Room Acoustics

[romavictor]

Hi guys

Anyone know how do I rectify what looks like a 50hz dip? Thanks

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[romavictor]

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[thxthx]

Great story Brent! I'm sure my room is getting in the way of my equipment sounding all it can. Unfortunately it is the only room I have so I'm hoping to meet someone with some expertise in the area of acoustics whom I have confidence in! Enjoy...

[chessman]

romavictor,

I have two possibilities for you to try.

First, the 50H dip may be caused by the 31H hump. If you are using any kind of subwoofer EQ (active cross-over or onboard EQ on a sub) try cutting the 31 H signal. I cured a similar problem in my room by adjusting the E.L.F. on my JL Audio F113 to minus 12. That happened to be right at 25 H, where my problem happened to be. If you do not have the EQ, try moving the sub in small increments. A one inch rotation can sometimes work wonders.

Unfortunately, your 2D waterfall graph does not show a sustained decay at either 31H or 50H, which suggests to me that the problem may not be cured using my first solution. It may be a case of "speaker boundary effect." Is one of your speakers close to a wall? If so, my second solution is to try moving it in small increments (either rotate or away from the wall). Wall reflections cause phase problems. In extreme cases you get a "W" pattern on the graph. In less extreme cases you get the "hump then dip" picture. Solution 2a would be to put a big bass trap behind the offending speaker, but in real world situations space or aesthetics may negate that choice.

Finally, and this is just curiosity, do you hear this problem or does it bug you because the XTZ Room Analyzer lets you see it? With audio, always trust your ears over your eyes. Graphs carry undue weight for us because we perceive them visually and we give undue weight to what we see. My XTZ ran me in circles for a while, until I realized I could not hear the "problem."

[chessman]

Bikeman, I just realized I semi-hijacked your thread about your room. My apologies.

[Bikeman71]

Originally Posted by chessman

Bikeman, I just realized I semi-hijacked your thread about your room. My apologies.

No apology needed. My story was meant to spur further conversation...this is not just about my room, it is about our rooms!

[Bikeman71]

Also...with the most critical part of any audio system, the room, back in balance, I have started buying stuff again. My addiction is back! Not sure this was a good move after all...crap! Ha!

[romavictor]

Originally Posted by chessman

romavictor, I have two possibilities for you to try. First, the 50H dip may be caused by the 31H hump. If you are using any kind of subwoofer EQ (active cross-over or onboard EQ on a sub) try cutting the 31 H signal. I cured a similar problem in my room by adjusting the E.L.F. on my JL Audio F113 to minus 12. That happened to be right at 25 H, where my problem happened to be. If you do not have the EQ, try moving the sub in small increments. A one inch rotation can sometimes work wonders. Unfortunately, your 2D waterfall graph does not show a sustained decay at either 31H or 50H, which suggests to me that the problem may not be cured using my first solution. It may be a case of "speaker boundary effect." Is one of your speakers close to a wall? If so, my second solution is to try moving it in small increments (either rotate or away from the wall). Wall reflections cause phase problems. In extreme cases you get a "W" pattern on the graph. In less extreme cases you get the "hump then dip" picture. Solution 2a would be to put a big bass trap behind the offending speaker, but in real world situations space or aesthetics may negate that choice. Finally, and this is just curiosity, do you hear this problem or does it bug you because the XTZ Room Analyzer lets you see it? With audio, always trust your ears over your eyes. Graphs carry undue weight for us because we perceive them visually and we give undue weight to what we see. My XTZ ran me in circles for a while, until I realized I could not hear the "problem."

Hi Chessman

You're right!! I only noticed the problem thanks to XTZ, otherwise it has a much better bass response compared to where the SW was previously located, which was jammed into a corner. I moved it to the other side which is open to a hallway.

I have a B&W sub ASW855 that does have not much to toggle with setting wise accept for phase (0 or 180), volume and low pass frequency adjustment. I have it set at 60hz while the mains handles beyond that.

I might be able to rotate the sub to the left or right but location wise it's about 3 feet from the wall sitting next to the left main. See attached pics.

It would be nice to have a flatter curve but moving stuff around is not a choice I have since I've already moved things as much as I can without taking over the living room. I was thinking of bass traps but definitely not those big ugly things that you usually see. Do they have ones with a slimmer smaller profile that's perhaps wife friendly? And hey worst case scenario, will an EQ component help smooth things out? Which one would recommend....My source is an Oppo 105D running into the C2500 preamp which drives the MC452 amp.

Thanks for your help Chessman.




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[romavictor]

Originally Posted by Bikeman71

No apology needed. My story was meant to spur further conversation...this is not just about my room, it is about our rooms!

Thanks. Didn't mean to take over either...😀

[chessman]

romavictor,

When you are dealing with frequencies below 200H it is far more important to have roughly equal decay times than a flat frequency response curve. Your waterfall graph already looks good. That plus not hearing the "problem" tells me you should declare victory and be happy with it as is.

Seriously, flat frequency curves are touted to sell EQ equipment and that misses the point. I spent a ton of money and wasted a lot of time to achieve a table top flat frequency response curve (as long as you held your head exactly where the measuring mic was - duh) and it sounded like crap. I used the XTZ to help me measure decay times, limited the EQ to one cut at 25H (room induced), lived with a less than flat frequency response curve, used some ugly bass traps in my dedicated room and it sounds great.