Meridian Unplugged - Powered by MrTechGuy.co.uk Forums Discussion Meridian - Systems MRC - Too many filters?

Hi Shankar,

With MRC switched off, how would you describe the sound of your room Pre / Post room treatment?

Regards,
Carl

Can you tell us what aspect of the room's sound changed, and in what (if any) ways it is better and in what ways it is worse?

That, along with the drawings of the room may prove helpful.

Thank you

oops , I read 25 feet square the wrong way.
Square room = bigger bass problems

25 feet square, i.e. 25 feet by 25 feet = about 650 sq feet.

Shankar

With MRC switched off the sound is not so very different pre and post treatment. It is boomy with strong room modes at 25 and 50Hz that are clearly visible in the plots. I have not really gone for bass traps etc. so this is logical. All the treatment relates to making reflective surfaces a little softer or uneven.

However, post treatment, if I leave MRC on auto (371ms) or tighten the decay further, the bass becomes very thin and the overall sound level drops considerably possibly because the energy is being sucked out by deep filters. I end up listening on an average 10 points higher for the same perceived level. Also, the sound starts becoming very forward and almost shrill.

I have to bring the decay to 450ms and manually attenuate some of the filters (from -12dB to say -7dB) to make the sound reasonable.

Photos now uploaded Shankar - Media Room Layout

Thanks all,
Shankar

How high is the ceiling and is it flat? Any treatment on the ceiling?

Ken

Ceiling = 10 feet. Absorbent wedge foam on ceiling - see images referred in Gallery.

Shankar

The textbook says try to adjust the listening position and speakers to minimize modes. That's not easy to do, especially in a multi-purpose room. At a recent roadshow, I asked about bass problems and the suggestion from several M. execs was to move the speakers closer to the wall. In close, it couples to standing bass waves and produces a stronger base effect. I've tried it in my room and found that it works for me. The somewhat tech description: the speakers have rounded backs and can get up close to a back wall, but the mid range and tweeters are still out in open space. You can also adjust the boundary setting if some bass is a bit bloated. Worth a try?

Moving the speakers closer to the wall is actually a very good thought. In fact prior to the room treatment the speakers were 12" from the wall; now I moved it out to 36". Let me give it a shot.

Shankar

Shankar, can you make a list/drawing where your room treatment are placed and which kind - maybe with data - are that?

Looking at the huge ceiling with so much foam on it, I imagine that this is suck out all higher frequencies live out.
To less reflection like as you have done with covering the whole ceiling, driving the sounds in a direction to dry out, unnatural, uncomfortable.
Watch the sound in a anechoic chamber, and then you get the idea.

Moving the speaker closer to the wall increase the bass, but to get a good sound you have to go away from the wall. Only builtin speakers can avoide the disadvantage with generating comb-filters. Moving the speakers away from the wall gives a better overall distribution - more equal not so many single spikes - of the comb-filters.

Your black fences in front of the windows - which material is that? If it is a thick/heavy rubber/plastic fence, then it act like a panel absorber for deep frequencies (less bass).
Also windows acts like panel absorber.

Your big sofa absorb also the bass.

Are the black surfaces - clearly visible on the left and front wall on the upper edges close to the ceiling - room treatments,
maybe bass absorber?
The same question on the lower edge on left and front wall?
That's all bass absorber-hopefully not.

What is the big black surface below the screen, maybe also a panel?

Which material are the walls-concrete, brick, wood?
Same question for the ceiling and the floor.

I send you a PM with my emailadress, so you can send me the MRC files before and after room treatment.
How they are measured,with the fences in front of the windows,doors/windows closed.

Robert

Do you have a way to take any room measurements? The ceiling and walls look very damped but the floor not so much. REW, XTZ or the like could help us a lot.

Ken

Shankar, room looks fine apart from the very ugly foam, which IMO is overdone.

There is an easy test to see if the room is over damped, walk into it while talking and if your voices still sounds natural to you, it's probably ok, if it seems to suck the life and become nasal, it's overdone.

However, you are complaining of boomyness without correction and reediness and shrillness with. That indicates there is very little wrong with mids and HF and it's the bass correction that is killing the sound.

It could be that the boom is masking an innate issue with upper mids and treble. You might have well overdamped the room in the HF as looking at the pics, especially the foam. All most of the treatments will do and absorb is upper HF. This will tend to accentuate freqs from 2k-8k - where shrillness resides...

The problem you could have moving the speakers nearer the wall is that it might improve bass but it might do you no favours when it comes to soundstage, mid/HF and imaging.

I think you manually need to build the filters in MRC, or as I said, whack in a "house curve" to compensate for the correction leaving you bass light, or to use a different form of correction.

I have never found in any of the systems that I have used, that auto correction works 100% without quite a bit of tweaking.

Of course, vital in ANY form of RC that relies on measurements, is the measurement itself.