5.1 AVR for 7.1

labrat

Hi all,

I have added a pair of S8 to my bedroom setup and am thinking of using four S4 for surrounds. (Center is CS250S) The problem is I have a cheap JVC 5.1 AVR and no funds at the moment for the 7.1. The proposed solution is to hook the left side and rear surround in series to the left surround output and do the same on the right. This will show the AVR a 16 ohm load and reduce the output from 100 to 50 or 60 watts. I am assuming the side and rear surround signal are almost always the same on a 7.1 AVR. My guess is that this should help diffuse the surround sound, although it may need to be turned up about 3db to get the same level.

Has anyone tried this? Any guesses if the sound will be better than just running 5.1? It would be nice to know if it will work before spending the time to build custom shelves, run wire etc.

Thanks much for any input on this setup,

Labrat

unc2701

Probably sound about the same, but with more diffusion. I'd suggest you find something to sit the speakers on, run some cheap cable to them and see how it works out before you go through the trouble of running wires, shelves, etc.

labrat

Just because I am curious, does anyone know how this setup would sound different than ProLogic IIx? Does IIx send the same signal to the left rear and side surround? Would the lack of power on the surrounds be noticable?

Thanks much,

Labrat

mantis

NO,

Your receiver would see a 4 ohm load when pairing up 2 speakers on one binding post.

NO,

7.1 and 5.1 are not the same. the 6th and 7th channel are discrete. (Mono in use) They are an actual recorded channel.The 6th and 7th channels are considered the 6th channel using one or two speakers. Center surround or surround back.

If you want to connect 2 more speakers to your exsisting receiver safely , I suggest you purchase a 2 way speaker selector box. This will show the receiver 8ohm load and you can turn on and off both pairs as you wish or run both at the same time.

Dan

beardog03

mantis

In your opinion would this selector box affect the SQ ?

jarros

Originally posted by mantis
NO,

Your receiver would see a 4 ohm load when pairing up 2 speakers on one binding post.

NO,

7.1 and 5.1 are not the same. the 6th and 7th channel are discrete. (Mono in use) They are an actual recorded channel.The 6th and 7th channels are considered the 6th channel using one or two speakers. Center surround or surround back.

If you want to connect 2 more speakers to your exsisting receiver safely , I suggest you purchase a 2 way speaker selector box. This will show the receiver 8ohm load and you can turn on and off both pairs as you wish or run both at the same time.

Dan

You're right about the 7.1 having a discrete rear center channel (at least for movies with encoded DTS ES or DD EX), but you misread his original post about wiring the speakers. He said he will wire the speakers in series, which will add the impedances of the two speakers, giving him 16 ohms. I don't think this should be a problem. Take a look at this diagram to get an idea of what wiring in series does:



As for DD ProLogicIIx, I'm not sure about how they manage their rear surround channels. I imagine the rear surround channels can't be too different, because in many cases the signal source is stereo.

labrat

Thank you jarros, that is the proposed connection. I don't think this cheapy AVR would handle a 4 ohm load at the spring clips. (binding posts? What binding posts? - remember the thing about the cheap AVR)

I know that 7.1 sources have discrete channels but they seem few and far between. Most of the time we end up with neo 7.1 derived either from a stereo source or a 5.1 source. Does anyone know if there is a difference in the signals to the side and rear surrounds when running a neo 7.1? Any input as to if it would be worth it to use four direct radiating surrounds (neo 7.1) or stick with two (5.1)

Thanks to all for your input,

labrat

John K.

Scott, the answer to your questions is not necessarily. Just in case that you'd like something a bit more specific, a little terminology and technology can be discussed. Although there of course are 7.1 speaker setups, there is no 7.1 format or "source". The most "real" discrete channels are the 6.1 in relatively few DTS ES Discrete DVDs. DD EX and DTS ES are 5.1 but have information matrixed into the side surround channels which can be processed and extracted to be sent as a mono back surround signal to one or two back surround speakers. The reason why Dolby, THX etc. recommend two speakers although it's only a mono signal is to avoid a psychoacoustic effect in which a sound coming from one speaker directly behind the listener can sometimes "reverse" and appear to come from the front.

Now as to whether a 7.1 receiver would merely duplicate the sound of the side speakers in the back speakers, this would be the case in some modes. For example in "all channel stereo" the front speaker would be duplicated in both the side and back speakers on that side; another example is that some 7.1 receivers playing a 5.1 DVD will send the same side channel sound to the back speakers in a 7.1 setup(this is, in effect, what you're proposing to do and can be pleasant, especially if the speakers are at least 3-4' behind the listener).

However, processing such as DPLIIx and Logic 7 doesn't send the same signals to the back speakers. Just as DPLII does in processiing two channel material, i.e. takes the ambience present in two channel recordings in varying degrees and steers it to the sides where it belongs and sounds a little more natural, DPLIIx in addition processes the discrete 5.1 side channels. The surround information is distributed in different proportions over four rather than two surround speakers. Hard left and right material stays in the side speakers, but material having a left of center balance is extracted and sent to the left back speaker while material having a right of center orientation(sounds better to me!)is sent to the right back speaker. The result is a smoother and more stable surround effect.

So, just duplicating the side speakers in back would probably be pleasing to you(note that in theaters when the movie is 5.1 without DD EX back surround information, the back speakers also just duplicate the same left and right side surround material), but wouldn't give the same results as DPLIIx or Logic 7 in a 7.1 receiver. As unc suggested, you might try a temporary setup first to see how you liked it.

labrat

John,

Thank you very much for the explanation. You have no idea how much I appreciate getting a detailed explanation so I can make more informed decisions on set up.

Scott