Meridian Unplugged - Powered by MrTechGuy.co.uk Forums Discussion Meridian - Systems Bass management and phase

Does anyone know if the bass that is redirected from channels set as small to a mono sub are delayed to the same time that the small channel is set too? I guess someone would need to look at the bass output with a scope to verify this. The reason I ask is I have noticed changes in bass response when I change distances. I'm thinking that we may be cancelling some bass when summing all the channels set to small with a mono sub. When we adjust the distances we shift the phase of the bass of each channel thus we get different bass responses due to phase cancelation. I recently set my front three channels and sub 1 foot closer in my type setup and the bass tightened up significantly. My original setting was tighter when I used negative phase in all channels and now with my fronts and sub set 1 foot closer I don't hear any change in bass when I change phase. So I assume there is some cancelation depending on the distance settings. I just found it odd but maybe thats the way it should be anyway.

Ron

Wasn't this question asked at the factory visit (with respect to the 7.5ms delay in the latest DSP firmware)? I forget the detail of the response, but the implication was that everything (whether analogue or DSP) should now be in synch.

I would sincerely hope that the delays on directed bass were determined soley by the sub distance. In set-ups with different L and R main distances, you would certainly have phase problems if this were not the case.

In my experience moving the sub has a pretty profound effect on bass quality due to room effects etc so it's always going to be difficult to make precise measurements of the bass output.

Cliff

From a processing point of view, one would expect that the crossover filtering is performed prior to individual speaker delay. i.e. Work out which sound should be coming out of each speaker first and then apply per-speaker processing. I hope so anyway!

When setting up my subs recently, I used TrueRTA to show me what was happening... I put the subs out of phase with the main speakers and then watched the crossover area, while changing the subs distances, and looking for the greatest cancellation of sound due to the out of phase subs. It turns out that the subs correct distance setting was indeed their actual distance, which does seem to suggest that Meridian are now doing the distance/sub thing correctly...

Mark

Apparently you measure to the centre of the sub. I always measured to the grill so next time I calibrate I will try this.

Thanks for the tip, Ian.

Mark

Is the same true for all speakers? From the center of the cabinet for left/center/right and surrounds as well? My main speakers are like subs themselves and the cabinet is 1.5 foot deep.

Ron

I don't know. My question was specific about subs. Not ideal, but basically my sub fires backward and I wanted to know if I had to take into account the distance the sound is reflected off the wall. I was told to simply measure from the centre of the sub.

I think I will try it tonight and see what it sounds like. I like Mark's idea using TrueRTA. I've used the internal sine tone with an SPL meter to do the same.

This may sound crazy, but in the Meridian software I set my sub closer to my listening position then it actually is and I noticed the bass is a little tighter and more on tune with my music. My sub is actually approximately 10ft away from my couch and in a corner (diagonally behind my front Left speaker), but I set it as only 7ft away and placed between the Left Front and Center Speakers.

I was playing around with sub positioning and I found that the sub between the left and center speaker really didn't sound that great to me, so I moved it back to it's original position (10ft away and diagonally behind the left) and forgot to change the sub placement in the Meridian software.

I really don't know why it sounds better to me, other than since my 5200s are fast, telling the G68 that my sub is closer may get the signal to the sub quicker...or something like that.

Any thoughts or am I just going crazy???

Nick

Nick,

I also find setting my sub to the same distance as my front three channels is the best. I experimented a lot tonight and I always end up back with my original setup. I've tried moving my subs all over the room, changing distance in the config to the sub distance from my listening position and it never sounds that great. I get the tightest smoothest bass integration between my main channels and my sub by setting the sub distance to the same as the front three and then put the sub where it sounds the best. I also have a second mono sub set about half the distance from my seat as the front sub in the back of the room and run that one 180 degree out of phase with the front sub. Talk about nice tight articulate bass. The bass sounds great even sticking my head right in the corner of the room. Two subs one out of phase in the room and positioned just right and you can smooth out your bass quite nicely. Even in the corners! Imaging is greatly improved as well. I've tried using the sub distance setting now in two different rooms and it never works for me. My crossover is set to 80hz.

Ron