Certified THX Technician

I think the point is being missed here... that sub placement, along with room treatment, seating position etc are keys to having smooth bass response for the listener...NOT how good the sub is etc ...The best sub in the world, with perfect frequency response, will still cause problems in any room if not placed properly, and the room treated properly etc ....THX Certified gear means it was manufactured to meet rigorous engineering requirements and will perform up to THX standards at Reference levels with minimal distortion etc ... The only reason most people think it is a marketing tool is because they really don't know anything about it (either did I before I was certified). Yes, there is some gear that will hold up to THX engineering and performance specs that did not attempt to pass THX certification, but most won't because they were not built and engineered from the ground up in the first place to meet the THX performance standards. THX actually works with the manufacturers to build their products. Most of the specs are just very good engineering and design principles, but usually are not adhered to by manufacturers due to their own beliefs and due to manufacturing costs. However, many products that are brought in for testing, expecting to pass due to the "greatness" of the product, simply cannot meet the standards when push comes to shove and they do not pass the certification tests. It's up to them at that point to further engineer the product to meet the requirements or to simply sell it as is.

And it is not THX Certified ...and for good reason .... I will try to address this in my other thread on Subwoofers and proper placement.

\ I was wondering the same thing...... It entails spending some cash and taking a 3 day course on THX, all their technologies, how and why they work etc....a lot of it is hands on calibration, testing etc...and a lot of it is theory and calculations ...people on the course range from home theater installers who want to learn how to do things a "better" way, manufacturing engineers from speaker and receiver companies, sales guys ...you name it .... then you have to write a test and pass with a certain grade to become certified. Then you have to re-write the test every 2 years or so to keep your certification current and valid.

The left sub then should go in the middle of that entire wall, including the back room ...the standing waves first dip will be in the middle of that wall, and that is also where your first row is roughly ....then put the other sub across from it on the right wall, slightly ahead of center. You can then try moving the sub on the right wall to exact center and across from the other one to see which provides smoother response on that side. Non square or rectangular rooms are hard to control the bass properly. You don't need a wall behind you subs...they should be out at least a 6-12" from the wall....this helps reduce the Boundary Gain (buildup of frequencies on the wall...artificially boosting the signal) . I'll get back to you more on this tomorrow and with proper height for your surrounds etc ....also key is to make sure your SPL is the same from all speakers in the centre of the two rows of seats.

Yes, but the subs should be exactly in the center ...the look a little more towards the rear (I know it's only a rough diagram). Is the red line your curtain and does the actual room extend to the back behind it? if that left wall is actually longer and the signal passes through the curtain to the back that will affect the placement and sound as well.

Just a couple observations here ...I just started a new thread on subwoofer placement ... 1. Place your subs in the middle of each side wall across from each other....directly in the middle of the length of the side walls, one on each side. You could do front and back as well, but your would have to put the rear sub into the wall since you have seats there. THX recommended spec for 2 subs is opposite each other on opposing walls in the center of the wall. Face the drivers inwards towards the center of the room. 2. Your surround speaker placements are backwards. You should have your RS-42's at the sides, with the null between the two rows of seats and the 2 RB-51's on the back wall for the rear's, 30 degrees each off center. This is also THX recommended spec. Surrounds should be bi/dipole speakers and rear's should be direct radiating (front firing). I can explain this in much more detail with the how's and why's if you like by email. But trust me, you should reverse your surround speaker placements. Your setup is very similar to mine ...what is the height of your surrounds (side and rear) ? I will also let you know what height they should each be at.

This is a new thread on proper subwoofer placement according to THX standards. Some of the info in here will get pretty in depth, however, see the "6 spots to put a single subwoofer" to help you out. I will also mention dual sub, and quad sub configurations.

Gonna start a new thread on Subwoofer placement based on THX standards.....made some adjustments to my numbers in my above posts after referencing my notes .... Please direct any sub questions to the new Sub thread. Thx

The sub's driver should face the listening location, as do the speakers. if the sub is on the side wall, it's driver will face inward towards the room even though your mains will face perpendicular to that ..... See my previous post above on the 6 spots to put your sub ...I just checked my training notes and made some adjustments. If you move your sub into one of these positions it will help with the standing waves and even out the sub response. even if you have to move it a foot over, it will make a difference.

Please direct questions to the Ask a THX Technician post ..... we are clogging up Steve's original post and getting off topic (which is partly my own fault).. I love to educate, and can take criticism as well ....I'm just here to make your gear sound it's best!

What I meant was if you cannot put your sub on the front wall with the mains and center, and you have to put it on the side wall...if you choose to put it at 1/3 or 1/4 the length of the wall, put it on the part of the wall that is closest to the front wall ...the side of the wall, not the side of the sub. Sorry for the confusion. The sub's driver, if front firing, should face you no matter where you put it ...same direction as your speakers do. Hope that clears things up. And I realize everybody does not have a dedicated room etc ...all I'm saying is here are the principles so that you can try to apply them to your space. The more you can adhere to the standards, the better your sound will be. Even a cheapo two speaker stereo system can sound better by applying the standards, toeing in the speakers towards the listening position, placing at proper height, proper sound levels etc ...all the THX standards can be applied to any type of system to make it sound it's best. I haven't even begun to dig into Room treatment..things you can do to eliminate echoes, reflections ...where to put bookcases, what kind of seating, flooring and materials are best etc to make your system sound better..... I'll save that for another day : )

To help clarify .... Best Spot to Put Your Subwoofer (single) 1st Choice - Front wall - 1/2 way (center) 2nd Choice - Front wall - 1/4 or 3/4 along length of wall 3rd Choice - Front wall - 1/6 or 5/6 along length of wall 4th Choice - Side wall - 1/2 way (center) 5th Choice - Side wall - 1/4 or 3/4 along length of wall (on side nearest front wall) 6th Choice - Side wall - 1/6 or 5/6 along length of wall (on side nearest front wall) This provides the first 6 spots to try and place your sub based on the first three modal harmonic frequencies which will help provide smoother bass response. One of these should work in almost all situations.

bigdaddy...I hear exactly what you are saying and that is true. when people ask me "where should I put my sub" ...well, I tell them, but that may be where their tv sits etc and all their gear ...you still have to work within the environment you are given. So that is why the 2nd and 3rd positions (1/4 of the way or 1/6 of the way along the front wall) work well as a second choice....it puts the sub usually beside the gear, away from the corner, and still helps with the 2nd or 3rd octave frequencies. Like I said before, you CAN stick it anywhere....it's just that anywhere is not the best spot for it. There is always somewhere better that it could go which will hopefully help out with the sound AND the aesthetics. The reason THX states to put the screen so close is because to truly have the home theater experience, similar to an actual Theater screen, the screen horizontally should take up 40 degrees or less of your forward view (20 degree from center to each side). So from where you are sitting , if your corners in front of you are at roughly 40-45 degree angles, the screen should be almost half the width of the wall. "This provides the greatest combination of visual impact with sharp detail". Watching a 52" HD LCD from 20 ft back, although clear, hardly puts you into the action or gives you that theater experience. Again, there are calculations based on SD and HD specs and visual acuity (what the eye can actually make out at a certain distance) to figure out seating distance and screen size. Also, screen height is also calculated, so that the viewer should not have to look up more than 15 degrees to see the top of the screen. This makes your neck and eyes more relaxed for extended viewing etc. Most TV's will never meet this spec though. You would have to sit 2-3ft infront of a 32" TV to get the desired affect or 6ft infront of a 65" TV. So again you have to make due. The main idea though is to have the image take up a large percentage of your vision to wrap you up in the picture and what is happening. The bigger the better. With Projectors , it works out perfectly. And also with computer monitors, as the larger 22 and 24 models are now out, you can achieve this as well sitting at a desk. THX home theater specs are just guidelines and best practices all based on sound engineering and design principles to help maximize the theater experience at home. But you have to do what you can in your space as well. That is why whether there are 10 changes or 1 change you can make to your setup, there is always something you can do to make it technically better, performing and sounding better, and more enjoyable. You wouldn't beleive the installs I've seen, that are tens of thousands of dollars, and the speakers or screen is totally in the wrong spot. Now, to somebody going for looks, it looks great and they don't care about the sound at all as long as they can hear it. But to an audiophile, it won't sound great or the best it can and the gear should have never been put there in the first place. So you have to cater to the client and design it best for their needs and wants since after all, it is their system and they have to be happy with it.

It is Optimal placement and it has nothing to do with the seating or how far you are from the sub. It has to do with the sub, the room, and standing waves. Here is a brief explanation of why. Standing waves are caused by the room dimensions. Unless you are using resonators and bass traps to reduce these unwanted frequencies in the room, sub placement is key to providing smoother bass response. The seating should ideally be placed in the middle of the waveform of the modal frequencies (and there are exact calculations to find where that is). Usually you have a little play with the seating. Even moving them a foot or two in the proper direction can make a big difference in the bass response at those seats. You can't always move the seats though, as you mentioned, but you place the sub at the proper spot to help reduce the affect of the buildup of frequencies where the seats are. Keep in mind most of these frequencies are below 200Hz. The room generates these unwanted standing waves regardless of sub placement. Each dimension (Length, Width, and Height) has a particular harmonic frequency at different octaves that will have an affect on the room as the sound waves reflect off the walls, ceiling, floor etc. The idea is to reduce the affect of these standing waves by proper sub placement, and moving the seats to a better spot if possible so you don't feel this affect. Without doing tons of calculations, by placing the sub halfway along the wall, it reduces the first octave standing wave frequency's pressure level, whatever that frequency may be based on the room dimensions. 1/4 distance reduces the second octave, 1/6 the third etc ...The first octave is the strongest one over the others, although the 2nd or 3rd octave may be the one that is producing the same standing wave as another wall, creating a large build up of that frequency which would then require putting the sub at 1/4 distance along the wall etc to reduce the peak affects of that frequency. So unless you do the calcs to know the exact frequencies and where to place the sub, rule of thumb is to put it in the middle as it will reduce the first modal frequency (the strongest one) and help smooth out the bass response no matter what. Then you do a bass test (hammer the crap out of the sub with specific trouble frequency) and walk around the room to see where the buildup of frequencies are. You will feel a high pressure zone, making your head worble etc ..then as you move a foot or so away, it will disappear etc....you want to find that spot in between the high and low pressure to put your seating ...ensuring you will get smooth bass response. Now to do this you need a tone generator and need to do the calcs to get the frequencies that will cause havoc in the room. The sub is non-directional and isn't easily localized so it doesn't matter where you put it to get bass. But it does matter where you SHOULD put it to get smooth and accurate bass. Perfect scenario is 4 subs, one in the middle of each wall. 8 is even better - 2 on each wall in opposite phase to each other - eliminating almost all standing waves. Even 2, 1 in the middle of the front wall, and 1 in the middle of a side wall, will help reduce 2 major frequency build ups and provide smoother bass response. Some installs have subs mounted halfway up a wall or in the ceiling etc ... but there are hard engineering principles behind why it SHOULD go in certain spots, whether you agree with them or not. The proof is in the pudding ...when they are properly placed, you can run tests and sit in the sweet spot and have perfect, smooth bass response at extreme volume levels ..not loud, rumbly, shake your head bass (which is NOT good bass response). Subwoofer placement and calibration is one of the biggest misconceptions in Home Theater. To properly place a sub, it requires a good understanding of the science behind it and why it works. I should really open another Post on this topic, as it is quite indepth and requires knowledge of standing waves, modal frequencies and how the room affects bass response. You will actually get better bass response with more smaller subwoofers, than with fewer larger ones. I am just trying to educate people in order to help them out. I know some people that don't care, and just throw the sub in the corner and crank it up. And that is their right to do so. But in a $100,000 custom theater, you don't just guess and throw the sub somewhere because it's aesthetically pleasing or convenient. You place it where it should go to provide the best bass response for that room. And to do this requires proper calculations and testing. I hope this wasn't too technical, and helps you to understand the theory behind proper sub placement.

are you pumping the video out as well to a TV or projector and want the surround sound to fill the room? or are you just sitting watching it on your laptop and want surround sound around you in front of your laptop?

Couple things here ...If you only have 1 sub, it should be place in the center of the wall at the front where your LCR speakers are. Or you could move it 1/4 or 1/6 along the front wall...my other post Ask a THX Technician explains this in full ...no need to put the sub at your seat. Speaker Levels...thing of crucial importance here is that all speakers (LCR, Surrounds, Rear Surrounds, Sub) all provide the same SPL at the main listening position. So from your seat (sweet spot), pink noise or sound level tests should give the same SPL reading (75db min..85db for THX Reference) from all speakers. If you don't want to crank your system up that high, use the loudest you would ever have it at and make sure each speaker is the same level as the sound goes around the room. Best quick way to test this, and phase, is to run the THX Optimizer from any Pixar or Lucasfilm DVD ....this will quickly tell you where your problems are. Most people don't have the proper test disks to run the necessary tests, so this is a good substitute. But first, verify the settings with your receiver's internal pink noise channel level calibration as well. The auto Cal should have taken care of this nicely though, but this is where you can manually adjust it with a SPL meter to make sure it's exact from each speaker. Now personal preference plays into this as well ...if you like your dialog louder, then turn up the level on the center ...if you like the surround field louder, do the same to those ...proper reproduction of the source recorded material though requires that all speakers be at the same level. But tweak it as you like. Just keep in mind you are then altering what the director intended. Sub phase should be normal. Reverse is for multiple subs to help cancel out the standing waves (room modes) etc ... In regards to your RF-62, the Surrounds (L, R, Rear) should be at approx. 2m (6') or 2' above the listeners ear level. Surround speakers are not meant to be blasing into your ears or head directly and should not be easily localized (you can tell where it came from). Normally, you would have 2 monopole front firing bookshelf speakers (like RB-51's) as the rear speakers, in a 6.1 or 7.1 configuration. If you can, put these towers on boxes to raise them up. The ambient sound will then blend much better with your reg surrounds and create the proper ambient sound field. Turning up the channel level on these will provide more sound if that is what you prefer, but keep in mind, you are only meant to hear what is on that rear surround track....usually reciever's will create this from a reg 5.1 soundtrack just to have something there, as most films do not have rear surround tracks. Often, you don't hear anything in the surrounds, because nothing is there. Many people don't like this so they try to crank it up, spread it around etc to have constant sound around them all the time. But this is not what was intended with the source material. Proper speaker placement and levels will reproduce what you should be hearing. Again, you can tweak as you like, but again are going against the source material's intentions.

Is the 15' wall the rear? How far back is the rear wall from the listening position and how wide is the listening position (all seating) in relation to the width of the back wall/room?

4 RS-3ii's for your rear's? How large is that back wall? 100 ft? You should only need 2 at most for an average large room. However.... Only the side surrounds should be bi-pole or di-pole, like the RS-3ii's....rear speakers should be front firing monopole speakers, like the RB-51. You don't need to disperse the rear sound field as you do on the sides ...tests have shown that it is much harder to localize sound from the rear than from the sides, which is why even just one rear (6.1 config) often will do the trick. Don't forget ...the dedicated rear surround track has very minimal content in most cases...most films barely have an actual single rear track let alone a dual rear track ...so not many speakers are needed to reproduce the sound that gets sent back there. And you would only use 2 surrounds on each side if you had 2 rows of seating or more. So, if you are going with a full 7.1 setup, use 2 RB-51's across the back, approx. 2ft above the listeners ear position or 2m from the floor, spaced 1-2ft apart for THX ASA config, and 60 degrees apart (30 degrees from center on each side) for discrete 7.1 config. In a 6.1 setup, just use 1 RB-51 at the same height in the center of the wall. What are the dimensions of your room?

Thanks ...I always liked the phrase "Klipschome" ....

These are all computer speaker systems correct? Are you actually using them for a computer and desk? or as a poor man's home theatre system for a small room (10 x 10)? And if you are watching your HD movies on your PC , I'm assuming you have a 5.1 compatible audio card with optical or digital coax out?

Hello there, and welcome! There is plenty to do here, related to Klipsch. Speaking of Klipsch, do you have a preference.Thanks Are you referring to speaker preference for the Klipsch line itself or which brands I prefer in general?

I am new to the Forum but will gladly answer any questions people have on setup and calibration of Home Theater based on THX specification and quidelines.

Some speakers operate more efficiently on a lower setting ...so if you switch to 6, you need to make sure your speakers can also operate at that setting as well. But leaving things at 8 works for most people. Usually only higher end speakers will operate at 6 or 4 so then you can use that setting. For most people 8 is the default and works well with most equipment.

Steve...welcome to the Forums ... I will try to help out here as much as I can without making your brain hurt. Properly calibrating your receiver and room has many complex calculations to do it right. I just have a few comments and will answer your questions as well the best I can. You mention that you have RF-62's for surrounds ...which surrounds are you using them for? the rear? Reason I ask is due to proper placement of the speakers. Only your front speakers (LCR) should be Floors or similar as you want the speakers firing at approx. ear height in the seated position, or if they are higher up, aimed down to the seated position. The Surrounds (side) and Rear Surrounds should NOT be at ear level, firing directly into your head. These are meant to provide ambient sound and effects and should be mounted approx. 2m from the floor if seated position is on the floor. If the surrounds were placed in a room where most listeners are standing, then the surrounds would be mounted slightly higher (by a few feet) to make up the difference in ear height from seated to standing position. Ideally, you would use 2 RS-42 bi-pole (di-pole is better) for the Surrounds (side), with the null (point between the speakers) pointing at the seated position and mounted at 2m height. This will provide the best surround ambient soundfield and works with one or multiple rows of seating. For the Rear Surrounds, you would use 1 or 2 regular bookshelf RB-10 or RB-51 front firing speakers. Spacing if using 2 depends on the type of content and receiver modes you have available. Also, where is your center mounted in relation to the top of your RF-82s? You want to make sure that the center channel is within approx. 2 ft vertically of the L and R speakers. All 3 would ideally have their drivers at the same height. This allows for more accurate reproduction of localization and pans across the front sound field. Now, to your questions. 1. The HF and LF rows of speaker connectors are for Bi-wiring your speakers so that the lower frequencies and higher frequencies can be connected from seperate sources/amps etc or disconnected altogether (if you wanted to remove the lower frequencies from your speakers and only use the tweeters etc....There is a metal clip that should be mounted under these 2 terminals to connect them together and transfer the signal from your amp so that both High and Low frequencies are sent to the proper drivers in your speaker. So unless you are bi-wiring, it should make no difference whatsoever which set of terminals you connect your speaker wire to. 2. Most speakers and recievers are 8 Ohm ...you want to make sure that your reciever and speakers work on the same voltage etc ...if you send too much current to the speakers, you can fry internal components, corrode cheap and thin speaker wire etc ...The impedance is to make sure that the speaker is getting proper current to operate. There are testers and ways to check this, however unless you specifically need to adjust it due to a problem, I wouldn't worry about it too much. Key is to make sure you don't have 4 Ohm speakers running off an 8 Ohm amp or vice versa and this can cause overload to circuits in the amp and provide inefficient power to drive the speakers. 3. You should always use the autocalibration of your receiver as a starting point to manually tweaking your gear. The autocalibration will do a great job (some companies do it better than others - Denon, Pioneer, Yamaha etc) of setting up your channel levels, latency, and EQ based on your room settings. 9 times out of 10 this will save you hours of manual calibration and provide a good starting point to further adjust each speaker / channel for your room. But even if you just run the autocalibration, your sound will be greatly improved compared to out of the box settings. Key Notes on Autocalibration - Make sure the mic is placed at the central seating position as that is where it will take it's readings from and create the best sound field. Other seating areas of the room will not sound as good, especially off axis, but some recievers (Denon) have multiple mic readings and will adjust the sound for multiple seating positions, which is ideal. In a proper manual calibration, I would do readings with a multiplexer from each seated position and calibrate the EQ etc to have the best sound across all listening positions. This requires a lot of work and time and is not ideal or cost effective for most people. Also,make sure you run the AutoCal at Full 0db volume or Reference level of your reciever/amp. If this is too loud for your environment (it usually will be) or you will not be listening close to those levels, then running the Autocal at the loudest level in which you would set your reciever will give you a more accurate calibration for that volume level and will not require re-adjustment due to lowering the volume. In Short - run the Auto Calibration. 4. Ah ..the sub ... This is the biggest misconception in Home Theatre. The old rule of thumb was "just stick it in a corner"....this is however, the WORST spot to put a subwoofer. Now I will try and keep this short and sweet, but proper sub placement is based on something called Room Modes. Basically, the dimensions of any room, based on length, width, and height, produce waves of frequencies that depending on the distance (there is a calculation to determine all this) will cause boosted frequencies. Similar to what the other posted mentioned about being in the "dip or peak" of a wave, this is what creates bad bass response. Many time your seats are positioned in the peak, creating a boosted , worbly, make something rattle bass signal. Or they are in the dip, where the frequency is lowest, and you don't feel any bass at all. However, moving just a few feet can put you in the proper area of the wave, and provide the best bass response. The Room Mode, or frequencies for your room that will tend to be boosted by the room, can be toned down by proper placement of the subwoofer to eliminate the octave of the wave that will cause this boosted frequency to occur. I will get to phase in a moment. Rule of Thumb - if you are only using 1 Subwoofer, keep it in the front sound field (LCR wall) and put it in the center of the wall. Corners allow base frequencies to build up and un-naturally boost the base (Boundary Gain). Similar to how if you talk with the back of your head on a wall...as you move out from the wall, you will notice your voice loses a bit of base response. As you backup towards the wall again, the bass increases. This is Boundary Gain, and you do not want it because it is boosting the bass frequencies from what the reference level should be. The only time this is a good thing, is if you are using a passive, underpowered sub ...by putting it in a corner will help it get more "oomph". But louder is not better. Moving it to 2/3rds the length of the wall or 1/4 will also help. But never in the corner. Also, the crossover frequency of your reciever should be 80Hz, and the crossover settings on the sub won't matter if you disable it on the sub. Crossover settings on the sub are usually for passive connections that take the lower frequencies from the front L and R speaker feeds (speaker terminals on the back of the sub) and output them through the sub at the set frequency. If you are using a LFE connection to your sub then the internal cross over should be disabled anyways, and it's getting what the reciever is sending according to it's settings. When the sub is in passive mode and the setting is set to say 120Hz, you will hear things you should not coming out of the sub...even dialog at times. These higher settings are usually to make up for speakers that cannot reproduce lower frequencies properly or have proper mid-range and low-range woofers, so by setting the sub higher, these lower frequencies are allowed to be reproduced by the sub. Keep in mind sub's produce 2 types of sounds - low frequency effects and all frequencies below the frequency setting. This is where speaker type in the Reciever setup is so important. If you select Small (which you always should) the Reciever sends all frequencies lower than 80Hz to the subwoofer, along with specific LFE signals. If you select Large speakers, it assumes that the speakers subwoofers built in to produce those low frequencies, and only sends the LFE signals to your sub, allowing your speakers to produce the low bass frequencies them selves. Test this setting out and you will notice a big change in the sound. Now if you have killer floor towers and want to use their built in sub (if they go down to 25-35Hz) then go ahead, but in most cases, regardless of the size and type of your speakers, you will always select Small for the speaker type, allowing the low frequencies to be sent to the subwoofer. Putting the sub in the center of the wall reduces the boosted gain of the first octave modal frequency that your room is producing, allowing for smoother base response. Moving the sub to 1/4 or 1/6 etc along the wall will affect the 2nd and 3rd octave frequencies. So depending on which frequency of all walls is going to cause the largest boost, that is where you put the sub. In multi-sub (THX recommends at least 2) installs, the sub along each wall is placed in the correct spot to reduce the modal frequency that will cause the biggest boost. Phase - now this IS short and sweet. Basically, the Phase on a sub is used when the frequency is colliding with another frequency so that they can cancel each other out. So in the description above, where frequencies in the room are colliding and boosting the level of the signal, if you were to use 2 subs, fired at each other, in opposite phase from each other, then the frequency would cancel each other out and you would get smooth response. So in a perfect world, subs along each wall, firing at a sub on the opposite wall, in opposite phase would provide perfectly smooth bass response. The modal frequencies would cancel each other out no matter which wall or octave was causing the issue. In short - Subs that have Phase adjustments are better as they are configured for multi sub placement to eliminate these boosted frequencies. Same as dipole speakers do, so the they fire in opposite phase to the closest speaker, providing more accurate and smooth frequency response. If only 1 sub is present, it doesn't matter if you have it at 0 or 180. It only matters if you have 2 (unless your towers have built in subs ...then you may want to flip the phase. Please feel free to ask any more questions. I hope I didn't confuse you or ramble on too much. I could go on for days about this stuff. As you can see, there are many calculations involved to figuring out the best placement of a sub, and for location and height of all the speakers etc ..as well as screen size, distance etc ... I hope I was able to provide the answers you require and feel free to ask anything else. The more educated people are the better.