SINGLE rear amp/speaker for surround sound – Y cable combining L&R rear

robert_kc

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I’m currently using the analog RCA line-level outputs from an Oppo BDP-95 universal player for a 2.1 configuration (i.e., front L&R, subwoofer). No AVR - I use vintage tube amps.

I’m considering adding a center channel, and 1 speaker for the rear channel. (I don’t have room for 2 rear speakers.) I’m considering using a Y cable to combine the L & R rear channel line-level outputs from my Oppo BDP-95, and connecting it to a mono tube amp and rear speaker.

I mostly listen to classical music, including some SACDs that reportedly feature surround sound. And occasionally Blu-ray movies.

Independent of a theory that I’ve read that a “Y cable” should not be used to combine stereo line-level outputs from a CD player into a mono amp, I’ve done this with no problems for many years. IME.

My question is this: Do you anticipate any problem with combining the L & R rear line-level outputs from an Oppo BDP-95 via a Y-cable into a single mono tube amp?

Is there worthwhile rear channel content in 5.1 classical recordings, and separately, Hollywood movies? Is there a difference in rear L vs. R for classical recordings? For Hollywood movies?

Thanks
 
I don't think you'll have a problem doing that for rear channels. The main concern with doing it for stereo sources is that it may force the two channels into mono, compromising the main channels. Rear channel content in most classical surround recordings is just ambiance, so L/R differences are probably not important. For movies made in the last 20 years, there is definitely a difference between rear L vs. R. Nevertheless, a single rear channel may be better than just 2-channel - there's usually some related L/R difference in the main front channels that may provide clues for interpreting a mono rear channel.
 
I don't think you'll have a problem doing that for rear channels. The main concern with doing it for stereo sources is that it may force the two channels into mono, compromising the main channels. Rear channel content in most classical surround recordings is just ambiance, so L/R differences are probably not important. For movies made in the last 20 years, there is definitely a difference between rear L vs. R. Nevertheless, a single rear channel may be better than just 2-channel - there's usually some related L/R difference in the main front channels that may provide clues for interpreting a mono rear channel.

Thanks RichPA - your comments are very helpful.
 
I’m currently using the analog RCA line-level outputs from an Oppo BDP-95 universal player for a 2.1 configuration (i.e., front L&R, subwoofer). No AVR - I use vintage tube amps.

I’m considering adding a center channel, and 1 speaker for the rear channel. (I don’t have room for 2 rear speakers.) I’m considering using a Y cable to combine the L & R rear channel line-level outputs from my Oppo BDP-95, and connecting it to a mono tube amp and rear speaker.

I mostly listen to classical music, including some SACDs that reportedly feature surround sound. And occasionally Blu-ray movies.

Independent of a theory that I’ve read that a “Y cable” should not be used to combine stereo line-level outputs from a CD player into a mono amp, I’ve done this with no problems for many years. IME.

My question is this: Do you anticipate any problem with combining the L & R rear line-level outputs from an Oppo BDP-95 via a Y-cable into a single mono tube amp?

Is there worthwhile rear channel content in 5.1 classical recordings, and separately, Hollywood movies? Is there a difference in rear L vs. R for classical recordings? For Hollywood movies?

Thanks

You CANNOT do this. IF you need to combine channels - use mixer. They can be found cheap (usually start with 4 input channels) in pro-audio stores.
 
I think those who say you can't do this should include an explanation: The technical advice not to do this with a y-cable is based on each channel trying to drive the other as if it were an input, which can result in excessive current draw because of the low impedance presented by each output. But in practice, with preamp level signals, if often works fine, as the OP notes from his experience.
 
I think those who say you can't do this should include an explanation: The technical advice not to do this with a y-cable is based on each channel trying to drive the other as if it were an input, which can result in excessive current draw because of the low impedance presented by each output. But in practice, with preamp level signals, if often works fine, as the OP notes from his experience.

Because it screws up the stereo separation on the part presumably wished to be still in stereo (as you said previously). And, I think in some cases there is possibility of damage. Slim, perhaps, but possible.

"Can't" I think is a bit of a misnomer in this case because surely you physically can. Whether you should is a different matter; with shouldn't being operative IMO.

http://www.rane.com/note109.html

Maybe a Hafler-type arrangement (rear speaker connected across amplifier L+ and R+, to produce the difference) would be better to incorporate for a rear/center speaker if the amplifier can go that way.
 
Maybe a Hafler-type arrangement (rear speaker connected across amplifier L+ and R+, to produce the difference) would be better to incorporate for a rear/center speaker if the amplifier can go that way.

This! :thumbsup: No need to worry about Y-cables. Just use a normal stereo RCA cable, and then feed the out-of-phase content, to the rear speaker, as noted above. No risk, and it's a proven method.
 
Thanks for everyone’s input.

I had a “duh” moment (i.e., an epiphany) yesterday regarding my question: “Is there worthwhile rear channel content in 5.1 classical recordings, and separately, Hollywood movies? Is there a difference in rear L vs. R for classical recordings?” I realized that I can connect my stereo amp and speakers to the L&R rear outputs on my Oppo player and listen to what “rear” content (if any) is included in various classical recordings. I imagine that RichPA is right, it’s probably sound from the rear of the symphony hall – perhaps some (hopefully natural) reverb sound? I’m concerned it may be largely audience noise. (I hate audience noise, and I hate it when the engineers boost the level of applause in live recordings.) I’ve read about a few classical recordings where musical instruments are behind the listener. (IIRC, I read about a recording of a pipe organ that has racks of pipes installed all around a church, recorded with full range audio coming from the rear speakers. But I think this type of recording is very rare.) Bottom line, sometime in the next week or two I’ll connect my stereo to the L&R rear connections on my Oppo player, and listen to the content in a variety of recordings in order to discover if I think the content is worthwhile, vs. a 2.1 downmix that I’m accustomed to. My understanding is that my hi-res (24bit/192kHz) FLAC classical recordings (HDTracks) are 2 channel, but many of my SACDs are described as multi-channel. And, many Blu-ray classical and opera videos are described as multi-channel. (I’m not interested in using a DSP-based surround-sound pre-processor to generate artificial surround-sound from 2 channel recordings.)

Similarly, I’ll connect a mono amp to the center channel and listen for content on various multi-channel recordings. (Apparently even some 1950s RCA Living Stereo recordings were recorded in 3 channel, and the SACDs deliver 3 channels if played in 5.1 mode.)

I’ve read the “Why Not Wye” article several times over the years. Candidly, I’m somewhat skeptical about this article – but I’m not a technician - which is why I’m asking for others’ experience and expertise. I understand that if you connect a Y cable to the Tape Monitor output of an amp (e.g., to connect a subwoofer), then the main speakers might become mono (i.e. lose stereo separation). I don’t do that. (My Oppo universal player derives the subwoofer channel via its bass management software, and provides a line-level subwoofer connection.) In terms of electrical safety – or “frying” equipment – since I’m talking about line-level outputs – it seems to me we’re talking about low-power signals (unlike speaker outputs, which I would never combine). And I’m not talking about tying together outputs from 2 different pieces of equipment, which would tie together grounds. Bottom line, I’ve used Y cables for years to sum the stereo outputs of CD players for a mono tube amp. I currently use that arrangement in my bedroom system (Fisher 500 mono tube receiver) for both a CD player and a Chromecast Audio, and it works satisfactorily – sounds good - and no smoke comes out.

First, I must decide if 5.1 surround sound is worthwhile for classical music. Or, perhaps 3.1 – i.e., front L&R, center channel & subwoofer - and simply not connect the rear channels. (I have the impression that some people use 3.1 because they have no room for the rear speakers, or it’s inconvenient to run wires. How much worthwhile content are they missing?) Or just connect one rear channel. Or connect both rear channels via a Y cable (or via a “summing” circuit). (The software in my Oppo players (UDP-205, BDP-105, BDP-95) support stereo, 2.1, 5.1, and 7.1, but unfortunately they do not support 3.1.)

One of the things that is driving my questions is that I’m considering getting new stereo speakers in my basement system, and rather than selling the old speakers, I might redeploy one speaker as a center channel, and the other as a rear channel. I currently have mismatched stereo speakers – one Klipsch RF7 and one RF-7 II (plus a Klipsch R-115SW subwoofer). I’m considering buying another pair of RF-7 II, and redeploying my existing RF-7 II as a center channel (driven by a mono tube amp), and redeploying the RF-7 as a rear speaker (separate mono tube amp). Or, just buy one RF-7 II, and use my existing RF-7 as a center channel, and no rear speakers. In this basement system, my stereo speakers are 12 feet apart, so a center channel may deliver benefit (assuming a recording that has center channel content). For me, part of the madness of this hobby is always wondering if I could realize significantly better sound … would a center channel deliver benefit for surround-sound classical recordings … would rear channels deliver benefit … a second 15” subwoofer … :)

Please continue to contribute your comments.

Thanks again.

Robert

P.S. Separate question: Am I correct that there is low probability of a problem is I use a Y-cable to split the RCA line-level subwoofer output of my Oppo universal player to 2 subwoofers? (My existing Klipsch R-115SW subwoofer in my basement system does not have a daisy-chain connection.) I like using the Oppo’s bass management software, because it provides a crossover before the main tube amp and speakers, off-loading the power-hungry deep bass from the main amp and speakers (vs. a “double bass” configuration), thereby improving dynamics during fff passages.
 
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Just go into your receiver's speaker configuration menu and specify you're only using one rear speaker. Connect up a speaker to the one channel you selected. I do believe your receiver will correctly "merge" the two rear channels into that one speaker.

Also, unless you're playing recordings initially recorded in multi-channel mode, what you get from the rear channels isn't real. It's just stuff your receiver's DSP thinks should be back there.

About the only "real" current 5.1 music recordings* are on SACD, and there aren't that many of them.

* I think DVD-Audio did also but that format went the way of Sony's Betamax..
 
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Thanks Skipper - but I use vintage tube amps. (No AVR.) My Oppo UDP-205, BDP-105, and BDP-95 provide the only audio processing functions in my systems (e.g., 2.1 downmix, bass management). The software in my Oppo players support stereo, 2.1, 5.1, and 7.1, but they do not support 3.1. And the Oppo's configuration of rear speakers is both, or none (i.e., the Oppo software apparently doesn't support downmixing the 2 rear channels to one).

Sometime in the next few weeks I'll do some experimenting with some of my SACD and Blu-ray classical recordings that feature surround sound, to determine how much content is in the center and rear channels. Then I'll decide if rear speaker(s), and a center channel, are worthwhile for the music that I listen to.
 
FYI, following is my Q&A with Oppo.

Question:

“I own UDP-205, BDP-105, BDP-95, DV980H.

I currently use analog audio outputs in 2.1 configuration.

I'm think of expanding one of my systems (BDP-95) to 5.1, however I can only accommodate 1 rear speaker. Can I use a Y cable to combine the L&R rear analog audio outputs to one amp and speaker? Is there a better way to implement a surround sound system with only 1 rear speaker?”



Answer:

“Yes, you can use a Y-cable to take the Surround Back channels and make them into a single Surround Center connection.”


This answer matches my successful experience with using a Y cable to combine stereo L&R channels from a CD player into a mono tube amp.

While a single rear amp/speaker is technically possible, for me the question remains whether surround-sound is worthwhile, considering that I mostly listen to classical music and watch opera – not Hollywood action movies. Today I configured the Oppo BDP-95 in my basement system for 5.1 and connected an amp and speaker to the rear channel. I listened briefly to several SACDs and Blu-ray classical recordings that feature surround-sound. I found that there is very little rear-channel content - mostly some mild reverb in the symphony hall. Same with opera. The few Hollywood Blu-ray movies that I own have only a small amount of rear channel content.

This has been an interesting experiment, but for now, I think I’ll stick with 2.1.
 
Bear in mind for 5.1 setup you need to use the side/surround outputs regardless whether the surround speakers are to the side or behind the listening position.

The "back" surround outputs are for 6.1 or 7.1 surround, not 5.1.
 
I agree that the Hafler setup can be great, but I don't think the OP is trying extract surround information from stereo, he's trying to play the recorded surround tracks through a single speaker.
 
I use the Oppo UDP-205’s 5.1 downmix setting. IIRC, on the Oppo the “rear” connections that are used in a 5.1 configuration are labeled SL (Surround Left), SR (Surround Right).

As part of my investigation, I connected a stereo amp and speakers to the SL (Surround Left) and SR (Surround Right), and heard little rear content (a small amount of “hall reverb”), and little distinction between L&R, when listening to my classical SACDs. I therefore I decided (at least for now) that I’m not missing much by combining the rear channels.

I’ve only had my “surround sound” installation operating for two days. Thus far, it sounds great for my surround-sound classical SACDs. Because there is so little rear channel content on 5.1 classical SACDs, combining the rear channels sounds OK to me.

The left, center, and right speakers are identical (Klipsch RF-7 II). (I already owned one RF-7II, and like it – particularly for opera - so I decided to buy 2 more.)

The rear is an earlier version (RF-7) of the same Klipsch speaker. (I already owned this one.)

Multiple factors contributed to my decision to have a single rear speaker (at least initially):
  1. I already have a shelf where the RF-7 can be laid on its side, and that’s the only place where it’s practicable to install a rear speaker (or 2 small speakers side-by-side), based on room layout and my listening position.

  2. I don’t watch action movies. I will use this “surround sound” system to listen to classical music. Based on my limited testing thus far (an important qualifier), the classical music that I enjoy typically has little rear channel content, and there seems to be little significance to right vs. left rear content (hall sound). I therefore decided that I’ll start with the rear L&R channels combined into one speaker in the rear.

  3. I already owned the RF-7. If I were to sell an “orphan” (single) speaker, I wouldn’t get enough money to buy 2 top quality rear speakers.

  4. With a total of 4 channels (plus subs), I can use 2 of my vintage stereo tube amps. My other option would have been to keep a mono tube amp for the center channel – but I I’ve run out of room. I’ve therefore decided to sell most of my mono amps

Subwoofer: I’ve just added an SVS SB16-Ultra (i.e., the sealed cabinet model). I have an existing Klipsch R-115SW in this system, and I’ll have to decide if it can play a useful role, or if I’ll sell it. My initial impression of using both is positive.

P.S. This sounds fabulous in surround-sound.

71KTz3qcXWL._SX522_.jpg
 
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