Room Response - comments, please! - Page 2 - Home Theater Forum and Systems - HomeTheaterShack.com

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post #11 of 25 Old 04-06-13, 01:14 PM Thread Starter
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Re: Room Response - comments, please!

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Wayne A. Pflughaupt wrote: View Post

Our calibration file is generic; you canít be absolutely certain that your measured response is accurate without a custom calibration file. Mic orientation can make a difference too, whether or not you measured with it pointing at the speaker.

Regards,
Wayne
Hello Wayne,

Thanks for your reply.

I'm unclear about the custom calibration file - where would I get that? When you say that your cal file is generic, perhaps you could elaborate? How accurate can I expect my ECM8000 to be using the HTS cal file?

Mic orientation was in the listener position, pointing upwards and angled forward approx. 20 degrees.

JPC
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post #12 of 25 Old 04-06-13, 01:45 PM Thread Starter
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Re: Room Response - comments, please!

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AudiocRaver wrote: View Post
In a fairly live typical home theater or music listening room, the high-frequency buildup due to reflections will indeed seem harsh with a flat response. The rolloff you see is not too far from some suggested "target curves" for rooms like that, the intent being to help tame that harshness. A studio control room or mixing room, with well-damped acoustics, is generally tuned for flat response and it seems "just right" because of those acoustics.
Hi AudiocRaver,

OK, thanks again.

You've made some very interesting points that I would like to fully understand.

You point out that the HF buildup in a typical listening room will seem harsh with a flat response. So, if a studio control room is tuned for a flat response, why does it sound "just right"? I guess what you are saying is that the flat response in itself does not prevent the HF buildup due to reflections - is that correct? When you referred to "target curves" for listening rooms, where could I get hold of these?

JPC
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post #13 of 25 Old 04-06-13, 02:21 PM
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Re: Room Response - comments, please!


Hey John,

Quote:
jaypeecee wrote: View Post
I'm unclear about the custom calibration file - where would I get that?

Read more: http://www.hometheatershack.com/foru...#ixzz2PiFqul6N
The mic has to be calibrated by a lab, which compares its response against a reference mic and creates a calibration file to compensate for the former’s deviations from flat response. Sounds expensive, but you can buy calibrated mics from Cross Spectrum for less than $100.

Quote:
How accurate can I expect my ECM8000 to be using the HTS cal file?

Read more: http://www.hometheatershack.com/foru...#ixzz2PiEisd00
Here’s a graph from Cross Spectrum showing response deviations among a number of samples:




Quote:
Mic orientation was in the listener position, pointing upwards and angled forward approx. 20 degrees.
That alone would account for the high-end droop you’re seeing. Our generic calibration file is 0-degree, meaning it was generated with the mic in a horizontal position. With such a file, the mic should be pointed at the speaker and tilted up 20-degrees or so. The orientation you used, straight up and angled forward 20-degrees, requires a 90-degree calibration file.

Regards,
Wayne



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post #14 of 25 Old 04-06-13, 02:40 PM
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Re: Room Response - comments, please!

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jaypeecee wrote: View Post
Hi AudiocRaver,

OK, thanks again.

You've made some very interesting points that I would like to fully understand.

You point out that the HF buildup in a typical listening room will seem harsh with a flat response. So, if a studio control room is tuned for a flat response, why does it sound "just right"?
JPC
Nearfield listening in the studio VS normal listening positions in a home environment are very different.

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Onkyo 805, Yamaha YDP2006EQ, Samson Servo 600 amp
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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
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post #15 of 25 Old 04-07-13, 05:38 AM Thread Starter
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Re: Room Response - comments, please!

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Wayne A. Pflughaupt wrote: View Post

Hey John,

The mic has to be calibrated by a lab, which compares its response against a reference mic and creates a calibration file to compensate for the former’s deviations from flat response. Sounds expensive, but you can buy calibrated mics from Cross Spectrum for less than $100.

Here’s a graph from Cross Spectrum showing response deviations among a number of samples:




That alone would account for the high-end droop you’re seeing. Our generic calibration file is 0-degree, meaning it was generated with the mic in a horizontal position. With such a file, the mic should be pointed at the speaker and tilted up 20-degrees or so. The orientation you used, straight up and angled forward 20-degrees, requires a 90-degree calibration file.

Regards,
Wayne
Hi Wayne,

Many thanks.

For some reason, the links you have provided above take me back to this post.

With reference to the Cross-Spectrum graph showing response deviations for the Behringer ECM8000, it is apparent that this microphone has a rising response at the HF end of the audio range. That being the case, my room response at the listener position will be even further down at the top end than I had originally thought - to the tune (!) of a further 4dB or thereabouts. Your last comment above is therefore of particular relevance. The orientation for my test microphone was based on something I had read on the HTS forums but perhaps I got it wrong. It did seem odd pointing the microphone upwards. Looks like I need to repeat all my measurements with the ECM8000 tilted upwards 20 degrees from horizontal and pointing towards the loudspeakers.

Now, what about the 100Hz to 700Hz dip on my room response? Any thoughts?

Thanks again.

John

Last edited by jaypeecee; 04-07-13 at 06:12 AM. Reason: More clarification!
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post #16 of 25 Old 04-07-13, 05:44 AM Thread Starter
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Re: Room Response - comments, please!

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tonyvdb wrote: View Post
Nearfield listening in the studio VS normal listening positions in a home environment are very different.
Hi Tony,

OK, many thanks.

John
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post #17 of 25 Old 04-07-13, 09:30 AM
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Re: Room Response - comments, please!

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jaypeecee wrote: View Post
...the HF buildup in a typical listening room will seem harsh with a flat response. So, if a studio control room is tuned for a flat response, why does it sound "just right"?
Here is how I understand it: In your home environment there is a lot more LF energy than HF energy, relative to them being pretty equal in a "dead" studio control room, for 2 reasons - 1) speaker directivity being broader at LF, more total energy being dispersed into the room, not being soaked up by room treatment, and 2) almost all untreated rooms have longer reverb times at LF, getting shorter and shorter as frequency increases. So when you equalize for flat response in your home environment, the sound is more & more direct as frequency increases, and seems more and more "beamed at you." It is a relative perception issue, the more direct at HF vs. the more diffused at LF, that makes the HF seem harsh in contrast, needing to be ramped down to compensate. In the studio control room, all the sound is "beamed at you" and does not seem harsh with a flat response setting.

How much HF attenuation is called for to compensate? The effect in your lively home environment depends on many factors, the speakers, placement, the room, personal taste, & humidity are all significant, so no 1 target curve fits all. Some of the target curves out there compensate with 10 db attenuation at 10 KHz. I think that is way too much. I run my own speakers down only 2 db at 10 KHz, and that works great for me. It is known that we tolerate (do not notice) dips or attenuations in frequency response much more easily than peaks or increases, so maybe it is partly untrained listeners quickly selecting target curves that are super-easy on the ears and not noticing all the detail they are missing out on. No insult intended to those who have tried target curves and like them. It seems like a lot of listeners grab target curves out of convenience rather than letting their ears guide them.

I think target curves are overrated, do not see any 1 generic curve fitting all speakers in all rooms. Start out flat, listen a bunch, if it is too harsh, hinge it at 1 KHz and drop the top end 2 db and see how that works for awhile, go 2 db at a time and stop when you like it. Probably no one on the planet will agree with me, so if another explanation makes more sense to you, go with it.

Harmon, B&K, JBL all have published target curves. I don't have any bookmarked, but they shouldn't be hard to find with a web search. There was some lively discussion at this thread awhile back, you might find some of it interesting.
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post #18 of 25 Old 04-08-13, 06:25 AM Thread Starter
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Re: Room Response - comments, please!

Hi AudiocRaver,

Many thanks for your comprehensive reply - it is greatly appreciated.

You have provided much food for thought. I must check out the effect of humidity on sound reproduction. It also occurs to me that, if humidity plays a part, then what about temperature and barometric pressure?

Once again, thanks.

John
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post #19 of 25 Old 04-18-13, 06:40 AM Thread Starter
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Re: Room Response - comments, please!

Hi Folks,

In view of Wayne's comment "That alone would account for the high-end droop youíre seeing" in response to the ECM8000 orientation that I had used for all my REW measurements to date (red plot), I repeated my measurements with the ECM8000 pointing to the mid point between the speakers and tilted upwards 18 degrees (black plot). See below. It is clear that there is virtually no difference in HF response as a result of changing the mic orientation in the listener position.

As a result of the above comparison, I once again repeated the measurements for each individual speaker at a distance of 0.5 metres with the ECM 8000 horizontal, on axis and pointing half way between the two drivers. This is shown in the green plot. At 10kHz, the SPL is 9dB higher than at the listener position.

For simplicity, all plots are for the RH channel only.

JPC
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post #20 of 25 Old 04-18-13, 03:55 PM
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Re: Room Response - comments, please!

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jaypeecee wrote: View Post
It is clear that there is virtually no difference in HF response as a result of changing the mic orientation in the listener position.
I have performed similar tests in the past and come to the same conclusion. Pointing the mic 180 degrees away from the speaker causes HF droop of several db. Anything less than 90 degrees off axis, the measurement difference was less than 1 db and that was all above 10 KHz where no EQing is done anyway. There is a lot said about mic orientation and it does no harm to follow the common guidelines so I don't argue about it, but if someone asks how much difference it really makes, this is my answer: At 90 deg or less off axis - for all practical purposes - none.
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