read the ETC ( John ) - Home Theater Forum and Systems - HomeTheaterShack.com

Old 10-04-15, 09:40 AM Thread Starter
Shackster

giordy60

Join Date: Aug 2013
Location: cremona (IT)
Posts: 40
read the ETC ( John )

Hello John,
I can not solve this problem:
I measured with REW my listening room and I must say that the measures are not bad but there is one thing I can not understand:
the answer in the environment is good
the level of distortion is acceptable
the impulse response is good
the value is good dell'TR60
the waterfall is acceptable
but on reflection I ETC to 1,93ms and a 5.93 ms that I can not delete.
I tried it with the classical string to figure out where are these thoughts .... but nothing to do.
(I did so: the sound travels 344 meters per second then a millisecond equals 34 cm.
First reflection: 34 X 1.93 = 65.62 cm + (distance monitor - microphone) 208 cm = 273.62)
there is nothing at that distance that generates the reflection.
I enclose the mdat for easy reading
thank you
Attached Files ott 4 sx+dx.mdat (3.18 MB)
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Old 10-07-15, 03:37 PM
REW Author

John

Join Date: Apr 2006
Location: UK
Posts: 6,302
Re: read the ETC ( John )

Hi Giordy, your approach is correct, so if the distance from mic to speaker is 2.08m the path travelled by that first reflection at 1.93 ms will be 2.74m. Depending on the height of the mic and speaker drive units, that would be about the distance travelled by sound reflected from the floor. One way to narrow down where a reflection is coming from is to place a very absorbent panel or material in different positions around the mic or the speaker (above, below, left, right) and see which location most reduces the height of the reflection.
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Old 10-07-15, 03:49 PM Thread Starter
Shackster

giordy60

Join Date: Aug 2013
Location: cremona (IT)
Posts: 40
Re: read the ETC ( John )

Quote:
JohnM wrote: View Post
..... One way to narrow down where a reflection is coming from is to place a very absorbent panel or material in different positions around the mic or the speaker (above, below, left, right) and see which location most reduces the height of the reflection.
What can I use as a material to be placed around the mic....use a panel of polyurethane foam + pyramid might be correct for a test ?
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Old 10-07-15, 04:01 PM
REW Author

John

Join Date: Apr 2006
Location: UK
Posts: 6,302
Re: read the ETC ( John )

That should work, something that is a good sound absorber - the more sound it lets through, the less the effect on the peak. You could even use something solid, although it would reflect the sound a create a peak somewhere else you should still be able to see if it affects the peak you are interested in.
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Old 10-07-15, 04:05 PM Thread Starter
Shackster

giordy60

Join Date: Aug 2013
Location: cremona (IT)
Posts: 40
Re: read the ETC ( John )

OK, I see what I have at home.
thank you
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Old 10-11-15, 08:14 AM Thread Starter
Shackster

giordy60

Join Date: Aug 2013
Location: cremona (IT)
Posts: 40
Re: read the ETC ( John )

Hello John, problem solved.
reflection was created in the space between the couch and the rear wall, I put (temporarily) a couple of pillows, then put a panel QRD.

here is the extent

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