# New here, did read a lot, now what???



## Guest (Feb 21, 2007)

Hi guys
First, I want to express how this place is great for newbies!!

I did read a lot on HT and accoustic, here and on the web. I'm now ready to go into the audio treatment part of my home theater... 

After other different subjects projects, I now now the value of these kind of forums on the internet, where experts (both by formation and/or experience) can help avoid mistake.

So i started a tread about my room treatment so I can get help throught the processe. (By the way, I hope my english won't be too bad, as this is not my first one...)

So, here is my room:

11 feets wide
16 feets deapth
7 feet high
The front wall is 3 inches shorter then the back wall, symetrically, so like a V shape. (Was suggested in the construction process, hope it's ok)

This room is mine, so no wife factor limitation :daydream: 
Step #1
I know the first step is probably measure, measure, measure.
I know the basics of using my digital Radioschack SPL meter, but what do i do with the results?
What program, what graph to post, etc.

Thank's for your time guys:jiggy:


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## Sonnie (Apr 11, 2006)

Hi Christian and welcome to the Shack!

I would start out by reading up on REW (Room EQ Wizard) and its HELP file... and then check out some of the sticky threads in the BFD | REW Forum ... :T


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## bpape (Sep 14, 2006)

Welcome.

I agree with the REQ thing. Great tool. Realistically, there are things that every room needs. The REQ will help with the details. Get some good broadband absorbtion in the corners, hit the first reflection points (probably 2" in your room size) and hit the front wall totally. After that, it's a matter of balancing out the overall decay time scheme.

Bryan


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## Guest (Feb 21, 2007)

Thank's for the quick reply.

Just want to be sure: Would you recommend doing the basic treatment before mesurements or after?

Thank's
chris


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## bpape (Sep 14, 2006)

I personally like to measure the room with just speakers and furniture in it. Makes tweaking sub and speaker positions a lot easier. Once you do that, then you can do the basic treatments and see what you still have left to address.

Bryan


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## Guest (Feb 22, 2007)

Ok guys, REW is calibrated.
I did my fisrt room test:

http://www.hometheatershack.com/for...t-measurement-graph-what-wrong.html#post27084

I did post in the REW forum, but I was wondering what you think about the graph, something wrong is in't it??
Chris


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## Guest (Feb 22, 2007)

Ok, i made the correction to the software.
Here is my first reading graph:









Thank's for your support
Chris


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## bpape (Sep 14, 2006)

Yup. That looks 'better' or at least more typical. Play with the sub location and seating location to minimize the nulls as much as possible. 

Bryan


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## Sonnie (Apr 11, 2006)

I don't mean to plaster you with tons of questions, but it may help in instructing you better.

Can you show us a diagram of your room and maybe some pics? 

Is it completely sealed or does it open up to other areas?

Where is the sub located and where is the main listening position?

What is the sub you are using?


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## Guest (Feb 23, 2007)

No problems with questions!! , i think it show that your advices are custom fit, not a one size fit a ll 

I really enjoy this new field of hobby. The more i read about it, the more i understand that the money spent on equipment is not that important...

Answers:

The room is 11 X 16 X 7. One small room is 3 inch shorter than the other small wall, so the shape is like /--\ but not noticeable to the eye. It was a recommandation when i built the room... At that time, i did not knew HT shack :huh: I think the idea was to avoid standing wave...

My listening position (2 place couch) was place 38% from back wall, as recommended on forum, and i placed the sub in front. Last night, i moved it forward, and it reduced the crash seen at 150HZ and some other.

Commercial carpet floor, sealed door, gypsum wall.

But everything can be move, i have enough connection everywhere, and no wife factor. She is simply not intersted in that:hush: 

Thank's again for your support to help me start the tuning

Chris

p.s.

Once the sub is ok, i assume i do the same with the main and surrond?


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## bpape (Sep 14, 2006)

OK. I'd go back and start at 38% again just as a baseline. Do the sub first. Take sweeps at various positions to get the smoothest response to say 120hz even though you'll cross at 80. Start out with the sub at say 2/5 of the room width, a foot from the front wall (and don't forget you can move the sub vertically too...) and see what that does.

Another option is to leave the sub in it's current position in the vertical and front to back plane and just move it side to side to see what changes. After noting these, go back to the same side to side position and move it away from the front wall and note what changes. Based on these things, you'll get a better feel for where the best sub position will be.

Now the mains... Distance to the front and side wall are critical and can drastically change the frequency response. This is due to boundary interference (SBIR) from direct radiated and early reflected sound from the spherical wavefront that woofers generate. My strong suspicion is that some of the nulls are from 2 things:

- Lack of absorbtion behind a speaker too close to the front wall
- Reflection off the back wall and cancellation at your listening position (this has nothing to do with standard room modes though - it's purely a function of distance from speakers to head and head to rear wall.)

If you see a null or peak move when you move the speakers purely forward and back, then note the frequency and try some absorbtion capable of dealing with that frequency directly behind the speaker on the wall. This will absorb some of the reflected wave and cause the resulting interference to be lessened. The same can be done on the rear wall.

As you go through this, do not move the mic at all. Steady consistent mic position is key to getting accurate results. When you make movements of the subs and mains, do the bulk moves first, then start whittling down to a few inches or even an inch at a time. You'll be amazed at the differences you can get. For the sub, shoot for the fewest nulls - peaks can be dealt with via EQ on the sub more easily. Having 2 seats also makes this a much easier task than trying to balance out 8-12 seats for best overall performance.

We're having fun now! :jiggy:


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## Guest (Feb 23, 2007)

Thank's Bryan, I'm starting to see the light 

One basic question; Do I always sweep from 15 to 200HZ for sub and main/surrond? Or i first take care or the 15-200 range and after i go full range?

Also, was is acceptable and not considerated as a peak or a null? + - 5 Db ok?
Thank's
Chris


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## Sonnie (Apr 11, 2006)

I think knowing what your equipment is might help us some. If you main speakers can handle it, you might try a lower crossover point, which could help with the 85Hz hole. Knowing what kind of sub you own helps us determine what kind of extension you should be looking for... so equipment does matter.

What kind of sub do you own?

What are your main speakers?


I would start with the sub and get it as smooth as possible and then move to full range, which means you want to focus on the crashes at 50Hz and 85hz for now. Measure your sub only to start with.


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## terry j (Jul 31, 2006)

Geez Brian

thanks very much for the well detailed answer above, the time that both you and Ethan take in these forums are, I'm sure, very much appreciated by many more than just myself!!


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## Guest (Feb 24, 2007)

Sonnie, here is my equipment

DENON AVR 5 X 105 watts (and a ARCAM 7 X 150 W FMJ waiting to work)

B&W 602 speakers for main
CC6 B& w for surrond
B&W HTM1 for center
Sub B&W ASW 500 or 600, don't remember :R 

I don't think I can change the crossover point on the AVR 
Chris


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## Sonnie (Apr 11, 2006)

Okay... yeah... well those subs roll off at about 25Hz if I remember correctly, so the response extension we see is probably all we will see.

I would think the Arcam would allow crossover adjustment... and most Denons do unless it's an older model.


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## bpape (Sep 14, 2006)

I would recommend the xover be set at 80Hz for this exercise. It's the best compromise between letting the sub do as much as possible, keeping the bottom end away from the mains which are rarely placed for bass response, and having the xover too high where the sub starts becoming localizable (and much harder to set phase correctly when the sub range gets wider.

When running the mains test, run them full range and sweep 20-200 or 20-300. We want to see what it's doing below the xover point since there will still be input. Another reason for this is the following scenario:

What if.... I have smooth response down to say 60 Hz from the mains and up to 100 Hz from the sub. BUT, when I run both of them with the xover, I get a dip somewhere in that 60-100Hz range? What does that tell me? Beuller? Beuller?


Bryan


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## Guest (Mar 5, 2007)

Ok guys!

After a lot of testing the sub, here is the best graph I get.

I understand that 26 to 47 Hz is a problem...

Would you agree to + or - 5 db to every frequency is ok for the sub?

All suggestion welcome!

Thank's for your time
Chris


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## bpape (Sep 14, 2006)

+/- 5 is a good realistic target to shoot for. 

Do you have any other plots from other locations?

Bryan


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## Guest (Mar 5, 2007)

Sorry Brian, don't understand the question?? I speak french first, but did try to understand the meaning with translation, but ?? Could you reformulate?:R


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## Guest (Mar 5, 2007)

In case you meant another graph, here it is, the one with fewest nulls.


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## Guest (Mar 5, 2007)

Another graph, full range. 
Is the scale ok to read and help?

Looks pretty bad after 10000 Hz :sad: 
I use radio shack SPL meter, maybe it's the reason


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## Guest (Mar 5, 2007)

oops, here is the graph


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## bpape (Sep 14, 2006)

The 0-300 is fine. I'm thinking the 2nd one is more where I'd start. Now the question is how much of the peak you're getting is related to seating position. Try setting the sub the same way but move the mic back maybe a foot and see what happens. Where is your seating position?

The next question is what did you do to the sub position that got rid of the 50Hz null but caused the large wide peak lower?

Bryan


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## Guest (Mar 5, 2007)

Recording 1 foot closer to the sub give a lower paek at 35, but create another one at 75, about the same strengh +7 DB

Recoding 1 foot wider away, make the peak higher

Quick question, when full range, I understand that some frequency will get peak because of reflexion, but why is there nulls too?? frequency cancellation??

Thank's


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