5.1 vs 7.1 system

[cristisabo_28]

Hy everyone.This year I'm beginning my own HT basement project and I'm gathering some info.My option for the audio gear is the Jamo C 80 system(5.1).Lately I have notice that more films with the 7.1 sondtrack are released and I'm thinking of going 7.1 with my audio line.My question is what happens when you play a 7.1 soundtrack on a 5.1 system?Do you loose something?What kind of speakers should I get for rear surround(cheap or expensive)?Is there a real difference between 5.1 and 7.1 soundtrack(sonically speaking)?Thanks

 

[AcuDefTechGuy]

IMO, you don't lose anything.

I've tried 5.1 & 7.1 on some BD that were 7.1 DTS-HD MA. Can't tell any difference.

If you ever feel that your surrounds aren't giving you "enough", just increase the Surround Channel Level +2dB above the front channels.

Now if your room were like 40' x 30' x 15' ceiling, then I can see 7.1.

Unless you also use big towers for surrounds, then 5.1 will be peachy.

 

[Josuah]

Go 7.1 over 5.1 only if your room is large enough for it to matter. In which case the additional rear speaker placement will help with sound imaging behind you.

 

[FirstReflection]

Yes, the decision of whether to go 7 speakers or 5 speakers is determined by the room and your seating position within it.

You need an absolute bare minimum of 4 feet from the back of your seat to the wall behind you before you should ever consider adding 6th and 7th surround back speakers. And you're not gaining anything from those additional speakers at that distance. It's merely the minimum so that the 6th and 7th speakers do not make things sound WORSE.

You honestly need a good 8 feet from the back of your seat to the wall behind you before surround back speakers start to provide any sort of audible benefit. At that distance, you can start to hear a bit of a "hole" in the surround field behind you. Although that is still assuming you have your regular surround speakers positioned directly to either side of your seat. If you have your surround speakers positioned slightly behind the seat, you'll need 10 feet or more from the back of your seat to the wall behind you before 6th and 7th surround back speakers begin to produce any audible benefit.

When you play back a 7.1 channel recording on a 5.1 system, you do not "lose" anything. The 6th and 7th channels are automatically down-mixed into the regular surround channels. So none of the sound "disappears", it just gets redirected into your existing surround speakers. Even if you play it back in 3.1 or 2.1 or 2.0, nothing gets "lost". However many speakers you have, the sound gets down-mixed into them and you still hear all the sound

The purpose of the 6th and 7th surround back speakers is to "fill in" the enveloping surround field when you have a lot of space between the back of your seat and the wall behind you. If you have a large gap behind you, the regular surround speakers might not be able to make it seem as though sound is coming from behind you. So only consider adding 6th and 7th surround back speakers if you have a lot of room back there. They will make things sound WORSE if you have only a 4 foot or less gap. They don't really add anything useful if the gap is 4-8 feet. Only at 8 feet or more would I recommend adding the 6th and 7th surround back speakers.

 

[Calvin Hobbes]

The width of the room could be considered more important. A thirty foot deep room that is only 14 feet wide will not see any benefit with 7.1, if you have the surrounds a bit behind you.

 

[cristisabo_28]

My room is 23 feet long and 14 wide but the seats are 18 feet from the projector screen.I have another question regarding the gauge of the speaker cables.The 2 Jamo C 809 tower speakers will need about 32 feet of speaker cable each.I decided to buy Belden 5000 series cable and I want to know wich gauge should I buy.The 10 gauge or 12?Is there any difference for this distance sonically speaking?Thank you very much

 

[Josuah]

For that distance, use the lowest gauge speaker wire you can that will fit your speaker and amp binding posts. Make sure it will fit.

 

[AcuDefTechGuy]

I doubt you will ever tell the difference between 12g & 10g wires.

I would go for the 12g.

 

[Josuah]

There are some general recommendations listed in Speaker Cable Gauge (AWG) Guidelines & Recommendations. At 30' and 4 ohm speakers they recommend 12awg. At 50' and 4 ohms they recommend 10awg.

If your speakers, at 32' cable distance, might dip below 4 ohms at some point, it would make sense to play it safe and go with 11awg or 10awg. Or you might get different speakers later and it won't hurt to have thicker cables, saving yourself some work.

 

[cristisabo_28]

I can put the player and receiver closer to the fronts and I was thinking of having 10 gauge for the fronts and center and go with the 12 gauge for the surrounds(and have the longest cables for the sur).What do you say?
So,I can pay less for the cables.

 

[FirstReflection]

In practice, 12 gauge speaker wire is perfectly fine up to 40 or 50 foot lengths. Resistance is the primary electrical factor to consider when it comes to speaker wire, so a lower (ie. thicker) gauge copper wire will have less resistance, allowing for a longer run without any signal attenuation. If you want to get REALLY picky and technical, 12 gauge copper wire can start to have the slightest amount of high frequency signal attenuation at about a 20-25 foot length. But actually HEARING any such loss? Highly unlikely. It's pretty debatable whether you'll actually hear the high frequency signal loss with a 50 foot or even longer length. So honestly, I wouldn't worry about it. 12 gauge is already thicker than what a lot of people use

Revel offers some REALLY conservative guidelines in their speaker manuals if you're interested. Check page 16 of this S12 manual for a chart as an example. Just realize you can basically double those distances with no problem

 

[slipperybidness]

If it were my system, I always go with the lower gauge cables, assuming that I can afford them.

In general, I think 7.1 is a waste. As mentioned, only good for very large rooms. Also, there aren't a lot of 7.1 sources available, you are much more likely to find 5.1.

My philosophy on the surrounds is that I don't want to put a lot of $ into them. They don't run 100% of the time and I have a hard time putting money into that. However, I am focused on music first and movies second.

 

[cristisabo_28]

Can I run the speaker cables through the concrete slab?Could this affect the sound quality?I'm talking about Belden 5000 series.Thanks

 

[Josuah]

Can I run the speaker cables through the concrete slab?Could this affect the sound quality?

Surrounding your cables with concrete will not negatively affect the sound quality.