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I just mapped my room response with a Radio Shack SPL meter and the Rives Audio Test CD2 calibrated tracks. My results are below - quite concerning I am pretty sure. My attached room picture show the listening view but the back of my room is totally open into the rest of the house - will try and include a second picture, not sure how yet. Please advise - what would be the best next step?
Freq. SPL
20 80
25 86
31.5 89
40 89
50 88
63 80
80 87
100 90
125 87
160 88
200 89
250 89
315 82
400 82
500 78
630 89
800 80
1000 81
1250 77
1600 76
2000 78
2500 92
3150 92
4000 92
5000 91
6300 94
8000 78
10000 68
12500 64
16000 64
20000 54
Follow Ups:
Hi Eric, I'm no professional and the other posts are certainly knowledgeable, but my experience is to use a 30 band graphic equalizer you can get one used for about $100. This allows you to tailor the bass, which means smoothing out the sound, you can't add to the nulls, but you can detract from the peaks. Yes, using bass traps, etc., are preferable, but with the 30 band you can adjust to your liking. Equalizers are controversial, but then when you use cables as tone controls, just try it and see if it works for you and your room. If you buy used (ebay) and don't like what you hear, you can recoup most of your money and be wiser for the experience. I have the Rives and RS meter as well, and a bass tone cd that does it in 1db increments to 100db. My experience is the bass is foremost, followed by annoying highs which can be the recording as well. The hard part is to get it balanced so that not only do your test music cd's sound great, but the rest of your cd's/records sound better. If I had my dream eq it would have presets for about 5 different settings since recordings differ so much. I have also tried the digital Beringer 30 band, but went back to the analog type because I didn't like the digital sound, and the extreme highs were lost. Good luck!
You might find this post helpful:
http://www.AudioAsylum.com/audio/tweaks/messages/17541.html
Jon Risch
Did you use the C Weighted, Slow mode? Also, the RS meter needs correction data as it's not accurate at the extremes.
As others mentioned, the numbers aren't that bad +/- 3db mostly in the 300-2Khz range. The bass probably needs traps and it would look like there a room mode around 25-30hz. The only thing that sticks out to me is the peak from 2500 to 6300. Perhaps that's due to the speaker toe in and meter positioning.
-Rod
He's using the Rives test CD. It supposedly has the levels of the test tones corrected to match the RS meter response so the meter readings don't have to be adjusted.
David Aiken
> My results are below - quite concerning I am pretty sure. <
Actually, the data you posted is mostly useless. Low frequencies need to be measured at much higher resolution than 1/3 octave. More here:
Test Tone CD
Sine wave tones at high frequencies are equally useless because if you move the measuring microphone even one inch you'll get a totally different reading. So I prefer 1 Hz spacing below 200 or 300 Hz, and 1/3 octave filtered pink noise above 300 or 400 Hz.
> what would be the best next step? <
Here's my standard advice which will get you 99 percent of the way there. All rooms need:
* Broadband (not tuned) bass traps straddling as many corners as you can manage, including the wall-ceiling corners. More bass traps on the rear wall behind helps even further. You simply cannot have too much bass trapping. Real bass trapping, that is - thin foam and thin fiberglass don't work to a low enough frequency.
* Mid/high frequency absorption at the first reflection points on the side walls and ceiling.
* Some additional amount of mid/high absorption and/or diffusion on any large areas of bare parallel surfaces, such as opposing walls or the ceiling if the floor is reflective. Diffusion on the rear wall behind you is also useful in larger rooms.
--Ethan
Levels are usually compared to the levels at 1000 Hz.You've got a few peaks and little in the way of dips below 1000 Hz and the biggest peak is +9 dB. That's not bad at all for an untreated room. One of the peaks is a little high in frequency at 630 Hz, you would expect things to start smoothing out a bit before that, but I don't think it's unusual.
Above 1000 Hz you've got a small dip followed by a rise and plateau from 2.5 kHz to 6.3 kHz followed by a rolloff. I'd say the rolloff is partly due to the absorption of high frequencies by air, partly by absorption of high frequencies by soft furnishings, and partly losses due to reflective behaviour at the back of the room.
Acoustically, the situation at the back of the room is complex with the hallway and kitchen split by a wall and both opening into areas even further behind. Those coupled spaces do have an effect on what you measure at your listening position and I suspect they're responsible for a lot of what you're seeing in the measurements.
Ignoring the rolloff above 10 kHz the room is measuring +11/-13 dB from 20 Hz to 10 kHz. That's well within the normal range of variation for most rooms. Though where the peaks and dips occur is a little interesting, it's certainly not unheard of. The rolloff above 10 kHz would be expected. You won't find a room of the size of most listening rooms that measures flat and you won't find a room which opens into other spaces which doesn't have some "interesting wrinkles" in its measurements.
Forget the numbers to some degree. What counts is how it sounds. Enclosed spaces don't give uniform measurements and we're adapted to that to some degree. What you're measuring is a combination of direct sound and reflected sound and the ear/brain doesn't work that way. It can separate the direct sound from the reflections and that influences the way our brain processes the sound. With more sophisticated measuruing equipment you could get measurements showing the behaviour of sound in the room over a time window of several hundred milliseconds and that would correlate much better with how you hear things in many ways but a simple meter like the RS meter can't do that so there's no point getting overly worried about the results you've got. What counts is how it sounds and I'd bet that it doesn't sound anywhere near as bad as you think the measurements look.
What makes you think anyone else's untreated room measures much better than yours?
David Aiken
Edits: 01/09/09
I don't see what's "concerning". That's not a terribly varied plotline you have there overall. Yes, you have some peaks and some troughs, but jeez, this is not so bad. Maybe I'm way off?
Until you get to almost 10kHz, what's the big problem that you see?
And, BTW, was this C weighted reading?
I'm wondering why you're getting such low readings when you go from 8kHz up the scale. Sounds like either a tweeter isn't putting out well or your room is soaking up the HF quite a bit.
I'm given to understand that room EQ isn't really for boosting troughs as it is for taming peaks. If that bit of CW is correct, you might benefit from a supertweeter, but one that's set down into the audible range (as most except the really expensive ones seem to be), or maybe a new tweeter. Room EQ probably can't be used effectively to boost the HF downslope you have there, so another source of HF might be in order.
But since I'm still new to this myself, don't take what I'm saying here at all to heart until you ask those more experienced. In fact, you might be better off posting this Q in the Speaker Asylum.
here is a picture showing the back of the room
I saw your room reponse check, thought you might want a more accurate
measurement. I have software that will help. You would have to redo the readings starting with adjusting db for one of the spkrs for reference @200hz,70db. Set the mic where the 2 spkrs cross (sweet spot). Measure/write all db, 20 - 10khz at this distance. Then measure db, 20-200 Hz near field (within 1/4" of center Woofer dust cover; will be ~30db higher) Aim the meter on a stand (diy.. 5/8" wood dowel rod screwed into plywd base, find 5/16" pan hd for mic screw; which is put thru std plastic 1/2 plumbing snub end, slide on a match male/female elbow fitting; this will slide onto dowel top.. no glue. Measure/cut dowel length for the center of Tw cone ht., cut another dowel for the center driver of your 3 woofer arrangement.) Send me the readings and I will send you a plot with a comparison to top of the line speaker using the same method. I am retired with time on my hands.
I suggest you download the free REW (Room EQ. wizard) software from www.hometheatershack.com.
You can use your RS meter's mic and output port to feed the measured signal to your computer to properly see your room's response via REW that includes the mandatory time domain. Simple RS measurements don't.
There's lots of posts on the REW discussion area and also about calibration corrections and using a RS meter.
It's all about the music
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