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Author Topic: aiming speakers
Marco Giustini
Film God

Posts: 2539
From: Reading, UK
Registered: Nov 2007


 - posted 06-24-2012 12:23 PM      Profile for Marco Giustini   Email Marco Giustini   Send New Private Message       Edit/Delete Post 
Hello,
How do you usually aim stage speakers, LF and HF? QSC manuals say to aim the HF horns to point to the center seat of the back row - using the very useful holes on the horn - but JBL say 2/3 of the room.
What is your choice when installing/tweaking a sound system?

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Monte L Fullmer
Film God

Posts: 8301
From: Nampa, Idaho, USA
Registered: Nov 2004


 - posted 06-24-2012 07:53 PM      Profile for Monte L Fullmer   Email Monte L Fullmer   Send New Private Message       Edit/Delete Post 
2/3rds have usually been the standard for HF horn alignment for uniform coverage.

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Manny Knowles
"What are these things and WHY are they BLUE???"

Posts: 4247
From: Bloomington, IN, USA
Registered: Feb 2002


 - posted 06-24-2012 08:04 PM      Profile for Manny Knowles   Email Manny Knowles   Send New Private Message       Edit/Delete Post 
Before going with the default way that it has "always been done" I'd want to know a little more about the difference(s) between the horn used by JBL vs QSC.

QSC may have good reasons for suggesting the back row. Then again, they may not. But how do we know if we don't dig deeper?

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Louis Bornwasser
Film God

Posts: 4427
From: prospect ky usa
Registered: Mar 2005


 - posted 06-25-2012 07:59 AM      Profile for Louis Bornwasser   Author's Homepage   Email Louis Bornwasser   Send New Private Message       Edit/Delete Post 
Certainly the vertical coverage of the horn is the main issue. If the back wall is "live" I have had to aim the horn to minimize echo. (Easier to do than you think: real time mike just above ear level on last row, analyzer at speaker; adjust for good sound, not great sound.)

It can look like you are aimed at the front row! Louis

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Don Sneed
Master Film Handler

Posts: 451
From: Texas City, TX, USA
Registered: Aug 2001


 - posted 06-25-2012 06:33 PM      Profile for Don Sneed   Author's Homepage   Email Don Sneed   Send New Private Message       Edit/Delete Post 
I aim the speakers using a SPL meter to get the lowest DB front to rear...The rear wall or 2/3 or a starting point for me, I fine tune using a SPL meter... if a large stadium seating auditorium, if need be on stadium seating I aim the array or speakers for the stadium seating & add front fill speakers under the speaker platform for the seats in the front of the screen, this allows the main screen speakers to be focus on the stadium seating area & allow the front fill speakers to be focus on the front of the screen seating area....I always get a (.5 to 1.5 db) by using a SPL meter...using this method all seat will hear evenly... with the front fill speaker a couple of amps is needed & outboard equalizers for the fills...for a large aud. this is the system to use...I am surprise more theater are not using doing this...

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Sam D. Chavez
Film God

Posts: 2081
From: Martinez, CA USA
Registered: Aug 2003


 - posted 06-25-2012 06:47 PM      Profile for Sam D. Chavez   Author's Homepage     Send New Private Message       Edit/Delete Post 
Say What? You are using low main speakers to fill in the seats below the stadium?

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Robert Koch
Film Handler

Posts: 93
From: Williams Ca USA
Registered: Apr 2006


 - posted 06-25-2012 07:49 PM      Profile for Robert Koch   Email Robert Koch   Send New Private Message       Edit/Delete Post 
Pay attention to Sam

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Samuel Hynds
Film Handler

Posts: 50
From: Riverside, CA, USA
Registered: Aug 2004


 - posted 06-26-2012 01:09 PM      Profile for Samuel Hynds   Email Samuel Hynds   Send New Private Message       Edit/Delete Post 
just FYI - Our HF horn has a ten degree down angle built into the horn and our MF horn has an eight degree down angle. which is why QSC recommends aiming at the rear of the seating area. (but not with the SC-2150) All other loudspeaker manufactures dont have this down angle - so aiming for them would be around 2/3 of the seating area.

but its always a good idea to run pink noise and walk the room, up and down and left to right - to get the most even spl thru out the seating are.

Sam Hynds
Product Specialist, Cinema
QSC Audio Products, LLC

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Louis Bornwasser
Film God

Posts: 4427
From: prospect ky usa
Registered: Mar 2005


 - posted 06-26-2012 03:39 PM      Profile for Louis Bornwasser   Author's Homepage   Email Louis Bornwasser   Send New Private Message       Edit/Delete Post 
Sam: we love ya.'

However, years ago JBL came out with a computer program that attempted to level out the sound field in a cinema.

I did a lot of random testing to determine why people sit where they do (if given a choice.) This was related to excessive screen size.

Sound issues were brought up by nearly half of the public.

Sometimes people sit where they do to allow a primitive form of volume control.

Note that women of all ages prefer distant seats because of sound. They are unusually unhappy with anything that is shrill or distorted. (Dull is OK.)

I ended up NOT supporting the JBL "constant volume" deal since it meant that a large group of people had lost control. Louis

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Tony Bandiera Jr
Film God

Posts: 2948
From: Moreland Idaho
Registered: Apr 2004


 - posted 06-26-2012 07:33 PM      Profile for Tony Bandiera Jr   Email Tony Bandiera Jr   Send New Private Message       Edit/Delete Post 
Sam H.: Thanks for popping in and clarifying why QSC directs the aiming the way they do.

As you know I used the QSC line at UCI for my new screening room..and they still rave about how great they sound. [Smile]

Oh, did you guys ever get the software changes to the DCM10/30 made as we discussed? PM me please.

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Marco Giustini
Film God

Posts: 2539
From: Reading, UK
Registered: Nov 2007


 - posted 06-27-2012 02:25 PM      Profile for Marco Giustini   Email Marco Giustini   Send New Private Message       Edit/Delete Post 
Hi Sam,

Then I did the right thing, I was aiming the 2150 and I eventually chose 2/3 of the auditorium. In fact, I checked the manuals to see whether there was a note about a prebuilt down angle.
I do agree with the walking procedure though, it's possibly the quickest way. I usually find HF aimed to the back row (sometimes the projection porthole!) and I have always wondered whether there was a real reason for that, besides laziness.

When I installed the 2150 I did a quick test from behind the screen, and found that actually aiming the horn towards the last row was causing my mike to read a little more HF content. But I like Sam's advice of walking around and judging the HF content by ear, I reckon is more accurate.

And yes, my appreciation too. Were my first QSC's, and despite the basic range and the very small auditorium they sounded really great. Was particularly impressed by the subwoofer, I've rarely heard such a deep, clean and undistorted sound, even at high levels. Looking forward to being able to setup a proper auditorium with a proper QSC array.

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System Notices
Forum Watchdog / Soup Nazi

Posts: 215

Registered: Apr 2004


 - posted 01-09-2018 07:42 AM      Profile for System Notices         Edit/Delete Post 

It has been 2021 days since the last post.


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Brian Vetter
Film Handler

Posts: 1
From: Raleigh, NC, usa
Registered: Nov 2016


 - posted 01-09-2018 07:42 AM      Profile for Brian Vetter   Email Brian Vetter   Send New Private Message       Edit/Delete Post 
I found this on the QSC Cinema web site:

QSC Cinema Tech Tip - 'No Tilt Required'

quote:
The mid-high frequency section of most 3- and 4-way QSC screen channel loudspeakers has a pre-set downward tilt. When it is properly elevated to approximately 5/8 image height behind the screen and aimed to the last row in a typical stadium-style cinema, there is no need for additional downward tilt. This allows you to minimize the distance from the horn to the screen, and keep it flush within a baffle wall.
 -

--
Brian

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Mark Gulbrandsen
Resident Trollmaster

Posts: 16151
From: Bountiful, Utah
Registered: Jun 99


 - posted 01-09-2018 11:09 AM      Profile for Mark Gulbrandsen   Email Mark Gulbrandsen   Send New Private Message       Edit/Delete Post 
I always did what QSC said to do, even with JBL (4675's typically) because that's also close to what THX specified. THX specified 2 feet above the center rear seat in all the THX houses I did. I usually use a pen laser to do aim them.

Mark

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Terry Monohan
Master Film Handler

Posts: 282
From: San Francisco CA USA
Registered: May 2014


 - posted 01-09-2018 09:18 PM      Profile for Terry Monohan   Email Terry Monohan   Send New Private Message       Edit/Delete Post 
One of the worst things for me in the many movie theatres I have gone into all my life is the placement of the stage speakers for stereo sound. Many cinemas even with large wide screens have the 3 L R C speakers all in a group in the middle behind the screen so you don't hear the full width of the stereo sound. While most do a good job of going to the end of the screen or masking many older small screen theatres still have the group of 3 speakers next to one another when the have room to extend to the ends. Who knows what the pitch of the speakers are to the audience in these problem cinemas.

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