[ Reciever ]
A1. Given that the THD at 1kHz is 0.7% at 6 ohm, how high would it be at 20Khz? It almost appears as if the amp is unable to drive even 6 ohm speakers with good quality. By comparison, the Outlaw is able to drive the whole 8-4ohm range with 0.05% for all audible frequencies.
A2. Though it is not designed for it, what kind of THD could I expect when driving 4 ohm speakers from the reciever?
A3. Would this reciever (designed for 8 ohm) be able to sustain 4 ohm speakers _stabley_ (as 4 ohm speakers are likely to drop to 2ohmish)?
A4. With the 8.1A PS, what dB range would I be able to run the system at given the stated 5.1ch speaker set (and not including the amplifier)?
A5. Are the pre-amp outputs of the reciever also suceptible to the frequency response of the reciever (Due, i suspect to the signal processing)?
[ Amplifier ]
B1. If an amplifier is used for each of the main outputs, how do they know what gain to use in order to match the dB of the other speakers (center, surrounds, sub)?
B2. If separate amplifiers are used to drive left and right channels (instead of using a stereo amplifier) what is the possibility of and extent that the dB will vary between the left and right?
B3. Is there any audible sound quality benefit to separating the main channel into HF/LF and using a bi-amp connection to the main speakers if the original source is a combined pre-amp out?
B4. Are there any mono amplifiers available (<$400 @ 150W-200W) with a built-in crossover?
B5. Given that the reciever has increasingly disruptive THD when driving 6 ohms, would using a 7 channel amplifier with a stated 20Hz-20kHz 0.05% THD yield an audible sound quality increase?
[ Speakers ]
C1. If you separate the HF/LF of the main speakers, would driving each half be less of a load on the amplifier with regard to wattage per dB? It seems odd that driving 6 speakers would use the same amount of energy as driving 3. In the case of the stated M80's, both HF and LF would still be 4ohmish.
A1. Human ears begin to really hear distortion at about 10% THD. Most of the time speakers will always produce much higher levels of distortion than any amplifier, even tube amps. Unless you see the THD values go into the few percent range, I wouldn't worry.
A2. Who knows, they didn't list it. Notice how 8 ohm THD is over the whole frequency range but 6 ohm THD is at 1 KHz?
A3. Maybe.
A4. What you need to do is use the sensitivity ratings of the speakers and the expected power they will receive. These speakers appear to be highly sensitive at 95 dB 1W/1m. I imagine with this receiver and these speakers you should be able to achieve on the order of 110 - 113 dB, possibly slightly higher, without major issue. Speaker sensitivity affects SPL far more than amplifiers do. For example, going from 50 watts to 100 watts means +3dB, most people can't hear differences much smaller than this. But a speaker with a 95dB sensitivity requires half the power that a 92dB speaker would need to produce the same SPL's. Doubling the volume on the amplifier end of things requires TEN TIMES the power. Keep in mind here that a 90dB sensitivity is starting to get into the higher sensitivity range. Many acoustic suspension systems have 85dB sensitivities.
A5. They might be, they might not be. My guess would be no.
B1. They wouldn't unless there was some kind of feedback about the SPL of each individual speaker.
B2. Very high, because you could have the volume controls set differently. Seriously though, if they're the same amplifier using components made by the same people, variance should be extremely low. Different amps is a different story.
B3. No. Next question!
B4. Yes, in fact. I know of only one or two, the one I can think of is the dbx MPA-150 (this amp is an eBay special seeing as they haven't been made for about 20 years now). 150 watt stereo input mono output with low pass crossover, but not variable.
B5. Not because of THD alone. Thing to remember about THD is that you may well throw it out the window most of the time. I can't remember exactly why but apparently THD is a poor indicator of anything, where a THD+N (noise) rating tells you more. That and the fact that companies like to list THD in sneaky ways, like they did here. Check Wikipedia, the article there is decent.
C1. Theoretically, the best amplifiers will be able to "double down" when the impedance is halved (this is what's theoretically supposed to happen anyway). That is, with half the load the amplifier should be putting out twice the current, and therefore power since they run at a constant voltage. So theoretically biamping on two discrete amplifiers as opposed to one would give you 100 watts x 2 amplifiers @ 4 ohms as opposed to 50 watts x 1 amplifier @ 8 ohms. I forgot exactly what the question was already but I know I explained it. In an HT receiver, the more speakers you use the less power per channel you get. For example, running them in stereo might allow the amp to produce 100 watt peaks without clipping, but with all the surround speakers going that will drop considerably, depending on the amp. Oh, that's right. Wattage per dB? That doesn't make any sense. Given a speaker under certain conditions you're going to get the same output for the same input no matter how it's connected. There's good information in stickies posted at these forums. Read them!
