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Discussion Starter · #1 ·
I just invested in an SPL meter for HT setup. I have a couple of questions........


1. I have a Denon 3803, and the manual states to set up at 75db, C weighted slow scale........no problem, but the manual says from listening position. That is where I wonder if I would be better in the center of the room. My room layout forces my surround to be wall mounted, pointed down at listening position, center atop my TV about 15 feet away, sub is off to the left side wall, about 2 feet in front of listening position, and mains about 15 away. I considered that I might get a better result mounting the meter on a tripod in the center of the room as this would put it almost equal distance from all speakers.


2. What causes one of my main speakers to play about 3db below the other when using test tones?? The louder of the two is in a corner, between the wall and RPTV, and the other is pretty much in the open.........I thought this might be the reason, but I am not sure.
 

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The SPL at the listening position will be different than in the center of the room.

If you balance the system in the center of the room, it will be unbalanced at the listening position.

Room modes (standing waves) and reflections are the culprit.


1. place the meter at ear level at the listening position.


2. One speaker is close to a corner while the other is near the middle of the room.

These locations are about as dissimilar as they could be.

It's no wonder that one speaker is receiving more room reinforcement than the other.

Ideally, the LR speakers should loaded into the same acoustical "space" or their tonal balance will not match in the bass and lower midrange.


3. the average subwoofer level on the RS meter will be off by about 2db, so set it to read 77db if the other speakers are at 75db.

(the RS meter mic roll-off produces low readings below 50hz with the C/slow setting)

Correction tables are available for this meter if you want to calibrate the subwoofer precisely using warble tones.
 

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As Snicker says, you want to calibrate your set up to where you sit, because that is where you will be listening to it. First, and you likely have, but didn't mention, you want to set up the distances of each speaker into your reciever. This will give them the proper delay. Then you adjust the levels using the SPL meter. Doesn't really matter if one speaker gets set a few DB higher than the other, that's the whole point of calibrating them.


As far as placement goes, do a search for dolby or THX standards for speaker placement. Ideally, for movies anyway, you do not want to point your surrounds down to the listening position. They are supposed to be ambiance sounds, and you should not be able to pinpoint the source. This makes the surround effect a little more believable. For sub placement, I set mine up with a lot of trial and error and a piece of software called RoomEQ Wizard. Some people can calculate the ideal position from room dimensions. I haven't really looked into this yet, but shouldn't be too hard. Easiest seems to be to temporarily put the sub in the listening position, then walk around the room with your SPL meter, and while playing the pink tones through the subwoofer, set your meter to c-weighted fast response, and find the place where the needle jumps around the least (ie the flattest response). Remember that your sub will likely be on the floor, so you want to hold the SPL meter close to the same level. More than likely, you will find that your sub placement will be close to the corner with the longest adjoining walls, but not always. This will give you the quick and dirty setup, there are lots of tools, and lots of software that will help you pinpoint it, but this method should get you pretty close.


Remember that if you move your listening position or adjust your speaker positions, you will have to set up the distances, and calibrate again.
 

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If you're thinking that you want calibration that applies to *all* seats in the house, sorry, but you can't. You can sample the levels at each seat and try for balance, but it will be a compromise at best. The "center of the room" approach won't do as well.


Where the seat-by-seat calibration will vary most is in the bass region. Standing waves in the room make the frequency response curve in the bass region vary by moving as little as 6". With more sophisticated gear (basically a PC) added to your SPL meter you will be able to plot the curves and get a much more accurate look at what's going on than simply the SPL. But the net result will be the balancing act. There's still a good deal of art to this acoustics business.
 

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Discussion Starter · #5 ·
Thanks for the replies so far............I have learned a few things, and has some ideas re-enforced.


As far as surround placement, I am forced into the postion they are......long room, couch (main position) is against the back wall.......entry door to the right in the corner, and couch almost against the other corner. The door way keeps speakers from being ear level, and a window behind the couch keeps them from being mounted behind the couch.......so they are the best they can be.
 

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You need to move your couch forward past the door. It will not only sound better, it will actually make the room appear larger.


You can always mount rear speakers against the ceiling.
 

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Ive found that placing my surround speakers on the floor and aiming them upward and toward the wall, the surround effect is better, with virtually no localization problems.


I agree with the recommendation that the primary listening position will work better away from the wall.

Experiment.

My room is set up on a diagonal, which places the speakers and listener about a third of the way into the room.

bass is smooth but still very extended, and sidewall reflections are minimized, since the walls actually splay outward away from the listener.
http://www.byrographics.com/media/room-setup.jpg
 

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Discussion Starter · #8 ·
Quote:
Originally Posted by DMF
You need to move your couch forward past the door. It will not only sound better, it will actually make the room appear larger.


You can always mount rear speakers against the ceiling.
Due to issues with another couch (love seat) and a wall furnace, moving forward is impratical if not impossible.


How would the speakers be mounted against the ceiling?? ie......flush mounted with back to the ceiling facing down?? Right now the are turned 90 degrees, mounted with brackets fastened to the back of the speaker angled down about 60 degrees. I can not mount the up and down, due to the height of the speaker compared the the amount of clearance between entry door and ceiling.
 

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Without the couch moved forward, I wouldn't even try to do rear channels.



Love the Bladerunner quote.
 

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Quote:
Originally Posted by DMF
Without the couch moved forward, I wouldn't even try to do rear channels.



Love the Bladerunner quote.
so it wont be optimal, no big deal...those that dont have a dedicated room are always forced to make compromises...


as far as the couch against the wall and the surrounds...you have several options.


1. fire the rear channels up from the back of the couch ... preferably from behind and below.


2. get a pair of bi or di poles. this will help disperse the rear channels...perfect? no, but certainly better than nothing.


check here for more ideas, specifically Figure 11:
http://www.4seating.com/audio_DolbyReference.htm
 

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All pictures in that section show the couch pulled away from the wall. need4speed, do you think you might have missed part of this conversation? ;)


No, I don't think "anything" is better than nothing. The rears exist to provide spatial clues. Other than that, they contain no discrete information. If you can't put them behind you then you can't get the clues. So why bother?
 

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Quote:
Originally Posted by DMF
All pictures in that section show the couch pulled away from the wall. need4speed, do you think you might have missed part of this conversation? ;)


No, I don't think "anything" is better than nothing. The rears exist to provide spatial clues. Other than that, they contain no discrete information. If you can't put them behind you then you can't get the clues. So why bother?
instead of looking everything in black and white, take the pictures as a guideline for possible alternate speaker placements...some ideas to experiment with. At my old town house, i had the couch against the back wall with the rears firing up, and it sounded fine. there is nothing cast in stone that says someone has to do it 'this way'. if the OP finds a placement that sounds good to him, then thats all that matters...IMHO.


also, the rears don't always have to be behind...you can reflect them off the sidewalls to give the illusion that the sound is coming from the rear...
 

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Don't get me wrong, need, I agree with you and the diagrams. But you (and they) just reinforce what I said. He *must* get the couch away from the wall to use rear channels. Just a foot or two will help.


If he can't move the couch off the wall, then there's no room for the many setup options, and no reason to spend time and $$ on the rears.
 

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Quote:
Originally Posted by DMF
Don't get me wrong, need, I agree with you and the diagrams. But you (and they) just reinforce what I said. He *must* get the couch away from the wall to use rear channels. Just a foot or two will help.


If he can't move the couch off the wall, then there's no room for the many setup options, and no reason to spend time and $$ on the rears.
we agree to agreee :)


ive also had success mounting them on the side walls pointing towards each other or slightly back and reflecting off the back wall, but they will need to be about 2-3ft above the ears.


and i agree with you..even just a foot would help, but if he cant do it, then he will just have to play around with reflecting the sound and adjusting the levels accordingly
 

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3. the average subwoofer level on the RS meter will be off by about 2db, so set it to read 77db if the other speakers are at 75db.

(the RS meter mic roll-off produces low readings below 50hz with the C/slow setting)

Correction tables are available for this meter if you want to calibrate the subwoofer precisely using warble tones.[/quote]

I'm sorry but I am confused abot this.I've previously read just the opposite about the RS meter on this forum.I was hoping someone would please clear this for me.
 

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You are right; snicklefritz is wrong. It reads too low, not too high (and I assume a 3 dB difference).

To set the sub for 75 dB, adjust it to 72 dB on the meter.



Good catch! I missed it entirely.
 
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