Ugghh...help - Home Theater Forum and Systems - HomeTheaterShack.com

Old 03-02-08, 04:02 AM
mamm7215
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Ugghh...help

I finally got this working and did an analysis of my home studio room. I have bass traps floor-ceiling in all 4 corners and 2 5x4' panels on each long end wall and wall/ceiling traps above those and a 5x4' cloud above the mixing desk. I used another eq tool and it reported a big null at about 90hz. REW confirms this. Is it the room or my speakers or mic??? What can I do about a null like this, it's a critical bass frequency?
Tia.
M.
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Old 03-02-08, 06:53 AM
REW Author

John

Join Date: Apr 2006
Location: UK
Posts: 6,296
Re: Ugghh...help

If you have a sub in the system adjusting the sub's phase may help. If not, the dip is likely to be due to the position of you or your speakers or both, try measuring in different locations to see what effect changing the listening position has and try moving the speakers to see if there is a position that gives a smoother response.
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Old 03-02-08, 07:05 AM
Elite Shackster
brucek

Join Date: Apr 2006
Posts: 7,514
Re: Ugghh...help

Let me make a few points about REW first.

It would be wise to use a vertical scale of 45dB-105dB for your graphs. This allows an reasonable swing of +/-30dB (total 60dB) around a 75dB target. Your graph uses a total of ~190dB. This makes the presentation quite kind to your results.
Use a vertical axis of 45dB-105dB.

The horizontal scale shows an extension at the low end to 2Hz. You can see the response of your speakers extending into the noise at about 20Hz. Use this as you bottom figure of your horizontal axis. You've measured to 200Hz, so make that your top figure.
Use horizontal axis of 20Hz-200Hz.

When using waterfal it's most reveiling to use the same axis as the response graphs and also to use a LOG view rather than the LINear view. This way you can use the slider to dial down to a single slice that matches the response graph and then slowly move to 30 and watch the signal degrade out.

Quote:
Is it the room or my speakers or mic???
Not enough information. You need to tell us what type of mic you're using and whether you are using the correct calibration file.
Is this a single monitor at the listening position at the console?
If you know your mic is correct, then you can do a near-field measure of a monitor outside or at least in the middle of a room where there are no boundaries. This will (attempt) to reveal the response of the speaker itself without the room influence.
Then when you know it's not your speakers, take measures at different spots in the room. You may have to move the console a bit to reduce the dip..

brucek
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Old 03-02-08, 10:55 AM
mamm7215
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Re: Ugghh...help

Ok, I've done a bunch more tests, it seems that the null follows mic placement, ie if I move the mic back from the listening position in 6" increments, then the null follows at higer positions. Ex: Listening pos, -6in, -12in, -18in the null goes from 92hz, 104hz, 108hz, 112hz
Old 03-02-08, 11:04 AM
mamm7215
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Re: Ugghh...help

Interesting...after a bunch of measurements, I've found that between the current listening position and 2 other positions, the last being standing up 3 feet back of listening, I can get a composite accurate graph if overlayed with each other. Would it be ok to use 3-4 listening positions to get a better idea of overall response? There's not a lot of room for any more treatment in here but I can live with the comporomise.
Old 03-02-08, 11:36 AM
Elite Shackster
brucek

Join Date: Apr 2006
Posts: 7,514
Re: Ugghh...help

Actually, we just had a member here a week or so ago that had a small studio and some of the same positional problems you're experiencing. I think you would find it interesting to read this thread completely through. Positioning ended up being the best fix. I know it's a bit more difficult when it's a studio, but sometimes it's needed.

I think unlike a home theater where there are concerns for listening positions of other individuals, wouldn't a studio attempt to have a single sweet spot for mixing?

brucek
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Old 03-02-08, 03:44 PM
mamm7215
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Re: Ugghh...help

Absolutely, but it's not a big room so moving around a bit won't kill me
I'll read that thread. The other problem is I'm using Yorkville YSM1P's with no sub. They're good for mid and high freq but the lows are weak on them, even though they're rated down to 45hz.
Old 03-02-08, 04:03 PM
mamm7215
Inactive

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Re: Ugghh...help

BTW, how do I set the graph to read 20-200hz? I can't get it exact using the magnifying glass in the corner?
Old 03-02-08, 04:10 PM
mamm7215
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Re: Ugghh...help

Another update...I just redid the test using another pre-amp. This with the same mic (Apex 460 modded with peluso capsule, cinemag xfrmr and changed out output cap). A bit different response so there is obviously some user error here as well?? or original pre's characteristics (ART MPA GOLD) came out in the plot...
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Old 03-02-08, 04:19 PM
mamm7215
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Re: Ugghh...help

Nevermind, figured the graph out...

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