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Watts Per Channel/AV Receiver Architecture Questions? (1 Viewer)

Doug2000

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I'm new to HT (but not to audio) so I'm trying to understand how to best interpret the specs on HT AV Receivers regarding watts per channel. The units have many channels but the spec seem to only show watts per for the two front channels. Is there any way to find the power rating for the other channels?

For example, I looked at the Marantz SR8012 (but it seems the same for other manufacturers). This unit has 11 channels. Per the specs its rated at 140 watts per channel. The fine detail says" "The continuous power rating (in watts) for each stereo speaker output channel when the receiver is in stereo mode." So for example, is it published anywhere how many watts this unit pushes for the other 9 channels in surround mode?

And further why would they specify "in stereo mode" unless the fronts have less power in the various surround modes?. do the Front Left & Right get different wattage when the unit is in surround mode (vs Stereo mode)? Are these kinds of specs published anywhere from any of the manufacturers? I briefly looked at specs from a couple other brands - seems the same.

My going in assumption is these units have separate amps for each channel. Is that incorrect? Do they have some kind of technology that allows them to distribute the units total reservoir of power across whatever channels are being used depending on the mode the unit is in (surround/stereo/etc)?
 

Clinton McClure

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There’s no real way to check this. Most, if not all, manufacturers list their power ratings with some ridiculous number like “one channel driven at 200Khz with 10% THD”.

For the most part, you can completely ignore what any receiver manufacturer claims to be their power handling and know that as long as you have fairly efficient speakers, you’re going to be ok. If you get into really inefficient, yet otherworldly sounding speakers like Thiels ( @JohnRice ) can back me up on this, you will burn up most receivers and want to move to separates with actual 1, 2, or 3 channel amps that truly give you massive power handling.
 

JohnRice

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I'll come back when I have more time, but how manufacturers fool you is by giving output ratings for one or two channels, or as Clinton stated, giving a worthless output rating for one channel. Receivers generally are capable of pretty decent power output per channel, but don't have enough power supply to drive more than one or two channels to that level at the same time. So, when you're watching a loud action movie with lots of channels, you're most likely to run out of power coming in. Equipment can't put out more power than it has available coming in, and power supplies tend to be the most expensive component in a receiver.
 

Doug2000

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Ok. Got it. Thanks for the info.

Disappointing that the specs in this regard are apparently intentionally misleading (sounds like they are mostly marketing hoopla). I was hoping to learn something real from the specs - but I guess not.
 

JohnRice

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The question, is how much power do you need? That's also a complex one, since it gets into what your speakers are, how efficient they are, if you want maximum dynamics, and so on. It's not like you are usually going to notice when you run out of power.
 

Doug2000

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The question, is how much power do you need? That's also a complex one, since it gets into what your speakers are, how efficient they are, if you want maximum dynamics, and so on. It's not like you are usually going to notice when you run out of power.
I understand what you're saying. This stuff can be very complex - especially if you're trying to figure it out on paper.

To be clear - I'm not looking to buy an AV Receiver. I am currently building my HT around a Marantz preamp. And a separate 700 watt, 2 channel amp driving a pair of near field studio monitors for front speakers. I have a powered studio monitor I'm using for the center channel and am planning to use powered studio monitors for all the other speakers (surrounds, backs, height, etc.) - but those are not in place yet.

So as I build out this HT system one of my concerns it to make sure all these speakers play well with each other. I've already been surprised once. I assumed my 50 watt center speaker would be too weak compared with my fronts, but it was actually too loud (dialog was over boosted) so I had to turn it down 10dB to bring it into a good relative range.

My goal regarding these specs was to see the relative power these AV Receivers send to (for example) the surround speakers vs the fronts, or the height speakers vs the fronts, etc. - and use that as an input into the power rating of the powered speakers I should get for the rest of my system. But as indicated, the Receiver specs are not going to tell me that. So I'll just have to work my way through it.
 
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Clinton McClure

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One thing to keep in mind when putting together a multi-channel HT is that you want your front three speakers (right, center, left) to be by the same manufacturer and, ideally, out of the same product line. This is so there is no awkwardness of sound or tonal differences during front panning effects. In some cases, the center channel can be from a different manufacturer but still sound ok with the front mains. Surrounds, Atmos height speakers, and subs can be from different manufacturers.
 

JohnRice

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Ah. Now I get it. That’s not quite how it all works. And there are a lot more variables. I can’t write a full explanation right now, but will later.
 

Dave Moritz

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The Audioholics review is a very good review and they even do a bench test on the SR8012. It is sad that so many will rate especially the lower end models at 1KHz using one channel just to pump up the wattage numbers. I own the Marantz SR8012 and this receiver doesn't disappoint. There are alot of great features. performance and it is built like a tank. The one thing the SR8015 will do is you can disconnect the amp from the preamp when running an external amp to reduce distortion.
 

JohnRice

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I have a powered studio monitor I'm using for the center channel and am planning to use powered studio monitors for all the other speakers (surrounds, backs, height, etc.) - but those are not in place yet.
I thought powered monitors usually had a volume control on them. Will that be the case?
 

Doug2000

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I thought powered monitors usually had a volume control on them. Will that be the case?
Many (probably most) powered speakers have a volume control. But, unfortunately the ones I'm using/plan to use do not. For the center channel I knocked 10dB off with an inline pad (in the XRL cable between the pre and the amp). Looks like this:

img_9133-jpg.155758

This brought the volume into a range with the fronts where I could fine tune it with the center channel adjustment in the Marantz preamp.

you want your front three speakers (right, center, left) to be by the same manufacturer
Probably a really good idea but these are very good speakers I had already from my previous recording studio so I wanted to leverage them. After padding down the center speaker & dialing them in with the fine adjustments available in the Marantz the system sounds excellent. Beyond my expectations.
 

JohnRice

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Doug, you walked right into one of my most common topics, which is Gain vs. Power. They're often confused. If you're going to mix powered studio speakers with a home system, you'll have to deal with some incompatibilities, such as you've already found.

Simply put, gain (voltage) influences how loud an audio signal is. Power (wattage) is how much power is available to let a speaker reproduce sound. They're two completely separate things. Home audio gear generally falls into certain ranges, which makes them more easily compatible with each other. Speakers generally fall into a sensitivity range pretty close to 90dB using standard techniques. Home amps generally have a gain in between 27dB and 32dB. Both these mean there aren't massive inconsistencies that have to be corrected for in a surround system. So it seems your powered center speaker has an amp with significantly higher gain than that. If that puts it outside where the channels trims in the preamp can balance it with the rest of the system, then you need an attenuator. The thing is, that has nothing to do with how much power (watts) it's capable of.

So if you are intent on using active studio monitors for your system, and they lack a volume control, you might have to add more attenuators, but their power rating has nothing to do with that.

I just want to correct a technicality, "gain" is actually how much the voltage is increased at a certain stage, not the voltage itself. I didn't want someone coming in to correct me.
 
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Doug2000

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Doug, you walked right into one of my most common topics, which is Gain vs. Power. ...
Thanks so much for the info/clinic. Very helpful.

(sorry for the slow response - been traveling)

Yeah - I'll likely need to use more attenuators which sucks.

My new surround speakers are at home waiting but I wont be home for another week to try em out.
 

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