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post #31 of 48 Old 05-07-2012, 06:24 PM
 
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Quote:
Originally Posted by BruceD View Post

I'm sorry to say you are giving false and non-helpful information to the poster and I sure wish you would cease and desist. You fundamentally don't understand what you are talking about and disagree with many industry heavyweights on this.

Go back to your quoted post and stay out of this one, we don't need your type of help here, because you have a distorted viewpoint as a seller of high-end audio equipment. You should read "Sound System Engineering" by Davis and Patronis to get a better education on facts.

Good points however, greed is very powerful. As such, what you posted will simply be deflected and redirected by him.
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post #32 of 48 Old 05-07-2012, 07:25 PM
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Originally Posted by BruceD View Post

read "Sound System Engineering" by Davis and Patronis

+1 over and over and over
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post #33 of 48 Old 05-08-2012, 04:20 AM
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Originally Posted by Martycool007 View Post

Thanks for that wealth of information, Localhost127! Man, that really helped me and was probably the most helpful post I have ever read.

Ok so now I understand that I need to run REW and measure the ETC so that I can see what destructive specular interference I have at my listening position, due to room boundaries or other reflection points. After I take my ETC measurements to identify what the high gain reflections I am dealing with are, then I will work out the math and treat my room with absorbion panels in those particular places, then remeasure and replete.

I will also run a waterfall plot so that I can see what kind of LF decay times I have. Keep in mind that i have never used REW, although i will soon, and I have no idea what the waterfall plot looks like. How do I see, by looking at a waterfall plot, what kind of low frequency decay times I have and where the room modes are at? Also how will this tell me where and how I need to treat my room in order to lower or shorten decay times in the low frequency region?

Are there any other usefull measurement tools in REW besides the ETC, which measures gain vs time, and the waterfall plots, which measure LF decay times? What other factors are important in treating rooms, and, how can they be measured?

Thanks for your help Localhost127! Kudos to you for taking the time to explain all of that!

Good questions that you may need answers to down the road, but first get your feet wet!

Stay the course - get the equipment you plan to get and be prepared to spend a lot of time with it.

You are probably going to run out of time and energy before you run out of things to fix, even with just the tools that have been discussed so far.

Don't fall prey to what seems to be a common problem around here - wasting time and energy on head games when practical hands-on experience and research driven by what you find in the real world will educate you best.
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post #34 of 48 Old 05-08-2012, 05:50 PM
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Ok so I about to order a Behringer ECM-8000 mic, a Behringer Xenyx 502 mixer (for providing power to the mic) and a Creative Labs Sound Blaster Live outboard sound card, so that I can do some measurements using REW via my laptop. This should be all that I need, baring cables and REW software, right? Can anyone suggest any good sites to order this stuff from?

I was wanting to measure both my 2 channel system, and, my home theater system. My theater system is made up of Definitive Technology speakers, flagship models btw. I am unsure if measuring this system is even going to produce any helpfull info because both of my mains, as well as my surrounds, are all bipolar. Have any of you guys ever measured bipolar speakers? They depend on things such as reflections off of the front walls, as that what they were designed to do. Is this going to create a measurement nightmare? What about treating my theater room? I would guess that regardless of how they measure, I could probably really mess up the overall sound of the entire system by attempting to treat this room. I guess the only way to know, is to try it and see. Any advise?
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post #35 of 48 Old 05-09-2012, 10:27 AM
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Quote:
Originally Posted by Martycool007 View Post

Ok so I about to order a Behringer ECM-8000 mic, a Behringer Xenyx 502 mixer (for providing power to the mic) and a Creative Labs Sound Blaster Live outboard sound card

You'll probably do better getting a USB sound card that has microphone inputs with phantom power. It might cost a little more, but the quality will be better and it's easier to connect. This has one microphone input for $99:

http://www.bhphotovideo.com/c/produc...Interface.html

And this model has two for only $15 more:

http://www.bhphotovideo.com/c/produc...USB_Audio.html

Quote:


Have any of you guys ever measured bipolar speakers? They depend on things such as reflections off of the front walls, as that what they were designed to do. Is this going to create a measurement nightmare?

I don't recommend that type of speaker. You don't want the sound of reflections in your room drowning out the sound in the recordings.

Quote:


What about treating my theater room? I would guess that regardless of how they measure, I could probably really mess up the overall sound of the entire system by attempting to treat this room.

Treating your room will only improve it. More here:

Acoustic Basics

--Ethan

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Ethan's Audio Expert book

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post #36 of 48 Old 06-24-2013, 04:19 PM
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Hi, I'm new at this forum and I enjoy a lot all the comments here and the helpful you are with everyone here.

Ethan, I recently checked some of your videos about acoustic basics, bass traps and room treatment, I'm trying to find an online room simulator, but I can't find one.

I know this thread is a bit old, but I think this is the right place for my problem.

I'll try to be explicit and give you the more detailed explanation I can, so thanks in advance for your help.

I have a VERY LITTLE ROOM for my very simple home theater, I bought recently the ONKYO HT-S9400THX, and my room is also an odd shaped room.

Dimensions are

Back Wall 11.5' with a window of 3.3'H x 6.6'W at 8" from the right wall and 3.5' from the floor

Right Wall 9.85' with a window of 1'H x 2'W at 0" from the back wall and 3' 2" from the floor

Left Wall 12.1' this wall is particularly segmented first a 5' wall from the back wall, a 2'4" door entrance with a step of 9"H, next 1'2" wall, next another door entrance of 3' and a 7" wall at end cornering with front wall

Front Wall 3.8' (This is a projection wall)

Ceiling 9.85'

At first I had too much echo but after running Audyssey everything improves, but of course I wasn't really happy with the acoustics but it was just fine, two weeks ago I upgraded my system starting with an Onkyo NR3009 Receiver and OPPO BDP-93 NuForce Extreme Edition, the problem is this onkyo is A LOT BETTER than the in box Onkyo 9400THX receiver, the sound is much crisp and clear, but with my problematic room, after several Audyssey calibrations the sound is very fatiguing and annoying because the high frequencies from the early reflections, the bass is now boomy, etc

Because my little space I opted for Front Wide Speakers, So I have 7.1 with surrounds, fronts, front wides, center and sub, again for the little space I have, and the fact I'm up to the back wall my surround speakers are placed totally at the back corners, so if I put bass traps I can't go all the way from ceiling to the floors because the speakers are on the way, all my speakers are at ear level, for the window I have at my right I couldn't put that a little above my ear level.

I really need help to treat this room the best possible, since my space from the front wall is so little I have my seats all the way back at 1" from my back wall, and the couch back is about 8"

So, what is the best treatment combining bass traps, absorbers and diffusers for this very odd type of room?

In the future, maybe after a year from now I can seal the 2 windows but right now they will have a heavy blackout curtain.

Of course, after I treat the room entirely I will upgrade my speakers too, with:

- Polk Audio FXI A4 Surround Speakers
- Polk Audio TSi500 Floorstanding Speaker
- JBL LC1 3-Way Center Channel
and I suppose the wides will still be the same, I know maybe is too much for that little room, but I wanna have a good equipment for a greater room in the future.

I would benefit too much for wider bass traps? because my room is so little 6" corner bass trap kits would be fine?? or 8" would be a dramatic difference in this case???

Thanks in advance for your soon response.

And please if you know an online room simulator or something like that to explain me better I would appreciate that.

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post #37 of 48 Old 06-25-2013, 06:45 AM
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After you treat your room there's a good chance you'll find that your current speakers are fine! And there's no need for "room simulation" software either.

A small room like that needs as many bass traps as you can manage. You'll also need absorbers at the side-wall reflection pints, and especially on the rear wall behind you. Diffusers on the rear wall work even better than absorbers, but good diffusion costs more than absorption whether you buy commercial products or make your own because it's more complicated to build. Is the room yours alone letting you do whatever you want?

That's about it! If you saw my Acoustics Basics article linked above, you'll have a good handle on what is needed.

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post #38 of 48 Old 06-25-2013, 08:21 AM
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Thank you so much for your soon response Ethan, I was exactly thinking about maybe after room treatment my little speakers maybe are just fine to that little room, and that's another good reason to treat the room before, yesterday I reinstalled my speakers a little lower after reading your acoustic basics article because my tweeters were a little upper my ear level.

About your question about if is my room alone and aesthetics are not a problem, that room will be just for 20% music listening and 80% movies, so if you have any suggestion given my room specifications I'll be glad rolleyes.gif

My projector screen is 80" but I was thinking about the speaker placement, how important is the 60 degrees angle between the listener position and front speakers? it is too important the speakers are just right next to screen? Because right now my speakers are 60 degrees wide angle from seating position, but the speakers are a a little separated from the screen, and I feel almost everytime in movies that the sound is too much far from the image i'm viewing, I don't know if this is for the reflections or lack of treatment generally but, if I put speakers right next to the screen keeping the 60 degrees angle, I must sit much closer to the screen and for 80" maybe that would be a problem, I'm not sure yet.

For my room dimensions do you think I'm just OK all the way back to the back wall or maybe is better sitting a little forward?

Last question, for my room dimensions bass traps and corner kits of 6" would be good? Because I see 8" bass traps almost double the price and 12" almost triple, so 6" would be good? or I must invest more on 8" or even 12", I love the diffusers idea, but you are right they are really expensive, and in my case I'm all the way back the diffusers will help that much vs the absorbers? but no bare wall of course, I'm thinking on buying 2'x4' panel absorbers that's right for side walls? o must go all the way from floor to the ceiling?

Sorry for bothering you with all this questions, but I don't know you personally of course, but I've seen your videos and I've been reading your posts for several weeks now, and I personally respect your opinions so much at this point.

I was looking around for some diffusers and absorbers, I was thinking in this as diffusers


An this as absorbers


The back wall of my room is 11.5 and I was thinking about using 10' diffusion absorption mixed as this:

2'Hx1'W AB / 2'Hx2'W DIFF / 2'Hx1'W AB / 2'Hx2'W DIFF / 2'Hx1'W AB / 2'Hx2'W DIFF / 2'Hx1'W AB or I can double the height if necessary, any suggestion about this would be appreciated too.

Thanks in advance for your response again Ethan.


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post #39 of 48 Old 06-26-2013, 12:45 PM
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Neither of those products you show are real diffusers. This video may help:

All About Diffusion

As for your other questions, this short article explains about speaker and listening position placements:

How to set up a room

Yes, the angles are important (within reason), and sitting directly in front of a reflecting wall is best avoided if possible.

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post #40 of 48 Old 06-27-2013, 06:27 AM
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Thanks again for your comments Ethan, I view the videos and are very helpful as usual, I prefer to put only absorbers because of the little space is not functional to me a diffuser almost hitting the back of my head, so absorbers will be in my case.

I have a last question, this room next is not my case of course, but is the third time I look this setup of absorbers and diffusers on the internet, and I don't understand why...



Note that absorbers and diffusers on side walls are alternate, where an absorber is in the left wall, a diffuser is set on the right wall, why is that? they not need to be symmetric?

Is that right? is that normal?




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post #41 of 48 Old 06-27-2013, 11:53 AM
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Is that right? is that normal?

Probably not. biggrin.gif

Where did that image come from?

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post #42 of 48 Old 06-27-2013, 03:22 PM
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Is there an ideal thickness for treating sidewall reflections? Is there enough acoustic energy at these points to see a benefit going from 2" to 4"?
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post #43 of 48 Old 06-27-2013, 04:50 PM
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Is there an ideal thickness for treating sidewall reflections? Is there enough acoustic energy at these points to see a benefit going from 2" to 4"?
It is not a matter of energy but frequency response at which it is effective. Ideally, the absorption so "broadband" meaning it goes down to a few hundred hertz (so called transition frequencies). To get there, you need 4 inches with typical absorbers. Here is a simulation of a 4 inch absorber (with or without an air gap behind it):

i-GXX8zzp-XL.png

As you see in the blue graph, it gets down to few hundred hertz at 4 inches. If had a thinner panel, it would lose effectiveness at a higher frequency. What that would do then is filter out the high frequencies but not low. In essence, it would "EQ" the reflections making them sound more different than the direct sound of the speaker which is not a good thing. You can actually damage the sound of a good speaker that way.

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post #44 of 48 Old 06-27-2013, 11:38 PM
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I found two of this set-ups in hometheater.com and the third I don't remember where it was.

http://www.hometheater.com/content/acoustics-101\

http://www.hometheater.com/content/room-acoustics

But the first link article in the description says that must be parallel or symmetric, but the image is misleading that, the second one just shows the image and no clarifies that.

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post #45 of 48 Old 07-08-2013, 04:31 PM
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Hi again Ethan,

Thank you so much for being so kind with me and your support!

This long weekend I've been rearranging everything and re-orientating everything too, because I know the couch up to the back wall is not the best for acoustics.

My Home Theater Room is under construction so I can change anything before it goes, so any suggestions you have can affect my room orientation and listening position.

I moved all 90 degrees to the right so now I'm watching the previous right wall as my new front wall, I think I will seal forever the window in my front wall, and if you think is really necessary I can seal the right window too.

I moved the couch forward 3.5 feet so my Main Listening Position is better located respecting the Dolby and THX angles. So. what do you think?? I sketched and pictured everything, so you can visualizes it more clearly

In the sketch there are 5 side surround speakers, as you can see, I had a problem with a monopole speaker just behind the entrance door, so today I bought a polk audio dipole/bipole speaker to place it in a 90 degrees angle, the 2 polks to the left is because I'm thinking about the angled wall, what is the best location for that speaker... but the monopole side surround speakers will be rear surrounds today.

I draw the corner bass kit I already have, they are only 8" and I have 8 additional bass traps 8"x8"x24" too.

My walls will be painted in dark gray or black, I don't know yet, but that's irrelevant for audio purposes.

Now I'm 3.5 feet from back wall, remember please my 9.85" do you think I will have any benefits from diffusion with this arrangement at any point? could be ceiling higher back wall, etc.


Of course the doorway behind the couch will have a door installed, take in count the open space up in the back wall, I can seal it of course if you suggest is really necessary.

Back Wall



View from the Top


Front Wall



Left Angled Wall



Right Wall



Thanks in advance for your response and sorry for taking so much of your valuable time to make a decision.

David
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post #46 of 48 Old 07-09-2013, 01:21 PM
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The setup in your new drawing looks good, but I have to mention a bass trap that's only 8 inches square will not do very much.

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post #47 of 48 Old 07-09-2013, 02:21 PM
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Hi Ethan, I know, but the space is really little and bass traps in the corners are several things on their way, I think I will buy 12" bass traps to fill the higher corners and use the 8" for floor-ceiling and wall-ceiling intermediate junctures.

Now I got the dipoles I think I will try some diffusion. I'll try to improve my bass traps later while arranging everything.

Thanks Ethan, and everyone on the forum, you were really kind and helpful.

David
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post #48 of 48 Old 07-12-2013, 07:26 AM
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Hi again everyone, as I recently bought 4 Surround Polk Audio Dipole/Bipole Fxi's I was searching here and there about the differences in room treatment with this type of speakers and I found this in another forum:

Quote:
Diffusion should take place AFTER it has left the sound source be it Singer, Orchestra or Speaker, not emulated at source.

I have the side surrounds as dipole 90 degrees from the sweet spot, as Chris from Audyssey recommends and backs in bipolar as Polk Audio recommends.

That comment in the other forum was about placing diffusion panels right next to dipole mode speakers, I suppose placing some diffusion next to bipolar would be ok, but not on dipolar because they try to emulate already a diffused sound, and if we apply diffusion to a diffused sound maybe that won't sound right.

I'll appreciate your opinions.

Thanks everyone.

David
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