[deepstang]

My friend told me that from "benchmark" tests of wattage and signal-to-noise ratio, when you take a receiver like my Onkyo 605 and go from having 5.1 speakers connected to 7.1, the other speakers take a huge hit. He said if Onkyo claims 90w x 7....if i have 5.1 speakers connected I might get 90x5, but if I connect 7.1 speakers the receiver drops to maybe 40w x 7 and more distortion

.


I can see his thought process, but i don't know if that is really true. If that is the case, I am scared to try a 7.1 vs a 5.1 if my mains and entire system will take a big hit.


Has anyone heard definitive info about this?

 

[graphicguy]



Quote:
Originally Posted by deepstang /forum/post/16885996


My friend told me that from "benchmark" tests of wattage and signal-to-noise ratio, when you take a receiver like my Onkyo 605 and go from having 5.1 speakers connected to 7.1, the other speakers take a huge hit. He said if Onkyo claims 90w x 7....if i have 5.1 speakers connected I might get 90x5, but if I connect 7.1 speakers the receiver drops to maybe 40w x 7 and more distortion

.


I can see his thought process, but i don't know if that is really true. If that is the case, I am scared to try a 7.1 vs a 5.1 if my mains and entire system will take a big hit.


Has anyone heard definitive info about this?

Generally speaking, driving more channels will have less power to each channel than driving less.


In your particular case, I don't know how big the power supply is, nor if it is capable of providing equal power to all channels at the rated spec. Also, without knowing what the nominal impedance of your speakers, it's tough to give a definitive answer.


In short, I don't think your friend can make a blanket statement that power is cut by 50+% to each channel going from 5 to 7 channels.

 

[BruceOmega]



Quote:
Originally Posted by deepstang /forum/post/16885996


..... I am scared to try a 7.1 vs a 5.1 if my mains and entire system will take a big hit .....

Independent of the answer regarding the receiver's amps, if you are thinking about trying 7.1, then I definitely recommend trying that if your room layout supports a 7.1 speaker array per the Dolby recommendations; e.g., you have space behind the listening position for 2 rear surrounds.


When I expanded from 5.1 to 7.1, I found a significant improvement in surround envelopment.


If it turns out you like 7.1 but it does create a problem with your current receiver, you could upgrade as time and money allows to better amplification.


In the interim, if adding two additional speakers does cut the power per channel in half, that is only a 3db reduction in volume. If distortion is not an issue, then you may not have a big problem with the current receiver and / or it may be something you can live with until you upgrade.


Bruce

 

[Dzhokhar]

Generally speaking, I think your friend's example is an exaggeration.


In most receivers there is are two limits on the power they can output. One of those limits is the power limit of each individual amplifier and the other is the limit of the power supply which feeds power to those amplifiers.


The specification that manufacturers generally report is the limit of each amplifier. This limit is usually an accurate representation for 1-2 channels but often falls apart as you add more channels where the total power limit of the power supply dominates.


In the case of going from 5 to 7 channels, you'd generally get about 5/7 as much power from each channel with 7 channels as you would with 5 channels. In the case of a system where you get 90Wpc with 5 channels, you'd only be able to get about 64Wpc with 7 channels (but the same 450W from the system as a whole).


That said, surround channels generally don't receive as much content as mains, so the actual effect is less than would be predicted from driving all channels equally (as I described above).



The real disadvantage of a 7.1 setup is that the two extra speakers take away money that you could have spent on a nicer 5.1 setup. Also, you have to have an appropriate room configuration in order to benefit from 7.1, something which a lot of people don't have (either because of room size and shape or aesthetic considerations).

 

[MichaelJHuman]



Quote:
Originally Posted by deepstang /forum/post/16885996


My friend told me that from "benchmark" tests of wattage and signal-to-noise ratio, when you take a receiver like my Onkyo 605 and go from having 5.1 speakers connected to 7.1, the other speakers take a huge hit. He said if Onkyo claims 90w x 7....if i have 5.1 speakers connected I might get 90x5, but if I connect 7.1 speakers the receiver drops to maybe 40w x 7 and more distortion

.

Here's a review of the 606 with benchmarks. Your receiver might perform close to this as manufacturers often don't change much from year to year.


Not that it does not hit it's rated power into 5 channels, this is normal for receivers. The drop between 5 and 7 channel power is quite respectable.

http://www.ultimateavmag.com/avrecei...06/index6.html

 

[deepstang]

In my specific set-up, the extra speakers are already there. I currently use in-walls mounted high on my rear wall as my surround speakers. I am going to definitely get some bipole on-wall to replace the in-walls. So, that leaves those in-walls going to waste if not connected. I have yet to buy the bipoles, but here is a pic of the current in-walls that I can use as the 6 and 7th speaker:

The problem is that my new front mains are not as efficient as i would like, so that is taking more power. I also plan on getting a dual sub set-up. I am worried that I may be demanding too much from my receiver. I know the most important speakers for HT is the center and sub...so I don't want to rob them more than I need to.

 

[deepstang]



Quote:
Originally Posted by MichaelJHuman /forum/post/16886982


The drop between 5 and 7 channel power is quite respectable.

http://www.ultimateavmag.com/avrecei...06/index6.html

So, you are saying the Onkyo is doing a good job. I wonder if it is worth it. I guess I can run the wires and see if I notice a difference. The 605 can not support anything lower than 8ohms, so I am not sure how close that 606 article applies.


Also, in that article, what is meant by

:


"The manufacturer's stated distortion of 0.08 % was reached at 71.8 watts with seven channels driven into 8 ohms. However, the specs are stated for two channels driven, so looking at the graph, the amp reaches this distortion level at nearly 115W, which is considerably above the stated power spec."

 

[snpanago]



Quote:
Originally Posted by deepstang /forum/post/16887166


In my specific set-up, the extra speakers are already there. I currently use in-walls mounted high on my rear wall as my surround speakers. I am going to definitely get some bipole on-wall to replace the in-walls. So, that leaves those in-walls going to waste if not connected. I have yet to buy the bipoles, but here is a pic of the current in-walls that I can use as the 6 and 7th speaker:

The problem is that my new front mains are not as efficient as i would like, so that is taking more power. I also plan on getting a dual sub set-up. I am worried that I may be demanding too much from my receiver. I know the most important speakers for HT is the center and sub...so I don't want to rob them more than I need to.

Hello. From what I've read and from what I've experienced in my own application, your rear wall seating couch (configuration) will not lend itself to appreciable 7.1 enjoyment.

The couch would need to be a few feet from the rear wall with the surround side speakers mounted near that new couch position (eg your new bipoles).

 

[MichaelJHuman]



Quote:
Originally Posted by deepstang /forum/post/16887186


Also, in that article, what is meant by

:


"The manufacturer's stated distortion of 0.08 % was reached at 71.8 watts with seven channels driven into 8 ohms. However, the specs are stated for two channels driven, so looking at the graph, the amp reaches this distortion level at nearly 115W, which is considerably above the stated power spec."

I will try. Before I try, I will note that I have been critized before for what I am going to say. Unfortnately, I don't have access to very specific info on the FTC amplifier rules.


Years ago, the FTC decided that there needed to be a rule about measuring amplifier power.


This is a summary of the rule at one point in time (from what I can find on the topic)


* There was a one hour preconditioning period of 1/3 rated power; I believe it's now 1/8; This is not advantageous to the manufacturer

* The bandwidth has to be stated

* The receiver must play for 5 mins (Not sure if this has been changed)

* Power is started in RMS; a way of averaging waveforms


This was all fine and good, but the FTC weakened the rules around the year 2000. And multi-channel amplifiers, like a receiver has fall under a murky part of the rule which states that 'All associated channels must be driven.' What's an associated channel? You got me. But based on my reading up on the topic, the usual interpretation seems to be a stereo pair. So for example, the receiver is tested by driving only the left and right channels.


Going back to your question, the article writer is saying that the receiver only needed to meet it's rated power into two channels, like a stereo receiver would. And it exceeds this, which is admirable. Like most receivers, it does not hit rated power with 5 channels driven, but it's not bad. And with 7 channels driven, it's power level does not fall off that much. I would say it's a pretty capable receiver. Some receivers 7 channel power is less than one half rated power, which is what your friend was talking about.


The thing to remember is that the 7 channel output of most receivers won't be half of the 5 channel power, but it might be half of the RATED power. I think that's were your friend either said it wrong, or misunderstood the sitution a bit.


Here is more info on the topic -

http://www.soundstage.com/gettingtec...ical200503.htm

 

[deepstang]

Thanks! The more I read, the more I think it maybe a better idea to stay at 5.1 with my rear seating so close to the rear wall. If it did not draw more power, i would have probably gone the 7.1 route since the only additional investment would be in speaker wire.


MJHuman, thanks for your explanation!

 

[OppoPX14]



Quote:
Originally Posted by deepstang /forum/post/16885996


My friend told me that from "benchmark" tests of wattage and signal-to-noise ratio, when you take a receiver like my Onkyo 605 and go from having 5.1 speakers connected to 7.1, the other speakers take a huge hit. He said if Onkyo claims 90w x 7....if i have 5.1 speakers connected I might get 90x5, but if I connect 7.1 speakers the receiver drops to maybe 40w x 7 and more distortion

.


I can see his thought process, but i don't know if that is really true. If that is the case, I am scared to try a 7.1 vs a 5.1 if my mains and entire system will take a big hit.


Has anyone heard definitive info about this?

It's true, but the added room fill with 7.1 out weigh the slight loss of power.


If you go by your friends logic, then you should only use two channels.

 

[JOHNnDENVER]

Generally no loss of power because audio in general and surrounds specifically do not use continuous signals. So all channels driven specs against even 2 channels driven are not really going to be a factor. IMHO of course.

 

[deepstang]



Quote:
Originally Posted by JOHNnDENVER /forum/post/16896729


Generally no loss of power because audio in general and surrounds specifically do not use continuous signals. So all channels driven specs against even 2 channels driven are not really going to be a factor. IMHO of course.

Yeah, I was wondering about that. For example, movies in 5.1 TruHD formats, where the other 2 channels are not in use, I would assume that the power and disotortion should only be split for those 5.1 channels and not for all 7 speakers (of course if the 5.1 is bypassed and an "all channel" mode is selected this would not apply).