Use Har-Bal to tune your playback equalization

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Re: Use Har-Bal to tune your playback equalization

Postby Gordon Gidluck » Fri Nov 28, 2008 9:16 pm

I do have an RME Multiface, and it comes with DigiCheck which has an excellent RTA. I could use that.

Half of the back wall of this room is open, so my thinking was that the open space would provide an outlet.

As well, mastering rooms that I have seen use an elongated room with the speakers a good distance away from the back wall. Perhaps this assumes that the room echo has been treated acoustically by a professional acoustician.

I saw one estimate of 38% being the best distance to be from the back wall. I forget now where I read that. Of course, I am still learning, so please excuse me if this is incorrect.

There is a thread going on prosoundweb.com (in particular Brad Blackwood's forum) regarding the new room that is being built for amsterdammastering.com . You might find the layout of the floor plan interesting as well as the acoustic planning.
http://recforums.prosoundweb.com/index. ... 611/12697/

Thanks for the link. Ideally, I suppose that room dimensions should be based upon prime numbers. If I ever get a chance to build my own room for audio, I will do it right. But for now, the plugin will help.
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Re: Use Har-Bal to tune your playback equalization

Postby HarBal » Fri Nov 28, 2008 11:44 pm

The speakers should be a good distance away from the wall to both reduce coupling and keep the bass output from being overly raised by virtue of being radiated into a "quarter space" against the wall, or worse still, an "eight space" in the corners. 38% sounds like a rule of thumb to me. Where exactly is the best spot is determined by room geometry as the modal patterns are governed by that. Whilst you can do a lot of elaborate design beforehand, ultimately fine tuning can only be done the manual way of measurement trial and error. Models of acoustic behaviour are only as accurate as the level of detail you put into them and part of problem of being able to predict the behaviour is knowing the material properties well enough. That is usually why model and reality can differ considerably.

Why most mastering studios are elongated is predominantly because you want minimal reflection directed back to you off the back wall as it plays havoc with imaging. So typically the back wall is a fair way away and covered in diffusers. That being said, it doesn't have to be that way if you can ensure sufficient diffusion and or a reflection free zone. My space is very small in acoustic terms (2.7m wall length pentagonal room with 3m ceiling height). At a guess, it would be less than 10 square metres, as opposed to the luxurious 42 square metres space in that design (which, by the way looks eminently sensible). Given the very small nature of my room I find it quite remarkable that it is as good as it is. The impulse response post treatment is almost ideal. The only thing I can't get away from is the problem of controlling that LF mode and that is where a big room helps. But it is a double edged sword in that the larger the room is the more treatment you will require to control the acoustics (simply because the room surface area is so much bigger). As mine is so small I was able to get away with not much treatment area as my wall area is correspondingly small.

On the open end aspect of your room, I don't know if it is ideal. My room has double doors on the back wall that I can open up and I can say with absolute certainty, that it sounds considerably better with the doors shut rather than open. On the other hand, they both have diffusers attached to them to avoid any early reflection issues. Prior to the diffusers the reflection was a audible and unpleasant problem. With the doors open the performance looses vitality as the level of diffuse sound in the room is considerably reduced.

A good room is one that provides the right level of diffuse ambiance. Many rooms have the right level of ambiance but in the form of plane specular reflections which confuses the image leading to listening fatigue. Sort of like walking into a room of mirrors. you'll see many images of yourself but which one is you. Sandblast the mirrors (adding diffusion) and the ambiguity goes away.

cheers,


Paavo.
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Re: Use Har-Bal to tune your playback equalization

Postby Gordon Gidluck » Mon Dec 01, 2008 12:35 am

HarBal wrote:The hardware version of Audyssey allows you to interface with a PC and get graphical views of the measure room impulse and frequency responses before and after correction. I don't know if the ARC product gives you that option.


The ARC plug shows you the uncorrected and corrected frequency response, but it is a very small graph. There is no option to see impulse response data.

That hardware box would be nice to have. That way you could eq anything going to your amp/speakers. Right now I can use ARC with any VST capable program. Someone wrote a VST wrapper for Foobar2000. I can play CD's with correction on using that. But there is no option for the plugin with iTunes on windows. iTunes is nice for previewing music.

Gordon
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