AES/EBU As Output To Monitors?

[John Ludlow]

I'm in the process of setting up a shootout between three sets of upper-middle-class monitors. All of them are powered. Two of them will accept an AES/EBU input. At least one of those (the Adam s3h) will digitize an analog signal before converting it back to analog again if you feed it a balanced signal instead. In theory, staying in the digital domain until the last possible moment, and avoiding the two conversions, seems like a better option. So, I'm investigating that.


SAC seems to at least partially recognize the AES/EBU output from my Fireface UFX+. However, in the list of potential outputs, SAC lists only 'AES L'. Like: not 'AES L-R'. I have never used AES/EBU. I vaguely believe that I know that it is a two channel digital protocol, which would seem to support a stereo signal.


So, here are my questions:


1. Is SAC reporting the output capability of the UFX+ correctly? That is, is there only one channel - or are there actually two (potentially L and R)?


2. If there are two, is it a viable option to the analog stereo outputs to send to powered monitors with an AES/EBU input and output connection? And would I daisy-chain them: UFX+ OUT -> L AES IN -> L AES OUT -> R AES IN - and then somehow select which of the two signals (L or R) each speaker would output using the firmware within the speaker itself?


3. And, if that is the procedure - within SAC, to use it, do I simply select it in the output converter list as I would an output converter?

[MMP]

The AES digital out is a stereo pair on one connector like a SPDIF output. The monitors will take care of the splitting L/R. I think you should be all set.

[John Ludlow]

The AES digital out is a stereo pair on one connector like a SPDIF output. The monitors will take care of the splitting L/R. I think you should be all set.

Thanks, Michael. I'm kind of surprised that these Adams did not ship with a manual considering that they are more sophisticated than a hifi speaker - and also spendy. But, I just found it online (maybe Adam is affiliated with ASUS :-P ). I see that I select AES and then L or R from the firmware from within a truly tiny screen on the back of the monitor.

Do you know whether I can daisy-chain a second set of monitors off the first set? Like: Adam L -> Adam R -> Genelec L -> Genelec R? Or is the signal 'consumed' by the first one that accesses it? And, if so, is there a limit? I don't think I'll do that, but I'm curious to understand whether AES works like a network - just in case I do at some point in the future.

[cgrafx]

If your intent is to compare the monitors, then all the monitors need to be tested with the same signal chain.

You can't use and AES digital connection on some and an analog connection on others as that will completely negate the comparison.

You may also wish to test the difference between the AES and Analog connections.

So if you have three monitors and two of them support AES you'll have 5 configurations

3 analog and 2 digital

[MMP]

I would guess that the AES signal is just being repeated on the AES out, so daisy chaining them should work, but I have no first hand experience with that setup. The fact that each monitor has to be told which side to reproduce leads me to believe the full stereo signal is being output on the AES out.

Thanks, Michael. I'm kind of surprised that these Adams did not ship with a manual considering that they are more sophisticated than a hifi speaker - and also spendy. But, I just found it online (maybe Adam is affiliated with ASUS :-P ). I see that I select AES and then L or R from the firmware from within a truly tiny screen on the back of the monitor.

Do you know whether I can daisy-chain a second set of monitors off the first set? Like: Adam L -> Adam R -> Genelec L -> Genelec R? Or is the signal 'consumed' by the first one that accesses it? And, if so, is there a limit? I don't think I'll do that, but I'm curious to understand whether AES works like a network - just in case I do at some point in the future.

[John Ludlow]

If your intent is to compare the monitors, then all the monitors need to be tested with the same signal chain.

You can't use and AES digital connection on some and an analog connection on others as that will completely negate the comparison.

You may also wish to test the difference between the AES and Analog connections.

So if you have three monitors and two of them support AES you'll have 5 configurations

3 analog and 2 digital

Well - you make a good point. I guess I have to think about that. My original thought was that while the room itself will be identical between them, the optimum settings relative to it won't be the same between monitors. I want to give each one the best chance at being optimal and each have advantages over others in that regard.

For instance, the 8341a comes with the capability to use Genelec's automatic room 'tuning' software that cannot be used with other manufacturer's products - which is an advantage for it. I wouldn't not use it to give the other manufacturers equal footing. It's part of what you're buying when you buy an 8341a. Similarly, both the s3h and the 8341a have an AES input option, whereas the sm9 does not. If not doing that last set of conversions is clearly better - then that's what the monitor should be judged by since you can't get one without the other anyway. And the sm9 has the option of turning it's 3-way system into a 2-way, spectrum-limited, system more analogous to the 'car test', which is an advantage for it. The other two monitors can't do that but I'd still like to test it. And the sm9 has a passive radiator on top, whereas the others do not. As a result, I think it's going to require different tuning for the room. In fact, I presume that each will require different tuning to maximize their potential.

On the other hand, although I am doing this primarily for myself - I am publishing it so that others might get a clearer picture, at least. It's so hard for some people (like me...) to hear monitors in relation to each other within their geographical area. It won't be perfect, but maybe this will help somebody. And not everyone will have an AES option out of their converters. So, I probably should review the six distinct options separately while still keeping in mind that there are ultimately only three that can be purchased.

I do plan to use SAC to quickly A-B-C the same test program material in quick succession because that temporal proximity to each other helps me hear differences and compare. In as much as the monitors cannot occupy the same volume of space simultaneously, they will necessarily have to be in different locations relative to the listener (me...) which could also cause inequities. I have considered swapping the sm9's and the s3h's, which will both be on Argosy 420Xi stands, in mid-test in case that has given one or the other an advantage. But, they are mid-field monitors whereas the 8341a's are near-field, and on the desk, and would not benefit from swapping with them. For that matter, I do not trust the weight of either the sm9's or the s3h's (over 70 lbs each!) on my 'mixing desk' (a cafeteria table that the KU Student Union got rid of in the early 1980's because it was shot).

So... I think you're probably right that I should consider each monitor permutation separately, but there are limits as to how identical the setup for each can ideally be. And we will have to keep in mind that, although my room is treated, it isn't anachoic and will doubtless interface differently with the three monitors no matter what I do. I get why you would want there to be zero parameter differences between them (because in a perfect world that would be ideal for testing) but there probably isn't a realistic way to do that and still review each in their best light. So, we'll all have to keep that in mind. For that matter, the tester doing the comparison will be someone who does not have golden ears and mixes on an ancient cafeteria table. That will certainly take away some of the relevance. All these things add to the salt it must be taken with. Hopefully, it will still be helpful. But, if not - that's unfortunate but... oh well.

[John Ludlow]

I would guess that the AES signal is just being repeated on the AES out, so daisy chaining them should work, but I have no first hand experience with that setup. The fact that each monitor has to be told which side to reproduce leads me to believe the full stereo signal is being output on the AES out.

Good - that's what I was hoping. I'm not sure what I'd do with that capability, but it makes my propeller spin to know it's there. Maybe someday it will come in handy.

[John Ludlow]

For anyone who is wondering, using AES with SAC is as easy as using any other output type. The 'AES - L' is misleading: it outputs both channels. You daisy chain the signal from the source to the first speaker, then out of it to the second one. At least on an Adam, you choose which channel the speaker amplifies by making a selection from a control on the speaker cabinet itself. I've got the Adams belting out Bela Fleck right now to loosen them up.