Meridian Unplugged - Powered by MrTechGuy.co.uk Forums Discussion Meridian - Systems What is the lower limit of Digital Room Correction (Hz), etc...

Hi,

I have not been following Meridian and A/V in general for the past year due to focusing on radiology, having to buy a house, and other issues. Due to a problem with a dealer who ultimately declared bankruptcy, I got ripped off for a Meridian 800 version 3.0 as well as a Faroudja NRS 720p scaler (approximately 1.5 years ago). That took the wind out of the sails along with a couple other issues.

Anyway, what was the end result of the room correction software in terms of abilities. Can somebody summarize the abilities as well as how the subwoofer(s) outputs fit into the picture? What is the lowest frequency one can adjust?

Ultimately, I'll probably have to use a linkwitz Transform on any future IB array. I hope to build a dedicated room, something on the order of 20 W x 30L x 12 H using dual walls (probably concrete outer wall/ air space/ staggered stud wall with floating gypsum board) with optimal shape, etc... Then comes the "Black Hole of Infinity" (Tm) Infinite Baffle array which will utilize 2 colums of the latest and greatest 18 inch subs, probably a custom run with a Qts that falls in the 0.5-0.55 range. I can fit (7) adjacent 18 inch subs comfortably adjacent to each other in a vertical column along one of the front wall corners, Most likely I will end up putting the second vertical column just adjacent to the first column in the same corner and using a 40 Hz crossover point. I am a fan of stereo subs, but once you get to the point of using true full range speakers and a crossover point of 40 Hz to the Infinite baffle array, I think it is most acoustically ideal to just use one corner. I'll sell my 5 Nautilus 802 speakers and get something truly full range... perhaps Grand Utopias or something on that order.

So the point is to end up with a front wall with an infinite baffle array of approximately (14) 18 inch custom drivers (directly adjacent in two vertical columns) optimized for low Fs, Qts 0.5-0.55 ... Crossover of 40 Hz... Meridian 861 to use digital room correction which I have not upgrade to at this point, however, I may need a separate EQ to tweak the IB most likely.. May as well make it flat to 10 Hz with that kind of headroom. The amplifiers and most equipment will be in the 'IB room' behind the front wall of the HT room. If a serious concrete wall is used (With intervening 3 inch thick baltic birch for mounting the subs to the front wall... Flexion is not going to be an issue) . In any case, I believe this will be the most elegant sounding method of producing effortless bass. This method would be utilized if I had 10 Million to spend on deep bass reproduction, however it would only depend on the cost of the drivers and amps... This is not the most efficient method, but this is my way to achieve quantity of the highest quality... Effortlessness and never having to exceed apprximately 1/2 Xmax on peaks is ideal... This is my idea of ultimate sound quality.

[This message has been edited by Health Nut (edited 09-10-2003).]

I'm still a 861.4 newbie and my sub goes nowhere near 10Hz, but here goes:

As can be seen in the 861 manual the frequency range of the room correction seems to be 0 to 250Hz. The main problem with very low freq. RC is the measuring device... The Radioshack SPL Meridian recommends is way off in these regions: http://www.hometheaterhifi.com/utilities-download-page.html
10 Hz -20.5
12.5 Hz -16.5
16 Hz -11.5
20 Hz -7.5
25 Hz -5

You can of course run the sine sweep and fix the problem freq. manualy (filter editor).

One other important thing... you can only make corrections in the minus range (-20 to 0dB) and the total amount of filters is limited to 60 (I need almost 50)

Do read the V4 manual if you haven't already

That is strange... why can you not add boost? I guess I'll rely totally on the boost from the linkwitz transform for the Infinite baffle array so it can be flat to 10 Hz and can make additional corrections for the positive room modes with the Meridian rom correction... It is not an issue at an issue at the moment anyway, just keeping in touch...

I understand that room dips are from cancellation and not something you can boost to correct, however, it would be nice to add boost for other digital EQ purposes...

[This message has been edited by Health Nut (edited 09-10-2003).]

but can you get bass this low?!

http://dsc.discovery.com/news/afp/20030908/soundwaves.html

Im sure you know this,but MRC runs from 20-250hz.

Hi Jerry,

I have not followed Meridian closely for around a year and a half due to being ripped off from some dealer who ended up declaring bankruptcy and took my Meridian 800 and Faroudja NRS 720p down with him amongst lots of lies, etc,.. so I lost a lot of money in that process and any ability to upgrade from what I have now. I just have my Meridian 861 2.X and still suffer the repurcussions of what happened, so I'm still unable to upgrade or do anything until at least 2 years from now... that was a huge loss. I'm still clinging to a Sony 7700 Cinematrix from MSB for the time being...probably until an HD-DVD player comes out at this point.

So room correction is 20-250 Hz and is like a parametric EQ but only allows one to reduce the gain at a specific Hz and Q? Is that the short version? Any other quick summaries or opinions?

I noticed the Black Hole bass notes on the DIY speaker list... I never did catch the frequency... I tend to get uninterested when it becomes less than a single Hz... if that's what the freq is

[This message has been edited by Health Nut (edited 09-10-2003).]

Interesting link, Jerry. I wonder what the Radioshack correction factor is on that?

All I have to say is thank-god, literally, for the 1/d^2 rule for effect of gravity...

HN,
actually- its not really a parametric EQ. As you probably know using a parametric eq or plain eq in a room will result with 1 point having the desired eq but the other points likely not achieving anything close. What Meridian is doing, and I think it is very sophicistated, is trying to equalize the time each frequency is ringing. so for example, they will get 30hz to ring the same amount of time as 40hz. Every time it makes 1 correction, it creates a "filter". I believe the system is capable of up to 8 filters/ channel. I know someone who is truly an expert in acoustics and she tells me this approach is the most desirable. the way I would characterize the affect of MRC is that it will make a subtle, but noticeable improvement in the clarity of the bass, which somehow helps the clarity of the entire sound. I would not think it would "fix" a bad room, but I think if your room is a decent acoustic space it will help.

as far as setting it up- its easy. just plug a rca cable into a radio shack SPL meter and the other end into the analog input card in the 861 (you need an analog input card). you run the MRC software (part of the new Meridian setup software). when you run the software, it gives you 25 seconds to leave the room. you put the mic about where your head would be and leave. it runs test tones and then formulates the filters for each channel. I found I get slightly better results when I hold the mic near my head and sit in the chair. the test tones arent that loud. you can turn the RC on and off in any preset.

as you can tell, Im a fan. btw- the v4 upgrade to the 861 also includes much more computing power and the result is a really more refined sound before RC. hard as it is to believe because I was very impressed with v3.

Don't despair Dr. Chris.Board certification, the big bucks, and the big bass will come soon enough.

this thread might be of interest:

http://www.softronix.com/ubb/Forum2/HTML/000128.html