Sub woofer outputs

[ef37a]

It is I know for a single sub woofer output, from say a controller, to be a mono sum. However, where two (RCA) outputs are provided would it not be usual for these to carry left and right signals, especially when the product handbook shows the option of two sub woofers? The mono/stereo selection being effected in hard or software.

Dave.

[Hugh Robjohns]

I've no idea of the context, but some hi-fi preamps provide separate left and right low frequency signals for subs.

And most subwoofers provide two inputs with internal mixing to mono.

[ef37a]

Denon AVR S770H Hugh. Dopey bought it on the strength that it had many of the functions I needed, six HDMI ins to one, TV out. Couple of RCA analogue stereo inputs. S/PDIF and, rare this, MM phono inputs. I saw two RCA "pre outs" and thought I could use those to drive my speakers but not in mono!

I am in contact with Denon. Haven't penetrated to anyone technical yet but I am hoping the routing of the two sub outs can be hacked to deliver L&R? Worse case they are hard wired in parallel.

Last resort in the making is a "sniffer" in the HDMI feed to the TV which then sends its RCA outs to a balanced line diver and ultimately an Audient Nero.

Dave.

[Hugh Robjohns]

I saw two RCA "pre outs" and thought I could use those to drive my speakers but not in mono!

Ah... no... now I know what you're talking about I checked the manual and its quite explicit that both outputs carry the same (summed mono) signal.

I dont see any way of deriving outputs to feed your speakers unless you're willing to perform some surgery on it.

I am hoping the routing of the two sub outs can be hacked to deliver L&R?

I think you'd stand more chance of finding unicorn poo at the end of a rainbow! That's not the kind of thing Denon are going to be able or willing to do.

Last resort in the making is a "sniffer" in the HDMI feed to the TV which then sends its RCA outs to a balanced line diver and ultimately an Audient Nero.

You know the audio channels in the HDMI cable are digitally encoded within the HDMI data stream? A "sniffer" will need to be an active HDMI splitter and decoder/D-A converter.

[tacitus]

I’ve used a couple of audio extractors for HDMI - one is just an audio decoder, the other is a 3-way HDMI switch that happens to yield an audio output. Both sound fine, but I haven’t used them on top systems.

I haven’t thought this through, but might it be possible to plonk something like a WiiM unit in the HDMI output and hijack the audio that way? I seem to be able to do quite a lot with my WiiM amp …

[ef37a]

Thank you Hugh. I am sure you are right and the Denon cannot be modified by software. I did have the top off (shush! Warranty) and NO FRIGGIN WAY am I delving into that jungle of SMT and ribbon cables!
If/when Denon come back with a no I can at least point out the error of their way! Ok just MHO but if you provide two sub outs, in my book they should be stereo. Even fixed level 'tape outs' would do but no show. My fault. I have told people many times in the past RTFM!

Digitally encoded audio in HDMI? Yus, know that, got a "Porta" HDMI converter. comes out at CVBS and L&R on RCA. Not THE best solution I grant you but better than the headphone from the AV I bet? At least I have S/PDIF from CD into the Nero so that's pretty good? And the output of my M4.

Dave.

[Wonks]

Sub crossover frequency is 80Hz, so no directional stereo information carried in that (as opposed to say 125Hz) so no point in stereo sub outputs.

[ef37a]

Sub crossover frequency is 80Hz, so no directional stereo information carried in that (as opposed to say 125Hz) so no point in stereo sub outputs.

I thought this might crop up! We don't get directional clues from VLF in even fairly big rooms but we do in 'king big ones and outdoors. Since the L/R signal is already there and you need at least a resistive mixer to get the mono, IF you are providing two RCAs why not leave it stereo? (surely there could be a mono option in the setup menu? This Denon does all sorts in there!)

Then, I think all the subs I have seen reviewed in the mag take L&R full bandwidth, pass it on then mono and filter.

Dave.

[Wonks]

But if the main source material (video and TV) only provide a mono sub signal, what point is there in stereo? And that particular AV system isn't designed to go in effing big rooms.

I've been in effing big rooms with effing expensive sound systems and you are looking at 19" racks with multiple big power amps in.

[ef37a]

But if the main source material (video and TV) only provide a mono sub signal, what point is there in stereo? And that particular AV system isn't designed to go in effing big rooms.

I've been in effing big rooms with effing expensive sound systems and you are looking at 19" racks with multiple big power amps in.

OK! So I am hissed off I bought wrong. No need to rub it in. (I was just pointing out the science)

Dave.

[Hugh Robjohns]

If/when Denon come back with a no I can at least point out the error of their way!

I'm not sure that buying the wrong tool for the job can be claimed as their error....

... if you provide two sub outs, in my book they should be stereo.

Yes and no. I've seen both mono and stereo sub feeds on different products, but mono is much more common. ...and they're normally low-pass filtered, too. Nothing above 85Hz or so.

There is, arguably, a benefit to having very low frequencies in stereo in open space and ridiculously large auditoria.. but not in the vast majority of domestic spaces. Even the largest cinemas run low frequencies purely in mono. The wavelengths involved are too big and the reflections too strong to do anything else.

Having two sub outputs is unusual in my experience, but being able to hook up two subs can often help resolve standing wave issues, so I can see why Denon have provided the facilities they have.

Even fixed level 'tape outs' would do but no show. My fault. I have told people many times in the past RTFM!

Quite so...

I was initially surprised at the absence of a tape outs but, thinking about it, what would they feed? No one records analogue audio anymore. In a world of instant streaming and personal playlists, who would bother to record anything manually?

My Bryston BP17^3 hi-fi preamp doesn't have dedicated tape outs, either... but it does have both fixed and variable outputs on both unbalanced RCA-phonos and XLRs — making it very simple to hook up all sorts of other gear and active monitors for testing. Which is why I bought it.

Digitally encoded audio in HDMI? Yus, know that, got a "Porta" HDMI converter. comes out at CVBS and L&R on RCA. Not THE best solution I grant you but better than the headphone from the AV I bet?

Fair enough... I was just concerned you hoped to break into the HDMI cable...

[ef37a]

" No one records analogue audio anymore. "Well I 'could' ! I have a working MD recorder* and I could of course feed the M4. Even S/PDIF out would have been handy.
No matter I can live with the kludge.

*A Grundig by crikey!

Dave.

[Hugh Robjohns]

" No one records analogue audio anymore. "Well I 'could' !

Yes, so could I... but we're not typical Denon customers, are we?

The typical customer for that kind of product is someone who wants to listen to Netflix in surround. End of story...

[ef37a]

".. I was just concerned you hoped to break into the HDMI cable.."
Cheeky bugger!

Netflix do surround sound? I have absolutely no interest in that. I was around for the first 4 channel s'storm where a half dozen companies tried to corner the market resulting in a total meltdown because Joe pub just lost interest.

I would have been interested in a system that could recreate the acoustics of great concert venues but that seems to have gone a bit niche?

Dave.

[ef37a]

I have had a new response from Denon (do you think "Zuzana" might be an AI bot?)
"Just use the Pre Outs to drive your active speakers" The email then goes on to speak of "amplifier Align". A deep dive into the manual gets me to 'Setup>Audio" but "Sub woofer level adjust" is greyed out as are two other functions. I have done a reset to factory defaults but that did not restore them.

There are more settings for the sub outs but I cannot access them.

Told her/them/it.

Dave.

[ef37a]

I have had a further email from Denon and, as suspected, it is not possible to modify the sub outs to full bandwidth L&R. There are sub parameters that can be changed but that function and others are greyed out. Another email!

Surprisingly they have offered the notion that "a Molex connector could be tapped" but of course, strongly advise against such a mod! However I shall press them for details as it seems to me that I could make up a "break in" Molex to Molex cable and extract controlled audio. With care the unit could be put back to factory state and no one would know should it need a warranty service?

Dave.