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Speaker high frequency roll off at 3.5khz - Is this normal?

napuli

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I was using REW with Dayton Audio UMM-6 to measure room acoustics and adjust position of my Vandersteen 2ce Signature II and dual Rel T9i subwoofers. I was hoping for some feedback regarding the high frequency response. To me it looks like it starts to roll off early at about 3.5Khz. If I put the microphone in front of the tweeter I get a more normal response, so pretty sure is a result of tweeter dispersion. I would like to see some of your measurements if you have any. With microphone at the listening position. Just wondering if my speakers are underperforming or if this is normal.

Graph shows average of L&R speakers with both subs - psychoacoustic.
 

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dougi

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I don't think it is normal. What setting was the treble trim? Measure at 1m on tweeter axis and compare with stereophile measurements you can find. That will give you a better picture. Use time gating if required to get a good view of it above the bass region.
 
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napuli

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I kept the trim at zero.

I know I can get a better response if I measure close to the tweeter. However, my goal is to use REW to help me improve speaker response at the listening position. I am just wondering if the graphs I am seeing for other speakers were done like you suggested vs 9 feet away like I did.
 
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napuli

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Are you aiming the tweeters at you, toe in? If they are parallel to the wall, the tweeters narrow directivity will fall off, but woofers will be much less affected by where you point them.

https://www.crutchfield.com/S-GS8xV3u3Fci/learn/home-stereo-speaker-placement.html

No toe in on the measurement I showed you. I did experiment with various amounts of toe in and it did increase the response a little but still showing a downward slope from 3.5Khz.

Tilting the speakers back by about 5 degrees helped as well. I am wondering if I am completely off axis? So hard to tell with these speakers because the drivers are not visible.

One thing I didn't mention is that I do have GIK bass traps on the side walls. I am now wondering if this is the reason why I am seeing the roll off? I guess I need to experiment. I don't normally keep the speaker on slabs but this way I can move them around more easily when testing.
IMG_3103.jpg
 
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fieldcar

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Very clean looking setup!

The bass traps shouldn't affect the treble. If anything, you would get a flatter response by smoothing bass peaks/room modes.

Since you have them on slabs/risers, it may be raising the center of the vertical axis of the tweeter too. I would also try to tilt the speaker down a bit if they are adjustable. If that doesn't do it, it could just be the speaker's design. Best of luck!
 
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