wires
related part)
:star: :star: :star: :star: :star:

 

[Mike Knapp]

Brian,
The idea is to generate discussion. If I answered all the questions in the essay, what would we have to talk about?
If anyone has suggestions lets hear them. The purpose is to be helpful, lets get some newbies headed down the right track this holiday season!
Mike

 

[Mike Knapp]

Coaches. Are coaches that are in an L shape formation bad?

You talking about Steve Spurrier? He uses a shotgun formation I think. I know you mean couches (just having some fun) The formation isnt the thing to concern yourself with...the proximity to the speakers is.
Enjoy!
Mike

 

[Saurav]

Just a comment regarding speaker isolation vs. coupling. I too believe that spikes couple more closely to the floor, rather than isolate, and the idea is as stated, to transmit cabinet vibrations to the floor, which is essentially the same thing as providing a greater effective mass to reduce cabinet vibrations.
This is usually a good thing. However, there are certain situations where it might be better to actually isolate the speaker from its support. Example 1 - speakers sitting on a bookshelf. In such a case, you do not want cabinet vibrations being transmitted to the bookshelf. So, you use soft compliant rubber feet, or partially inflated bicycle inner tubes, or something similar. Example 2 - a room with a very springy wooden floor - if the resonant frequency of that floor is within the range of what your speaker produces (which is quite likely with a subwoofer), you probably do not want to be transmitting vibrations down to that floor. Again, soft compliant feet which decouple/isolate will be better. On the other hand, if you have something like a concrete floor, you almost always want to use spikes to couple your speakers to the floor, because a heavy dense floor will absorb any vibrations sent into it.
This becomes even more important if you're playing vinyl, because floor-borne vibrations can have a drastic effect on a turntable's performance. This is because a phono cartridge is trying to track very tiny undulations in the groove, and any external vibration added to it gets directly converted into sound. In fact, sometimes you can actually set up a feedback situation, where the speaker's vibrations go through the floor to the cartridge, and then get amplified and played back through the speaker, and so on. The results aren't pretty

 

[Tom S]

Thanks Mike for the insight.

I wonder what your opinion would be on the LFE on my system?

A Denon 3300, a pair of def Tech powered towers, and a "boomy" Velodyne sub.

The 3300 only has on subwoofer output, but also has L and R preouts. Right now I have the Denon setup on "large", left and right (speaker level only), and plug LFE into the subwoofer. Would you suggest spliting the LFE to each speaker and the sub? Doesn't setting the speaker set up to large, push some LFE into the mains?

Tom.

P.S. Can you recommen a good dvd player? My Panny A310 is on it's last legs.

 

[Brett DiMichele]

Saurav,
You are right on the money as usual I should have included
the examples you spoke of, when not to use direct coupled
cabinents in leiu of isolated cabinents. Very good post and
very good information.
That whole feedback situation, Not pretty at all