Poll: How do YOU set your gain structure???? - Page 3 - AVS Forum
View Poll Results: Do you max your SUB amp's gain out to start or make it your last adjustment in gain structure?
I max my amp's gain then go from there 5 17.24%
I start at the AVR and go down the chain 13 44.83%
I haven't done proper gain structuring on my system yet 10 34.48%
I don't know what gain structure means 1 3.45%
Voters: 29. You may not vote on this poll

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post #61 of 90 Old 02-20-2013, 07:25 AM
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Quote:
Originally Posted by whoaru99 View Post

Yeah, it almost sounds like a little confusion between gain structure vs. trying to use (get?) all the power an amp can produce. They aren't inherently the same thing.

my understanding is that the goal is to maximize dynamic range. And if the amp cannot be driven into clipping at AVR calibrated "reference" level than the dynamic range is truncated by definition. Does it sound about right?
Granted one can allow some padding for headroom if power is plentiful. But I suspect most of us do not have more than 3dB or 1/2 of the max power to spare.
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post #62 of 90 Old 02-20-2013, 07:45 AM
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Bass Addict,

Just wondering here, if once you have finished setting the gain structure in the system, are you than going back and setting the individual speaker and sub levels with the internal test tone of receiver-processor? I just cannot see how you are getting such a difference in between the speakers and sub(s) once you have set up the gain.

James
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post #63 of 90 Old 02-20-2013, 07:46 AM
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Quote:
Originally Posted by zheka View Post

Quote:
Originally Posted by NicksHitachi View Post

As far as over riding Audyssey goes, i always set gain structure after Audyssey has done its thing. Youll want all EQ in place for that task IMO anyways.
but is not it a chicken or the eggs situation? if you adjust gain down the chain after Audyssey calibration, would not it invalidate the level matching done by Audyssey in the first place? That's where my question in post #29 comes from.
.


I don't use Audyssey's level settings, especially for the sub channel.

And, Yes, I always set gain structure after Audyssey and outboard EQ is complete. I don't know how one would do it before proper, not knowing what boost filters may or may not be applied?
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post #64 of 90 Old 02-20-2013, 07:59 AM - Thread Starter
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Quote:
Originally Posted by NicksHitachi View Post

I don't use Audyssey's level settings, especially for the sub channel.

And, Yes, I always set gain structure after Audyssey and outboard EQ is complete. I don't know how one would do it before proper, not knowing what boost filters may or may not be applied?

Ive taken down some peaks before Audyssey before, and it helps in some cases smile.gif If Aud is giving you something really crazy or applying an insane amount filters, sometimes pre-eq is good, especially for mains smile.gif

BA, I am also interested in what your amp is doing during pod scene at ref. how far up the gain meter are you hitting? Assuming subs are flat or even 5dB hot.

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post #65 of 90 Old 02-20-2013, 07:59 AM
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Quote:
Originally Posted by NicksHitachi View Post

I don't use Audyssey's level settings, especially for the sub channel.

And, Yes, I always set gain structure after Audyssey and outboard EQ is complete. I don't know how one would do it before proper, not knowing what boost filters may or may not be applied?

yeah, setting gain structure after Audyssey makes perfect sense. How do you do the level matching? SPL meter?
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post #66 of 90 Old 02-20-2013, 08:09 AM
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Originally Posted by beastaudio View Post

Ive taken down some peaks before Audyssey before, and it helps in some cases smile.gif If Aud is giving you something really crazy or applying an insane amount filters, sometimes pre-eq is good, especially for mains smile.gif

Aint nothin wrong with that! I don't manually EQ my mains(yet) but I hope to when I grow up......... biggrin.gif

FWIW, Ive read both ways work: Audyssey first then manual EQ and manual EQ first then Audyssey. IDK which is the definitive best way, I just enjoy the control of the final say on FR.
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post #67 of 90 Old 02-20-2013, 08:10 AM
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Quote:
Originally Posted by zheka View Post

Quote:
Originally Posted by NicksHitachi View Post

I don't use Audyssey's level settings, especially for the sub channel.

And, Yes, I always set gain structure after Audyssey and outboard EQ is complete. I don't know how one would do it before proper, not knowing what boost filters may or may not be applied?

yeah, setting gain structure after Audyssey makes perfect sense. How do you do the level matching? SPL meter?

Sure, meter works.

I use REW though.....
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post #68 of 90 Old 02-20-2013, 09:36 AM
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Originally Posted by whoaru99 View Post

Bearing in mind that 20V appears to be 20Vpp, but formerly discussed was Vrms. 20Vpp = 7Vrms.

Well that certainly clears things up. I was thinking there was no way this thing was cranking out 20v. 7 sounds much more likely. Thank you. That being said, the Onkyo does not show clipping at full tilt.

So in my other post when showing gain structure, my SMS1 is clipping the output signal at 1.77 volts not 5. Now what I'm not sure of is if this is an absolute value, or a value correlating to boost over incoming voltage via the volume knob.

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Originally Posted by exojam View Post

Bass Addict,

Just wondering here, if once you have finished setting the gain structure in the system, are you than going back and setting the individual speaker and sub levels with the internal test tone of receiver-processor? I just cannot see how you are getting such a difference in between the speakers and sub(s) once you have set up the gain.

James

Once again, the way I understand it; gain structure and calibrated level are two totally separate things.

I setup the gains as I should. I didn't use full boost on Onkyo as it's not required. Onkyo level was set to 0, I then opened the ep4000 gains to wide open and turned up the volume on the SMS1. I know the SMS clips the output at 28, so as long as I'm below that level I'm fine. Clip lights came on at volume 26, so I backed it down to 24.

So initial gain settings before any eq'ing were Onkyo 0, SMS1 at 24, and EP4000 wide open. Here's where I have the issue:

Both Audessey and the SMS see some major differences when calibrating at this point. And it makes perfect sense. Setting up a gain structure is not the same as calibrating output. When I went to EQ my SMS curve, at my gain structure level, there was no way to match the main level and sub level. I had the volume so far down on the receiver the mains sweep wasn't even registering. I had to turn the sub level to around -10, and raise the volume, to get the sub level and speaker level at around the same 80db level. So I know according to the ECM mic that the sub level was crazy hot at an output of 0.

Audyssey also confirms the same thing. When calibrating speakers, they are set around -2, and the sub level is set at -12; and this is with the gains on the 4000 backed down to about a 1/4 and the SMS volume at 13. When I turn them up any further, the sub level can't take enough out. Now I haven't verified this against an SPL meter as it's loaned out to a friend, but I trust that my SMS mic is pretty accurate and it's showing the same thing.

So here's the nutshell. Assuming the SMS1 is boosting 1db per volume unit increase; I have a difference of 22 db's and 3/4 gain between gain structure setup and calibrated setup?????????????????????

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post #69 of 90 Old 02-20-2013, 10:50 AM
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"Once again, the way I understand it; gain structure and calibrated level are two totally separate things." They are seperate but I guess what I stated - was asking is I just cannot see how the speakers and subs are so far apart after doing your steps.

To set the gain I did the steps below. I used the files provided by Wayne over at HTS.

1) Trims for L-R and sub were set to +12db (highest they could go using an Onkyo 885) with Onkyo set to stereo

2) Speakers set to an 80HZ crossover (I measured them with a volt meter and received the same voltage with a 1KHZ 0dbfs signal with this crossover and at full range).

3) I increased the master volume until my signal went into clipping and then backed it down until it was out of clipping.

For the mains with the 1KHZ signal I was clean until 0db on the master volume.

For the sub signal I was clean until -2.5db on the master volume

I than (with speakers disconnected) played the 1KHZ signal at 0db on master volume and increased the gain until I barely lit the clip light. The mains use a QSC GX5.

I than played the 60HZ signal for the sub channel at -2.5db on the master volume and increased the gain until I barley lit up the clip light. The subs use a Marathon MA-5050.

I than played the internal test tone to set the trims to read 75db on my SPL meter.

I have attached some screen shots of the o’scope readings for both the 1KHZ and 60HZ signal with no clipping and clipping.
* If you want you can see the scope reading at the thread below
http://www.avsforum.com/t/1330718/how-to-set-gain-structure-properly/30


James
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post #70 of 90 Old 02-20-2013, 11:12 AM
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Quote:
Originally Posted by zheka View Post

And if the amp cannot be driven into clipping at AVR calibrated "reference" level than the dynamic range is truncated by definition. Does it sound about right?

Not really, in regard to where I think the confusion may lie. If, at calibrated reference level, only 250 watts are required to achieve ref level, you're not going to be driving a 1,000 watt amp to clipping.

More or less, the only time I'd think you'd expect to see amp clipping at calibrated reference level is if the amp has only enough (or not enough) power to drive reference level volume in your system. You can't just adjust your gains to make the amp clip at reference level if the power output at (verge of) amp clipping isn't necessary to achieve ref level.

Just because there is a knob doesn't mean you should turn it.
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post #71 of 90 Old 02-20-2013, 11:40 AM
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Quote:
Originally Posted by whoaru99 View Post

Quote:
And if the amp cannot be driven into clipping at AVR calibrated "reference" level than the dynamic range is truncated by definition. Does it sound about right?
Not really, in regard to where I think the confusion may lie. If, at calibrated reference level, only 250 watts are required to achieve ref level, you're not going to be driving a 1,000 watt amp to clipping.

More or less, the only time I'd think you'd expect to see amp clipping at calibrated reference level is if the amp has only enough (or not enough) power to drive reference level volume in your system. You can't just adjust your gains to make the amp clip at reference level if the power output at (verge of) amp clipping isn't necessary to achieve ref level.

Well, this does not work in my system. My sub is nowhere near required SPL with Audyssey calibrated ref sub signal level. And how could it be, if with that input signal and gain settings my amp can only produce around 150W into 4 ohm load?
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post #72 of 90 Old 02-20-2013, 11:42 AM - Thread Starter
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I think he means calibrated as, after you have gone back and readjusted your sub trim to 75dB

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post #73 of 90 Old 02-20-2013, 01:38 PM
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Quote:
Originally Posted by exojam View Post

"Once again, the way I understand it; gain structure and calibrated level are two totally separate things." They are seperate but I guess what I stated - was asking is I just cannot see how the speakers and subs are so far apart after doing your steps.

To set the gain I did the steps below. I used the files provided by Wayne over at HTS.

1) Trims for L-R and sub were set to +12db (highest they could go using an Onkyo 885)

2) Speakers set to an 80HZ crossover (I measured them with a volt meter and received the same voltage with a 1KHZ 0dbfs signal with this crossover and at full range).

3) I increased the master volume until my signal went into clipping and then backed it down until it was out of clipping.

For the mains with the 1KHZ signal I was clean until 0db on the master volume.

For the sub signal I was clean until -2.5db on the master volume

I than (with speakers disconnected) played the 1KHZ signal at 0db on master volume and increased the gain until I barely lit the clip light. The mains use a QSC GX5.

I than played the 60HZ signal for the sub channel at -2.5db on the master volume and increased the gain until I barley lit up the clip light. The subs use a Marathon MA-5050.

I than played the internal test tone to set the trims to read 75db on my SPL meter.

I have attached some screen shots of the o’scope readings for both the 1KHZ and 60HZ signal with no clipping and clipping.
* If you want you can see the scope reading at the thread below
http://www.avsforum.com/t/1330718/how-to-set-gain-structure-properly/30


James

Hi James,

Thank you for sharing and for the link. you obviously went through the troubles of setting up gain structure as proscribed by the pros. respect.

Can you check how far below clipping your subwoofer amp is during the WoW tripod scene at ref level? That is assuming you can tell what settings on MVC correspond to the ref level, which may be wrong assumption given that you did not use Audyssey for level matching.

thank you
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post #74 of 90 Old 02-20-2013, 03:26 PM
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Zheka,

I have to be honest and say I just do not have time on my plate to go through the process you requested. Sorry.

James
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post #75 of 90 Old 02-20-2013, 04:30 PM
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Quote:
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Zheka,

I have to be honest and say I just do not have time on my plate to go through the process you requested. Sorry.

James

Sure, I understand.
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post #76 of 90 Old 02-20-2013, 04:55 PM
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Quote:
Originally Posted by zheka View Post

Well, this does not work in my system. My sub is nowhere near required SPL with Audyssey calibrated ref sub signal level. And how could it be, if with that input signal and gain settings my amp can only produce around 150W into 4 ohm load?

I'm not clear what you're saying.

If you forget about trying to tweak the gain structure and just run an ordinary, every day straight up Audyssey cal, what are the resulting channel trims?

Just because there is a knob doesn't mean you should turn it.
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post #77 of 90 Old 02-20-2013, 05:21 PM
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Quote:
Originally Posted by whoaru99 View Post

I'm not clear what you're saying.

If you forget about trying to tweak the gain structure and just run an ordinary, every day straight up Audyssey cal, what are the resulting channel trims?

right, that's exactly what I did. I was prompted to lower the sub volume during the calibration. So I got the trim on the amp around 12 o'clock position to get it within the range Audyssey accepted. After the calibration my sub channel level was set at -7, surrounds - at -11.5 and the fronts are around -3.

I arrived at the 150W number based on the assumption that at 0dBFS my amp is supposed to do around 2kW bridged into 4ohm and the max output during the tripod scene was at -12dBFS which is roughly 1/15th of the max power or 133W
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post #78 of 90 Old 02-20-2013, 06:49 PM
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Where does 0 dBFS or -12 dBFS come from? What are these with reference to?

Just because there is a knob doesn't mean you should turn it.
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post #79 of 90 Old 02-20-2013, 07:03 PM
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Quote:
Originally Posted by whoaru99 View Post

Where does 0 dBFS or -12 dBFS come from? What are these with reference to?

0dBFS - max output before clipping lights on the amp meter turn on

-12dBFS observed on the the amp meter during the tripod scene. It was confirmed by the fact that I had to boost the signal by roughly this amount to get the amp into clipping territory. In fact it was slightly more than 12dB boost: 7db on AVR sub channel and 6db input gain on the amp.
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post #80 of 90 Old 02-20-2013, 07:29 PM
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I must be missing something...

If you ran Audyssey cal and made the necessary adjustments for the cal to successfully complete, then your amp is doing what it's supposed to be doing. You can't force the amp to put out 2kW / indicate 0dB on the meters and still keep the calibrated channel/system balance if it only takes 133W from that amp to do the work.

Just because there is a knob doesn't mean you should turn it.
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post #81 of 90 Old 02-21-2013, 06:43 AM - Thread Starter
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Quote:
Originally Posted by whoaru99 View Post

Where does 0 dBFS or -12 dBFS come from? What are these with reference to?

Think of 0dBFS as a FULL VOLUME signal. To explain, when the mixer is doing the soundtrack of a movie, he doesn't want to produce vocals that are the same volume as the loudest explosion in the movie right? If he were to use the full potential of a particular frequency to recreate that explosion, gunshot, car crash, etc. then he would use a 0dBFS signal, whereas vocals might average about -15 to -25dBFS or so.

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I must be missing something...

If you ran Audyssey cal and made the necessary adjustments for the cal to successfully complete, then your amp is doing what it's supposed to be doing. You can't force the amp to put out 2kW / indicate 0dB on the meters and still keep the calibrated channel/system balance if it only takes 133W from that amp to do the work.

Not necessarily.

A) Audyssey rarely gets a lot of sub systems calibrated right. And even if it does, the levels are off if you test with an RS meter after calibration.

B) IF Audyssey decides to apply a 6dB boost at some frequencies during calibration, then there you are, all of the sudden needing to use your full amp's potential if there are just two filters of that size...

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post #82 of 90 Old 02-21-2013, 06:49 AM
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Quote:
Originally Posted by whoaru99 View Post

I must be missing something...

If you ran Audyssey cal and made the necessary adjustments for the cal to successfully complete, then your amp is doing what it's supposed to be doing. You can't force the amp to put out 2kW / indicate 0dB on the meters and still keep the calibrated channel/system balance if it only takes 133W from that amp to do the work.

I do not know what to say. I understand your point that the amp should not necessarily be at full capacity for ref. level playback. And there are guys here with systems that have plenty of headroom that would support your point. But mine is not one of them, especially with this much power.
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post #83 of 90 Old 02-21-2013, 06:58 AM
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actually, maybe it can get close to ref level with 130W, depending on the frequency of the test signal. wow.
I'll post the sims later.
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post #84 of 90 Old 02-21-2013, 07:05 AM - Thread Starter
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I dunno, I would think my system would have more than enough headroom, with an fp14k and 8 18's, but just having that additional headroom makes me want to use it, so I typically do smile.gif I have each quad of drivers set to 75dB, summed they give me 85dB at the LP so 10dB's hot overall. In the pod scene and FOTP I don't clip, but the -4dB light on my amp comes on. If I were to run my system dead flat, obviously this would not be an issue...

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post #85 of 90 Old 02-21-2013, 07:49 AM
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CHT SS18.2 - dual 18" pro woofers, approx 90dB efficient each.

Without EQ the drivers begin to roll off relatively high but w/ 130w, predicted SPL is above 110dB from approx 40Hz and up.
Obviously the output would be lower at 10ft(my LP) but then the room may play role as well. perhaps there is a mode at LP that boosts the test tone.



do you guys know the frequency range used for the subwoofer PN test tones?


i guess the lesson is that I have much more room for the LF boost than I thought. e.g. I can get a curve like this with a few filters and still be well within power and excursion limits.







I may have to rethink power requirements for my upcoming setups.

whoaru99, thank you for making me look at this more closely.
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post #86 of 90 Old 02-21-2013, 08:36 AM
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Quote:
Originally Posted by beastaudio View Post

I dunno, I would think my system would have more than enough headroom, with an fp14k and 8 18's, but just having that additional headroom makes me want to use it, so I typically do smile.gif I have each quad of drivers set to 75dB, summed they give me 85dB at the LP so 10dB's hot overall. In the pod scene and FOTP I don't clip, but the -4dB light on my amp comes on. If I were to run my system dead flat, obviously this would not be an issue...

yeah, i still think the levels are off in my case but maybe not by as much as I thought, especially in the mid/upper bass.
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post #87 of 90 Old 02-21-2013, 09:24 AM
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A good house curve eats up headroom pretty quick...... Audyssey applies a pretty good bit of LF boost for me out of the box. Im using the MulteqXT variety.

Z,

it really sounds like to me, that your ready for a full measurement setup. Many of the questions your asking beg measurement to resolve completely.
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post #88 of 90 Old 02-21-2013, 09:43 AM
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Quote:
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Think of 0dBFS as a FULL VOLUME...

I had thoughts on what 0 dBFS means to me but I was looking for more clarity of the context it was being used in this case.

Just because there is a knob doesn't mean you should turn it.
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post #89 of 90 Old 02-21-2013, 10:18 AM
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Originally Posted by NicksHitachi View Post

A good house curve eats up headroom pretty quick...... Audyssey applies a pretty good bit of LF boost for me out of the box. Im using the MulteqXT variety.

Z,

it really sounds like to me, that your ready for a full measurement setup. Many of the questions your asking beg measurement to resolve completely.

That's in part why I was surprised by such low power consumption in my case. I use a low shelf filter plus whatever Audyssey/DEQ does.
With Audyssey disabled my curve is fairly flat to 20Hz at the LP. But I measure at relatively low SPL which may be my problem.

I will definitely be investigating more. My new subs are coming soon, I want to make sure the are set up properly.
I am using REW with calibrated Galaxy meter and Edirol USB SC . should be good enough for the task (as long as I know what I am doing which may not be the case)
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post #90 of 90 Old 02-21-2013, 10:44 AM
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Originally Posted by zheka View Post

whoaru99, thank you for making me look at this more closely.

No problem.

Just because there is a knob doesn't mean you should turn it.
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