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View Full Version : ďIn & OutĒ REW Frequency sweep



JBL 4645
02-16-2009, 12:50 PM
http://i279.photobucket.com/albums/kk123/IndianaJones34/InoutEQtesting.jpg

Hereís something I suggested a few days go about room EQ.

ďIn the cinema EQ is done in the projection booth this is to keep any disturbance like someone moving around because it will affect the graph.

When, I worked as projectionist for Warner Bros back (1998) the sound engineer asked for my assistance to place the microphone a few feet forward and slightly to one side and then ďget outĒ!

Also it took 2 days for the guy to EQ each of the 12 screens with the Dolby CP500, now then

Since I rather close to the door and I donít know why I didnít do this early, even thou I remember my days at Warner Bros.

So the title of this thread came to me out of the closet LOL. Yeah thatís right the (Kevin Kine, In & Out 1997) and no, Iím not gay.:D

So Iíve been In & Out the room like a yoyo, testing it first with me in the room and then out of the room, out of sight while REW performs its frequency sweep.

The difference looks appears so tiny when glancing at it first time, but there are some small variables.



Centre channel while being inside the living room.
http://i279.photobucket.com/albums/kk123/IndianaJones34/InoutFrequencysweepIN1centre.jpg

Centre channel while being outside of the living room.
http://i279.photobucket.com/albums/kk123/IndianaJones34/InoutFrequencysweepOUT1centre.jpg

JBL 4645
02-16-2009, 02:16 PM
Ran the centre though a few more times depressed the LF slightly and added a slight EQ in at 1Khz on the DCX2496. The left and right at present are miles out and Iíll work on them later.

Test was done while being outside of the room and good thing too because the high frequency is loud on the outside and I was inside the room Iíll be waving my arms around because of the pain of the high frequency, bending me ears.:(

JBL 4645
02-16-2009, 02:48 PM
You’ll get a good workout with “In & Out” it feels good too. :D

Well its looking okay for now I’ll run a few more though then focus on the left and right and see how close I can get them with the centre, sigh this is going to take all-night and into the early morning hours.:blink:


Centre channel JBL control 5

JBL 4645
02-16-2009, 03:17 PM
As an experiment I switched THX ON just for the sake of it there is only minor difference in the graph since the last one, I added a filter at 180Hz a tiny decrees -2db. Iíve selected 1/3 smoothing for this one.

Allanvh5150
02-16-2009, 03:38 PM
I have to ask the question: Do you do your listening from inside the room or outside? :blink:

JBL 4645
02-16-2009, 04:09 PM
I have to ask the question: Do you do your listening from inside the room or outside? :blink:

I let the frequency sweep run while being outside of the room otherwise my body will interfere with the frequencies, especially the high frequencies, the slightest moment and it wonders off up and down.

Play a sine wave high frequency stand still look at the SPL db, then move youíre arm or move youíre body around and the tone will make the needle on the SPL db go up and down.

JBL 4645
02-16-2009, 04:11 PM
I was wondering out that dip around 1Khz range?:banghead::D Iíve inverted the phase on it to rise it up. Well its not looking to bad except below 170Hz I think its in a bit ďnullĒ ether I move the sofa forwards and test it or move it back and test or I look for an alternative.:hmm: Sigh, its all good stuff.

Iíve been at this now for hours, and thatís just the centre and with limited EQ on the DCX2496 at hand because the crossover filters is taking up most of the free space percentage running close to 1%. Need those DEQ to handle this more efficiently.

JBL 4645
02-16-2009, 05:54 PM
So far this is how the right channel looks, yes a lot to do. [Sigh]

Iíve only applied a few filters with slim Q adjustments once the whole thing looks good enough over LCR Iíll post the filters used not that its going to useful for anyone, well maybe who knows? I know this much if and when I start on the false wall it will all be undone and Iíd have to start all over again. [Sigh]

JBL 4645
02-16-2009, 06:31 PM
So far the right channel is starting to slowly shape up but looks as if its going to take longer than the centre, I need to get it trimmed just a tiny little bit and get the level even for centre and right.

This must be past 7 hours now and its starting to get to me and its coming up to 2:30am. Iím going to have a few cat naps 20 minutes, to meditate on this I will.

JBL 4645
02-16-2009, 08:05 PM
Update on the left channel, its going slow here slow “in and out” the room like a yoyo.

4am in the morning sigh!:blink::D

JBL 4645
02-16-2009, 10:51 PM
This is what Iíve managed so far with the right front Iíll go over the LCR later tonight as the traffic level outside will start to registering on REW due to the sensuality of the ECM8000.

Besides I use the flipping break now Iím shattered!

Next is the surrounds left and right sidewall arrays and centre back. Sigh

Allanvh5150
02-16-2009, 11:51 PM
What I was meaning was that I dont listen to my system from another room so why would I EQ it from another room? :)

Allan.

JBL 4645
02-17-2009, 12:22 AM
You can have frequency analyzer in the room to run the sweeps just don’t get in the way of it while its running, otherwise it will get disturbed.

Once it’s done just look at what mess you have and apply EQ filters. Run the sweep again to see how it looks if more needs to be done, make it so.

I’m running the pink noise generator on the AVR to see what else needs to be addressed. A few tiny other adjustments I’m attending to at the moment as the tone on LCR in the LF range is slightly off so a few more hours, maybe another day?

HF LCR isn’t too bad when listening to the pink noise cycling from LCR.

EQ in the cinema is done in the booth, so if everything is pc adaptable with some of today’s digital EQ multi-bands link it up to the pc and do outside of the room.

I need lead to link up with the computer and the DCX2496 then I could move the pc out into the hallway and perform the tests outside of the room.

You realize I haven’t slept since yesterday.:snore: 13 hours

Allanvh5150
02-17-2009, 12:26 AM
Do you realise that it is nearly tomorrow here?:D

JBL 4645
02-17-2009, 01:10 AM
Do you realise that it is nearly tomorrow here?:D

:)LOL, no I wasnít aware of that fact.

JBL 4645
02-17-2009, 12:37 PM
Iíve had to ďreinvent the wheelĒ when I played the pink noise from the AVR the tones wasnít transparent. It should have been (left-hiss centre-hiss right-hiss) instead it was left-HiSS centre-hiss right-HiSS.:banghead:

Anyway Iím going over it again from a totally different angle of approach.:)

13 hours sigh.:(

boputnam
02-17-2009, 04:23 PM
I’ve had to “reinvent the wheel” when I played the pink noise from the AVR the tones wasn’t transparent. It should have been (left-hiss centre-hiss right-hiss) instead it was left-HiSS centre-hiss right-HiSS.:banghead:Ashley, that is one of the first things I always do when initializing (or inheriting... :( ) a system. Run Pink Noise and then quickly solo the outputs one-by-one:

HF L then R
MF L then R
LF L then R
Sub L then R

Almost always, there are surprises. :bouncy: Sometimes it's the interconnects, sometimes the speaker connections and sometimes the routings in the DSP. All sorta fun...

JBL 4645
02-17-2009, 07:55 PM
Ashley, that is one of the first things I always do when initializing (or inheriting... :( ) a system. Run Pink Noise and then quickly solo the outputs one-by-one:

HF L then R
MF L then R
LF L then R
Sub L then R

Almost always, there are surprises. :bouncy: Sometimes it's the interconnects, sometimes the speaker connections and sometimes the routings in the DSP. All sorta fun...

I have something else in mind run a sweep directly from channel to channel and pass it straight though the pc rather than airborne sound waves see how it looks from side to side. If one side should be different then Iíll know what to fix.

bop

Donít you have textbook version of your own a set of guidelines, that says this is how to address and tackle the issue?

jblbgw_man
02-20-2009, 11:33 PM
Can I ask what RTA/software you are using for these measurements. :bouncy:

JBL 4645
02-21-2009, 07:52 PM
Can I ask what RTA/software you are using for these measurements. :bouncy:


http://i279.photobucket.com/albums/kk123/IndianaJones34/InoutEQtesting.jpg

REW its software that was developed I think by the Home Theatre Shack.
http://www.hometheatershack.com/forums/

The In & Out thing came to me :D when realizing I should be outside the room otherwise the microphone can pick up breathing or other sounds? Oh, bugger I just realized it might be picking-up the fan noise on the pc, but the graph. Well maybe?