[neils]

When I had first built my HT, I created a 7.1 setup in terms of speaker layout. Now, in terms of amplifier channels, I went with 3 stereo power amps (Carver TFM-35x). After reading lots of info about 7.1 (at the time), it was told that the "rear center" which was 6.1 then became 7.1 BUT that the 2 channels were NOT discrete, and were simply mono channels for rear surround (same rear surround signal fed to both channels).

After this point, every receiver and prepro out there were providing 7 channels of sound. So my question is this. Has the 7.1 format advanced to the point that these channels are now considered discrete, and can have different tracks fed to them ??

This of course would become a bit of a pain for a stereo power amp guy like me, where you add channels in pairs. If the channels are discrete, then I might have to get to the point of considering a 7.1 amp rather than going with 4 stereo amps that take up a lot of room.

Looking forward to hearing the answer on this one.

Thanks
Neil

 

[jaddie]

The bulk of soundtracks are still 5.1, which means when an AVR provides 7.1, the back two are extracted from the two surround channels of 5.1. However, there are a few discrete 7.1 channel soundtracks in the world, and when presented with a real 7.1 bitstream an AVR will decode and place the back channels correctly.

Many AVRs will also do 6.1 (mono rear) if only those speakers are provided during auto setup, but it's almost always a downmix from 7.1 or an upmix from 5.1.

It's up to you if you want to place importance on accurately reproducing all surround formats, but be aware that Dolby Atmos is now out there with the potential of up to 34 speaker total. You'll want to read up on that to understand what Atmos is and what it means to you. Right now there are more discrete 7.1 tracks in the world than Atmos discs, but the expectation is for the number to grow. Atmos has a way to both downmix a full Atmos theatrical mix (up to 64 speaker channels) to as few as 9.1 at home. But since it's not technically a discrete system, "downmix" is not actually the correct term, especially in light of what goes on with 7.1/5.1. Atmos will also "upmix" from 5.1/7.1 to as many as you have up to 34.

If you're worried about power amps coming in pairs now, realize it's always going to be an odd number. 6.1 and a couple of Atmos configurations are the exceptions, and nothing is being currently produced in discreet 6.1. Atmos AVRs are the worlds best power amp bargain in terms of channels per $.

 

[neils]

Thanks for the answer, and yes I am very well aware of the Atmos and Aura 3D and even the upcoming DTS work in this area. For now I am letting the format war battle itself out (again) and don't foresee too many people ripping up their finished HT rooms to install these extra channels but I could be wrong, I considered it myself just last week.

Back to the topic, I guess if there are few discrete 7.1 soundtracks out there it is not worth it (right now), dumping my 3 stereo power amps in favour of a 7 multi channel amp.

The issue I have with multi channel amps is power, many do not provide enough power and the Sunfire's of the world with 400w x 7 are few and far between and way more pricey than my 3 stereo power amps.

So in the end, it seems like an expensive venture to move to one of those expensive beasts to accommodate the 7th rear channel. I can't even imagine what folks are doing today to get 9 and 11 channels worth of power.

If any of you are doing a prepro and external amps, would love to hear how you are doing it (# amps).

Thanks
Neil

 

[jaddie]

The issue I have with multi channel amps is power, many do not provide enough power and the Sunfire's of the world with 400w x 7 are few and far between and way more pricey than my 3 stereo power amps.

Yup, pretty hard to be 3 400 wpc stereo power amps for raw power. Never going to find that in an AVR.

Of course, the actual need for such is pretty rare too. Mostly a 125wpc AVR and decent home theater speakers will hit reference level in everything but a huge room, at which point you need different speakers anyway. But I'd never talk someone out of their Sunfires.

If you wanted to add a couple surround channels you don't need 400wpc, surrounds never actually demand that, and often are closer to the LP, further reducing the need. For power demand, fronts are way above surrounds, center beats all by more than 10dB.

 

[neils]

So conclusion to the topic is that for most movie soundtracks, it will probably be a 5.1 source up mixed in the prepro or AVR to either 6.1 or 7.1 depending on rear surround speaker layout. And few movies today offer discrete 7.1 channels, I wonder if that statement also holds true for the newer BD formats DTS-MA, True-HD,etc.

As for moving to a dedicated 7.1 channel amp, I love power, running 250w x 6 with my 3 Carver's and find myself cranking it often. And sub side is even more intense in my setup. So all of the 7.1 amps out today from the likes of Marantz, Onkyo, Bryston, Yamaha, Emotiva etc just does not cut it for me.

But since the 400w x 7 Sunfire is pricey, I might have to consider dumping my beloved Carver TFM-35x (3) in favour of the 200w x 7 Sunfire and pray it holds up when pushed hard.

One thing I like to monitor is channel levels / clipping. I hate these all-aluminum faceplates with power light only. I am not even sure I like the 1 VU meter on the Sunfire. No way to monitor all of the 7 channels, but that is a different topic.

Will stick with my 6.1 layout for now, it sounds like adding the 7th rear surround and the investment in amplifier upgrade that goes with it might not be worth it, audibly at least.

Thanks

 

[jaddie]

So conclusion to the topic is that for most movie soundtracks, it will probably be a 5.1 source up mixed in the prepro or AVR to either 6.1 or 7.1 depending on rear surround speaker layout. And few movies today offer discrete 7.1 channels, I wonder if that statement also holds true for the newer BD formats DTS-MA, True-HD,etc.

As for moving to a dedicated 7.1 channel amp, I love power, running 250w x 6 with my 3 Carver's and find myself cranking it often. And sub side is even more intense in my setup. So all of the 7.1 amps out today from the likes of Marantz, Onkyo, Bryston, Yamaha, Emotiva etc just does not cut it for me.

But since the 400w x 7 Sunfire is pricey, I might have to consider dumping my beloved Carver TFM-35x (3) in favour of the 200w x 7 Sunfire and pray it holds up when pushed hard.

One thing I like to monitor is channel levels / clipping. I hate these all-aluminum faceplates with power light only. I am not even sure I like the 1 VU meter on the Sunfire. No way to monitor all of the 7 channels, but that is a different topic.

Will stick with my 6.1 layout for now, it sounds like adding the 7th rear surround and the investment in amplifier upgrade that goes with it might not be worth it, audibly at least.

Thanks

Love having it, but you're never using it. Sorry
Dolby proved this years ago. The power distribution around the channels just doesn't support the need for equal power everywhere, much less equal full simultaneous power in every channel (ACD). It's nice to know it's there, it will never be used because 70-80% of your total SPL comes from the center, the remaining 4 channels share, unequally, the rest. Even considering brief peak demands, those peaks never appear in all channels at the exact same instant.

Carver's use of VU meters is for show only. I have a TFM15. The meter ballistics are too slow to indicate peaks or clipping, like not even close. In fact, it's only useful for a rough relative voltage measurement with a test tone. There are amps with clip indicators, but even better, clip limiters that gracefully protect the amp from clipping. Indicator or not, that's really what you want if you're going to work an amp that hard.

 

[sdurani]

Has the 7.1 format advanced to the point that these channels are now considered discrete, and can have different tracks fed to them ??

They're not considered discrete, they actually are discrete. With the advent of HD DVD and Blu-ray, discrete 7.1 was delivered on home video. Initially it was studio re-mixes of theatrical 5.1 soundtracks but, beginning in 2010 with Toy Story 3, theatrical soundtracks started being mixed with 7.1 discrete channels. A quick search at Blu-ray.com shows almost 1,200 Blu-rays with discrete 7.1 tracks. Even if half of them are different editions of a title, that's still a lot of 7.1 movies.

 

[4DHD]

From an acoustical stand point, having two rear speakers, even if they are a mono channel is better than one rear channel that is right behind your seat.

As you do have three amps, you really do not need a 7 channel amp..
just replace one of the stereo amps with a 3 channel amp.
And say have a combo of one stereo amp driving the L/R mains;
The other stereo amp driving the side surrounds,
the 3 channel amp driving the center and BS.

Or buy a mono amp. then its having your 3rd stereo amp driving the BS pair and the mono amp driving the center.

 

[neils]

Hey 4DHD,

Funny you say that. My amps are the Carver TFM35x, one driving FL+FR, one driving SL + SR and one driving C + SB (mono to 2 speakers).

Carver actually did make a 3 channel version called the A753x (image below). This would solve my issue to turn my 6.1 into a discrete 7.1, but I would really have to want to stick with a 7.1 setup, which I think I will, and not move to 9.1 and need even more amp channels.

My ceiling is too low for front height, and my room has no convenient walls for front width, not to mention impossible to get wiring to them.

So I might have to remain content with 7.1, and my "big" upgrade in the future is keeping an eye out for a nice pre-owned a753x, which are rare beyond belief.

Thanks guys for all of your input, much appreciated !!

Carver a753x
http://img.canuckaudiomart.com/uploads/large/416475-carver_a753x__amplifier.jpg


Neil

 

[jaddie]

From an acoustical stand point, having two rear speakers, even if they are a mono channel is better than one rear channel that is right behind your seat.

Depending on how close it its, perhaps, but the problem with two spaced rear speakers is that you can't get a reliable solid phantom rear center. Having a hard-center rear channel was the original motivation for 6.1 in theaters, though short lived. Having that location available to mixers was important to generate better "fly-over" effects. In fact, the 7.1 configuration we have at home never existed in theaters. THX attempted to improve the 7.1-home situation with their proprietary processing and somewhat different preferred location for the rears. But, as you know, THX processing is less than common today.

As you do have three amps, you really do not need a 7 channel amp..
just replace one of the stereo amps with a 3 channel amp.
And say have a combo of one stereo amp driving the L/R mains;
The other stereo amp driving the side surrounds,
the 3 channel amp driving the center and BS.

Or buy a mono amp. then its having your 3rd stereo amp driving the BS pair and the mono amp driving the center.

3-channel amps are not exactly thick on the ground, and not cheap either (if you want something similar to the Sunfire), but I like the mono amp idea, or a lower power stereo amp run bridged. They may be more expensive in the home audio market than the pro market, but lots to choose from there, including lots of product under $300. I hesitate to recommend Behringer to a guy who likes Sunfire, but for loafing along in a surround application, it's just fine. Watch out for cooling fan noise in the "pro audio" product lines. The used market might solve this cheaply too.

 

[neils]

Thanks jaddie,

And yes, you are correct, no Behringer stuff in my HT, although I appreciate what they offer in terms of gear for DJs and bands. Logically, if I were to upgrade from 6.1 to 7.1, with my current setup of 3 Carver TFM-35x, I would have 2 upgrade options in sticking with my beloved Carver/Sunfire company.

Purchase a 3 channel Carver A753x, which essentially is a match to my TFM-35x, same power output and VU meters (not sure about sonic quality and build though). Other option would be to move to the more expensive Sunfire 7 channels amps (TGA-7200/7201 or 7400/7401). While I like the compactness of a single 7 channel amp, I do not like the all-aluminum faceplates with no clipping lights or VU meters, looks blah to me. So might consider the a753, especially since they can be had for around $500 on the used market.

I am just hoping that after upgrading to 7 channels worth of amps, that those rear speakers come alive with 7.1 tracks and that I can actually hear the difference. Part of making that happen, I think, is changing the type of speakers I am currently using (Polk bi/di polars) and changing their angle and location. Thinking a pair of good bookshelves, more seperated and aimed at the viewer will sound better.

For reference, my entire basement is my HT room, it is close to 30' deep, with the couch mid center, so I have plenty of room back there for rear surround.

Thanks for all the help !!

Neil

 

[4DHD]

For reference, my entire basement is my HT room, it is close to 30' deep, with the couch mid center, so I have plenty of room back there for rear surround.

Thanks for all the help !!

Neil

Having a room 30ft deep does not guarantee good back surround.
My room is 32ft deep and my seating is 12ft from the front wall and the rear surrounds are 13ft behind the seats, which are 7ft from the rear wall.
And its totally dependent on the surround mix of a movie as to how much sound comes from those rear speakers.

And I find it depends on the surround mode.
Apple TV has DD 5.1, if I want to use the rear channels then I have to use DPLIIx...not my first choice.
If the program is streamed in stereo, then I can use Logic 7...my preferred matix surround...
DTS-ES, that's a whole different thing.

 

[Skytrooper]

Just a note to Neil's. I got a TFM-45, 375w per channel. Amazing how cool it runs with all those watts.

 

[sdurani]

I am just hoping that after upgrading to 7 channels worth of amps, that those rear speakers come alive with 7.1 tracks and that I can actually hear the difference.

Will be easier to hear stereo separation behind you if you spread your rear speakers at least 60 degrees apart (±30° from centre line).

 

[neils]

To 4DHD, I just went downstairs to measure the distance to both front and back, and without the space of my racks, I have about 12' to the front as well as to the back wall where my rear surrounds are located, so spacing is about the same both ways. My seperation needs improving, as they are only about 4'-5' apart, as I mounted them on the same short wall, before it curves off into a hallway. So if I advance them to gain more seperation, I will also bring them too close to my listening position (compared to the fronts), but then again, I am guessing this is all taken care of by Audyssey. Better to have closer speakers delayed then to have them too far away and having to crank them.

To Skytropper, that is another reason why I love the vintage Carver products. They consume little electricity. I remember when I was wiring my HT room, I wanted to stick several 15A circuits in there, and my buddy said hang on, hook it all up and try it out. I laughed, how the heck would 3 X 500w amps plus a bunch of other stuff not trip a single breaker. I wired up all the gear to a power conditioner with an ammeter, cranked the system, and sure enough, was not even drawing 8A, very impressive !!! And they run cool to the touch too !!! I just hope that the A753x 3 channel version has the same sonic quality as the TFM series. But that if for another thread and discussion.

I do think with a good pair of bookshelves instead of bi/di-poles and more spacing between the two and the full 7 channels of amps, I will hear the difference, but as others have mentioned, depends on the source and number of tracks and which soundfield is used to upmix.

Thanks
Neil

 

[jaddie]

To Skytropper, that is another reason why I love the vintage Carver products. They consume little electricity. I remember when I was wiring my HT room, I wanted to stick several 15A circuits in there, and my buddy said hang on, hook it all up and try it out. I laughed, how the heck would 3 X 500w amps plus a bunch of other stuff not trip a single breaker. I wired up all the gear to a power conditioner with an ammeter, cranked the system, and sure enough, was not even drawing 8A, very impressive !!! And they run cool to the touch too !!!

Well, conservation of energy...the amps weren't creating power from nothing, they could pull nearly 13A (probably more) from the AC line, but you won't see that with an ammeter while playing audio because it's a peak demand that the ammeter won't respond to. The ammeter is a slow responding, hopefully RMS, meter, not a peak meter. Also, to pull the full 13A all channels would have to hit full power at the same exact moment which won't happen with anything but test tones.

The Carver stuff was efficient because of power supply design, but the biggest efficiency gains were at idle. That's also why they don't run hot. Many modern amps also do pretty well at this by using modern power supply designs, though they aren't using the Carver trick precisely.

I just hope that the A753x 3 channel version has the same sonic quality as the TFM series. But that if for another thread and discussion.

TFM stands for Transfer Function Modified, in other words, Carver was modeling another amp (Conrad-Johnson tube, if I recall), so no, the A753x3 won't sound like the TFM. He stuck with the model name convention. But it may not matter, these are surrounds, right? No primary content anyway. I personally don't care for the transfer function modeling of my TFM15, so it's not used for anything critical.

I do think with a good pair of bookshelves instead of bi/di-poles and more spacing between the two and the full 7 channels of amps, I will hear the difference, but as others have mentioned, depends on the source and number of tracks and which soundfield is used to upmix.

For smaller rooms I advocate dipoles for side surround, direct radiators for back channels, if you can get some distance away from them. The problem with direct radiators is the audience will localize them as a point source, where surround is supposed to be a diffuse field. At least for film, music is something else again.

 

[ChromeJob]

Innnnnteresting discussion! I remember that I have some DTS-ES Discrete (true 6.1 channels ) and Dolby Digital EX (Surround Back/SBL+SBR derived from Surround Left and Surround Right) films, and would presume that SBL and SBR, if used, are generally mono. In DVD.

I presume that Dolby Pro Logic IIx treats SBL and SBR as a single channel. (I used to use a little SB speaker but discarded it for my current hi-fi living room

Fast forward to DTS-HD MA and Dolby TrueHD...

I haven't seen any BDs (I don't buy a lot, mind you) offering anything more than 5.1 (3/2/0/1) ... I'll have to pay attention to new movies if any of my BDs offer 7.1. I think one of my recent PIxars offered it, now to remember which one....

 

[ChromeJob]

Oh, I daresay that the INTERSTELLAR soundtrack, with Hans Zimmer falling asleep on his keyboard, probably sends inordinate power draw to all the surround channels. On all the forums I follow, people telling of their aural-gasms over the BD.

So much for "you won't need a ton o' sustained power in those surrounds...." (just kidding around)(I haven't played the BD, the movie didn't wow me enough to buy it)