# Room analysis before more treatments



## mtbdudex (Jan 2, 2008)

Need to do some room analysis before I proceed with any more treatments....
Rear wall in process broadband bass traps









LH side and RH side 1st reflection absorption panels
















Acoustic cloud for 2nd row 1st reflection


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## markus76 (Sep 13, 2008)

*Re: Can't get REW5 for Mac inputs to work*

Mike,

It would be much more effective to arrange the corner blocks like this:


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## mtbdudex (Jan 2, 2008)

*Re: Can't get REW5 for Mac inputs to work*



markus76 said:


> Mike,
> 
> It would be much more effective to arrange the corner blocks like this:
> 
> ...


Markus76;

Thank you for your opinion, can you give me some fact based data to justify your statement on the rear wall broadband absorber I'm in process of making?

Ok - so I hate bad karma, therefore to end on a positive note, here is a star trail picture I took last weekend:
Each is multiple 20 sec exposures stacked, taken with T1i + 15-85 lens @ 15mm, f3.5, ISO800.

North star trails (55min total exposure).....................................South star trails (45 min total exposure):
















and a 17 sec video sequence...


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## markus76 (Sep 13, 2008)

*Re: Can't get REW5 for Mac inputs to work*



mtbdudex said:


> Thank you for your opinion, can you give me some fact based data to justify your statement on the rear wall broadband absorber I'm in process of making?


Porous absorbers work at locations where there is sound particle velocity. Sound particle velocity at the surface of a wall is zero (maximum pressure). It has its maximum at 1/4 of the wavelength. For 40Hz this would be 2.15m (7 ft.). So the more absorption you place away from a wall the more effective it becomes at lower frequencies.

The corner blocks at the back should be floor to ceiling. Treat as many corners as you can - there are 12 of them.

Objects in the vicinity of loudspeakers cause very early reflections that have a negative impact on summing localization. Equipment racks, decoration, drum sets, coffee tables, etc. can cause very early reflections that are detrimental to sound localization.

Using a center speaker that is the same as the other mains is probably one of the biggest improvements in sound quality. Center speaker below (or above) the screen have two problems. a) Sound is coming from the wrong direction. b) The directivity is most likely different from the other mains so the center will sound different.


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## DanTheMan (Oct 12, 2009)

Markus, that's very clever. Why didn't I think of that? (don't answer that  )

Dan


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## markus76 (Sep 13, 2008)

Mike, when looking at your pictures, your seating seems to prevent sitting in the main listening position? Please don't get me wrong but this is like driving a Porsche 911 on a dirt road. You really should change this because sitting in the main listening position is one of the most basic requirements of any loudspeaker based sound reproduction system (with the exception of wave field synthesis). Yes, multichannel does improve the experience at other seats but localization and spatial reproduction can only be optimal at one single seat.


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## mtbdudex (Jan 2, 2008)

markus76 said:


> Mike, when looking at your pictures, your seating seems to prevent sitting in the main listening position? Please don't get me wrong but this is like driving a Porsche 911 on a dirt road. You really should change this because sitting in the main listening position is one of the most basic requirements of any loudspeaker based sound reproduction system (with the exception of wave field synthesis). Yes, multichannel does improve the experience at other seats but localization and spatial reproduction can only be optimal at one single seat.


Markus - here is my HT layout:









I do appreciat people sharing their experiences, that is how a community learns.

There is a balance to treatments vs the room space aestics, I did understand why you stated "turning the bass traps", however that won't work in my space due to physical interfence with the 2nd row seats.

I'm not trying to dial in any 1 seat location, rather compromise and make all the seats "decent", that's what a HT is for. 
If a listening room, then there would be different goals/objectives.

I consider the 2nd row over the 1st row for primary seating, due to the 2nd row has HT seats while the 1st row is still my old getto-looking couch....seems something in the home always gets priority for $k over getting a 1st row HT seat. Still, I'm taking care of 1st row seating acoustics also. 

Here are graphs of my IB sub, no EQ, with the treatments as show earlier here:
(fwiw, my 2nd seat riser is also a broadband bass trap as well)
2nd row all 4 seat positions









1st row all 3 seat positions









Overall I'm impressed by how they have helped the room bass acoustics.

fwiw, I've read "Master Handbook of Acoustics" by F. Alton Everest 2 years ago and quite a lot of other articles on acoustics. 
However, reading theory is 1 thing, and then putting it into action, making treatments, connecting the dots, having the "light" go on when theory and reality come together. 
That's the fun part of this hobby, the DIY thing and also grasp of the science behind it.
(I have a MSME, so math is very easy for me. At times, I wish some of the equations presented in the "Master Handbook of Acoustics" had their derivation available (besides footnotes), nothing like understanding equations by grasping their derivation. That would be something a future iPad verson having would be worthwhile to me, dynamic link to footnotes)

My friends and family think I'm a geek, but they also like me explaining the "What's/How's/Why's" of stuff.
However, I do have to preface to them what I leaned is via reading books/OJT/forums/etc, that I'm NOT certified in acoustics so I'm just an amatuer in that regard.


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## markus76 (Sep 13, 2008)

I disagree on most things you've said about "aestics" and "goals/objectives" so it's probably more constructive to concentrate on the graphs you've posted. Are those graphs smoothed? Please switch it off and make sure the frequency resolution is 1Hz or better. That will result in a better representation of what is heard.


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## mtbdudex (Jan 2, 2008)

markus76 said:


> I disagree on most things you've said about "aestics" and "goals/objectives" so it's probably more constructive to concentrate on the graphs you've posted. Are those graphs smoothed? Please switch it off and make sure the frequency resolution is 1Hz or better. That will result in a better representation of what is heard.


markus76, you seem...very strong in your opinions.

Can you:
-post some picts of your HT
-your before treatment/after treatment analysis of your HT
-whatever acoustic certification you have
-if you represent an acoustic related company or work at one I'd like to review that site
-have you professionally consulted on other peoples HT acoustics?

Being a registered Professional Engineer for 20+ years (Michigan), I know when to speak with authority when the subject is in my field of expertise, both theory and practical, and when to say "in my opinion".
http://www.nspe.org/Ethics/CodeofEthics/index.html


> Engineers shall perform services only in the areas of their competence.
> 
> 1. Engineers shall undertake assignments only when qualified by education or experience in the specific technical fields involved.


Trust, but verify.


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## DanTheMan (Oct 12, 2009)

Markus has been doing this stuff for a long time--no dummy for sure. I'll vouch for him there and his website is also full of useful stuff. 

Not that you asked for my voucher,

Dan


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## markus76 (Sep 13, 2008)

Mike, here's a good read with more up to date information from someone that definitely has the credentials you're looking for: "Sound Reproduction" by Floyd Toole.

Good luck with your home theater build.


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## mtbdudex (Jan 2, 2008)

markus76 said:


> Mike, here's a good read with more up to date information from someone that definitely has the credentials you're looking for: "Sound Reproduction" by Floyd Toole.
> 
> Good luck with your home theater build.


That's a great book Markus, I see lots of material there that I downloaded 3 years ago from the white paper series, http://www.infinitysystems.com/home/technology/technology_whitepapers.aspx?Language=ENG&Country=US&Region=USA, based on recommendation of an acoustic friend who left work 2 years ago to return to Harman Becker.
(he printed me quite a few AES papers also when I was studying subwoofers, I miss him as my local "free" acoustic subject matter expert, we've lost touch of each other)

I've not sprung for that book - yet, it does cover similair material to the "Master Handbook of Acoustics" which I have (4th edition), plus from what I can see on the index pages (via amazom) seems more specific to HT, its in my shopping basket now, thx for advice. Peace.


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