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My room's frequency response graph
#125320 01/24/06 08:14 PM
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Thought some of you might be interested in seeing my room's FR graph. This was a project I did with my boys. It was pretty darn enlightening, though I'm also confused by a couple of things.

The Radio Shack SPL meter was on a tripod right at my usual listening position. The speakers are Axiom m22ti, mounted horizontally (tweeters in) about 7' high, toed in and pointing down slightly towards the listening area. They are approx 12 feet apart (need to check that again), and are about 16-17 feet from the primary listening spot.

The graph (all measurements were adjusted for the known RS deficiencies and are not raw measurements):




Couple of my takeaways:
1) My room (really my listening position!) is HOSED! Makes me think of Mark Johnson, whose room sucks. Well, my room seems to be sucking right at 250 Hz, a fairly important frequency. [Note: when I moved the meter several feet to the left or right, that frequency was greatly improved, so it is something specifically in my alleged sweet spot]

2) I'm running my sub a little hot, and I didn't think I was, so I need to make some adjustments

3) My sub (SVS 20-39pci) performs a better than I thought it did. I confess to some recent sub envy with everything I've been reading, but it appears to be performing pretty well. It sounds good on music & HT, but I still feel like I'm missing some slam and pressurization at the bottom end. The room is pretty darn large, and open in a way I can't close off. I probably need a multi-sub set-up if I want to achieve a stronger chest-thumping effect.

4) Man, stuff sure does rattle in my living room! 22.5 Hz was exciting one whole wall in particular. The inserts in the fireplace were buzzing/vibrating like crazy in the upper 30s.

Any other thoughts or observations? Suggestions, particularly with respect to the suckout @ 250Hz at my listening position?

Thanks,
Rich

Re: My room's frequency response graph
#125321 01/24/06 08:24 PM
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Let me start with the obvious...your room acoustics suck but you are halfway to better sound now that you have taken the time to understand where the nodes are. First thing to do is spend a couple of weeks reading up on acoustical treatments. Once you have developed your understanding I would suggest you concentrate on basstraps in the corners which will have the most impact on smoothing your peaks and nulls. Next experiment with panels athe prime and secondary reflection points from your main speakers. Finally consider a good equalizer. The road to improved room acoustics is a long one but the most significant thing you can do to get better sound...moreso than buying new equipment.


John
Re: My room's frequency response graph
#125322 01/24/06 10:07 PM
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Well, I am trying to find out what are those deficiencies on the RS meter...

I have the digital SPL from Ratshack, and I didnt know that I had to correct for the measurements made with it..

Please enlighten me about that matter...
Thanks

Re: My room's frequency response graph
#125323 01/24/06 10:50 PM
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There is a "sticky" post over at AVSForum that contains several links for Radio Shack SPL Correction Tables. Most of the links also explain anything else you need to know about that.

Most of the links also focus on the range <200Hz for sub measurements. There is one (I forget which) which shows the corrections all the way up to 20Khz.

Hope that helps! Take care,
Rich

Re: My room's frequency response graph
#125324 01/25/06 03:15 AM
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If I remember correctly, a 250 Hz dip means you have two different paths from speaker to seating position which differ by a couple of feet. Could be something as simple as having the speakers a foot or so from a side or back wall, but more likely the difference between "direct from speaker to ear" and "from speaker to ear including a bounce off the side wall or" is a couple of feet.

If the former, move the speakers further away from the wall and the dip will move. If the latter, treat the first reflection points as others have suggested.


M60ti, VP180, QS8, M2ti, EP500, PC-Plus 20-39
M5HP, M40ti, Sierra-1
LFR1100 active, ADA1500-4 and -8
Re: My room's frequency response graph
#125325 01/25/06 12:47 PM
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My major problem right now with my room has to do with WAF.

The stockings are STILL hung by the chimney with care in hopes that St Nickolas....will continue to block the reflections off of the fireplace.

Yeah....she wants me to take the Christmas stockings down

Re: My room's frequency response graph
#125326 01/25/06 01:45 PM
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This is why I use the Rives Audio Test CD 2. It has 20hz-20K hz tracks that are calibrated to compensate for the inaccuracies of the Radio Shack meter.


I live the life I love and I love the life I live.
Re: My room's frequency response graph
#125327 01/25/06 01:59 PM
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Rich:
You need really big stockings filled with fiberglass....

I oughta know something about stockings!






::::::: No disrespect to Axiom, but my favorite woofer is my yellow lab :::::::
Re: My room's frequency response graph
#125328 01/25/06 03:04 PM
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Mark,

Santa is right!!

We made up for not having fiberglass filled large stockings by adding lots of smaller ones!! All those grandkids!!

It was amazing what a difference it made!

The Wife IS looking at producing some kind of decorative drape we can hang from the mantle to help control the reflections, so I may not get good sound "only" at Christmastime!!

Yipee!!

Rich.

Re: My room's frequency response graph
#125329 01/25/06 04:09 PM
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bridgman--

*That's* the kind of info I'm talking about! I love this place!

On one side, there is a wall that angles back before turning into the side wall, and on the other side there is just a side wall. So the side walls are not equidistant from the speakers. Unfortunately, with the wall mounting I have, I don't have flexibility to move the speakers. Even if I did, I'm not sure I could fix the problem by moving speakers because of the room's configuration. I think this may call for room treatments.

Do you have any references for where I can read more about why that particular frequency manifests this issue?

Or I could just sacrifice the alleged "sweet spot" to my wife and/or kids in an act of immense generosity, and move on over to where the suckout ain't!

Thanks!
Rich

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