[audiocrazy]

I took the measurements of my Salk SongTowers using RoomEQ wizard. I have SVS sub and the xover is set to 80hz. I have SVS AS-EQ1 to equalize the sub & Integra DTC-9.8 with Audyssey.

I'm concerned about the FR from 1k-20Khz as its a down hill. I was expecting a very small variance about +/-3db but its more than 8db difference from rest of the range.
I also turned off all EQ but still the graph is same for 1k-20khz

I've GIK Panels(room kit 2) in my room 16x12. I've a 3 pairs of GIK 242 on the side walls to catch the reflection and 244 bass trap on all the corners and monster bass trap on the rear wall.
Here are the links to the room
Front
http://www.flickr.com/photos/arshadmalik/sets/72157616172223502/
Side walls
http://www.flickr.com/photos/arshadmalik/sets/72157616172168822/
Rear wall
http://www.flickr.com/photos/arshadmalik/sets/72157616172074934/

Has somebody taken any measurements with REW?

[Ethan Winer]

Are you using a Radio Shack SPL meter? See this:

Comparison of Ten Measuring Microphones

--Ethan

[audiocrazy]

Are you using a Radio Shack SPL meter? See this:

Comparison of Ten Measuring Microphones

--Ethan

Thanks Ethan for the response but I'm using ECM8000 and I've the calibration file for the mic applied on my graph using REW.

[laserman]

audiocrazy,

Just for discovery of what is happening in the room, would you first test that other pair of floor standers I see in one picture and then please remove the GIK panels and test the Salks and other pair again.  It would be an interesting comparison and may lead to a better suggestion.      

Lou

[Vinyl-Addict]

Are you using a Radio Shack SPL meter? See this:

Comparison of Ten Measuring Microphones

--Ethan

Thanks Ethan for the response but I'm using ECM8000 and I've the calibration file for the mic applied on my graph using REW.

What soundcard are you using? IIRC, you have to calibrate the soundcard and load the calibration file prior to measuring. I could of course be wrong. It's been a long time since I used REW.
Your mic could be defective as well. Good luck in resolving this.

[audiocrazy]

What soundcard are you using? IIRC, you have to calibrate the soundcard and load the calibration file prior to measuring. I could of course be wrong. It's been a long time since I used REW.
Your mic could be defective as well. Good luck in resolving this.

My soundcard is EMU0404 USB connected to my laptop. Thanks for the reminder but I've done all the required step to use REW.

[gitarretyp]

Was this done with both speakers playing simultaneously (will lead to cancellations at upper frequencies unless equidistant to the order of the wavelength from each speaker)? If so, try repeating the measurement with each channel individually.

[TomW16]

Was this done with both speakers playing simultaneously (will lead to cancellations at upper frequencies unless equidistant to the order of the wavelength from each speaker)? If so, try repeating the measurement with each channel individually.

I am a complete newbie at this so please forgive my ignorance but wouldn't taking measurements of both speakers in stereo be the most appropriate since ultimately this is how the system would be used?  This, of course, doesn't preclude measuring one speaker at a time for investigation.

Thanks.

Tom

[gitarretyp]

I am a complete newbie at this so please forgive my ignorance but wouldn't taking measurements of both speakers in stereo be the most appropriate since ultimately this is how the system would be used?  This, of course, doesn't preclude measuring one speaker at a time for investigation.

Thanks.

Tom

Tom,

Yes and no. It's best for doing measurements in the modal region (<~ 200 Hz), but for high frequency measurements you must measure each individually (or with the mic very carefully placed) or you'll end up with the response you posted.

As an aside, it can be interesting to measure both simultaneously to see what happens to the high frequency response for even small movements of the mic.

[richidoo]

What does the FR look like with no treatment?

Get a roll of kraft paper from local art supply store. Or just use pages from newspaper for experiment. Start adding it in strips over the panels. It reflects high freqs only. Mids get through. It will not affect your bass trapping. If that works, you need less absorbtion or more reflective surface, maybe GIK diffusor over a couple panels on rear wall.

[audiocrazy]

Most people have adviced that the FR at Higher Frequency range is not the true response of the sepaker. The measurment must be take within 1 to 3 meters to get an accurate FR of the higher freq.
Here is the graph with each speaker measured separately at the listening position.
Red is Right
Green is Left

[audiocrazy]

Here is the graph without any acoustic panels. It does not make much difference in FR with or without the acoustic panels on the side walls

[Dan_ed]

Audiocrazy,

I wouldn't spend too much time chasing this. I get similar anomalies when measuring inroom response with my Behringer mic and usb sound card. If our experiences are truly the same, the roll-off shown in the measurements is not heard. Keep in mind that flat response does NOT guarantee great sound.

These measurements are good for placing speakers, testing tweaks, etc., but I try not to get caught up with how things measure as much as how things sound.

[laserman]

Thanks for the update, separate speaker measurements and the removal of the acoustic panels.  It appears this is a paradox, since apparently you liked the sound signature of the Salk ST's and yet they aren't measuring up to your expectations  ...or...

 an enigma wrapped in a conundrum. 

If you will.  If you still have those other floorstanders is there any chance you have measurements of them or could you roll them in and measure them to provide us with a comparison??

[face]

Download ARTA(it's free) and measure each individual speaker from approximately 1 meter away. 

[McTwins]

Hi
It seems that you have some sort of phase shift issue. The difference between 20Hz and 20kHz is 32Hz. You have to much bass as I see it. This is not a easy one to handle. If you can measure phase responce then you would kleerly see it.
Thanks

[youngho]

Hello, sorry about the lack of expertise, but a few thoughts and questions:

1. It appears as though you have wall-to-wall carpeting. Without knowing anything about the type of carpet or underlay, the absorption graphs from Everest's Master Handbook and Toole's Sound Reproduction show generally rising absorption from 125 Hz to 4 kHz or so. This would likely also extend into the higher frequencies, too, although it seems unlikely that it would be so linear above 7 kHz. It would be interesting to measure other loudspeakers in the room, as suggested. Also, do you find that your system sounds so rolled-off compared to a pair of quality headphones?

2. If the GiK 242 panels behaved essentially like panels of 2" thick rigid fiberglass, they would have decreasing absorption below about 1-2 kHz or so. In the context of the wall-to-wall carpeting, all this mid- and high-frequency absorption might be excessive without adequate bass trapping. Absorption of resistive absorbers can be idiosyncratic, depending on the angle of incidence, but it seems strange that the response curves with the panels seem a little worse than without the panels, unless they had some sort of peak in terms of absorption at 1 kHz or so.

3. Unless I'm mistaken, bass performance is slightly worse with the 244 panels and Monster bass trap than without them. Is there any change that these graphs are reversed?

If your measurements are correct (in terms of microphone and equipment) and correctly labelled, you might consider the following:

[bpape]

While the carpet and panels will certainly provide absorption up high like that, but it will effect primarily decay time, not frequency response - certainly not that drastic a drop.

Looks to me like there is something in the cal file or the mic or both.  I know that tweeter doesn't fall like that.  The only other thing I can think of is that somehow, maybe one tweeter is wired out of phase?

Bryan

[*Scotty*]

 audiocrazy,What does your nearfield measurement of the speakers response look like? Is it flat to 20kHz? You might treat your speakers like a giant pair of headphones and try listening to them at about 3ft. with your listening position at the apex of a triangle duplicating the proportions of your normal setup. You could then determine if having the very top end flat to 20kHz. is desirable.
Scotty

[youngho]

While the carpet and panels will certainly provide absorption up high like that, but it will effect primarily decay time, not frequency response - certainly not that drastic a drop.

Yes, I agree. "It seems unlikely that [the rising absorption curves] would be so linear above 7 kHz" was probably understated. That's why I wondered about how the room sounded compared to headphones.

Looks to me like there is something in the cal file or the mic or both.  I know that tweeter doesn't fall like that.  The only other thing I can think of is that somehow, maybe one tweeter is wired out of phase?

The individual speaker measurements show the same trend, and one tweeter cannot be out of phase with itself, as far as I know. I assume that there must be some problem with microphone or equipment. If other loudspeakers don't demonstrate this trend, then it's probably a problem with the loudspeakers. If the room sounds comparable with headphones, then it's probably a problem with the measurements. If other speakers do demonstrate this trend and the room sounds noticeably rolled off compared to headphones, then it's a problem either with the room or the playback equipment. In any case, some troubleshooting clearly needs to be done.