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

I�m 100% sure an 861 is as tight and has as much slam as any preamp. It's what you do with the signals after it that defines what you hear. So I�m speculating what on earth went wrong. This is my hunch.

First 861 can only properly handle 1 sub with 7 channels (he runs 7 channels).

So MRC cannot not tune each sub and more importantly, you can't set the distance to each sub.

Now you can cheat and make sure all the subs (all 4) are the same distance from sweet the spot (did he or installer do that, I don�t know). Still weird stuff can happen with the same signal driving to 4 different places in a room (no matter what you do).

MRC will still run poorly even with that cheat. If any single sub has too much decay at a particular frequency, MRC will attenuate that peak for ALL the subs (since they are jammed on one signal). And if the distances don't match it will be confused. You won't get the benefit of multiple subs filling in problem frequencies because to MRC they are all "OR'd" together.

So to "solve" the problem he adds a QSC-322ua.

There is a major feature this box describes. That it has 2.354 ms of latency on ALL channels. This is fast and insignificant for lip sync issues. But it's not insignificant as far as relative timing (phase). If he ran all channels through QSC then this is not a problem. But he ran only his subs through it. That puts them 2.5 ft out of phase. That's not huge but fairly significant. The way to fix this is to subtract 2.5 ft on the Meridian sub channel to keep them in phase with the speakers.

Now the QSC box (I believe) can account for the subs being different distances, by adding delays to closer ones. Making all the subs appear the same distance to the Meridian. But you still have subtract the right distance in the Meridian to keep it in phase with the rest of the system. Again, did he do that, I don�t know.

And as EvdBerg said you�re not applying any room correction above 80hz. Lots of low freq issues can occur above 80hz.

The best way to handle multiple subs (IMHO) is to run a bunch of channels as LARGE. And only run an LFE only sub.

In DSP land you can seamlessly add a sub to any channel. And the beauty is the latency (phase) is NOT changed at all and MRC will continue to work 100%. Because both speaker and sub get the same signal at the same time and each apply their respective filter (same latency). I love DSP speakers. You can even add multiple subs per channel (I never would though). Again you must keep sub right at speaker to keep distances right. Basically that�s what the big DSP speakers are, a sub and a small speaker in phase at the same distance. You also get better imaging doing it this way.

You can do the same in analog. But to keep latency/phase issues right (and not lose quality of Meridian DACs) I would use an analog crossover for each speaker/sub.

Another option is to find a preamp that truly handles 4 subs. Maybe ADA does, then there would be no need for a QSC.

Now did he or his installer account for all this, I have no idea. But based on his questions on the forum (and lack of questions) and speed of which he had 861v4, added QSC, upgraded 861v6, Upgraded ADA I believe something like this was going on.

I suspect once he added a 3rd and 4th sub he was in trouble.

And I still believe it's much better to process Fixed Signals (even if just subs) than Variable ones.

Again maybe he did everything right, but I want folks to realize how complex stuff gets and how you can get yourself in trouble.