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Home Theater/receivers - surround sound


I bought a new 5.1 HDMI receiver recently and was kind of surprised by how different it sounded vs. my older 5.1 non-hdmi (10+ year old) receiver, that I have been using ever since.  This new receiver does 75 watts per channel at 8 ohms (20hz - 20khz), and sends equal power to all 5 channels, as it has discrete amplifiers.  My old receiver is 100 watts per channel at 8 ohms (100w + 100w, one channel driven - not sure what this means or if it's any good, and 40hz-20khz).  Not sure about the frequency thing either, or what's better.   Anyways, this new receiver has automatic calibration via the setup mic.  I did this a few times.  While watching a movie this new receiver sounded different than the old receiver.  The old receiver sounded louder all around.  On the new receiver, the automatic calibration made the sub not have enough bass, the center channel was louder than all the other channels.  Here is a breakdown of what the calibration set:
FL    9.8' (3.0 db)
FR    9.9' (1.0 db)
C    9.3' (3.0 db)
Sub    12.1' (+0.5 db)
SL    8.3' (1.5 db)
SR 7.9' (2.0 db)
Crossovers - Front 200Hz, Center 120Hz, Surround 200Hz.

The only settings that could be done on my old receiver is set the distance to the speakers and set the db for the speakers.  No automatic calibration.  My question is why would this new receiver sound different?  Also, my old receiver didn't have this Crossovers thing.  What is this for and is it any good?  This new receiver has this new feature called "Variable High/Low Pass Crossover Points.  It also has Automatic Equalization whereas it has a equalizer built in.  I should note that with the new receiver things sound very accurate, but less in your face loud all over, like what you would get in the movie theater.  Center speaker is very clear though and loudest.  Not sure if that's a good thing.  I wonder why the automatic calibration didn't set the Front Left and Front Right the same.  They are equal in every sense of the word, and equal distance.  I could set everything manually, but then automatic equalization gets turned off, and the crossover thing gets confusing.

Lastly, on my old receiver, loud was about 30db.  Also, as you turn the volume up the db goes down, so 50db would be less loud than 30db.  On the new receiver I found 50db to be quite loud, and as you turn up the volume the db goes up, so 70db would be louder than 50db.  Do you find this quite strange that both of these receivers are different in this sense?  Also, given that 30db was loud in the old, and 50db is loud in the new, would this be about equal even though one receiver is rated at 75 watts, and the other at 100 watts?

Thanks for any help you can offer with all of this.

From the top:

- Discrete amplifiers does not mean "all channels receive full power" - it just means that the channels aren't driven by an IC chip amp; this is fairly common for amplifiers larger than 50wpc unless switching amplifiers are used. Without calibrated measurements it's impossible to know what the actual per-channel output capabilities of either unit are, and the published specifications tell us almost nothing (because we have to assume that in both cases they are at best optimistic, and at worst outright lies - there is no accountability or legal protection for consumers when it comes to power specs on amplifiers).

- The difference in sound is almost certainly due to the auto-calibration, which does more than just set distance (time delay) and "db level" (channel leveling); it will also perform equalization (depending on how fancy a model, and who made it, this equalization can be VERY complex), and bass management (the crossover). The bass-management feature is very good - it's attempting to blend the satellite speakers to the subwoofer - in general the subwoofer should not be "heard" or "seen" in a system; bass should just be present in equal proportion to the rest of the spectrum (all the subwoofer is there to do is "fill in" for speakers that are too small to reproduce bass, it is not meant to add tons of "boom boom" to the experience). The crossover is basically the "hand off" frequency between the satellite and the subwoofer (and it isn't a brick-wall - there will be some signal below 200 Hz going to the satellites, and some above that going to the subwoofer; it usually rolls off at something like 12 or 18 dB/octave). The crossover points it set either mean that your satellite speakers are very small (<5" woofers), or that the microphone/calibration was negatively influenced by something (it couldn't get a good "read" on the speakers). If your satellite speakers are very large (like if your front left/right speakers are full-range towers with 10" woofers and an F3 much lower than 200Hz) you should re-try the calibration with the microphone in a different place, also try it with background noise objects powered off (for example if your home has air-conditioning, turn that off).

The equalization feature targets a manufacturer-designed curve - usually something approximating "flat" - whereas the previous model provided no equalization and you got whatever you got as a result of the speaker's interaction with the room. If the newer receiver has very elaborate EQ capabilities it can also try to address (but not entirely fix) things like reflected sound.

Equalization and placement is why your front left/right speakers also calibrated slightly differently - while they may be identical off the assembly line, they aren't placed in the exact same location within the room, so they will sound different as a result of their interaction with the room.

The loudness you previously heard was probably either distortion or compression (the "movie-theater like" sound is what makes me believe that; essentially things sound "loud" even if the overall intensity of the sound-wave isn't there because things are compressed, distorted, etc; its very fatiguing and leads to the "in your face" kind of attack (a good sound system should play loud without sound like that)). There's a chance the amplifiers in the new model are more robust and are therefore putting out less distortion and leading to less compression, coupled with the equalization and bass management (which also helps to improve efficiency, to a small extent). "Clear and accurate" should be the goal.

The center being set highest is either because it sits further away (or off-angle; for example if it's up on top of a TV cabinet it may be the same distance in a straight line from where you put the mic, but in absolute terms its further away (because its at an angle)), or because it is less sensitive than the other speakers (this isn't uncommon), meaning that it needs slightly more power to achieve the same output level. Finally, placement is also a big factor - how it interacts with the room and its surroundings influences how loud it can get from a relative position in the room.

- You cannot compare the relative volume dial positions of two receivers, ESPECIALLY if one (or both) of them perform automatic calibration (as they will actually move their relative volume scales to match; THX certified models, for example, will re-target themselves so 0.0 dB equates to 85 dB SPL (or as close as they can get to that), which will mean different power output and so-on depending on what speakers, room, etc are available). On the model where the "db goes down" it likely isn't going down - there's likely a "-" (minus symbol) being drawn (it may look like a dot depending on how small the screen is) to indicate that you're moving from "-30 dB" to "-50 dB" (where -30 is a larger value). This is done to be more in-line with professional equipment (and for home theater components, more specifically to be in-line with THX certified equipment) which reports volume levels as how much reduction or enhancement over "line level" is occuring (line level being 0 dB); however with auto-calibration on modern receivers the entire scale is moved up or down based on the calibration results, so it becomes a basically meaningless number (and it would be easier if they just went back to the "1-10" scale in many cases). On older receivers (early to mid 1990s), the 0 dB point generally corresponded to "full open" or "line level" on the volume control (if memory serves it was either Yamaha or Lexicon that first implemented this; most other manufacturers followed very quickly, especially as THX moved into the consumer sphere in the late 1990s). Your newer receiver may also go beyond 0 dB, where the pre-amplifier section is applying additional gain to the signal; this will usually result in some degree of audible distortion.

The older model just counting up from 0 (or something near it) to something like 70-100 dB is not uncommon for something from around 2000 - a lot of manufacturers did that as a "me too" feature to throw "dB based volume controls" on their products, the numbers are equally meaningless because they don't show any applied gain, reduction, output SPL, etc - it's just a random sequence of numbers that they threw a "dB" symbol onto.


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