Why >10kHz drop so much ? - Home Theater Forum and Systems - HomeTheaterShack.com

 
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post #1 of 7 Old 08-30-16, 09:48 AM Thread Starter
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Why >10kHz drop so much ?

Hi,

I had performed a stereo measurement of my floorstanding spk at my listening position.

Spk = monitor Audio pl200
Pre = ATC LS27
Power = DIY Hypex Ncore NC400

Attached is the dB vs freq curve.
As per the title, it is common for the high freq to drop in such a way ?

Attached the rest of the plots & data-file for info.
Attached Thumbnails
Why >10kHz drop so much ?-90degree-db-vs-freq.jpg  

Why >10kHz drop so much ?-90degree-decay.jpg  

Why >10kHz drop so much ?-90degree-spectrogram.jpg  

Why >10kHz drop so much ?-90degree-waterfall.jpg  

Attached Files Aug 27 16_08_29 (LR).mdat (2.93 MB) 

Regards, E.H.
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post #2 of 7 Old 08-30-16, 10:01 AM
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Re: Why >10kHz drop so much ?

did you measure both speakers at the same time? What mic did you use and how was it orientated?
HF roll off is common when taking readings with both speakers at the same time due to phase cancellation. Also keep in mind if you had a ruler flat frequency response from 10Khz up to 20Khz your ears would be ringing, some roll off is a good thing.

Home theater:
Onkyo 805, Yamaha YDP2006EQ, Samson Servo 600 amp
3 EV Sentry 500 monitors across the front, 4 Mission 762i's Surrounds, SVS PB13U sub, Panasonic BDT220, Harmony 1100, Nintendo WiiU
Panasonic PT-AE8000 on a 120" 2,35:1 fixed screen

Living room system:
Sherwood/Newcastle R972, Mission 765's, SVS SBS02's, A/D/S MS3u sub, Yamaha YDG2030EQ
Yamaha KX-393 Tape deck, CDC 805 CD changer, Panasonic BD60, Sony turntable PS-T20
Panasonic TC-P50ST60, HD-PVR & WDTV Live, Harmony 900

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post #3 of 7 Old 08-30-16, 11:45 AM Thread Starter
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Re: Why >10kHz drop so much ?

It is taken with both spk at the same time.
mic = miniDSP UMIK-1 calibrated by Cross Spectrum Lab
90 degree (ie facing upwards).

Regards, E.H.
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post #4 of 7 Old 08-30-16, 12:17 PM
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Re: Why >10kHz drop so much ?

The drop above 10khz should not be a problem. You need to have roll off in high from about 1.5khz of about 6db per octave.
see as example my SPL curve of my Monitor Audio GR200 below with acoustical treatment and room correction, you can refer to it as target curve.

What are the dimensions of your listening room?
Do you have any acoustical treatment like bass traps and absorption panels in your room?

Your waterfall and spectrogram looks bad with frequencies that decay longer than 350ms from 10 to 400Hz due to room resonances and issues with acoustic treatments.

Please see below my spectrogram in my listening room with both speakers and try to achieve it.
Attached Thumbnails
Why >10kHz drop so much ?-spl-sub.jpg  

Why >10kHz drop so much ?-spectrogram-sub.jpg  

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post #5 of 7 Old 08-30-16, 06:05 PM
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Re: Why >10kHz drop so much ?


As mentioned, measuring both speakers simultaneously with a sweep can cause reduced highs. Same with a 90-degree orientation if you’re not using a 90 degree calibration file.

Regards,
Wayne A. Pflughaupt



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post #6 of 7 Old 08-30-16, 09:09 PM Thread Starter
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Re: Why >10kHz drop so much ?

Room dimensions is about: 4.5 x 3.9 x 2.9 M (14.7 x 12.8 x 9.5 Ft) - Width x Depth x Height
Unfortunately, the front & the back walls are all glass surfaces - I had place wooden blinds on them.
Other than that, there are zero treatment done on the room (Yet ).
NOTE: For bass correction, should be using DRC cause don't think want to put those big bass trap inside the room.

Was provided 6 files from cross spectrum: [narrow_band_response_XX_degree.frd] & [one_third_octave_band_response_XX_degree.frd]. Where XX = 0, 45, 90.

Make use of the narrow band 90 degree file as the calibration file for REW.
Also using a camera tripod place on top of the sofa.

Attached the front view, seating position view and side view of the room for references.
Attached Thumbnails
Why >10kHz drop so much ?-front.jpg  

Why >10kHz drop so much ?-side.jpg  

Why >10kHz drop so much ?-sp.jpg  


Regards, E.H.
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post #7 of 7 Old 08-30-16, 09:36 PM
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Re: Why >10kHz drop so much ?

You would benafit greatly with some acoustic foam behind the front speakers and a simple throw rug on the floor.

Home theater:
Onkyo 805, Yamaha YDP2006EQ, Samson Servo 600 amp
3 EV Sentry 500 monitors across the front, 4 Mission 762i's Surrounds, SVS PB13U sub, Panasonic BDT220, Harmony 1100, Nintendo WiiU
Panasonic PT-AE8000 on a 120" 2,35:1 fixed screen

Living room system:
Sherwood/Newcastle R972, Mission 765's, SVS SBS02's, A/D/S MS3u sub, Yamaha YDG2030EQ
Yamaha KX-393 Tape deck, CDC 805 CD changer, Panasonic BD60, Sony turntable PS-T20
Panasonic TC-P50ST60, HD-PVR & WDTV Live, Harmony 900

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