Meridian Unplugged - Powered by MrTechGuy.co.uk Forums Discussion Meridian - Systems Interesting Discussion 861v6 v ADA

Yes, I think you've nailed it. Never could get subs to work all that well at higher crossover points, particularly in multiples. I'm fortunate to have main speakers that do low bass well, it's just that for whatever reason they nver quite got down below 30 hz. in my room.

Coke>Pepsi

Pepsi>Coke

Here we go again.

Some observations.
Low frequencies (let's pick on 80Hz and lower) cannot be localized by mechanisms of human hearing. When listeners believe they can localize these low frequencies, the localization mechanism is, in fact, the higher frequency artifacts (or the placebo effect) of the subwoofer's generation of the low frequency output (driver slapping the air, etc.). When these high frequency artifacts are eliminated and the listener has no advance knowledge of the physical locations of the low frequency drivers, they cannot be localized. There is therefore no advantage associated with keeping the subwoofers in the same place as the mains. In fact, due to the differences in placement to achieve proper imaging and the modal response characteristics below a room's Schroeder frequency, they cannot be colocated.

Meridian would suggest, using their speakers that speakers (such as the DSP8000s) should be set to large. Let's examine that. The DSP8000s are said to produce 20Hz to 20kHz at 118 dB SPL at 1 meter. That would mean at 2 meters a single 8k cannot produce reference in the low frequencies. At 2 meters, that would be approximately 109 dB. With three 8ks, you'd be back to 118 dB. (I am not being critical of their design ... I happen to like those speakers.) Looking at the SW5500, they are rated at 110dB SPL at 1 meter .... ie, they will not produce the full dynamic range at 1 meter. So accounting for a 6dB loss for each doubling of the distance, it would take several to produce reference (115dB at 20Hz). Certainly for most music content, that's fine but note when we did Previn and the Atlanta Symphony's 1812, there was 10Hz content on the masters.

I should add, the fact that a single DSP8000 has four low frequency drivers does not mean the rated output of the 8k is four times the published rating for the speaker.

Finally, one does need to utilize care in the selection of subwoofers when multiple subs are being used in a single space. Subwoofers, as do all speakers, have an optimal range of operation. As much as you do not want subs operating near, or at peak, you also do not want them operating below their optimal curve.

Mr DErskine, did you install Ken's 861v6 or ADA with QSC and 4 subs?

Do you believe ADA has that much better signal to work with to get tight slamming bass vs an 861v6? That's what the thread started out as. And some of us are trying to get to the bottom of it.

Some folks want this to be a Coke vs Pepsi argument. You'd think respected Meridian owners would like to understand too. Guess not.

The all Large vs Multiple Mono Subs is certainly a good debate (should probably be in seperate thread). And I'm sure many appreciate the knowledge you are sharing on that topic. And I respect both sides. I think there are tradeoffs to each. And a LOT depends on priorities, size of the room and constraints (not to mention knowledge of knowing how to do it).

Most of us have been told/read numerous times the under 80hz has no directionality, but it just doesn't seem to be jiving with experience for many of us. What the science is behind it I'm not going to say I understand. But I can try to speculate as best I can.

I agree running mega large speakers will only get you so far as far as room size goes and then you have to use subs to start filling gaps. But, as you know, it gets extremely complex.

Again the point was why would it be possible on an ADA Mark IV and not possible on an 861v6.

In otherwords are you agreeing that the 861v6 is inferior to ADA's Mark IV in regard to getting 4 subs working using your tools of the trade?

Let's take a mono signal containing frequencies above and below 80Hz.

If I split that signal between a subwoofer and a loudspeaker and place those two apart from each other and at the same or different distances from the listening point in say a triangular configuration, surely I will notice that it is not a point source? I am sure I could use delays and phase adjustment to get them time aligned but surely I would get an odd image?

So although bass may not be localised in isolation it may be in the context of a real-world signal?

For most of us a subwoofer is a means of getting some deep bass in a domestic environment at reasonable cost and some compromise. For those of us who can afford five (!) subs, surely it makes sense to place them adjacent to the speakers they support then manage the room modes with some form of correction rather than displace them and then have to manage phase and timing anomolies as well as the room modes?

I think this is an argument for five full range speakers for optimum phase and timing performance (my Sys 1) rather than 5 small speakers and a sub for optimum room usability (my Sys 2).

Guy's tell me if I'm blind or something.

From specs on infamous QSC-322ua (not sure Ken has this exact model, it's the only QSC-322 I can find and I've been burned on that before so I'm asking). Joelc said Ken was running a QSC-322az (can't find a thing on that).

http://www.qscaudio.com/products/network/DSP/dsp_322ua.php

Frequency response
20 Hz - 20 kHz (max) +/- 0.5 dB
20 Hz - 20 kHz (typ) +/- 0.2 dB
Audio converters 24 bit, 48 kHz, in and out

As many folks know I don't think 96Khz is a big deal vs 48Khz.
But it sure is critical when doing A to D. You'd have to sample at 96Khz to retain 48Khz.

We have been talking 4 mega subs right, yet this box seems limited to 20Hz. LFE goes from 3-120Hz

I sure hope this isn't the box Ken is using.

I did put the 816/v6 in his rack. There was someone else there at the time doing calibration. I did not install the ADA. The serious calibration was done by an individual I know very well and knows his craft exceptionally well. (Not the lad there that evening.)

I have measured the QSC down to a 10Hz signal. Your misunderstanding of the specifications is understandable. The fact the published specifications are only from 20 to 20k doesn't mean those frequencies are a brick wall.

I also have no clue as to why you'd be concerned with a 3Hz signal. First, it would not be audible. Second, even if you did have a sub that could reproduce it, the amount of energy required to reproduce it would be staggering. The fact of the matter is there are way too many music records with sub 20Hz content ... all of it unintentional. Why? It couldn't be heard by the studio/mix engineers (below audibility) or below the ability of the equipment (subwoofers) to reproduce it. That's a problem! Where below 20Hz is intended, you want to reproduce it. Where it is not intended, you wanna kill it off.

I agree Mr. Derskine, on the 20Hz. I realized that on the drive home from work that it's just that range it's accurate too that spec (My error, that's why I asked). It does not mean it's an absolute low end range. Just that it won't be as accurate over that range as it is 20-20K. Which is true for any audio device. I was just stating LFE range regarding 3hz. I'm not worried about 3hz.

But the 48Khz A to D. There no misunderstanding there. Am I misreading that.

Sampling 192Khz DACs at 48Khz?

I've tried many combinations/permutations of subs with my main Genesis speakers, including crossover points from 80 hz. down to 30 hz., as well as running the mains full range and 'bass doubling' with multiple subs. I never could get things to sound right with crossover points above 40 hz., nor did placing the subs in close proximity to the mains work either. So, I ended up crossing the bass from all channels to a single mono sub (sub #1) at 30 hz. located in a somewhat 'traditional' front corner. The remaining subs were then daisy-chained to the mono sub channel and located in different places in the room based on a long period of experimenting with location, phase and output level. In my room, location ended with sub #2 on top of sub #1, sub #3 in the rear, diagonal corner, and subs #4 and 5 stacked along the left side wall. Further complicating things is that three of the subs are sealed, one is ported and one is a folded horn. I don't doubt that five may be overkill and that removal of one, or even two, would make little difference, however, since things finally sound great in the low bass, I see no reason to muck around with things.

George:

Apologies, my bad as I got the "ua" and "az" mixed up...a close look at the QSC porduct line reveals that the the differnce is in the connector types but otherwose teh capabilities are all the same...

And, with respect to the 48kHz versus 96kHz debate I will let DErskine respond but I suggest that he will respond that this is not a material issue depending on speaker type, etc. and, to avoid further confusion, I say this because:

1. DErskine designed my theatre and will calibrate it in two months time; and

2. DErskine and I had this conversation/debate when we were deciding on which DSP engine to use in my new home theatre noting that I was considering more costly units that worked at 96Khz (and above) but ended up with the QSC 922uz which operates at 48Khz...and before everyone goes nuts as to why Ken uses the 322 and Joelc uses the 922 it is becasue I, unlike Ken, am using QSC amplifiers which when paired with the 922s provide real time feedback and monitoring [i.e. the 322 and the 922 have the same capabilities re: DSP but the 922 adds/has different CobraNet and other communication capabalities]...

And, that said, DErskine, feel free to chime in...

Thanks Joel. I understand your trying to help and maybe got a few things imperfect as did I.

Like I said the 96Khz and up (which ends up including Meridian Apodizing and Upsampling and all that) is a bit overrated (IMHO) and I'm in the minority on that.
But sampling at 48Khz doesn't even get you 48Khz accuracy. It gets 24Khz accuracy (information captured) anything higher than that is lost.
See http://en.wikipedia.org/wiki/Nyquist_frequency

Perhaps it samples at 96Khz giving you 48Khz effective accuracy and that is what the spec is trying to say.
That might be a possibility. But it doesn't look that way. Or the infamous spec typo.

I do believe you can do good A to D (Like Meridian's IA45 card which is 96Khz). But geesh 48Khz is not state of the art today.

You would need to sample at 384Khz to capture what comes out of a Meridian 861v6 DAC (or ADA DAC).
You would need to sample at 192Khz to capture what comes out of 96Khz BD or DVDA.
You would need to sample at 88Khz to capture what comes out of 44Khz CD.

You are talking BELOW CD.

You're system is only as good as it's weakest link.

Running only bass through the QSC is no problem (and quite useful steering multiple subs), but using it full range as Ken does seriously compromises sound quality.