Meridian Unplugged - Powered by MrTechGuy.co.uk Forums Discussion Meridian - Systems C61R - EBA sync problem with EBA and legacy speakers

Playing with speaker distances within the configuration program doesn't solve the EBA sync problem for my legacy subs, sides and rears using a C61R surround unit.

It appears that, due to memory/processor limitations, software only allows pushing distance (and therefore delay timing) to 27 feet max - when I would need a distance of at least 38 feet if I understand the EBA delay in my front left, right and center 5200SE speakers.

I can reduce the distance to my sides and rears in config by as much as 6 feet to narrow the gap further, but can't actually get in sync without some sort of divine intervention from Hitchhikers who, unlike myself, really understand these issues.

My fronts, including analog subs, are located 16' to 18' away from the sweet spot, while DSP sides are approx 7' and DSP rears approx 8.5'. Sides and rears all have firmware with "unified latency."

Please help me to get surround sound working properly!

While I have endeavored to assist my fellow hitchhikers with any knowledge that I could contribute to their various questions over the years, I am frustrated that no one has bothered to address my repeated concerns over reconciling EBA delay in front SE speakers with legacy surround equipment.

Am I misunderstanding the situation?

Is this not a real issue?

Why hasn't anyone suggested a digital delay device to sync the system?

Am I wrong to think that this forum is dedicated to optimizing the Meridian experience?

In a mixed system, turn EBA off I would think. I only have two channel now and I won’t go surround as I haven’t any more EBA speakers or the monies to buy them.

As I understand it, EBA isn't an overall delay, but a variable delay based on frequency. Therefore an external delay device would not solve your problem. The only non-EBA speakers compatible with EBA speakers are DSP3200s, which have an EBA compatibility mode, but not actual EBA. I use them as my rear channels in my living room system and they work fine.

A system with non-EBA compatible rear speakers will not sound acceptable with EBA enabled in the front channels. It must be disabled (as you've discovered)

John

Hi ODC

My DSPs are non EBA, so for those of us in a similar position who may wish to help, can you describe the practical problem as it currently stands in your system?

I get that the fronts are out of sync with the rears and sides, but can you describe in more detail please? Are the rear and sides channels (and their respective signals) actually running ahead of the fronts?

I do remember that there was a trade off between the amount of lipsync and the speaker distances (or was it MRC filters?) due to processing power limitations. I'll wait to hear more from you before any futher suggestions.

Cheers

George

Thanks, everyone, for restoring my faith after suffering silence since my first appeal for help back in October.

This issue was discussed here when EBA was introduced and found to delay music by approx 25ms compared to legacy DSP speakers with the latest "unified latency" firmware. Some people said that surround listeners should simply turn EBA off (no thanks), while others offered possible solutions for the loss of coherent soundstage. Because delay settings in the config program did not have enough range to be effective, Ludwig suggested a workaround:

Believing that a speaker running EBA firmware has a latency of "26/27ms" (that's the most recent I heard from M) I simply added a distance equivalent to that amount of delay, to the FRONT speakers in Mconfig. This is a bit counterintuitive, but is correct: if the fronts are further away, the sound therefore being delayed, thus the rears need to be fed sound delayed relative to the fronts, which is what we want.

The calculation I used (with 343m/s as the speed of sound through air at 20C plucked from Wikipedia) is this:

343m/s x (0.0265-0.0075) = 6.517m = 21.38ft which I'll call 21'6".

The 0.0075 is the 7.5ms unified latency of pre-EBA firmware and legacy speakers.

My measurements are in fact 8'6" to the three fronts, and 4'6" to the rears. So I added 21'6" to the front distances, making 30' for each of the fronts. Configured and the processor accepted this without question.

Later that year (2014), M did introduce a firmware fix to align EBA/non-EBA speakers for 861v6 and 861v8 (which seemed to quiet the discussion), but no joy for older processors like mine. -And I am unable to add enough distance to my front EBA speakers in config to implement Ludwig's workaround.

Also, I don't get John's explanation for why a multichannel digital delay device between my C61R and legacy DSPs couldn't sync everything except my analog subs -if I could find an affordable 24/96 solution.

Has anyone discovered a practical answer during the past five years?

The reason a digital delay device won't work is because EBA delays only certain frequencies - not the entire signal, like lipsync does. EBA is a method of digitally time-aligning the speaker in a way that is far more precise than just aligning individual drivers (as each driver carries a wide range of frequencies. Frequencies are delayed "on a curve" and not a consistent amount.

A digital delay device, like lipsync, will simply delay all sound from a given speaker.

I hope that's more understandable.

below is a Meridian "blurb" about EBA:

High or low, all sounds travel at the same speed, so all the sounds from a live musical event arrive at your ear at the same time, whatever frequencies they contain. Loudspeakers, however, have a problem when playing low frequency sounds at the same time as mid and high frequencies – the bass arrives late, and the deeper the sound, the later it arrives. This delayed bass causes music to lose its impact and reduces the sense of the recorded space – it is often described as “boomy”.

The goal is to have time-accurate loudspeakers, where all reproduced frequencies start and end at the same time. In a loudspeaker, this timing is affected by the crossover, driver, and enclosure 
type. To eliminate the delay between low, and mid and high frequencies, Meridian has designed a combination of digital filters and time delays for the mid and high frequencies. This solution enables the mid and high frequencies to “wait” for the low frequencies, delivering perfectly-timed music playback.

Mid and high frequencies are delayed to time-align them, while upper bass is delayed with a special type of patented filter. These features must 
be implemented entirely in the digital domain, making them impossible to achieve in any passive or analogue-active loudspeaker design.

Enhanced Bass Alignment provides accurate time-alignment of the drivers in the system, delivering exceptional imaging and a clear, transparent, more life like sound.

John

Hi John,

All correct, but ODC in this scenario needs to delay the non-EBA speakers so that they end up in sync with the EBA ones.
(While the EBA speakers time-align their drive units in the EBA process)

I think ODC idea should work fine.

ODC, how about a Felson DD740 delay box, works at 96/24.

You'd need one per pair of channels.

Rick

Thanks Rick,

My surround unit has SPDIF outputs that combine Left & Right to be sorted by the DSP pair. How can I provide the required two RCA inputs to the Felson in order to get two delayed SPDIF signals out, one for each channel?

I suppose that I could also buy two Meridian SpeakerLink-to-SPDIF adapters for the rear pair, direct the combined C61R coax to my AC11 (which I now use to feed new SL SE fronts) for conversion to discrete L/R SL outputs, use the adapters to get back to SPDIF coax that the speakers can accept, insert the Felson in the signal path and then re-wire 75ohm coax up through the ceiling to each DSP33...

- Or am I not seeing the forest for the trees?

Just a question but why would you need to delay the left and right channels separately?

I could see having to delay sides and rears separately. Are the rears placed asymmetrical from the listening position? If so, a simple Y cable before the delay box will do the trick as the speakers know which signal be it left or right that they respond to.

Hi Bruce.

Yes, you are seeing this more clearly than my rabid over-thinking.

I wouldn't even need a Y cable. Just send the combined L/R coax output for the sides or the rears to a Felson DD740 which will delay everything and pass it bit perfect to the existing daisy-chained wiring for the two speakers to sort out which channel is which as they have always done. (And a second Felson for the other pair.) Thanks.

BTW, does a Y cable on an SPDIF signal change the sound in any way? Aren't you altering the ideal 75ohm connection?

Maybe, but then we are possibly picking at microbial nits. For this we have to place a priority on the least of evils:

A very small delay concern with the non EBA enabled speakers.

A impedance concern using a Y cable.

Non EBA speakers doing what non EBA speakers do, muddy up the midrange.

You need to prioritize on what is most important to you.


Honestly in the vast majority of multichannel audio, the minute differences between audio delay in EBA speakers versus non would be most evident when the Mono DSP preset is used and party mode is enabled. In this scenario, all speakers would be receiving the same content at the same time. This is where I feel the delay problem with G series would be most evident albeit in very small doses. In most cases where the multichannel signal received by each speaker can be vastly different, I feel these differences would be difficult for most to hear. We have spent a ton of cash for our gear and I get that we expect the most from it. It just depends on how far down the rabbit hole you wish to go. JMO YMMV etc.