Q I have a few questions regarding some of the specifications provided by speaker and amplifier manufacturers. First, on Paradigm's web site, they list most of their speaker models as having a "Maximum input power" and a "Suitable amplifier power". In every case the upper limit of the latter is greater than the former.

Now, I want to upgrade my receiver, which currently delivers 70W to the mains and 15W to the rears. My mains are listed as having 15 -100W
amplifier suitable, 80W max, and my surrounds as 15 - 80W suitable, 50W max, so the amp is well wihin their power handling range.

You have said many times that speaker damage is caused more often by too little clean power than too much power. I am looking at several receivers which are rated to deliver 80 - 110W to all the channels. Will this excess of power damage my smaller rears? If so, then I will probably need new rears. Should I look to upgrade to speakers which are rated to handle power up to 150 - 200W, in case I want to add one of the behemoth power amps like the Sunfire Cinema Grand or Carver AV-705x?

Finally, a question on rated sensitivity. Sensitivity is given as dB/W/M, so it is the dB measured at 1W and at 1 Meter. P=V²/R, so for a speaker whose impedance is 8 ohms, 1 = V²/8, or V = root 8. 10log(root8) is always the same number, regardless of whether the speaker in question is super-efficient or incredibly inefficient. Further, 10log(root8) = 4.5 dB, which is far from the 85-105 dB/W/M that one normally sees. What is wrong with my logic?

A Maximum input power means the limit of power that can be supplied to the speaker without damaging it. Let's say it is 100 watts. A suitable power amplifier might be listed as 50 - 150 watts. An amplifier of 25 watts would not be suitable if the speaker were not very sensitive. If the speaker were more sensitive, a 25 watt amplifier might be listed as suitable. It is just a general guide rather than anything absolute. I once used a 7 watt amplifier to drive some bookshelf speakers that were not very sensitive, and it worked fine. The speaker manufaturer was surprised. There is a little bit of arbitrary thinking that goes into the suitable amplifier specification. A high power amplifier like the Cinema Grand or AV-705 will work very well with small speakers because you will be listening to the same volume regardless of the amplifier. I have been testing some very small bookshelf speakers using our 300 w/ch reference amplifier. No problem. Of course, I don't crank it all the way up because I would damage the speakers, and cranking it up would make it so loud, I couldn't stand to be in the room. If the amplifier is too small, turning it up could damage the speakers due to clipping. If the amplifier is huge, turning it up could damage the speakers as well. This is why the suitable amplifier power specification is given. However, I much prefer to have enormous power reserves for transient peaks than an amplifier that gives out when the crash boom bang comes along. I set the volume at about 80 dB for movies, and everything goes smoothly. I could have a 10,000 watt amplifier, and as long as I set the volume at 80 dB, the final result would be the same as having a 200 watt amplifier set to 80 dB, except during very short transients when the 10,000 watt amplifier would be superior.

The square root of 8 is 2.83 Volts, which is the newer standard for measurement (dB/2.83 Volts/1 Meter), compared to the older one of dB/W/M. The dB measurement is made in an anechoic chamber with the microphone at one meter from the center of the speaker, on axix, using 2.83 Volts input. You are solving the formulas for the constants rather than the variables. Basically all consumers really need to know is that, the more sensitive the speakers are, the less power will be required to drive them at an particular volume. For every 3 dB less sensitivity, the required power doubles. For every 3 dB more sensitivity, the required power is reduced by half. So, let's say you like to listen at about 80 dB loudness, and for speakers with 92 dB/2.83V/M sensitivity, you need 10 watts per channel going into the speakers. If you bought some new speakers that were 89 dB sensitivity, you would need 20 watts per channel to get the same volume. If you bought 95 dB sensitivity speakers, you would need only 5 watts. This makes a big difference with built-in receiver amplifiers. One of the drawbacks of high sensitivity speakers is that they tend to have a less smooth frequency response. However, they can be truly excellent when well designed.

Q I enjoy reading your Q&A sessions every week. One item I am concerned with is last week's response in regards to tone controls. The
reader's question was "how does Cinema EQ differ from regular tone controls?". In your answer, you briefly mentioned Cinema EQ as a different
equalization curve, then started comparing it to DSP modes. IMHO, your answer seemed to imply (right or wrong) that Cinema EQ was just a
soundfield mode. In actuality, it is a high-end rolloff very similar to the re-equalization curve used by THX to "tame down" the excessive
brightness many soundtracks exhibit. Unlike THX, this EQ is adjustable, allowing personalized settings and the ability to somewhat compensate for slight timbre mismatches front/rear/front effect. While I don't doubt your understanding of this, I believe your explanation was unclear and possibly misleading to your readers who don't understand this EQ's purpose/effect. Perhaps you would post an addendum to your reply. Please keep up the good work!

A No matter how much we read and edit our material before we publish it, things get through now and then that are unclear. This is one, and we appreciate your E-Mail. Cinema EQ is a type of DSP, but it can operate along with other DSP modes, such as Concert Hall or Jazz Club. The schematic diagram on the left shows the Yamaha DSP parthways in the Yamaha DSP-A1 Processor/Amplifier (it is not a receiver since it has no AM/FM tuner). The signal is decoded from DD or DTS by the Yamaha YSS-249 or DSP156009 respectively. Then, the digital signal passes into the main DSP LSI, the Yamaha YSS-214, where it has several possibilities including DSP presence modes and Cinema EQ. The latter can be used in all channels to reduced brightness that occurs in many movie sound tracks, but it is still DSP. It can also be used for fine tuning the tonality of front vs. rear speakers. The graph on the right shows how Cinema EQ affects the front left/center/right in the Yamaha DSP-A1. Following Cinema DSP and or Cinema EQ, the signal for each channel passes through a D/A converter, and then to the analog pre-outs or to the built-in power amplifiers This particular mode acts sort of like a notch filter or single slider in an equalizer in that the frequencies around 12 kHz are diminished. There are other types of Cinema EQ as well, that affect different frequencies. You can accomplish the same thing by using a multi-channel home theater equalizer, but in that case, the EQ is performed in the analog domain, while in the Cinema EQ for the Yamaha, it is performed in the digital domain.

Q I'm soon going to buy a DD home-theater system.I like a lot of bass so, I will be considering five Subwoofers.

The system is as follows:
NHT VT-2 (2) Front left/right
NHT VS-2A Center
NHT VS-2A (2) Surround left/right
I will bi-amp the subwoofer module on the VT-2s, with an SA-2 amp each.

The whole system will be run by:
Meridian 565 7.1 (Processor)
Meridian 562V (Control)
Meridian 518 (Enhancement)

It will mainly be used for DD and DTS programs. DD and DTS require full-range surrounds, so is it in fact better to have a subwoofer for each
channel (total 5 subs)? The NHT VT-2s already have a sub built into each, I will add a Velodyne FSR-15 for the center channel and two small subs (such as the Atlantic 162PBMs) for the surround channels? Will this work, or will there be so much bass, that it will cancel out? The left and right channel subs will be aimed outwards, the center will be aimed forwards, and the surround subs will be aimed inwards towards the center of the room.

So, will this cause any problems? The bass should be cleaner, as it each sub doesn't have to work as hard, resulting in less distortion right?

A Theoretically it should work just fine. However, placement of multiple subs is difficult. Let's call the difficulty increasing as a function of the inverse of the number of subs². So, placement of five subs will be 25 times more difficult than placing just one. Multiple subs can be spectacular however, when done properly. Rather than five though, I would suggest three. One each for the front left/right and one for the center and rear. Place them all in the front, at unequal distances from the walls and with the front left/right at different distances from their respective walls. In other words, the front left might be one foot out from the back wall and 1.5 feet from the side wall, while the front right might be 1.75 feet from the back wall and 2 feet from the side wall. The center sub should not be placed exactly in the middle but off to one side slightly, say six feet from one side wall and 7 feet from the other. You will indeed get less distortion from several subs compared to one. There is also an enormous three dimensional effect, even though the low frequencies are non directional.

Q Is it a good idea to get a Pro Logic receiver with the ability to individually control the volume of its center speaker?

A All surround sound receivers and processors allow you to individually control the center channel volume (there may be an odd one out there - bargain basement product - that doesn't let you do that, but all the ones I have seen do let you control it). More advanced receivers let you control the delay to the center channel since it is closer to where you sit than the front left/right speakers. With DD and DTS, it is handy to be able to control the volume of the rear left separately from the rear right, but this is not absolutely necessary. However, center channel volume control separate from the front left/right is critical. Some consumers think that after the setup procedure is done (from the instruction manual), they should have the proper channel balance for all movies and music. This is certainly not the case. Setup is fine for getting started. After that, adjust everything to suit your own taste.

Q I am curious as to what devices and/or methods are used to conceal A/V components in Home Theaters. I have components from various manufacturers and would like a single remote to operate all. I have seen several learning remotes available today. However, I also desire to conceal all components from view with the exception of some type of IR receiver to relay a single remote signal. Any information would be appreciated.

A Placing components in an A/V cabinet is pretty straightforward. There are lots of beautiful designs available, and if you like to work with wood, an unfinished furniture store is a good place to start. One of the things you have to be careful of is heat dissipation. Power amplifiers produce lots of heat. Even if they don't get very warm sitting on a table, plenty of heat can accumulate in an enclosed cabinet. A small ventilation fan in the rear of the cabinet is helpful. Otherwise, make sure that there is sufficient space above the power amplifiers for heat dissipation, and leave the cabinet door open slightly when the system is turned on (holes drilled in the top of the cabinet, where they can't be seen, will allow some heat to escape, and will assist the fan). Many components come with excellent learning remotes, so getting a separate one may not even be necessary. There are numerous companies that make remote controls for system installations, including ones that utilize RF so you can operate the system from another room.

Q Currently I have very old home theater equipment and have been looking to replace it. Unfortunately, it has become quite difficult to determine which equipment is the "best" for my needs. I watch a lot of movies and listen to a lot of music at high volumes. What would you recommend for a receiver, outboard amp(s), decoder (DD, DTS), DVD player, cables, and speakers (front, center, rear, and sub)? My budget is in the arena of $10,000 to $15,000 (possibly more if I can convince my wife). I have asked local shops for estimates and recommendations, however I am not satified with the equipment they are trying to sell me. The bottom line is that I need ample amounts of power and high quality sound using equipment from reliable manufacturers.

A Based on your budget, I would suggest the following as a starting point for listening: Yamaha DSP-A1 Processor/Amplifier, Panasonic A-310 or Yamaha DVD-S700 DVD Player (we reviewed the 310 and are preparing a review of the 700), four Krix Esoterix Floorstanding Loudspeakers, Krix Equinox Center Speaker, Velodyne FSR-18 Subwoofer. This is the setup I have in our reference home theater right now, and it is awesome.

Q I want to build my own subwoofer and use separate amplifiers. Should I use a single voice coil or double voice coil driver?

A Use a single voice coil driver if you are going to power it from the mono subwoofer line level output from the receiver, with a single power amplifier. If you want to use two amplifiers (one each for left and right channels), then get a dual voice coil driver. In the case of using an old receiver to power it, get a Y connector for input to the two highest power channels and the output to a dual voice coil driver.

Q if you put your receiver in wide mode does the center channels's lower frequenciencies also output by the subwoofer if
you use the sub preout on the reciever? If so then I would imagine that most people with speakers across the front that go down to 50 Hz would prefer to listen to wide mode with the crossover on the woofer set to 50 Hz.

A Wide mode is an older mode that is being replaced by the numerous choices in DSP sound fields. In general, the low pass frequency to the subwoofer output is fixed. It may be 100 Hz or 90 Hz (so signals below these frequencies are sent to the subwoofer). Depending on how sophisticated the bass management is on your receiver, you can direct the low frequencies from various channels to the mains or to the subwoofer output, but the cutoff frequency remains the same. If your subwoofer output has 100 Hz and below, and you are directing the low frequencies from the mains, center, and/or rear to the subwoofer, you would need to set the crossover of the subwoofer to 100 Hz (actually probably a little below 100 Hz to reduce overlap). Othewise, you would be missing the 50 Hz - 100 Hz for the channels that are being low frequency directed to the subwoofer. If you have speakers that are good to 50 Hz all the way around, the subwoofer output jack may still be sending <100 Hz to the sub, unless you have set the bass management to subwoofer off or subwoofer none. In the case of full range speakers, set the bass management to large speakers and the subwoofer to 50 Hz. This way, you will ge the lowest octave, which is pretty much non-directional.

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